ea Lh Begun in 1895 NUMBER 361 NOVEMBER 28, 2001 Paleoecological Studies of South Forida edited by i Bruce R. Wardlaw Published in cooperation with The United States Geological Survey ZUSGS science for a changing world Paleontological Research Institution 1259 Trumansburg Road Ithaca, New York, 14850 U.S.A. PALEONTOLOGICAL RESEARCH INSTITUTION Officers PRESTON sree areal ean ea aI ACTED ne a Male REA ee Tad CHRISTOPHER G. MAPLES FURST WAGEAR RESTO EIN oy ce ieieyet HRL eed Mise ay Bie ett MalISPOA undone TEA Oy Deh enh JOHN PoseTA, JR. SECONDAVIGE

' a wa in - yin - Gd AOS Ae Caen Couly Ah al ony : (\) om? 1.0 axe? Giagewh aoe? : = om = Cone! it Ut Ge wt We Reet come ‘2 oe . l@ 7 4 4 We CHAPTER INTRODUCTION TO PALEOECOLOGICAL STUDIES OF SOUTH FLORIDA AND THE IMPLICATIONS FOR LAND MANAGEMENT DECISIONS BRUCE R. WARDLAW U.S. Geological Survey, 926A National Center, Reston, Virginia 20192 ABSTRACT The Florida Everglades developed from the interplay of sea level and climate. The subtle balance of these two factors over the last two millennia is important to understanding restoration strategies. During the Medieval Warm Period and the Little Ice Age, the Everglades showed a general drying trend. The Medieval Warm Period trend was due to a significant decrease in annual precipitation while sea level was rising. The Little Ice Age trend was due to the combined effect of reduced precipitation and the slowing in the relative rate of sea level rise. This failure to keep base level with Everglades sediment and peat accumulation, yielded shorter hydroperiods and dryer conditions. Sea level has been steadily rising over the last century and should be considered in water flow modeling. Land use and water management practices over the last century have greatly partitioned the Everglades, compounding its ability to respond ecosystem-wide in predictable ways to climate and sea level change. Salinity in Florida Bay is affected by marine circulation, climate (rainfall) and runoff. Marine circulation was reduced in the early 20" century by intense railroad, highway, and bridge construction connecting the Keys. Rainfall and runoff appeared coupled early in the 1900’s and has slowly been decoupled throughout the last century, especially after 1970. A restoration goal should be to couple rainfall and runoff again. Salinity in central, western and southern (Atlantic transitional) zones is influenced by direct rainfall; salinity in the northern (northern transitional) and eastern zones is influenced to a large extent by runoff. These latter zones need to be monitored to ascertain that rainfall and runoff are indeed coupled to the degree that they have been in the past. Salinity can be predicted for specific sites in Florida Bay following known rainfall months. INTRODUCTION The South Florida ecosystem has undergone dynam- ic changes over the last century but most of these are known only by analogy. Can paleoecological studies fill this important information gap? Yes, detailed pa- leoecological studies provide the retrospective infor- mation to understand the course and cause of these changes. Can this information influence and be utilized by decision makers? Yes, this information enables a more coherent scientific foundation on which to base policies and decisions. This volume offers a wide variety of paleoecologi- cal studies in many different areas of South Florida. The area of study and the techniques utilized affect the conclusions which vary from local and qualitative to widespread and quantitative. The underlying data for interpretation are invaluable. Swart et al. (Chapter 2) show by the isotopic sig- nature of the water that salinity in central, western and southern (Atlantic transitional) zones of Florida Bay is influenced by direct rainfall; salinity in the northern (northern transitional) and eastern zones of Florida Bay is influenced to a large extent by runoff (Text-fig. 1). Holmes et al. (Chapter 3) discuss the utility of 7!°Pb in dating cores from the mud banks of Florida Bay. This technique provides age models for the last 150 years and is critical for unraveling the sequence of variability and change in Florida Bay. In the peats of the terrestrial ecosystem and the peats of the initial transgression in the bays, radiocarbon dates provide the age framework and are reliable up until near modern time where the margin of error ex- ceeds the age value. *!°Pb has provided reasonable age models in the uppermost part of the peats for the last century of deposition. Willard et al. (Chapter 4) utilize modern census data from the ridge and slough and southeastern Everglades National Park along with that data collected by Riegel (1965) to develop a robust modern analogue for inter- preting down-core terrestrial samples. Core samples are from the northern ridge and slough, Shark River Slough, and Taylor Slough. The core data indicate that the Everglades were generally wetter (experienced deeper water and longer hydroperiods) than today, but experienced three significant drying spells: one that correlates with the Medieval Warm Period (800—1400 AD); one that correlates with the Little Ice Age (1550— 1850 AD); and one that is the present century. The present dry spell shows a progressive deterioration with shallower water and shorter hydroperiods by 1930, significant localization of the marsh in the 1950’s and 1960’s, and expansion of cattail marshes at nutrient-enriched sites after 1960. ° BULLETIN 361 Only Precipitatiamsand sm CL, ATLANTIC OCEAN Text-figure 1.—Zones of Florida Bay defining eastern, northern (Northern Transitional), central, western, and southern (Atlantic Transitional) Florida Bay and isotopic signature of the waters (derived from Swart er al., this volume). Winkler et al. (Chapter 5) concentrate on several cores from the brackish marshes and wet prairies of eastern Everglades National Park where marls and cal- careous soils currently dominate. They provide a wealth of data from a variety of fossil groups. An in- teresting insight, based on the distribution of chitinous exoskeletons of cladoceran crustaceans from two cores shows a dramatic recent increase; it is commonly as- sociated with periphyton; and implies that periphyton may also be a recent phenomenom, corresponding to nutrient and trace element increases from land use changes during the last 50 years. This suggestion needs careful documentation of the modern distribu- tion and the distribution in many more cores before it can be substantiated. Winkler er al. (Chapter 5) envi- sion Everglades peat deposition initiating about 5,000 INTRODUCTION: WARDLAW 7 Lake Okeechobee Radiocarbon Ages of Initial Sedimentation in years before present Elevation of Bedrock Surface Showing Everglades Trough (Shaded) Contours in feet above mean sea level Text-figure 2——Basal ages of initial Everglades transgressive sed- imentation modified from data presented in Winkler et al. (this vol- ume) and elevation of bedrock surface modified from Brooks (1984) outlining Everglades trough (shaded, elevations generally 6 ft or less above mean sea level). ame] Pinelands x Wet Prairies > al Cypress Forests = Brackish Marshes Sa] Mangroves ‘| Developed Area = Rockland Pine Forests ey] Sloughs iii) Sawgrass Marshes years ago by a widespread climate change; however, based on their data, it is more easily explained as part of the Holocene transgression (see below). They cau- tion that dating at close intervals is critical to under- standing the ecosystem history, yet fall prey to lack of precision when their correlation of marls as contem- poraneous is not supported by their sparse age data. However, based on diatom abundances, they propose a wet period between 2,000 and 1,600 years B. P, which agrees with the wet period observed by Willard et al. (Chapter 4) based on pollen at the base of their sections (0 to 800 AD). O’Neal et al. (Chapter 6) utilize census data from Riegel (1965) which concentrated on the western por- tion of Everglades National Park. Numerical analysis (cluster and multivariate analysis) characterize spatial pollen zones of the western Everglades and examine the historical record in two cores from the mangrove swamps of the same region. They document the over- all late Holocene transgression and differentiate man- grove swamp communities as coastlines that first trans- gressed and then were stabilized. Zarikian et al. (Chapter 7) show that rainfall is the dominant driving force behind long-term variability in microfaunal assemblages from one core from Oyster Bay within the mangrove forests. This environment (interior mangrove forest) generally is most suscepti- bile to hurricane devastation and yet the core provides Developed areas Peat and muck soils - sawgrass peat Peat and muck soils - loose peat Sandy soils - light colored, agi poor natural drainage and low fertility es) Rockdale - rockland pine Wet rock land, marshes, swamp and made land = Marls and calcareous soils eal Marls - saline A Vegetation Type, B Soil Type Text-figure 3.— Vegetation types (A) of South Florida (modified from Willard et al., this volume) and soil types (B) of parts of South Florida (modified from Willard et al., 2001). 8 BULLETIN 361 Cattails 2000 ar (ec) lo) oO 1600 Little Ice Age 1400 1200 1000 800 Medieval Warm Period 600 400 Weedy Sawgrass Marsh ; qf z | | ; ae z Wet Prairie Site 6 —M Mixed | Florida B ay Text-figure 4.—Pollen wetland subenvironments indicated for eight peat cores from South Florida over the past 3 millennia. Locality shown in inset (modified from data in Willard et a/., this volume). little correlation to hurricane events, though the au- thors maintain they remain an important factor. Stable isotopes from ostracode and foram tests suggest a de- coupling of rainfall and freshwater flow during the 1970’s for this particular location. Huvane and Cooper (Chapter 8) show that diatoms are common to Florida Bay cores and useful in sea- grass, salinity, and productivity studies. Cronin et al. (chapter 9) utilizing ostracode-epiphyte distributions show that seagrass and macro-benthic al- gae fluctuate in abundance and coverage. They were sparse in the late 19" and early 20" centuries, dense in the 1950’s and 1960’s and declined in the 1970’s and 1980’s; but they are still more common than at the turn of the 20" century. Brewster-Wingard et al. (Chapter 10) show that the molluscan faunas that occur throughout the cores ba- sically reflect the same fauna that is present at those sites today. However, subtle fluctuations in patterns of dominance and diversity track the changes in local habitat, salinity, and water quality through time. Ishman (Chapter 11) recognizes four distinct fora- miniferal assemblages in Biscayne Bay: an open-bay seagrass, an open-bay substrate, a restricted and a high productivity assemblage. The restricted assemblage represents reduced salinity, restricted circulation, and point-source fresh water input. The high productivity assemblage represents high nutrient input and is very local in the northern part of the Bay. Dwyer and Cronin (Chapter 12) show that Mg/Ca ratios from adult ostracode shells reflect the salinity and provide a reasonable value function; they conclude that there is a strong climatic control on Florida Bay salinity. THE EVERGLADES Data presented in this volume suggest that the Ev- erglades are the result of a delicate balance of sea level rise and climate (precipitation). Comparison of the age INTRODUCTION: WARDLAW 9 Salinity (ppt) and Rainfall (cm) Text-figure 5.—Average annual rainfall for South Florida, in cm, compared to salinity derived from shell elemental chemistry of os- tracodes from the Russell Bank Core (for location see Fig. 6, mod- ified from Dwyer and Cronin, this volume). Notice the strong match of low rainfall years and high salinity up to 1967 and inconsistent matches following that year. of initial sedimentation of Everglade deposits to the elevation of bedrock (Text-fig. 2) shows a direct cor- relation of lower elevations and earlier deposition. Clearly, the Everglades represent a growing terrestrial marsh ecosystem with rising base level driven by sea level rise. This is exactly what O’ Neal et al. (Chapter 6) could discern from their work, documenting a trans- gressive sequence in the mangrove environments. Vegetation and soil type (Text-fig. 3) distributions agree well with each other and show a direct correla- tion to the trough shown by lower elevation (Text-fig. 2) with the area that comprises the ridge and slough vegetation of the Everglades today. Willard et al. (Chapter 4) indicate three general dry- ing phases in the history of the Everglades summa- rized in Text-figure 4. These correspond to the Medi- eval Warm Period (800-1400 AD), the Little Ice Age (1550-1850 AD), and the present (post-1930 AD). Much evidence suggests that the Medieval Warm Pe- riod represented a period of decreased rainfall in the subtropics (see Willard er al., Chapter 4); hence the reason for the drying of the Everglades. However, the explanation of the Little Ice Age is less clear. Fair- bridge (1984) presents a lot of anecdotal evidence for a decrease in the rate of sea level rise or even a slight EVERGLADES NATIONAL PARK Decadal Salinity Averages Florida Bay 4 ®@ Lignumvitae SALINITY (PPT) Text-figure 6.—Decadal salinity averages across Florida Bay. fall, during the Little Ice Age. It appears that a drop in base level along with a slight decrease in the pre- cipitation probably caused the drying conditions ob- served for the Little Ice Age period in the Everglades. This emphasizes the subtle interplay of base level and precipitation in maintaining deep water levels and long hydroperiods for the Everglades. Long term sea-level curves (Robbin, 1984; Toscano and Lundberg, 1998) are smoothed given the coarseness of the data com- pared to the fluctuating curve of Fairbridge (1984). All consistently show a decrease in the rate of sea-level rise approaching the present, which suggests a natural drying trend for the Everglades. However, the present shows a dramatic drying trend, starting around 1930 (Willard er al., Chapter 4), and fragmentation after 1960 that appear to be beyond the interplay of precip- itation and base level. SALINITY IN FLORIDA BAY Data presented in this volume and in an earlier sum- mary by Brewster-Wingard ef al. (1998) indicate that fossil and geochemical proxies yield fairly reliable sa- linity information from Florida Bay. The distribution 10 BULLETIN 361 Bob Allen 6A e High Amplitude Shifts Ee 2 2 [o) oO = = a oO a Russell Bank 19B o Pass Key 37 @ Taylor T24 « 0) 10 20 30 40 50 60 70 ~1900 ontoODmonTO EVERGLADES NATIONAL PARK Distribution of Benthic Salinity Indicators in Florida Bay Cores Text-figure 7.—Distribution of benthic faunal indicators of euhaline and near euhaline conditions (> 25 ppt) in four cores from Florida Bay (modified from Brewster-Wingard et al., 1998). of benthic faunal indicators (foraminifer, ostracodes, and mollusks) from four cores and the shell geochem- istry of the ostracode shells from three of these cores have been analyzed. We are continuing the shell geo- chemistry analysis of additional cores, looking at the results in different growth stages, and looking at the elemental chemistry and carbon and oxygen isotopes of mollusk shells in an effort to evaluate the seasonal variability in salinity over the last century. The salinity values derived from shell geochemistry are compared to the average annual rainfall for South Florida (Text-fig. 5). The salinity record is taken from 2 cm samples that average approximately 2 years/sam- ple based on the age model which yields a sedimen- tation rate of 1.28 cm/year (Russell Bank Core, see Holmes et al., Chapter 2). The average rainfall curve is a compilation of the available data from NOAA website (http://www.ncde.noaa.gov/onlineprod. drought/xmgr.html) for the three reporting districts that makeup South Florida (the SW, the SE coast, and the Bay and Keys), averaged to one composite and coy- ering the years 1895 to the present. Our core was taken in 1995. The rainfall pattern beginning the 19" century shows high frequency, low amplitude shifts that change to high frequency, high amplitude shifts in the late 1930s, and change again to moderate frequency, moderate amplitude shifts for the latter part of the 20" century. The derived salinity curve matches the rain- fall curve very well for the first and middle parts of the century, with high salinity peaks occurring during low rainfall years and low salinity peaks occurring in high rainfall years. This is quite remarkable, given the difference in sampling intervals. However, following 1967, a decoupling occurs, with only the lowest rain- fall years matching salinity highs and moderate and high rainfall years not corresponding consistently with moderate or low salinities. Coincidently, 1967 is the year that South Florida came under complete water control management. Recent isotopic data from Swart (Chapter 2) suggest that the salinity values in the east- ern part of Florida Bay are affected directly by surface waters as those waters have an isotopic composition that reflects strong mixing with Everglades water. Therefore, rainfall is coupled to decreases in salinity directly by increased surface water flow and that flow was disrupted in the late 1960's. Swart et al. (1996b) presented salinity data based on C and O isotopic studies of the growth bands in a rare large coral head in Florida Bay from Lignumvitae basin (inset, Text-fig. 6). The data were summarized as decadal salinity averages. I compare this to the sa- linity values derived from our combined fossil salinity INTRODUCTION: WARDLAW 11 ‘Best Fit' Age 140 120 100 Russell Bank Age Model € oO} o 80 ° * : 4 £ LY = 60 Sa = yy 6 _ 40 we LE a ee ge om AE - a 20 JP _AA 1985S O75 N 19655 1955 S45 935 Year Range in Age for a given 2 cm Sample Maximum, Median, and Minimum Age based on Sedimentation Rate Park Key Age Model 1925) SiS) 1905) e895 Text-figure 8.—Best Fit Age model for Russell Bank and Park Key. proxies (foraminifers, ostracodes, and mollusks). De- cadal averages are plotted at the midpoint of each de- cade (Text-fig. 6). The data for both Lignumvitae and Bob Allen Key extend back to before 1850. The Rus- sell Bank data extends back to 1870. Prior to 1910, the three localities show a consistent gradient from fresher to more saline values from north to south in the bay. However, following 1910, Lignumvitae shows less decadal fluctuation and slightly elevated average salinities (above mean sea average) indicating more restrictive conditions. Bob Allen and Russell Bank switch; that is, though the decadal fluctuations still track each other, Bob Allen in the center of the bay becomes consistently fresher relative to Russell Bank, disrupting the gradient noted prior to 1910. Large- scale construction connecting the Keys and filling in marine passages (building the Flagler Railroad to Key West) and initial canal construction in the Everglades occurred in the first two decades of the 20" century. These activities may have directly affected the subtle changes seen in the salinity patterns of the Bay. The salinity values derived from faunal (foraminifer, mollusk, and ostracode) proxies for our first four Flor- ida Bay cores are shown in Text-figure 7. These are plotted against depth in core with the age model high- lighted in bold. The values for the longer cores (Bob Allen and Russell Bank) show low amplitude shifts in salinity prior to 1910 and high amplitude shifts in sa- linity after about 1940, agreeing with the curve de- veloped from shell geochemistry for Russell Bank. These faunal derivations are too coarse to comment on the frequency of salinity shifts. The overall trend in- dicated by these benthic faunal indicators is that most of the bay seems to have experienced a slight increase in salinity values over the last century and specifically in last 30 years (post-1970). IMPLICATIONS FOR RESTORATION Comparison of the average annual rainfall of South Florida (Text-fig. 5) to the pollen assemblage data which is summarized in Text-figure 4 shows that broad-scale vegetational changes in the Everglades wetlands began by 1930, indicating shallower water depths and shorter hydroperiods, even though regional precipitation increased concomitantly. Further, more localized changes occurred after 1960. Thus, restora- tion goals of achieving pre-1960 hydrologic regimes are aimed at an already disrupted system; a more “‘nat- ural” restoration target would be the 19" century Ev- erglades, consisting of slough subenvironments which had been stable for the past few centuries. Recent land- use changes have resulted in localized rather than sys- tem-wide ecosystem responses, at least in part because of the fragmentation of the wetland. This artificially induced ecological heterogeneity makes prediction of future wetland responses to climatic changes problem- atic. Faunally and chemically derived salinity curves for Florida Bay show that salinity values are directly re- lated to rainfall and surface water flow for the eastern half of the bay. However, following 1967, there is a decoupling of salinity response to rainfall amount and surface water flow. More subtle trends show that the annual average salinity of the bay has increased slight- ly during the 20" century and that the general pattern of fresher to more saline water across the eastern bay has been disrupted after the turn of the century. These trends in the salinity values of the bay are related to the disruption of both fresh-water and marine-water delivery to the system that began shortly after the turn of the century and culminated in total water-control management in 1967. Recent water practices of re- leasing fresh water into Taylor Slough appear to have reestablished at least a normal gradient in salinity over the past 5 years, based on our modern monitoring data (post-coring). Long-term data provided by faunal, floral and bio- geochemical analysis provide essential information to establish restoration targets for the South Florida eco- system. These data clearly indicate that a more open water delivery system is necessary to provide eastern Florida Bay with more fresh water and the terrestrial Everglades with less restricted flow and deeper water during wet cycles, thus reestablishing more natural cy- cles of change. PREDICTING SALINITY IN FLORIDA BAY The chemical proxy data from Florida Bay cores allow us to develop predictive formulas for establish- ing an anticipated salinity for a given rainfall record that should help us test success in recoupling rainfall and surface water flow. It also allows us to “‘retune” the age model provided by Holmes et al. (Chapter 3). Biotic and chemical proxies for salinity in Florida Bay show that salinity values for the last century are strongly correlated with climate, specifically, rainfall (Brewster-Wingard and others, 1998; Cronin and oth- ers, 1998). Elemental chemistry of ostracode shells provides a methodology to discern salinity values of the past (Dwyer and Cronin, 1999). Adult tests of the ostracode Loxoconcha matagordensis are grown es- sentially instantaneously in the late Spring and early Summer. Salinity values derived from adult Loxocon- cha matagordensis, generally grown between May and July, each year serve as proxies for June salinities. Because Loxoconcha matagordensis growth shows a very tight normal distribution, population studies from one sample should provide us with data on salinity 2» BULLETIN 361 Table 1.—Best Fit Model data for year, salinity (in parts per thou- sand, ppt), and cumulative January—May rainfall (in cm). Russell Bank Park Key Year Salinity Rainfall Year Salinity Rainfall 1900 21 45.30 1895 31 33.46 1903 27 39.88 1897 30 30.80 1906 22. 42.71 1900 27 45.30 1912 20 41.50 1906 20 42.71 1913 19 35.54 1910 58 23.60 1915 21 42.59 1917 60 17.56 1916 30 26.93 1922 38 29.52 1917 34 17.56 1927 38 21.74 1919 21 43.67 1928 29 37.05 1922 30 29.52 1931 26 50.62 1923 20 35.61 1935 47 21.07 1927 37 21.74 1936 27 45.99 1928 27 37.05 1938 40 19.03 1929 42 25.05 1942 31 45.26 1931 20 50.62 1945 53 13.68 1932 28 41.44 1947 34 43.36 1933 40 29.49 1949 56 21.67 1934 28 45.75 1952 BS 28.06 1935 43 21.07 1955 51 18.84 1936 24 45.99 1957 38 51.61 1938 44 19.03 1958 33 64.36 1941 20 53.94 1959 27 41.65 1943 38 25.82 1962 60 20.67 1947 27 43.36 1966 35 42.40 1949 54 21.67 1971 49 16.33 1950 53 21.08 1973 36 27.60 1953 35 31.50 1978 25 41.01 1954 22 47.26 1981 51 20.05 1955 5y7/ 18.84 1982 34 52.45 1956 57 18.83 1983 32 67.63 1958 27 64.36 1985 45 28.03 1962 51 20.67 1987 33 38.32 1963 51 2el> 1991 28 48.61 1964 60 29.87 1993 26 50.50 1965 52 21.99 1967 43 19.43 1968 29 46.33 1969 35 43.01 1970 18 51.28 1974 31 20.40 1976 29 37.90 1977 36 36.60 1979 31 40.62 1981 45 20.05 1982 25 52.45 1984 25 45.80 1987 19 38.32 1988 29 32.83 1989 43 PYG) 1990, 42 31.73 1992 37 25°71 1994 35 42.59 changes occurring at the beginning of the rainy season (usually June). Russell Bank has a long record and relatively abundant Loxoconcha matagordensis. Park Key has a relatively short record but also has relatively INTRODUCTION: WARDLAW | 50 Salinity (ppt) i} 1 20-4 1900-1928 1974-1994 0 10 20 30 40 50 60 70 Russell Bank Salinity (ppt) 10 20 30 40 50 Cumulative Rainfall January-May) in cm Park Key Text-figure 9.—Regression trend lines for data points listed in Table 1. abundant Loxoconcha matagordensis. Biotic indicators were analyzed from every other 2 cm sample and el- emental chemistry of the ostracodes was performed from every sample. The calculated sedimentation rate of the Russell Bank core is 1.28 cm + 0.07 (Holmes et al., Chapter 3), so our sampling represents approx- imately every 1.5 to 2 years. The calculated sedimen- tation rate of the Park Key core is 0.78 cm + 0.5 (Holmes et al., Chapter 3), so our sampling represents approximately every 2.5 years. ASSUMPTIONS AND VALUES FOR THE MODEL January—May rainfall.——Monthly rainfall informa- tion is available from NOAA website (www.ncdc. Ww Table 2.—Linear equations and R® values for regression trend lines for all points, natural clusters, and model linear equation for site at present for ‘natural’ restoration. Russell Bank Park Key All Points y = —0.78x + 60.08 y = —0.57x + 57.86 R? = 0.5508 R? = 0.5278 1900-1922 y = —0.62x + 46.60 R? = 0.6541 1895-1936 y = —0.97x + 68.25 R? = 0.7027 1929-1943 y = —0.73x + 58.83 R? = 0.9683 1895-1955 y = —0.86x + 65.24 R? = 0.6882 1946-1970 y = —0.85x + 69.94 R? = 0.7414 1938-1955 y = —0.66x + 60.75 R? = 0.6466 1974-1994 y = —0.50x + 49.98 R? = 0.4253 1957-1993 y = —0.45x + 55.27 R? = 0.4907 Model y = —0.79x + 64.38 y = —0.92x + 66.74 noaa.gov/onlineprod.drought.xmgr.html) dating back to 1895. The eastern portion of Florida Bay is influ- enced by rainfall and surface run-off. To compare rain- fall to salinity values on a monthly basis, averages of the three southern districts (southwest (Everglades), southeast coast, and Bay and Keys) were taken be- cause rainfall to all three may influence salinity in Florida Bay. Because the focus is June salinity, rainfall from the five preceding months was examined to es- tablish a relationship. During El Nino years, high win- ter rainfall is usually recorded in January; therefore, January rainfall is included in the data set to indicate the occurrence of these events. This methodology ap- pears to combine the affects of both direct rainfall and surface water runoff. The salinities derived from the cores do not match well with direct rainfall for the months of May, June, and July, and imply that surface water flow has a strong influence on the salinity at these sites. June salinities.—Meg/Ca derived salinities from the ostracode Loxoconcha matagordensis from Russell Bank Core and Park Key Core as discussed above and derived from the analyses listed in Dwyer and Cronin (this volume). Wardlaw and Brewster-Wingard (2000) have shown significant correlation between the Janu- ary—May rainfall and derived salinities for the eastern portion of the Bay. Here, I have taken the age model of Holmes er al. (Chapter 3, this volume) and fine tuned it (Text-fig. 8) matching better rainfall to salinity values within or close to within the allowable ages given the age model and sampling interval (see Table 1 for all data). 14 BULLETIN 361 Results.—The relationship between January—May average rainfall for South Florida and June “‘‘ostra- code”’ salinities can be expressed as a series of simple linear equations of negative correlation (Text-fig. 9) and provides us with a predictive value. The relation- ships for all derived values and relationships that clus- ter in age groups are shown in Table 2. The lessening of slope appears to indicate disruption or decoupling of the natural system. At Park Key, this appears as early as the 1930’s. At Russell Bank, it appears in the seventies. The correlation value (R?) also decreases greatly at major disruption. Though Park Key appears disrupted early in the century, its impact appears minor in that the trend line for all data 1895-1955 is still very close to that before disruption. A model for prediction of salinity can be derived be- tween these two trend lines (Text-fig. 9). Russell Bank shows a progressive change in slight increase in slope and rising in overall salinity through most of the century. Rainfall patterns are changing from high amplitude, high frequency fluctuations to more moderate amplitudes and frequencies and a mod- el for prediction can be derived between trends of 1929-1943 and 1946-1970, suggesting a slight less- ening of overall salinity for this site. The slope of the trend line decreases as a function of distance from surface water source and with a few additional cores could be mathematically modeled. In addition, the interplay of rainfall versus surface water flow on salinity can be addressed by looking at the biology of the ostracodes more closely and devel- oping chemical proxies from longer-lived taxa such as molluscs that can yield multi-year records of nearly continuous carbonate secretion. REFERENCES CITED Alvarez Zarikian, C.A., Swart, P.K., Hood, T., Blackwelder, P.L., Nelsen, T.A., Featherstone, C., Wanless, H.R., Trefrey, J., and Kang, W.-J. 2001. Chapter 7. 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Historical trends in epiphytal ostracodes from Florida Bay: implications for seagrass and macro-benthic algal variability. Bulletins of American Paleontology, no. 361, pp. 159-197. Dwyer, G.S., and Cronin, T.M. 2001. Chapter 12. Ostracode shell chemistry as a paleosalinity proxy in Florida Bay. Bulletins of American Paleontolo- gy, no. 361, pp. 249-276. Fairbridge, R.W. 1984. The Holocene sea level record in South Florida. in Glea- son, P.J., ed., Environments of South Florida, Present and Past II. Coral Gables, FL, Miami Geological Society, pp. 427-436. Holmes, C.W., Robbins, J., Halley, R., Bothner, M., Ten Brink, M., and Marot, M. 2001. Chapter 3. Sediment dynamics of Florida Bay mud banks on a decadal time scale. Bulletins of American Paleon- tology, no. 361, pp. 31—40. Huvane, J.K., and Cooper, S.R. 2001. Chapter 8. Diatoms as indicators of environmental change in sediment cores from northeastern Florida Bay. Bulle- tins of American Paleontology, no. 361, pp. 145-158. Ishman, S.E. 2001. Chapter 11. Ecological controls on benthic foraminifer distributions in Biscayne Bay, Florida. Bulletins of Amer- ican Paleontology, no. 361, pp. 233-247. O’Neal, M.A., Tedesco, L.P., Souch, C., and Pachut, J.F. 2001. Chapter 6. A pollen zonation of southwestern Florida us- ing multivariate statistical methods and its application to two vertical sedimentary sequences. Bulletins of Ameri- can Paleontology, no. 361, pp. 101-132. Riegel, W.L. 1965. Palynology of environments of peat formation in south- western Florida: Unpublished PhD thesis, The Pennsyl- vania State University, 189 pp. Robbin, D.M. 1984. A new Holocene see level curve for the Upper Keys and Florida reef tract. in Gleason, PJ., ed., Environments of South Florida, Present and Past II. Coral Gables, FL, Mi- ami Geological Society, pp. 437—458. Swart, P.K., Healy, G.F., Dodge, R.E., Kramer, P., Hudson, J.H., Halley, R.B., and Robblee, M.B. 1996. The stable oxygen and carbon isotopic record from a coral growing in Florida Bay, A 160 year record of climatic and anthropogenic influence. Palaeogeography, Palaeocli- matology, Palaeoecology, v. 123, p. 219-237. Swart, P.K., Price, R.M., Greer, L. 2001. Chapter 2. The relationship between stable isotopic vari- ations (O, H and C) and salinity in waters and corals from environments in South Florida: implications for reading the paleoenvironmental record. Bulletins of American Pa- leontology, no. 361, pp. 17-29. Toscano, M.A., and Lundberg, J. 1998. Early Holocene sea-level record from submerged fossil reefs on the southeast Florida margin. Geology, vol. 26, no. 3, pp. 255-258. Wardlaw, B.R., and Brewster-Wingard, G.L. 2000. Predicting salinity in Florida Bay. Greater Everglades INTRODUCTION: Ecosystem Restoration Science Conference: Defining Success, South Florida Ecosystem Restoration Task Force and Working Group, Naples, Florida, 12/1 1—15/2000, pp. 177-179. Willard, D.A., Holmes, C.W., and Weimer, L.M. 2001. Chapter 4. The Florida Everglades ecosystem: Climatic and anthropogenic impacts over the last two millennia. Bulletins of American Paleontology, no. 361, pp. 41-55. W ARDLAW 15 Willard, D.A., Weimer, L.M., and Riegel, W.L. 2001. Pollen assemblages as paleoenvironmental proxies in the Florida Everglades. Review of Palaeobotany and Paly- nology, vol. 113, pp. 213-235. Winkler, M.G., Sanford, P.R., and Kaplan, S.W. 2001. Chapter 5. Hydrology, vegetation, and climate change in the southern Everglades during the Holocene. Bulletins of American Paleontology, no. 361, pp. 57-99. CHAPTER 2 THE RELATIONSHIP BETWEEN STABLE ISOTOPIC VARIATIONS (O, H, and C) AND SALINITY IN WATERS AND CORALS FROM ENVIRONMENTS IN SOUTH FLORIDA: IMPLICATIONS FOR READING THE PALEOENVIRONMENTAL RECORD PETER K. SWART, RENE M. PRICE, AND LISA GREER Stable Isotope Laboratory Rosensteil School of Marine and Atmospheric Science University of Miami 4600 Rickenbacker Causeway Miami, FL 33149 ABSTRACT The oxygen isotopic composition of calcareous material secreted by organisms is often used for the reconstruction of salinity values in past environments. Implicit in this reconstruction is the assumption of a constant relationship between salinity and the 5'8O value of water. In this paper, we demonstrate through the analysis of water samples collected from several estuaries situated adjacent to the Florida mainland that varying relationships exist between these two parameters depending upon the extent of evaporation experienced by the freshwater which influences the salinity. We further show that these relationships are translated into the 6'°C and 6'8O values of corals growing in these environments. Water samples collected from Florida Bay, Whitewater Bay, and the Ten Thousand Island area between October 1993 and December 1998 show a range of correlations between the 5'8O of the water and salinity. These varying correlations arise because while water from the Everglades possesses a low salinity it has a relatively positive 6'°O value. In contrast, precipitation has a more negative 65'*O value. Consequently, areas in which the salinity is significantly influenced by freshwater derived from the Everglades tend to have different 6!*O to salinity relation- ships compared to regions where salinity variations are caused solely by inputs of precipitation. These variations must be recognized if one is to use proxy indicators of salinity such as the 6!*O value of skeletal carbonates to accurately reconstruct past salinity records. The 6'°C of estuarine waters is related to both the input of isotopically depleted runoff from the Everglades and the local remineralization of organic material. Areas far removed from Everglades runoff, where variations in salinity resulted from input of precipitation, show little relationships between salinity and 5'°C because 6'°C variations arise from the local remineralization of organic material. In contrast, areas closer to the Everglades show stronger relationships between salinity and 6'°C. These relationships are manifested in the isotopic composition of the coral skeleton as an absence of correlation between 6'C and 6!*O in more marine areas compared to areas more directly influenced by runoff. INTRODUCTION The 6'°C and 6!8O values of calcareous organisms (ostracods, foraminifera, molluscs, and corals) have been used in the South Florida environment to ascer- tain changes in past environmental conditions, in par- ticular salinity (Swart et al., 1996; Swart et al., 1999; Halley and Roulier, 1999; Nelsen et al., 2000). The results of these studies indicate a change in salinity patterns commencing in Florida Bay as early as 1900. A concurrent shift in the 6'°C in both corals and mol- luscs suggest that a reduction in the hydrodynamic cir- culation of Florida Bay may be responsible for the observed changes in salinity. Construction of the Overseas Railway from Miami to Key West from 1906-1914, followed by water management practices which diverted the natural flow of water from the Ev- erglades into Florida Bay have been suggested as pos- sible causes for the reduced circulation within Florida Bay (Smith er al., 1989; Swart et al., 1996, 1999). Anthropogenic changes in South Florida occurred synchronously with climatic variability. Regional droughts have been recorded in every decade from 1950 to 1990 resulting in salinity exceeding 50 in the central portions of Florida Bay (Fourqurean and Rob- blee, 1999; Fourqurean er al. 1992). In contrast, the 1997 El Nino, termed the “El Nino of the Century” produced above average rainfall during the winter dry season in South Florida. Decoupling these natural cli- matic conditions from anthropogenic conditions is im- portant in deciphering the paleoenvironmental record. This paper examines the associations between salin- ity, precipitation, and the 6'°O, 5D, and 6'°C of surface waters from ‘fresh’, estuarine, and marine environ- ments of South Florida and relates these data to the interpretation of the 5'°C and 6'%O record of two corals growing in Florida Bay. In order to study these rela- tionships, we have conducted a temporal and spatial investigation of the 6!°O, 6D, and 6'°C composition of 18 BULLETIN 361 waters from the Everglades, Florida Bay, Whitewater Bay, and the Ten Thousand Islands areas. These data were then correlated with salinity measurements made on the same samples (Boyer ef al., 1999). ACKNOWLEDGMENTS The authors would like to thank Dave Rudnick for having the insight to support this project, and the SFWMD for providing funding. Help with sample col- lection was provided by Mike Lutz. Amel Saied and Vivian Gonzalez are acknowledged for assistance with analyses. Collection of the water samples would not have been possible without the assistance of Florida International University/Southeastern Environmental Research Program (FIU/SERP). In this regard Ron Jones and Joe Boyer are especially acknowledged. George Shardt of Everglades National Park is ac- knowledged for collection of the Everglades samples. BACKGROUND HYDROLOGICAL SYSTEM IN SOUTH FLORIDA South Florida experiences a subtropical climate with a hot, wet season during the summer (mid-May—Oc- tober), and a mild, dry season during the winter (No- vember—mid-May). Annual precipitation is approxi- mately 130 to 150 cm across the region, with approx- imately 70% received during the summer wet season (Leach et al., 1972). The seasonality of precipitation and evaporation causes a seasonal fluctuation in sur- face water levels in South Florida. Water levels rise during the summer rainy season, with highest levels commonly observed in September and October. Dur- ing the winter dry season, water levels decline slowly. Surface water can be absent from many areas of the Everglades at the end of the dry season (April and May) as evapotranspiration exceeds rainfall (Kushlan, 1990). The Everglades depression extends southward from Lake Okeechobee to Florida Bay and is bounded to the east by Pleistocene limestones and quartz sands of the Atlantic Coastal Ridge and to the west by exposed Pliocene limestones of the Big Cypress Ridge. Holo- cene freshwater peats and marls partially fill the Ev- erglades trough, decreasing in thickness southward from 4 m at the southern end of Lake Okeechobee to 0.7 m along the coastline of Florida Bay (Kushlan, 1990). Under natural, pre-development conditions, most surface water flowed southward in the Ever- glades from Lake Okeechobee to the Gulf of Mexico via the Shark River Slough (Fennema ef al., 1994). A smaller drainage area, Taylor Slough, discharged lo- cally derived freshwater into Florida Bay. Beginning in the late 1800s and throughout the 1900s, a complex network of canals, levees, pump stations, and im- poundment areas were constructed throughout South Florida in an effort to manage water levels and flow throughout the region. Because of the resultant im- poundment of water in what are known as conserva- tion areas, evaporation is high, with estimates of rain- fall lost to evapotranspiration being as high as 70% to 95% (Leach et al., 1972). This decreased surface water flow from Lake Okeechobee, through the Everglades to the marine systems of the Gulf of Mexico and Flor- ida Bay, and increased drainage eastward toward Bis- cayne Bay (Fennema ef al., 1994). Marine environments that bound the southern pen- insula of Florida include the Gulf of Mexico to the west, Biscayne Bay to the east, and Florida Bay to the south. The west coast from Cape Romano in the north to Cape Sable in the south, is characterized by man- grove swamps, tidal channels and small bays. The northern section contains numerous mangrove islands separated by tidal channels with strong currents and is referred to as the Ten Thousand Islands (TTI) area. South of the TTI, tidal currents are more sluggish and freshwater runoff from the Big Cypress Swamp and the Everglades is transported to the Gulf of Mexico by numerous streams (Davis, 1997). Florida Bay is a large (2,000 km7?) triangular shaped estuary lying between the Southern Peninsula of Flor- ida and the Florida Keys. Florida Bay is relatively shallow and underlain by a complex system of Holo- cene carbonate mud-banks that subdivide Florida Bay into smaller basins. Water in Florida Bay is a mixture of precipitation, freshwater runoff from the Ever- glades, and seawater from the Gulf of Mexico and the Florida Straits. These sources combined with evapo- ration results in salinity variations from 4 to 50 (Nuttle et al., 2000). STABLE ISOTOPES The major influence on variations in the ratio of '*O to '°O and D to H in the water cycle occurs during the processes of evaporation and precipitation (Craig and Gordan, 1965). During evaporation, the concentrations of 'SO and D are reduced in the water vapor while these same species are enriched in the condensate. As a consequence, restricted bodies of water become en- riched in the heavier isotopes during evaporation while precipitation is typically enriched in '°O and H. Pre- cipitation throughout the world has been measured by the International Atomic Energy Authority (IAEA) and this data set shows that precipitation values become increasingly depleted towards the north and south poles (Rozanski et al., 1993). In South Florida the IAEA data estimates that rainfall should have a 65'8O value between —2 and —4%c. The behavior of the iso- topic composition of water during evaporation and STABLE ISOTOPIC VARIATION: SWART ET AL. 19 Cape Romano < “BG ® » a Outer Florida Bay ° Bs A nee Miami ox “ Biscayne Bay x ° i ° ouned ‘ Precipitation “ Precipitation “ _@ / it cae) NX Manates Bay Coral * ” . y Cora F, ; ° e De e Inner Florida Bay ONS Eastern-middle Florida Bay Western-middle Florida Bay e\Lignumvitae Basin Coral Text-figure 1_—Location map of water sampling stations within each geographic region. precipitation can be modeled using the Rayleigh Dis- tillation Equation. However, the maximum amount of enrichment in the heavier isotope that can be experi- enced by an evaporating water body is limited by sub- sequent exchange between the atmospheric moisture and the water body. The resulting isotopic composition that can be attained during evaporation is a function of the relative humidity, temperature of evaporation, and the isotopic composition of the atmosphere. The principals which govern the isotopic composition of such water bodies have been well studied and for fur- ther discussion the reader is referred to Gat (1981) and Gonfiantini (1986). For an environment such as South Florida where the mean relative humidity is 75%, the maximum 6'*O and 6D that can be attained by the water body undergoing evaporation are approximately +4%o and +42%o, respectively. Although the 6D ys. 6'8O of most precipitation throughout the world falls along a line known as the meteoric water line (MWL) (Craig and Gordan, 1965), data from evaporating wa- ter basins, when plotted on a similar diagram, fall on lines which deviate from the MWL depending upon the relative humidity. For example, environments with high relative humidity fall close to the MWL with a slope of 8, while waters evaporated into an environ- ment with a lower relative humidity will plot on a line with a slope significantly less than 8 (Gonfiantini, 1986). The dissolved inorganic carbon (DIC) pool is com- posed of CO,, HCO, , and CO,’ . In waters of pH between 7 and 9, the DIC is dominated by HCO, -. Although there is a large fractionation factor between CO, and HCO, (e = 8%c), the measured isotopic composition of the DIC reflects that of the HCO, fraction. Hence when CO, is added to water the iso- topic composition of the HCO, will be approximately 8%c heavier than that of the CO,. The 65°C of the DIC is governed by the input of respiratory carbon delivered to the system through the respiration of organic material and the consumption of CO, through the process of photosynthesis. As organic material contains less '*C than DIC which is in equi- librium with the atmosphere, addition of oxidized ma- terial will cause the 6'°C of the DIC to become en- riched in the lighter isotope of C ('?C). Terrestrial or- ganic materials tend to have more negative 6'°C values than marine material, and therefore waters derived from terrestrial sources associated with the oxidation of organic material often have more negative isotopic signatures than waters derived from marine sources. In a relatively closed system, the utilization of CO, in the process of photosynthesis can cause the residual pool of carbon in an environment to become enriched in 5C. Hence algal blooms for example could lead to more positive DIC 6'°C values. METHODS WATER SAMPLE COLLECTION Surface water samples were collected monthly since October 1993 in Florida Bay (Text-fig. 1). In October 20 BULLETIN 361 1996 and February 1997, additional stations were add- ed first in Whitewater Bay and subsequently in the Ten Thousand Islands area. Sampling for 6'8O at nine sites in the Everglades was initiated in August 1996. All water samples were collected in the field, filtered through a 0.45 jm filter to remove carbonate and other particles, and treated with a small amount of HgCl, to suppress biological activity. In the laboratory, the sam- ples were transferred to serum bottles and capped to exclude as much of the air space in the bottle as pos- sible. Repeated analyses of samples stored in this man- ner have not detected appreciable change in the iso- topic composition over periods of up to five years. Salinity was measured at each surface water sam- pling location (except for the Everglades locations) by Florida International University/Southeastern Environ- mental Research Program (FIU/SERP). A summary of these data has been published by Boyer et al. (1999). Automated water salinity monitors were deployed at three locations in Florida Bay: Lignumvitae Basin, East Key and Manatee Bay. Hourly salinity data were obtained using a Hydrolab Datasonde 3 between 1995 and 1998 in Lingnumvitae Basin. Similar data from East Key and Manatee Bay were collected over shorter time periods. Each instrument was serviced at 6 to 8 week intervals. Servicing consisted of cleaning organ- isms which encrusted the housing and sensors, replac- ing batteries, and calibrating the instrument for salin- ity. Drift in the instrument within a given sampling period was corrected by measuring the salinity and temperature with the instrument at the beginning and end of each deployment period and assuming a linear instrument drift during the deployment period. Precipitation samples were collected between Au- gust 1997 and December 1998 from two locations on the South Florida mainland. At the Redlands site, lo- cated southwest of Miami, precipitation was collected in a bottle equipped with funnel and tube. On a daily basis, the contents of the bottle were transferred to another bottle that was kept indoors and capped to form a bi-weekly to monthly composited sample. Dai- ly amounts of precipitation were recorded with a stan- dard wedge gage. Precipitation was also collected be- hind the Iori Building within Everglades National Park from December 1997 through December 1998, using an Aerochemetrics Wet/Dry collector. This collector consisted of two buckets, one to collect dry deposition and the other to collect wet deposition. The instrument was equipped with a heated sensor that when wet ac- tivated a mechanical arm that moved a cover from the wet collection bucket to the dry collection bucket, thereby exposing the wet collection bucket to rainfall. The heated sensor allowed for evaporation of rainfall that collected on it, and once dry, the mechanical arm was moved again to cover the wet collection bucket to prevent evaporation of the rainfall sample. Amount of precipitation was measured directly from the wet collection bucket using a ruler. CARBON ISOTOPIC COMPOSITION OF DISSOLVED INORGANIC CARBON (DIC) The 5'°C of waters was measured using two meth- ods. Method 1: The 6'°C of the DIC for samples col- lected early in the project were determined by acidi- fication under vacuum. Prior to analysis a sample (5 cc) was withdrawn from the serum bottle through a septum. The displaced volume of water was replaced by nitrogen gas. To acidify the sample it was injected into a sealed vessel through a septum which contained 0.5 cc of H,PO,. The sample and acid were then re- moved from the vacuum line and thoroughly shaken. The vessel was then reattached to the vacuum line and after evacuation the CO, produced was allowed to ex- pand through a water trap and then frozen with liquid nitrogen into a vacuum vessel. The vessel was subse- quently attached to a stable isotope mass spectrometer (Finnigan-MAT 251) and the ratios of C/'*C and !8O/ '©Q determined in a similar manner to the CO, pro- duced from the acidification of carbonate. Standards were made by dissolving NaHCO, of known 8C in 18.3 Mohm water to make a 4 mM solution. Stan- dardization is relative to PDB and data are reported in conventional 6 units. Reproducibility was determined by replicate analysis of the same sample and has been measured at + 0.1%0. Method 2: The 5%C of the DIC for samples col- lected during the latter stages of the project was de- termined using a continuous flow mass spectrometer. In this technique a vial with a septum containing 0.5 cc of ortho-phosphoric acid was evacuated. Two-cc of the sample was injected into the vial and thoroughly shaken. The sample was then placed along with other samples and standards in an autosampler (Gilssen) at- tached to a continuous flow isotope ratio mass spec- trometer (Europa 20—20). Each sample in turn was purged by helium and the water removed using mag- nesium perchlorate. The CO, produced by the reaction of the acid with the dissolved inorganic carbon (DIC) was passed through a packed GC column (75°C) and then analyzed using the mass spectrometer. In this method up to 200 samples can be processed in one batch. The precision of this method is approximately the same as in the acidification under vacuum method (+ 0.1%). STABLE ISOTOPIC VARIATION: SWART ET AL. 21 OXYGEN ISOTOPIC COMPOSITION OF WATERS The 5!8O of water was determined using the Epstein and Mayeda (1953) method of equilibration. Two ad- aptations of this method were used. Method 1: In this technique, | cm? of sample was placed in a vacuum vessel and all air removed through a process of freezing, pumping and thawing. After all air was removed, each flask was flooded in turn by | atm of CO, and the flask sealed. The water and the carbon dioxide were then allowed to equilibrate at 40°C overnight. In this process the oxygen in the water isotopically exchanged with the CO,. The CO, then attained an isotopic composition representative of the water, although offset through a fractionation factor. In each run 14 samples and 2 standards were equilibrated with CO,. Standards are related to V-SMOW through simultaneous equilibration with samples of V-SMOW distributed by the National Bureau of Standards (NBS). Reproducibility was determined by replicate analysis of the same sample and has been measured at + 0.1%. Method 2: \n this method the entire process includ- ing the flushing of the samples with CO,, equilibration, and extraction was handled automatically. The process was controlled by a computer interfaced to a mass spectrometer (Europa GEO) and an equilibration unit (Europa WES). In each experiment, 0.5 cc of sample was placed in a small serum vial with a septum top. These samples were flushed with CO, at atmospheric pressure and allowed to equilibrate for 12 hours at 35°C. The CO, was then extracted through a cryogenic water trap and the isotopic composition determined us- ing a mass spectrometer. A series of 59 specimens (in- cluding samples and standards) was analyzed in a 12 hour period. The reproducibility was approximately 0.08%c. HYDROGEN ISOTOPIC COMPOSITION OF WATERS The 5D of the water was determined using two methods. Initial samples were analyzed using the first method described for each of the elements. Later sam- ples, 1995 to the present, were analyzed using the sec- ond method. In both methods, data are reported rela- tive to V-SMOW. Method 1: The first method utilized the reduction of H,O to H, gas using uranium at 800°C (Friedman, 1953). The hydrogen gas was then analyzed using a stable isotope mass spectrometer (Finnigan MAT 251). Method 2: The second method used an equilibration technique between H, gas and H,O in the presence of a platinum catalyst (Hokko beads) (Coplen er al., 1991). This method was used in conjunction with the second method of determining the 6'°O of water using the GEO and WES. In this method the same samples which were used for the determination of the 6!°O were flushed with H,. The equilibration between H, and H,O occurred in a period of 30 minutes, allowing for analysis of the first equilibrated samples immedi- ately following flushing of the last sample H,. Preci- sion of this method determined by replicate analyses of the standards within each run is approximately 1.5%o. CORALS A specimen of Solenastrea bournoni was cored in Lignumvitae Basin of Florida Bay in 1986 and 1993. Isotopic analyses from this specimen were reported by Swart et al. (1996, 1999). In 1996, a specimen of So- lenastrea hyades was collected from Barnes Sound, near the mouth of Manatee Bay in northeast Florida Bay. Coral cores were sliced into sections parallel to the axis of coral growth. Core sections were then subjected to X-radiography to facilitate the construction of an- nual coral chronologies. Skeletal coral carbonate was sampled for 6'°C and 6'8O using methods described previously (Swart ef al., 1999). A powdered calcium carbonate was collected in transects from coral slabs using a computer-controlled drilling apparatus. All car- bonate samples were processed on a Finnigan MAT 251 Mass spectrometer connected to an automated ex- traction devise at the University of Miami. Data are presented in standard delta notation relative to PDB. RESULTS IsoTOPIC COMPOSITION OF WATERS The 6'8O of precipitation reported in this study in the South Florida area is highly variable. Despite this variability, the data fall near the MWL and have vol- ume weighted mean values for 6'°O and 6D of —2.9%c and —9.9%c, respectively (Table 1). The 6!*O data agree well with precipitation data collected between 1983 and 1988 (Swart ef al., 1989) that have mean 5'8O and 6D values of —2.7%c and —11.4%c, respec- tively. Actual 6'8O values of the precipitation ranged from values as negative as —6%c during the wet season to values close to 0%c during the drier portions of the year. Water from the Everglades is significantly enriched in 'SO and D with respect to precipitation (Table 1). Mean 56!8O for the Everglades samples is +0.55%c, compared to —2.9%c for precipitation. The highest val- ues occur during the end of the dry season (March— May) with isotopically more negative values in the late wet season (Text-fig. 2). The 6!°O and 6D data fall on a line with a slope of 5.8 (R* = 0.75), less than the slope of 8 for the MWL (Text-fig. 3). Although 6°C 22 BULLETIN 361 Table |.—Statistical summary of stable isotope and salinity data for surface waters by area and precipitation in South Florida. Number of Mean S.D. (a) Mean S.D. Mean S.D. Mean S.D. (a) Area samples ur) oe) 6D beC 6C Salinity Salinity Everglades 221 0.55 1.59 6.75 10.83 =e). Ox (c) (c) Florida Bay (total) 1318 1.62 1.00 ililesis) 6.66 ENT) 2.32 27.9 9.6 Inner 427 1.76 1.06 11.83 7.30 3-59 2.16 21.6 9.2 Eastern Middle 240 1.80 0.96 11.64 7.39 2,95 2.45 31.5 6.8 Western Middle 194 1.55 0.67 10.99 5.63 =) 7/7) 2.35 3319) 3.6 Outer 15] 1.41 0.60 9.50 4.99 2,23) 2.39 33.8 2.9 Whitewater Bay 247 1.58 1.19 10.07 8.07 133 1.85 13.5 10.1 Ten Thousand Islands 259 1.06 1.31 TEMP 7.89 =o) 2.34 21.6 11.6 Precipitation (b) 23 = 2.9 1.48 = 9195) 11 (c) (c) (c) (c) (a) Standard deviation. (b) Isotopic means for precipitation are weighted by the amount of precipitation. (c) Not measured. * Meyers (1990). of Everglades waters were not measured in this study, they were reported in Meyers (1990) and included in Table | for comparative purposes. In general, the iso- topic composition of DIC in Everglades waters were negative with a mean 6'°C of —6.9%c (Meyers 1990). The 6'8O of the water in all of the Florida Bay sam- ples ranges from —2.9 to +5.7%c with a mean of +1.62 (Table 1). The 5'%C for all of the Florida Bay samples (—2.87%c) is higher than that reported for the Everglades (—6%c; Table 1). A time series of the mean d!°C values for all stations in South Florida indicate a minimum in 1996 (Text-fig. 4). The mean 46'°O for the Whitewater Bay and Ten Thousand Islands areas are positive and +1.58%ec and +1.06%c, respectively (Table 1). In contrast, the mean 56°C for both Whitewater Bay and the Ten Thousand Islands area is significantly negative with values of —7.33%e and —5.76%oc, respectively (Table 1). These values are similar to those reported for the Everglades (Table 1) by Meyers (1990). COMPARISON OF OXYGEN AND CARBON ISOTOPIC COMPOSITION WITH SALINITY In order to examine the variation in the relationships between 6!°O, 61°C, and salinity further, we have sep- arated Florida Bay into four regions: Inner Florida Bay, Eastern-middle, Western-middle, and Outer Flor- ida Bay (Text-fig. 1). Salinity within these regions in- creases from east to west across Florida Bay (Table 1), typical of an estuary. The Inner Florida Bay region has the lowest mean salinity of 21.6, while the West- ern-Middle and Outer Florida Bay regions have a sim- ilar mean salinities of 31—33. In general, the mean 6'°O decreases from east to west across Florida Bay from +1.8 to +1.4%c (Table 1). The relationships between 6!°O and 6%C with salin- ity of South Florida estuarine waters are investigated by using 5!8O vs salinity and 6'3C vs salinity plots and then fitting a linear regression through the data (Table 2). When the 6!°O for each site in Florida Bay is avy- eraged on a monthly basis and compared to the cor- responding mean monthly salinity for each station, there is a positive linear correlation (R* = +0.36; p < 0.01) (Text-fig. 5). There is a positive linear relation- ship between 6!°O and salinity for each of the four regions of Florida Bay (Table 2; Text-fig. 6). Although the linear regression can explain only 30 percent or less of the variation between 5'8O and salinity in the Florida Bay regions (Table 2), each of the linear re- gressions are significant at p < 0.01. The linear rela- tionship between 6!*O and salinity was strongest for the two middle regions of Florida Bay (R* = 0.3), and weakest for the Outer region of Florida Bay (R? = 0.09). There is a variation in the intercepts of the linear regressions for each of the regions in Florida Bay. The linear regressions for the Inner and Eastern-middle ar- eas of Florida Bay predict a 6!°O at zero salinity of +0.33%c and —0.83%c, respectively. The predicted in- tercept of the linear relationship at zero salinity for the Western-middle and Outer areas of Florida Bay are 6.00 38'°0 ( Too) -6.00 Apr-95 Oct-95 May-96 Dec-96 Jun-97 Jan-98 Shark S aylor Text-figure 2.—Time series of mean 6'SO for Everglades. Error bars represent + | standard deviation. STABLE ISOTOPIC VARIATION: SWART ET AL. 23; 6D o -6 -4 -2 0 2 4 6 d°O1 Text-figure 3—Oxygen and hydrogen isotopic composition of Everglades water. Black circle represents volume weighted average isotopic composition of rainfall collected in this study. Open triangle represents isotopic composition of rainfall reported by Swart er al., 1989. significantly more negative than zero at —2.39%c and —1.07%c, respectively. A positive linear relationship exists between 6!*O and salinity for the Whitewater Bay and Ten Thousand Islands areas (Table 2). The linear correlation coeffi- cient (R*) for the Whitewater Bay and Ten Thousand Islands is 0.34 and 0.28, respectively (p < 0.01). The predicted intercept of the linear relationship at zero salinity is close to zero for both the Whitewater Bay (+0.35%c) and Ten Thousand Islands areas (—0.2%c, Table 2). There is no strong linear correlation between 61°C and salinity throughout all of Florida Bay (Text-fig. 7). Similarly there is no strong linear correlation between 56°C and salinity within the four regions of Florida Bay (Table 2; Text-fig. 8), except for the Inner Florida Bay area. The Inner Florida Bay area, Whitewater Bay area and the Ten Thousand Islands areas have similar cor- relations (R* = 0.2; p < 0.01) between 61°C and salin- ity. CORALS The 65°C and 8'8O data for the skeleton of the coral collected from Lignumvitae Basin have been reported previously (Swart er al., 1996; 1999). The average an- Table 2.—Results of linear regression analyses. 5'8O vs. salinity Area Intercept Slope R? Number Florida Bay Inner +0.33 0.06 0.26 S3}7/ Eastern Middle —0.83 0.08 0.31 293 Western Middle —2.39 0.11 0.30 242 Outer == 07) 0.09 0.09 194 Whitewater Bay +0.35 0.07 0.34 395 Ten Thousand Islands —0.2 0.06 0.28 395 0.077 -2.0 -6.07] -8.0 T l T Oct-93 Jun-95 Feb-97 Oct-98 Jun-00 Text-figure 4+—Five month running mean of the 6'°C composition of the DIC in all regions studied. Error bars represent + one standard error. nual values for both corals are shown in Text-figure 9. The Manatee Bay coral (—2.58 + 0.3%c) is slightly isotopically enriched in 6!°O relative to the Lignum- vitae coral (—2.04 + 0.5%c), and has more negative 63C values (—6.45 + 0.43%o vs. —3.25 + 0.58%o for the Manatee Bay coral). CONTINUOUS SALINITY MONITORING DATA Continuous salinity data collected from Lignumvi- tae Basin in Florida Bay are shown in Text-figure 10. The continuous data from Lignumvitae Basin have been averaged into monthly values and are plotted with the FIU/SERP data. The FIU /SERP data repre- sent water samples collected on a single day within the month. Generally the agreement between the two datasets is excellent considering the different temporal resolution between them. DISCUSSION SOURCES OF SALINITY VARIATION Relatively few studies have examined the 6'*O and 6D of precipitation in South Florida. The data pre- dC vs. salinity P Intercept Slope R? Number 1p <0.01 =3);7/5) 0.11 0.20 516 <0.01 <0.01 —6.54 0.12 0.11 296 <0.01 <0.01 —7.99 0.16 0.05 244 <0.01 <0.01 — 10.90 0.26 0.10 184 <0.01 <0.01 =8.33 0.10 0.20 364 <0.01 <0.01 STO 0.09 0.20 336 <0.01 24 BULLETIN 361 6.00 4 4.00 — 4 —~ | ~— 200 we 7 0.00 + -2.00 T T T i T T T ] T ] 0.00 10.00 20.00 30,00 40.00 50.00 Salinity Text-figure 5—Mean monthly 6'*O values versus salinity for all sites in Florida Bay. Error bars represent +1 one standard deviation. sented in this study show that the isotopic composition of South Florida precipitation falls near the MWL (Text-fig. 3). It is relatively depleted with volume weighted means of 5D and 8'8O —9.95%ec and —2.90%oc, respectively (Table 1). Based on a correlation between 6D and 6!8O, the data from the Everglades plot below the MWL (Text- fig. 3). Deviation away from the MWL is a well- known phenomenon and arises through the differential influence of evaporation of the oxygen and hydrogen isotopes. In the case of the Everglades data, the close- ness of the slope of the best fit line through the data Salinity NR uo 8'°C (°/o0) Text-figure 7—Mean monthly 5'°C versus salinity for all sites in Florida Bay. (5.8) to the slope of the MWL, suggests evaporation at a high relative humidity (Gonfiantini, 1986). Meyers et al. (1993) predicted a mean relative humidity of 80% for the Everglades based upon a stable isotope evaporation model. The time series trend of the Ev- erglades data (Text-fig. 2) shows some seasonality with isotopically more positive values toward the end of the dry season when evaporation typically exceeds precip- itation. The intercept of the best fit line through the Ever- glades data with the MWL is similar to the isotopic composition determined for South Florida precipita- tion (Text-fig. 3). These results indicate that precipi- tation is the ultimate source of the evaporated water in the Everglades, Everglades water can be distinguished isotopically from its parent precipitation. The mean 5'8O and 5D of the Everglades water is +0.55%ce and Outer FB White Water Bay SALINITY 30 40 50 0 10 20 30 40 50 Ten Thousand Islands Text-figure 6.—Comparison of the linear relationship between 8'8O and salinity for the six major areas designated in Text-figure 1. J 4) g g STABLE ISOTOPIC VARIATION: SWART ET AL. 25) a) “ee Tra) a a 10 20 30 40 50 3 Eastern Middle FB Western Middle FB oe 2 ° oO 0 0 Qye2 -4 -6 -8 WA A -19 14 * 0 10 20 30 40 Outer FB White Water Bay SALINITY Ten Thousand Islands Text-figure 8.—Comparison of the linear relationship between carbon isotopic composition (DIC) and salinity for the six major areas designated in Text-figure 1. +6.75%c, respectively, as compared to —2.90%c and —9.95%c for the precipitation. Florida Bay exhibits a wide range of 5!°O values related to evaporation, precipitation, and mixing with water derived from the Everglades, the Gulf of Mex- ico, and the Florida Reef Tract. The wide range of 6!°O values was noted by Lloyd (1964) who was unable to exhibit any relationship between salinity and 5!8O. In contrast to the study of Lloyd (1964), the data in this study were collected within a temporal and spatial framework and consequently the apparent poor corre- lation between salinity and 6!°O noted by Lloyd can be explained by mixing between different end-mem- — -1.00 + Bay ~~ Zo) -5.00 0.00 2 > ss | << a) = Oo © 1000 Manatee Bay Text-figure 9 —Oxygen and carbon isotopic data from corals col- lected from Lignumvitae Bay and Manatee Bay. bers with similar salinity, but differing 6'°O values. These relationships can be visualized on a 6!*O vs. salinity plot (Text-fig. 11) comparing the 6'°O com- position and salinity of the relevant end-members wa- ters: Everglades, precipitation, and seawater. Data for the seawater end-member are derived from previous studies (Ortner et al., 1995; Leder et al., 1996; Swart, 40.00 This Paper 36.00 Salinity 32.00 28.00 Jun-95 Apr-96 Feb-97 Dec-97 Oct-98 Date Text-figure 10.—Comparison of data collected from the continu- ous salinity monitoring stations and data collected by FIU on a monthly basis. Salinity data have been averaged from hourly data into monthly values. Error bars represent + one standard deviation. 26 BULLETIN 361 Oxygen oOo | 1 ' 1 ! t 1 I 1 I I 1 ! ' ! 1 ! Nal ‘1 aE > a Gulf of Mexico/Atlantic Water 0 10 20 30 40 50 Salinity Text-figure 11.—Model for the evolution of waters in the coastal region of Florida Bay showing the salinities and 6'O of three end members. Marine water from the Gulf of Mexico and the Atlantic (A) has a salinity of approximately 35.5 and a 6'*O of +0.5 to +1.5%c. This mixes with (B) rainwater (6'8O = 0 to —6%c; mean = —2.9%c) or water from the (C) Everglades (6'9O = —4.5 to + +4.5%e; mean = +0.55%c). Evaporation can take place at any time from any mixture. Evaporation of the marine water will produce a trend along a line (D). unpublished data), and have a 6!°O of between +0.5 and +1.5%c and a salinity between 35 and 36. The model proposed herein suggests that South Florida es- tuarine waters plotting along a linear correlation be- tween 6'8O and salinity with an intercept of 0 to + 1%c reflect mixing of seawater with Everglades runoff. Es- tuarine waters plotting along a linear correlation with an intercept near —2%c or lower indicate mixing of seawater with precipitation. Variation in the intercept between these two extremes reflects varying contri- butions from both runoff and precipitation and scatter in these relationships reflect the presence of multiple sources and processes such as evaporation (Text-fig. 11). The intercept of the linear correlation between 6'*O and salinity changes from being more negative in the western areas (Outer and Western-middle) of Florida Bay to being more positive in the eastern areas (East- ern-middle and Inner) of Florida Bay (Table 2; Text- fig. 11). These results indicate that inputs of precipi- tation is most responsible for varying salinity in the western areas of Florida Bay. Conversely, runoff from the Everglades is more important for the variation in salinity in the eastern portion of Florida Bay. For Whitewater Bay and the Ten Thousand Islands areas, the intercept of the correlation between 5'*O and sa- linity is close to zero (Table 2) suggesting that the salinity variation in these regions is principally a result of runoff from the Everglades, and in particular from Shark Slough. SOURCES OF CARBON ISOTOPIC VARIATION The 65°C of the DIC in all the surface waters from the estuarine environments was highly variable and showed a limited relationship with salinity (Table 2 and Text-fig. 7 & 8). Stronger correlations between 5'C and salinity were observed in the areas most in- fluenced by runoff from the Everglades. These areas include the Inner area of Florida Bay, White Water Bay and the Ten Thousand Islands. Although the 6'°C of the Everglades was not measured routinely through- out this study, measurements that were made on se- lected samples from the Everglades reveal that these waters had negative 6'°C values (Meyers, 1990). Hence when these waters flowed into the marine en- vironment, the result was a strong correlation between dC and salinity. In contrast, the absence of a strong relationship between 6'°C and salinity in the more sa- line portions of Florida Bay supports the relative lack of influence of Everglades waters on these portions of Florida Bay. Despite the absence of a correlation between 64°C and salinity in the central and western areas of Florida Bay sites, the waters at these sites show a considerable amount of variability in 6'°C which is probably related to local remineralization of organic material. The most negative 61°C values that are attained in Florida Bay (mean = ~—3%c) is a reflection of the more marine nature of this organic material compared to the White Water Bay and Ten Thousand Island area (6'"C be- tween —S5%o and —7%c) where most of the organic material is derived from terrestrial sources. CORALS Considering the relatively poor correlation between salinity and 6'°C of DIC, there appears to be little util- ity in relating the 6'°C of calcareous skeletons to input of freshwater except in the environments which are the closest to the Everglades. In the central areas of Flor- ida Bay, where it has been established that there is a relative absence of freshwater input using the 6!°O data, the changes in the 5'°C of calcareous organisms can be interpreted as reflecting increased oxidation of organic material, perhaps leading to an increase abun- dance of nutrients. The correlation between the 6'C and 5!*O of coral skeletons can be used as an indicator of the relative influence of freshwater. Corals from areas where there is relatively little influence of freshwater will have rel- atively little correlation between the two isotopes in STABLE ISOTOPIC VARIATION: SWART ET AL. Di -2.00 + -4.00 4 4 Gam wy | ~) O -6.00 a | . Ze) 4 ; . Manatee Bay 192=0.18 Bape 8.00 oa -10.00 ; 1 ] T ] -6.00 -4.00 -2.00 0.00 2.00 8 OC») Text-figure 12.—Relationships between 6'°C and 6'%O in the coral skeletons from Lignumvitae Basin and from Manatee Bay. Note that in the Lignumvitae data there is no correlation between the two isotopes (R* = 0.04)as predicted from an absence of a correlation in the two isotopes in the water at that site. In Manatee Bay however there is a correlation between the two isotopes which is statistically significant at the 99% level (R* = 0.14). their skeletons, while corals influenced by runoff should have a better correlation. These correlations can be seen in data from the coral collected from Manatee Bay which shows a strong positive correlation between skeletal 5'°C and 8!8O (R = .42, n = 362, p > .0001). In contrast, corals from Lignumvitae Basin show no correlation between the two isotopes (R = 0.003, n = 1894, p = not significant) (Text-fig. 12). These cor- relations are similar to the relationships seen between the 6'°C and 6!*O of waters. For example, results from a linear regression model between 5'°C of DIC and salinity has an R* of 0.2 (Table 2). In western-middle Florida Bay, where the Lignumvitae Basin is located, an R? of 0.05 is obtained (Table 2). APPLICATION TO EXISTING PALEOENVIRONMENTAL DATA Combining the salinity relationship beteen Lignum- vitae Basin along with 6'8O record of the coral skel- eton collected from Lignumvitae Basin, attempts have been made at estimating salinity variations in other regions of Florida Bay (Swart ef al., 1996; 1999). Based on data presented in this paper, however, the equation linking the skeletal 6'°O and salinity in Lig- numvitae Basin (Swart ef al., 1999) is not valid for other areas of Florida Bay. Consequently different equations for estimating salinity from 6!*O need to be derived for every location. While this is impractical in real terms, One can obtain an idea of the influence of the variations by calculating the relationships between salinity and 6!°O for the different geographic sub-re- gions designated for Florida Bay (Text-figs. 1, 6). As an example of the influence that these different rela- tionships have on the calculation of the salinity from a 6'8O record, we examined the 6!8O record of a coral from Lignumvitae Basin and a coral of a similar genus growing in Barnes Sound near the mouth of Manatee Bay. In order to compare the salinity estimates, we used three methods to determine the salinity at the mouth of Manatee Bay. These are (1) the transfer func- tion approach presented by Swart er al. (1999) using the 6'8O of coral skeletons growing in Lignumvitae Basin and the modern salinity correlations between the two basins, (2) using a coral actually growing in a site and the correlation between salinity and 6!*O for Lig- numvitae Basin, and (3) using the Manatee Bay coral and the salinity vs. 6!°O relationship presented in this paper. We then compared these salinity estimates di- rectly with measurements by FIU/SERP and the Uni- versity of Miami in Barnes Sound. In the first com- parison, the data from the coral growing in Lignum- vitae Basin was converted to salinity using the equa- tion presented by Swart et al. (1999) which related salinity to the temperature (T) and the 5'*O of the coral skeleton (equation 1). This provided an estimate of salinity with a slightly greater amplitude than the Lig- numvitae coral, but significantly higher than the range in salinity measured in Manatee Bay (Text-fig. 13). Salinity = 4.9885!°O iP dlaiwe se IS oy? (1) coral In the second approach equation | was also used, but in this case the data from the coral actually growing near the mouth of Manatee Bay was used (Text-fig. 13). This gave an estimate similar in pattern to the method used previously, but with much higher salinity estimates than the salinities actually measured (Text- fig. 13). The third method uses the new relationship between salinity and 6!*O,,,,.. shown in Table 4. In or- der to convert the 6!°O of the coral skeleton to salinity we used the relationship established by Leder ef al. (1996) between temperature and skeletal 5'°O for the species Monastrea annularis and assumed an annual mean temperature of 25°C. Combining these two equa- tions a new formula can be derived which is specific for corals growing in the inner portion of Florida Bay. This relationship is shown in equation 2. Salinity = 4.148'8O.,,4) + 0.978T + 9.33 (2) cora The results of these three calculations together with the range of salinities actually measured at the site in Manatee Bay are shown in Text-figure 13. This visual comparison shows that the best estimate of salinities 28 BULLETIN 361 40 30 Salinity 1965 1975 1985 1995 Date Text-figure 13.—Line (1) represents the salinity in Barnes Sound estimated using the 6'SO data from the coral in Lignumvitae Basin (Swart er al., 1996, 1999). Line (2) represents the salinity estimate calculated from the 6'°O of the Manatee Bay coral using the rela- tionship between salinity and 6'*O,,,., established for Lignumvitae Basin. Line (3) is the new relationship between salinity and 6!°O for the inner region of Florida Bay established in this paper (Table 4). The ranges in salinity measured by FIU and presented in this paper are indicated by the arrow. measured at the site are provided by the method in which we used the correlation between salinity and 5!°O, er for inner Florida Bay. Previously estimates for the salinity in this portion of Florida Bay are therefore likely to have been too high (Swart et al., 1999). How- ever, in spite of the distance between the two locations (Lignumvitae Basin and Manatee Bay), the coral in Lignumvitae Basin shows a similar temporal pattern in 6'8O to the Manatee Bay Coral and with the appro- priate calibration the Lignumvitae coral record (Swart et al., 1996) can be used to estimate salinities in other portions of Florida Bay. CONCLUSIONS 1) Relationships between salinity and 6!8O vary ac- cording to relative distance from the Everglades. This changing relationship is caused by an increasing influ- ence of rainfall compared to runoff in controlling sa- linity variations. For example, the western portion of Florida Bay appears not to be significantly influenced by runoff from the Everglades and salinity variations there are related to changes in the amount of precipi- tation. Application of a constant salinity vs. 5!°O re- lationship in the interpretation of 6'°O values of cal- careous organisms from South Florida estuaries is not appropriate. 2) Carbon isotopic variations in Florida Bay are re- lated to the oxidation of organic material. Large vari- ations in the 6'°C of the DIC occur both within saline and freshwater environments. Within the saline envi- ronments, there is little relationship between salinity and 6'°C while in the freshwater environment, there is a strong correlation between salinity and 54C. REFERENCES CITED Boyer, J.N, Fourqurean, J.W., and Jones, R.D. 1999. Seasonal and long-term trends in the water quality of Florida Bay (1989-1997). Estuaries, vol. 22, pp. 417— 430. Coplen, T.B., Woldman, J.D., and Chen, J. 1991. Improvements in the gaseous hydrogen-water equilibra- tion technique for hydrogen isotope ratio analysis. Ana- lytical Chemistry, vol. 63, pp. 910-912. Craig, H., and Gordan, L.I. 1965. Deuterium and oxygen-18 variations in the oceans and the marine atmosphere. in Stable Isotopes in Oceanographic Studies and Paleotemperatures, E. Tongiorgi, ed., Consig- lio Nazionale delle Ricerche, Laboratori Geologia Nucle- are, Pisa, pp. 9-130. Davis, R.A., Jr. 1997. Geology of the Florida Coast. in The Geology of Florida, Randazzo, A.F and D.S. Jones, eds., University Press of Florida, Gainesville, pp. 155—168. Epstein, S., and Mayeda, T. 1953. Variations in O'* content of waters from natural sources. Geochimica et Cosmochimica, vol. 27, pp. 213-224. Fennema, R.J., Neidrauer, C.J., Johnson, R.A., MacVicar, T.K., and Perkins, W.A. 1994. Understanding the Ecosystem. in The Everglades Hand- book, Thomas E. Lodge, ed., St. Lucie Press, Delray Beach, FL, pp. 249-289. Fourqurean, J.W., and Robblee, M.B. 1999. Florida Bay: A history of recent ecological changes. Es- tuaries, vol. 22, pp. 345-357. Fourqurean, J.W., Zieman, J.C., and Powell, G.V.N. 1992. Phosphorus limitation of primary production in Florida Bay: Evidence from the C:N:P ratios of the dominant sea- grass Thalassia testudinum. Limnology and Oceanogra- phy, vol. 37, pp. 162-171. Friedman, I. 1953. Deuterium content of natural waters and other substances. Geochimica et Cosmochimica Acta, vol. 4, pp. 89-103. Gat, J. 1981. Isotopic fractionation. in Isotope Hydrology: Deuterium and Oxygen-18 in the Water Cycle, J. Gat, and R. Gon- fiantini, eds., Vienna, IAEA, pp. 21-31. STABLE ISOTOPIC VARIATION: SWART ET AL. 29 Gonfiantini, R. 1986. Environmental isotopes in lake studies. in Handbook of Environmental Isotope Geochemistry A., Volume 1, P. Fritz, and J.C. Fontes, eds., Amsterdam, Elsevier, pp. 113-168. Halley, R.B., and Roulier, L.M. 1999. Reconstructing the history of eastern and central Florida Bay using mollusk-shell isotope records. Estuaries, vol. 22, pp. 358-368. Kushlan, J.A. 1990. Freshwater Marshes. in Ecosystems of Florida, Myers, R.L. and J.J. Ewel, eds., University of Central Florida Press, Orlando, FL., pp. 324-363. Leach, S.D., Klein, H., and Hampton, E.R. 1972. Hydrologic effects of water control and management of oS —) southeastern Florida, Florida Bureau of Geology Report of Investigations, vol. 60, 115 pp. Leder, J.J., Swart, P.K., Szmant, A, and Dodge, R.E. 1996. The origin of variations in the isotopic record of Scler- actinian corals: | Oxygen, Geochimica et Cosmochimica Acta, vol. 60, pp. 2857-2870. Lloyd, M.R. 1964. Variations in the oxygen and carbon isotope ratios of Flor- ida Bay mollusks and their environmental significance. Journal of Geology, vol. 72, pp. 84-111. Meyers, J.B. 1990. Stable isotope hydrology and diagenesis in the surficial aquifer system, southern Florida everglades. Unpublished M.S. thesis, University of Miami. 92 pp. Meyers, J. B., Swart,P. K., and Meyers, J.L. 1993. Geochemical evidence for groundwater behavior in an un- confined aquifer, south Florida. Journal of Hydrology, vol. 148, pp. 249-272. Nelsen, T.A., Wanless, H.R., Trefry J.H., Alvarez-Zarikian, C., Hood, T., Blackwelder, P. Swart, P., Tedesco, L., Kang, W-J., Metz, S., Garte, G., Fetherstone, C., Souch, C., Pachut, J.F., O’Neal, M., and Ellis, G. 2001. Linkages between the South Florida peninsula and coastal zone: A sediment-based history of natural and anthropo- genic influences. in Linkages Between Ecosystems in the South Florida Hydroscape: The River of Grass Continues. K. Porter and J. Porter, eds., CRC Press, Boca Raton, Florida (in press) Nuttle, W.K., Fourqurean, J.W., Cosby, B.J., Zieman, J.C., and Robblee, M.B. 2000. Influence of net freshwater supply on salinity in Florida Bay. Water Resources Research, vol. 36, no. 7, pp. 1805— 1822. Ortner, P.B., Lee, T.N., Milne P.J., Zidka, R.G., Clarke, M.E., Podesta, G.P., Swart, P.K., Testa, P.A., Atkinson, L.P., and Johnson, W.R. 1995. Mississippi river flood waters reached the Gulf Stream, Journal of Geophysical Research, vol. 100, pp.13,595— 13,601. Rozanski, K., Aragus-Aragus, L., and Gonfianitini, R. 1993. Isotopic patterns in modern global precipitation. in Cli- mate Changes in Continental Isotopic Records, P. Swart, K. Lohmann, J. McKenzie, and S. Savin, eds., Volume 78: Geophysical Monograph, Washington, DC, American Geophysical Union, pp. 1-36. Smith, T.J. II, Hudson, J.H., Robblee, M.B., Powell, G.V.N., and Isdale, P.J. 1989. Freshwater flow from the the Everglades to Florida Bay: A historical reconstruction based on flourescent banding in the coral Solenastrea bournoni. Bulletin of Marine Sci- ence, vol. 44, pp. 274-282. Swart, P., Sternberg, D., Steinen, R., and Harrison, S. 1989. Controls on the oxygen and hydrogen isotopic composi- tion of waters from Florida Bay, USA. Chemical Geology, vol. 79, pp. 113-123. Swart, P.K., Healy, G., Dodge, R., Kramer, P., Hudson, H., Hal- ley R., and Robblee, M. 1996. The stable oxygen and carbon isotopic record from a coral growing in florida bay: A 160 year record of climatic and anthropogenic influence. Palaeogeography, Palaeoclima- tology, Palaeoecology, vol. 123, pp. 219-238. Swart, P.K., Healy, G., Greer, L., Lutz, M., Saied, A., Anderegg, D., Dodge, R.E., and Rudnick, D. 1999. The use of proxy chemical records in coral skeletons to ascertain past environmental conditions in Florida Bay. Estuaries, vol. 22, pp. 384-397. bh aac wee (4) CGS ea i : ; ; eee Ome et —s UA slp at -" a reat tee CHARTERS SEDIMENT DYNAMICS OF FLORIDA BAY MUD BANKS ON A DECADAL TIME SCALE CHARLES W. HoLMEs!, JOHN ROBBINS?, ROBERT HALLEY!, MICHAEL BOTHNER®, MARILYN TEN BRINK*, AND MArRcI Marot! 'U.S. Geological Survey, 600 4" St. South, St. Petersburg, FL 34701 °Great Lakes Environmental Research Laboratory, (NOAA), Ann Arbor, MI 48105 5U.S. Geological Survey. Woods Hole, MA 02543 ABSTRACT Ecosystem management requires knowledge of environmental dynamics. If historical environmental records do not exist, other methods must be employed to obtain this information. A well-known geochemical procedure that supplies this type of data is the use of natural radioactive nuclides to “date” the timing of events. Of the many naturally occurring nuclides, *!°Pb is the best suited for gauging the timing of episodes in Florida Bay. The age-depth relationships were calculated using the *!°Pb method for thirty-five sites within Florida Bay. The ages were independently confirmed by comparing the distribution of known concentrations of atmospherically anthropogenic lead recorded in dated cores to similar data in an annually banded coral. Sediments in the western and northern fringe of Florida Bay are accumulating at ~0.3 cm/yr, a rate similar to that of sea level rise. In the north- central part of the bay, sediments are accumulating at a faster rate of ~1.0 cm/yr. The highest rate, =2.0 cm/yr was measured in the northeastern part of the bay on the bank between Pass and Lake Keys. The rapid rate of accumulation in the northeastern part of the bay permits the deciphering of biological and geochemical changes with an accuracy of about two years. In contrast, the intermediate sediment rate in the central part of the bay provides adequate age-depth for relationships deciphering the environmental record of the past 100 years. INTRODUCTION Any retrospective analysis of natural systems re- quires a temporal frame of reference against which dy- namic processes can be measured. The lack of ade- quate historical environmental records within the Flor- ida Bay system necessitated the development of a method to determine the timing of environmental al- terations. Conventional wisdom implies that the natu- ral hydrology was significantly altered over the past 100 years. However, prior to any “‘restoration”’ effort, it is prudent to determine what changes are the result of natural processes and which are not. The keys to this information lie within the sedimentary record. To read this record properly, the first requirement is to establish accurately a temporal frame of reference. A program was initiated in 1994 to define the environ- mental record with the sediments of Florida Bay. The project was a cooperative between the South Florida Water Management District, the U.S. Geological Sur- vey, and the Great Lakes Environmental Research Laboratory (N.O.A.A.). Sediments have been accumulating in Florida Bay for approximately 4000 years (Scholl, 1964). The bas- al sediments are brackish and freshwater peats and marls, similar to those presently accumulating in the Everglades (Davies and Cohen, 1989). Overlying these sediments are marine sediments that form a network of mud banks and islands that partition the bay into more than 30 small basins. The basins range from one to four meters in depth and are up to a few kilometers wide (Text-fig. 1). The bulk of the sediments is in the banks and islands and is predominantly silt- and clay- sized carbonate particles. Most of the mud is derived from the physical breakdown of larger skeletal frag- ments, with a contribution from calcareous algae that produce micron-sized carbonate needles (Boscence, 1989a). The minor amount of sand-sized and coarser material is the result of the debris from a great variety of calcareous invertebrates living in the bay (Bosc- ence, 1989a). Although much work has been devoted to the origin, composition, and distribution of sediments in Florida Bay (Boscence, 1989b), the processes that have cre- ated the mudbanks and their rate of formation are poorly understood. It is commonly held that the south or west sides of the mud banks are accreting while the northern and eastern sides are eroding (Wanless and Taggert, 1989). '*C dating of peats and carbonate sed- iments provide a general picture of the time of sedi- ment formation. However, these data do not address the dynamics of sediment transport—particularly in re- gard to the mobile, fine-grained particles. This infor- mation is important in defining stratigraphic relation- 32 BULLETIN 361 a * Coral Site 25°00 N Key Contours in feet Core Sites ——~— + A 7-30 — a) Mud Banks a Core Locations Nautical Miles After USC &G SCharts 1249,1250 1. Buchanan Bank N. 10. Russell Bank S. 19. Russell Bank S. 2. Buchanan Bank S. 11. Johnson Key 20. Bob Allen Bank 3. Rabbit Key 12. Porjoe Bank 21. W. Pass Key 4. Cluett Key 13. Trout Creek Spit 22. Russell Bank 5. Whipray Basin 14. Little Madeira Bay 23. Park Key Bank 6. Bob Allen S. 15. E. Pass Key 24. Bob Allen Bank 7. Rankin Bight 16. Crocodile Point 25. Whipray Basin 8. Lake Ingraham 17. W. Pass Key 9. Russell Bank N. 18. Russell Bank S. 81°00 W 80:00 W Text-figure 1—Location of coring sites in Florida Bay. ships within the deposits. To obtain this information, chronological methods using short-lived isotopes were employed. The requirements for an isotope to be a candidate for dating sediments are that: (1) the chemistry of the isotope (element) is known; (2) the half-life is known; (3) the initial concentrations of the isotopes are known or can be accurately estimated; (4) the only change in concentration is due to radioactive decay; and (5) in order to be useful, it must be relatively easy to mea- sure. If all these conditions are met, the effective range for each isotope is about eight half-lives. Four natu- rally occurring isotopes (’Be, tC, '*’Cs, and 7!°Pb) sat- isfy these criteria and have been found useful for mea- suring sedimentary dynamics in Florida Bay over the past 100 years. *10Pb is a common radioisotope that has become a mainstay of radiometric dating of sediment deposited during the last century (Goldberg, 1963). This method is based on a radioactive disequilibrium between 7!°Pb (t;. = 22.3 yr) and its parent, *?°Ra (t,. = 1600 yr). The radioactive disequilibrium is the result of the sep- aration in the decay chain caused by the diffusion of the intermediate daughter, *’Rn. The physical and chemical process that lead to this disequilibrium have been described and critiqued in reviews by Robbins (1978) and Appleby and Oldfield (1992). ACKNOWLEDGMENTS We wish to acknowledge the efforts of Peter Swar- zenski and James Flocks who made a significant con- tribution to this report in discussions with the senior author. We would also like to acknowledge Fran Glick of Mariner Hospital al in Tavernier and Larry Wise of Fisherman’s Hospital in Marathon for providing the x- radiographs, which played a vital role in the selection of cores. The South Florida Water Management Dis- trict provided much of the funding for this work. Da- vid Rudnick was the contracting official and his work (and worry) is greatly appreciated. There are many others, too numerous to mention here, who labored long and hard under the hot sun and late into the even- SEDIMENT DYNAMICS: HOLMES ET AL. 333} ing to collect and section cores; to those people we are extremely grateful. PROCEDURES SAMPLING PROCEDURES Twenty-five locations were selected for coring in Florida Bay to obtain a comprehensive overview of the different environments (Text-fig. 1). In keeping with the goal of the program—to develop a method of establishing a sediment chronology—most coring sites were located on the accretionary side of the mudbanks. It is there that the potentially longest sediment record is likely. Additional cores were collected in other en- vironments, such as on the “erosional” side of a mud- bank (Site 18—Russell Bank and Site 12—Porjoe Bank), within the central part of selected basins (Site 5—Whipray Basin; Site 7—Rankin Bight; Site 8— Lake Ingraham) and on the fringe of the Everglades (Site 13—Trout Creek Spit, Site 14—Little Madeira Bay and Site 16—Crocodile Point). Duplicate cores were taken at selected sites. In all, 27 cores were an- alyzed. The cores (10 cm i.d.) were collected with a conventional piston coring device. All cores were driven to the limestone surface and averaged ~1.5 meters in length. Extreme care was ex- ercised to preserve the sediment-water interface and to minimize disturbance. Prior to sampling, each core was x-rayed to determine the presence of laminations and to evaluate the extent of mixing. If there was no observable disturbance during sampling, handling, or transport to the laboratory, the cores were sectioned into 2 cm intervals for analysis. Cores located on Buchanan Bank (North and South), on Cluett Key, Russell Bank north, and on the eastern part of Pass Key were disturbed and therefore were not analyzed. LABORATORY ANALYSIS Wet and dry bulk density, acid insoluble residues, loss on ignition, and grain size analysis were deter- mined for each interval (Holmes er al., 1998). Since 2!°Pb is adsorbed on the clay-sized particles, analyses were performed on the <0.062 mm fraction. The total 71°Pb content of the sediment samples was measured on freeze-dried subsamples by both alpha spectrome- try, with selected samples also analyzed by gamma techniques. The samples, which were >99% carbon- ate, were “ashed” at 450°C for 6 hrs to destroy any organic material, and dissolved in 8N HCl. The alpha spectrometry procedure closely followed the method detailed by Flynn (1968). Overall counting uncertain- ties were +2%. Replicate samples were analyzed by gamma methods at the Woods Hole USGS Laboratory (M. Bothner and M. Ten Brink) as well as at the Great Lakes Environmental Research Laboratory (J. Rob- bins) and the results were within counting error of measurements made by alpha methods. The **°Ra val- ues were measured on selected samples by gamma spectrometry. Further detail of the analytical proce- dures and results from the replicate analyses are pre- sented in Holmes er al. (1998). RESULTS AND DISCUSSION SITE CHARACTERIZATION In this study, attention was given to the selection of coring sites that were thought to contain well-pre- served sediments and high accumulation rates. Coring focused on the recovery of finely laminated sediments, which generally indicate a lack of physical or biolog- ical mixing (Ball et al., 1967; Shinn, 1968; Wanless and Taggert, 1989). Three factors are thought to con- tribute to the formation of the laminated sediments in Florida Bay: 1. Rapidly deposited mud becomes quickly de-wa- tered by as much as 50% so that they become suffi- ciently cohesive to exhibit pseudo-conchoidal fracture and can resist erosion. 2. The interior of the Bay is characterized by ex- treme variations in temperature and salinity relative to the open Gulf of Mexico or the Atlantic Ocean. These fluctuations limit the diversity of burrowing organisms that can live in the Bay. 3. Florida Bay sediments are rich in sulfide (SO0— 5000 4M), which inhibits biological activity (William Orem, 1998, personal communication). The combination of these factors creates an envi- ronment wherein short-lived radionuclides can be used successfully to measure sedimentation rates. Geochemical Models The calculation of “‘ages” by the *!°Pb method is usually based on one of two models: the constant rate of supply model or the constant initial concentration model. The constant rate of supply (CRS) model as- sumes that the flux of 7!°Pb is constant over time re- gardless of how the sediment flux might vary. The constant initial concentration model is based on the assumption that the concentration of *!°Pb at time zero (when the sediment was deposited) has been constant over time. Robbins er a/. (2000) examined several var- iations of these models. As a result, a secular equilib- rium model, which assumes that a fraction of the *!°Pb present in the sample must be in equilibrium with >°Ra, and that there is a constant flux of 7!°Pb with the attendant adsorption, seems to be the most appro- priate model for these sediments. Individual cores were analyzed by applying a best- fit curve to the data using an unweighted Marquardt- Levenberg parameter optimization method (Press ef 34 BULLETIN 361 Table 1.—Concentration of 210Pb in Penicillus sp from site in northeastern Florida Bay. Total Pb-210 activity Sample no. Location (dpm/g) Latitude Longitude June 1994 1 Peterson Keys 2.32 24.7330 80.7500 2 Russell Key 4.02 25.0660 80.6330 3 Rabbit Keys 1.22 24.9900 80.8330 4 Bob Allen Key 1.93 25.0300 80.6730 5 Johnson Basin 1.70 25.1330 80.9250 August 1994 1 Buttonwood Sound 3.64 25.0853 80.4542 2 Buttonwood Sound 2.79 25.0933 80.4480 3 Buttonwood Sound 3.92 25.1008 80.4425 4 Buttonwood Sound 3.49 25.1072 80.4367 4U Buttonwood Sound 2.43 25.1072 80.4367 5 Buttonwood Sound D728} 25.1128 80.4438 SA Buttonwood Sound 2.56 25.1128 80.4438 6 Buttonwood Sound 2.24 25.1063 80.4492 8 Buttonwood Sound 4.33 25.0908 80.4613 9 Buttonwood Sound 2.81 25.0963 80.4675 10 Buttonwood Sound 3.14 25.1033 80.4620 11 Buttonwood Sound 2.22 PPS IS) 80.4553 13 Buttonwood Sound gl 25.1242 80.4567 17 Buttonwood Sound 8555 25.1147 80.4755 18 Buttonwood Sound 3.58 25.1228 80.4688 19 Buttonwood Sound 4.16 25.1295 80.4642 19D Buttonwood Sound 1.90 25.1295 80.4142 25 Little Maderia Basin 8.66 25.1600 80.6233 26 Little Maderia Basin 6.10 25.1342 80.5833 October 1994 94-glw-201HAL Lignum Vitae Basin 0.72 24.9370 80.6957 94-glw-201PEN Lignum Vitae Basin Hater 24.9370 80.6957 94-glw-202HAL Twinkeys 0.44 24.9617 80.6669 94-glw-202PEN Twinkeys 1.35 24.9617 80.6669 94-g]w-203PEN Spy Keys 1.96 24.0123 80.7644 94-glw-204HAL Twin Key Basin 0.59 24.9898 80.7839 94-glw-204PEN Twin Key Basin 1.44 24.9898 80.7839 94-glw-205SPEN N. Rabbit Key 1.86 24.9816 80.8242 94-glw-207HAL Peterson Bank 0.85 24.9189 90.7472 94-glw-207PEN Peterson Bank 1.97 24.9189 90.7472 HAL = Halameda, U = Udotea, PEN = Penicillis, D = Dasycladaceae, A = Duplicate. al., 1989). A distinct advantage of this procedure is that all data points, including negative values (which are the result of counting errors, etc.), are used in the sediment accumulation rate calculations. This method has the further advantage of correcting for the ‘old age’ error, which is inherent in many other best-fit in- terpolation routines. Special Geochemical Considerations (Florida Bay) *10Pb dating of marine sediments in the coastal en- vironment is generally complicated by the multiplicity and variability of sources and by physical perturba- tions of sediment mixing. Thus, the assumptions used in correctly applying *!°Pb as a geochronological tool can be seriously violated. However, in northeastern Florida Bay there are a variety of conditions, in ad- ditional to the physio-chemical conditions previously enumerated that suggest that the *!°Pb distribution can provide a sound basis for dating the sediments. First, a major source of excess 7!°Pb is the atmo- spheric flux of 7!°Pb. In Florida Bay, input from other sources such as groundwater and in situ production (via *?Rn) must also be considered. Recent data by Chanton and Burnett (1995) have demonstrated high levels of *??Rn in Florida Bay waters. The likely source is ground water exchange with the elevated levels of parent radionuclides in the underlying Pleistocene rocks. A measure of this reactivity is the measurement of *!°Pb activities in the carbonate secreted by the short-lived algae Penicillus sp. This alga, which has a life span of ~45 days, is a good monitor (Stockton et al., 1967). The concentration of *!°Pb in the algal car- SEDIMENT DYNAMICS: HOLMES ET AL. 35 Radium (dpm/g) versus Lead-210 (dpm/g) Lead -210 (dpm/g) i) o | 1 1 l 1 1 n LE 4 1 ! si n 1 0.00 0.50 1.00 1.50 2.00 2.50 Radium (dpm/g) Text-figure 2.—Plot of the *°Ra activity versus the total *!°Pb activity showing a positive relationship with the sediments of Florida Bay (r = 0.68). bonates is highest in areas where there is very little sediment covering the “bedrock” (Table 1). This is consistent with a ground water or bedrock source and would provide a constant flux of *!°Pb to the waters of Florida Bay. Second, even though Rude and Aller (1991) mea- sured the maximum excess *!°Pb activity (1.1 dpm/g) to be only about half the background (noise) at the top of the core on Bob Allen Bank, there are a number of characteristics of the 7!°Pb and **°Ra profiles that ap- pear to be favorable for geochronological purposes: 1. The radium values vary within a limited range (<20%) over the one-meter long cores. 2. Sediment mixing, as evidenced from a 20-cm zone of nearly constant excess *!°Pb activities, was confined to the surface of the core. Conventional steady-state sediment mixing and accumulation mod- els can be accurately used to determine a mixing depth and/or mixing rate as well as a sediment accumulation rate (Robbins ef al., 2000). 3. Rude and Aller (1991) calculated a mean linear accumulation rate of 1 cm/yr at the Bob Allen Key site which favors the use of reasonably short sediment cores to reconstruct historical records of system chang- es over the past 100 years. 210Pbh and ?°°Ra Distribution Calculating *‘?!°Pb ages” according to the model of Robbins er al. (2000) requires the determination of a portion of the *!°Pb that is “supported” by *°Ra. A number of investigators assume that the radium distri- bution is constant and equal to the value where the total *!°Pb activity is constant with depth. They use this value to subtract from the total 7!°Pb, eliminating the need for independent radium measurements. In or- der to validate this assumption for the Florida Bay sediments, a large number of radium measurements were made on samples from eight cores. These cores were chosen to represent various environments of the Bay. The Bob Allen Bank cores (6A and 6C), Russell Bank cores (19B and 19C), and Pass Key Bank cores (7D and 17G) were taken from the accreting sides of the banks. The Whipray Basin core (5G), Trout Creek Spit core (13), and Crocodile Point core (16B) repre- sent the non-accreting fringing environments. In each core from an accreting environment, radium systematically decreased with depth. A linear best-fit of the radium versus depth for individual cores had r- squared values (goodness of fit) which ranged from 0.6-0.9. The slopes and the surface intercept of the individual curves varied within narrow limits, between —0.002——0.003 for the slope and 1.9—2.2 for the sur- face intercept. The coherence of the radium distribu- tions between these cores suggested that a singular ex- pression, *?°Ra.,, = —0.0025(depth) + 2.0 (where cal = calculated value) could be used to describe the ra- dium distribution on accreting banks (Text-fig. 2). 36 BULLETIN 361 Russell Bank (Core 19C) 0 | ry | . 226 } Pee kee Ra wea 40 | 210 —@ L “4° = & 30 - a 120 |— | 39 | ee ee le l 2 3 4 5 6 Total Activity - dpm/g (Radium-226 and Lead-2 10) Text-figure 3.—Distribution of **°Ra and total *!°Pb in the Russell Bank (Core 19C). However, for non-accreting banks, where *!°Pb activity approaches a minimum in the upper part of the cores, the similar, more generic relationship was determined for *!°Pb and radium *°Rag,,y. = 0.16 Total 7!°PBgpnjc + 1.37 (where dpm/g + total activity). Comparison of ages using calculated versus measured radium values yielded insignificant differences. The total *!°Pb activities for all samples ranged from 1.5—6.0 dpm/g. Subtracting a background value of 2.2 dpm/g for the radium content of the most recently de- posited sediments; the maximum excess 7!°Pb signal was 3.8 dpm/g. A typical plot of excess 7!°Pb vs. depth from Russell Bank (Core 19C) demonstrates that Flor- ida Bay sediment are in sufficient disequilibrium for calculating accurate geochronology (Text-fig. 3). Text- figure 3 clearly shows that a discernable difference can be observed in *!°Pb and *°Ra down to a depth of 100 cm. This diagram also shows the consistent decrease in radium with depth. The core in Whipray Basin (5G) has high ?!°Pb ac- tivity at the top and, interestingly, also elevated activ- Whipray Basin (Core 5G) 0 | eee r = ee 20 — oe + 210 aT Pb (Gamma) 8 60 |— << eh Tk fa) 80 7% SA \\210 LO is a \ Pb (Alpha) r a 120 | 2 SA) | oe ee 140 i it it | it it it | i it i | it 1 it | i it it 1 2 3 4 5 6 Total Activity (dpm/g) Text-figure 4.—Distribution of **°Ra and total 7!°Pb in the Whi- pray Basin Core 5G. Also plotted is the total *!"Pb as determined by gamma spectroscopy that demonstrates very good agreement be- tween the two methods. ity at the bottom (Text-fig. 4). Gamma spectrometry measurements of these cores suggest that the increased activities observed in the bottom sediments are likely the result of elevated radium and uranium activities. This phenomenon has been detected in the cores taken within the Everglades; in cores from the northern por- tion of Florida Bay: Rankin Bight (Site 7), Johnson Key (Site 11), Trout Creek (Site 13), and Little Ma- deira Bay (Site 14); and in cores near the islands in the southern Bahamas (Tedesco and Aller, 1997). The remaining cores show a conventional exponential de- crease in excess *!°Pb with depth. The most obvious difference between these cores appears to be the depth at which apparent equilibrium (7.e., total activity equals supported activity) is reached. This is clearly seen by comparison of the S. Russell Bank (19C) and the Whipray Basin (5G) cores. Age calculations for the S. Russell Bank cores indicate that the bottom sediments are at least 150 years old, whereas the Whipray Basin cores reach “‘equilibrium” in the upper 20 to 40 cm and the bottom sediment has been '*C dated as 3300 years BP. The Pass Key cores SEDIMENT DYNAMICS: HOLMES ET AL. 37 Table 2.—Core location, average rate of accumulation for the last 100 years, and total excess *!°Pb inventory of cores used in this chapter. Location Tait Core Rate tory Site No. N W cm/yr dpm/cm? Comment Rabbit Key Basin SBP 24959!06) 9 80)50:25) 10!35) ==0!05, 3.3. Northern edge of basin in a grass bed. Whipray Basin 5G 2504.26 804431 0.37 + 0.06 8 Eastern side of the basin in a barren patch. Bob Allen Bank 6A 2501.39 8039.41 0.75 + 0.08 46 South side of the bank in a grass bed. Bob Allen Bank 6@ > 25/0139) 18039741 1.08 + 0.10 79 10 m from 6A in a barren spot. Rankin Bight [Bae 251092555 80i47262-—~ 0:338== 10105 28 Northeastern edge of the bight about 100 m from shore. Lake Ingraham 8B 25 08.85 8105.88 3.57 + 0.50 32 West side of central channel in the middle of the lake. Russell Bank 10B 25 03.84 80 37.52 1.00 + 0.08 141 Top of the bank'. Johnson Key Basin 11A 2503.10 8054.39 0.37 = 0.04 5.6 Eastern side of basin in a grass bed. Porjoe Bank 12B 25 08.04 80 28.42 0.50 + 0.08 35 Eastern side of the bank in a grass bed. Porjoe Bank 12D 25 08.04 80 28.42 0.50 + 0.08 36 Eastern side of the bank in the same grass bed as 12B. Trout Creek Spit ISD 25250 SOS 99 0411005 PE Spit on the eastern side of the entrance to Trout Creek. Little Madeira Bay 14B 2510.65 8037.44 0.85 + 0.09 22 Mouth on the eastern side of Little Madeira Bay. Crocodile Point 16B 2508.32 8043.68 0.33 + 0.06 85 Transverse north-south bank in grass bed’. Pass Key Bank 17D 2508.86 8034.49 3.50 + 0.12 165* Top of bank in the middle of the old channel. Pass Key Bank 17G 25 08.86 80 34.49 5.80 + 0.60 230* Top of bank, 5 m from 17G in a barren site. Russell Bank I8B 25.03.98 8037.46 0.75 + 0.06 48 Northern side of the bank’. Russell Bank 19B! 2503583) 80137748) 1-27 210108 54 South side of bank in deeper water than 10B (grassy). Russell Bank 19C 25 03.83 80 37.48 0.97 + 0.08 71 South side of bank 10 m from 19B (barren). Bob Allen Bank 20D 2501.39 80 39.41 1.56 + 0.20 182 South side of bank in a barren “hole” deeper than 6A. Pass Key Bank 21B 25 08.86 80 34.49 3.00 + 0.08 462* Top of bank in the middle of the old channel. Pass Key Bank ZE 25109106) | 803457, 78050) 19 Western side of bank, south of old channel. Pass Key Bank 21F 25 08.83 = 80 34.21 1.91 + 0.06 114* Western side of bank, south of the old channel. Russell Bank 22D 2503.88 8037.55 0.88 = 0.08 55) Top of bank to the north and west of core site 19. Park Key 23A 2506.27 80 34.47 0.78 + 0.05 25 Northern side of the bank, sparse grass. Bob Allen Bank 24A 2501.42 80 33.84 0.78 + 0.09 25 South side of bank, 1 km southeast of 6. Bob Allen Bank 24C 2501.42 8033.84 0.73 + 0.08 20 South side of bank, 1 km southeast of 6. Whipray Basin 25B 25 04.27 8044.31 0.43 + 0.07 23, Eastern side of the basin in deeper water than site 5. ' The core “Russell Bank 10C” appears to be in three segments: a top part that has either been rapidly deposited or is mixed, a middle part that has the character of a grass bed (a highly variable *'°Pb signal and a lot of grass fragments), and a bottom part. > The top 20 cm are disturbed. The rate of accumulation was calculated for the section of the core below the mixed layer. 3 The top of the core appears to represent material that has “slumped” into place. The rate was calculated using part of this zone. do not attain equilibrium. Age calculations and pho- tographic evidence indicate that the core bottom sed- iments (~1 m) are less than thirty years old A sum- mary of the rates of accumulation is given in Table 2. Confirmation and Replication of *!°Pb Ages Shen and Boyle (1987) measured stable lead con- centrations in the annual bands of a Monastrea an- nularis coral collected on the ocean side of the Florida Keys, directly east of this study area. The total stable lead concentration in this coral reached a maximum around 1977, which corresponds to the peak use of leaded gasoline. In three cores, 6A and 6C (Bob Allen Bank) and 19C (S. Russell Bank), the down core pro- file of stable lead was determined by ICP-MS. These core and coral sites are located less than five miles apart. The stable lead concentrations for both the cores and coral are plotted against time (Text-fig. 5). The ages of the cores were calculated from the *!°Pb data, while the age of the coral was determined by counting the annual bands. The clear concordance of these in- dependently dated profiles confirms the validity and accuracy of our sediment geochronology. The within-station variability in sedimentation rates was estimated using two cores collected 10 meters apart on Bob Allen Bank (Text-fig. 6). Core 6A was collected in a grass bed, while core 6C was taken in a barren area. Core 6A shows a fairly constant sedi- ment flux prior to 1965 with the minimum accumu- lation occurring during the mid-1930s. Since 1965, the flux rate has rapidly decreased. In comparison, at the non-vegetated site, the sediment flux fluctuated widely before the 1920’s. A distinct decrease in sedimentation occurred in the 1930’s, followed by a sharp increase up to 1950. After 1950, the sediment flux has been decreasing steadily. The patterns between the two cores are remarkably similar, suggesting that the same forces control sediment accumulation in both areas, though to slightly different degrees. There is also a difference in bulk density between the two cores. The average density of sediment within the grass bed is 0.7 g/cm’, whereas the average density of the sediment at 38 BULLETIN 361 Bob Allen Core 4.5 a " mt 3.5/_ ot oll Coral Data _, 3 2.5 as 2.0 | - AC ‘Core Data i) 1D ie - @e -. a x 4 es 2s ma ee (le Eee Sr Se] e 1860 1880 1900 1920 1940 1960 1980 2000 — Year eo} a Sie South Russell Bank Core Ol eS [e = ane . ae rh a oe Core a? 2.5 Data ~ wich 2.0 — e e° ta L 45 a0 °° 8°°a" "\Coral Data 0 e@ (ye ee er ee 1860 1880 1900 1920 1940 1960 1980 2000 Year Text-figure 5.—Comparison of the distribution of stable lead with dated cores (6A and 19C) and a dated coral. the barren site is 0.9 g/cm?. The core taken in the grass bed contains a high percentage of plant material, which decreases the overall density of the sediment. A similar comparison can be seen in the Pass Keys Cores—17D and 17G (Text-fig. 7). Sedimentary Dynamics As mentioned above, the source of excess ?!°Pb is a result of the severed decay chain by the gaseous ***Rn. As a result *!°Pb can reach a site of deposition via atmospheric fallout or a combination of atmospheric fallout and particle transport in which lead is added along the route of transport. The atmospheric flux along the northeastern coast of the United States has been measured as 1.0 + 0.2 dpm/cm®? (Turekian er ai., 1983). This would produce a steady state inventory of excess *!°Pb of 32 + 6 dpm/cm?. Similar inventories determined in lowland soil profiles in the eastern Unit- ed States average 26 + 4 dpm/cm,. Baskaran ef al. (1993) measured the atmospheric flux at Galveston and College Station, Texas, as varying between 0.67 and 1.71 dpm/ cm?/yr, with a mean of 1.03 dpm/cm?/ yr. Their data also demonstrated the flux differences in between continental and marine sources, with the ma- rine sources producing a smaller flux than the conti- nental source. In south Florida a flux of 0.8 dpm/cm?/ Bob Allen Bank 1.40 — — — —_—___— r ’ 1.20 F I Core 6C - Barren Site ° le || L mm) fs e fait ii Te fo Ct hdl | g Wor gs LS lel Nhe ES rt oe es? one) : ® = 0.80 Hike y 2) \~ 8 \ Sura Mu J 5 wa ll | os | \ 5 0.60 ¢ & Ay % | [ Phe “sl laa Core 6A-Grass Site % 0.40 4 a 0.20 4 | a 0.00 & He | Si | 1 Se | L 0 50 100. 150 200 250 Years (BP) Text-figure 6—Comparison of sedimentation rates between core 6A (Grass) and 6C (Barren) from Bob Allen Bank. The high vari- ation in sedimentation rates in the barren core (6C) may be related to climate fluctuations (see Cronin er al., this volume). yr was measured at the University of Miami for the year 1997 by Dr. Frank Millero (written communica- tion, 1998). This would yield an inventory of ~25 dpm/cm?’. Dalphino ef al. (1993) estimated an inven- tory of 19 dpm/cm? which would suggest an average flux for south Florida of ~0.6 dpm/cm?/yr. These low- er values are consistent with the proposed marine source of air masses that move across south Florida. Inventories of excess 7!°Pb have been calculated for each core from: Q, = > (:hA;) where Q, = inventory of excess 7!°Pb, p,; = dry bulk density of the ith depth interval (gy,, /em*), h, = thick- ness of the ith interval (cm), and A; = excess 7!°Pb of the ith interval (dpm/g). The summation of the excess Pass Key Bank Cores 17D and 17G 2.50 + F Core 17D (West of Bank) Is o | a 2 1 WA AK 2.00 | a | te M Ye M\ 7 | 3 nit one Pe ary AR t | 2 , Mk \ Rae | a mx : § Nee oe B 1.50 + A E | n » A, 5b we ON \ of Core 17G (Top of Bank) a | mo 4 1.00 aba Fei ete Seal ree es TS eR Ln, 0 10 20 30 40 50 60 Years (BP) Text-figure 7.—Comparison of sedimentation rates between core 17D and 17G from Pass Key. The difference in sedimentation rates can be attributed to their relative locations to the central channel. SEDIMENT DYNAMICS: HOLMES ET AL. 39 values was carried out from the surface to that level in which the difference between background and ex- cess 7!°Pb activity was indistinguishable. The inven- tories record in the cores ranges from 3 dpm/cm, to >400 dpm/cm?. Assuming that the excess *!°Pb inven- tory should be in the 20 to 30 range if all of the lead was a result of atmospheric flux, these extreme values lead to some indications of the sediment dynamics. The inventories are presented in Table 2. Those sites with inventories significantly lower than can be ac- counted by the atmospheric flux indicate that some sediment has been removed. The three such sites are on the southern and western sides of the Bay. In Whi- pray basin, the core with the lowest inventory (5G) is much shallower than core 25. The *'°Pb distribution curve in this core has an apparent discontinuity at about 16 cm hinting at an interval of missing sediment. Along the northern fringe of the bay, the inventory in cores 7, 13, 14 and 16 imply that the source of lead was wholly atmospheric. At all the rest of the sites, the high inventories are indicative of sediment *!°Pb “enriched” by focusing and/or an external non-atmo- spheric source, possibly ground-water fluxes. In gen- eral, the highest inventories were measured on Pass Key bank, where the highest rate of sediment accu- mulation occurs forming the bank within the last 30 years. The high rate on Bob Allen Bank (core 20) was measured at a site in deeper water further south than the other cores, consistent with the idea of southward accretion of the banks. SUMMARY The determination of sediment geochronologies us- ing *!°Pb at various sites within the sedimentary banks of Florida Bay has yielded a valid time scale on the order of decades. These calculated ages have been con- firmed by independent means. At sites in the western portion and along the northern fringe of the Bay, sed- iment accumulation is ~0.3 cm/yr. At sites in the west- ern part of the Bay, the inventory of *!°Pb is much less than atmospheric flux, indicating that sediment has been removed, probably by storms. In the northeastern section of the Bay, which is most impacted by chang- ing salinity regimes, the sedimentation rates vary from 0.7 cm/yr to greater than 2.0 cm/yr. In the central part of the study area on the leeward side of Russell Bank and Bob Allen Bank, the sediment accumulation rate is moderate (~1.0 cm/yr). It is from these sites that the ecological history of Florida Bay during the last century could best be developed. Additional ongoing studies are addressing other geochemical and paleon- tological issues (Cronin ef al., 1998). This investiga- tion on the feasibility of dating the sediments in Flor- ida Bay has proven to be quite successful; the infor- mation is being used to reconstruct the paleoecological history of the bay and to assess the transport and de- position of Florida Bay sediments. REFERENCES CITED Appleby, P.G., and Oldfield, F. 1992. Application of lead-210 to sedimentation studies. in Ura- nium-series Disequilibrium. Applications to Earth, Marine and Environmental Studies. M. Ivanovich, and R.S. Har- mon, eds., Oxford Science Publishers, Clarendon Press, Oxford, Second Edition, pp. 731-778. Baskaran, M., Colman, C.H., and Santschi, P.H. 1993. Atmospheric depositional fluxes of 7Be and *!°Pb at Gal- veston and College Station, Texas. Journal of Geophysical Research, vol. 98, pp. 20,555—20,571. Boscence, D. 1989a. Biogenic carbonate production in Florida Bay. Bulletin of Marine Science, vol. 44, pp. 419—433 1989b. Surface sublittoral sediments of Florida Bay. Bulletin of Marine Science, vol. 44, pp. 434—453. Chanton, J., and Burnett, W. 1995. Delivery of nutrients to Florida Bay by submarine groundwater. FSU Project report no. 1368-689-37, 15 p. Cronin, T. M., Holmes, C.W., Wingard, G. L., Ishman, S., Dow- sett, H., and Waibel, N. 2001. Historical trends in epiphytal ostracodes from Florida Bay: Implications for seagrass and macro-benthic algal variability. Bulletins of American Paleontology, no. 361, pp. 159-197. Dalphino, J.J., Crisman, T.L., Gottgens, J.F., Rood, B.E. and Earle, C.D.A. 1993. Spatial and temporal distribution of mercury in Ever- glades and Okefenokee wetland sediments, Final report SEWMD, Contract C91-2237, 138 pp. Davies, T. D., and Cohen, A. D. 1989. Composition and significance of the peat deposits of Flor- ida Bay. Bulletin of Marine Science, vol. 44, pp. 387— 398. Flynn, W.W. 1968. The determination of polonium-210 in environmental ma- terials. Analytica Chimica Acta, vol. 43, pp. 121-131. Goldberg, E. D. 1963. Geochronology with Lead-210. in Radioactive Dating, [.A.E.A., Vienna, pp. 121-122. Press, W. H., Flannary, B. P., Teukolsky, S.A., and Vettering, V.T. 1989. Numerical Recipes: The Art of Scientific Computing. Cambridge University Press, New York, NY, 702 pp. Robbins, J. A. 1978. Geochemical and geophysical applications of radioactive lead. in Biogeochemistry of Lead in the Environment, Part A. J. O. Nriagu, ed., Elsevier Scientific Publishers, Amsterdam, Netherlands, vol. 1A, pp. 285-393. Robbins, J.A., Holmes, C.W., Halley, R. B., Bothner, M., Shinn, E. A., Graney, J., Keeler, G., Ten Brink, M., and Rud- nick, D. 2000. Time constants characterizing pre-depositional integration 40 BULLETIN 361 of '*’Cs and Pb fluxes to sediments in Florida Bay. Journal of Geophysical Research, vol. 105, pp. C28,805—28,822. Rude, P. D., and Aller, R. C. 1991. Fluorine mobility during early diagenesis of carbonate sediment: An indicator of mineral transformation. Geo- chimica et Cosmochimica Acta, vol. 55, pp. 2491—2509. Scholl, D. W. 1964. Recent sedimentary record in mangrove swamps and rise in sea level over the southwestern coast of Florida, parts I and I. Journal of Marine Geology, vol. 1, pp. 344-366. Shen, G. T., and Boyle, E. A. 1987. Lead in corals: Reconstruction of historical industrial fluxes to the surface ocean. Earth and Planetary Science Letters, vol. 82, pp. 289-304. Stockman, K. W., Ginsburg, R. N., and Shinn, E. A. 1967. The production of lime mud by algae in south Florida. Journal of Sedimentary Petrology, vol. 37, pp. 633-648. Tedesco, L.P., and Aller, R.C. 1997. ?'° Pb chronology of sequence affected by burrow exca- vation and infilling; examples from shallow marine car- bonate sediment sequences, Holocene South Florida and Caicos Platform, British West Indies, Journal of Sedimen- tary Research, Section A: Sedimentary Petrology and Pro- cesses, vol. 67, no. 1, pp. 36-46. Turekian, K.K., Benninger, L.K., and Dion, E.P. 1983. /’Be and ?!°Pb total depositional fluxes at New Haven, Connecticut and at Bermuda. Journal of Geophysical Re- search, vol. 88, pp. 5411—S415. Wannless, H., and Taggert, M. G. 1989. Origin, growth and evolution of carbonate mudbanks in Florida Bay. Bulletin of Marine Science, vol. 44, pp. 454— 495. CHAPTER 4 THE FLORIDA EVERGLADES ECOSYSTEM: CLIMATIC AND ANTHROPOGENIC IMPACTS OVER THE LAST TWO MILLENNIA DEBRA A. WILLARD!, CHARLES W. HOLMES?2, AND LISA M. WEIMER! 'U.S. Geological Survey, Eastern Surface Processes Team, 926A National Center, Reston, VA 20192 °U.S. Geological Survey, Center for Coastal and Marine Geology, 400 6th Street South St. Petersburg, FL 33701 ABSTRACT We document the response of the Everglades ecosystem to climatic and environmental changes over the last two millennia using pollen records. Centennial-scale intervals of vegetational stasis characterize the time between 0 A.D. and 1900 A.D. From 0-800 A.D., marsh and slough vegetation characteristic of deeper water and longer hydroperiods (annual duration of inundation) than today dominated the study region. Drier conditions between about 800 A.D. and 1200 A.D. resulted in shallower water depths and shorter, fluctuating hydroperiods in Everglades marshes as well as salinity increases near Florida Bay. After a recovery to deep-water conditions in the 14" century, somewhat drier conditions are suggested between the 17" and 19" centuries. These climatically-induced periods of relative dryness are correlated with regional droughts during the intervals known as the Medieval Warm Period (9"—-14" centuries) and Little Ice Age (15""—19" centuries). Although regional precipitation was greater than average after 1920 A.D., vegetational changes throughout the area indicate reduced water depths and hydroperiods after construction of water-contro] structures in the early 20" century. Further, more localized changes occurred after 1960, when the Central & South Florida (C&SF) Project was completed. Thus, restoration goals of achieving pre-C&SF Project hydrologic regimes are aimed at an already disrupted system; a more “natural” restoration target would be the 19" century Everglades, which had been stable for the past few centuries. Recent land-use changes have resulted in localized rather than system-wide ecosystem responses, at least in part because of the fragmentation of the wetland. This artificially induced ecological heterogeneity makes prediction of future wetland responses to climatic changes problematic. INTRODUCTION In wetland ecosystems, climatic warming is expect- ed to cause lowered water tables, increased rates of evapotranspiration, and, in the Florida Everglades, greater incidence of saltwater intrusion from both sea- level rise and hydrologic changes (Watson ef al., 1996). Additionally, anthropogenic changes in hydrol- ogy and nutrient availability due to land-use alterations affect wetland ecosystems on both local and regional scales. The accurate prediction of wetland response to future climatic and environmental changes is ham- pered by a lack of broad-scale, long-term studies of past changes in wetland ecosystems. Such studies are feasible in the Florida Everglades, where we have col- lected a series of cores that preserve records of the last 2,000 to 3,000 years of Everglades vegetation (Text- fig. 1). These cores provide data on past responses of wetland vegetation to late Holocene climatic events as well as hydrologic alteration of the system over the last century. A possible analog for Everglades re- sponse to a predicted warming of 1°C to 3.5°C by 2100 A.D. (Watson ef al., 1996) is preserved in sediments deposited during the Medieval Warm Period (MWP) ‘ Deceased. (800-1300 A.D.) (Hughes and Diaz, 1994) when sea- surface temperatures at least 1°C warmer than today have been documented in the Sargasso Sea (Keigwin, 1996). The impact of a cooling event, the Little Ice Age (LIA) (A.D. 1550-1850) (Bradley and Jones, 1993) on Everglades vegetation also is preserved in many cores throughout the region. Of particular inter- est are the timing and extent of vegetational changes in response to hydrologic changes and changing land- use practices of the last century. This suite of cores provides the temporal and spatial coverage necessary to address these questions on a regional basis. Vegetational distribution in the Everglades wetland is controlled primarily by water depth, hydroperiod (average annual length of inundation), substrate, fire regime, and water chemistry (Kushlan, 1990). Al- though plant community composition can vary locally, several broad vegetational categories have been iden- tified (Davis et al., 1994; McVoy et al., 2000; Willard et al., 2001a). These include: the Ridge and Slough region consisting of a mosaic of sawgrass-dominated marshes, sloughs, and tree islands in the north and central Everglades and ranging southwest through the Shark River Slough; sparse sawgrass marshes and wet prairies in the southern Everglades; cypress swamps 42 BULLETIN 361 PI LAKE OKEECHOBEE Hillsboro Canal | WCA3A\ it 26° ‘Shark River Tamiami Trail ae BISCAYNE BAY ATLANTIC OCEAN 10 20 7 We == F Z MILES LORIDA BAY UY 950 fo} fe} {2} (=) eo) oO foo) Text-figure 1.—Map of core locations discussed in this study. De- tailed locality information is provided in Table 1. and domes and pinelands in the Everglades and Big Cypress National Preserve; and mangrove forests along the Florida Bay and Whitewater Bay coasts (Text-fig. 2). This report presents reconstructions of the vegetational history of the Everglades ecosystem at several sites over the last two millennia and its re- sponse to both natural climatic fluctuations and altered land-use practices of the last century. ACKNOWLEDGMENTS The research was supported by the U.S. Geological Survey Integrated Natural Resource Science Program (INATURES) in cooperation with the South Florida Water Management District. For field and technical as- sistance, we thank C. Bates, P. Buchanan, A. Fagen- holz, M. Cangelosi, C. Fellman, J. Herring, H. Lerch, M. Marot, J. Murray, W. Orem, T. Sheehan, and N. Waibel. L. Brewster-Wingard and S. Ishman provided data on molluscan and foraminifer assemblages for site 8. For their helpful input during the project, we thank T. Cronin, S. Davis, W. DiMichele, T. Fontaine, A. Higer, C. Labandeira, C. McVoy, W. Park, P. Rawlik, K. Rutchey, FE Sklar, D. Verardo, S. Verardo, B. War- dlaw, and Y. Wu. Valuable comments on earlier ver- sions of the manuscript were provided by E. Grimm, O. Davis, D. Peteet, and P. Swart. We thank the staffs of Big Cypress National Preserve, Everglades National Park, Loxahatchee National Wildlife Refuge, and Ro- tenberger and Holey Land Wildlife Management Areas for assistance gaining access to their lands. STUDY SITES AND METHODS Peats preserved in the historic Everglades provide a detailed archive of biotic patterns over the last few millennia. Cores discussed herein were collected in Water Conservation Areas 1, 2, and 3, in Taylor Slough, and in the dwarf mangrove fringe adjacent to Florida Bay (Text-fig. 1, Table 1). These sites were selected to evaluate past vegetational patterns in the Ridge and Slough area, where relatively minor chang- es in hydroperiod and water depth may alter the spatial distribution of vegetation types, and in the saline-in- fluenced part of the Everglades, where hydrologic changes may result in salt-water intrusion. Pollen assemblages and geochronology were ana- lyzed from samples collected at I—2 cm intervals throughout the cores. Most cores are about 0.7 meters long, cover the last two millennia (Tables 1, 2), and reach the underlying Pleistocene limestone. Age mod- els for the last century of deposition are based on 7!°Pb, '7Cs, and 'C from atomic testing (Robbins er al., 2000) and, where applicable, first occurrences of pol- len of the exotic plant Casuarina which was intro- duced to south Florida in the late 19" century (Lande- land, 1990). In older sediments, models are derived from linear interpolation between radiocarbon data points (Table 2), which were calibrated to calendar years using the Pretoria Calibration Procedure (Stuiver et al., 1993; Talma and Vogel, 1993; Vogel et al., 1993). In cores where both bulk radiocarbon dates and AMS dates on plant fragments were obtained, age models are based on the AMS dates, which minimize the possibility of contamination by sediments outside the sample interval. Pollen was isolated from samples using standard palynological techniques (Traverse, 1988), including carbonate and silicate removal with HCl and HF when necessary, acetolysis to reduce the amount of phytodebris, sieving through 8 4m mesh to remove clay-size particles, heavy liquid treatment when needed, and staining with Bismarck Brown be- fore mounting on microscope slides with glycerin jel- ly. Tablets with known numbers of Lycopodium spores also were added to the dry samples for determination of pollen/gram dry sediment (see (Maher, 1981). To calculate percent abundance in each sample, at least 300 pollen grains were identified and counted. In some cases, pollen preservation was poor, and counts of at least 100 grains were included in the analyses. Pollen data and closest analogs are available via the internet CLIMATIC AND ANTHROPOGENIC IMPACTS: WILLARD ET AL. 43 Gulf of Mexico Florida Bay 81° Pinelands Wet Prairies Cypress forests ELE Southern marl- forming marshes Mangroves Developed areas Rockland Pine Forests Sloughs Sawgrass marshes Ey | Biscayne Bay / 80.5° Text-figure 2—Generalized map of vegetation types, developed areas (urban and agricultural), and boundaries of Water Conservation Areas, Big Cypress National Preserve, Everglades National Park, and Loxahatchee National Wildlife Refuge. Compiled from Davis (1943) and Davis et al. (1994). from the North American Pollen Database (NAPD) at the World Data Center for Paleoclimatology in Boul- der, CO (http://www.ngdc.noaa.gov/paleo/pollen.htm1) and at the US Geological Survey South Florida Eco- system History Database at http://flaecohist.erusgs. gov/database. We interpreted vegetational changes in cores from patterns in both percent abundance and concentration (pollen/gram dry sediment) of pollen. The timing of major vegetational changes is clear from examination of pollen diagrams. However, to improve the accuracy of vegetational interpretations based on pollen data, we statistically compared assemblages from cores to those from modern samples using both cluster analysis and Table 1.—Site locations, core length, and date of core collection for sediment cores, South Florida. Latitude Longitude Core length Site (N) (W) General location (cm) Date collected l 26°28.873' 80°24.931' Loxahatchee NWR 72 4/21/1995 2 26°21.580' 80°22.230' Water Conservation Area 2A 72 4/26/1995 3 26°17.254’ 80°24.660' Water Conservation Area 2A 71 4/25/1995 4 25°58.455’ 80°40.129' Water Conservation Area 3A 70 4/27/1995 5) 25°17.231' 80°38.780' Taylor Slough 76 5/20/1996 6 DS mle ale 80°41.227' Taylor Slough 78 5/24/1996 7 25712339! 80°38.64 1 Everglades National Park 86 3/29/1995 8 25°13.190' 80°36.279' Everglades National Park 82 3/15/1996 44 BULLETIN 361 Table 2.—Radiocarbon dates from peat cores, South Florida. Site Depth (cm) Beta no. Sample type 3C/"C ratio Corrected ''C age (BP) Calendar age 1 30-32 110295 Bulk 26:2, 480 + 40 AD 1410-1470 | 50-52 110296 Bulk —27.4 960 + 40 AD 1005-1180 1 70-72 110297 Bulk —26.2 1590 + 40 AD 405-575 2 14-16 104814 AMS—leaf —P)''6 175.2% + 0.4 post 1950 2 28-30 104815 AMS—leaf lox, 1040 + 50 AD 860-960 2 32-36 90032 Bulk —26.3 1090 + 60 AD 800-920 2 40-42 104816 AMS—leat —16.8 19110) = 50 10 BC-AD 90 2 52-56 90033 Bulk —26.3 1990 + 60 100 BC-AD 20 2 60-64 90034 Bulk —26.1 2270 + 60 380-260 BC 3 26-28 129850 Bulk = 2)7fa I 400 + 50 AD 1425-1635 3 38—40 129849 Bulk —27.4 930 + 50 AD 1005-1220 3 50-52 129848 Bulk —27.4 W/OOKERS 0) AD 235-435 3} 64-68 90034 Bulk —26.6 2090 + 60 4 30-32 110292 Bulk —?)5)(6) 610 + 40 AD 1295-1420 4 50-52 110293 Bulk =2519) 1880 + 40 AD 65-240 4 64-68 110294 Bulk — Psy 2470 + 40 BC 780—405 5 30-32 110298 Bulk —P5)-5) 1500 + 40 AD 465-645 5 50-52 110299 Bulk = 72333) 2460 + 40 BC 780—405 5 72-74 110300 Bulk 23:8 3560 + 40 BC 1975-1760 6 30-32 115197 AMS—leaf —27.0 310 + 40 AD 1600-1680 6 44-46 114967 Bulk —26.8 320 + 50 AD 1580-1680 6 60-62 115644 AMS—leat —30.6 530 + 60 AD 1305-1460 7 0-4 104507 AMS—twig PHS) 109.8% + 0.6 post 1950 7 4-8 104508 AMS—twig = 26:5) 96.0% + 0.4 post 1950 7 13-14 86194 Bulk ye: 370) 60 AD 1520-1640 7 20-24 104510 AMS—twig —26.8 230 + 40 AD 1680-1760 a 24-26 96195 Bulk — TS} 700 + 70 AD 1180-1320 a 75-76 86785 Bulk —26.5 1610 + 60 AD 280—400 8 30-32 96610 Bulk Uf 300 + 80 AD 1570-1730 8 58-60 93311 Bulk =i 750 + 80 AD 1120-1280 8 78-84 93312 Bulk ihe 1950 + 70 70 BC-AD 70 Note: Site numbers correspond to sites in Figure 1. Radiocarbon dating was performed by Beta Analytic, Miami, Florida, dating both bulk sediment and selected plant fragments with AMS. When aerial material could not be separated confidently from the peat, homogenized bulk samples were used. Due to the possibility of contamination by younger roots, dates on bulk samples represent minimum ages for the intervals. Corrected dates are based on fractionation calculated by 6'°C. Calendar ages have been calibrated according to Stuiver et al., 1993, Talma and Vogel, 1993, and Vogel et al., 1993, + 2 o, and 95% probability. * These C13/C12 ratios were not determined but are estimates based on the peat composition. the modern analog technique. Cluster analysis and oth- er hierarchical classification techniques are used to show relationships among different samples based on species abundance in those samples. These relation- ships are determined by first calculating a sample-by- sample distance matrix and then linking samples into clusters based on their dissimilarity/similarity to each other (Gauch, 1982). We used average-linkage clus- tering (UPGMA) with the Pearson product moment correlation coefficient and the computer program MVSP 3.1 (Kovach, 1999) to cluster our samples. The modern analog technique compares fossil pol- len assemblages with modern assemblages from a number of vegetation types to identify the closest mod- ern analog (Overpeck et al., 1985). If close analogs exist for the fossil assemblage, it is assumed to have a similar vegetational composition and, by extension, similar environmental parameters, such as hydroperiod or water depth. Modern analogs are identified by cal- culating a dissimilarity coefficient between a fossil and modern assemblage; samples with dissimilarity coef- ficients less than a critical value are considered to rep- resent the same vegetation type. To determine the ap- propriate critical value for these samples, we calculat- ed dissimilarity coefficients (using squared chord dis- tance, or SCD) among all modern samples using the ANALOG program of Schweitzer (1994) (see Willard et al., 2001a). Samples from the same vegetation type typically had SCD values <0.15. Recognizable wet- land subenvironments include sloughs, sawgrass marshes, sawgrass marshes near tree islands, southern Everglades sawgrass marshes/wet prairies, tree islands, southwestern mangrove forests, and cattail marshes. This modern dataset incorporates both samples col- lected between 1995 and 1998 and samples collected in the early 1960s. The latter group includes a number of sites that have since been altered by construction of the Central & South Florida (C&SF) Project since CLIMATIC AND ANTHROPOGENIC IMPACTS: WILLARD ET AL. 45 Table 3.—Clusters from Q-mode cluster analysis of modern and fossil pollen assemblages, modern analogs, and pollen signatures for each cluster. Cluster Modern analog Pollen signature I TREE ISLANDS Fern Spores > 25% 1a LOXAHATCHEE SAWGRASS MARSHES Myrica > 30% I SOUTHWESTERN MANGROVE FORESTS AND Rhizophora > 15%; Avicennia and Conocarpus present BRACKISH MARSHES IV SOUTHERN EVERGLADES MARSHES AND SLOUGHS IV a No modern analogs, but apparently fresh-water marshes Cyperaceae 22-32%; Myrica 18-30% IV b Wet Prairies (no fossils) Myrica 5—20%; Asteraceae > 15%: Sum of Cyperaceae and Sagittaria > 5% IV c Dwarf Mangrove Stands Rhizophora 5—25%; Myrica 2—12%; Cyperaceae 1—5% IV dl Wet Prairies, Cypress Stands, Pinelands Pinus > 40%; Myrica 5—12%:; Asteraceae > 5%; Cyperaceae > 2% IV d2 Sawgrass marshes Pinus 20-40%; Myrica > 15%; Asteraceae 3—10%; Cypera- ceae >3% Vv NORTHERN EVERGLADES MARSHES AND SLOUGHS Va Dense Sawgrass Marshes V bl Sloughs (primarily fossils) V b2 Sloughs, Dense Sawgrass Marsh Vc Sawgrass Marshes near Tree Islands or Disturbed Sites Cyperaceae > 10%; Asteraceae >10%; Sagittaria > 5% Nymphaea 5—20%; sum of Cyperaceae and Sagittaria > 5% Cheno/Ams 30-40%; sum of Nymphaea, Sagittaria, and Cy- peraceae > 10% Cheno/Ams > 40%; sum of Typha, Cyperaceae, and Sagit- taria > 10% 1960, and they include deeper water sloughs than oc- cur today. ECOLOGY AND POLLEN SIGNATURES OF EVERGLADES VEGETATION TYPES Eight vegetation types are clearly distinguishable from modern pollen assemblages collected throughout the Everglades (Willard ef al., 2001a). Slough vege- tation occurs in the wettest sites and typically is dom- inated by floating aquatics such as Nymphaea (water lily) and Utricularia (bladderwort). This community type grows in relatively deep water over thick peat substrates and requires long hydroperiods (>9 months annual inundation) (Kushlan, 1990). Pollen assemblag- es from sloughs are distinguished by >3% Nymphaea pollen (Willard ef al., 2001a) and include samples in cluster Vb (Table 3, Text-fig. 3). Marshes requiring moderate water depths (<1 me- ter) and hydroperiods (6—9 months annual inundation) include those dominated by Cladium (sawgrass), Sag- ittaria (arrowhead), Eleocharis (spikerush), and Typha (cattail). Substrate type, fire frequency, nutrient con- tent of surface waters, and disturbance determine the dominant component (Kushlan, 1990). Sawgrass marshes consist primarily of Cladium, grading into flag marshes with more Sagittaria and Eleocharis where surface sediments change from deeply organic peats to shallow peats and marls (Kushlan, 1990). Pol- len assemblages from typical sawgrass marshes are dominated by Cladium and Sagittaria pollen and are represented in clusters Va and Vb2 (Table 3). Cattail marshes, dominated by Typha, may replace sawgrass marshes after disturbances, such as severe fires or nu- trient enrichment (Davis, 1994). Sawgrass marshes near tree islands, near levees and canals, and with fluc- tuating water levels are dominated by pollen of weedy annuals, particularly Amaranthus (water hemp) or the Asteraceae (aster family) (Willard er al., 2001a). These plants are known to become particularly abundant after periods of rapid drying over a few (<5) years or pro- longed droughts (Loveless, 1950; Mc Voy et al., 2000). Pollen assemblages from both cattail marshes and saw- grass marshes associated with tree islands or distur- bance are included in cluster Ve (Table 3). Short hydroperiod marshes such as wet prairies re- quire shallow water depths, seasonal drying (O—3 months annual inundation), and either marl or shallow peat substrates (Kushlan, 1990). Sparse vegetation in these marshes consists primarily of taxa in the Poaceae (grass family) and Cyperaceae (sedge family) that tol- erate both dry and flooded conditions. These marshes, most common in the southern Everglades, have the greatest abundance of Myrica (wax myrtle) pollen, as well as Poaceae and Cyperaceae (Willard et al., 2001 a); wet prairies are represented in clusters [Vb and [Vd (Text-fig. 3, Table 3). Pinus pollen also is abundant in these assemblages; however, it represents extra-local deposition and reflects low pollen productivity of plants in this community type. Tree islands are interspersed throughout the marshes and sloughs of the Everglades, and two types exist. “Pop-up” or battery islands, dominated by bays (Per- 46 BULLETIN 361 | ! aval Il [ ae ae -0.2 0 0.2 0.4 0.6 0.8 1 Pearson Coefficient Text-figure 3.—Dendrogram from Q-mode cluster analysis (using UPGMA and Pearson correlation coefficient) of pollen assemblages from surface samples and down-core samples from sites 1-8, Florida Everglades. Cluster I represents tree-island samples. Cluster II represents samples from sawgrass marshes in Loxahatchee NWR. Cluster III includes samples from southwestern mangrove forests and brackish marshes. Cluster IV includes samples from southern Everglades marshes and sloughs. Cluster V includes samples from northern Everglades marshes and sloughs. Finer details on clusters are provided in Table 3. CLIMATIC AND ANTHROPOGENIC IMPACTS: WILLARD ET AL. 47 sea) and holly (lex), are the most common type in Loxahatchee National Wildlife Refuge; these sites are characterized by abundant //ex and Myrica pollen and are included in cluster II (Table 3). Fixed, tear-drop shaped tree islands, which are elongated parallel to flow, occur throughout the Everglades; vegetation on tree island heads consists of trees, shrubs, and ferns and the tapering tails are vegetated by shrubs, ferns and thick Cladium or Typha. Pollen assemblages from fixed tree islands are characterized by high abundances of fern spores and are represented in cluster I (Table 3). The high abundance of ferns is a local signature of the tree islands themselves, with fern spores rare in marshes and sloughs surrounding the islands (Willard, et al., 2001b). Two types of mangrove assemblages occur in South Florida: dwarf mangroves consisting primarily of short (<3 meters) Rhizophora near Florida Bay, and the tall, diverse forests near Whitewater Bay in Shark River Slough. Both types are distinguished in the pollen re- cord by abundant mangrove pollen, particularly that of Rhizophora. Near Florida Bay, mangrove pollen com- prises only about 20% of assemblages and consists primarily of Rhizophora with minor amounts of Con- ocarpus and rare Avicennia and Laguncularia. These are included in cluster [Vc (Table 3). In southwestern Florida, however, Rhizophora is the dominant element, and the four mangrove genera listed above combine to make up at least 40% of the assemblages (Riegel, 1965; Willard et al., 2001a). These samples comprise most of cluster III (Table 3). VEGETATIONAL HISTORY: RIDGE AND SLOUGH SITES PRE-20T4 CENTURY VEGETATION Four cores (sites 1—4: Text-fig. 1) in the Ridge and Slough region (Text-fig. 2) provide records of the last two millennia. From about 0-800 A.D., pollen evi- dence from these sites indicate that they typically were dominated by slough vegetation, indicating long hy- droperiods and relatively deep water (Text-fig. 4). Be- tween 800 A.D. and 1200 A.D., all sites show evi- dence for shallower water and shorter hydroperiods, although temporal resolution varies among the cores. At sites | and 4, comparison with modern analogs in- dicates that sawgrass marshes replaced sloughs for varying intervals between 800 and 1200 A.D. The great abundance of weedy annuals such as Amaranthus at site 4 and, to a lesser extent site 2, indicate that droughts or intervals of rapid drying (over <5 years) (Loveless, 1950; McVoy et al., 2001) occurred during that time, allowing weedy species to flourish. At site 2, Cladium pollen abundance increased and samples are grouped in cluster Vb2, indicating shorter hydro- periods and/or shallower water depths than before. During this interval at site 3, there are no close ana- logs, but samples cluster with marsh and slough sam- ples from the southern Everglades (Text-fig. 4), where water depths are shallower and peat substrates thinner. Although this is suggestive of drier conditions, the high percentages of Nymphaea make confident inter- pretation of hydrology problematic at this site. Be- tween 1200 A.D. and 1600 A.D., deeper water con- ditions associated with slough vegetation returned at all four sites, although site 3 remained similar to south- ern Everglades sloughs. Early in the 17" century, Myr- ica pollen doubled in abundance at all four sites, and Nymphaea pollen decreased in abundance at most sites. Although the assemblages remained analogous to sloughs, the increased abundance of tree pollen is suggestive of drier conditions beginning in the early 17" century. Vegetational composition remained stable from then until the early 20" century. 20™ CENTURY VEGETATION From about 1200 A.D. to 1930 A.D., vegetation at all four sites was characteristic of sloughs. After 1930, however, shallower water conditions are indicated at sites 2, 3, and 4 by the change to sawgrass marshes with abundant weedy annuals. Although shallower wa- ter depths are suggestive of drier conditions, precipi- tation levels were higher than the 20" century average during this time (Text-fig. 5), indicating that reduced water levels and drier marsh conditions at these sites resulted from hydrologic alteration of the system rather than climatic change. Hydrologic changes that were completed by 1930 include construction of the Hoover Dike on the south side of Lake Okeechobee and dredg- ing of major muck canals linking the lake to the At- lantic Ocean (Light and Dineen, 1994). Construction of the Hoover Dike prevented seasonal influx of water to the Everglades from overflow of the southern lake bank, a major source of water for sheet flow across the Everglades. Additionally, substantial areas of the Everglades were drained as the muck canals diverted much of the remaining sheet flow from the Everglades to the ocean. Additional changes occurred between 1950 and 1960. At site 1 in WCA 1, vegetation changed from sloughs to sawgrass marshes; at site 2 near the Hills- boro Canal in WCA 2A, cattail marshes began to dom- inate the vegetation after 1960. Both changes occurred after completion of the Water Conservation Areas and Everglades Agricultural Area (EAA), part of the C&SF Project. Construction of a levee on the western border of WCA | between 1954 and 1959 effectively stopped the remaining sheet flow across WCA | (Light BULLETIN 361 SITE 1 Depth cm 1950AD = ~1900AD = 1410-1470AD fj 30 40 1005 - 1180 AD I 50 60 405-575AD ff 70 0 10 0 0 10 20 30 0 0 10 20 30 40 50 60 PERCENT ABUNDANCE SITE 2 Post 1950 20 1900AD seo-960aD ff = 800 - 920 AD | 40 1oBc-90A0 ff 100 BC | 50 20 AD i 60 380 - 260 BC | 0 10 20 30 40 50 60 70 80 90 0 10 0 10 20 30 40 50 60 70 80 & 40 20 0 PERCENT ABUNDANCE Sawgrass Marsh Vbi V b2 0 01 SQUARED CHORD DISTANCE Slough Sawgrass Marsh - Slough Mosaic Slough Cattail Marsh Sawgrass Marsh Near Tree Island V b2 Vbi Slough oe 00102 Squared Chord Distance Sawgrass Marsh Near Tree Island Myrica Typha Asteraceae Cladium OE O Te 10 > Ierce © © 2 Fi > , Yl PD « t j 1 7 Text-figure 4.—Percent abundance of pollen of major plant groups at sites 1—4 in northern and central Everglades. SCD values show lowest squared chord distance values for modern analogs; SCD <0.15 are considered to be close analogs for fossil assemblages. Cluster designations refer to clusters designated in Text-figure 3 and Table 3. CLIMATIC AND ANTHROPOGENIC IMPACTS: WILLARD ET AL. SITE 3 e Re Soo xe S oe w RS S & se Radiometric Dat P ge oe adiometric Dates ¢ eS we s ~1960AD « \ ~1900AD =” 1425 - 1635 AD § 30 } 1005 - 1220AD E,, = 50 + 235-483 AD 60 0 1020 0 10 20 30 0 10 20 PERCENT ABUNDANCE SITE 4 ~1960AD = ~1900AD s 1295-1420AD J ~ = 40 65-240AD § ~ 780-405 BC | 0 10 20 0 10 PERCENT ABUNDANCE 0 10 20 30 f) 0 10 20 30 40 50 60 70 SQUARED CHORD DISTANCE | 0 QO 10 20 30 40 50 60 70 80 0 010 SQUARED CHORD DISTANCE Text-figure 4.—Continued. Va Vb1 V b2 Vb1 EeVic2me Vb1 ING Vb1 IV d1 Vb1 V b2 Ve V b2 Vb1 V b2 Vb1 Vb2 Vb1 Sawgrass Marsh Slough Sawgrass Marsh Near Tree Island Slough Sawgrass marsh Slough/Sawgrass marsh transition Slough Sawgrass Marsh Near Tree Island Slough Sawgrass Marsh Near Tree Island Slough E34 Myrica = Asteraceae Cladium 49 50 BULLETIN 361 1998 1995 1992 1989 1986 1983 1980 1977 1974 1971 1968 1965 1962 1959 1956 1953 1950 1947 1944 1941 1938 1935 1932 1929 1926 1923 1920 1917 1914 Wy 1908 1905 1901 1898 1895 120) 25 Isa Wee W4'o) 4s Annual Precipitation (cm) Year (A.D.) Text-figure 5—Annual rainfall (9 point smoothing) for Ever- glades, 1895-1998. Vertical line indicates 1895-1998 average. Based on precipitation data for Florida region 5 obtained from NOAA at http://www.ncdc.noaa.gov/onlineprod/drought/xmgr.html. and Dineen, 1994), and the reduced water depths re- corded in sediments from site 1 after 1960 illustrates the impact of that hydrologic change. The increased abundance of cattail pollen at site 2 after 1960 is cor- related with increased levels of phosphorus in both sediments and pore water from cores (Orem ef al., 1999). After 1960, agricultural activities in the EAA expanded rapidly: the subsequent increased phospho- rus concentrations and cattail abundance recorded in sediments at site 2 appears to be tied to greater nutrient runoff from the EAA after that time. VEGETATIONAL HISTORY: SOUTHERN EVERGLADES SITES PRE-20'! CENTURY VEGETATION The impact of climatic changes on hydrology and salinity in the southern Everglades is illustrated in four cores collected in Taylor Slough and near Florida Bay (Sites 5—8, Text-fig. 1). From about 0 A.D. to 1200 A.D., fresh-water marshes, analogous to sawgrass marshes and wet prairies found in the southern Ever- glades today, dominated the four sites (Text-figs. 6—9). Even at the southernmost site near Florida Bay (site 8), mollusc assemblages of this interval consist exclu- sively of terrestrial and fresh-water taxa (Text-fig. 9). The first occurrence of brackish mollusc and benthic foraminifer taxa there in the late 13" century coincides with a decreased abundance of pollen typical of fresh- water marshes. By the 16" century, vegetation at that site fluctuated between wet prairies and brackish marshes, indicating periodically shallower water and, possibly, salt-water intrusion. The last occurrence of terrestrial and fresh-water molluscs and algae was in the 17"-18" century, indicating minimal fresh-water influence after that time. Marsh vegetation persisted at this site until late 19" or early 20" century, when man- groves became the dominant element of the vegetation. Pollen assemblages from site 5, located in very thick peats in the central part of Taylor Slough, indicate changes from sloughs and deep-water conditions to wet prairies/sawgrass marshes with moderate water depths at about 2,800 yrBP (Text-fig. 6). Although sedimentation rates were very low at this site, little vegetational variation is recorded at this site from 2,800 yrBP until the 20" century. Sites 6 and 7 provide little data on vegetational trends prior to about 1300 A.D. because the basal age of the core at site 6 is about 1200 A.D. and because 5—10 cm thick intervals were analyzed for the lower 60 cm of the core collected at site 7. At site 6, pollen assemblages indicate fluctuat- ing hydrologic conditions from about 1300 A.D. to 1900 A.D., with vegetation ranging from wet prairies to brackish marshes to sawgrass marshes, sloughs, and mangroves (Text-fig. 7). Conditions appear to have been less variable at site 7 during that time (Text-fig. 8), although slower sedimentation rates decrease the time resolution possible in that interval. As seen at northern Everglades sites, Myrica abundance doubled in the 17" century, possibly indicating regionally drier conditions. From the 17" through 19" centuries, veg- etation at all four sites varied little. CLIMATIC AND ANTHROPOGENIC IMPACTS: WILLARD ET AL. 51 SITES Radiometric Dates of ; ~ 1960 AD s (4) ~1900AD 8 << 10 20 465-645AD g ~ 40 } 780-405BC § 60 | 70 | 1975-1760BC § 0 10 20 0 10 20 30 40 50 60 70 80 0 10 PERCENT ABUNDANCE Rou 3 we x & Cua ee con w Ny s > a es & o” o IV d1 IV d2 Wet Prairies/ Ivd1 Sparse Sawgrass Marshes | vil Sloughs | | j ! 10 20 30 0 10 20 0 0 0.10 — Myrica SQUARED CHORD DISTANCE Asteraceae [7] Sagittaria Text-figure 6.—Percent abundance of pollen of major plant groups at site 5, central Taylor Slough. SCD values show lowest squared chord distance values for modern analogs; SCD <0.15 are considered to be close analogs for fossil assemblages. Cluster designations refer to clusters designated in Text-figure 3 and Table 3. 20TH CENTURY VEGETATION Vegetation at the southernmost site (site 8) changed little throughout the 20" century, because present sa- linity levels and vegetational composition apparently were established by late in the 18" century. Site 7, collected farther north in dwarf mangrove scrub, changed from fresh-water marshes to mangrove as- semblages in the early to mid-20" century. This change probably reflects the combined effects of nat- ural sea-level rise and reduced fresh-water flow from the Everglades. Additional evidence for hydrologic changes along Taylor Creek is provided by examina- tion of aerial photographs taken between 1940 and 1994. These photographs show infilling of a lake along Taylor Creek, reducing its area by about half and in- filling parts of the coastal zone west of the Taylor Creek mouth (Schaffranek er al., 2001). In Taylor Slough, vegetation at both sites 5 and 6 changed after 1930. At site 5, pollen of asters and sedges increased greatly, which is suggestive of greater disturbance, fluctuating water levels, and/or drier con- ditions. At site 6, mangrove abundance decreased by 1960, and marsh pollen (Cladium, other Cyperaceae, Poaceae, and Typha) increased to abundances unprec- edented in the past 2,000 years. This shift to sawgrass marshes may reflect the influence of construction of the C-111 canal and South Dade Conveyance System in the early 1960s; management of these control struc- tures ensures minimum monthly deliveries of water to Taylor Slough (Light and Dineen, 1994), possibly pro- viding more annually constant hydrology, deeper wa- ter, and longer hydroperiods than occurred naturally at this site. DISCUSSION Over most of the last two millennia, water depths in much of the Everglades appear to have been deeper than today with longer hydroperiods. In the Ridge and Slough, the presence of slough vegetation between 0 A.D. and 800 A.D. and between 1200 A.D. and 1600 A.D. indicates the long-term existence of deep water and long hydroperiods. In Taylor Slough and sites near Florida Bay, the presence of wet prairie and sparse sawgrass marsh vegetation prior to 1200 A.D. indi- Nn bo SITE 6 Radiometric PS Ay Dates &* ~1960 AD # 10- 20 £ ~1900AD #8 1475 - 1665 AD § 1455 - 1665 AD 8 50 1305 - 1460 AD § © = 0 20 40 60 80 PERCENT ABUNDANCE BULLETIN 361 2 Re) Rs & we we se S ” oe IVdt IV d2 Wet Prairies Tb WV d2 Wet Prairies with Dwarf Mangroves IV d2 Brackish Marshes Ww V b2 Sawgrass Marshes Near Tree Islands Ve Cattail Marshes Brackish Marshes m Southwest Florida Mangrove Forests wee Dwarf Mangroves Vb1 IV dt Wet Prairies SQUARED CHORD : DISTANCE ES) myrica EE] Asteraceae Eq Wha Text-figure 7—Percent abundance of pollen of major plant groups at site 6, southern Taylor Slough. SCD values show lowest squared chord distance values for modern analogs: SCD <0.15 are considered to be close analogs for fossil assemblages. Cluster designations refer to clusters designated in Text-figure 3 and Table 3. cates fresh-water conditions and short to moderate hy- droperiods. These long-term differences in hydrologic regimes between northern and southern sites is reflect- ed in the present vegetational distribution and substrate type and probably reflects underlying geologic con- trols, including differences in the underlying lime- stone. Northern sites are underlain by the Fort Thomp- son Formation, which consists of a series of alternating freshwater and marine limestones. Southern sites are underlain by the Miami Limestone, consisting of an upper, oolitic limestone overlying a bryozoan facies (Gleason and Stone, 1994). The impact of climate variability on Everglades vegetation and hydrology is indicated in sediments de- posited between the 9" to 13" centuries. During this time, water was shallower at most Ridge and Slough sites, with the greater abundance of weedy annuals suggesting rapid drying or prolonged droughts. Near Florida Bay, salinity increased at this time. Also during this interval, known as the Medieval Warm Period (MWP) (9" to 14" centuries) (Hughes and Diaz, 1994), prolonged droughts have been documented in Haiti, Mexico, and North Carolina, as have lower lake levels in Mexico, and increased fire frequency in Costa Rica (Hodell et al., 1995; Horn and Sanford, 1992; Metcalfe and Hales, 1990; Stahle er al., 1988). Although slow sedimentation rates at Everglades sites preclude de- tailed temporal analysis of vegetational patterns throughout this interval, the evidence for drier condi- tions is consistent with a broader regional pattern of warmer, drier conditions during the MWP. Our data also indicate slightly drier terrestrial con- ditions in the 16" through 19" centuries. Although sed- imentation rates in these cores do not allow detailed analysis of this interval, the broad patterns shown dur- ing the interval known as the Little Ice Age (LIA) (1550-1850 A.D.) (Bradley and Jones, 1993) are con- sistent with records of 65!°O from coral skeletons in Biscayne Bay indicating drier conditions in the 18" and 19" centuries (Swart et al., 1996). Sea-surface temperatures 1°C cooler than today also are indicated by 6'8O data from corals and foraminifers in the Flor- ida Straits and Sargasso Sea for the late part of the LIA (Druffel, 1982; Keigwin, 1996). Cooling of Gulf surface temperatures in climate models is correlated with lower precipitation levels (Overpeck ef al., 1989), which is consistent with drying trends shown by LIA pollen records from the Everglades. CLIMATIC AND ANTHROPOGENIC IMPACTS: WILLARD ET AL. 5/3) SIME? SF s ss 2) 2) Radiometric Dates O “ ~1960AD = ~1900 AD = 1680-1760 AD | 30 40 60 70 280-400 AD so = 90 £ 0 10 20 30 40 50 60 70 80 90 0 10 0 10 20 30 40 PERCENT ABUNDANCE 2 & os ys s e AS * 3@ Pa &” & Vc Wd2 Ve Dwart Mangroves IV d2 Va Brackish and i Freshwater Marshes Va IV d1 IV d2 Va Wet Prairies/ Sparse Sawgrass Marshes IV di 0 10 20 30 40 50 0 0 10 20° SQUARED CHORD ES Myrica DISTANCE E-] Asteraceae Text-figure 8.—Percent abundance of pollen of major plant groups at site 7, Taylor Creek. SCD values show lowest squared chord distance values for modern analogs; SCD - 2 2 designated in Text-figure 3 and Table 3. The advent and evolution of water-control practices in south Florida has resulted in unprecedented changes in vegetational distribution. The greatest and most re- gional impacts were seen by 1930, when shallower water and shorter hydroperiods are documented in most Everglades cores. These drier conditions oc- curred at a time of higher than average precipitation, indicating that vegetational and hydrologic changes re- sulted from hydrologic changes to the system. The combined effects of reduced sheet flow due to water diversion through canals and disrupted seasonal water supply due to construction of the Hoover Dike were sufficient to shift the Ridge and Slough ecosystem from a deep-water slough to a sawgrass marsh with abundant weedy annuals. At both sites in Taylor Slough, weedy species also increased in abundance, although the impact on water depths is less clear. In contrast, alterations associated with construction of the Central & South Florida (C & SF) Project in the 1950s and 1960s appear to have had more localized impacts on marsh vegetation. Some sites underwent striking changes after 1960, such as expansion of cattail marsh- 0.15 are considered to be close analogs for fossil assemblages. Cluster designations refer to clusters es at nutrient-enriched sites, whereas other sites saw minimal change. These observations are particularly relevant in light of suggestions that restoration goals for the Everglades be aimed at rainfall and runoff conditions that existed before the C&SF Project was completed in the early 1960s (Light and Dineen, 1994). Our data clearly in- dicate that the major alterations of the system occurred in the early 20" century, when construction of muck canals linking Lake Okeechobee to the Atlantic Ocean, the Hoover Dike along the southern shore of Lake Okeechobee. Thus, the early- to mid-20" century should not be construed as the “natural” state of the Everglades ecosystem. Rather, reconstructions of the early 19"-century Everglades provide a more realistic estimate of the “natural” state that our data indicate had persisted for the previous two to three centuries. These data also provide a model for how an undis- turbed wetland ecosystem responds to changing cli- matic conditions; data indicating drier conditions dur- ing the Medieval Warm Period are consistent with the predicted response of the Everglades wetland to pos- Nn L SITE 8 Radiometric Dates ~1960AD * "| -1900AD = 2 | 1570-1730AD g | 50 1120-1280AD F 70BC-70AD § | 10 0 10 20 30 a) 0 10 20 30 40 50 60 70 80 90 PERCENT ABUNDANCE BULLETIN 361 @ F S Ks & ¥ s & & eo S \V dt WV d2 [an Dwart Mangroves IV d2 ) ty Y) —— Wat Brackish Marshes H Vide and Wet Prairies ° ) e e dt ° e J e e We Wet Prairies/ ) Sparse Sawgrass Marshes dt E43 Myrica % 40 0 0 02 04 SQUARED CHORD F=) Asteraceae DISTANCE Text-figure 9.—Percent abundance of pollen of major plant groups at site 8, Mud Creek. SCD values show lowest squared chord distance values for modern analogs; SCD <0.15 are considered to be close analogs for fossil assemblages. Cluster designations refer to clusters designated in Text-figure 3 and Table 3. Ovals indicate presence of molluscs or foraminifers picked from sediments. Foraminifer presence also was noted when foraminifer linings (““microforams”’) were observed in palynological preparations. Fresh-water algal presence is based on presence of Ovoidites in palynological preparations. sible global warming over the next century (Watson et al., 1996). Additionally, the drier conditions indicated during parts of the Little Ice Age are consistent with climate model predictions of lower precipitation due to cooling of Gulf surface temperatures (Overpeck et al., 1989). A more difficult question to address confi- dently is the impact of future warming on an already disturbed ecosystem. Prior to compartmentalization of the marshes by canals and levees in the 20" century, it appears that broad-scale subenvironments of the Ev- erglades responded similarly to climatic fluctuations. Changes over the last century have altered water levels and the natural rhythm of seasonal hydroperiod fluc- tuations in the Everglades wetland, resulting in a land- scape characterized by localized fluctuations in hydro- period, disturbance, nutrient status, and salinity. The resulting ecological heterogeneity makes modeling predictions of system-wide changes due either to fu- ture climatic change or alterations in water-control practices much more problematic. REFERENCES CITED Bradley, R.S., and Jones, P.D. 1993. ‘Little Ice Age’ summer temperature variations: Their na- ture and relevance to Recent global warming trends. The Holocene, vol. 3, pp. 367-376. Davis, J.H., Jr. 1943. The Natural Features of Southern Florida. Geological Bul- letin No.25. Florida Dept. of Conservation, Tallahassee, FL, pp. 130-215 Davis, S.M. 1994. Phosphorus inputs and vegetation sensitivity in the Ev- erglades. in S.M. Davis, and J.C. Ogden, eds., Everglades: The Ecosystem and its Restoration. 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St. Lucie Press, Delray Beach, FL, pp. 47-84. Loveless, C.M. 1950. A study of the vegetation in the Florida Everglades. Ecol- ogy, vol. 40, pp. 1-9. Maher, L.J., Jr. 1981. Statistics for microfossil concentration measurements em- ploying samples spiked with marker grains. Review of Palaeobotany and Palynology, vol. 32, pp. 153-191. MeVoy, C.W., Park, W.A., and Obeysekera, J. 2001. Landscapes and hydrology of the Everglades, circa 1850: U.S. Geological Survey Open-file Report (in press). Metcalfe, S., and Hales, P. 1990. Holocene diatoms from a Mexican crater lake—La Pisci- na de Yuriria. Memoirs, California Academy of Science, vol. 17, pp. 501-515. NOAA CLIMVIS internet climate data site. 2000. — http://www.ncdc.noaa.gov/onlineprod/drought/xmgr.html Orem, W.H., Lerch, H.E., Bates, A.L., Boylan, A., and Corum, M. 1999. Nutrient geochemistry of the South Florida wetlands eco- system: sources, accumulation, and biogeochemical cy- cling. in S. Gerould and A. 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A 240-year stable oxygen and carbon isotopic record in a coral from south Florida: implications for the prediction of precipitation in southern Florida. Palaios, vol. 11, pp. 362-375. Talma, A.S., and Vogel, J.C. 1993. A simplified approach to calibrating C14 dates. Radio- carbon, vol. 35, pp. 317-322. Traverse, A. 1988. Paleopalynology. Unwin Hyman, Boston, 600 pp. Vogel, J.C., Fuls, A., Visser, E., and Becker, B. 1993. Pretoria calibration curve for short lived samples. Radio- carbon, vol. 35, pp. 73-86. Watson, R.T., Zinyowera, M.C., Moss, R.H., and Dokken, D.J. 1996. Impacts, Adaptations and Mitigation of Climate Change: Scientific-Technical Analyses. Cambridge University Press, New York. 878 pp. Willard, D.A., Weimer, L.M., and Riegel, W.L. 2001a. Pollen assemblages as paleoenvironmental proxies in the Florida Everglades. Review of Palaeobotany and Paly- nology, vol. 113, pp. 213-235. Willard, D.A., Holmes, C.W., Korvela, M., Mason, D., Murray, J.B., Orem, W.H., and Towles, T. 2001b. Paleoecological insights on fixed tree-island development in the Florida Everglades: I. Environmental controls. in F Sklar and A. van der Valk, eds., Tree Islands of the Everglades. Kluwer Publishers, Amsterdam (in press). L& ie Vokhio? lia aw ~ “wt 7 ein 2s _ - i coll eee { i ~ot iva _ J eh rid . ‘ se a6 _ ¢ #8 honey AOR = sl = = =~ ; x on ry A ne j , 4 a 7 Ti) : - ll v Lhd Pande _ : 7 ‘ , “4 a pie Mahaney e iré 7 nd % : a a” = load ¥ 7 i y 33% Jona) UPD k ee 2 Act oy Atte aml 4 . wv end ” » ig eal he —ith aime = ile ie >a. ‘ x . . i a lye | SVE = ‘ ’ he iL & a : ns wen » ee Vie sy 16 €& <4) seek wheat ~ ie & ,pe - tae riot ae | ee ee Sate a iad. Sh ae) be AP ; 2 Qete= 81) adi 64 00 16 ~ ld pat oo) le 4 ree a iw a Lee o! « avs, a4 = ie Sty Z te CHAPTER 5 HYDROLOGY, VEGETATION, AND CLIMATE CHANGE IN THE SOUTHERN EVERGLADES DURING THE HOLOCENE MARJORIE GREEN WINKLER!, PATRICIA R. SANFORD!, AND SAMANTHA W. KAPLAN? ‘Center for Climatic Research, Institute for Environmental Studies, University of Wisconsin—Madison, 1225 West Dayton Street, Madison, Wisconsin 53706 *Department of Geography and Center for Climatic Research, University of Wisconsin—Madison, 1225 West Dayton Street, Madison, Wisconsin 53706 ABSTRACT Paleoecological study of 18 AMS-dated sediment cores from the southern Everglades provides evidence of a shifting mosaic of biotic communities in the past similar to those on the Everglades landscape today. Our results also indicate initiation of Everglades peatlands at 5000 yr B.P., the importance of fire (from charcoal analysis) as a structuring agent in the tropical Everglades, evidence of past plant communities (/soetes marshes) not present in the modern landscape, and the introduction of exotic plants (Schinus, Casuarina, etc.) today. Past vegetation changes are documented by pollen and sclereid changes. Past water level changes are documented by plant community changes, diatom species and habitat changes, sponge spicule changes, and by intervals of peat (wet) or marl (dry) deposition in the sediment cores. Marl deposition dominates today at these sites in the southern Everglades, a long-term trend exacerbated by human impacts. The Everglades may become less complex in the near future as introduced plants outcompete native vegetation and decreased water levels result in decreased peat production. A rewatering plan must include both wet and dry seasonal cycles in order to preserve the shifting mosaic nature of the landscape and to maintain the Everglades as a functional habitat for both plants and animals. INTRODUCTION The Everglades is an unique subtropical and tropical hydroecologic region found at the southern end of the Florida peninsula below latitude 28°N. Sheetflow from the Kissimmee-Okeechobee drainage maintains the di- verse biotic communities in the Everglades as it flows through marshes, hammocks, sloughs, and swamps to the ocean. Human activities in the past 100 years have decreased flow of water critical to the health of the natural Everglades. As South Florida population 1n- creases in coming years, pressure to divert more water and drain more land for development will increase. Recently Congress increased federal and local funding for a large-scale Everglades restoration effort. Con- flicting demands from developers, landowners, and preservationists make restoration decisions by federal and state agencies charged with water and environment management extremely difficult. To make informed choices managers need to under- stand the evolution of the Everglades landscape. Only paleoecologic analyses can provide an understanding of the processes which made the Everglades. Previous paleoecologic studies of the region (Riegel, 1965; Nichols, 1974; Gleason and Spackman, 1974; Gleason and Stone, 1994) were concentrated in the coastal southwestern or northern (the Water Conservation Ar- eas, WCA) sections of the historical Everglades. We undertook paleoecological analysis of 38 sediment cores (Text-fig. 1) from 17 sites in the southern section of the Everglades concentrating on Everglades Nation- al Park (ENP) and the southern parts of WCA3 to Ty © 4800 ] Everglades hs /\\ Basal Ages Nan 4590 | | Core Sites = 235 Poi. au | Miles K— Dass ~Y Q 1 20 \ 6 = 2% 32 |3055\\ ©2000; Kilometers oor 061445 "4 3460 | | ll - | A lente mae a ———— lf Le7Ag/ t \f 3500 @/ (\ sd { Vf, \ \(e ims a Y/, TN] 4 lease i) y, | =Sra es y tN 4350 04990 | asi es F ons ine SSS | | ) @ 23) \ ‘f | { #2840 | (| y epee? \ \ \/ // Biscayne eae i \ / -/ Biscayne | i | 7 f Bay 1 f | ve \ Bay al Nc ae | (Gwar | Rocky Glade | |eCastellow Hamnmock | |e 4000 { \ } ee OES Kyeress Dome eGumbs Limbo Trail @cii e Ever 6 / |9Mile Pond * Craighead Pi Pond’ N Try) as Paurotis ards e yer Florida Bay Pe 25° v4 LY ie 2290 @Lignum Vitae Key ee A Text-figure |.—a and b. Map of coring sites for this study in the southern Everglades (a). Distribution of basal organic sediment ra- diocarbon ages for cores in the southern Everglades (b). Filled cir- cles denote sites in this study and are all AMS dates. Open circles show basal ages from studies cited in text and are all conventional bulk radiocarbon dates. All ages are expressed in radiocarbon years before present (1950 A. D.) (yr B. P.). L67A L67C Large diam 0=60 cm Depth Ocm 5 d modern /-31 40 10 15 | modern /-31 40 fa 1790+ 30 /-26 67 20 500+ 40 /-25.50 25 58 BULLETIN 361 C111 Canal C111 Canal P-core 1 Hiller 4 0=40 cm Ocm g 20 40 710 +55 /-25.23 100 550+40/-26 18 120 140 160 H3010+50/-25 71 180 Ey limestone peat algal floc gyttja silt clay marl Daee peaty marl ®@@ shells organic marl i] unsampled marly peat sandy marl charcoal-stained marl Text-figure 2.—Sediment stratigraphies of cores obtained from Everglades sites. Radiocarbon dates and stable carbon isotope values (6'C) are to the right of each sediment core. Water depth is represented by 0 = # at the top of each stratigraphic column. provide a chronology for the development of the Ev- erglades and to compare the past vegetation and hy- drology with that of the modern landscape. ACKNOWLEDGMENTS We thank the many people at both Everglades Na- tional Park South Florida Natural Resources Center and at the Center for Climatic Research (CCR) who helped facilitate this study. The field work was aided by D. McJunkin, R. S. Webb, P. Killoran, J. Stott, S. S. Winkler, W. Loftus, W. Robertson, R. Rehrer, and M. Nesbitt. AMS-radiocarbon dates were run at the AMS-facilities at Woods Hole Oceanographic Institute and Lawrence Livermore Laboratory. I. Treichel, Uni- versity of Wisconsin Chemistry Department ran the samples for mass spectrometry. The Fairchild Tropical Garden, Miami, Florida, allowed access to their her- barium. This study was funded by NPS grant agree- ment #CA 5280—2—9010 from Everglades National Park to M. G. Winkler and by NSF grants ATM- 9101919 (COHMAP), ATM-9510668 (TEMPO), ATM-9318973 (Interdisciplinary Research Program in Climatology) to J. E. Kutzbach at CCR, University of Wisconsin—Madison. The stable carbon isotope mea- surements were partially supported by NIH Grant GM18939 to W. W. Cleland, Dept. of Biochemistry, UW-Madison. AMS Radiocarbon dates from the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) facility at Woods Hole Oceanographic Institute were partially funded by NSF cooperative agreement OCE801015. This is CCR Contribution No. 757. METHODS Cores were taken with the Hiller corer, hand-driven polycarbonate tubes, freeze corer, or modified Living- ston piston-corer as field conditions, transport consid- erations, and/or sediment type dictated. All sites were cored to bedrock except for Gator Lake, a deep sink- hole lake, although at some sites (Rocky Glades and C111) coring was discontinuous (Text-fig. 2). Sedi- ments from all sites were analyzed by loss-of-weight- HYDROLOGY, VEGETATION, AND CLIMATE: WINKLER ET AL. 59 Ever 6 Craighead Pond Craighead Pond Castellow Lignum Vitae Small diam Hiller Hammock Hiller 2 0=35 cm 0=35 cm 0=7.5 cm 0=10 cm Depth Ocm 20 30 40 50 60 70 80 90 110 algal floc ==s| limestone gyttja peat silt marly peat clay marl 905+30 /-27 47 250+30/-25 00 algal floc peaty marl shells [al unsampled organic marl sandy marl charcoal-stained marl Text-figure 2.— Continued. on-ignition (LOI) (Berglund and Ralska-Jasiewiczowa, 1986) and high temperature LOI (HLOI) (Dean, 1974) to determine sediment composition (marl or peat). Fif- ty samples of basal and other organic sediments from the cores were radiocarbon-dated by Accelerator Mass Spectrometry (AMS) techniques. Sediment chemistry was obtained by Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) analysis run at the University of Wisconsin—Madison Extension Soil and Plant Analysis Laboratory (Schulte er al., 1987) to de- termine changes in the concentrations of atmospheri- cally- and locally-deposited elements and nutrients. Selected cores were analyzed for charcoal following the method of Winkler (1985); diatoms and other algae (Winkler, 1994a); pollen (Gray, 1965; Faegri and Iver- sen, 1975); and cladocera (Frey 1986). Sponge spic- ules and Nymphaea (white water lily) and Cladium (sawgrass) sclereids were counted during cladoceran and/or pollen counts (Winkler et al., 1996a). RESULTS AND DISCUSSION STRATIGRAPHY AND DATING The unique landscape that is the Everglades in southern Florida is one that presents dating and inter- pretive difficulties for the paleoecologist. The land- scape evolved from and is maintained by seasonal wa- ter-level extremes and frequent peat-consuming fires Charcoal is found at many levels in sediment cores (Cohen and Spackman, 1974; Duever ef al., 1985). Low water levels during drought, exacerbated by mod- ern drainage and canalization, expose ancient peats which are then destroyed by oxidation and decompo- sition (Shih, 1980; Duever er al., 1985; Snyder and Davidson, 1994). Dewatered peat is also loose and fri- able and can be scattered by winds or moved down- stream when water levels increase. In addition, gases from the decomposition of peat during low water lev- els weaken tree islands and permit storm-force winds to cause tree islands and chunks of hammock peat to break off and be transported downstream where they 60 BULLETIN 361 Rocky Glades Rocky Glades Paurotis H. Paurotis H. WCA 3B Hiller Frozen F Hiller Small diam Hiller 0=24 cm 4cm 0=0 cm 0=0 cm 0=37 cm Depth ocm Ocm Ocm 20 iG 10 20 310+ 40/-26 57 60 80 20 ay 100 30:/-25.a¢ 30 /-21.4¢ 120 30 60 140 160.) | AG 80 180. 134 B00 = 100 220 23.45 240 29 tao 260 140 280 70 300 +40/-18 09 160 320 a 180 90 ORES UG26-59) 200 4990+ 40 /-21 67 100 C 90 513 algal floc Erg limestone peaty marl ®@ shells id gyttja peat organic marl =| unsampled silt marly peat ee sandy marl = clay marl charcoal-stained marl Text-figure 2.— Continued. (Robertson, 1953; Gunderson and Snyder, 1994). become the locus of further peat accumulation thus confounding interpretation of the Everglades environ- ments. When there is marl in the sequence there is the possibility of hiatus in the record because transition to marl-forming conditions may involve sediment de- composition. In addition, when peat is subject to low water levels and/or fire there is also the possibility of hiatus in the record. Obtaining a continuous sedimen- tary record is not possible at many sites in the Ever- glades. In order to interpret this volatile region, many radiocarbon dates are required to determine the chro- nostratigraphic context at each site. Until a regional pattern is clear, intervals of interest in Everglades cores should be dated individually. Our goal was to date all HYDROLOGY, VEGETATION, AND CLIMATE: WINKLER ET AL. 61 A23 A06 Gator Lake Gator Lake Hiller Hiller Livingstone P-core 1 0=35 cm 0=30 cm 0=259m 0=25.9m Depth Ocr Ocmg : Ocm Ocm 5 00 20 100 40 10 : 40 200 x 900+60 80 0 1110+40 /-27 69 15 60 nee SO 26-307300 100 +30/-25.56 20 80 400 0 25 60 500 30 600 1950+45 50 2040 +80 35 40 45 50 “i }2840 +70 algal floc a limestone peaty marl shells = gyttja peat organic marl =a unsampled silt marly peat sandy marl =| clay marl charcoal-stained marl Text-figure 2.—Continued. basal sediments and bracket-date as many of the ob- vious sediment transitions in our cores as funds al- lowed. Additional dates will be obtained as studies on these cores continue. Text-figure 2 presents the sediment stratigraphy, ra- diocarbon dates, and stable carbon isotope values (64C) available for the sites. Sediment core depths ranged from 7 m of sediment at Gator Lake to 21 cm from a cypress dome. Alternations between peat and marl deposition are documented at several sites by sed- iment changes, LOI and carbonate analysis, and stable carbon isotope values. Peat deposition represents deep water-long hydroperiod, while marl deposition repre- sents low water level-short hydroperiod. We hypothe- size that temporal concurrence in hydrologic indicators suggests climatic forcing while local hydrological var- iability may be a result of topographical differences. Rocky Glades, L67C, Castellow Hammock and WCA 3B have basal ages between 5000 and 4000 years Before Present (yr B. P.) (Table 1). These early dates occur at the base of peat overlying bedrock and correspond to basal ages obtained in earlier studies (Gleason and Spackman, 1974; Gleason and Stone, 1994). Cores taken at sites L67A, C111 Canal, and A23 show organic sediments or peat overlying lime- stone bedrock with basal ages ranging from 3500 to 2500 yr B. P. A23 radiocarbon dates indicate that the bottom 30 cm of sediment accumulated rapidly. Sites BULLETIN 361 Table 1.—Radiocarbon dates (accelerator mass spectrometric [AMS] and conventional) and stable carbon isotope values (5'°C) for this study. CAMS dates are from Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory. OS dates are from Woods Hole National Ocean Sciences AMS facility. WIS dates are from University of Wisconsin—Madison Radiocarbon Dating Laboratory. 6'°C values of —25 A are assumed rather than measured values. Lab. ID Site Depth (cm) Material Date Le: CAMS-7483 A23 2.03.0 org. marl 1380 + 70 —25 A CAMS-7484 A23 5.09.0 charcoal-stained marl 1660 + 100 —25 A CAMS-7485 A23 9.0-12.0 marl 1890 + 70 — Psy IN CAMS-7486 A23 12.0-21.0 org. marl 2600 + 70 —25 A CAMS-7487 A23 21.0—25.0 org. marl 2840 + 80 —25 A CAMS-7529 A23 25.0-33.0 marl 2830 + 60 —25 A CAMS-7499 A23 41.0-S0.0 marl 2840 + 70 —25 A OS-3547 Rocky Glades, FF 101.6—-106.7 peat 1040 + 30 —=25:3 OS-3554 Rocky Glades, FF 116.8-121.9 marl 2370 + 30 —21.4 OS-3549 Rocky Glades, H2 195-200 org. carbon 1770) = 30 —21.34 OS-3753 Rocky Glades, H2 195-200 inorg. carbon 5270 + 45 —0.23 OS-3550 Rocky Glades, H3 232-242 wood 2900 + 50 —23.45 OS-3548 Rocky Glades, H1 295-300 gyttja 4880 + 40 —18.09 OS-3556 Lignumvitae 9.0-14.0 peat DOS) —25.44 OS-3557 Lignumvitae 20.0—25.0 peat 2502230) —26.85 OS-3558 Lignumvitae 50.0—60.0 peat 600 + 25 —24.72 OS-3559 Lignumvitae 75.0-79.5 org. carbon 1040 + 35 =P Py OS-3752 Lignumvitae 75.0-79.5 inorg. carbon 2610 + 40 +0.62 OS-3560 Lignumvitae 96-100 peat 2290) 250 =25 250) OS-3551 Castellow Hammock 61.0—62.3 wood 4000 + 30 = 7ze ils) OS-3561 A06, H3 57.0—60.5 peat 1960 + 30 —26.31 OS-3562 A06, H3 70.0-75.0 peat 2100 + 30 =25:56 OS-8203 A06, H3 20.0—25.0 peat modern —26:53 OS-3731 L67A, F 135) peat modern —31.4 OS-3732 L67A, L 22.5 marl 3500 + 40 =75)-5) OS-2746 L67C, P-core 2 5.5-6.5 peaty marl modern —25 A OS-3733 L67C, P-core 2 14.3-15.5 peat 1790 + 30 —26.97 OS-3734 L67C, P-core 2 25.3-26.5 wood 4350 + 35 —25.86 OS-3735 Paurotis Hammock, P-core 2 10.2-10.9 wood 310 + 40 —26.57 OS-3736 Paurotis Hammock, Hiller 75.0-87.0 peat 200 + 45 =26.59 OS-2742 Paurotis Hammock, Hiller 100-103 marl i170) == ©I0) =). 118) OS-3737 GU P=core! 1 10.6—11.7 peat TNO) == 35) = 25},313) OS-3738 C111, P-core 1 17.6-18.6 (top) peat 550 + 40 —26.18 OS-2739 C111, Hiller 4H 169-174 peat 3010 + 50 = 27/1 OS-3744 Gator Lake 93.0-95.6 gyttja 1110 + 40 —2 769) OS-3745 Gator Lake 190-191 gyttja 1010 + 50 PNT OS-3746 Gator Lake 660-68 | gyttja 1950 + 45 = ies) WIS-2338 Gator Lake 694-700 gyttja 2040 + 80 —27.67 OS-2745 Craighead Pond, P-core 22.8-23.8 peat 1500 + 30 20:59) OS-2744 Craighead Pond, P-core 36.0-37.5 peat w/ clay 2120 + 40 —24.92 OS-2743 Craighead Pond, Hiller | 74.0-79.0 peat 905 + 30 —27.47 OS-2741 Ever6, Hiller | 68.0—73.0 marl w/ peat 2560) 2335 —24.24 OS-2740 WCA 3B, Hiller 187-198 peat 4990 + 40 —21.67 at AO6, Craighead Pond, and Lignumvitae have basal ages between 2300 and 2100 yr B. P., although only Craighead Pond has peat at the base. Basal ages on the remaining cores fall between 1170 and 530 yr B. P. Paurotis Hammock core shows a transition from marl to peat at 310 yr B. P.,, possibly indicating the date of formation for this hammock. Sedimentation probably began at all of these sites in response to a rising water table. As noted below, our sequence of sediment cores would suggest at least four periods of long hydroper- iod. Marl deposition is observed at Rocky Glades and A23 between 2900 and 2800 yr B. P. and at Ever6 at 2560 yr B. P. Radiocarbon ages on basal portions of other marl deposits tend to cluster at about 1770 yr B. P., 1040 yr B. P,, and between 210 yr B. P. and the present. Data from these cores indicate that water levels rose high enough to allow sediment accumulation begin- ning about 5000 yr B.P. At all of these sites, except WCA 3B, basal sediments consisted of peat overlying bedrock. While WCA 3B has one of the earliest basal HYDROLOGY, VEGETATION, AND CLIMATE: WINKLER ET AL. 63 dates on peat (4990 + 40 yr B. P.), it overlies a marl deposit. The presence of marl under peat at WCA 3B suggests a chronological sequence similar to that of calcitic mud underlying peat in southern Lake Okee- chobee (Brooks 1974; Gleason and Stone, 1994) and the Corkscrew Swamp (Kropp, 1976)—deposits which have all been radiocarbon dated at ca. 6500 yr B. P. After the earliest peat deposition (SOOO—4000 yr B. P.) water levels continued to rise until c. 2900 yr B. P. when a number of sites show a transition to marl. The period from 2900—2300 yr B. P. is characterized by marl deposition. Gleason and Stone (1994) also re- port calcitic mud deposition at 2432 yr B. P. from Core 25 in south Water Conservation Area 3A west of Le- vee 67 and interpret hydroperiods to be short. How- ever, an increase in water levels or hydroperiod may have occurred locally between 2600 and 2500 yr B. P. as indicated by organic sediments at Ever6 and A23. Deposition of organics here when widespread marl de- position occurred over the rest of the Everglades in- dicates the mosaic landscape form persisting even dur- ing times of short hydroperiod. Craighead Pond, A06, and Lignumvitae show sed- iment beginning to accumulate over bedrock between 2290 and 2100 yr B. P. indicating a rise in water level or increase in hydroperiod. Gleason and Stone (1994) provide a radiocarbon age of 2036/2082 yr B.P. on peat in Core 25 and hypothesize wetter conditions dur- ing this period. A transition to peat deposition at AO6 about 1960 yr B.P. and to marl mixed with organic material (charcoal-stained marl) at A23 at 1890 yr B. P., as well as a peat layer deposited prior to 1790 yr B.P. at L67C, suggest water levels remained high for several hundred years. Marl deposition resumed at Rocky Glades at 1770 yr B. P. and at A23 at 1890 yr B. P. This drier period may have lasted until c. 1400 yr B. P. when organic deposition resumed at A23. Peat is also present prior to 1500 yr B. P. at Craighead Pond. Conditions were probably dry or variable between 1400 and 1000 yr B. P. as some sites show marl and others peat. Again the mosaic of contemporaneous wetter and drier habitats is demonstrated in the sedi- ment record. Between 1040 and 900 yr B. P. longer hydroperiods resumed and peat formation commenced at Craighead Pond and Rocky Glades. Hydroperiods remained long until about 550 yr B. P. as indicated by peat and organic sediment deposition at C111 and Lig- numvitae. Hydroperiods were again variable between 550 and 210 yr B. P. Paurotis Hammock and Lignumvitae re- veal peat formation, while the C111 canal site exhibits a change to marl. The uppermost portions of the ma- jority of cores have marl or algal deposits indicating shortened hydroperiods. These sediments are dated as modern at L67C, L67A, and AO06 or younger than 210 yr B. P. at Lignumvitae Key. SEDIMENT CHEMISTRY LOI and HLOI Analysis Text-figure 3 presents results from the LOI (% or- ganic matter) and HLOI (% carbonate) analyses for selected sites. The values given in the graphs are the direct measurements due to the LOI and HLOI ana- lytical procedures (Dean, 1974). The amount of or- ganic matter in the Everglades sediments varies from a mean close to 85% in Gator Lake (a value that re- mains quite stable throughout the 7 meter sediment column) to less than 4% in Ever6. The percent car- bonate also varies between 40% (at some time in the development of most sites) and less than 1% (at Gator Lake). At most sites the percent carbonate is greatest (approaching 40%) near the basal section of the cores, nearest to the limestone bedrock. 6'°C values of the carbonate (inorganic carbon) component of the sedi- ment (see Table 1, Rocky Glades, 195-200 cm and Lignum Vitae 2, 75—79.5 cm) are —0.23 and +0.62, respectively, close to 0 (marine HCO, ), demonstrat- ing the importance of the marine Miami and Key Lar- go limestones as the carbon source for much of the sediment deposition at these sites. Everglades peat, marly peat, and gyttja (lake sediments) are defined in our study terminology as sediments with more than 30% organic matter by LOI, while the Everglades marls in our cores contain a maximum of 30 to 40% carbonate by HLOI. Alternations between peat and marl are evident at 17 of the radiocarbon-dated cores including those from C-111, A06, A23, LV-2, Rocky Glades sinkhole site, L67C, Craighead Pond, and Pau- rotis Hammock. Ever6 and 9-Mile pond sites (Text- fig. 3) have elevated organic matter in the upper 15 cm, while WCA-3B (Text-fig. 3) has close to 90% or- ganic matter throughout most of the core. Higher % HLOI values in the top meter of the Gator Lake core (Text-fig. 3), suggest increased atmospheric deposition of dust and minerals from 20th Century land-use changes in the region. Charcoal Analysis Fire burns off peat deposits locally and lowers the ground surface which allows ponds to form (Loveless, 1959a; Gunderson and Loftus, 1993) thus contributing to the mosaic nature of the landscape and causing hi- atuses in the sediment record. A dramatic recent ex- ample of this destructive process occurred in spring of 1999 when wild and human-set accidental fires burned more than 20,000 ha of Everglades (Bragg, 1999). It may not be possible to find a complete paleohistorical 64 BULLETIN 361 Craighead Pond Craighead Pond Hiller P-Core % Loss of Weight % Loss of Weight 40 60 20 40 60 —— + 7.5-8.5 17.8-18.8 Depth (cm.) 22.8-23.8 28.9-29.9 33.9-35 Paurotis Hammock Paurotis Hammock Hiller P-Core % Loss of Weight % Loss of Weight 20 40 60 20 40 60 80 100 + + + +— f____+- _____} 8.2-9.2 10.9-11.9 13.9-14.1 87-89 17.1-18.4 89-100 100-103 20.8-22.0 Everglade 6 Castellow Hammock % Loss of Weight % Loss of Weight 40 60 80 40 60 3-4 15.9-16.9 24.5-25.5 35.4-36.3 44.3-45.4 53.4-54.4 57.7-58.8 Carbonate Text-figure 3.—Percent loss-on-ignition (LOI) and percent high temperature loss-on-ignition (HLOI) analyses for selected Everglades sedi- ment cores. LOI is a measure of organic carbon and HLOI measures sediment carbonate. HYDROLOGY, VEGETATION, AND CLIMATE: WINKLER ET AL. Gator Lake Gator L. P-Core 1 % Loss of Weight % Loss of Weight 20 40 20 40 60 80 51.2-52.2 61.2-62.2 73.5-74.7 86.5-87.6 A23 Hiller AO6 Hiller % Loss of Weight % Loss of Weight 20 40 60 80 100 40 60 80 + + C111 Canal C111 Canal Hiller-4 P-Core 1 % Loss of Weight % Loss of Weight 40 60 40 60 80 0-5 + + + 15-19 2.0-3.0 20-25 4.0-5.0 6.2-7.5 149-154 85-95 154-159 10.6-11.7 ISAS 13.2-14.4 164-169 15.4-16.4 169-174 17.6-18.6 Organic Carbon Carbonate Text-figure 3.—Continued. 66 Rocky Glades Hiller 175-180 195-200 232-237 247-252 270-275 280-285 290-295 300-310 0-8 25-33 50-58 75-83 100-108 116-125 150-156 167-171 175-187 198-200 0 % Loss of Weight 20 40 60 80 BULLETIN 361 Drives 2-4 L67A % Loss of Weight 20 40 60 80 + WCA 3B % Loss of Weight 40 60 80 Organic Carbon 10.2-15.2 30.5-35.6 50.8-55.9 71.1-76.2 91.4-96.5 111.8-116.8 0-1.5 3.9-4.4 5.5-6.5 88-98 12.0-13.3 14.3-15.5 16.8-18.0 20.8-21.8 22.8-23.8 25.3-26.5 Text-figure 3.—Continued. Rocky Glades FF % Loss of Weight 20 40 60 80 L67C P-Core 2 % Loss of Weight 20 40 60 80 + + Lignum Vitae Key % Loss of Weight 20 40 60 Carbonate 80 Depth (cm) 12-25 11.7-12.7 20.8-22.0 31.3-32.3 410-42 0 51.2-52.2 61.2-62 2 71.3-72.3 167-168 267-268 367-368 467-468 567-568 667-668 Text-figure 5.—Percent charcoal in Gator Lake sediments. ° HYDROLOGY, VEGETATION, AND CLIMATE: WINKLER ET AL. 67 Charcoal as % organic weight 0 10 50 | 1 0-7 7-145 14-207 20-257 25-327 32-397 39-4575 45-507 50-577 57-60.5 c0 5-044 64-70 70-75 Depth cm Charcoal as % dry weight Depth cm A23 Charcoal as % organic weight 0 20 40 60 80 100 > 1380 +/- 70 YBP 1660 +/-100 YBP 1890 +/- 70 YBP 2600 +/- 70 YBP 2840 +/- 70 YBP > 2830 +/- 60 YBP Ld 2840 +/- 70 YBP Charcoal as % dry weight —O— Charcoal as % dry weight Charcoal as % organic weight Text-figure 4—Charcoal analyses of AO6 and A23 presented as percent dry weight and as percent organic weight. Gator Lake Charcoal Percent Charcoal 100 record in any single Everglades peat deposit. Much of the dark organic matter in some cores is charcoal (A23, Text-fig. 4) and even in peat sections which ap- pear to be continuous, hiatuses occur. These findings dramatically underscore one of our conclusions: dating at close intervals is critical to understanding Ever- glades development. Charcoal analysis of contiguous samples from cores at AO6 and A23 (Text-fig. 4) showed that wildfires have been an agent of change on the Everglades land- scape for at least the last few millennia. High charcoal abundances are noted after about 1600 yr B. P. at both sites when drier plant communities are evident from the pollen assemblages. In diatom slides abundant charcoal was noted throughout 70—45 cm at the A06 site and from 33—12 cm and again in the 9—5 cm sam- ple interval at A23. Charcoal analysis of the Gator Lake sediments shows higher charcoal abundances in the upper 20 cm (Text-fig. 5). This may indicate an increase in regional land-clearing fires and/or atmospheric deposition of particles of soot from industrial growth in the region since the 1940’s. Fires used to burn off sugar cane growing areas in the Everglades Agricultural Area to the north of Gator Lake, may be one of the sources of increased charcoal in the recent sediments as well as a source of increased mercury (see Sediment Chem- 68 BULLETIN 361 istry below). Fires due to drought, however, have been documented in WCA-3, the region surrounding Gator Lake, as recently as 1971 (Goodrick, 1984) and prob- ably again in 1999 (Bragg, 1999). The charcoal evi- dence helps explain the presence of willow scrub sur- rounding Gator Lake as willow is known to colonize burned-over peat (Hofstetter, 1974; Olmstead and Loo- pe, 1984). The pollen analysis of Gator Lake sedi- ments (see below) suggests that willow was a recent addition to the vegetation near to Gator Lake. Mineral and Heavy Metal Analysis Total minerals and heavy metals in subsamples from Rocky Glades, C111, A06, A23, LV2, and Gator Lake were analyzed by ICP-OES (Table 2; Text-figs. 6 and 7). The results of these studies will be considered in- dividually below. When contrasting prehistoric and re- cent concentrations of most elements (Table 2b) we found that lead, zinc, copper, and arsenic increase in the surface sediments (upper I1—2 cm) at most sites. Even at the Lignumvitae LV2 site where past and pre- sent saltwater intrusion has confounded element changes, surface sediments are highly enriched with lead. Most lead is deposited to these remote places through the atmosphere or, in the Everglades, through waterflow as roads and other concrete highway struc- tures are washed by heavy summer rains and pollutants drain into surface waters. Lead in airboat fuels could also contribute to the metals pollution. Mercury is elevated in both fish scales and sedi- ments from recent levels of the Gator Lake core (Text- fig. 8). Mercury is used in the growing and processing of sugar cane in the Everglades Agricultural Area in the northern Everglades. Mercury has become a health problem for wildlife and humans in ENP (Loftus and Bass, 1992). The mineral and metals analyses show that even in the same drainage, sites such as AO6 and A23 (Table 2), can have different allochthonous inputs. Rocky Glades Total mineral (Text-fig. 6a) and heavy metal (Text- fig. 6b) analyses of top 128 cm of sediments from Rocky Glades provides evidence of elevated heavy metal concentrations above 45 cm. Samples analyzed below 110 cm (dated at about 1000 yr B. P.) have low- est heavy metals concentrations. Additional dates are needed to identify the cultural horizon in this core. The total mineral analysis (Text-fig. 6a) indicates peak ley- els of all minerals except calcium at 95 cm depth in the core, almost directly overlying the 1000 B. P. date. High sodium at this point suggests that saltwater in- trusion may have been the cause of elevated mineral concentrations. A similar, but smaller, peak occurs at 45 cm in the core, but is accompanied at this higher interval by elevated heavy metals. The surface sedi- ment has high concentrations of copper, zinc, manga- nese, arsenic, lead, and selenium (Text-fig. 6b). Cal- cium (Text-fig. 6a) is elevated in the bottom marl sed- iments of the frozen core (Text-fig. 2) and in the top surface sediment where LOI and HLOI analyses (Text- fig. 3) document marl deposition (decreased organic carbon and increased carbonate). Clll-core 4H ICP analyses of the top and bottom sediments of a 179 cm core from C111 (core 4H) (Text-figs. 7a and 7b) suggest that saltwater intrusion and agricultural runoff both affect the sedimentation in this region of the Everglades. A near basal date for C111 core 4H at 170 cm is about 3000 yr B. P. However, in these bot- tom sediments there are elevated metal and mineral levels which suggest that there may have been a salt- water intrusion, an hiatus in the peat and concentration of elements, or diagenesis and mixing at this site. Ca- nal construction may have also affected the stratigra- phy at this site although we moved away from the canal road and berm before coring. Calcitum and man- ganese peak in the marl sediments at 15—19 cm. depth and lead has near peak values in the top sediments (Text-fig. 7b). Boron, phosphorus, and copper, miner- als used in fertilizers (Hem, 1992) have high concen- trations in the top sediments. Sodium is elevated in the top sediments also suggesting possible saltwater intru- sion in this area. Gator Lake ICP total minerals were analyzed for two sediment samples, 3.6 and 681 cm, from Gator Lake (Table 2a). The 3.6 cm sample is from the modern sediments and the 680—681 cm sample has been AMS radiocarbon- dated at 1950 + 45 yr B. P. Similar to the results from C111 core 4H, boron and copper are elevated in the surface sediments of Gator Lake. These values suggest enrichment from agricultural practices in the region. A06, A23, and LV2 Surface and core bottom sediments were analyzed at AO6 and A23 sites for both total minerals and trace metals (Tables 2a and 2b). Percent N (% total nitrogen) was also analyzed for the top and bottom samples of the AO6 and A23 cores (Table 2a). Only trace metals were analyzed for LV2 (Table 2b). As at some of the other Everglades sites, phosphorus, boron, and copper, as well as nitrogen, are elevated in modern sediments at AO6 suggesting agricultural enrichment, while cal- cium and manganese are high in the modern marls of 69 HYDROLOGY, VEGETATION, AND CLIMATE: WINKLER ET AL. rol THT Pr co6 cle c6'b rO'SL 687 [98S 97'S Bes rS'l CSI 67 EO Lb 606 66'T Sb €08 66¢ 7869 9801 Sis orl CSI 67 LO'EP 60'6 66°C ais 9S TL re S6TS LL LL orl 9'LT Lr Lr Vol zeg pr OLLE ZG raids) 60'°9 Ip 97 OSI €t €0S 60'6 10°€ Ub PILI SCAG 66LL 716 90'€ Lr'l TST TLE OE bE Lv1 98'P LLY GOS +8 +06L LET cL9 SET Sl Ltt SO'9S 86'8 (bn GAG 80'0L SE 6LSL 16L L8'6 € C8 SILC 8'8L 801 LOE £89 LO IL GEG Ssh LL9 GUE SLI ssl €€T IP LZ Sv6 Soe tre 68S 8c LOS 19b crt 86r' I VLI kSG 10°67 86'6 6c ere 16°61 vT'T €90b S91 86r'l 19° r6S1 SL 07 LIS ces 769 9¢°9 L88b 98'S C8bT IL9€ 68LI or 786 = LOE OLte 86'E1 te) rs'S 6TLS 669 OISZ EL'LI 90'r1 GHG ETI sl 69'9 6'L PTE t0'r IL8E 88 GLSL b6'S ef Ol oll 6LI € 97 61ST 6E 17 pre $9'T GSH VAS prSr 6£ 9¢'1 69'1 676 ~—sSPL'SI LUS Lys SLY arr £069 €LTI 6£69I ZO" 7 SI IS] IL6 ~=r681 £901 19°€] 6c br 6'| Ga ler €18L 6T€ SO'r IW 2S sv uz qd IN ow uN a od nD ID oD el 97E 6969 b6'b SPT I ST€8 as) 6$9 OLLI res SOLSOI £981 I TOEE €60C 6€'b 9669 Corl LOOT SOT = POI Os6l Proce! 7 COI 61 €9Ib 18S SOL ITE ST IE aa 8E'8 Z6IE ITEl TELE cial Ve T EBL ISLE ~~ LOSE Ip8r $S'9T Or 69ST 9099 96£1 60007 7691 — € 167 Lr9E —-€9°8 psor 6895 F8'tl ¢St LEIP cEeeo £1691 8887 = Itl OL8I 79'8I 800r L061 TIE 90E O£6S L908 OLIFI 9881 N UN IV nD ad uN d uz Ss 3IN Le) M wm Ap uidd 980 c80 c8'0 Saale c8'0 cell c8'0 86°0 £80 60 6c € 61 ro 0 99°T 189 18-08 “L “"PoOwD CT cor T8-O08 “¢ "POD +1 C8e 16-06 “‘F “POD cI 067 06-S8 “€ “POD Tl O81 18-08 CG “PHOrD II QOL | a100-d = quoiey OI less | at0o-d = quojyey 6 Taec | at0o-d yioyweyH g 9¢ ] o100-d qaowey 1 96 GeO tz CAT 9 6 6-0 ‘I TAT S os ¢¢-0¢ ‘tH 90V L L-0 ‘IH 90V £ IZ 1@-TI ‘TH €tW T @ Z as09-d €TtV I siskjeuy qOl—SIPIW 21, IZ IZ-TI ‘1H ETV ST I | a109-d €TW 9T os $7-0T ‘TH 90V FT L L-0 ‘IH 90V €T 189 18-08 “ZL “HOD gI 9¢ | aoo-d qiowey LI yidaq aA aus (wo) siskjeuy qO[—S]|P1ouly [PIOL qm Aap wid ut uaatd aie suonesUadUOD “Wd [89g 0} WHO g'¢ WO’ Saydues aye] 10IVH J0J puv ‘TAT ‘9OV “CTY Wor sajdues Woo pur do} J0OF stIsAjeUY s[PIe 9PIL SHO -dOl QM Aap (uoypru tad syed) widd ur uaars are suoneussuo0d “¢7Ty Pure ‘QOY ‘Aye Joy wos saydwes woyog pue do} 10} sisAjeuy s[esoulP [PIOL SHO-dOl “RP —T AIGRL 70 Y GLADES, Everglades National Park ICP Total Mineral Analyses, 1993 core & cs (e Ss s Z S & Se BULLETIN 361 SS, ty S Depth (cm) 2370 + 30] 2 —SeasS —— 1040 + 30] 4 | 1 } TVTTTT [TT | 7 yj 1 r = = 500 1000 1500 100 200 4000 6000 500 1000 1500’ 200 400 w So S nm 2000 Depth (cm) 754 =| 804 854 90-4 954 100 4 1054 1040 + 30] 105 1154 TITTLE T + 1 T + 1 100 200 300 50 100 150 200 400 600 200 400 600 800° 500 1000 ~=1500 ppm Text-figure 6.—a and b. ICP-OES Total Mineral Analyses of the top 130 cm of Rocky Glades FF core (a). ICP-OES Heavy Metal Analyses of the top 130 cm of Rocky Glades (ENP) sediments from same core (b). Minerals and metals concentrations are given in ppm. A23 p-core 1. Lead, zinc, and arsenic are elevated in the surface sediments of A23 p-core 2 (Table 2b), while copper, lead, zinc, arsenic, and selenium are high in the surface sediments of A06. LV2 has elevated lead, lithium, and manganese in the surface sediments. Abundant marine diatoms in the LV2 surface sedi- ments indicate frequent saltwater inundation of this mangrove-fringed coastal pond. 71 AL. ’, VEGETATION, AND CLIMATE: WINKLER ET i HyYDROLOC National Park Fyerglades vergiad f TPT rz r pil l = oe | pea eal | Pa | ai | eee ET es | od pop eae ss es | ey ee ee I) ere at at Sel moonmnownwnoaonc;9qonononnonrwnaone79eru owownmnnsao -NN MOM AD TST MNONMWOWOMm~Mm™~ DW DWADWOCC — NN 32) & i | } a ra lela L i | | ae mE Eta (ise | in E =, 1000 1500 2000' 50 100 1 Hi, 500 | | = rosa US) a ea Fe es Fo fd a MOMONONOHNONONHNON OH OHNOHOHNONS SFRPANA*TTDN DORK DAARADAGO-—--—-ANM Text-figure 6.—Continued. 72 BULLETIN 361 ——- = — — — L = m) Depth (« —— | ak _———_ = ; = : ; ——— ; : 00 1000 1500 100 200 300° 1000 2000 3000 100 200 300° 20 & d ppm és os < Ae) y S 7 LO): R & oe i= — eS = IK ————d | == => , | | | | e 5 2s a S (=) SSS oa 3010 + 508 = __ : 1 tenaq ht T T Te 1 a “al Tose "ont T 7 T T Tr il 40 60 100 200 300 400 20° 100 200 300 400 500 100 200 300 400 ppm Text figure 7—a and b. ICP-OES Total Mineral (a) and Heavy Metal Analyses (b) of the top 25 cm and the bottom 25 cm (155-180 cm) from sediment cores from C-111, ENP. Minerals and metals concentrations are given in ppm. 3010 + 509 3010 + 50§ C11 ICP Depth (cm) Depth (cm) Heavy Metals Analyses, 1993 core 4H ee) So nn & OO BDNONGHGS an HYDROLOGY, VEGETATION, AND CLIMATE: WINKLER ET AL. Everglades National Park Text-figure 7.—Continued. 73 ppm 74 BULLETIN 361 Percent ug/g Hg dry weight io} 0.S 0 100} 1 Age Model Stratigraphy Core Description 4 ‘t = nN o +- before European settlement E Ss ° + 230 30 | 8 c £404, 40+ a fa sot so + 60 | 60 70 44 70 8044 * 80 + Hy g x so} 3 8 90+ om BS 2 100-4 +99+— Homogeneous soupy $4 and fibrous olive- @ brown peat. Flocculent sediment 0-6.6 cm becoming slightly more fibrous and consolidated Es He Be g 2 # 4g with depth. Text-figure 8.—Mercury concentrations in Gator Lake sediments (p-core 1) and in fish scales found at the same depth in the sediments (modified from Jensen, 1994). Sediment Stable Carbon Isotope Analysis Charcoal isolated from the sediments of the A23H core was used for stable carbon isotope analyses (Table 3). The charcoal is considered to represent air- or wa- ter-borne upland carbon at most sites (Winkler, 1994b), but in the Everglades, charcoal may also come from the direct burning of peat at the site during drought. Stable carbon isotope values (6'C) higher than —23 signal a proportional contribution of carbon from C-4 plants (such as Muhlenbergia and other drought-tol- erant plants) in the region. The highest values in the A23H sequence (6'°C —21.04) are found from 9-12 cm when marl was being deposited at the site (Text- fig. 2). This result suggests an expansion of arid C-4 vegetation in the region, perhaps Muhlenbergia grass prairies, before about 1890 + 70 yr B. P. and indicates that this vegetation association (which contains com- paratively little biomass) burned frequently and con- tributed windborne charcoal to the sediment at A23H. Other 85'°C results accompany the radiocarbon-dated samples. These values (Table 1; Text-fig. 2) are from analysis of whole sediment organic carbon which in- cludes carbon from both upland and wetland sources. Table 3.—6'°C-Stable carbon isotope values for six A23H sedi- ment samples. Analysis was performed on charcoal fraction isolated from the sediments at each depth. Depth (cm) GAS 5-9 —23.48 9-12 —21.04 12-21 —24.01 21-25 Dep, 25-33 252i 41-50 —23.00 Highest values on organic carbon (values above 6°C —21) are found at the bottom of the WCA 3B core (4990 yr B. P.) influenced by the underlying marls, or in the Rocky Glades sediments before 4800 yr B. P. and from about 2500 to 1900 yr B.P., times when other sediment analyses also indicate drought. In the two cases where separate samples of inorgan- ic carbon and organic carbon were analyzed (Rocky Glades 195—200 cm and Lignumvitae LV-2, Dr. 4, 75— 79.5 cm), the 6'°C values of inorganic carbon docu- ment dissolution of underlying marine coral (64°C —0.23 and +0.62, respectively, close to marine lime- stone 85°C of 0.0), rather than modern atmospheric CO, (68°C —7.0), as the carbon source for marl-form- ing organisms. This is an interesting result in light of recent increases in atmospheric CO, and the need to identify carbon sources and sinks in the global carbon cycle. Additional stable carbon isotope sequences would aid interpretation of vegetation community change data from pollen. BIOLOGICAL INDICATORS Diatom Analysis Diatom associations integrate environmental factors such as water chemistry, water temperature, water depth, and aquatic macrophyte presence or absence by their speciation, distribution, and abundance. Accu- mulation of diatom frustules in lake or peat sediments represents the response of the biota at various time scales. Seasonal and microhabitat variations are smoothed at medium frequency sampling intervals. Diatoms respond relatively rapidly to environmental changes such as pH and salinity gradients, and to changes in nutrient availability, water levels, and tem- HYDROLOGY, VEGETATION, AND CLIMATE: WINKLER ET AL. 15 perature (Hustedt, 1939; Patrick and Reimer, 1966; Bradbury, 1975; Patrick, 1977; Gasse, 1980; Diger- feldt et al., 1980; Rasanen and Tolonen, 1983; Charles, 1985; Charles et al., 1986; Smol et al., 1986; Winkler, 1988; Whitmore, 1989; Sweets et al., 1989; Fritz, 1990; Sweets er al., 1990; Blinn, 1993; Dixit er al., 1993). Therefore, diatoms can be used to reconstruct the environmental history of lakes and wetlands and to delineate the biotic response to modern trophic and chemical conditions caused by land use and other changes. Correlation of chemical variables, morpho- metric factors, disturbance indicators, and diatom per- centages, enables separation of some of the factors af- fecting the diatom distribution within lakes (Winkler, 1988). Diatoms were identified using floras compiled by Hustedt (1930, 1939, 1955), Huber-Pestalozzi (1942), Patrick and Reimer (1966, 1975), Pergallo and Per- gallo (1965), Koppen (1975, 1978), Florin (1980), Fo- ged (1980, 1984), Gasse (1980), Germain (1981), Hak- ansson and Locker (1981), Gasse et al., (1983), Gasse and Tekaia (1983); Haworth (1983), Bateman and Rushforth (1984), Camburn et al. (1984—1986), Hak- ansson and Stoermer (1984), Stoermer and Hakansson (1984), Krammer and Lange-Bertalot (1985, 1986, 1988, 1991a,b), Camburn and Kingston (1986), Hak- ansson (1986a,b), Dodd (1987), Klee and Schmidt (1987), Kling and Hakansson (1988), and Scherer (1988). Diatoms have been analyzed at four sites, Gator Lake, A23H, AOQ6, and LV2. Each site will be dis- cussed individually below, while the Diatom Discus- sion section will include consideration of results from all of the sites. Gator Lake Diatom analysis of the Gator Lake sediments (Text- fig. 9) reveals two zones devoid of diatoms: before 1900 yr B. P. (before 650 cm) and after about 1600 yr B. P. (above 450 cm). The interval between 1900 and 1600 yr B.P. has abundant acid to circumneutral planktonic diatoms dominated by Aulacoseira ambi- gua and other Aulacoseira species, including a large number of diatoms which may be a new species of Aulacoseira (Plate 1, figs. 1 and 2). This zone of deep- er water, as indicated by the planktonic diatoms, is concurrent with one described below at sites in the Northeast Shark River Slough and may indicate a change in the regional hydrology at that time. A di- verse assemblage of littoral diatoms including Eunotia, Navicula, and Neidium, and other algae (Pediastrum and desmids) are also present during this wet time be- tween 650 and 450 cm. At Gator Lake, the intervals with sparse diatoms are the only ones with abundant sponge spicules (Pl. 1,3 and 4), as well as abundant rhizopod amoeba tests, chrysophyte cysts, Nymphaceae sclereids (Pl. 1,6), fungal spores, and pyrite framboids. The few diatoms in the surface sediment sample suggest an increase in taxa such as Aulacoseira granulata and varieties, and Rhizosolenia resting spores. These species dwell in more alkaline and more nutrient-rich water than dia- tom species found in the lower levels of the core. A23H The diatom assemblage at the A23H site (Text-fig. 10) in Northeast Shark River Slough indicates that al- kaline littoral (shallow water), epiphytic (plant cling- ing) species such as Mastogloia smithii v lacustris, An- omoneis vitrea, Cymbella microcephala have domi- nated since 2840 + 70 yr B. P. However, for the period after 2600 (?2000) to 1660 yr B.P, circumneutral planktonic diatoms (Cyclotella, Aulacoseira ambigua, Tabellaria flocculosa v linearis) appeared and made up more than 10% of the diatom sum. These plank- tonic species indicate deeper water at that time. The chronology of this deepwater event is concurrent with the interval of abundant planktonic diatoms at Gator Lake dated from 1900 to 1600 yr B. P., suggesting hy- drologic changes across the southern Everglades. The inverse relationship of sponge spicule/diatom presence or absence found in Gator Lake sediments, does not hold true at A23H site. Sponge spicules at this site are present only sporadically in intervals when diatoms are abundant. Diatoms are very sparse in the marly peat below 2600 yr B. P. A06 Diatoms are relatively sparse throughout the A06 core and, although entire slides were examined, the highest diatom sum for any level at this site was 156 frustules. The diatom assemblage at the A06 site (Text- fig. 11) in Northeast Shark Slough is dominated main- ly by ephiphytic alkaliphilic/alkalibiont diatoms from the genera Mastogloia, Amphora, Cymbella, and Na- vicula. However, the basal levels of the core contain epiphytic Gomphonema spp. and evidence of alkali- philic planktonic species including Asterionella, Ste- pPhanodiscus, Synedra, and benthic Surirella spp. sug- gesting slightly deeper water after about 2100 yr B. P. Planktonic/benthic diatoms (small Fragilaria spp.) are present above 55 cm in the core, but are the dominant taxa only when other diatoms are scarce. At A06 sponge spicules and chrysophyte cysts are most abun- dant in the top 30 cm of the sediment, the time when diatoms are also most numerous. The number of lit- toral diatoms increases in the AO06 top sediments with much of this increase due to circumneutral Eunotia 76 BULLETIN 361 Ls n -—f + ie 9 a | | Joell Lae | i} | | | | | | par = | | | Ey | | | ae : = 2000 3 at TOM PERCENTAGE ~ \ \ \ | | 440 | 44 j | | 7 | ‘Aaa / | Abundant =n 40 A | / | / | | / Test | | 13 5 + t4 | Sparse di l= 1950 + 45 2 = 2040 +8 DIATOM PERCENTAGE Text-figure 9.—Gator Lake Diatom Percentage Diagram. Solid curves represent actual percentages. Stippled marking represents 10 ex- aggeration. Radiocarbon dates are placed to the right of the diagram. HYDROLOGY, VEGETATION, AND CLIMATE: WINKLER ET AL. WI site { Je vi f 4 t | | |-16 10 | 4 | Sao cellll rs Jy] 354 i} | 455 | zalll| ya 840 + t 70 ( TOM PERCENTAGE 17 5 36 A mall | = ; | 97 | 24 1-1660 + 100 104 | | | Nar = | | 4 | | 30 + | | | 1 a | A ee is Lyell A = | } S | | 4 = \ | Ve g = | f B40 + A (ie ep a | | | 304 | 4 | 4 | ) , 4 | i 4 | t 4 404 | | | 4 | | y Y | | q | Wl | | m7 | 45-4 | Y Z | | | | | L | | | | Yy YY 50J } =I pamel man [ [> Fo T - 1 LOTUS: 20 eC 20 50 100 = 15 DIATOM PERCENTAGES Text-figure 10.—A23H Diatom Percentage Diagram. Solid curves represent actual percentages. Radiocarbon dates are placed to the right of the diagram. Oldest sediment is at the bottom of the column. 78 BULLETIN 361 oy Perot \ I | a a maf 0) 20 19 DIATOM PERCENTAGES Text-figure 11.—A06 Diatom Percentage Diagram. Solid curves represent actual percentages. Radiocarbon dates are placed to the left of the diagram. Oldest sediment is at the bottom of the column. HYDROLOGY, VEGETATION, AND CLIMATE: WINKLER ET AL. 79 LIGNUM VITAE KEY, Florida LV-2 Hiller Core Diatom Percentages M. Winkler, Analyst s oe. © 2 e~ s RS Ss ee : Ss ey RS RS & Ny S < XO SSS sor” Sor Fe 1s SF Se SE SHS LS wf Qo TRS PV Mick of 10 on Pasties é [a fae eerie 143 18 34 0 210k | Sa SSeS 10 6 19 4 154 i 20 250 + 30] | 25 34 354 404 454 € 50 600 + | = 55 3s a anP a ee ee) SCAR AA Oh 3 |e 65 ul 75 1040 + ssf a 85 904 I 95 2290 + 50 100 0 i 0;9 Uns 20 20 40 In ae 20 20 40 eyiceti= 20 40 20 20 40 60 80 100!" DIATOM PERCENTAGES Text figure 12.—Lignum Vitae Key, Florida, LV2 Diatom Percentage Diagram. Radiocarbon dates are placed to the left of the diagram. Oldest sediment is at the bottom of the column. and Pinnularia species, as well as more alkaline Am- phora, Anomoneis, Nitzschia, Cocconeis, and Diplo- neis spp. A study by Wood and Maynard (1974) may illuminate reasons for the unexpected presence of Eu- notia and Pinnularia diatoms at this site. These inves- tigators analyzed algae trapped in air nets placed on the 7-mile fire tower in ENP. They found that aside from marine algae which had traveled more than 64 km from the sea, there were several species of acid and circumneutral Eunotia and Pinnularia diatoms in the traps which had probably been airborne from northern and central Florida sites. Eunotia and Pin- nularia are frequently found growing in lakes under- lain by acidic sands in northcentral Florida (Sweets er al., 1989; Whitmore, 1989; Sweets et al., 1990). Other aerophilic diatoms found in the air nets included Mas- togloia, Amphora, Nitzschia, and Hantzschia species, and Asterionella formosa (Wood and Maynard, 1974). They also analyzed ENP surface water foams which contained diatoms and theorized that these foams were easily picked up, shredded, and transported by the wind to colonize or recolonize distant sites. The pres- ence of Hurricane Andrew debris at several Everglades sites during our fieldwork in February 1993 (Winkler, personal observation) illustrates the importance of wind as a factor for distribution of diatoms and other organisms in storm-swept southern Florida. Lignumvitae Key (LV2) At Lignumvitae Key site LV2 (Text-fig. 12), dia- toms are relatively abundant only in the surface sedi- ments. Marine diatoms, such as marine Amphora spp. and Navicula spp., Pleurosigma, and other saline di- atoms (Triceratium, Thalassiosira, and Paralia sulcata genuina f. radiata) comprise the majority of species above 15 cm in the core. Many of the freshwater spe- cies, such as Amphora cf acutiuscula, Cyclotella kuet- zingiana, and Navicula cf salinarum are also found in brackish water. Sponge spicules and chrysophyte cyts are abundant only in the top 70 cm of the core. Pyrite framboids, indicative of reducing conditions, are fre- quent in the basal sediments of LV2. Diatom Discussion The presence of diatoms in the Everglades and the Keys sediments has been either feast or famine. In much of the sediment, diatoms are absent or very sparse. However at times, and at several different sites 80 BULLETIN 361 (some more than 40 km apart), there are abundant planktonic diatoms indicating high water levels in the southern Everglades. These findings are synchronous and indicate high water between about 2000 and 1600 yr B.P. at site A23 (Text-fig. 10), around 1900 and possibly 1600 yr B. P. at site AO6 (Text-fig. 11), and between 1900 and possibly 1600 yr B. P. at Gator Lake (Text-fig. 9). The high water levels in this time period may be concurrent with a local sea-level highstand in Florida Bay (H. Wanless, personal communication, 1998). High water in ENP during this time interval also correlates well with interpretations of high water in northern Guatemala from similar findings of abun- dant planktonic diatoms in otherwise diatom-barren sediment cores from Laguna de Petenxil in northern Guatemala (Patrick, 1966). This extra-regional hydro- logic similarity is not surprising. In an Americas lake- level database which includes late-glacial and Holo- cene sites, there are similarities in water level changes in lakes within the Caribbean latitudes throughout their history (Winkler er al., 1996b). The Everglades and northern Guatemala are within this latitudinal range. Aside from the diatom-rich period between 1900 and 1600 yr B.P., there are very sparse diatoms before about 1900 yr B. P. at all Everglades sites examined. After 1600 yr B. P. diatoms are either rare at some sites such as Gator Lake, or are abundant shallow water taxa that grow in high nutrient conditions, among heavy macrophyte cover, and/or with heavy algal blooms. Reasons for the scarcity of diatoms in some wetland sediments might include competition for a limited sil- ica resource. This is unlikely in the Everglades. At only one site (Gator Lake) do diatoms and other sili- ceous objects (chrysophyte cysts and sponge spicules) have an inverse relationship. At all other sites exam- ined, these siliceous remains are abundant at the same time and disappear together at other times. Dissolution of diatoms and other silica objects may be due to changes in water chemistry. Strong brines, especially Na,CO, and NaCl, and salts of other single valent cat- ions, dissolve silica rapidly. In an experiment by Bark- er et al. (1994), diatoms dissolved in these brines in a matter of days. High pH accelerates diatom dissolu- tion. In fens that receive very alkaline (pH >9) ground or spring water, diatoms are present in the top sedi- ments, but only highly silicified remains are found a few centimeters downcore (Winkler, unpublished data). Dissolution conditions can be very complex. Some elements, such as iron and aluminum, make complexes with brines and retard dissolution. Seawater incursions at some sites in ENP may destroy fresh- water diatoms but may not provide high enough salin- ities for a long enough duration for growth of saltwater taxa. In combination with drought which concentrates salts found in freshwaters, water level and water com- position changes in the Everglades environment may be too harsh for sustained growth of many organisms. Increased UV-B penetration of surface waters in recent decades, as documented at other sites, may be causing changes in Everglades biota. Diatom growth is sup- pressed by 40% by UV-B in alpine lakes (Leavitt and Vinebrooke, 1999). The morphometry of the diatom itself can prevent or delay dissolution—(Barker, 1992; Barker et al.,1994) those diatoms with low surface area to vol- ume ratios remain, while other diatoms dissolve. Tur- bidity can also cause decreased diatom growth as can excessive nutrient or metal loading. If increased silts and clays and/or macrophyte growth such as water lil- ies shut out light, diatom growth would be reduced. Dense blue-green algae blooms also shut out light and may interfere with diatom growth. Wood and Maynard (1974) and Gleason and Spackman (1974) have mea- sured blue-green algae mats in excess of 10 cm depth in surface waters. Very warm temperatures (as high as 36°C, Browder ef al., 1981) may also favor blue-green algae growth and discourage (or prevent) diatom growth. In temperate lakes diatom growth is dominant during cool spring and fall months (Hutchinson, 1975), giving way to blooms of green and then blue-green algae during hot summer months. Blue-green algae dominance in the Everglades surface waters may be related to their tolerance of high temperatures and high carbonate environments, and to their more efficient uti- lization of other abundant nutrients. Indeed, some blue-green algae precipitate carbonate (Gleason and Spackman, 1974) and contribute to the formation of marl which covers large areas of the shallow-water Everglades today. The periphyton are the basis of the aquatic food chain upon which most other Everglades organisms are maintained. Some blue-green algae also fix nitrates from atmospheric nitrogen, adding to the already abundant nutrients in Everglades waters which stimulate excess periphyton growth and, at times, lead to anoxic conditions at some sites (especially under low flow conditions). Some blue-greens (e.g., Micro- cystis) secrete phytotoxins which may exacerbate poor growing conditions for other forms of plankton. Agricultural enrichment by nitrogen and phosphorus in the northern Everglades has been studied by Rader and Richardson (1992). They found that annual pri- mary productivity and algal biomass increased at least 3-fold from nutrient enrichment, but algal diversity did not change (although there were significant species changes and a surprising shift from cyanobacterial mats to dominance by filamentous green algae). How- ever, there was increased diversity of macro-inverte- HYDROLOGY, VEGETATION, AND CLIMATE: WINKLER ET AL. 81 brates. The increased minerals identified in our surface samples and interpreted as resulting from agricultural enrichment may explain the abundance of remains of biota in the top sediments at some sites and the dearth of microfossils at depth in some of the cores. Comparison of Paleoecological Results with Studies of Modern Periphyton Ecology and Distribution Everglades periphyton taxonomy, chemistry, and distribution have been studied by Van Meter (1965), Gleason and Spackman (1974), Wood and Maynard (1974), Browder et al. (1981), Swift (1984), and Swift and Nicholas (1987). Much of their findings are sum- marized in Browder et al. (1994). The dominant algal taxa of the important periphyton communities are list- ed in Table 16.1 in Browder er al. (1994). The periph- yton communities have been divided by their relation- ship to water chemistry into |). high mineral (carbon- ate), high nutrient communities, 2). low carbonate, high nutrient communities, and 3). low carbonate, low nutrient communities. The high mineral, high nutrient communities are very alkaline with pH values in ex- cess of 9 and are dominated by carbonate-precipitating filamentous blue-green algae. The low mineral, high nutrient communities are dominated by filamentous green algae in early summer, filamentous blue-greens by late summer and early fall, and in winter by diatoms characteristic of high nutrient waters. The low mineral, low nutrient waters had pH values below 6 and con- tained a diverse association of desmids and filamen- tous green algae, and diverse (but not dominant) dia- toms characteristic of oligotrophic water and wetlands. Looking at the spatial variations of the periphyton (Wood and Maynard, 1974; Browder er al., 1994) and specifically, of the diatoms (Whitmore, 1989), it is clear from our core sediment studies that some of the same relationships occur on a temporal basis. For ex- ample, Mastogloia smithii v lacustris, an alkaliphilic diatom found in mesotrophic to eutrophic surface wa- ters, is the dominant diatom in the marls found in the sediment cores (see especially AO6 and A23 diatom stratigraphies, Text-figs. 11 and 10). These marls are high carbonate and either high (A06) or low nutrient (possibly A23) environments. pH changes not directly obvious from sediment changes identified in the field or the laboratory may be interpreted by the presence/ absence of Mastogloia species at specific sites. At oth- er times, however, diatom assemblages unlike those found in the modern sediments were dominant at the sites analyzed and indicate deeper water and different water chemistry from today. Pollen and Sclereid Analysis Pollen analytical data from 5 sites, AO6 and A23 in Shark River Slough, L67A and L67C in WCA3B, and Lignumvitae Key illustrate the development of Ever- glades vegetation. In this section pollen taxa will be divided into 6 groups: Chenopodiaceae-Amarantha- ceae (cheno-am), pine, slough and marsh taxa, fern taxa, upland vegetation taxa, and mangrove taxa. Cheno-am is a pollen morphological group comprised of two related families with genera that have similar pollen that is virtually indistinguishable using ordinary light microscopy. Plants of these families are annual weeds of disturbed soil or perennial forbs or shrubs of desert, alkaline, or coastal areas. Based on pore num- ber and grain size more than one species may be rep- resented in our samples. Most grains are between 16— 22 wm in diameter and have more than 100 pores, typical of the annual weed genera. Cheno-am pollen found in Everglades sediment has not been assigned to a particular Everglades landscape type because it may be derived via wind transport from habitats far removed from the Everglades, although Loveless (1959b) found that Acnida cuspidata ( = Amaranthus cannabinus), pigweed, invaded sawgrass marsh during drought periods. Cheno-am is often the dominant pol- len type found in Everglades sediments. Pine pollen is often co- or sub-dominant with cheno-am pollen. It too is wind transported and may be of extra-local origin, although the pine forests of the Atlantic Coastal Ridge of South Florida may be the most likely source. Slough and marsh taxa include Nymphaea, Sagittaria, Utri- cularia, Cyperaceae, Cladium, Typha, Potamogeton, Justicia, Umbelliferae, and Gramineae. These species represent more local vegetation although grains can be transported by flowing water from their parent plants’ growth positions. Cyperaceae including Cladium may be underrepresented in Everglades pollen spectra be- cause these species propagate vegetatively as well as by seed and in the case of Cladium only older culms produce flowering stalks (Steward and Ornes 1975). Ferns are monolete and trilete spores including Poly- podiaceae, Anemia sp., and Osmunda sp. Ferns may be emergent plants of marshes or understory plants on hammocks. Upland taxa are mainly tree, shrub, vine, or perennial herb species of hammocks, tree islands, and willow heads. These include Myrica (wax myrtle), Quercus (oak), Myrtaceae (stoppers), and Cephalan- thus (buttonbush). Mangrove taxa are Rhizophora (red mangrove), Conocarpus (buttonwood), Laguncularia (white mangrove), and Avicennia (black mangrove). Sclereids are structures that provide hardness or ri- gidity to plant tissues. These structures may remain in sediments after degradation of other plant tissues and some sclereid forms are identifiable to genus. Both Cladium and Nymphaceae have recognizable sclereids which are diagnostic features of sawgrass and waterlily peats (Cohen and Spackman, 1977). Cladium sclereids 82 BULLETIN 361 A06 Percent € au0Z modern Depth cm. 2 1960 +/- 30 yrs B. P. N 2100 +/- 30 yrs B. PS o = L67A Percent =~" © © 2 Wan @ © o OCcenroaon eos 6 0-5.7 5.7-8.2 8.2-10.1 10.1-10.6~ 10.6-12.7 12,7-14,2 Depth cm. 14.2-15.4 15.4-15.9 N ° 3 oO = A23 Percent a N = % © BHwanowwvos ° o o o o o °o o o o o =] Ss oO 0-2 g > 2-3 Fj 1380 +/- 70 yrs B. P. 3-5 N ° 5-9 1660 +/- 100 yrs B.P. 3 9-12 [1890 +/- 70 yrs B.P. wo 12-21 F] 2600 +/- yrs B. P. RG 21-25 ee] Ml 28404/- 80 yrs BP. & SS SS i oO 25-33 np 33-41 N 41-50 P| 2840 +/- 70 yrs B. P. 2 = b L67C Core 2 Percent % Pine % Fern HOg@a @ % Upland % Mangrove % Chenopodiaceae-Amaranthaceae % Slough + Marsh Text-figure 13.—a-d. Pollen diagrams of A06, A23, L67A, and L67C. Pollen is presented as percentages of total pollen divided into Everglades community groups plus Chenopodiaceae-Amaranthaceae and Pinus. See discussion in text. are flat net-like masses with distinctive triangular openings (Plate 1, fig. 5); Nymphaceae sclereids are irregular stellate structures (Plate 1,fig. 6). A06 The AO6 pollen sequence is divided into three pol- len zones (Text-fig. 13a). Zone 1, 75-64 cm, is stati- graphically marl, more organic at the base and becom- ing less so at the top of the pollen zone. It has a basal date of ca. 2100 yrs B. P. Cheno-am dominates at 45— 50%, but pine is a secondary dominant. The slough- marsh component and the upland component each comprise ca. 12—15%. Sclereids of both Cladium and Nymphaceae occurred at very low concentrations (Text-fig. 14a). Zone 1 represents a low hydroperiod with a shallow mixed sawgrass-waterlily marsh and a drier upland area nearby. Zone 2, 64—25 cm, transgresses stratigraphic zones. HYDROLOGY, VEGETATION, AND CLIMATE: WINKLER ET AL. 83 A06 A06 Cladium sclereids Nymphaceae sclereids per per g dry wt 0.6m!i sediment fF 15000 20000 f 5000 10000 15000 20000 LF 10000 0-7 7-14 14-20 = 20-25 —) © 25-32 — = 32-39 a : ee 39-45 Q 45-50 50-57 57-60.5 60.5-64 64-70 70-75 a. A23 A23 Cladium sclereids Nymphaeacae sclereids per per g dry wt 0.6m!i sediment ° ° ° ° ° S S S S ° ° ° ° ° 3 3 3 S 3 S 3 S a S x S ca & x s oy rn L 1 f = ; = 0-2 0-2 [scan 2-3 ps: a 2-3 3-54 355 z E 5-9 °o 5-9 rs) = = 9-124 +fH4 € 9-12 Q 12-21 @ 12-21 21-25 21-25 25-33 25-33 33-41 33-41 41-50 41-50 Text-figure 14.—A06 Cladiwm and Nymphaceae sclereids (a); A23 Cladium and Nymphaceae sclereids (b). 64—57 cm is marl; 57-25 cm is fibrous peat. Marl at 60.5—57 cm yielded a radiocarbon date of c. 1960 yr B.P. The upper part of Zone 2 has no radiocarbon dates, but the change in pollen spectra between Zone 2 and | suggests that there is a hiatus; however, the charcoal profile does not show a sharp increase at the top of Zone 2. This zone is characterized by cheno- am dominance (Text-fig. 13a), ca. 60% of the pollen spectrum throughout the zone. At the beginning of Zone 2 slough-marsh and upland pollen groups occur at lower percentages than in preceding Zone 1, but by the end of Zone 2 the slough-marsh component in- creases to ca. 20% of the total pollen, while the upland component remains at less than 10%. Ferns occur at low frequency and the mangrove component makes a small contribution in the middle of Zone 2. Cladium sclereid concentrations rise gradually to a peak at 50— 45 cm (Text-fig. 14a), decline and then rise to a higher peak at 32-25 cm. Nymphaceae sclereid concentra- tions rise faster than Cladium sclereids and reach a peak at 57-50 cm, decline slightly, rise to a second higher peak at 45-39 cm, and then decline again. The high percentage of cheno-am pollen may be an indi- cator of rapidly fluctuating water levels and/or variable hydroperiod. Cheno-ams are early successional weeds which can take advantage of briefly available habitats such as areas alternating between inundation and des- sication over short time intervals. In late Zone 2 at 50-25 cm the slough and marsh pollen group per- centages rise and both Nymphaea pollen and Nym- phaceae sclereid concentrations increase. This suggests a longer hydroperiod during this interval. Zone 3, 25—0 cm is stratigraphically fibrous peat. A radiocarbon date on sediment from 25—20 cm yielded a modern (<~100 years old) date. Zone 3 cheno-am pollen spectra show a sharp decrease, falling from ca. 60% to ca. 30% and then to less than 20% (Text-fig. 13a). The slough-marsh component increases to almost 30% of the pollen total. Cladium sclereid concentra- tions (Text-fig. 14a) peak early in Zone 3 (continuing the trend seen in Zone 2), decline in the middle of Zone 3, and increase again at the top of Zone 3 (the surface sample). Nymphaceae sclereid concentrations continue the decline begun in late Zone 2. Upland pol- len increases from ca. 15% at the base of Zone 3 to almost 40% at the top of Zone 3 (Text-fig. 13a). The most important species in the upland component is wax myrtle, but buttonbush and Vitis (wild grape) also contribute to the increase. The increase in the upland and fern groups may indicate development of a ham- mock nearby, or may be the result of upland species colonizing the newly available habitat of levee and highway embankments (Leyden in Delfino er al. 1994). Mangrove pollen (Rhizophora and Conocar- pus) occurred sporadically in Zones | and 2 and was very scarce (mean = 0.28%). In Zone 3 it occurred in every sample and accounted for almost 1.5% (mean = 1.42%) of the total pollen sum. In all zones mangrove pollen is probably derived from distant sources, prob- ably the southwest end of the Shark River Slough. Its increase in Zone 3 may indicate recent deeper incur- sions of salt water up the Harney and Shark rivers into the Slough accelerating the expansion of mangroves up-slough so that the pollen source area is now a little closer to AO6 than in the past. A23H The A23H pollen sequence is divided into four zones (Text-fig. 13b). Pollen Zone 1, covers the basal sandy marl deposits (50-33 cm) and is characterized by a high slough and marsh percentage, accounted for almost entirely by /soetes microspores. Nymphaceae and Cladium sclereids occur at very low concentra- tions (Text-fig. 14b); Cladium sclereids were not found 84 BULLETIN 361 in the upper sample of Zone 1. Pollen Zone 2 covers two stratigraphic units, a marl layer from 33-25 cm and the lower sample from an organic marl layer, 25— 21 cm. It is characterized by cheno-am dominance, 60-70% of the pollen total, and a very low slough- marsh component percentage (Text-fig. 13b). Both Cladium and Nymphaceae sclereid concentration in- crease slightly over levels in Zone | (Text-fig. 14b). Pollen Zone 3, 21—2 cm covers five stratigraphic units: the upper sample of the first organic marl layer (21— 12 cm), a second marl unit (21—9 cm), a charcoal stained marl unit (S—9 cm), a third marl unit (S—3 cm), and the lower sample of the second organic marl unit (3-2 cm). Zone 3 is characterized by cheno-am and pine co-dominance (Text-fig. 13b). The slough-marsh component is variable, but increases to almost 20% by the end of Zone 3. Cladium and Nymphaceae sclereid concentrations increase sharply in Zone 3 (Text-fig. 14b). Zone 4, the surface sample (upper sample of the second organic marl unit, 2—O cm) is once again dom- inated by cheno-ams (Text-fig. 13b). The pine and slough-marsh components percentages are very low. The upland component percentage which increased throughout Zone 3 holds steady. Cladium sclereid con- centrations reach an all time high, while Nymphaceae sclereid concentrations decline precipitously (Text-fig. 14b). Zone | is dominated by /soetes microspores (Text- fig. 13b). Isoetes flaccida, the only species mentioned in Long and Lakela (1976) for central and southern Florida today, inhabits sluggish waters. According to Tryon and Tryon (1982) ‘in the American tropics [/s- oetes| species grow in lakes, usually in rather shallow water, in pools or in streams, in grassy turf at the bor- der of lakes, in wet open sandy soil...” (Tryon and Tryon, 1982: 829). The presence of /soetes does not necessarily imply deep or continuously present water. Pollen and sclereid data indicate low frequencies of Nymphaea and Cladium/Cyperaceae and a relatively greater frequency of upland taxa. LOI and HLOI evi- dence of low percent organic and low percent carbon- ate, microscopic observation of abundant sand grains, Isoetes dominance and low pollen concentration, and low occurrences of Nymphaea and Cladium suggest a seasonally inundated, wet open sandy habitat, with ar- eas of clear standing water, possibly an /soetes marsh. Zone 2 is dominated by cheno-ams both relatively and absolutely. This zone may represent a time of drought or highly fluctuating water levels and hydroperiod. Zone 3 is characterized by Pinus and cheno-am co- dominance with these two taxa switching back and forth as dominant. The slough and marsh group in- creases fairly steadily early in the zone, declines in the charcoal stained marl unit at 9—5 cm, but recovers in the upper two samples. Presence of Nymphaea sug- gests at least pockets of deeper water in the area of A23 and a longer hydroperiod than that of Zones | and 2. However the deposition of marl layers during the time represented by Pollen Zone 3 indicates radical changes in hydroperiod. Cladium/Cyperaceae pollen increases during these marl-short hydroperiod epi- sodes. Zone 3 appears to represent a time when hy- droperiods were very variable and the landscape was very patchy with small areas of deeper water sloughs surrounded by marsh and drier areas. Zone 4, a single sample, represents modern pollen deposition (Casuarina is found in this sample). The pollen spectrum is dominated by cheno-ams. Pollen from slough-marsh and upland groups decrease in per- cent and pollen concentrations of these groups fall pre- cipitously. The Zone 4 pollen spectrum appears to rep- resent a depauperate wet prairie community. L67A The L67A pollen sequence is divided into three zones (Text-fig. 13c). Zone 1 is older than 3500 yr B. P. and is characterized by cheno-am dominance less than 50%, slough-marsh group slightly greater than pine at ca. 25%, and a small incidence of upland pol- len. Zone | is interpreted to represent relatively long hydroperiods. Zone 2 has a basal date of 3500 yr B. P. The top of the zone is undated. Zone 2 pollen spectra are dominated by cheno-am pollen at 60-70%. Slough-marsh and pine groups decrease from Zone | percentages and pine is always greater than slough- marsh. By the end of Zone 2 slough-marsh is at its lowest percentage. Upland group pollen percentages increase throughout Zone 2. Fern and mangrove groups appear in upper Zone 2. Zone 2 is interpreted to represent shorter hydroperiods than Zone 1 with drought increasing through time. Zone 3 has a basal modern radiocarbon date. The abrupt change in pollen spectra signals a probable hiatus. Cheno-am percent- ages decline abruptly to ca. 25% and continue to de- cline upcore. Pine increases initially, but then also de- clines upcore. The slough-marsh group percentage tri- ples over Zone 2 values and then increases upcore to dominate the surface sample at ca. 80%. Fern and up- land groups increase in Zone 1, but decline in the sur- face sample. Pollen from mangrove taxa is present only sporadically. Zone 3 is interpreted to represent recently artificially ponded conditions resulting from construction of the Tamiami Trail and L67A and C canals. The L67A pollen diagram resembles those of AO6 and L67C in the decline of cheno-ams and the increase in slough-marsh and upland groups pollen in recent samples. HYDROLOGY, VEGETATION, AND CLIMATE: WINKLER ET AL. 85 L67C Only a few samples from L67C have been examined (Text-fig. 13d). These samples resemble those from the A06 core. Cheno-am dominates the pollen spectrum in the oldest sediment; pine is variable, as is the slough- marsh component. The upland component increases over time and is a large proportion of the surface sam- ple. The mangrove component is also most evident in the surface sample. Gator Lake Subsequent to our coring effort at Gator Lake, we learned that the lake had been cored by a group from the Environmental Engineering Dept. of the University of Florida in Gainesville, Florida (Delfino et al., 1994). This group obtained a 40 cm core from Gator Lake which was 7'°Pb-dated and found to cover 90 years. The core was used for Hg analysis of the sediment and for pollen analysis (carried out by B. Leyden [Delfino et al., 1994]). The pollen indicated that willow trees expanded near the lake in the last 50 years becoming most abundant since the 1980’s. Cheno-am_ pollen dominated throughout the 90 years covered by the sed- iment core. Pine pollen decreased in the last 35 years, while pollen from Compositae increased in the last 50 years. The aquatic environment was dominated by Nu- phar (yellow pond lily) and Sagittaria (arrowhead). Pollen analysis of our longer sediment cores from Gator Lake is in progress. One interesting finding is that Nuphar pollen is abundant in Gator Lake sedi- ments from 400 cm depth (about 1500 yr B. P.) to the present. At other sites in the Everglades, Nymphaea (white water lily) is the abundant water lily pollen. Pollen analysis also indicates that Salix (willow) pollen is only present in the top 40 cm representing the recent several decades at Gator Lake. The lake is presently surrounded by shrub willows. These may have spread from stands that grew on spoil piles from construction in the 1930’s and 1940’s of the nearby Miami Canal or may have become established after local fires burned the surrounding peat during drought (see char- coal stratigraphy, Text-fig. 5). Willows are known to colonize burned-over peats in the Everglades (Hof- stetter, 1974) and the high charcoal in the recent sed- iments of Gator Lake (Text-fig. 5) suggests that willow growth near the lake may have been initiated after fire (probably during drought or drawdown due to canali- zation) burned into the deep sawgrass peat around the lake. Lignumvitae Lignumvitae Key was chosen as a coring site be- cause it 1s a protected state botanical site, has a diverse hardwood hammock vegetation, and has an elevation Lignum Vitae, LV 2 Percent Percent Depth cm Wo (n = 883) 1 (n = 481) 26-100 So YL ALAR) 2290 +/- SO vey BP Rhizophora % Cheno-am | Conocarpus [a e Oo Laguncularia lm aviewen % Other a b Text-figure 15.—a and b. Lignum Vitae (LV2) pollen diagrams showing percent Chenopodiaceae-Amaranthaceae versus all other pollen (a) and mangrove pollen divided into constituent species (b). In (b)n = the sum of mangrove pollen. of close to 5 m, one of the highest keys in Florida Bay. The LV-2 coring site was a relatively shallow (about 10 cm), saline, mangrove-fringed (Conocarpus, Avicennia) pond (pH 8) separated by an old limestone ridge from a tidal flat. Saltmarsh plants such as Sali- cornia (saltwort) and Limonium sp. (sea lavender) were growing on the tidal flat, while the cactus Opun- tia cereus was found near the pond. Two samples have been analyzed for pollen: 96—100 cm and 20—25 cm. (Text-fig. 15). The 96-100 cm sample is the basal or- ganic sediment which was AMS radiocarbon dated at 2290 + 50 yr B. P. The 20—25 cm sediment is undated but is within the historic horizon. The pollen in the younger sample is quite different from that in the older. The younger sample is domi- nated by Chenopodiaceae/Amaranthaceae (pigweed family) pollen, which constituted only 14% of the old- er sample (Text-fig. 15a). Most of the pollen in the older sample is Conocarpus, a mangrove plant. Con- sidering mangrove pollen only (Text-fig.15b) Rhizo- phora and Avicennia are present in only trace amounts and Laguncularia is absent in the older sample; while in the younger sample Rhizophora and Conocarpus are co-dominant with only minor representation of other 86 BULLETIN 361 mangroves, Laguncularia and Avicennia. Pollen of Al- nus, Salix, Acacia, Guaiacum officinale, and G. sanc- tum is present in the older sample, but not the younger sample. Pollen of Pinus, Taxus-Cupressaceae-Taxo- dium, Juniperus, Myrica, Schinus, Anacardiaceae, Pal- mae, Solanaceae, Tubuliflora Compositae, and Legu- minosae are present in the younger sample, but not the older one. Taxa found in both samples include: Bur- sera, Myrtaceae, Alternanthera/Gomphrena, and Rhamnaceae. Of the mangrove taxa Conocarpus is the least de- pendent on immersion in fresh or saline water. It pre- fers drier ground than the other three taxa and is also a component of the tropical hardwood forest. Its dom- inance of the older sample suggests drier conditions at 2290 years ago and lower sea level. It is, however, growing abundantly near the coring site now, co-dom- inant with Avicennia (black mangrove). Rhizophora is also present today and is replacing Conocarpus as sa- linity of the site increases due to a rising sea level. The sparseness of Avicennia pollen in the two samples examined and abundance of Avicennia at the site today suggests that this mangrove species has expanded in recent decades at the LV2 site. However, Riegel (1965) states that Avicennia produces little pollen which has a restricted local distribution. He considers Avicennia pollen percents of 1—2% to indicate presence of the plants at the site and pollen percents more than 5% to indicate dominance at a site. Chenopodiaceae dominance of the younger sample and the presence of Schinus pollen may indicate clear- ance of some of the island for habitation thus opening up the tropical forest habitat to invasion by weeds. The pollen spectra document the declining presence of Lig- num Vitae (Guaiacum spp.) on the island. While ham- mock flora is still well-represented, anthropogenic pressures have greatly changed the forest composition on Lignumvitae Key. Cladocera Analysis Cladocera (Arthropoda: Crustaceae, Branchiopoda) are small aquatic invertebrates (0.2—2.0 mm) found primarily in fresh water. A few taxa are marine and some freshwater taxa can tolerate brackish water. All of these creatures can swim, but while some forms are primarily free-swimming in open water others are bot- tom-dwelling or epiphytic. Cladocera are indicators of water chemistry and nutrient status. Loftus ef al. (1986) found cladocera in the Shark River Slough. Chitinous exoskeletons of cladocera are common com- ponents of lake sediment and should therefore be pre- sent in marsh-slough deposits in the Everglades. A06 Chitinous exoskeletal remains of 28 cladoceran taxa were identified from AO6 sediments (Table 4). Of these, Euryalona and Oxyurella have not been found in previous neolimnological surveys of ENP (Loftus, unpub. data, 1993), however they have been found in southern Florida (Crisman 1980, Frey 1982) and it is reasonable to expect to find them in ENP. Cladoceran remains occurred throughout the core (Text-fig. 16a). They were very rare in the organic marl at the base of the core and only two taxa were represented, Alona spp. and Chydorus brevilabris. The number of cladoceran parts and taxa increased slightly in the lower part of the peat, 57-20 cm. Cladoceran parts and taxa increased again beginning at 20 cm and continued at an exponential rate up to the surface, 7— 0 cm. One possible explanation for this distribution is post-depositional degradation of cladoceran remains over time although chitinous exoskeletons are known to resist decay in lake and bog deposits over even lon- ger spans of time than are represented by this core (Frey 1964). Oxidation during dry phases would not affect cladoceran remains more than the organic matrix surrounding them, therefore the number of cladoceran remains in a given sample of Everglades peat or marl probably fairly represents the number of cladocera liv- ing in the area at the time the deposit formed. Hunt (1952) found that cladocera were never very abundant in the open water of the Tamiami Canal, but that lit- toral cladocera were found in periphyton growing on emergent and submerged plants. Most of the species listed in Table 4 are littoral substrate dwellers which live on plants rather than in open-water. Thus another explanation for the distribution of cladoceran remains in AOQ6 deposits is that cladocera are tracking periph- yton production, which is in turn responding to water level and nutrient changes. The cladoceran data would suggest that periphyton production increased dramati- cally at this site in the last 50 years. This kind of limnological change would be expected in light of ev- idence of increased allochthonous nutrients to the site in recent decades. A23H Chitinous exoskeleton remains of at least 17 cla- doceran taxa were recovered from A23H deposits (Ta- ble 5, Text-fig. 16b). Cladoceran remains are so scarce in the deposits from 50—21 cm that little can be in- ferred from them except that conditions at the A23 site during this time never favored development of a cla- doceran assemblage. Rapidly fluctuating water levels and low nutrients could be contributing factors. Pe- riphyton production may have been insufficient in this HYDROLOGY, VEGETATION, AND CLIMATE: WINKLER ET AL. 87 Table 4.—A06 cladocera taxonomy and counts. Minimum number (MNI) molts/deaths on counts from four slides per sample. Depth (cm) Taxon 0-7 7-14 14-20 20-25 25-32 32-39 39-45 45-50 50-57 57—60.5 60.5—64 64—70 70-75 Alona affinis 2 1 2 — —_ 1 - A. verrucosa 4 | 1 — 1 — —_— 0.5 1 A. setulosa 2 1 —_ — —- 1 A. rustica 4 1 A. guttata type 3 1 1 2 A. karua type 0.5 0.5 1 Alona spp. | | | — — — 05° — Euryalona = — 1 — —_— 1 Chydorus brevilabris 1 — 1.5 — 0.5 Chydorus spp. — 2 — 1.5 — 1 1.5 — — — 1 —_- — Chydorus nitidulus/Ephemeroporus ES 0.5 — 0.5 Ephemeroporus hybridus — 0.5 E. cf. archboldii 0.5 Dunhevedia 1 Oxyurella l Leydigia acanthocercoides 1 1S = 1 L. cf. parva | Leydigia spp. ] 1 1 Alonella excisa 2 Alonella spp. A) 1 — 1 _ — — 0.5 Pleuroxus/Alonella — — 0.5 0.5 Camptocercus l 1 Ilyocryptus 2 0.5 165) 0.1 0.5 —- —- — Grimaldina 1 cf. Eubosmina tubicen IGS) 1 Ceriodaphnia 0.5 — — — Daphnidae ies) — 0.5 — 1 — — 155) — 0.5 — —_-_ — Scaphoberis 0.5 Total MNI 34.5 9'5 10 Sal DS Tes) 3 6.5 3.5 1 1 05° — Total No. Taxa 21 10 9 5 3 il 3 8 4 2 1 1 — Total Cladoceran Pieces 193 133 106 29 30 34 32 37 13 10 5 5 3 A06 A23 Cladoceran pieces per g dry wt Cladoceran pieces per g dry wt ° © 2 iS iS S = ° ° ° ° ° ° ° L 1 1 1 4 1 ai] 0-7 0-25 — foie 2:34) Ab 1380 +/- 70 YBP 14-20 20-25 S25 — 25-32 — 5-9 1660 +/-100 YBP a) a) 2 a e912 1890 +/- 70 YBP B 45-50 Q 12-21 2600 +/- 70 YBP Oevsp-57, OW ai-25 2840 +/- 70 YBP 57-60.5 1960 +/- 30 YBP 25-33 4 2830 +/- 60 YBP 60.5-64 64-70 33-41 | 70-75 2100 +/- 30 YBP 41-50 2840 +/- 70 YBP a. b. Text-figure 16.—Cladoceran pieces per gram dry weight for AO6 and A23. Error bars = | standard deviation based on 4 replicates per sample. 88 BULLETIN 361 Table 5.—A23H cladocera taxonomy and counts. Minimum number (MNI) molts/deaths on counts from four slides per sample. Depth (cm) Taxon 0-2 2-3 3-5 5-9 9-12 12-21 21-25 25-33 33-41 41-40 Alona affinis I 1 A. circumfimbriata 2 A. costata 1 A. guttata 1 A. intermedia 1 A. rustica l A. setulosa 2 1 A. verrucosa 3 Alona spp. — — 3 2.5 — — 1 Oxyurella 1 Camptocercus | Leydigia parva/acanthocercoides 1 i Alonella cf. dadayi 2 Alonella spp. 0.5 Chydorus brevilabris 2 _ 0.5 Chydorus/Pleuroxus 1] cf. Ceriodaphnia 1 Daphnia spp. 1 1 Ilyocryptus ct. gouldeni 0.5 Ilyocryptus spp. —— — 1 Macrothrix paulensis 1.5 Macrothricidae 0.5 Total MNI 19 4 3)5) 3 2 10) 3.5 0 0 (0) Total No. Taxa 12 4 4 2 2 (0) 4 0 (0) 0 Total Cladoceran Pieces 189 38 45 8 5 3 5 0 (0) 10) area from 2800-1650 years ago to support many cla- docera. Cladoceran remains increase in samples from 12-3 cm suggesting more permanent water and/or in- creased nutrients during this time interval. Cladoceran remains increase exponentially in the uppermost two samples. Because other data suggest lower water levels or shorter hydroperiods during this time, increased nu- trients may be a factor in the increase of cladocera at this site. Sponge Spicule Analysis Spicules are the siliceous remains of sponges (phy- lum Porifera). Pennak states that ““Sponges are most common in waters less than 2 m deep ... and are seldom found in extremely rapid waters’ (Pennak 1978). They require hard substrates and rarely grow on mud or silt. Aquatic macrophytes can, however, provide a substrate for sponges to encrust. They are quite sensitive to environmental conditions such as light intensity, pH, conductivity, bicarbonate ion con- centrations, and calcium concentrations, and are very sensitive to eutrophication and pollution (Harrison 1974, 1988; Poirrier, 1974; Pennak 1978; Frost 1991). The Everglades would seem to provide ideal habitat for freshwater sponges, but they have rarely been stud- ied (Poirrier, 1976; Harrison et al., 1979) and their role in the Everglades ecosystem is not known; however, G sponges can have a “substantial influence on total nu- trient cycling and primary production ... [and may operate] primarily to limit the availability of materials to other organisms within the food web” (Frost 1991). Because sponges are potentially competitive with pe- riphyton for substrate, their role in the development of the Everglades may be of interest. A06 Sponge spicules from A06 deposits appeared to be primarily smooth, cylindrical fusiform, amphioxic megascleres when viewed with ordinary light micros- copy (Text-fig. 17a, Plate 1, fig. 3). All megascleres were fragmentary and some showed varying degrees of axial canal widening and degradation. This situation is similar to that of spicular remains studied by Racek (1966) in deposits from Laguna de Petenxil, El Petén, Guatemala. He attributed axial canal widening and degradation to bacterial reduction of gypsum in the sediment releasing Ca(OH), which dissolved hydrated silica. The degraded condition of AO6 megascleres suggests that this process may have occurred in the Everglades in the past. Increased amounts of Ca(OH), in the sediment from bacterial action may also be op- erative in the dissolution of diatoms. Some A06 megascleres were virtually complete, missing only their tips. Measurement of 50 virtually HYDROLOGY, VEGETATION, AND CLIMATE: WINKLER ET AL. 89 A06 A23 Sponge spicule pieces per g dry wt Sponge spicule pieces per g dry wt 2 8 S S S S S S o J iJ =] J i=) i=J i= o o o i=) o o Oo o o o o o o o i=) i=] o o i=} i=} o o o i=} i=] o i=} o N v o o o N Tv N tc o o Oo N vt SSS ES 4 0-7 0-2 7-144 2-3 3 a Rp aera 4 1380 +/- 70 YBI » 20-2544 SAS E 25-324 E 5-9 1660 +/-100 YBP me SG) = 9-12 1890 +/- 70 YBP B 39-454 a 3 & 45-504 Bie 2600 +/- 70 YBP 50-57- 21-25 2840 +/- 70 YBP 57-60.5 4 1960 +/- 30 YBP 25-33 2830 +/- 60 YBP 60.5-64 coe 64-70 70-75 2100 +/- 30 YBP 41-50 2840 +/- 70 YBP a. b. Text-figure 17—Sponge spicule pieces per gram dry weight for AO6 and A23. Error bars = | standard deviation based on 4 replicates per sample. complete spicules from 20—14 cm depth indicates that megascleres average at least 396 4m long (range 300— 476 pm, S.D. 43 pm) by 30 pm w (range, 16.5—43 wm, S.D. 6.4 4m). Several taxa have smooth mega- scleres in this size range: Ephydatia fluviatilis, Spon- gilla alba, and S. cenota (Frost 1991). Unfortunately, identification is based on microscleres and gem- moscleres, which are scarce in A06 deposits. The few gemmoscleres seen resemble those of Spongilla lacus- tris, but the spines are not very well defined. These spicules are slightly bent cylindrical fusiform am- phioxes from 60—70 pm | with sparsely, but + uni- formly distributed, short, broad-based spines (Plate 1, fig. 4). With light microscopy the axial canal is visible running lengthwise within this spicule type. The ab- sence of definite microscleres and the large size of the megascleres suggest that E. fluviatilis may also be pre- sent, but its birotulate gemmoscleres were not seen. Sponge spicule pieces are present in every sampling increment of the AO6 core, but they are rare in the dark organic marl (75-57 cm, Text-fig. 17a). Two peaks in sponge spicule pieces are, however, apparent in the peat: one at 45—39 cm and another at 20-14 cm. when diatom frustules are also most numerous. A23H Sponge spicules were found throughout the A23 de- posits (Text-fig. 17b). A23 spicules were similar to those already described for AO6. They occurred in low numbers in deposits from 50—21 cm with a small peak at 41-33 cm. A very large peak occurred in the organic marl unit from 21—12 cm at the same time that plank- tonic diatoms occur. From 12—5 cm, spicules were very rare. Then from 5 cm up to the surface sponge spicules increased exponentially as did Cladium scler- eids and cladocera pieces. There was no numerical re- lationship among these three biotic indicators in earlier levels, therefore the increase in all three indicators may reflect some structural or functional change in the marsh ecosystem, possibly increased nutrients. HOLOCENE CLIMATE ON THE FLORIDA PENINSULA Our study of sites in the southern Everglades indi- cates a shift from a dry to wet climate in the middle Holocene at about 5000 yr B. P. which initiated for- mation of the peat-forming Everglades. Similar chang- es were taking place circum-Caribbean (Text-fig. 18). We looked for continental- and regional-scale factors which would effect this dramatic change. Climatic changes in North America during the Holocene were determined by collapse of the Laurentide ice sheet, the position of sea level due to ice retreat, the relative amounts of land and sea in the hemisphere, changes in the orbital parameters of the Earth which determine insolation variations and seasonality, volcanic erup- tions, and other boundary conditions (Text-fig. 19). Changes in the North Atlantic thermohaline circulation pattern would also affect what happens on land in southern Florida. Sea surface temperatures adjacent to the Florida peninsula are important in determining the amount of annual and seasonal precipitation with warmer water causing greater rainfall. In our investi- gation of the cause of the change from dry to wet 90 BULLETIN 361 | | | 5 ©} | | | ice) =I 77) (re om | o = = =o gr a | E 2 fe) =| eS as 2 g 2 s | O28 0 w| | BS w ao oe oS Oc} —| © = pO eo = i=) ne) ne] x 5 a0 0 or ®— a= ) oc | cS Dow iL co ao ® 2 ® >| Osc 2Q- =-c% ao] Bw ow gs go Els o— oO C SE 3 0 So ahs ior ax Oc o Fe 2 DE 2a ayes a2 024 £2 oe S| 28 Go| 995) 25 =8S/ 58| s= >| wo ws} Wor sa 5300 zs JO 3 } Qa @ 3 ~) So oO We Dry NoData[ lext-figure 18.—Time and space comparison of qualitative hydrologic changes (Wet/Dry) from regional paleoecological data. Sites range from thern to southern (ENP sites) Florida and from Haiti in the Caribbean to northern Guatemala. Timing of wet/dry transitions may not be a e as the line separating them suggests at some sites. HYDROLOGY, VEGETATION, AND CLIMATE: WINKLER ET AL. 9] f T T Ti T T 1 July + % solar radiation | Eslean Peg aurentics Sg d ONES Seasonality 4 fee Envelope Cee | TOM. Yinceh. a} 30 5 L : Everglades 2 re Hydrology @ o Warm n Ory = a x a 1 es = o ® * Modern 25 3 2 3 z H s Cool+ x a z l : fe} 20 G4 Vv SST Au Coldkaa m 9 ‘ 4& SST Feb January - % solar radiation | | | | | | 18 15 12 ) 6 3 te) yr. B-P. (x 10%) Text-figure 19.—Late-glacial and Holocene climate change dia- gram. The seasonality envelope illustrates changes in % solar radi- ation in July (+) and January (-) throughout the last 18,000 radio- carbon years (possibly 21,000 years if compared to the Uranium- Thorium coral chronology) determined by changes in the orbital parameters of the Earth (the Milankovitch cycle). It demonstrates that at about 12,000 through 8,000 yr B. P. seasonality was different from today because the Earth was closest to the sun in July (today Earth is closest to the sun in January) and summers were warmer and winters colder than modern in middle latitudes. The Laurentide ice sheet melted from the continent by about 7000 yr B. P. (Dyke and Prest, 1987). Sea Surface Temperature scale (SST, closed tri- angles: August; open triangles: February) is on right and indicates from foraminifera changes in ocean cores that SST (southeast of South Florida) was slightly warmer in winter than modern at about 6000 yr B. P. (Ruddiman and Mix, 1993). Sea Level Rise, the lower dashed-line curve, reaches to 4.5 m by about 5000 yr B. P. (Dyke and Prest, 1987; Wanless er al., 1994) but the rate of rise varied after about 3000 yr B. P. The Everglades peat was initiated at about 5000 yr B. P. possibly due to increased winter precipitation because of the warmer SST’s and the rising sea level. The changes in Ey- erglades hydrology (Wet or Dry) interpreted from our results is shown from 5000 yr B.P. to the present. Diagram modified from Kutzbach and Street-Perrott (1985). climate in Florida and the Caribbean region at about 5000 yr B. P., we consider two mechanisms: sea level rise and changes in ocean temperatures after collapse of the Laurentide ice sheet. Calculations of orbital con- ditions at 5000 yr B. PR. shows maximum insolation in early fall. Sea surface temperatures would therefore be higher at that time and the incidence of tropical cy- clones would increase. Increased storminess would bring more moisture to the Florida peninsula. Fossil data from foraminifera in ocean cores from the region (Ruddiman and Mix, 1993) indicate that sea surface temperatures southeast of the Florida peninsula did change at about that time. Sea surface temperatures were about 0.3°C warmer than modern in winter 6000 yr B.P., but about the same as modern (~28.5°C) in summer. In addition, because the S. Florida peninsula is relatively narrow with low relief and has a porous limestone aquifer, sea level rise during the Holocene was important to initiation of Everglades peat. Sea lev- el was 120 m lower than the present mean sea level at the last glacial maximum (18,000—21,000 yr B. P.), had returned to about 6.2 m below modern levels by 5500 yr B. P. (Fairbanks, 1989; Wanless ef al., 1994), to about 4.5 m below modern levels by 5000 yr B. P. (Dyke and Prest, 1987) and to about 3 m below mod- ern levels by 4000 yr B. P. (Colquhoun and Brooks, 1986). Rising sea level would raise the freshwater ta- ble in the Everglades wetlands (the freshwater aquifer overlies saltwater) and would slow sheetflow through the Everglades from the north. Most sites throughout Florida indicate drought be- fore 5000 yr B. P. and wet conditions after that time (Text-fig. 18), regardless of their proximity to the sea, indicating that changing climatic conditions such as increased precipitation due to rising sea surface tem- peratures in the middle Holocene (Ruddiman and Mix, 1993) especially in winter, may have been equally im- portant as sea level rise in initiation of the Everglades landscape. Furthermore, increased precipitation in winter in the middle Holocene (about 6000-5000 yr B. P.)—winter today being the driest time of the Ev- erglades year—may have provided the needed increased effective moisture for peat to accumulate at many sites. Other global-scale climatic events such as more nu- merous El Nino years since 5000 yr B. P. (Sandweiss et al. 1996) would also increase precipitation to the southern peninsula of Florida as it does today (Winkler et al., 1999). The interaction of rising sea level and increased pre- cipitation resulted in long hydroperiod in low-lying ar- eas and the accumulation of peat, especially in the Ev- erglades Depression south of Lake Okeechobee. High- er elevation areas adjacent to the Everglades Depres- sion did not accumulate peat until sea level rise raised the water table to intersect local low points. Once peat is present on the landscape it retards waterflow, further increasing the hydroperiod (water residence time) at a site. The presence of peat would also raise the water table at a site, separating the water in the peat from the carbonate-rich Everglades aquifer and thereby changing the chemistry of the site. The peat would then be watered by a larger proportion of water from rainfall than by groundwater or surface flow. The for- mation of barrier beaches surrounding southern Florida and the topography within the old limestone bedrock, also affect the rate of waterflow through the Ever- glades drainage and the accumulation of freshwater peats. Some of the higher elevation areas may never have accumulated peat. Instead seasonally wet prairies developed on short hydroperiod, higher elevation sites and marl deposition began. 92 BULLETIN 361 Our evidence for an increase in effective moisture in winter at about 6000—SO000 yr B. P. and initiation of peat deposition in the southern Everglades supports the Genesis! climate model simulations for the Caribbean region which show that in winter (December, January, February) at 6 ka, surface temperatures increased by 0.74°C, precipitation increased by 0.79 mm/day, and P — E increased by 1.2 mm/day, compared to modern values (Thompson and Pollard, 1995). What we probably see in the Everglades today is a landscape that has become increasingly fragmented af- ter 2900 yr B. P. by shrinkage of the peat-based plant communities and expansion of the drier plant com- munities. The modern dry conditions are further ex- acerbated by anthropogenic drainage, canalization, and drawdown of freshwater. IMPACTS FOR LAND MANAGEMENT AND DECISION-MAKING Today the Everglades hydrologic environment is in- creasingly uncoupled from climatic changes as water is artificially sequestered in some parts of the historic Everglades and diverted from other parts. Recent an- thropogenic nutrient and hydrologic changes seem to favor periphyton production leading to widespread marl deposition in contrast with climate- and sea-level- induced changes over the past 5 millennia when stand- ing deepwater peats formed. However, some of our cores (e.g. A23, Ever6, and 9-Mile) show that some areas have experienced marl production only and have, therefore, always had shorter hydroperiods. These marl prairies are important habitats for native Everglades fauna, notably the Cape Sable Sparrow. Therefore, simply increasing the amount of water standing over the whole Everglades by artificially maintained long hydroperiod/high water levels will not preserve the natural Everglades. Neither will suppression of wild- fires, which are necessary to the maintenance of the mosaic landscape by burning off peat and naturally lowering the topography so that ponds and sloughs can develop and provide sites for peat to accumulate again. A rewatering plan must include both wet and dry sea- sonal cycles in order to preserve the natural landscape of the southern Everglades—a shifting mosaic of wet and dry communities in space and time—as a func- tional habitat for both plants and animals. The mosaic landscape of the Everglades may become less complex if long-term water management does not take into ac- count the natural dynamics of the hydroscape and the topographically variable landscape which offers di- verse habitat for flora and fauna. Sea-level rise is another confounding factor that must be taken into account in an Everglades rewater- ing plan. There is pollen (mangrove taxa replacement) and diatom evidence of sea-level changes that correlate with findings in cores from Florida Bay. Chemical analyses of C111 sediments suggest a salt water in- cursion several millennia ago at sites east of Taylor Slough followed by a subsequent change to fresher water as channels were closed off. Therefore, changes in rates of sea-level rise and in the topography of Flor- ida Bay, both volatile processes, should be considered during water delivery to the lower Everglades. CONCLUSIONS Paleoecological study tells us that the Everglades landscape was (and is) a shifting mosaic of biotic com- munities initiated at about 5000 yr B.P. when the southeastern U. S. and a broader Caribbean region un- derwent transition from dry to wet climate. Our results indicate that most sites alternated between deposition of wet peat or drier marl at times throughout their ex- istence. These facts document that the modern mosaic landscape existed in time as well as space for at least five millennia. Fire and low, drought-induced, water levels are critical natural structuring agents in the de- velopment of the Everglades landscape but these events cause severe sediment decomposition. Due to fire and drought there are probably no marsh or prairie deposits with complete paleostratigraphic records and it is therefore necessary to piece together the history of the Everglades from many cores. These cores should be well dated because hiatuses in the record are not always stratigraphically obvious. A wide variety of physical and biotic parameters should be examined as well because chemical and hydrologic extremes also result in gaps in the biologic record. Most plant communities in the past were similar (in- ferred from pollen and sclereid analyses) to those pre- sent in today’s landscape, although in the course of our research we found at least one habitat type, an Isoetes marsh, which is not recognized in the modern Everglades. /soetes marsh is found today on the Yu- catan Peninsula, but is not listed as a biotic community in any of the vegetation surveys of the historic Ever- glades. Other vegetation changes, including the peri- phyton composition, have been caused by nutrient and trace element increases from land use changes in the last 50 or so years and the introduction of aggressive exotic plant species. However, dominant diatoms found in surface marls were also found to be the same taxa that dominated in ancient marl sediments. Cla- doceran assemblage changes appear to correlate with nutrient-driven periphyton changes in top sediments. Pollen also provided evidence of changes in man- grove species in Lignumvitae Key in Florida Bay. There Rhizophora is replacing Conocarpus as the sa- linity of the site increases due to sea level rise. At that HYDROLOGY, VEGETATION, AND CLIMATE: WINKLER ET AL. 93 site pollen also documents the declining presence of Lignum Vitae trees on the island and other hammock forest changes due to anthropogenic pressures includ- ing the introduction of exotic plant species. Planktonic diatom increases documented a wet pe- riod between 2000 and 1600 yr B. P. at several sites over a broad region of the Everglades. 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Aulacoseira, possible new diatom species, Gator Lake, 471 and 571 cm, 13 * 5—6 pm, with parallel rows of very fine pores (almost unresolvabletat000> mapnification) snoteralsoylongyspinesiesn-iiensnemeiei- n-ne eee nee nent ee ieee 77 35 Unidentified/sponge megasclere;, A065 14—20)icem> 266) imi longs =o erencneye) teil) ecient pee seems ere citsncnen antennae ee 90 4) Unidentified!sponseigemmoscleres-A06;)20—25icm> 7 Ohpumlon ge) senate one teenenene ieee cuen stanton cliente eee 91 5. Cladium sclereid piece, A06, 0-7 cm, longest dimension 333 jm, triangular openings ca. 23 wm. ...........--...----. 84 6 * INymphaceae!sclereid,A23>33—4 lem 600—G67.O)uml long. iss cia = estes eucre cieneae cetonsteaeeits etree ariel eer eae 84 99 HYDROLOGY, VEGETATION, AND CLIMATE: WINKLER ET AL. GHAPTER 6 A POLLEN ZONATION OF SOUTHWESTERN FLORIDA USING MULTIVARIATE STATISTICAL METH- ODS AND ITS APPLICATION TO TWO VERTICAL SEDIMENTARY SEQUENCES M. A. O’NEAL!, L. P. TEDESco!, C. SOUCH?, AND J. EF PAcHutT! Departments of Geology! and Geography’, Center for Earth and Environmental Science, Indiana University-Purdue University, Indianapolis, IN 46202 ABSTRACT Extensive and reliable modern analogs are the key to palynological assessments of habitat change. This study uses multivariate statistical techniques to reevaluate surface pollen distributions within Everglades National Park, South Florida. Results indicate that multivariate techniques provide a sensitive and informative measure of variations in the distribution of pollen and spores. The distribution of pollen and spores in surface sediments of southwest Florida were grouped into five distinct clusters, or pollen zones, containing a total of 10 sub-clusters that help delineate subtle differences within each zone. These pollen zones are: 1) mangrove swamp, 2) brackish marsh, 3) freshwater marsh, 4) headwater marsh, and 5) upland complex. The spatial distribution of these pollen zones strongly corresponds to the major physiographic provinces of the area. Cluster analysis indicates that individual taxa typically are not environmentally restricted and, in most environments, there is no single indicator species because of overlapping ranges. The results generated from the analysis of surface assemblages are applied to two vertical sedimentary sequences to interpret past environmental changes. Results show that these methods can be used to identify broad environmental changes (i.e., the overall late-Holocene transgression of South Florida) and can differentiate among different mangrove swamps where time integration of in situ samples has occurred. The method is limited in its ability to differentiate short-lived changes in coastal configuration (i.e., sea-level oscillations) as long as the overall environment remains in close proximity to the coastal zone. In these cases, detailed sedimentologic work, combined with palynological analysis is required, especially where sediment reworking has occurred. INTRODUCTION Pollen and spores incorporated into the sediment re- cord of the coastal systems of South Florida can pro- vide detailed information about environments of de- position. However, the variety of pollen and spore types present in most samples makes it difficult to compare and group assemblages by visual inspection of frequency histograms. Multivariate statistical meth- ods provide more robust techniques for comparing and grouping surface pollen sites, and also permit the si- multaneous investigation of multiple sample sites con- taining several taxa. Such techniques have been used successfully for ecological interpretations at the re- gional scale elsewhere: see, for example, Birks et al. (1975). To date, however, such methods have not been applied in South Florida, even though the vegetation communities have a distinct spatial distribution that is strongly related to salinity, hydroperiod, elevation, and substrate, and are likely to be amenable to such anal- yses. Moreover, given the considerable attention that has been, and is now being, directed towards the use of palynological data in interpreting the paleoecology of vertical sediment sequences in the area (Riegel, 1965; Spackman et al., 1966; Kuehn, 1980; Bartow et al., 1996; Meeder et al., 1996; Brewster-Wingard et al., 1997; Willard and Holmes, 1997; Winkler et al., 1998), such methods have great potential to associate vertical sequences of assemblages with surface pollen and spore groups in order to interpret paleoenviron- mental changes through time. The purpose of this study is two-fold. First, to de- lineate surface pollen zones in Everglades National Park, South Florida, using multivariate statistical methods. The objectives here are to (1) provide an objective model for interpreting the distribution of pol- len and spores in surface sediments, (2) demonstrate the sensitivities of cluster and discriminant analysis in delineating surface pollen clusters, and (3) provide a framework for paleoecological reconstructions in South Florida. Then second, to use the objective pollen zonation to analyze and interpret two vertical sedi- mentary sequences, one from the Harney River, the other from Gopher Key, in terms of late Holocene en- vironmental conditions. With these objectives, the pa- per is structured in two parts: pollen data for contem- porary sediments and their analysis are presented first; details of the vertical sequences, pollen counts, and their analysis, second. 102 BULLETIN 361 ore 59- (©) Core 59-T1 — © Core 9411-7 ~ Harney Rive O7 = ‘ GULF OF MEXICO Rod MANGROVE SWAMP Es BRACKISH TO TRANSITIONAL MARSH FRESHWATER MARSH WITH HAMMOCKS FRESHWATER MARSH - SLOUGH [4 umestone upLAND COMPLEX SHALLOW MARINE MUDBANK KILOMETERS Text-figure 1—Major physiographic provinces of the South Florida peninsula (modified from Wanless er al., 1989). Cores discussed in Part B are located. ACKNOWLEDGMENTS This research was supported by a grant from NOAA’s Coastal Ocean Program and the South Florida Ecosystem Restoration and Monitoring Program. Nu- merous people have improved this manuscript through thought-provoking discussions and comments. In par- ticular we would like to thank H. R. Wanless (Uni- versity of Miami), T. A. Nelsen (NOAA-AOML), A. D. Cohen, and FE J. Rich. D. W. Kuehn (University of Western Kentucky), P. G. Mueller and the Illinois State Museum generously provided reference sets of tropical pollen. Thanks to Everglades National Park, T. Ar- mentano, and W. Meshaka for permission to sample the vouchered herbarium at ENP and help in doing so. A. Vlad volunteered her time to help sample the her- barium. C. J. Ross helped computerize the reference set and the original data set. M. A. Capps helped es- tablish laboratory procedures for pollen preparation. STUDY AREA South Florida is part of the broad, Florida platform (Parker and Cooke, 1944). Although presently attached to the North American continent, the South Florida peninsula is a partly inundated carbonate platform re- moved from most continental influences (Wanless et al., 1989). Sea level has flooded the platform resulting in an expansive shelf margin to the west and a narrow, steep-sided margin to the south and east. The upper- most rock units in the study area are of Tertiary and Quaternary age (Puri and Vernon, 1959). The north- west portion of the study area is underlain by the Pli- ocene Tamiami Formation, a calcareous sandstone to sandy limestone (Parker and Cooke, 1944). The Big Cypress Ridge area is underlain by shallow reefal limestones of Pliocene age (Meeder, 1987). The re- maining portions of the study area are underlain by the Pleistocene Miami Oolite (Parker et al., 1955; Hoff- meister ef al., 1967). Unconsolidated Holocene sedi- ments blanket much of the bedrock surface. Holocene carbonate, organic and siliceous sediments of biogenic origin are forming and accumulating, and quartzose sands are being supplied by littoral transport and by dissolution of limestones (Wanless ef al., 1989). The gentle southerly slope of the bedrock surface results in an increase in the thickness of unconsolidated Holo- cene sediments seaward. Local differences in the thickness and distribution of Holocene sediments can be attributed, in part, to hydrologic and topographic variability in which the preexisting limestone surface plays a fundamental role (Wanless et al., 1995). PHYSIOGRAPHY The distribution of pre-Holocene bedrock highs and thick accumulations of Holocene sediments define the major physiographic provinces of the South Florida peninsula (Text-fig. 1). The Everglades depression ex- tends southward through the center of South Florida and is bounded by exposed Pliocene limestones of the Big Cypress Ridge to the west and the Pleistocene quartz sand and oolitic limestone of the Atlantic Coast- POLLEN ZONATION: O’ NEAL ET AL. 103 al Ridge to the east (Text-fig. 1). The broad Everglades depression carries fresh water flow southward from Lake Okeechobee to the sea via the Shark River Slough complex (Text-fig. 1). The Everglades depres- sion is underlain by Pleistocene lagoonal deposits termed the bryozoan facies of the Miami Limestone by Hoffmeister et al. (1967). The depression is choked with Holocene freshwater peat and calcitic mud de- posits (Wanless et al., 1989). A natural coastal dam of mangrove peat and storm-levee marl inhibits saline in- trusion into the depression. The oolitic limestone ridge of the Miami Limestone crests 2—6 m above sea level, extends north-south from north Miami to the south, where it then curves westward. The Atlantic Coastal Ridge is cross-cut by numerous fossil tidal channels. These channels form swales that are filled with quartz sand and peat and served as conduits for fresh water flow through the ridge prior to drawdown of Ever- glades water levels in the early 1900’s (Wanless et al., 1989). In addition to the physiographic units defined by Pliocene and Pleistocene ridges, Holocene sediment buildups generate coastlines and marine buildups which define the coastal complex. Along the northern shore of Florida Bay, transgressive to regressive coast- al storm levees of carbonate mud form the shoreline. Broad progradational peat and coastal sand and mud accumulations form a coastal mangrove forest and transitional marsh complex along the western shoreline (Wanless et al., 1995). The study area is characterized by elevations that are generally less than 0.3 m above mean sea level (MSL) (Spackman et al., 1966). In the area south of Lake Okeechobee, elevations are as much as 10 m above MSL and gently slope to the south (Spackman et al., 1966). Changes in topography, although subtle, are significant in that natural highs and lows strongly influence the depth of the water ta- ble, thickness of Holocene sediment, and the surface flow of water in a given area (Riegel, 1965). The pri- mary inputs of surface water to the study area are overflow from Lake Okeechobee and local rainfall. In the approximately 4000 sq. miles (6,400 km7?) of the Everglades depression, water moves as sheet flow (Spackman et al., 1966), although historically, human channelization of flow has disrupted the natural flow system to varying degrees (Mclvor et al., 1994; Smith et al., 1989). VEGETATION COMMUNITIES South Florida has a very distinct zonation of vege- tation that is strongly related to salinity, hydroperiod, elevation, and substrate (Riegel, 1965; Text-fig. 2). The boundaries between zones are usually abrupt (Co- hen, 1968) except in estuaries. Here, transitional com- » 84-€7 (SO+E): /) » 64-10 "s 54-16 (SG+E) AR HOR Al wh ; wy # 64:1680(SG¥E), 1151/11 v\ ay uJ 20 kilometers Mangrove Swamp (J Brackish Marsh (°] Freshwater Marsh with Cypress Hammocks EJ Freshwater Marsh (Slough) |} Freshwater Marsh with Hardwood Hammocks E] Beach Community - (i Flamingo Marl Prairie oe Bi Pine - Upland eee an (©) Hardwood Forest - Upland AREA | \, | Big Cypress Swamp - Upland d Text-figure 2.—Generalized vegetation map of southwest Florida showing the location of samples. SR samples are along the Shark River Slough complex. The 86 sample sites used for statistical anal- ysis are shown (modified from Riegel, 1965). munities occur where tidal channels and river systems compete for dominance of influence in a given area. Fires, hurricanes, droughts, floods, and freezing tem- peratures also control the distribution and extent of vegetation communities; however, the long-term ef- fects of such forces are not well understood (Olmstead and Loope, 1984; Gunderson and Snyder, 1992). Veg- etation communities in southwestern Florida, particu- larly in Everglades National Park, vary in complexity. Some communities are dominated by a few species, while others are composed of more complex mixtures with no truly dominant species. The vegetation com- munities used in this study were described by Riegel (1965) based on the work of Davis (1943) and Love- less (1959). Gunderson (1994) provided a detailed de- scription of freshwater marsh and tree island commu- 104 BULLETIN 361 nities, as well as upland vegetation. The spatial distri- bution of communities is shown in Text-figure 2. Coastal Mangrove Fringe (Mangrove Swamp) Mangrove forests of varying heights dominate the coastal margin of the study area. These forests are es- sentially a continuous cover of woody vegetation that is tolerant of high salinity and changes in hydroperiod related to inundation by tides. The forests produce root peat deposits that may develop into peat islands or shore-parallel wedges that are dissected by river chan- nels draining the Everglades Basin. The interior of these islands is commonly higher in elevation and de- velops into a saltwater marsh or coastal prairie sup- porting less water-tolerant woody species (Bancroft et al., 1994). Rhizophora (red mangrove), Avicennia (black mangrove) and Laguncularia (white mangrove) dominate the mangrove forest. Light gaps permit the growth of Batis (saltwort). The coastal levees of the mangrove swamp are capable of supporting a variety of upland vegetation. Prior to devastation by Hurricane Donna (1960), Avicennia forests were prevalent in the areas around Flamingo and the lower Shark River Slough (Craighead and Gilbert, 1962). These regrowth forests are now primarily composed of Rhizophora. Brackish and Headwater Marsh A brackish zone develops parallel to the coast where fresh water runoff from the mainland mixes with ma- rine waters of the Gulf and Florida Bay. The location and extent of this brackish transitional zone varies with tidal influences and seasonal changes in the amount of freshwater input. Physiographically, the vegetation communities of southwestern Florida are parallel to the coast consistent with the salinity gradient (Text-fig. 2). Two brackish transitional zones can be distinguished. One occurs parallel to the coast and away from the major freshwater outflow of the Shark River Slough. This brackish, transitional marsh is dominated by Rhi- zophora, Avicennia, Laguncularia, Typha (cattail), Spartina (eelgrass), and Cladium (sawgrass). A second transitional zone, the headwater marsh, occurs adjacent to the outflow of the Shark River Slough in the zone of fluctuating freshwater and marine influences. This area is dominated by a network of river channels of the Shark River Slough/Little Shark River complex. Vegetation in the area is a mixture of Rhizophora, Av- icennia, Laguncularia, Conocarpus (buttonwood), Spartina, Scirpus (bulrush), Typha, Cladium, and Myr- ica (wax myrtle) (Bancroft et al., 1994). Freshwater Marsh and Slough Environments Inland from the coastal bays, waters become fresher and mangrove communities diminish. These more in- land vegetation communities can once again be divid- ed based on species tolerance to fluctuations in salinity and hydroperiod. The freshwater areas can be divided into freshwater marsh—slough (the primary vegeta- tion-choked waterways developed in the Everglades Basin) and freshwater marsh with hammocks (tree is- lands). Sloughs and marshes are prairies of grasses and sedges that comprise the largest percentage of the freshwater area. Cladium, Eleocharis (spikerush), Pan- icum (maidencane), Muhlenbergia (Muhly grass) and Rhynchospora (beakrush) are the primary sedges and grasses. In the wetter slough areas, emergent aquatics also are abundant including Sagittaria (arrowhead), Nymphaea (water lily) and Utricularia (bladderwort) (Gunderson, 1994). In the freshwater marsh with ham- mocks, tree islands or hammocks commonly develop. Communities can be divided into Bayheads, Willow Heads, and Cypress Forests (Gunderson, 1994) and in- clude a diverse mixture of Persea (red bay), [lex (da- hoon holly), Anona (pond apple), Myrica (wax myr- tle), Salix (willow), Chrysobalanus (cocoplum), and Taxodium (bald cypress), in addition to numerous oth- er species that occur in low abundances. Upland Complex Toward the rim of the Everglades depression are bedrock highs on which pinelands and hardwood for- ests dominate. Pine uplands are found along the east- ern margin of the Everglades on the Atlantic Coastal Ridge and extend into Everglades National Park along limestone ridges (Gunderson, 1994). Rockland pine forests are dominated by monotypic stands of Pinus elliotti (slash pine). Additionally, an assortment of palms, including Sabal (cabbage palm) and Serenoa (saw palmetto) are common. Tropical hardwood hammocks occur on rock sub- strates most commonly in the southern Everglades. Quercus (live oak), Lysiloma (wild tamarind), Bursera (gumbo-limbo), and Swietenia (mahogany) are com- mon hammock species. In many areas, dense ham- mocks primarily comprised of the bald cypress Taxo- dium distichum have developed. Orchids, bromeliads, and ferns are also present, but are not abundant. PART A: CHARACTERIZATION OF MODERN POLLEN ZONES IN SOUTH FLORIDA FROM SURFACE POLLEN SAMPLES Data for the first part of this study, the delineation of contemporary pollen zones in South Florida, was obtained from Appendix II of Riegel (1965) who com- pleted the first extensive palynological analysis of Ey- erglades National Park. His objectives were effectively the same as ours: to determine the relationship be- tween pollen from surface sediments and the local POLLEN ZONATION: O’ NEAL ET AL. 105 plant communities of the same area, and to character- ize late Holocene ecological changes by comparing pollen preserved in sedimentary sequences with those found in the surface sediments. However, Riegel’s (1965) methods differ from ours. His data were pre- sented in a series of tables and abundance histograms designed to display the distribution of pollen and spores both at the surface and in sediment cores. His analysis focused on the means and variances of indi- cator species and their abundance. Results indicated, as expected, that the content of pollen assemblages was not directly proportional to the species composi- tion of the parent plant communities; however, depo- sitional environments could be recognized by pollen types that were transport-limited, and from vegetation communities restricted by salinity, hydroperiod, and elevation. The original data set is a matrix consisting of the percent frequency of 92 taxonomic and morphologic pollen and spore categories collected from 102 sample sites, representing six of the ten major vegetation com- munities presented in that report (Text-fig. 2). Riegel (1965) followed standard preparation procedures and counting was conducted on at least three slides per sample. For each site, Riegel (1965) attempted to count a minimum of 150 grains. Pollen was not abun- dant in some samples and, on occasion, counting was stopped after reaching a minimum of 100 grains. Sev- eral of Riegel’s (1965) samples taken from detrital sed- iments were removed from the data set for this study in order to restrict the analysis to samples from in situ depositional localities. The 92 taxonomic and morpho- logic categories in the original data set were reduced to 47 categories that could be associated with known parent plants present in surface vegetation communi- ties. Twelve samples were collected from the Joe River area along a transect less than 300 m long extending from the mangrove fringe into the transitional marsh of northwest Cape Sable. This represents a much great- er density of sites than for any of the other environ- ments sampled by Riegel (1965) in South Florida. In order to avoid biasing the present data set, only one sample, JR-1, was selected from the Joe River transect. The final data set consisted of 47 taxonomic and mor- phologic pollen and spore categories and 86 surface sampling sites (Text-fig. 2). Statistical Methods Two multivariate statistical methods, cluster analysis and discriminant analysis, were applied to the data. Cluster analysis is a technique that classifies samples or taxa into relatively homogenous groups based on inter-object similarities (Davis, 1986; Kachigan, 1991). Two separate cluster analyses were used; one for as- sociations of pollen and spores (taxonomic) and the other for surface sample associations (environmental). A hierarchical clustering technique, using Ward’s sum of squares linkage method (Ward, 1963) and Chi- squared distances, were used in each analysis. Ward’s method, which sums the squared Euclidean distances between each sample and the cluster means, is the pre- ferred linkage technique because at each stage in the cluster analysis two samples or clusters are merged in a manner that arrives at the lowest within-group sum of square totals (Davis, 1986; Kachigan, 1991). All statistical calculations presented in this study were per- formed using SYSTAT version 6.0 (SPSS Inc., 1996). Cluster analysis produces a dendrogram with objects (i.e., samples or taxa) on the vertical axis and a dis- tance measurement that defines where clusters join on the horizontal axis. Any vertical slice through the den- drogram should produce distinct groups that have maximized inter-object similarities. The statistical va- lidity of the groups obtained from cluster analysis of surface samples was tested using discriminant analysis. Discriminant analysis evaluates the distinctiveness of predefined groups by calculating discriminant func- tions representing a linear combination of measured variables (Davis, 1986). Likewise, discriminant func- tion scores are calculated for each sample by trans- forming the original set of measurements into a single value on each function. The mean, variance, and con- fidence intervals for function scores were calculated for each group and used to evaluate the distinctiveness of cluster-generated groupings. Function coefficients are calculated for each variable in the data set (i.e., taxa) permitting the identification of variables that most strongly contribute to group separation along each function. Results for Surface Samples Cluster Analysis of Taxa The dendrogram from cluster analysis of the 47 pol- len and spore categories can be divided into four clus- ter groups (Text-fig. 3). Cluster A is further divided into three sub-clusters. Cluster Al contains Rhus, Sphagnum, Caryophyllaceae, Fraxinus, Eugenia, Car- ya, Rhabdadenia, Ericaceae, Hamelia, Ulmus, Pteris, Rapenea, cf. Thomsonopollis, Nyssa, Myrtaceae, Nu- phar, Ficus, Polygona, Morus, and Alnus. Cluster A2 contains Sapotaceae, Vitis, Ilex, Anacardium, and Os- munda. Cluster A3 contains Compositae, Quercus, Ty- pha, Gramineae, Salix, Cephalanthus, Polypodium, and Taxodium. Cluster B contains chenopods. Cluster C contains triporates, Cyperaceae, Sagittaria, Utricu- laria, Umbelliferae, cf. Ovoidites, Nymphaea, and Pi- 106 BULLETIN 361 Table 1.—Southwestern Florida surface pollen and spore data arranged by environmental cluster groupings. Data from Riegel (1965) are percentage abundance of the original sample. All samples do not total 100% because of the exclusion of taxonomic/morphologic categories that could not be associated with known parent vegetation. Average (Avg.), standard deviation (st. dev.), and 95% confidence intervals (CI) are presented for each cluster group. Lagun- Cheno- Site Cluster = Rhizophora Avicennia cularia Conocarpus _ Batis pods Gramineae Cyperaceae Mangrove Swamp (N = 10) 62-01 1 58.7 7.3 0.7 3, 0.0 7.4 0.0 0.7 62-06 1 Si/ 5.4 0.0 4.2 1.8 7.8 ile? 0.6 62-08 1 64.0 3.1 1.2 Bh 3.1 6.1 0.0 0.0 62-11 1 63.5 0.0 0.6 1.8 2.4 6.0 0.0 0.0 62-12 1 66.1 0.0 DS 0.0 0.6 4.3 0.6 0.6 62-15 1 58.7 0.6 1.2 4.3 0.6 11.8 0.6 1.2 62-17 1 61.0 1.8 1e2 0.6 0.6 7.9 0.0 0.6 62-20 1 56.0 33 DD, 2.2 1.6 4.9 0.0 eit 62-21 1 43.7 7.6 PPS) 6.3 P25) 8.3 0.0 1.3 62-22 1 46.9 Ue 1.7 0.6 ed 2.8 0.6 67/ Avg. 57.4 3.0 1. 3.0 5 6.7 0.3 0.8 Stdev. 73 2.9 0.8 2.5 1.0 2.5 0.4 0.5 Cl 4.5 1.8 0.5 1.5 0.6 1.6 0.3 0.3 Mangrove Swamp (N = 15) 62-02 2 16.6 9.6 0.0 Se) 29.6 25.8 1.0 0.0 62-03 2 29.4 2) 0.5 S5f/ 10.8 28.4 2.1 0.0 62-05 2 Dilee 9.5 1.2 4.7 si 21.9 1.2 0.0 62-07 2 34.3 1.2 1.2 5.4 4.2 18.1 2.4 0.0 62-09 2 38.9 Spl 0.6 Su7/ 3.8 10.2 3} 1153} 62-10 2 43.5 2.0 1.3 2.0 0.0 11.7 1.3 1.3 62-13 2 37/3) 33 1.3 3:9 1.3 hil 0.7 0.0 62-14 2 39.6 45 1.1 2.3 177 10.8 ileal 1 62-18 2 49.0 1:9 3.9 32 2.6 8.5 0.0 0.7 62-19 2 25.1 6.7 1.7 1.7 0.0 10.7 1.1 tl 64-11 2 11.7 0.6 SE 1.8 0.0 12.2 19) 4.3 64-21 2 19.8 IEG 16.4 11.8 0.0 519) 0.9 0.0 SR-O1 2 37.5 ils) 1.3 3.3 319 8.5 0.0 0.7 SR-02 2 32.3 6.2 12. 2.3 3.5 IS\-2? 0.0 0.0 59-T1 2 30.7 6.1 8.9 2.4 0.0 9.2 1.2 0.0 Avg 31.5 4.3 3.0 4.1 4.6 14.0 1.0 0.7 Stdev 10.2 2.9 4.3 2.6 7.6 6.7 0.7 1.1 CI 5:2 1.5 2.2 1.3 3.8 3.4 0.4 0.6 Mangrove Swamp (N = 11) SR-03 3 44.4 Dei, 0.9 14.2 1.3 ile 0.0 0.0 SR-04 3 40.9 3i2 1:9 11.1 19 6.7 0.0 0.9 SR-05 3} 32.6 0.0 1.1 4.9 0.0 23.9 0.0 0.5 SR-06 3 33.5 ier 3 6.5 0.0 79) 0.3 1.4 SR-07 3} 3257 0.3 0.6 8.0 0.3 95 0.0 0.6 SR-09 3 52.4 2.9 1.3 6.8 0.3 6.5 0.0 0.7 SR-10 3 36.2 0.9 1.9 S57] 0.0 18.1 0.0 0.0 SR-13 3 13.6 0.0 1.1 8.2 1.1 315)-3) 0.0 0.5 SR-14 3 13.5 2.4 0.6 1229 0.0 21.2 0.6 2.4 SR-15 3 36.9 0.0 1.9 25 0.0 18.1 0.6 0.6 SR-16 3 29.1 0.0 0.7 iTh,3) 0.0 8.6 0.7 2.0 Avg 33.3 1.2 1.1 8.4 0.4 16.1 0.2 0.9 Stdev 11.7 1.3 0.5 3.6 0.7 8.8 0.3 0.8 CI 6.9 0.8 0.3 2.1 0.4 $.2 0.2 0.5 Freshwater Marsh (N = 9) 62-34 4 1.2 0.0 0.6 12 0.6 2.9 75 6.4 64-04 4 0.5 0.0 0.0 0.5 0.0 2.8 4.2 2.8 64-07 4 0.0 0.0 0.0 0.4 0.0 4.3 22, 3.0 64-E7SG 4 0.0 0.0 0.0 0.0 0.0 13:9 12 5.2 64-09 4 1.2 0.0 0.0 0.0 0.0 8.8 Ps) 73) 64-15 4 0.0 0.0 0.0 0.5 0.0 16.9 1.4 5.5 64-16SG 4 0.0 0.0 0.0 0.5 0.0 7.4 2.1 6.4 SLTR-03 4 0.0 0.0 0.0 0.0 0.0 eS) 1.4 Tes SLTR-04 4 0.0 0.0 0.0 1.0 0.0 13.1 0.0 4.7 Avg. 0.3 0.0 0.1 0.5 0.1 Chi7/ 2.5 6.0 Stdey. 0.5 0.0 0.2 0.4 0.2 5.8 2.2 2.8 io) L ol —) i2*) i—) - = w — -_ i) ie) _ = _— oo Table |.—Extended. Typha Nym- phaea Sagit- taria POLLEN ZONATION: O'NEAL ET AL. 107 Caryo- Umbel- Utricu- Com- Poly- phylla- Trip- Eu- Cephal- Frax- Sapot- liferae laria positae gona ceae_ Ilex Salix Morus Ficus orates genia anthus inus — aceae 0.0 0.0 2A 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.6 0.0 S7/ 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 3.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 3.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 6.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.0 2.9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.0 1.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.8 0.0 0.0 0.6 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.6 0.0 12. 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2a 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.7 0.0 0.0 3:3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 No 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.6 0.0 0.0 0.0 0.7 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 9.6 0.0 0.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.6 0.0 0.6 0.0 2 0.0 0.0 0.0 0.0 0.0 0.0 Sal 0.0 0.5 0.5 0.0 0.4 0.0 1.8 0.0 0.0 0.0 0.0 0.0 0.0 ile7/ 0.4 0.0 0.0 0.0 0.0 0.0 0.6 0.0 0.7 0.0 0.7 0.0 0.0 2.0 0.0 0.0 0.0 0.0 0.9 0.0 2.4 0.0 0.4 0.0 0.0 0.0 0.0 3.9 0.0 0.0 0.0 0.0 0.6 0.0 3.0 0.0 0.0 0.6 0.0 0.6 0.6 1.9 0.0 0.0 0.0 0.6 0.2 0.0 1.9 0.0 0.1 0.0 0.0 0.0 0.0 0.9 0.0 0.0 0.1 0.1 0.3 0.0 2.3 0.0 0.2 0.2 0.2 0.2 0.2 1.3 0.1 0.1 0.2 0.2 0.2 1.2 0.1 0.1 0.1 0.1 0.1 0.7 0.1 0.1 0.1 0.1 0.0 0.0 0.8 0.0 0.0 0.0 0.0 0.0 0.0 4.8 0.0 0.0 0.0 0.0 0.3 0.0 1.8 0.0 0.0 0.3 0.0 0.0 0.0 4.4 0.0 0.0 0.0 0.3 0.0 0.0 4.2 0.0 0.0 0.0 0.0 0.0 0.0 3.8 0.0 0.0 0.0 1.1 0.3 0.3 3.0 0.0 0.0 0.0 0.0 0.0 0.3 5.4 0.0 0.0 0.0 0.0 0.3 0.0 0.6 0.0 0.0 0.0 0.3 0.0 0.3 5.4 0.0 0.0 0.0 0.0 0.3 0.0 33) 0.0 0.0 0.0 0.0 0.0 0.0 SiS) 0.0 0.0 0.0 0.0 0.0 0.0 3.8 0.0 0.0 0.0 0.0 0.0 0.0 2.9 0.0 0.0 0.0 0.0 0.0 0.5 2.0 0.0 0.0 0.0 0.5 0.0 0.0 4.3 0.0 0.0 0.0 0.0 0.0 0.0 3.0 0.6 0.0 0.6 0.0 0.0 0.0 S)) 0.0 0.0 0.0 0.0 0.0 0.0 0.6 0.0 0.0 0.0 0.0 0.0 0.6 8.1 0.0 0.0 0.0 0.0 0.0 0.0 1.4 0.0 0.0 0.7 0.0 0.0 0.0 IS) 0.0 0.0 0.0 0.0 0.1 0.1 2.2 0.1 0.0 0.1 0.1 0.0 0.1 Seo) 0.0 0.0 0.0 0.1 0.2 0.2 1.3 0.2 0.0 0.3 0.2 0.0 0.2 3.0 0.0 0.0 0.0 0.3 0.1 0.1 0.8 0.1 0.2 0.1 0.1 1.8 0.2 0.6 0.0 4.0 0.6 0.0 0.6 0.0 Pee) 0.0 17.9 0.0 0.0 0.0 le7/ 0.5 0.0 See 0.0 0.0 0.0 0.9 0.0 0.0 9.9 0.0 0.0 0.5 0.0 1.3 0.9 2.5 0.0 0.0 0.0 0.4 0.0 0.0 8.7 0.4 0.4 0.0 0.0 od N72 0.6 0.0 0.0 0.0 0.0 0.0 0.0 12a 0.0 (leg 0.0 0.0 1.2 1.8 2.9 0.0 0.0 1.2 1.2 0.0 0.0 9.4 0.0 12 0.0 0.0 0.9 0.9 2.3 0.0 0.0 0.5 0.5 0.0 0.0 6.9 0.0 0.9 0.0 0.0 2.1 0.5 Dr 0.0 0.0 0.5 0.0 0.0 0.5 2Ae2 0.0 0.0 0.0 0.0 0.0 0.0 0.9 0.0 0.0 0.0 0.0 0.5 0.0 Tell 0.0 0.5 0.0 0.0 0.0 1.0 0.5 0.0 0.0 0.0 1.0 0.0 0.0 11.5 0.0 0.5 0.0 0.0 0.9 0.7 2.2 0.1 0.0 0.3 0.4 0.3 0.1 11.7 0.0 0.6 0.1 0.2 0.7 0.6 1.2 0.2 0.0 0.4 0.5 0.8 0.2 4.8 0.1 0.6 0.2 0.6 0.5 0.4 0.8 0.1 0.3 0.3 0.5 0.1 3.1 0.1 0.4 0.1 0.4 108 BULLETIN 361 Table 1.—Continued. Anacar- cf. Ovoidi- Site Cluster Quercus dium Alnus Carya Nyssa Taxodium tes Vitis Rapenea Mangrove Swamp (N = 10) 62-01 1 0.0 ils) 0.0 0.0 0.0 0.7 0.0 0.0 0.0 62-06 1 1:2 5.4 0.0 0.0 0.0 1.2 0.0 0.0 0.0 62-08 1 1.2 0.0 0.0 0.0 0.0 2.4 0.0 0.0 0.0 62-11 1 0.0 2.4 0.0 0.0 0.0 3.0 0.0 0.6 0.0 62-12 1 0.0 1.2 0.0 0.0 0.0 2.5 0.0 0.0 0.0 62-15 1 1.2 0.0 0.0 0.0 0.0 0.6 0.0 0.0 0.0 62-17 ! 0.0 0.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 62-20 1 0.0 1.2 0.0 0.0 0.0 1.6 0.0 0.0 0.0 62-21 1 1.9 0.0 0.0 1.3 0.0 3.2 0.0 0.6 0.0 62-22 1 0.0 0.0 0.0 0.0 0.0 1.1 0.0 0.0 0.0 Avg. 0.6 1.2 0.0 0.1 0.0 1.6 0.0 0.1 0.0 Stdev. 0.7 1.7 0.0 0.4 0.0 1.1 0.0 0.3 0.0 cI 0.5 1.0 0.3 0.7 0.2 Mangrove Swamp (N = 15) 62-02 2 0.5 1.2 0.0 0.0 0.0 0.2 0.0 0.0 0.0 62-03 2 0.0 0.0 0.0 0.0 0.0 2.1 0.0 0.0 0.0 62-05 2 3.0 1.8 0.0 0.0 0.0 0.5 0.0 0.0 0.0 62-07 2 0.0 0.0 0.0 0.0 0.0 2.4 0.0 0.0 0.0 62-09 2 13 1.3 0.6 0.0 0.0 1.3 0.0 0.0 0.0 62-10 2 1.4 0.7 0.7 0.1 0.0 1.3 0.0 0.0 0.0 62-13 2 4.0 2.6 0.7 0.0 0.0 0.0 0.0 0.7 0.0 62-14 2 2.3 1.1 0.0 0.0 0.0 1.7 0.0 0.0 0.0 62-18 2 3.9 0.0 0.0 0.0 0.0 4.5 0.0 0.0 0.0 62-19 2 4.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 64-11 2 DES 0.6 0.0 0.0 0.0 2.5 0.6 0.0 0.0 64-21 2 Del 0.0 0.0 0.0 0.0 0.0 0.9 0.0 0.0 SR-O1 2 1.3 0.0 0.0 0.0 0.0 3:3 0.0 0.0 0.0 SR-02 2 4.3 0.4 0.8 0.0 0.0 0.4 0.4 0.0 0.0 59-T1 2 3:5 1.2 0.0 0.0 0.0 2.5 0.0 0.0 0.0 Avg. 2.2 0.7 0.2 0.0 0.0 cs 0.1 0.0 0.0 Stdev 1.7 0.8 0.3 0.0 0.0 1.4 0.3 0.2 0.0 CI 0.7 0.4 0.2 0.0 0.7 0.1 0.1 Mangrove Swamp (N = 11) SR-03 3 0.9 0.0 0.0 0.0 0.0 0.0 0.9 0.0 0.0 SR-04 3 322 0.0 0.0 0.0 0.0 0.3 0.6 0.0 0.0 SR-05 3 1.0 0.5 0.5 0.0 0.0 0.6 0.0 0.0 0.0 SR-06 3 2 0.3 0.0 0.0 0.0 0.6 1.7 0.0 0.0 SR-07 3 2.1 0.0 0.0 0.0 0.0 0.9 1.2 0.0 0.0 SR-09 3 0.3 0.0 0.0 0.0 0.0 0.0 1.3 0.0 0.0 SR-10 3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 SR-13 3 Del 0.0 0.0 0.0 0.0 1.1 0.0 0.5 0.0 SR-14 3 1.2 0.0 0.0 0.0 0.0 1.2 0.0 0.0 0.0 SR-15 3 0.6 0.0 0.0 0.0 0.0 1.3 0.0 0.0 0.0 SR-16 3 0.7 0.0 0.7 0.0 0.0 1.3 0.7 0.0 0.0 Avg 1.4 0.1 0.1 0.0 0.0 0.7 0.6 0.0 0.0 Stdev 1.1 0.2 0.2 0.0 0.0 0.5 0.6 0.2 0.0 CI 0.6 0.1 0.1 0.3 0.4 0.1 Freshwater Marsh (N = 9) 62-34 4 il-72 0.6 0.6 0.0 0.0 il -72 2.9 1.7 0.0 64-04 4 Shr 0.0 0.0 0.0 0.0 3.8 15.0 0.0 0.0 64-07 4 13 0.4 0.4 0.0 0.0 EY 10.3 0.0 0.0 64-E7SG 4 1.2 0.0 12 0.0 0.0 2.3 8.7 0.0 0.0 64-09 4 2.4 0.6 0.0 0.0 0.0 53) 15.8 1.2 1.2 64-15 4 1.0 0.0 0.0 0.0 0.0 1.4 12.8 0.0 0.0 64-16SG 4 0.5 0.0 0.5 0.0 0.0 0.5 iL? 0.0 0.0 SLTR-03 4 0.9 0.9 0.0 0.0 0.0 1.8 8.2 0.0 0.0 SLTR-04 4 1.0 0.0 0.0 0.0 0.0 Sell 5.8 0.0 0.0 Avg 1.4 0.3 0.3 0.0 0.0 2.3 10.1 0.3 0.1 Stdev. 0.8 0.4 0.4 0.0 0.0 1.5 4.2 0.7 0.4 o) L al = a — iv = ta cme —) iS) Q S os o w Hame- lia 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Rhus 0.7 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.2 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 cil 0.0 0.0 0.0 0.0 0.0 0.1 0.3 0.1 0.0 0.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.1 0.0 0.0 0.0 0.0 0.0 POLLEN ZONATION: O’NEAL ET AL. 109 Table 1.—Continued Extended. cf. Grains Thom- Rhab- Grains used Myrt- Poly- Eric- Sphag- sono- daden- Liquid- count- for aceae Osmunda podium — aceae num Ulmus pollis Nuphar ia Pteris amber Pinus Other ed Stats 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2.0 10.1 150 133 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 6.6 De) 167 156 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 4.3 8.7 164 148 0.0 0.0 0.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Te? 8.5 167 151 0.0 0.0 ibs) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 10.5 Tell 162 149 0.0 0.0 ed, 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 8.0 4.7 162 153 0.0 0.0 2, 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Ue) 12.6 164 142 0.0 0.0 0.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 15.8 4.6 184 174 0.0 0.6 1.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 3.8 10.9 158 139 0.0 0.0 igi 0.0 0.6 0.0 0.0 0.0 0.0 0.0 0.0 20.7 ily 179 156 0.0 0.1 0.7 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0 8.7 9.4 0.0 0.2 0.6 0.0 0.2 0.0 0.0 0.0 0.0 0.0 0.0 5.7 69.0 0.1 0.3 0.1 3.5 80.8 0.0 0.5 0.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 3yS) 0.5 591 576 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 8.8 4.5 194 181 0.0 0.6 0.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 8.9 OD n/a n/a 0.0 2 0.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 9.0 16.2 166 136 0.0 0.0 1.9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 18.9 15.2 157 130 0.0 0.7 2.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 16.2 7.6 154 139 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 14.4 10.7 153 134 0.0 1.7 2.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 15.3 8.5 177 158 0.0 0.0 0.7 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 13.6 3.4 155 147 0.0 0.0 0.0 0.0 0.6 0.0 0.0 0.0 0.0 0.0 0.0 27.4 6.6 179 164 0.0 Sul 3.1 0.0 0.0 0.0 0.0 0.6 0.0 0.0 0.0 6.8 36.1 n/a n/a 0.0 18.1 0.9 0.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 9.4 4.1 23 223 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 17.8 15.1 52 26 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 15.2 7.4 25 233 0.0 1.8 1.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 S33 5.1 163 SI! 0.0 1.8 0.9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 12.8 12.1 0.0 4.6 1.0 0.1 0.2 0.0 0.0 0.2 0.0 0.0 0.0 5.6 41.0 2.3 0.5 0.1 0.1 0.1 2.8 70.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 8.0 7.0 225 203 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 11.4 6.9 315 284 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 12.5 8.8 184 162 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 12.5 6.4 352 319 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 8.6 25.3 336, 241 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 10.4 4.3 307 285 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 7.6 199) 105 81 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 17.3 We? 184 165 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 8.8 OKT, 170 131 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 6.3 18.3 160 126 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 O33 14.5 151 125 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 10.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 3.1 1.8 0.0 0.0 L7/ 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 13.9 25:9) 17/3) 121 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 25.4 0.9 213 139 0.0 0.0 3.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 47.8 49.2 232 109 0.0 Shs) 35 0.0 0.0 0.6 0.0 0.0 0.0 0.0 0.0 33.5 35.0 173 106 0.0 0.0 1.8 0.0 0.0 0.0 0.6 0.0 0.0 0.0 0.0 17.0 13.1 171 142 0.0 0.9 1.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 32.4 38.2 219 127 0.0 1.0 2.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 22.9 25.2 218 154 0.0 6.3 Drill 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 28.2 30. 220 145 0.0 2.6 3.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 33.5 36.7 213 126 0.0 1.6 2.3 0.0 0.0 0.1 0.1 0.0 0.0 0.0 0.0 28.3 0.0 2.2 1.2 0.0 0.0 0.2 0.2 0.0 0.0 0.0 0.0 10.1 1.4 0.8 0.1 0.1 6.6 110 BULLETIN 361 Table 1.—Continued. Lagun- Cheno- Site Cluster = Rhizophora Avicennia cularia Conocarpus _ Batis pods Gramineae Cyperaceae Freshwater Marsh (N = 8) 62-23 5 0.6 0.0 0.0 0.0 0.0 34.8 0.0 5.6 64-E7E 5) 0.0 0.0 0.0 0.0 0.0 Bye. 1.0 1S 64-10 5 0.0 0.0 0.0 0.0 0.0 33.8 0.0 3.6 64-16E 5 0.0 0.0 0.0 0.6 0.0 eT 0.0 By) 64-16ASG 5) 0.0 0.0 0.0 0.0 0.0 47.2 0.5 1.8 64-16AE 5 il 0.0 0.0 0.0 0.0 Syileil 1.2 122) SLTR-O1 5) 0.4 0.0 0.0 0.0 0.0 22.9 3a 1.9 SLTR-02 5) 0.5 0.0 0.0 0.0 0.0 Dial 0.5 31) Avg. 0.3 0.0 0.0 0.1 0.0 32.7 0.8 Del Stdev. 0.4 0.0 0.0 0.2 0.0 7.5 1.0 1.5 cI 0.3 0.1 S52 0.7 1.0 Headwater Marsh (N = 5) 64-33 6 0.0 3.4 0.0 0.6 16.2 62.1 0.0 0.6 SR-25 6 0.5 0.0 0.3 0.0 0.0 80.5 0.3 2.1 SR-26 6 0.9 0.0 0.0 0.0 0.0 78.4 0.0 3 SR-28 6 0.4 0.0 0.4 0.0 0.0 70.6 0.0 0.4 SR-29 6 1.3 0.3 0.0 0.0 0.0 89.9 0.0 0.3 Avg 0.6 0.7 0.1 0.1 3.2 76.3 0.1 0.9 Stdev 0.5 1.5 0.2 0.3 72 10.5 0.1 0.8 CI 0.4 1.3 0.2 0.2 6.4 9.2 0.1 0.7 Headwater Marsh (N = 10) 62-24 7 2.3 0.0 0.0 0.0 0.0 37.3 2.3 1.7 SR-17 7 18.2 iNet 0.0 1.7 0.0 22K 0.6 Ne7/ SR-18 7 24.4 0.0 0.0 3.6 0.6 31.5 0.0 4.2 SR-19 7 11.0 0.5 1.0 4.0 0.0 33.0 0.0 3.0 SR-20 7 20.1 0.7 0.0 2.0 0.0 22.8 0.0 0.7 SR-21 7 28.7 0.5 0.5 1.1 0.0 23.2 0.0 1.1 SR-22 7 8.9 0.0 0.0 0.0 0.0 47.3 0.0 0.8 SR-23 7 15.4 1.1 0.0 0.0 0.5 44.0 0.0 22. SR-24 7 6.8 0.9 0.0 0.9 0.0 47.7 0.0 1.4 SR30 Ti 25.6 1.8 0.6 1.2 0.0 14.9 0.0 1.8 Avg 16.1 0.7 0.2 1.5 0.1 32.4 0.3 1.9 Stdev 8.8 0.6 0.4 1.4 0.2 11.5 0.7 1.1 CI 5.4 0.4 0.2 0.9 0.1 Aoi 0.5 0.7 Brackish Marsh (N = 9) 62-25 8 7.9 0.0 0.0 3.4 0.0 11.9 0.0 4.5 62-30 8 7.0 0.0 0.0 10.2 0.6 8.3 1.3 8.9 64-18 8 9.5 0.0 0.0 1.1 1.6 10.6 2.0 16.4 64-22 8 2.3 0.0 0.6 1.1 il57/ 5.6 0.5 17.0 HR-O1 8 12.2 0.0 0.0 19.1 0.9 73 1.9 0.9 HR-02 8 16.0 0.6 1.9 13.5 0.6 7.0 1.9 1.9 JR-O1 8 3.7 0.0 0.7 4.1 0.0 4.8 0.0 3.0 TB-O1 8 16.9 0.0 0.0 4.5 atl 19.1 0.6 11.2 TB-02 8 16.4 0.0 0.0 3.0 0.0 9.7 7 8.5 Avg 10.2 0.1 0.4 6.7 0.7 9.4 4.2 8.0 Stdev fs) 0.2 0.6 6.2 0.7 4.3 9.5 6.0 CI 3.6 0.1 0.4 4.1 0.4 2.8 6.2 3.9 Brackish Marsh (N = 5) 62-26 9 1.3 0.0 0.0 1133 0.0 6.3 1.3 2S 62-33b 9 0.0 0.0 0.0 0.9 0.9 0.9 0.0 2.8 62-35 9 0.0 0.0 0.0 0.5 0.0 0.5 0.0 1.6 64-09H 9 0.0 0.0 0.0 0.0 0.0 15.1 0.6 35 64-14 9 2, 0.0 0.0 0.0 1.2 3.6 2.4 3.6 Avg. 0.5 0.0 0.0 0.5 0.4 55) 0.9 2.7 Stdev 0.7 0.0 0.0 0.6 0.6 6.0 1.0 0.7 CI 0.6 0.5 0.5 5.2) 0.9 0.7 Upland (N = 4) 62-27 10 0.0 0.0 0.0 0.0 0.0 ite 0.6 isi 62-28 10 0.6 0.0 0.0 0.6 0.0 12 3.8 3.8 62-29 10 0.6 0.0 0.0 0.0 0.0 lez 0.0 0.0 EE-11 10 0.0 0.0 0.0 0.0 0.0 0.6 0.6 4.1 Avg. 0.3 0.0 0.0 0.2 0.0 1.2 1.3 2.3 Stdev. 0.3 0.0 0.0 0.3 0.0 0.5 1.7 2.0 POLLEN ZONATION: O’ NEAL ET AL. 111 Table 1.—Continued Extended. Caryo- Nym- Sagit- Umbel-Utricu- Com- Poly- phylla- Trip- Eu- Cephal- Frax- Sapot- Typha phaea taria liferae laria positae gona ceae_ Ilex Salix Morus Ficus orates genia anthus inus — aceae 0.6 ls7 Ded, 0.0 0.0 0.6 0.0 0.0 0.0 0.0 0.0 0.0 9.0 0.6 0.0 0.0 0.0 0.0 S)5) 3.0 0.3 1.3 0.6 0.3 0.0 0.0 0.3 0.0 0.0 3.0 0.0 0.0 0.0 0.0 0.5 4.1 0.5 1.0 0.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 6.7 0.0 0.0 0.0 0.0 0.0 9.0 12 0.6 1.9 0.6 0.0 0.0 0.0 0.0 0.6 0.0 135 0.0 0.0 0.0 0.0 0.0 5.0 2.3 0.0 0.5 0.0 0.0 0.0 0.0 0.0 0.0 0.5 2.8 0.0 0.5 0.0 0.5 0.8 12.0 5.0 0.4 0.4 2.0 0.0 0.0 0.0 0.4 0.0 0.0 2 0.0 0.0 0.0 0.0 OOF 253 1.0 0.4 0.4 il) 0.0 0.0 0.0 0.0 0.0 0.0 0.8 0.0 0.0 0.0 2.8 0.0 14.7 5.0 0.5 0.5 2.7 0.0 0.0 0.0 0.0 0.0 0.0 6.9 0.0 0.5 0.0 0.0 0.2 9.6 2.5 0.4 0.7 1.0 0.0 0.0 0.0 0.1 0.1 0.1 5.5 0.1 0.1 0.0 0.4 0.3 Tet 1.7 0.3 0.6 1.0 0.1 0.0 0.0 0.2 0.2 0.2 4.4 0.2 0.2 0.0 1.0 0.2 5.3 1.2 0.2 0.4 0.7 0.1 0.1 0.1 0.1 3.0 0.1 0.2 0.7 0.6 0.0 0.0 0.0 0.0 4.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.3 0.8 5.9 0.0 0.0 0.0 0.5 0.0 0.0 0.0 0.0 0.0 Dell 0.0 0.0 0.0 0.0 0.4 0.4 3.0 0.4 0.0 0.8 0.0 0.0 0.0 0.0 0.0 0.4 319 0.0 0.0 0.0 0.0 0.0 0.8 225 0.0 0.0 1.6 0.0 0.0 0.0 0.0 0.0 0.0 ie? 0.0 0.4 0.0 0.0 0.0 0.0 2.9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.6 0.0 0.3 0.0 0.0 0.3 0.4 2.9 0.1 0.0 1.3 0.1 0.0 0.0 0.0 0.0 0.1 2.0 0.0 0.1 0.0 0.0 0.3 0.4 2.1 0.2 0.0 1.7 0.2 0.0 0.0 0.0 0.0 0.2 1.4 0.0 0.2 0.0 0.0 0.2 0.4 1.8 0.2 1.5 0.2 0.2 1.3 0.2 23 lev 1.0 1.3 0.0 10.3 0.0 0.0 0.3 ile4/ 0.0 0.0 lea 0.0 1.0 0.0 0.0 0.0 23 1.7 0.0 0.0 2.4 0.0 0.0 1.1 0.6 0.0 0.0 20.4 0.0 0.0 0.0 0.0 0.0 0.0 i) 0.0 0.0 3.6 0.0 0.0 0.0 0.0 0.0 0.0 Hell 0.0 0.0 0.0 0.0 0.0 1.0 2:5 0.0 0.5 2.0 0.0 0.0 0.5 0.5 0.5 0.0 ae) 0.0 0.5 0.0 0.0 0.0 1.3 13, 0.0 0.0 4.2 0.0 0.7 0.0 0.0 0.0 0.0 11.4 0.0 0.0 0.7 0.0 0.5 1.1 1.1 0.0 0.0 5.4 0.0 0.0 0.6 0.0 0.6 0.0 10.3 0.0 0.0 0.6 0.0 0.0 Med 1.1 0.0 0.0 5.6 0.0 0.0 1.1 0.0 0.0 0.0 12.4 0.0 7 0.0 0.0 0.5 0.0 1.6 0.5 0.0 1.0 0.0 0.0 0.5 1.6 0.0 0.0 9.3 0.5 0.0 0.5 0.0 0.9 0.5 3.6 0.9 0.5 2.8 0.5 0.0 1.4 0.0 0.0 0.0 8.2 0.5 0.5 0.5 0.0 0.6 0.6 0.6 0.0 0.0 1.2 0.0 0.0 0.6 0.0 0.0 0.0 12.5 0.0 125) 0.0 0.0 0.5 1.0 1.6 0.3 0.1 3.9 0.1 0.1 0.6 0.4 0.1 0.0 10.9 0.1 1.6 0.2 0.0 0.7 0.8 0.9 0.5 0.2 2.8 0.2 0.2 0.5 0.7 0.2 0.0 4.1 0.2 3.9 0.3 0.0 0.4 0.5 0.5 0.3 0.1 1.7 0.1 0.1 0.3 0.4 0.1 2.5 0.1 2.4 0.2 0.0 0.0 0.0 0.0 1.8 0.0 0.0 2.8 0.0 0.0 ei 17.6 0.0 ite 0.0 0.6 0.0 0.0 0.0 0.0 6.4 0.0 0.0 0.0 0.6 0.0 0.6 14.6 0.0 0.0 0.0 0.0 1.6 0.0 0.0 0.0 0.0 4.2 0.0 0.0 0.5 0.5 1.1 0.5 ules 0.0 0.0 0.0 0.0 0.0 0.6 0.6 0.6 0.0 2.8 0.0 0.0 1.1 0.6 0.0 0.0 20.9 0.0 0.0 0.4 0.0 0.0 0.0 0.9 0.0 0.0 4.4 0.0 0.0 0.9 0.9 0.0 0.9 19.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 7.0 0.0 0.0 1.3 0.6 0.0 0.0 22.4 0.0 0.0 0.0 0.0 0.0 0.0 0.4 0.0 0.0 7.4 0.0 0.0 4.1 0.0 0.0 0.0 23.3 0.7 0.0 0.0 0.0 0.0 0.6 0.0 0.0 3.4 0.0 0.6 0.6 0.0 0.0 0.6 17.4 0.0 0.6 0.0 0.0 a3) 0.0 0.6 0.0 0.0 1.8 0.0 0.0 2.4 0.6 0.0 0.0 20.6 1.3 0.0 12; 0.0 0.0 0.0 1.9 19) 0.0 12.6 0.6 0.0 0.0 1.3 0.0 0.0 5.0 0.0 8.2 0.0 0.0 0.0 0.0 0.0 eS) 0.0 4.7 0.9 0.0 0.0 1.9 0.0 1.9 3.8 0.0 19) 0.0 18.8 1.6 0.0 1.1 0.0 0.0 12.7 0.0 0.0 0.0 9.5 0.5 0.0 0.5 0.0 0.5 0.0 0.0 0.6 0.0 1S) 0.6 0.0 6.9 0.6 0.0 0.0 26.4 0.0 0.6 14.5 0.0 2.5 0.0 0.0 0.0 0.6 8.3 7A 0.6 3.6 0.0 0.0 0.0 3.0 0.0 0.0 4.2 0.0 27.4 0.0 0.0 0.4 0.1 2.5 2.2 0.1 8.1 0.4 0.0 0.0 8.4 0.1 0.5 5.6 0.0 8.1 0.0 3.8 0.7 0.3 3.3 2.8 0.3 4.3 0.4 0.0 0.0 10.6 0.2 0.8 5.3 0.0 11.2 0.0 8.4 0.6 0.2 2.9 2.5 0.2 3.8 0.4 9.3 0.2 0.7 4.6 9.8 7.4 0.0 0.0 0.0 0.0 0.0 Prp3) 0.0 0.0 0.6 0.6 0.0 0.0 0.6 0.0 2.8 0.0 0.0 0.6 0.0 0.6 0.0 0.0 4.6 0.6 0.0 0.0 Sil 0.0 0.0 1.3 0.0 0.0 0.0 0.0 0.6 0.0 0.0 0.0 0.0 Nod 0.0 0.0 0.0 1.1 0.0 0.0 1.1 0.6 0.0 0.0 0.0 0.6 0.0 te, 0.0 0.0 1.2 0.0 0.0 0.0 2.3 0.6 0.0 2.3 0.0 4.1 0.0 0.0 0.5 0.0 0.5 0.0 0.0 2.5 0.2 0.0 0.2 2.4 0.2 0.0 1.3 0.2 1.7 0.0 0.0 0.3 0.0 0.6 0.0 0.0 1.5 0.3 0.0 0.3 2.3 0.3 0.0 0.7 0.3 2.1 0.0 0.0 0.3 0.6 1.5 0.3 0.3 2.3 0.3 0.7 0.3 2.0 1 BULLETIN 361 Table 1.—Continued. Anacar- cf. Ovoidi- Site Cluster Quercus dium Alnus Carya Nyssa Taxodium tes Vitis Rapenea Freshwater Marsh (N = 8) 62-23 5 el 0.6 0.0 0.0 0.0 3.9 9:5 0.0 0.0 64-E7E 5 0.7 0.0 0.0 0.0 0.0 0.0 7.0 0.0 0.0 64-10 5 1.0 0.0 0.0 0.0 0.0 il5) 12.8 0.0 0.0 64-16E 5 0.0 0.6 0.0 0.0 0.0 3.9 8.4 0.0 0.0 64-16ASG 5) 1.4 0.0 0.0 0.5 0.0 0.9 6.0 0.0 0.0 64-16AE 5 0.4 0.0 0.0 0.0 0.0 1.2 1.4 0.0 0.0 SLTR-O1 5 0.0 0.0 0.0 0.0 0.0 P)s8) 9.6 0.0 0.0 SLTR-02 5) 0.5 0.5 0.0 0.0 0.0 1.8 8.3 0.0 0.0 Avg. 0.6 0.2 0.0 0.1 0.0 1.9 7.9 0.0 0.0 Stdev 0.5 0.3 0.0 0.2 0.0 1.4 3.3 0.0 0.0 cI 0.4 0.2 0.1 1.0 2.3 Headwater Marsh (N = 5) 64-33 6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 SR-25 6 0.0 0.0 0.0 0.0 0.0 0.5 0.8 0.0 0.0 SR-26 6 0.0 0.0 0.0 0.0 0.0 DD, 0.0 0.4 0.0 SR-28 6 0.0 0.0 0.0 0.0 0.0 ile7/ 0.0 0.0 0.0 SR-29 6 0.3 0.0 0.0 0.0 0.0 0.0 0.3 0.0 0.0 Avg. 0.1 0.0 0.0 0.0 0.0 0.9 0.2 0.1 0.0 Stdev 0.1 0.0 0.0 0.0 0.0 1.0 0.3 0.2 0.0 cI 0.1 0.9 0.3 0.2 Headwater Marsh (N = 10) 62-24 7 1.0 0.0 0.0 0.0 0.0 0.7 De, 0.0 0.0 SR-17 q/ 0.0 0.0 0.0 0.0 0.0 4.6 0.0 0.6 0.0 SR-18 iT, 0.0 0.0 0.0 0.0 0.0 2.9 0.0 0.0 0.0 SR-19 7 13) 1.5 0.0 0.0 0.0 2.4 0.5 0.0 0.0 SR-20 7 2.0 0.7 0.0 0.0 0.0 47 0.0 0.0 0.0 SR-21 W 0.0 ey 0.0 0.0 0.0 1.6 0.6 0.0 0.0 SR-22 vii ED 0.0 0.0 0.0 0.0 2) 1.1 0.0 0.6 SR-23 7 1.0 0.0 0.0 0.0 0.5 1.1 0.5 0.5 0.0 SR-24 7 0.9 0.0 0.0 0.0 0.0 1.4 1.4 0.5 0.0 SR-30 7 1.2 0.0 0.0 0.0 0.6 2.4 0.0 0.0 0.6 Avg 0.9 0.4 0.0 0.0 0.1 2.4 0.7 0.2 0.1 Stdev 0.7 0.7 0.0 0.0 0.2 1.4 0.9 0.3 0.3 cI 0.4 0.4 0.1 0.8 0.5 0.2 0.2 Brackish Marsh (N = 9) 62-25 8 0.6 0.0 0.6 0.0 0.0 61 0.0 0.6 0.6 62-30 8 1.9 0.0 0.6 0.0 0.0 8.3 0.6 0.6 0.6 64-18 8 Del 0.0 0.0 0.0 0.0 3}37/ 0.5 0.0 0.0 64-22 8 5 0.0 0.0 0.0 0.0 2.8 4.5 0.0 0.0 HR-O1 8 Net 0.9 0.0 0.0 0.0 4.3 0.0 0.0 0.0 HR-02 8 0.6 0.0 0.0 0.0 0.0 1.9 0.0 0.6 0.0 JR-O1 8 0.0 0.4 0.0 0.0 0.0 0.0 0.0 8.5 0.0 TB-O1 8 ED 0.0 0.0 0.0 0.0 el 0.0 0.0 0.0 TB-02 8 3.0 0.0 0.0 0.0 0.0 2.4 1.2 0.0 0.0 Avg. 1.3 0.1 0.1 0.0 0.0 2.8 0.8 1.1 0.1 Stdev 1.0 0.3 0.3 0.0 0.0 2.4 1.5 2.8 0.3 CI 0.6 0.2 0.2 1.6 1.0 1.8 0.2 Brackish Marsh (N = 5) 62-26 9 1.3 0.0 0.0 0.0 0.0 32.1 1.9 0.0 0.0 62-33b 9 0.9 0.0 0.0 0.0 0.0 2.8 0.0 2.8 0.0 62-35 9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.6 0.0 64-09H 9 0.6 0.0 0.6 0.0 0.0 6.9 0.6 0.0 0.0 64-14 9 0.6 0.6 0.0 0.0 0.0 1.2 1.8 is? 0.0 Avg. 0.7 0.1 0.1 0.0 0.0 8.6 0.9 1.1 0.0 Stdev 0.5 0.3 0.3 0.0 0.0 13.4 0.9 1.2 0.0 CI 0.4 0.2 0.2 11.7 0.8 1.0 Upland (N = 4) 62-27 10 el 0.0 0.0 0.0 0.6 72.5 0.0 D3, 0.0 62-28 10 0.6 0.0 0.6 0.6 0.0 55.4 i133} 0.0 0.0 62-29 10 ile 7/ 0.0 0.0 0.0 0.0 87.4 0.6 0.0 0.0 EE-11 10 0.0 0.0 0.6 0.0 0.0 73.4 0.0 0.6 0.0 Avg. 0.9 0.0 0.3 0.2 0.2 1p 0.5 0.7 0.0 Stdev. 0.7 0.0 0.3 0.3 0.3 13.1 0.6 1.1 0.0 POLLEN ZONATION: O’ NEAL ET AL. 113 Table 1.—Continued Extended. ch Grains Thom- Rhab- Grains used Hame- Myrt- Poly- Eric- Sphag- sono- daden- Liquid- count- for lia Rhus aceae Osmunda podium — aceae num Ulmus pollis Nuphar ia Pteris amber Pinus Other ed Stats 0.0 0.0 0.0 23 0.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 20.2 Pailes) 178 13 0.0 0.0 0.0 0.3 3.3 _ 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 31.6 30.1 301 195 0.0 0.0 0.0 0.5 4.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 24.6 24.4 195 138 0.0 0.0 0.0 2.6 1.9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 16.8 18.7 155 118 0.0 0.0 0.0 1.8 1.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 TL) 21.0 218 161 0.0 0.0 0.0 0.0 2.9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 28.2 32.2 241 151 0.0 0.0 0.0 0.0 0.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 23.0 21.8 261 191 0.0 0.0 0.0 0.5 0.9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 21.6 20.4 218 163 0.0 0.0 0.0 1.0 2.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 23.7 0.0 0.0 0.0 1.1 1.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 4.6 0.7 0.9 3:2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 8.2 12S) 179 157 0.0 0.0 0.0 0.8 0.0 0.0 0.0 0.0 0.0 0.3 0.0 0.0 0.0 1 3h] 375 361 0.0 0.0 0.0 0.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 3.9 6.7 231 216 0.0 0.0 0.0 11.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 ALS) 8.4 242 222 0.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.6 Ds) 307 299) 0.1 0.0 0.0 2.5 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 3.7 0.1 0.0 0.0 4.8 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 2.7 0.1 4.2 0.1 2.3 0.0 0.0 0.0 2.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 93 le7/ 300-244 0.0 0.0 0.0 1.8 0.0 0.0 0.0 0.6 0.0 0.0 0.0 0.0 0.0 10.2 10.9 176 144 0.0 0.0 0.0 6.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 9.5 tT) 168 143 0.0 ile) 0.0 6.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 6.0 13.3 200 159 0.0 0.0 0.0 10.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 7.4 9.6 149 124 0.0 1.1 0.6 7.0 0.6 0.0 0.6 0.0 0.0 0.0 0.0 0.0 0.0 7.0 3.9 185 165 0.0 0.0 0.6 2.9 0.0 0.0 0.0 0.0 0.0 0.6 0.0 iI 0.0 4.5 2.1 178 162 0.0 0.0 0.5 4.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 4.4 3.5} 182 160 0.0 0.0 0.0 6.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 4.6 3.5 220 197 0.0 0.0 0.6 4.8 0.0 0.0 0.0 0.0 0.0 1.2 0.0 0.0 0.0 3.6 Tel 168 144 0.0 0.3 0.2 5.2 0.1 0.0 0.1 0.0 0.1 0.2 0.0 0.1 0.0 6.7 0.0 0.6 0.3 2.6 0.2 0.0 0.2 0.0 0.2 0.4 0.0 0.3 0.0 2.4 0.3 0.2 1.6 0.1 0.1 0.1 0.3 0.2 1.5 0.0 0.6 0.0 1e, 19.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 9.0 13.2 n/a n/a 0.0 0.0 0.0 13 7.6 0.0 0.0 0.0 0.0 0.0 0.6 0.0 0.0 7.6 6.3 n/a n/a 0.0 0.0 0.0 10.1 6.4 0.0 0.0 0.0 0.5 0.0 0.0 0.0 0.0 IE 8.0 n/a n/a 0.0 0.0 0.0 2.3 6.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 IG)? 18.6 n/a n/a 0.0 0.0 0.0 4.4 7.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 6.1 4.3 n/a n/a 0.0 0.0 0.0 3.8 82, 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 5.8 7.2 n/a n/a 0.0 0.0 0.0 8.2 19.2 0.0 0.0 0.0 0.4 0.0 0.0 0.0 0.0 4.1 351 271 241 0.0 0.0 0.0 1.2 il 72 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 6.7 5.0 n/a n/a 0.0 0.6 0.0 0.6 4.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 11.5 4.9 n/a n/a 0.0 0.1 0.0 Abi 8.3 0.0 0.0 0.0 0.1 0.0 0.1 0.0 0.0 9.0 0.0 0.3 0.0 3.3 6.5 0.0 0.0 0.0 0.2 0.0 0.2 0.0 0.0 4.5 0.2 2.2 4.3 0.1 0.1 3.0 0.0 0.0 0.0 0.0 0.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 8.2 10.9 n/a n/a 0.0 0.0 0.0 2.8 6.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 7.6 34.2 n/a n/a 0.0 0.0 0.0 0.0 54.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.5 38) n/a n/a 0.0 0.0 0.0 0.6 6.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 LES) 2.6 n/a n/a 0.0 0.0 0.0 0.6 6.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Tell 11.7 168 133 0.0 0.0 0.0 0.8 14.9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 5.2 0.0 0.0 0.0 1.2 22.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 3.7 1.0 19.5 ah 0.0 0.0 0.0 0.0 ite 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2.8 27 n/a n/a 0.0 0.0 0.0 0.6 il.) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 7.0 15.6 n/a n/a 0.0 0.0 0.0 0.0 0.6 0.0 0.0 0.0 0.0 0.0 0.0 0.6 0.0 0.6 Dal n/a n/a 0.0 0.0 0.0 0.0 0.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2.3 ee. n/a n/a 0.0 0.0 0.0 0.2 1.1 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.0 3.2 0.0 0.0 0.0 0.3 0.6 0.0 0.0 0.0 0.0 0.0 0.0 0.3 0.0 2.7 114 BULLETIN 361 Nuphar Ficus Polygona Morus Alnus Sapotaceae Vitis Ilex Anacardium Osmunda Composits Quercus Typha 3 Gramineae Salix Cephalanthus Polypodium Taxodium Chenopods Triporates Cyperaceae Sagittaria Utricularia E Umbelliferae cf. Ovoidites Nymphaea Pinus (a Rhizophora Conocarpus D Laguncularia Avicennia Batis Rhus Sphagnum Carophyllaceae Fraxinus Eugenia Carya Rhabdadenia Ericaceae it Hamelia Ulmus Pteris A Rapenea cf. Thomsonopollis Nyssa Myrtaceae tO : Distance Text-figure 3.—Dendrogram illustrating associations of surface pollen and spore categories. Four cluster groupings are based on a Chi-squared distance of ~2.8. nus. Cluster D contains Rhizophora, Conocarpus, La- guncularia, Avicennia, and Batis (Text-fig. 3). Cluster A contains taxa that are generally found in lower frequencies than those of other clusters (Table 1). Sub-cluster Al includes taxa that have very low pollen frequencies and commonly appear in <2% of the sample sites. In addition, there are no clear patterns of spatial distribution for these taxa. The taxa in sub- cluster A2 appear in slightly higher frequencies than those of sub-cluster Al, but are still generally rare with no clear spatial distribution. The taxa in sub-cluster A3 are more common than the taxa in the other two sub- clusters, appearing in 30—50% of the sites. In addition, these taxa tend to occur in the freshwater marsh (slough), freshwater marsh with hammocks, and brack- ish marsh vegetation communities (Text-fig. 2). Clus- ter B is comprised of only chenopods. Chenopods are correlated most strongly with sites in the freshwater marsh—slough vegetation community (Text-fig. 2). However, they occur at all sites and tend to have an inverse relationship with abundances of Rhizophora. Riegel (1965) also noted this relationship. Cluster C consists of taxa that are generally more abundant than those of cluster A and are consistently found at ap- proximately 50% of the sample sites. In addition, taxa from cluster C show a strong spatial correlation with the freshwater marsh—slough and freshwater marsh with hammocks vegetation communities (Text-fig. 2). Finally, cluster D is comprised of taxa that are domi- nant in mangrove swamp and brackish marsh vegeta- tion communities (Text-fig. 2). Cluster Analysis of Sample Sites The dendrogram from cluster analysis of the 86 sur- face samples can be divided into ten distinct cluster groups (Text-fig. 4). Samples in clusters 1, 2 and 3 are from locations in the mangrove swamp vegetation community and the margin of the brackish marsh veg- etation community near the mangrove swamp. Cluster | is comprised of samples 62—01, 62—06, 62—08, 62 1 62-12. 62-15; 62-175 62-20562—21FvandsG2—22" These samples are from locations that are | to 2 ki- lometers from the coast (Text-fig. 2). Cluster 2 is com- prised of samples 62—2, 62-3, 62—5, 62—7, 62-9, 62 10, 62-13, 62-14, 62-18, 62-19, 64-11, 64-21, SR- Ol, SR-02, and 59-T1. These samples are generally from sites along the coastal margin of the mangrove swamp (Text-fig. 2). Samples in cluster 2 have 35 taxa present, the widest variety of any cluster. Cluster 3 is comprised of samples SR-03 to SR-07, SR-09, SR-10, and SR-13 to SR-16. These samples are from sites along the mouth of the Shark River where there is a strong marine influence. The three clusters are domi- nated by mangroves (Rhizophora, Avicennia, and La- guncularia), Batis, chenopods (pigweed family), Con- ocarpus, and Compositae (aster family) pollen types. The frequency of Rhizophora in cluster | is 20% high- er on average than in clusters 2 and 3. Cluster 2 sam- ples differ primarily from cluster | by having higher frequencies of Avicennia and chenopods. Cluster 3 dif- fers from clusters | and 2 by possessing more tripor- ates, chenopods, and Conocarpus (Table 1). Clusters 4 and 5 contain samples distributed throughout the freshwater marsh-slough, freshwater marsh with hardwood hammocks, and freshwater marsh with cypress hammocks vegetation communi- ties (Text-fig. 2). Cluster 4 is comprised of samples 62-34, 64-04, 64-07, 64-09, 64-E7SG, 64-15, 64— 16-SG, SLTR-03, and SLTR-04. Cluster 5 is com- prised of samples 62—23, 64-E7E, 64—10, 64—16AE, 64—-16ASG, 64—16E, SLTR-01, and SLTR-02. AI- though neither cluster occurs exclusively in a single vegetation community, samples in cluster 4 are pri- marily from the freshwater marsh with hardwood ham- POLLEN ZONATION: O’ NEAL ET AL. 115 Environment Cluster l Mangrove 2 Swamp 3 4 Freshwater Marsh 5 | See 6 SR2¢ Headwater SR-22 — Marsh sR23 J 7 SRS j 8 1Bai Brackish e423 Marsh + 9 414 Sli H 62. =] Upland 10 ; [ T T =a 1 0 5 10 15 20 Distance Text-figure 4.—Dendrogram illustrating association of surface sample cluster groups to environments. Ten clusters are designated based on a Chi-squared distance of ~2 (dashed line). mocks and freshwater marsh with cypress hammocks vegetation communities, while those in cluster 5 are mainly from the freshwater marsh slough vegetation community. The dominant pollen types associated with freshwater marshes are chenopods, triporates, Nym- phaea, Sagittaria, cf. Ovoidites, Compositae, and Cy- peraceae (sedge family). Both of these clusters contain a wide variety of freshwater-dependent species, but chenopod abundances are approximately 33% higher in cluster 5 (Table 1). Samples from clusters 6 and 7 are from sites located near the transition between the Everglades Depression and the mangrove swamp (Text-fig. 1). Although this area is designated as part of the brackish marsh veg- etation community by Riegel (1965) (Text-fig. 2), Rie- gel (1965) also describes this area as a unique zone called the headwater marsh. The assignment of head- water marsh will be used to designate this area in this study as well. Cluster 6 is comprised of samples 64— 33, SR-25, SR-26, SR-28, and SR-29, whereas cluster 7 is comprised of samples 62—24, SR-17 to SR-24, and SR-30. Samples in cluster 6 were obtained from lo- cations along the margin between the freshwater marshes and brackish marsh, while samples in cluster 7 were selected from a more seaward position within the brackish marsh vegetation community (Text-fig. 2). The dominant pollen types associated with the head- water marsh are Rhizophora, chenopods, triporates, Conocarpus, and Osmunda (ferns). Cluster 6 samples have more than twice the average frequency of che- nopods of cluster 7, whereas cluster 7 samples display a marked increase in Rhizophora and triporates (Table i): Cluster 8 groups samples from within the brackish marsh vegetation communities. This cluster includes samples HR-O1 and HR-02, TB-01 and TB-02, JR-O1, 62-25, 62—30, 64—18, and 64—22. Taxa common to the brackish marsh (1.e., Rhizophora, triporates, cheno- pods, Polypodium (ferns), Conocarpus, and Cypera- ceae) dominate these samples. However, there is a wide diversity of taxa present in this cluster (Table 1). Cluster 9 contains samples that are from the fresh- water marsh with hardwood hammocks and freshwater marsh with cypress hammocks vegetation communi- ties, but are grouped with the brackish marsh cluster. This cluster contains samples 62—26, 62—33b, 62-35, 64—09H, and 64—14. These samples include a variety of common freshwater species such as Sagittaria, Um- belliferae, and Salix (willow family), but they have more Compositae and less Pinus pollen than is found in the freshwater marshes. Although these samples contain a variety of taxa, each has an individual taxon that comprises at least 25% or more of the sample and does not conform to any common dominant species distribution found in other cluster groups (Table 1). For example, 27.4% of sample 64—14 is Cephalanthus (Buttonbush) and 26.4% of sample 64—09H is Salix. Cluster 10 contains samples from sites along the At- lantic Coastal Ridge within the freshwater marsh with cypress hammocks vegetation community. This cluster contains samples 62-27 to 62—29, and EE-11. The dominant taxon associated with these sites is Taxo- dium, although there are also a variety of freshwater components present in these samples (i.e., Gramineae, Cyperaceae, and Compositae) (Table 1). Discriminant Analysis Discriminant analysis correctly assigned all 86 sam- ples to the environmental groups delineated by cluster 116 BULLETIN 361 Table 2.—Pooled within-groups correlations (loadings) between taxa and discriminant functions. The 18 key contributing taxa are highlighted. Taxa Function | Function 2 Function 3 Function 4 cf. Ovoidites —0.05813 0.22115* —0.21270 —0.06030 Triporates —0.00777 0.21434* 0.21033 0.04846 Tlex 0.00486 0.07691 0.15489* —0.01152 Utricularia —0.02764 0.09736 —0.10737* —0.00624 Rhabdadenia 0.00280 0.02188 0.05313* —0.01507 Chenopods —0.08009 —0.01600 —0.11739 0.46002* Taxodium 0.21718 0.02709 —0.22441 —0.24851 Umbelliferae 0.03061 0.03766 —0.03234 0.5863 Pinus —0.06834 0.12545 —0.13453 —0.12608 Salix 0.06142 0.01412 —0.00748 0.06407 Cephalanthus 0.04336 0.01126 —0.00109 0.08223 Composits 0.05375 0.01563 0.07966 0.06185 Sapotaceae 0.02655 0.00773 —0.00527 0.04206 Rhizophora —0.05571 — 0.30883 0.14459 —0.24059 Ficus 0.02610 0.03491 0.06934 0.02143 Sphagnum —0.00375 —0.02183 0.00589 0.00232 Quercus —0.00703 —0.00955 0.02081 —0.09885 Myrta —0.00405 —0.00153 0.02151 0.10310 Osmunda —0.00653 0.02657 0.05460 0.07390 Fraxinus —0.00419 0.01061 0.04842 0.01722 Nuphar —0.00428 —0.00930 0.00679 0.05765 Nyssa 0.02168 0.00030 —0.01830 0.01646 Caryophyllaceae —0.00337 —0.01131 0.02565 —0.00836 Laguncularia —0.01176 —0.05997 0.01209 —0.06271 Carya 0.00979 —0.01318 —0.02525 —0.03736 Rhus —0.00284 —0.00467 0.03766 0.02378 Pteris 0.01606 0.00022 —0.01355 0.01219 Rapenea —0.00428 0.03605 0.02974 0.00614 Ericaceae —0.00287 —0.01593 —0.00225 —0.01830 cf. Thomsonopollis —0.00258 0.03484 0.03885 0.00052 Conocarpus —0.01460 —0.04109 0.14725 — 0.09632 Avicennia —0.02068 —0.11662 0.00641 — 0.08752 Anacardium —0.01116 —0.04637 0.00337 —0.04570 Batis —0.00755 —0.04279 0.00075 —0.01688 Polypodium 0.04074 0.04546 0.05585 0.02431 Cyperaceae 0.00343 0.14085 0.09104 —0.04395 Typha 0.00558 0.05675 0.07508 —0.01937 Gramineae 0.00381 0.04199 0.03805 —0.03976 Vitis 0.02567 0.03047 0.04343 —0.00396 Nymphaea —0.03497 0.08198 —0.12149 0.01812 Sagittaria —0.01212 0.08797 — 0.08782 0.07566 Hamelia —0.00513 —0.00912 —0.01654 0.06530 Ulmus —0.00701 0.02828 —0.02115 —0.01904 Alnus 0.00442 0.02143 —0.00730 —0.05957 Eugenia 0.00908 0.03237 0.03283 —0.01658 Polygona 0.04516 0.01269 —0.03082 0.06516 Morus —0.00386 0.03707 —0.00408 —0.00298 analysis. The first four discriminant functions account for 92.5% of the variance in the data set and display high canonical correlations of 0.996, 0.989, 0.981, and 0.971 respectively, underscoring the effectiveness of the functions in discriminating between cluster group- ings. The function loadings from the first four func- tions indicate that the surface cluster groupings are strongly influenced by 18 key taxa (Table 2). Taxo- dium, the dominant genus of the freshwater marsh with cypress hammocks physiographic zone, and chenopods are the statistically significant taxa on function 1. Sig- nificant taxa on function 2 include cf. Ovoidites, tri- porates, Ilex, Utricularia, Pinus, Rhizophora, Avicen- nia, Cyperaceae, Nymphaea, and Sagittaria. Important taxa on function 3 are cf. Ovoidites, triporates, Ilex, Utricularia, chenopods, Taxodium, Pinus, Composi- tae, Rhizophora, Conocarpus, Cyperaceae, Typha, Nymphaea, and Sagittaria. On function 4, chenopods, Taxodium, Pinus, Cephalanthus, Rhizophora, Quer- cus, Osmunda, Conocarpus, Avicennia, and Sagittaria POLLEN ZONATION: O’ NEAL ET AL. WaL7/ Function 2 \o te 0 10 Function 1 71K 9 Function 3 rl tb Function 2 Text-figure 5.—(A) Plot of means and 95% confidence intervals for environmental cluster groups on discriminant functions one and two. (B) Plot of means and 95% confidence intervals for environ- mental cluster groups on discriminant functions two and three. Num- bers refer to cluster groups in Text-figure 4. The symbol used to identify cluster group 7 (Figure A) encompasses the 95% confidence interval bars for that group. contribute most to group separation. Means and 95% confidence intervals for each group are plotted in Text- figure 5. A plot of discriminant score group means in three-dimensional discriminant function space displays broad spatial separations that underscore the statistical distinctiveness of the environmental groupings ob- tained from cluster analysis (Text-fig. 6). DISCUSSION OF SURFACE POLLEN ZONATION Visual inspection of the pollen data matrix sorted by site and taxonomic/morphologic groupings derived from cluster analysis (Table 1) indicates that there is a large amount of overlap in the species composition of the environmental cluster groups. Individual pollen and spore taxa typically are not environmentally re- stricted so that no single pollen or spore type can be used to characterize a particular environment. Rhizo- phora pollen, for instance, is most abundant in man- grove swamp clusters where it comprises from 16 to 66% of samples. However, it contributes as much as 17% to samples from brackish marsh cluster 8 and as much as 29% to samples from the headwater marsh cluster 7. Chenopods are most common in samples from the headwater marsh clusters with abundances ranging between 15 and 90%. However, they also comprise 7 to 47% of samples from the freshwater marsh clusters. Similarly, triporates are most abundant in samples from the brackish marsh clusters, where they comprise 11 to 23% of the samples, but they com- prise as much as 21% of samples from freshwater marsh cluster 4. Because of these occurrence patterns, visually determined associations of taxa may not be reliable indicators of environments. Riegel (1965) and Kuehn (1980) both relied on the appearance of Typha (cattail) and Conocarpus in vertical sequences to in- dicate an environmental shift to a brackish marsh. Dis- criminant analysis indicates that Conocarpus is an im- portant component of the brackish marsh. However, our results do not indicate that the abundances of these species co-vary and suggest that the mere presence of these species is not a reliable environmental indicator. In contrast, Rich et al. (1982) interpret cf. Ovoidites to be an indicator of freshwater environments. Statis- tical analysis confirms that cf. Ovoidites is an impor- tant species of the freshwater marsh, but this interpre- tation is strengthened by the co-occurrence of cf. Ovo- idites with Sagittaria, Nymphaea, Utricularia and Um- belliferae (hornwort), all of which are aquatic species (Text-fig. 3; Table 1). Pollen from the genus Pinus has a ubiquitous distribution because it is transported read- ily throughout the system by both wind and water (Ha- bib et al, 1994). Although it is generally most abun- dant near its origin in the Pine-Upland vegetation com- munity, the presence of Pinus in all other vegetation communities, and its tendency to concentrate along the coast because of fluvial and marine transport, limits its usefulness. However, a study in Taylor Slough (which drains a small portion of the southern Everglades into Florida Bay) indicates that Pinus pollen comprises a significant proportion of samples and may be a useful taxon for paleoenvironmental interpretation there (Wil- lard and Holmes, 1997). Similarly, trees of the genus Quercus are physically restricted to freshwater up- lands. However, Quercus pollen tends to be wide- spread and present in low abundances, which may also limit its use for environmental interpretation. As discussed above, numerically dominant pollen 118 Cluster Group Membership e Cluster 1 cheno 1) Cluster 2 Mangrove Swamp Cephalanthus Sagittaria, \qQ Cluster 3 Osmunda e Cluster 4 8 Freshwater Marsh © Cluster 5 6 a Cluster 6 les} 1 Headwater Marsh | 4 o Cluster 7 Qo 4\n Aa Cluster 8 Brackish and O° & Aa Cluster 9 Transitional Marsh = iS g U Cluster 10 | Upland S Taxodium S pet Rhizophora 4 > e cf, Ovoidites Pinus, Quercus, S, Conocarpus, 15 triporates, z Aiea s6 3 erneracesey eins Percent of Variance Utricularia i wa 5 Sagittaria, Function | = 56.76 triporates, //ex Conocarpus 5 Rhizophora. On Cyperaceae, S} -10 -10 composits, aw Taxodium, . cf Ovoidites, Pinus Nymphaea, chenopods, Utricularia, Sagittaria BULLETIN 361 vl Nymphaea, Ilex Function 2 = 18.59 oe Function 3 = 10.39 as Function 4 = 6.82 Rhizophora Avicennia Text-figure 6.—Three-dimensional plot of environmental cluster-group discriminant-score means with salinity regimes and key taxa displayed on each axis. Key taxa were identified by running stepwise iterations of discriminant analyses to identify the threshold where 100% discri- minantion was no longer achieved. taxa are not restricted to a given cluster. Of note is also the fact that several species are not present in certain environments (Table 1). For example, Avicen- nia never occurs in the freshwater marshes. Lagun- cularia and Vitis (wild grape) pollen are extremely rare in the freshwater marshes, appearing in low numbers in only one sample. Cephalanthus and Salix are not present in the mangrove swamp or headwater marsh. However, other pollen and spore types that are restrict- ed to one, or even two cluster groups, for example Ericaceae, are uncommon and comprise less than 1% of any given sample. Thus, their presence appears to be very sensitive to sampling and preparation proce- dures and very large sample volumes and counts would be required to be certain that their absence re- flects environmental or depositional conditions. Addi- tional problems may occur in that many rare pollen types generally comprise less than 2% of a sample and may not be present in statistically significant numbers in small samples. In most cases, the identification of a given environment cannot be based on the presence or absence of any single taxon and multivariate statistical analysis of pollen assemblages is necessary. The surface sample groupings obtained from cluster analysis do, however, display a spatial distribution that is strongly correlated with the physiographic provinces of the study area (Text-fig. 7). This is evident when the sample sites (from Text-fig. 2) are categorized by clusters (from Text-fig. 4) and overlaid on the phys- iographic map of the study area (Text-fig. 1). In samples from the Mangrove Swamp _ physio- graphic province, there is a strong correlation between the frequency of Rhizophora, Avicennia, chenopods, triporates and Conocarpus in a given sample and the elevation, salinity, and proximity to major rivers from which samples were taken. Cluster | contains samples that are located approximately 1 km from the current shoreline along tidal channel margins where Rhizo- phora is dominant. These samples contain an average of 20% more Rhizophora than samples in the other mangrove swamp clusters. Cluster 2 samples are from areas along the coastal margin where there is more variability in substrate type, tidal influence, and ele- vation than is seen in cluster | areas. This variability is reflected in the increased frequency of mangrove forest taxa (Avicennia, Laguncularia, and Conocar- pus) in cluster 2 samples. Cluster 3 contains samples with more triporate and Conocarpus pollen than sam- ples in cluster 1 and 2. The samples in cluster 3 are from locations along the mouth of the Shark River, a primary route of freshwater delivery to the Gulf of Mexico. Therefore, it is reasonable to expect taxa com- mon in brackish and freshwater marsh communities upstream to be present in cluster 3 samples. Differences between clusters 4 and 5, from the freshwater marshes, are less evident than for other POLLEN ZONATION: O’NEAL ET AL. 119 GULF OF MEXICO Cluster Group Membership Physiographic Provinces © Cluster 1 © Cluster 2 Mangrove Swamp ba) Mangrove Swamp © Cluster 3 @ Cluster 4 ; as) Brackish & Transitional Marsh E Freshwater Marsh © Cluster 5 - mw Cluster 6 y Freshwater Marsh (Slough) Headwater Marsh O Cluster 7 (Ezal A Cluster 8 Bracken and Freshwater Marsh with Hammocks 4 Cluster 9 Transitional Marsh UT Cluster 10 Upland Ba Limestone Upland Complex Text-figure 7—Overlay of sample site cluster groupings on phys- iographic map of southwest Florida showing strong correlation be- tween environmental pollen clusters and physiographic provinces. Clusters 1, 2, and 3 are the mangrove swamp; clusters 4 and 5 are the freshwater marsh; clusters 6 and 7 are the headwater marsh; clusters 8 and 9 are the brackish marsh; and cluster 10 is the upland complex. clusters. The abundance of a variety of freshwater-de- pendent taxa such as Nymphaea, cf. Ovoidites, and Utricularia assist in delineating this pollen zone, but compositional differences between the slough and ad- jacent marshes with hammocks result primarily from a large increase in the frequency of chenopods in the slough. Riegel (1965) attributed the dominance of che- nopods and Nymphaea in the slough to their need for a higher water table in this low-lying area. Differences in the headwater marsh clusters are based on changes in the frequency of Rhizophora and chenopods. Chenopods comprise more than 60% of samples from the headwater marsh (cluster 6) and are less dominant in cluster 7. Rhizophora, which com- prises less than 2% of any of the samples in cluster 6, increases to an average of 16% in cluster 7. The in- crease in Rhizophora occurs in samples nearer to shore where the slough shifts to channels and Rhizophora is localized along the margins. Samples from the brackish marsh, cluster 8, contain a wide variety of taxa. Tidal variability as well as fluc- tuations in freshwater and marine input strongly influ- ence the taxa that can survive in the brackish marsh zone. The pollen spectrum resembles the mixture of taxa that result from in situ deposition in the brackish marsh (i.e. triporates, Conocarpus, Cyperaceae, Os- munda, and Polypodium) plus components from the adjacent mangrove swamp and freshwater marsh en- vironments. Many samples are dominated by individ- ual taxa that do not occur in high frequencies else- where. These samples are grouped primarily in cluster 9 where individual taxa comprise 25% or more of the pollen totals. Each of these species is associated with the hardwood hammocks of the freshwater marsh (i.e. Cephalanthus, Taxodium, and Salix). It is likely that the broad distribution of taxa in conjunction with the low frequency of mangrove swamp taxa, resulted in the strong association of these samples with the brack- ish marsh rather than with freshwater marshes. The samples in cluster 10 are from the freshwater marsh with cypress hammocks vegetation community. Each sample contains at least 50% Taxodium pollen, confirming Riegel’s (1965) conclusion that an abun- dance of this species is indicative of the parent vege- tation and the environment in which it occurs. The loadings from the first four discriminant func- tions indicate that the surface pollen cluster groupings, or zones, are strongly influenced by 18 key taxa (Table 2). When the taxa are plotted along the functions (Text-fig. 6) it is evident that they are organized by salinity regimes. Although, hydroperiod, elevation, and salinity control the distribution of taxa and limit the pollen spectra of a sample, the functions only clearly display the salinity regimes when groups of taxa are arrayed on each axis towards the regime where they provide their strongest contribution. Text- figure 6 displays functions 2, 3, and 4 with the key taxa that drive each function towards the different re- gimes. Function 1, which is driven by Taxodium and, to a lesser degree by chenopods, was not plotted in the figure because it only excludes cluster 10 from the other groups (i.e., it serves to separate the Taxodium dominated hammocks of the freshwater marsh from other environments). Function 2 is driven by a suite of taxa from freshwater regimes at one end and dom- inant marine taxa on the other. Function 3 represents fresh to brackish regimes and helps separate the fresh- water clusters from the others. Function 4 separates clusters located in and near the brackish areas from those with more freshwater and marine influences. The taxa that are listed at the end of each axis represent the key taxa for each regime that drive a cluster in either direction. Thus, a cluster’s position on each axis is related directly to the key taxa that are present for each function. When the clusters are viewed on all three functions, domains representing different salinity 120 BULLETIN 361 Table 3.—Range and average frequency of the 18 key taxa derived from discriminant analysis of the 86 surface sample sites. Cluster Rhizophora Avicennia Conocarpus | Chenopod Cyperaceae Nymphaea Utricularia 1 Mangrove Swamp Range 43.7-66.1 0-7.6 0-7.3 2.8—11.8 O-1.7 0-0.6 0-0 Average 57.4 3 3 6.7 0.8 0.1 10) Std. Dev cs) 2.9 2.5 Poe) 0.5 0.3 (0) 2 Mangrove Swamp Range 11.7-49 0.6-9.6 1.7-11.8 5.9-28.4 0-4.3 0-1.3 0-0 Average BirS 4.3 4.1 14 0.7 0.3 0 Std. Dev 10.2 29) 2.6 6.7 Hil 0.5 0) 3 Mangrove Swamp Range 13.5-52.4 0-3.2 2.5—14.2 6.5—35.3 0-2.4 O-1.1 0-0.5 Average 33.3 12 8.4 16.1 0.9 0.4 0.1 Std. Dev Wile 13) 3.6 8.8 0.8 0.4 0.2 4 Freshwater Marsh Range O-1.2 0-0 O-1.2 2.8-17.3 2.8-12.3 0-8.9 0-1.8 Average 0.3 0 0.5 9.7 6 BoD, 0.7 Std. Dev 0.5 0 0.4 5.8 2.8 SY 0.6 5 Freshwater Marsh Range O-1.2 0-0 0-0.6 22.9—47.2 1.2-5.6 1.7-25.3 0-1.9 Average 0.3 0) 0.1 B27 Qui 9.6 0.7 Std. Dev 0.4 (0) 0.2 tS 1.5 Well 0.6 6 Headwater Marsh Range O-1.3 0-3.4 0-0.6 62.1-89.9 0.3-2.1 0-0.8 0-0 Average 0.6 0.7 0.1 76.3 0.9 0.4 0) Std. Dev 0.5 IES 0.3 10.5 0.8 0.4 (0) 7 Headwater Marsh Range 2.3-28.7 O-1.8 0-4 14.9-47.7 0.7—4.2 0-2.3 0-0.5 Average 16.1 0.7 1.5 32.4 IES) 1 0.18 Std. Dev 8.8 0.6 1.4 11.5 1.1 0.8 0.2 8 Brackish Marsh Range 2.3-16.9 0-0.6 1.1-19.1 4.8-19.1 0.9-17 0-0.6 0.0 Average 10.2 0.1 6.7 9.4 8 0.1 0 Std. Dev V5) 0.2 6.2 4.3 6 0.2 0) 9 Brackish Marsh Range 0-1.3 0-0 O-1.3 0.5—15.1 1.6-3.6 0-0.6 0-0.6 Average 0.5 (0) 0.5 5.3 Del 0.1 0.1 Std. Dev 0.7 0 0.6 6 0.7 0.3 0.3 10 Upland Range 0-0.6 0-0 0-0.6 0.6-17 0-4.1 0-0 0-0 Avg 0.3 (0) 0.2 12 Py.) 0 0 Std. Dev 0.3 0) 0.3 0.5 2 0 10) regimes are apparent (Text-fig. 6). Although hydro- period, salinity and elevation are strongly correlated in the study area, hydroperiod and elevation differences do not appear to be controlling distributions that are identifiable in this form of multivariate statistical anal- ysIs. A discriminant analysis of the surface sample data set based solely on the 18 key taxa produced 98.84% correct discrimination, with only one sample from cluster 2 misclassified as a member of cluster 3. This misclassification is a shift within the mangrove swamp environment and is not a complete reassignment to a different environment. These results indicate that anal- yses like this could potentially be completed using only the 18 key taxa in Table 3, although none of these taxa are restricted to a single cluster. Analysis of all of the taxa in a sample may be required to determine relationships between samples. Text-figure 8 is a gen- eralized schematic of the Everglades physiographic provinces with the key pollen types that help delineate each area. This conceptual diagram can be used to de- termine the distribution and relative importance of the 18 key taxa in the different physiographic zones. A primary reason for this is that a variety of taxa are present in relatively low abundances in some clusters such as the freshwater marsh clusters 4 and 5. This problem reiterates the need for high pollen counts. The suggested minimum count of 150 grains per sample used by Riegel (1965) is still very low. PART B: APPLICATION TO VERTICAL SEDIMENTARY SEQUENCES In order to assess the value of the approach for pa- leoecological interpretations, pollen data were collect- ed for two cores. The first, from the coastal margin of the Harney River (referred to hereafter as 59-T1) was collected by Reigel (1965). The second, core 9411-7, was collected from the Gopher Key region for a sed- imentologic study by Gelsanliter (1996) (Text-fig. 1). Both are long cores, taken to the Pleistocene bedrock surface and potentially contain sediments that record much of the late Holocene depositional history of southwest Florida. Core Descriptions The sedimentological description for core 59-T1 is presented in Riegel (1965). The core is 3.97 m in POLLEN ZONATION: O’ NEAL ET AL. 121 Table 3.—Extended. Cephalan- Ilex Triporates Taxodium Ovoidites Pinus Sagittaria Composits thus Quercus Typha Osmunda 0-0 0-0 0-3.2 0-0 2-20.7 0-0 1.8-6.1 0-0 0-1.9 0-0.6 0-0.6 (0) 0) 1.6 0 8.7 2.9 0) 0.6 0.1 0.1 0 10) 1.1 0 S)si/ il} 0) 0.7 0.3 0.2 0-0.6 0-3.9 0-4.5 0-0.9 5.3-27.4 O0-0.7 0-9.6 0-0.5 0-4.3 O-0.7 O-18.1 0 0.9 NES) 0.1 12.8 0.1 i) 0 2.2 0.2 1.8 0.2 1.3 1.4 0.3 5.6 0.2 2.3 0.1 1.4 0.3 4.6 0-0.7 2.9-13.9 O0-1.3 O-1.7 6.3-17.3 O-1.8 0.6—4.2 0-0 0-3.2 0-0.7 0-0 0.1 Se) 0.7 0.6 10.2 0.5 2.2 0 1.4 0.1 0 0.3 3 0.5 0.6 Bul 0.6 13 0 Vil 0.2 0 0-1.2 6.9-21.2 0.5-5.3 2.9-15.8 13.9—47.8 0.9-11.5 0.5—4 0-1.7 0.5-3.2 0-6.1 0-6.3 0.3 11.7 2.3 10.1 28.3 4.8 2:2, 0.6 1.4 0.9 1.6 0.4 4.8 1.5 4.2 10.1 4.4 ile? 0.6 0.8 2 22 0-0 0.8-13.5 0-3.9 1.4-12.8 16.8-31.6 0.5—5 0-2.7 0-0.5 O-1.4 0-0.8 0-2.6 0 5.5 1.9 VS) 235) DES I 0.1 0.6 0.2 1 10) 4.4 1.4 33 4.6 1.7 1 0.2 0.5 0.3 1.1 0-0 0-3.9 0-2.2 0-0.8 1.6-8.2 0-S.9 0-4 0-0.4 0-0.3 0-0.6 O-11.1 0 2 0.9 0.2 Su 2.9 IES 0.1 0.1 0.3 25) 0 1.4 1 0.3 2.7 2.1 1.7 0.2 0.1 0.3 4.8 O-1.4 5.5—20.4 0.7—4.7 0-2.7 3.6—10.2 0.6-3.6 1-10.3 0-12.5 0-2 0-2.3 1.8-10.1 0.6 10.9 2.4 0.7 6.7 1.6 3.9 1.6 0.9 0.5 5.2 0.5 4.1 1.4 0.9 2.4 0.9 2.8 3.9 0.7 0.7 2.6 0-4.1 11.1-23.3 0-8.3 0-4.5 4.1-19.2 0-0.9 1.8-7.4 O-1.1 0-3 0-7.3 0.6-10.1 1.5 18.6 2.8 0.8 9 0.3 4.4 0.2 3 DED, 3.7 1.3 3.9 2.4 1S 4.5 0.4 2.1 0.4 1 2.8 333 0-0 0.5—14.5 0-32.1 O0-1.9 0.5—-8.2 0-8.3 3.6-12.7 0.5-27.4 O0-1.3 O-1.6 0-2.8 0 5.6 8.6 0.9 5.2 2S) 8.1 8.1 0.7 0.4 0.8 0 2)53) 13.4 0.9 Shi 3.3 4.3 11.2 0.5 0.7 1.2 0-0:6 0.6—2.3 55.4-87.4 O-1.3 0.6-7 O-1.2 1.2-4.6 0-4.1 0-1-7 0-0.6 0-0.6 0.2 1.3 72.2 0.5 3.2 0.5 PES) 1.7 0.9 0.5 0:2 0.3 0.7 1341 0.6 Del] 0.6 Iles) Dal 0.7 0.3 0.3 length (Text-fig. 9). Its base contains a mixed marl and peat (3.97 m to 3.73 m) overlain by a pure peat that grades into a muddy mangrove peat (3.73 m to 0.76 m), and is capped by organic-rich carbonate muds (0.76 m to the surface in 1965). The sedimentological description of core 9411-7 is presented in Gelsanliter (1996). This core is 2.63 m in length (Text-fig. 10). The base of the core (between 2.63 m and 2.10 m) consists of quartz sands overlain by a red mangrove peat (between 2.10 m and 1.74 m). A gray mudstone to wackestone is present between 1.73 m and 1.50 m. Between 1.50 m and 1.37 m is a red mangrove peat overlain by a gray mudstone to wackestone (1.37 m and 0.97 m) that grades into a tan mudstone to wackestone (0.97 and 0.75 m). Capping the sequence, between 75 cm and the depositional sur- face in 1994, is a red mangrove peat. Laboratory Methods for Pollen Analysis of Core Samples Identification of pollen and spore types in the cores followed standard procedures (Moore et al., 1991; Wood et al., 1996). Core sub-samples of a known vol- ume were taken with a 10-cm? syringe, water content was determined, and bulk density calculated for sub- sequent count normalization. Organic content of pre- viously dried sediment was estimated from weight loss on ignition at 450°C for 6 hours (Dean, 1974). Initially, 1 g sub-samples were processed for pollen concentra- tion. However, the large quantity of organic material present in all samples yielded low pollen concentra- tions using standard processing techniques. Using standard methods on larger quantities of material (7.e., >1 g) often resulted in incomplete digestion of organic debris that masked the presence of pollen. Therefore, multiple, smaller sub-samples of approximately 0.2 g to 0.25 g were dried, disaggregated and spiked with a Lycopodium yield tracer tablet to facilitate the calcu- lation of absolute pollen concentrations (Stockmarr, 1971). Lycopodium tablets were dissolved and calcium carbonate was removed from the sample by the addi- tion of 10% HCl. All samples were treated with HF in a hot water bath to remove silica. After neutraliza- tion of the acid, samples were dried and treated in a hot water bath with 5% KOH for 3 minutes. Samples were sieved with a 200 pm screen to remove large 122, BULLETIN 361 Upland Freshwater P Marsh Slough with Hammocks Freshwater Marsh ° Headwater ' Brackish and Marsh Transitional Mangrove Swamp High Tide Marine | Pollen Type Brackish | Ric ophora Avicennia a | Conocarpus Osmunda composits triporates Ilex Cyperaceae Typha Cephalanthus chenopods Sagittaria Nymphaea Utricularia cf. Ovoidites | Taxodium | Pinus | Quercus Text-figure 8.—Conceptual diagram displaying the distribution of the 18 key taxa across the major physiographic zones of the study area. Shading on bars represents relative within-taxa frequency in a given environment (darker = more abundant). organic detritus. After sieving, the samples were ace- tolyzed in a hot water bath for 3 minutes. After neu- tralization, pollen concentrates were dehydrated with alcohol, suspended in silicon oil, stained with safranin and mounted on microscope slides for examination. Sample Counts Pollen identification for core 941 1—7 was completed at Indiana University/Purdue University at Indianapo- lis. Pollen grains were identified under incandescent and fluorescence light microscopy by comparing them to a reference set of tropical pollen consisting of her- barium samples from Everglades National Park, a set of modern pollen taxa provided by D. Kuehn (Western Kentucky University), and a computerized database. Under fluorescence, details of exine microstructure and ornamentation are enhanced thereby facilitating grain identification. Core 59-Tl was processed and counted by Riegel (1965). Riegel (1965) indicates that standard prepara- tion procedures were followed and counting was con- ducted on at least three slides per sample. For each site, Riegel (1965) attempted to count a minimum of 150 grains. Due to the scarcity of grains in some sam- ples, on occasion, counting was stopped after a mini- mum of 100 grains. Riegel (1965) did not use marker grains; thus absolute pollen concentrations are not pre- sented. In total, Riegel counted 28 samples for core 59-T1 (Table 4). For core 9411—7 every attempt was made to count 300 grains for each sample interval. In total seventeen samples from this core were counted (Table 5). For most samples however, the scarcity of pollen necessi- tated lower counts (range 102 to 306). Most palynol- ogists working in South Florida attempt to identify a minimum of 300 grains, although many data sets are characterized by low pollen sums of commonly around 150 grains (Riegel, 1965; Kuehn, 1980; and Willard and Holmes, 1997). Statistical Analysis of the Core Data Discriminant analysis was used to assign core sam- ples to surface pollen zones, identified earlier in this paper, in order to identify environmental changes in the vertical sequences over time. The input data were the frequency counts. The data sets for the cores were reduced to the same 48 taxonomic and morphologic pollen and spore categories presented in the first sec- tion of this study. Discriminant function scores were calculated for each sample by transforming the original set of measurements into a single value on each func- tion. Using these scores, each sample was assigned to the surface cluster group with which it was most sim- POLLEN ZONATION: O’ NEAL ET AL. | i) >) - Core 4 . Depth A 5 y Derrintion Cluster Physiographic Zone eS Sediment Type Age Cluster} Physiographic Zone 2 Mangrove Swamp (Coastal) 2 Mangrove Swamp (Coastal) 10. =| present 4 Freshwater Marsh with Hammocks 5 pe) 6 Headwater Marsh (Upper) Organic-rich “ : 20. 3 Sa! "4, Gashounte 2 Mangrove Swamp (Coastal) 30 Mangrove Swamp (Channel) Muds Z Mangroves wauin) constal) 40 =| Red Mangrove Peat 2 Mangrove Swamp (Coastal) : Mangrove Swamp (Coastal) 50am 2 Mangrove Swamp (Coastal) Mangrove S' Inner) = : bah eer Naas 60. | 2 Mangrove Swamp (Coastal) 2 Mangrove Swamp (Coastal) ==] 70S 1 Mangrove Swamp (Inner) 2 Mangrove Swamp (Coastal) 80 Excluded / Low Pollen Sum 2 Mangrove Swamp (Coastal) ~_| Tan Mudstone to 2 Mangrove Swamp (Coastal) pOgeres| Wackestone Excluded / Low Pollen Sum Muddy Peat with 2 Mangrove Swamp (Coastal) 100 __| = Mangrove Roots aa) 2 Mangrove Swamp (Coastal) 2 Mangrove Swamp (Coastal) LLU _| Gray Mudstone to | 2,390+60 1 Mangrove Swamp (Inner) 120 peewee] Se aa YBP 2 Mangrove Swamp (Coastal) 2 Mangrove S Coastal = angrove Swamp) (Cosetal) 130, 2: Mangrove Swamp (Coastal) = 1 Mangrove Swamp (Inner) 140 _] € 1 Mangrove Swamp (Inner) 1500 —) Red Mangrove Peat 2 Mangrove Swamp (Coastal) 3 = a=] Mang: S 4 . 2,880+60 2, Mangrove Swamp (Coastal) = 1 Aangrove Swamp (Inner) 160+ Gray Mudstone to ans cs) 2 Mangrove Swamp (Coastal) 4 Jacke 2 Mangrove Swamp (Coastal) 170 Wackestone g Pp 3 Mangrove Swamp (Channel) 180 4 Red Mangrove 1) aneroNe Sere (nes) 190° 4 sone Excluded / Low Pollen Sum Peat 3 Mangrove Swamp (Channel) _| Red Mangrove Peat Sam 2 Mangrove Swamp (Coastal) 200 __] YBP 8 Brackish 210° 2 Mangrove Swamp (Coastal) 8 Brackish 220) aaa 4 Freshwater Marsh with Hammocks 23 0sums| Mixed Marl 8 Brackish 240 "| Quartz Sand and Peat 8 Brackish 950 7 8 Brackish Text-figure 9.—Stratigraphic column of core 59-T1l (modified 260... Excluded / Low Pollen Sum from Riegel, 1965) and surface cluster group associations for sam- 7 Bedrock ples. Sample depths are indicated in gray. ilar. All multivariate statistical analyses were complet- ed using SYSTAT version 6.0 (SPSS Inc. 1996). Results for Vertical Sedimentary Sequences The results of discriminant analysis of core 59-T1 with the surface pollen zone data set assigned samples 84-92 cm, 190-198 cm, 221—229 cm, 236-242 cm, 251-259 cm, and 297-305 cm to the mangrove swamp surface cluster group | (Text-fig. 9). Samples O—8 cm, 8-15 cm, 38—45 cm, 53-61 cm, 69-77 cm, 99-107 cm, 114—122 cm, 130-138 cm, 145—153 cm, 160—168 em, 175-183 cm, 205-213 cm, 266—272 cm, and 320— 328 cm were assigned to the mangrove swamp surface cluster group 2. Samples 282-290 cm and 312-320 cm were assigned to the mangrove swamp surface cluster group 3. Samples 22—30 cm and 366-374 cm were assigned to the freshwater marsh surface cluster group 4. Samples 335-343 cm, 351—359 cm, 381—389 cm, and 389-397 cm were assigned to the brackish and transitional marsh cluster group 8 (Text-fig. 9). The discriminant analysis of core 9411—7 with the surface data set grouped sample 69 cm with the man- grove swamp surface cluster group | (Text-fig. 10). Samples 35 cm, 46 cm, 58 cm, 104 cm, 120 cm, 130 Text-figure 10.—Stratigraphic column of core 9411-7 (modified from Gelsanliter, 1996) and surface cluster group associations. Sam- ple depths are indicated in gray. em, 145 cm, 155 cm, 165 cm, and 205 cm were grouped with the mangrove swamp surface cluster group 2. Sample 21 cm was grouped with the man- grove swamp surface cluster group 3. Sample 10 cm was grouped with the headwater marsh surface cluster group 6. Sample 248 cm was grouped with the brack- ish and transitional marsh surface cluster group 8. Samples 79 cm, 90 cm, and 188 cm were excluded from discriminant analysis because of low pollen counts (Text-fig. 10). DISCUSSION Discriminant analysis of samples from core 59-T1 with the surface data set indicates that the overall se- quence went from basal brackish and freshwater marsh environments to dominantly mangrove swamp envi- ronments towards the present surface. These mangrove environments shifted from mixed mangrove environ- ments to predominantly coastal environments upwards in the core. This sequence suggests an overall trans- gression of southwest Florida, an interpretation sup- ported by Riegel (1965) and Spackman er al. (1966) BULLETIN 361 124 90 VC 6s 00 Pl 81 (ETE (G)! 00 00 VC (Gi)! Wd L6E—-86€ Se Site IS 90 OTI eal: (ew) 00 00 90 00 $6 W9 68E-18e SO EXE 86 00) £6 Cy! rl 00 a0) 00 00 LG wd pLe—-99e FO ST V8 L0 (46 Jer! ool 00 00 L0 LO NS wd 6SE-1SE 00 00 s0 (ONE CLI 00 CLI 00 OT s0 sO cel wid EpE-SEE 00 90 00 00 90 00 96 OG cal all 90 ses Wd 8Ct—-OCE 00 00 00 90 Oe Gl OTT 00 00 00 (Gli 88P wo Q@E-CIE 00 00 00 90 00 cl OCI 00 90 00 90 pss wd COE—-L6~ 00 00 00 00 00 Cl Ol TI 90 90 90 £9 W9 06T-T8T 00 00 00 00 Vl Dal ost ry! [E\! (ae Ei VEP Wd CLT-99C 00 90 00 00 00 90 OCI 90 (e! 00 vY 8°TS wd 6S7-IST 00 90 00 00 90 90 L6 00 Ul 90 ve OL9 Wd CHT-9ET 00 00 00 00 00 90 6Cl 00 Dae ei! ve 109 WIS 6CC~I1CC 00 00 00 00 Ve 00 O9T 00 90 cl Up 6LY wd €1c-SO0C 00 SO OT 00 Ol ol (Si! 00 OT ol (SAL eLy WW 861-061 00 00 SO 00 SO ima 6s 00 SO a EG L8e wd €8I-SLI 00 90 00 00 90 90 Gi Vl ST LE £8 9 eV wd 891—O9I 00 00 00 00 cl 61 90 L8 61 cl 89 CLV wd €CI—-SPrl 00 00 00 00 61 00 SYP 60 se ete 66 OEP wo §el—-Oel 00 SO a0) 00 en 00) ES ima HEX (NS Lol Cir ws @cI-vII SO 00 00 00 00 Ol OV 00 Ore ST 9TI £0S wu 101-66 00 00 00 00 00 SO ts al OT oO SE! [ESS WS 6-8 00 L0 L0 ry L0 00 Or 81 Ul LO | Lt w9 11-69 00 00 00 00 FO vO 08 el Ge Te Cl VB8e wo 19-€¢ 00 00 00 00 Vl 00 9S 00 OPI! GG [Ee Or Wd Cp-8e 00 00 00 00 Gi Gl ONS 90 eV Gn os Tle wd 0€—-CC 90 00 00 00 90 00 oH, 00 ONE 90 oP VCP wd CI-8 90 00 Gil 00 00 Gil T6 00 VT 68 19 L0¢ wd 8-0 Arey peoymouy ATI] Jey pened Ajwuey aspag A[turey sseig spodousyD HOMeS poomuoyNg c2oIsURLY SAOISURIY dAois UR ajdures Aasied DUDINISDS vanydwcy pyda I arooriedAD = aROUTLURID suvg sndip20u0) aU, yori pow aviajfy[oqui~) D1 piuuaaAy vsoydozyy -{D]NIUNSDT “T.L-6§ 2109 107 wep Aouanboiy us]][od—t 29PL WY N O’NEAL ET AL. POLLEN ZONATION 00 00 00 90 00 00 00 Sal 00 00 00 00 00 00 00 vl 00 00 00 OT 00 00 00 (elt 00 90 00 1 00 00 00 90 00 00 00 cl 00 00 00 Vl 00 00 00 90 00 00 00 90 00 00 00 00 00 00 00 00 00 00 00 0) 00 00 00 00 00 00 00 00 00 00 00 90 00 00 00 a0) 00 00 00 a0) 00 00 00 00 00 00 00 a0) 00 00 00 00 00 FO 00 80 00 00 00 ol 00 00 90 VC 00 00 00 6€ 00 00 00 61 SNUIXDAY snylupjpyday viuasny soqeiodiy, 00 00 00 r0 00 00 90 00 00 90 00 00 00 00 00 00 00 00 sO 00 00 SO r0 00 SO 90 00 90 SNL] 00 00 00 00 a0) 00 00 00 90 00 00 90 00 00 00 a0) 90 90 00 00 00 00 r0 00 00 00 00 90 sniopw 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 i 00 00 50 00 00 50 r0 r0 50 90 00 i) MOTTIAN xyes 90 ox) ox) 00 ox) 00 00 00 00 00 00 00 00 00 00 ox) 00 00 00 00 00 00 +0 ox) 00 00 00 90 ATIOH xal] 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 DE 00 Wd /6¢-86£ 00 8s 00 Wd 68E-I8E 00 or 0) Wd plLe—-99E 00 ev a0) wd 6CE-ICE 00 CT 00 wd €pE-CEE 00 VT 00 wid 87E-OTE 00 ST 00 wo OCE-TIE 00 00 00 wd COE—-L6T 00 90 00 Wd ()6T-T8T 00 90 00 wd TL7—-99T 00 El 00 Wd 6CT-IST 00 00 00 Wd ThT7—-9ET 00 Gi! 00 Wd 677-177 00 90 00 Wd €1Z—-SOT 00 OT 00 WO 861-061 00 00 00 wo €8I-CLI 00 00 00 Wd 891-091 00 00 00 wo €CI—Crl 00 OT 00 wo §¢I—-O€l 00 OT 00 wo CCI-¢I11 00 00 00 wd 101-66 00 a0) 00 Wd 76-8 00 00 00 wid //—-69 00 80 00 wd 19-¢€¢ 00 0) 00 Wd Ch-8e 00 ST 00 Wd O€-CT 00 (Gl 00 wo CI-8 00 Oe 00 wd 8-0 sysoduioj = woMIappel_ ajduies araory|AydoAiea) =paam yRuUIS arooruosA|og DIADINII) ‘papuarxy—p a1qeL BULLETIN 361 126 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 snyy 00 00 00 LAV, 00 00 00 90 00 00 00 ONE 00 00 00 vt 00 00 a0) s0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 90 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 90 00 00 00 00 00 00 00 Ul 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 a0) 90 00 00 00 00 00 00 el 00 00 00 00 pIawuvoy pauadpy adrin SINPIOAQC, “JO SHIA (G! 00 00 00 00 00 00 00 00 00 00 00 vO 00 00 vO 00 00 00 00 90 00 00 90 00 00 00 90 00 00 90 00 90 00 00 00 90 00 00 00 00 00 00 00 00 00 00 90 90 00 00 90 00 00 00 00 SO 00 00 00 0) 00 00 00 ny 00 00 90 cl 00 00 00 vl 00 00 00 SO 00 00 00 00 00 00 00 ol 00 00 00 LO 00 00 00 (GE 00 00 00 0) 00 00 00 (Ql 00 00 00 Sal 00 00 00 SC 00 00 00 ssaidAp DSSANT DMD IOplv UNIPOXD | snuyy 00 00 00 FO 00 00 90 00 cl 90 00 00 90 00 iS" 00 ea 00 val EG 00 Ol 81 (| 91 81 90 (|! unipibovUuy Cts ST oO 00 VC 61 ONS 00 VT 90 OG 90 00 SI ia0) at 6T SiG 61 00 0:0 a0) Tl 60 OT VC DME cae APO SNIAANE) 00 00 00 00 00 00 90 00 00 Lae 00 00 00 00 0 Ul 00 00 00 00 00 0 00 FO sO 00 90 90 avaonjodes WS /6£-86e W9 68E-18e wd pLE—99E W9 6¢e-1Se WOlEveSSce WS 8CE-0CE wd OCE-CLE WS COt-L6C WS ()6T-C8T WS CL7-997 wd 6SC-ISZ WIS CVC—-9ET WS 6¢CC-1C7 ws €1c-S07 WW 861-061 WS €8I-SLI wW9 891-091 wo €CI—SrI m9 8el—Oel wd CCI-FIT WS 101-66 wd ¢6-8 wo //—69 wd T9-€S wd Ch-8e wld 0E—CC uid ¢[-8 wuld g-() ajduirs ‘popuarxq— hp alge 127 POLLEN ZONATION: O’NEAL ET AL. OSI 691 Vil 0'6C 00 00 00 00 00 00 00 00 00 00 00 WS L6E-86E trl SSI S6 OBE 00 00 00 00 00 00 00 00 00 00 00 WS 68¢-18e Ss tol 6 Me) 00 00 00 00 00 00 00 00 a0) 00 00 WO PEESOOS O8T S8C [Es V8c 00 00 00 00 00 00 00 00 00 00 00 WS 6S ESSE 86l £0C VC O9¢ 00 00 00 00 00 00 00 00 00 00 00 WE) SASL L¥rl 9S HENS Pst 00 00 00 00 00 00 00 00 90 90 00 Wo"8CE—0CE 9S I F9l TS) £81 00 00 00 00 00 00 00 00 00 00 00 WOO CtROhs OSI 991 L6 L8i 00 00 00 00 00 00 00 00 00 00 00 WS SOESLOC Srl P9l Sl SOI 00 00 00 00 00 00 00 00 90 00 00 WS ()67-C8C SSI SLI Fil (ENS | 00 00 00 00 00 00 00 00 90 00 00 KCL GRI9G trl 6SI Vol 9TI 00 00 00 00 00 00 00 00 90 00 00 WS 6ST-1ST col OLI GE Ls 00 00 00 00 00 00 00 00 Ul 00 00 WOTCVG-9GG 8S 8ZI Cal LEAS 00 00 00 00 00 00 00 00 00 00 00 WO 6CCaCS Srl 691 cri Galil 00 00 00 00 00 00 00 00 00 00 00 Wo €TC-S07 esl SOT 601 LOl 00 00 00 00 00 00 00 00 00 SO 00 W9 §61-061 891 981 66 6Cl 00 00 00 00 00 00 00 00 a0) a0) 00 0) SS S/O! 991 18] £8 ULI 00 00 00 00 00 00 00 00 90 90 00 Wo 891—-09T srl 19] v8 orl 00 00 00 00 00 00 00 00 om 00 00 WOES TSSyI 981 LIT oll ST 00 00 00 00 00 00 00 00 60 00 00 wo SE I—-OET O91 L8I LYl LOI 00 00 00 00 00 00 00 00 a0) a0) 00 Wo ColSV PT CLI 661 Cel oT 00 00 00 00 00 00 00 00 a0) 0) 00 W195" 201566 Os rol OL Vel 00 00 00 00 00 00 00 00 a0) 00 00 WS" C6578 CET PLE Psi 601 00 00 00 00 00 00 00 00 00 r0 00 COT 69) 961 PCC Ll 6Cl 00 00 00 00 00 00 00 00 00 00 00 ws [9-E¢ orl c8I Vs Srl 00 00 00 00 00 00 00 00 ol 00 00 Wd Cr-8E trl rol STI OST 00 00 00 00 00 00 00 00 90 (Gi) 00 MSIOESCC cri cs] 18 DOT 00 00 00 00 00 00 00 00 90 00 00 ws CI=8 Isl £9] UL SS 00 00 00 00 00 00 00 00 cl 81 00 eee) t=(0) sonsneis 1of payunod aI, SNUI aq SAL piuap — Avydnny syjjodouoswoyy, wy wnuspydg — Ayturey wnip — ppuntusEQ. aeaoeyK|y ajdurg posn suieig = suring -wppinbiT -Dpqvyuy ‘yo smu) ueoH -od\jog avaorol” ‘papuaxq—"p 2qRL 128 BULLETIN 361 Table 5.—Pollen frequency data for core 9411-7. Rhizophora Avicennia Laguncularia Gramineae Cyperaceae Sample Red Black White Conocarpus — Batis Cheno- Grass Sawgrass Typha Nymphaea Sagittaria depth Mangrove Mangrove Mangrove Buttonwood Saltwort pods family family Cattail Water Lilly Arrowhead 10 cm 24.3 1.9 1.3 4.2 0.3 51.8 0.6 129) 1.3 0.0 1-3 21 cm 24.4 1.7 0.4 1.2 0.0 31.8 0.4 12 0.0 0.8 0.4 35 cm 15.1 5.8 1.2 5.8 0.6 33.1 3i5 2.9 3:5 0.0 1e7/ 46 cm Syle3} TES 0.0 1.5 0.0 29:9 37 0.0 0.0 0.0 0.7 58 cm 37.9 Del 0.7 2.8 0.0 32.4 2.1 0.7 0.0 0.0 0.0 69 cm 41.1 3.1 1.2 1.2 0.0 25.8 DES Pies) 0.0 0.0 0.0 79 cm 34.8 6.8 7.6 DS 0.0 12.9 eS) 0.8 0.0 0.0 0.0 90 cm 9.3 10.1 0.8 1.6 0.8 25.6 1.6 0.8 0.0 0.0 0.8 104 cm 17.4 SS) 2.2 0.0 0.7 15.9 0.0 4.3 0.0 0.0 0.0 120 cm 19 16.3 0.0 1e3} 1.3 11.3 6.3 6.3 0.0 0.0 0.0 130 cm 2235 10.3 1.1 ile 7/ 1.1 8.0 Pes} 1.1 0.0 0.0 0.0 145 cm 28.0 8.4 2.8 4.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 155 cm 24.6 8.4 NeF/ 1.1 0.0 5.6 1.1 1.1 0.0 0.0 0.0 165 cm 26.9 5.4 sf 1.1 0.5 O77 0.5 1.1 0.0 0.0 0.0 188 cm 29.3 0.0 0.7 4.1 0.0 0.0 0.0 0.0 2.0 0.0 0.0 205 cm 19.7 0.0 0.0 0.0 Le 22.5 45 Pep2 i697 0.6 1.7 248 cm Sul 0.0 1.3 0.0 0.0 3.8 3.8 11.5 0.0 4.5 3.8 Sample Umbelliferae Utricularia Polygonaceae Ilex Salix depth Celery family Bladderwort Composits Smart weed Holly Willow Morus Ficus Triporates 10 cm 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.0 21 cm 0.4 0.0 1.2 0.0 0.0 0.0 0.8 0.0 2.1 35 cm 0.0 0.0 0.0 0.6 0.0 0.6 0.0 0.0 122: 46 cm 0.7 0.0 0.7 0.0 0.0 0.0 0.7 0.0 0.7 58 cm 0.0 0.7 0.0 0.7 0.0 0.0 0.0 0.0 0.7 69 cm 0.0 0.0 1.2 0.0 0.0 0.0 0.0 0.0 le 79 cm 0.0 0.0 0.8 0.0 0.0 0.0 0.0 0.0 0.0 90 cm 0.0 0.0 23 0.0 23 0.8 0.0 0.0 2.3 104 cm 0.0 0.0 D2, 0.0 0.0 1.4 1.4 0.0 2.9 120 cm 0.0 0.0 6.3 0.6 0.0 4.4 0.0 0.0 0.6 130 cm 0.0 0.0 1.1 0.0 0.6 1.1 0.0 0.0 4.0 145 cm 0.0 0.0 0.0 1.4 0.7 0.0 0.0 0.0 0.0 155 cm 0.0 0.0 0.6 0.0 0.0 0.0 0.6 0.0 0.0 165 cm 0.0 0.0 1.1 0.0 0.0 0.0 0.0 0.0 0.0 188 cm 0.0 1.4 2 0.0 0.0 0.0 0.0 0.0 0.7 205 cm 0.0 0.0 NZ 0.6 0.0 0.6 0.0 0.0 Dee 248 cm 0.0 0.0 12.7 0.0 0.6 0.0 0.0 0.0 i) for the same core. Discriminant analysis using the sur- face pollen zonation is a sensitive enough measure to differentiate generally between the mangrove-domi- nated assemblages that are prevalent in the core. The assignment of core intervals between 328 cm and 190 cm to a mixture of mangrove swamp surface clusters (Text-fig. 9) is expected during the early stages of coastal transgression when variability in substrate type, hydroperiod, elevation, and varying proximity to brackish and freshwater marsh communities would contribute a variety of taxa to the sediment record. The upper 190 cm of core (essentially the last 2,800 years; Text-fig. 9) is assigned almost exclusively to mangrove swamp surface cluster 2, or that cluster represented by the coastal mangrove physiographic province, the de- position site of the core. This suggests that essentially modern conditions existed in the vicinity of the Harney River coastline for the last 2,800 years, a time surface that occurs within the muddy mangrove peat unit and is otherwise indistinguishable. Discriminant analysis of core 9411—7 with the sur- face pollen data set indicates a predominantly man- grove coastal environment of deposition for the core. However, core 9411-7 has been interpreted by Gel- sanliter (1996) to contain sedimentologic evidence that suggests a short-lived, high-frequency sea-level oscil- lation occurred in the overall transgressive sequence at approximately 2,400 ybp. Sedimentologic evidence for this sea-level oscillation first occurs in the form of Rhizophora peats prograding over subtidal marine car- POLLEN ZONATION: O'NEAL ET AL. 129 Table 5—Continued. Sample Quercus Alnus Taxodium depth Cephalanthus Fraxinus Sapotaceae Oak Anacardium Tricolpates Alder Carya Pinus Cypress 10 cm 0.0 0.0 0.0 0.3 0.0 1.0 0.0 0.0 2.9 1.0 21 cm 0.0 0.0 0.4 0.0 0.0 0.8 0.0 0.4 AUS) 33 35 cm 0.6 0.0 0.0 0.0 0.0 1.7 0.0 0.0 4.7 5.8 46 cm 0.0 0.0 3S 0.0 0.0 0.0 0.7 0.0 2.2 1S 58 cm 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2.8 Ql 69 cm 0.0 0.0 0.0 0.0 0.0 0.6 0.0 0.0 Sh7/ 0.6 79 cm 0.0 0.0 0.8 3.0 0.0 1.5 0.0 0.0 1.5 0.0 90 cm 0.0 0.0 0.0 0.0 0.8 1.6 0.0 0.0 6.2 0.0 104 cm 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 11.6 0.0 120 cm 0.6 0.0 0.0 0.0 0.6 0.6 0.0 0.0 6.3 0.0 130 cm 1.1 0.0 0.0 0.0 0.0 2.9 0.0 0.0 15.4 0.0 145 cm 0.7 0.7 0.0 0.0 0.0 0.0 0.0 0.0 24.5 0.0 155 cm 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 28.5 1.1 165 cm 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 25.3 0.0 188 cm 0.0 1.4 0.0 0.0 0.0 0.0 0.0 0.0 15.6 2.0 205 cm 0.0 0.0 0.0 0.0 0.0 0.0 0.6 0.0 5.6 0.0 248 cm 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 12.1 0.0 Sample Vitis cf. Polygala Others and Grains used depth Monocolpates Grape Inaperturate Ovoidites Milkwort Osmunda Polypodium unidentified Grains counted for statistics 10 cm 0.0 0.0 0.6 0.6 0.0 0.0 0.3 4.9 306 294 21 cm 0.0 0.4 2.1 0.0 0.0 0.4 1.2 20.7 242 183 35 cm 0.6 0.0 0.0 0.6 0.0 0.0 1.2 18.0 163 152 46 cm 0.0 0.0 2.2 0.0 0.7 0.0 0.0 11.2 122 113 58 cm 0.0 0.0 0.7 0.0 0.0 0.0 0.0 14.5 130 124 69 cm 0.0 0.0 0.0 0.0 0.0 0.0 0.0 16.0 145 137 79 cm 0.0 0.0 3.0 1.5 0.0 0.0 0.0 25.8 111 98 90 cm 1.6 0.0 2/3 0.0 0.0 0.0 1.6 27.1 105 87 104 cm 0.0 0.0 0.0 0.0 1.4 0.0 0.0 225 111 106 120 cm 0.0 0.0 2.5 0.0 0.0 1.9 4.4 16.3 130 112 130 cm 1.1 0.0 1.7 0.0 0.0 0.6 0.0 3357) 142 126 145 cm 0.0 0.0 0.0 0.0 0.0 0.0 0.0 52.4 107 102 155 cm 0.0 0.0 iT 0.0 0.0 0.0 0.0 32:9 140 133 165 cm 0.0 0.0 0.0 0.0 0.0 0.0 0.0 43.5 144 138 188 cm 0.0 0.0 3.4 1.4 0.0 0.0 0.0 48.3 102 89 205 cm 0.0 0.0 Ded: L7/ 0.0 leith 1.1 28.1 130 123 248 cm 0.0 0.0 0.0 25) 0.0 0.0 0.0 19.1 106 100 bonates (regression) at about 2,800 years before pre- sent (Text-fig. 10). This may be the event that stabi- lized the coastline in core 59-T1. Regressional man- grove peats are overlain by marine carbonate mud as the coast is transgressed. From 98 cm to 75 cm is a tan, supratidal carbonate mudstone. This represents a period of rapid sediment reworking following the sea- level oscillation centered around 2,400 ybp (Gelsan- liter, 1996). Rhizophora peats overlie the sequence to the depositional surface and indicate continual trans- gression. Discriminant analysis of core samples with the surface pollen data set yields variable results that attest to both the sensitivities and limitations of this method. Sample 248 cm is correctly attributed to the brackish marsh, as the sample is from reworked basal Holocene quartz sands. Samples 205 cm to 104 cm are all assigned to mangrove swamp cluster 2, represent- ing the coastal margin physiographic province (Text- figs. 7 and 10). Cluster 2 is represented by the widest variety of taxa in the mangrove swamp clusters and is characterized by higher percentages of chenopods and Avicennia pollen. These characteristics reflect the fact that the coastal margin mangrove swamp has the most variability in substrate type, hydroperiod, and eleva- tion. It is therefore reasonable that discriminant anal- ysis assigned all of these intervals to cluster 2 regard- less of the fact that the host sediments varied from Rhizophora peats (both transgressive and regressive) to marine carbonate muds. All these samples shared high overall percentages of Rhizophora pollen with 130 BULLETIN 361 complex mixtures of Avicennia, chenopods, Pinus, and other taxa, yet all were deposited in close proximity to the coastal margin. Samples 90 cm and 79 cm were both excluded from discriminant analysis because of low overall pollen sums. This is significant in that both samples come from the tan, supratidal carbonate mudstone that rep- resents a period of rapid sediment reworking and build-up of a supratidal coastal barrier (Gelsanliter, 1996). These intervals undoubtedly have low pollen sums because the pollen signal was inundated by re- worked marine sediment. The upper 58 cm of the core sequence are discriminated to cluster 2 (coastal man- grove swamp, 3 samples), cluster 3 (mangrove swamps along the Shark River Slough), and cluster 6 (upper headwater marsh). This sequence represents an overall change upwards to reflect the influence of proximity to brackish and freshwater taxa. Cluster 3 incorporates higher percentages of triporates, cheno- pods, and Conocarpus, while cluster 6 is dominated by chenopods. These discriminant assignments reflect the present proximity of the depositional site to the inner bays and its inclusion in the brackish to transi- tional marsh physiographic province (Text-fig. 7). While discriminant analysis of core 941 1—7 with the surface pollen data set initially suggests that this tech- nique is not sensitive enough to differentiate signifi- cant sedimentologic variability in a core sequence, it does yield predictable results. Discriminant analysis indicates an overall transgression in the core sequence that is present and correctly positions the contempo- rary depositional environment. The method, however, fails to recognize a sea-level oscillation because it as- signs all samples throughout the interval to the coastal mangrove swamp. Undoubtedly, the pollen signature of sediments deposited during this oscillation were, in fact, representative of the coastal mangrove swamp. CONCLUSIONS In South Florida, the boundaries between vegetation communities are commonly well defined, but bound- aries between pollen zones are blurred because of mix- ing of pollen by fluvial, tidal, and atmospheric pro- cesses. Multivariate statistical techniques provide a sensitive and objective means of delineating the dis- tribution of pollen and spores in the study area. Cluster analysis of pollen and spore types from sur- ficial deposits in the study area indicates that individ- ual taxa typically are not environmentally restricted and, in most environments, there are no single indi- cator species because of broadly overlapping geo- graphic ranges. Multivariate analysis of pollen assem- blages is required to separate surface sample pollen assemblages into distinct pollen zones. Cluster analysis of pollen and spores from surface sample sites pro- duced five clusters, or pollen zones, containing a total of 10 sub-clusters that help delineate subtle differences within each zone. The spatial distribution of these pol- len zones strongly corresponds to the major physio- graphic provinces of the area. These pollen zones are: 1) mangrove swamp, 2) brackish marsh, 3) freshwater marsh, 4) headwater marsh, and 5) upland complex. The correlation between the spatial distribution of clusters and physiographic provinces in the study area strongly suggests that the surface pollen cluster group- ings have environmental meaning and that pollen can provide valuable information for paleoenvironmental reconstructions. Discriminant analysis underscores the distinctiveness of the environmental groupings ob- tained from cluster analysis. It also supplies the objec- tive criteria and a methodological protocol for accu- rately assigning group membership to pollen and spore assemblages from vertical stratigraphic sequences and ultimately facilitates paleoecological interpretations. A visual comparison of unknown samples with the 18 key taxa identified herein indicates that the reduced set is also useful in making a first approximation in as- signing an unknown sample to a surface pollen zone. Results from two cores, 59-T1 and 9411-7, indicate the methods used in the study can identify the overall late Holocene transgression of South Florida from pol- len assemblages in vertical sequences and can differ- entiate among different mangrove swamp communities as coastlines are first transgressed and then stabilized. The method is limited in its ability to differentiate short-lived changes in coastal configuration (7.e., sea- level oscillations) as long as the overall environment remains in close proximity to the coastal zone. De- tailed sedimentologic work, combined with palynolog- ical analysis is required, especially where sediment re- working has occurred. REFERENCES CITED Bancroft, G.T., Strong, A.M., Sawicki, R.J., Hoffman, W., and Jewell, S.D. 1994. Relationship among wading bird foraging patterns, colony locations, and hydrology of the Everglades. in Everglades: The Ecosystem and its Restoration. S.M. Davis and J.C. Ogden, eds., St. Lucie Press, Delray Beach, Florida, pp. 615-659. Bartow, S.M., Craft, C.B., Richardson, C.J. 1996. Reconstructing historical changes in Everglades plant community composition using pollen distributions in peat. POLLEN ZONATION: O’ NEAL ET AL. 131 Journal of Lake and Reservoir Management, vol. 12, pp. 313-322. Birks, H.J., Webb, B. T., and Berti, A.A. 1975. Numerical analysis of surface pollen samples from central Canada: a comparison of methods. Review of Paleobot- any and Palynology, vol. 20, pp. 133-169. Brewster-Wingard, G.L., Ishman, S.E., Willard, D.A., Edwards, L.E., and Holmes, C.W. 1997. Preliminary paleontologic report on cores 19A and 19B, from Russell Bank, Everglades National Park, Florida Bay. U.S. Geological Survey Open-file Report 97—460, 29 pp. Cohen, A.D. 1968. The petrology of some peats of southern Florida (with special reference to the origin of coal). Unpublished Ph.D. thesis, Pennsylvania State University, 352 pp. Craighead, F.C., and Gilbert, V.C. 1962. The effects of Hurricane Donna on the vegetation of southern Florida. Quarterly Journal of the Florida Acad- emy of Science, vol. 25, pp. 1-28. Davis, J.H., Jr. 1943. The natural features of southern Florida, especially the vegetation and the Everglades. Bulletin 25, Florida Geo- logical Survey, Tallahassee, Florida. 311 pp. Davis, J.C. 1986. Statistical and data analysis in geology. 2 edition. John Wiley & Sons, New York, 646 pp. Dean, W.E., Jr. 1974. Determination of carbonate and organic matter in calcar- eous sediments and sedimentary rocks by loss on ignition: comparison with other methods. Journal of Sedimentary Petrology, vol. 44, p. 242-248. Gelsanliter, S.G. 1996. Holocene stratigraphy of the Chatam River Region, Southwestern Florida; With a reevaluation of the Late Ho- locene sea-level curve. Unpublished M.S. thesis, The Uni- versity of Miami, Miami, Florida. 182 pp. Gunderson, L.H. 1994. Vegetation in the Everglades: Determinants of community composition. in Everglades: The Ecosystem and its Res- toration. S.M. Davis and J.C. Ogden, eds., St. Lucie Press, Delray Beach, Florida. pp. 323-340. Gunderson, L.H., and Snyder, J.R. 1992. Fire patterns in the southern Everglades. in Everglades: The Ecosystem and its Restoration. S.M. Davis and J.C. Ogden, eds., St. Lucie Press, Delray Beach, Florida, pp. 291-306. Habib, D., Eshet, Y., and Van Pelt, R. 1994. Palynology of sedimentary cycles. in Sedimentation of Organic Particles. A. Traverse, ed., Cambridge University Press, pp. 311-335. Hoffmeister, J.E., Stockman, K.W., and Multer, H.G. 1967. Miami Limestone of Florida and its recent Bahamian counterpart. American Association of Petroleum Geolo- gists Bulletin, vol. 78, pp. 175-190. Kachigan, S.K. 1991. Multivariate statistical analysis: A conceptual introduc- tion. Radius Press, New York, 303 pp. Kuehn, D.W. 1980. Offshore transgressive peat deposits of southwest Florida: Evidence for a late Holocene rise of sea level. Unpub- lished MLS. thesis, Pennsylvania State University, 104 pp. Loveless, C.M. 1959. A study of the vegetation of the Florida Everglades. Ecol- ogy, vol. 40, pp. 1-9. Mclvor, C.C., Ley, J.A., and Bjork, R.D. 1994. Changes in freshwater inflow from the Everglades to Flor- ida Bay including effects on biota and biotic processes: A review. in Everglades: The Ecosystem and its Resto- ration. S.M. Davis and J.C. Ogden, eds., St. Lucie Press, Delray Beach, Florida, pp. 117—148. Meeder, J.F. 1987. The paleoecology, petrology, and depositional model of the Pliocene Tamiami Formation, southwest Florida (with special reference to coral and reef development). Unpub- lished Ph.D. dissertation, University of Miami, 249 pp. Meeder, J.F., Ross, R.S, Telesnicki, G., Ruiz, P.L., and Sah, J.P. 1996. Vegetation analysis in the C-111/Taylor Slough Basin. Fi- nal Report Contract C-4244, Southeast Environmental Re- search Program, Florida International University, Miami, Florida, 90 pp. Moore, P.D., Webb, J.A., and Collinson, M.E. 1991. Pollen Analysis. Blackwell Scientific Publishing, Oxford, 216 pp. Olmstead, I.C., and Loope, L.L. 1984. Plant communities of Everglades National Park. in En- vironments of South Florida: Present and Past II. PJ. Gleason, ed., Miami Geological Society, Coral Gables, Florida, pp. 167—184. Parker, G.G., and Cooke, C.W. 1944. Late Cenozoic geology of southern Florida, with a dis- cussion of ground water. Florida Geological Survey Bul- letin 27, 119 pp. Parker, G.G., Hoy, N.D., and Schroeder, M.C. 1955. Geology of water resources of southeastern Florida with special reference to the geology and groundwater of the Miami area. U.S. Geological Survey Water Resources Pa- per 1255. Puri, H.S. and Vernon, R.O. 1959. Summary of the geology of Florida and a guidebook to classic exposures. Florida Geologic Survey, Special Pub- lication 5, Tallahassee, Florida, 255 pp. Rich, F.J., Kuehn, D., and Davies, T.D. 1982. The paleoecological significance of Ovoidites. Palynolo- gy, vol. 6, pp. 19-28. Riegel, W.L. 1965. Palynology of Environments of Peat Formation in South- western Florida. Unpublished Ph.D. thesis, Pennsylvania State University, 189 pp. Smith, T.J., III, Hudson, J.H., Robblee, M.B., Powell, G.V.N., and Isdale, P.J. 1989. Freshwater flow from the Everglades to Florida Bay: A historical reconstruction based on fluorescent banding in the coral Solenastrea bournoni. Bulletin Marine Science, vol. 44, pp. 274-282. Spackman, W., Dolsen, C.P., and Riegel, W. 1966. Phytogenic organic sediments and sedimentary environ- ments in the Everglades—Mangrove Complex, Part I: Ey- idence of a transgressing sea and its effects on environ- ments of the Shark River area of southwestern Florida. Palaeontographica, vol. 117, pp. 135-152. Stockmarr, J. 1971. Tablets with spores used in absolute pollen analysis. Pol- len et Spores, vol. 13, 614-621. Wanless, H.R., Tedesco, L.P., Rossinsky, V., and Dravis, J.J. 1989. Carbonate Environments and Sequences of Caicos Plat- 132 BULLETIN 361 form with an Introductory Evaluation of South Florida. in 28" International Geologic Congress Field Trip Guide- book T1374, American Geophysical Union, 75 pp. Wanless, H.R., Tedesco, L.P., Risi, J.A., Bischof, B.G., and Gel- sanliter, S. 1995. The role of storm processes on the growth and evolution of coastal and shallow marine sedimentary environments in South Florida. 1*‘ SEPM Congress on Sedimentary Ge- ology, St. Petersburg, Florida, 137 pp. Ward, J.H. 1963. Hierarchical grouping to optimize an objective function. Journal of the American Statistical Association, vol. 58, pas Willard, D.A. and Holmes, C.W. 1997. Pollen and geochronological data from South Florida: Taylor Creek Site 2. U.S. Geological Survey Open-file Report 97-35, 14 pp. Winkler, M.J., Sanford, P.R., and Kaplan, S.W. 1998. Holocene hydrologic and vegetation history of the south- ern Everglades. Geological Society of America, Abstracts with Programs, vol. 30, p. A309. Wood, G.D., Gabriel, A.M., and Lawson, J.C. 1996. Palynological techniques—processing and microscopy, in J. Jansonius, and D.C. McGregor, eds., Palynology: Prin- ciples and Applications. American Association of Strati- graphic Palynologists. Salt Lake City, Utah, pp. 29-50. CHAPTER 7 A CENTURY OF ENVIRONMENTAL VARIABILITY IN OYSTER BAY USING OSTRACODE ECOLOGICAL AND ISOTOPIC DATA AS PALEOENVIRONMENTAL TOOLS Cartos A. ALVAREZ ZARIKIAN', PETER K. SWART!, TERRI Hoop!, Pat L. BLACKWELDER!2, TERRY A. NELSEN*, AND CHARLES FEATHERSTONE: 'Marine Geology and Geophysics, University of Miami-RSMAS, 4600 Rickenbacker Causeway, Virginia Key, FL 33149 °Nova Southeastern University, Oceanographic Center, 8000 N. Ocean Dr., Dania, FL 33004 SNOAA-AOML-OCD, 4301 Rickenbacker Causeway, Virginia Key, FL 33149 ABSTRACT Stable isotopic analysis (6'SO and 6'C) and characterization of the ostracode community structure were carried out from a high-resolution sediment-core recovered from Oyster Bay in the west of the Everglades National Park. Because of its location, between the Shark River Slough (SRS) and the Gulf of Mexico, the Oyster Bay core locality experiences extreme salinity fluctuations due to the interaction of freshwater run-off, precipitation, and marine water inputs. Ostracode population dynamics and isotopic variability over the 20" century are linked to natural and anthropogenic forces that affect the South Florida coastal ecosystem on interannual to decadal time scales. Three ostracode assemblages can be recognized within the 100-year sediment- core record: the first extending from the turn of the century to about 1950; the second, from the early 1950s to the late 1970s; and the third to core recovery in 1995. An abrupt decrease in ostracode abundance, species diversity, and shifts in species dominance occur in the mid-1980s and reflect episodes of environmental stress. Markedly enriched 6!SO values from the ostracode Peratocytheridea setipunctata and the benthic foraminifer Ammonia parkinsoniana typica at this time are concurrent with a major regional drought in South Florida, as well as with documented algal blooms and major die-off of sea grasses in Florida Bay. In addition, the timing of these events is contem- poraneous to the onset of the South Florida Water Management District (SFWMD) “Rainfall Plan” and the closing of the Buttonwood canal. Higher ostracode abundance and species richness occurs between the late-1950s and late-1970s. Stable isotopic data and ostracode assemblage characteristics suggest a period of relative environmental stability and possibly improved water circulation in Whitewater Bay and Oyster Bay. Fluctuations in community structure during this time are more systematic and appear to be temporally correlated to rainfall variability patterns. Water management policies at this time are also discernable from the microfaunal and isotopic record, particularly the Congressionally mandated Monthly Minimum Allocation Plan of water supply to SRS. Before 1950, hurricane events and their effects are the major cause for immediate modifications within the ostracode community, though our data show that ostracode populations are capable of rapid recovery. Over the complete record of the last century, the effects of water management practices can be assessed from information embedded in the ostracode record. Nevertheless, the effects of natural climatic variability in Oyster Bay appear to outweigh the impact of anthropogenic forces. INTRODUCTION Over the past decade, scientists have used proxy re- cords of environmental conditions in Florida Bay and its environs to examine the paleoecological history of this region (Brewster- Wingard et al., 2000; Halley and Roulier, 1999; Swart et al., 1996, 1999; Nelsen et al., in press). Benthic microfaunal communities preserved in undisturbed sediment records have shown great promise for the reconstruction of paleoenvironmental fluctuations (Alvarez Zarikian et al., 1999a, 1999b; Brewster-Wingard and Ishman, 1999; Cronin ef al., 2000; Dwyer and Cronin, 2000; Hood et al., 1998: Ishman, 2000). Ostracodes have proven particularly valuable for such reconstructions because they are abundant in the marine and brackish water environ- ments of South Florida (Puri and Hulings, 1957; Puri, 1960; Benda and Puri, 1962; Keyser, 1975, 1977). In addition, they have specific ecological requirements and well defined salinity tolerances (Neal, 1988). Moreover, ostracodes rapidly secrete a calcitic bivalve shell (Turpen and Angell, 1971), which with genetic influences, records the isotopic composition of the aquatic environment, thus providing a geochemical snapshot of the chemical conditions of the water in which they lived. The lower Everglades National Park is comprised of a north-south ecosystem succession ranging from large flat wetlands in the north to shallow bays, lakes and channels in the south, which are mostly filled with mangrove swamp deposits and bordered by mangrove forests. The environmental transition into the coastal zone is gradual and it extends into the shallow mud- banks and semi-restricted basins of Florida Bay. To the west and north of Cape Sable, the 1—2 meter-deep Whitewater Bay extends to the northwest through the mangrove forest and Oyster Bay until opening up to 134 BULLETIN 361 # Oyster Bay core ;Whitewater Bay : d Sees Florida Bay* *~_ v 2 oF 5 Text-figure 1—Location Map of Oyster and Florida Bays. Sediment core location in Oyster Bay represented by black cylinder. the Gulf of Mexico. Direct freshwater runoff from the Everglades into Florida Bay and adjacent bays is pri- marily through the natural drainage basins of Shark River and Taylor Sloughs, and artificially from the C- 111 Canal. To the west, the park is heavily influenced by the marine waters of the Gulf. Freshwater input from canals and watersheds that flow into Florida Bay is strongly influenced by rainfall and freshwater man- agement policies of the South Florida Water Manage- ment District (Nelsen ef al., in press; Rudnick er al., 1999). Numerous hydrological modifications have impact- ed the Everglades natural ecosystem during the 20th century. Among these are the fragmentation of the wetlands due to construction of a massive network of canals and levees for water supply and flood control, and the loss of extensive wetland area to agriculture and residential development (Davis and Ogden, 1994). Prior to human impact, natural forces and seasonal cli- matic variability were the main factors controlling hy- drological conditions in the area. Increased salinity and nutrient concentration in Florida Bay (Mclvor et al., 1994), as well as algal blooms and major seagrass die- offs (Fourqurean and Robblee, 1999; Robblee er al., 1991), have raised growing concerns as to whether the origin of these changes are anthropogenic or are part of a natural cycle of climatic variability. Micropaleontological and stable isotopic data ob- tained from a high deposition rate sediment-core col- lected in Oyster Bay are presented here. These data have allowed interpretation of interannual to decadal changes in hydrological conditions from this area within the Everglades National Park. Because of its location, adjacent to Shark River and the Gulf of Mex- ico, the Oyster Bay core locality experiences extreme salinity fluctuations (4 to >40 parts of salinity, Boyer et al., 1997) due to the interaction of freshwater run- off, precipitation and marine water inputs. Because of the wide range of environmental conditions, this site is ideally located to examine the response and sensi- tivity of ostracode populations and their isotopic com- position to environmental change over the last century. CORE SELECTION AND GEOCHRONOLOGY An undisturbed sediment record is a pre-requisite for the meaningful interpretation and reconstruction of paleoenvironmental changes. The Oyster Bay core (Text-fig. 1) used in this study is one of many collected in Florida and adjacent bays during the last four years. It was recovered from seagrass-free soft bottom sedi- ments in shallow water (1 m). This high sedimentation rate core has been the focus of an interdisciplinary study to reconstruct Oyster Bay’s paleoenvironmental record. Analyses that have been completed include mi- crofaunal and pollen assemblage, stable isotope, or- ganic and inorganic carbon, mineralogy and heavy metals (Nelsen ef al., in press). The location of the sediment core was carefully tar- OSTRACODE PALEOENVIRONMENTAL RECONSTRUCTION: ALVAREZ ZARIKIAN ET AL. 135 geted from review of sequential aerial photographs (1927—present) and published data on the dynamics of banks and deltas in Florida Bay (Wanless and Tagett, 1989). Aerial photographs helped identify sites that had been free of macro vegetation since the time of the earliest aerial photograph. Subsequent reconnais- sance coring sought to verify that the site was an area of active sediment accumulation and that it had well- preserved stratification (minimal bioturbation activity) (Nelsen et al., in press). The |.5-m long Oyster Bay core was examined for stratification/disruption utilizing X-radiography to as- sure that sediment geochronology would yield inter- pretable sequences. Stratification in the sediment core was clear, with laminations consisting of alternations of mangrove organics, carbonate silt, and fine quartz. The core was age-dated using the *!°Pb-dating tech- nique (Nelsen ef al., in press), described, and photo- graphed for evaluation of sediment type and structures. The sediment accumulation rates derived from the pro- file of excess 7!°Pb were approximately 1.1 cm/yr (0.6 g/cm?/yr). The geochronology for the Oyster Bay core was extended back to the turn of the century by ex- trapolating the activity of excess *!°Pb downcore. In addition to providing a time-line and accumulation rate information, fine-structural features were observed in the excess 7!°Pb profile including sediment erosion/de- position bands that are tied by year to hurricane events. These discontinuities appear as lower levels of excess *!°Pb than would be expected from the overall trend. These lower levels are most likely a result of the com- bined effects of losing sediment from the core site dur- ing a storm and input of sediments with lower levels of excess 7!°Pb, i.e., older sediments or organic-rich debris, from upland or other sources (Nelsen ef al., in press). In the Oyster Bay core site, sudden shifts in the *!°Pb activity correspond (within +3 years) to the years of 1960, 1948, and 1935 (Text-fig. 2) and are likely the result of sediment movement due to Hurri- cane Donna, the hurricane of 1948, and the Great La- bor Day Hurricane in 1935, respectively. Given the established age model, the Oyster Bay core was subsampled at l-cm intervals for geochemi- cal (organic carbon, heavy metals, stable isotopes), mi- cropaleontological (ostracodes and benthic foramini- fers) and palynological characterization. These data were complemented by an analysis of historical rain- fall, gauged freshwater flow, and limited near shore salinity data (see Nelsen ef al., in press). It is important to note that geochronology-based ages have associated error estimates that increase downcore. As a result, 7!°Pb-derived core ages in the 1940s and 1920s, for example, have a range of +3 and +4 years at the core location in Oyster Bay. For more recent Excess 210Pb activity (Ln(dpm/g)) -1 0 1 2 1 o oO — Hurricane Andrew 11 721\ 5 a skis SI 5 4 = 414 © Hurricane € 4 Donna E51 rs (e) Hurricane — of 1948 1 Ee o 1} n un Hurricane of 1935 81 91 101 Text-figure 2—Excess *!°Pb profile used to establish the geochro- nology for the Oyster Bay core (from Nelsen er al., in press). years, between 1980 and 1995, sediment geochronology varies by only +1 year (Nelsen ef al., in press). ACKNOWLEDGMENTS The authors would like to thank Amel Saied and Vivian Gonzalez, from the University of Miami- RSMAS Stable Isotope Laboratory, for running the samples for isotopic analysis. Dr. Harold R. Wanless, chairman of the University of Miami’s Dept. of Ge- ology, for fieldwork logistics and expertise about sed- imentological processes in Florida Bay. Dr. John Tre- fry and W-J. Kang, from the Florida Institute of Tech- nology’s Div. of Marine and Environmental Systems, for performing the core’s geochronology. Water qual- ity data was provided by Drs. Ron Jones and Joe Boy- er of the Southeast Environmental Research Center at Florida International University with support by the South Florida Water Management District (SFWMD/ SERC #C-10244) through Everglades National Park (NPS/SERC Cooperative Agreement #5280-2-9017). The National Climate Data Center for the rainfall data and the National Oceanic and Atmospheric Adminis- tration for their financial assistance. In addition, we 136 BULLETIN 361 would like to thank Dr. Larry Peterson for reviewing the manuscript and for his helpful suggestions. METHODS MICROFAUNAL ANALYSIS Core sediment intervals were sub-sampled, wet- sieved using a 63 fm mesh, and the coarse fraction retained for microfaunal characterization. High organic content in the Oyster Bay core required the use of ashing and 30% hydrogen peroxide treatments. Sub- sample weights were used to determine total popula- tion abundances expressed as tests or valves per gram dry sediment weight. A minimum of three hundred specimens of both ostracodes and foraminifers were counted for each sample unless limited by sample size. Temporal fluctuations in microfaunal community structure were evaluated using relative and absolute abundances, and the Shannon-Weiner diversity index (SWDI). The SWDI is defined as: H = — XN, p(i) In p(i), where H is the measure of diversity, N is the number of species counted and p(i) is the proportion of the total number of individuals which belong to the i species (MacArthur, 1983). This index incorporates a measure of species evenness as well as number (communities with many species with equal-size pop- ulations have the highest index) (Patrick, 1983), mak- ing it sensitive to the presence of rare species. STABLE ISOTOPE ANALYSIS Stable isotopic analyses (6!°O and 6°C) were car- ried out on valves of the ostracode Peratocytheridea setipunctata. This species was chosen for isotopic analysis due to its ubiquitous occurrence throughout the Oyster Bay core as well as its high abundance in surface sediment samples collected from Oyster and Whitewater bays and Florida Bay. Well-preserved adult valves of P. setipunctata were isolated from the >63 wm sediment fraction prior to the ashing/H,O, treatments. Specimens were cleaned with a small paintbrush in a distilled water bath and then in an eth- anol solution to remove adhering debris. Between 6 to 8 valves of P. setipunctata were then immersed in methanol-filled “‘copper boats” and crushed to a pow- der. The carbonate samples were processed by an au- tomated device attached to a Finnigan-MAT 251 mass spectrometer. The external precision (0.02%o for 6'°C and 0.08%c for 6'8O) was calculated from replicate analyses of the RSMAS Stable Isotope Laboratory cal- cite standard. All isotopic data are reported in per mil (%o) units relative to the Pee Dee Belemnite (PDB) standard and are corrected for the usual isobaric inter- ferences. The stable isotopic composition of the sedi- ment’s organic C fraction was analyzed as well (Nel- sen et al., in press). RAINFALL AND FRESH WATER FLOW DATA Continuous monthly freshwater flow data for Shark River Slough extending from 1939 to the present were obtained from the United States Geological Survey (http://fl.water.usgs.gov/). Rainfall data were obtained from NOAA's National Climate Data Center. Contin- uous monthly data from the Everglades, Flamingo, Homestead and Tavernier stations were obtained, ex- tending from present back to 1926, 1951, 1911, and 1936, respectively (Nelsen ef a/., in press). RESULTS The three major sediment components in the Oyster Bay core are carbonates, alumino-silicates and organic matter. The average CaCO, content is 75 + 5% and is comprised mostly of benthic foraminifers, ostracodes, small mollusks and calcareous fragments. The organic C content averages 7.1 + 1.3%, while the alumino- silicate contribution is minor, averaging only 1.6 + 0.3% (Nelsen et al., in press). OSTRACODE ASSEMBLAGE The Oyster Bay core contained 43 ostracode spe- cies. The number of species in any one sample ranged from 2 to 27, with an average of 11 species per 1-cm sample. Ostracode diversity, total abundance and spe- cies evenness show large temporal fluctuations (Text- fig. 3). Significant variability in species dominance and temporal loss of numerous species towards the present time also occurred. In addition, microfaunal preser- vation is lower towards the top of the core. The Shannon-Weiner diversity index (SWDI), used here to expressed ostracode diversity, is sensitive to the presence and absence of minor species, such that larger positive values reflect greater diversity while lower numbers indicate a community dominated by fewer species. The SWDI ranged from 0.22 at a depth of 18.5 cm (~1977) to 2.51 at a depth of 59.5 cm (~1941). Ostracode abundance in the sediment core ranged from 0 to 397 valves per gram. Highest ostra- code abundance and diversity occurred in sediments deposited in the mid-1970s, and in the late-1960s and 1950s. In contrast, the bottom half of the core, record- ing deposition between the turn of the century and the late- 1940s, is characterized by a fairly diverse and sta- ble community and a relatively low ostracode abun- dance (Text-fig. 3). The lowest abundances were found in sample intervals at 90, 74 and 57 centimeters. These samples contained less than 10 ostracode valves each, mainly of Perissocytheridea brachyforma, and repre- sent the years of 1915 + 4, 1929 + 4 and 1941 + 3, according to the extended 7!°Pb-derived geochronolo- gy. The timing of two of these events temporally cor- relates with hurricanes that occurred over areas of OSTRACODE PALEOENVIRONMENTAL RECONSTRUCTION: ALVAREZ ZARIKIAN ET AL. Phase III Phase II Phase | < r¢ 4 0.5 (1995) 7 40.5 (1985) 20.5 (1975) 30.5 (1966) 40.5 (1958) 50.5 (1948) Wag Ostracodes per gram —@— Ostracode diversity (SWDI) 300 c. Ye : , © ee : , e | 200 100 lh IB wt, Se + a = in S rr) 80.5 (1923) 90.5 (1915) 100.5 (1906) Pb Geochronology Text-figure 3.—Ostracode diversity (Shannon-Weiner diversity index; left axis) and abundance (valves/g: right axis) in the Oyster Bay core. Geochronology based on 7!°Pb and '*’Cs dating techniques (cm (year)). —@— Mailzella floridana —a&— Peratocythendea setipunctata 50 4 25 * —. 40.5 vos 0.5 (1995) + 40.5 (1985) 20.5 (1975) 30.5 (1966) 50.5 (1948) 60.5 (1940) 70.5 (1932) 8 80.5 (1923) 90.5 (1915) 100.5 (1906) —m- P. brachyforma Text-figure 4.—Relative abundances of: a) Malzella floridana; b) Peratocytheridea setipunctata, and c) Perissocytheridea brachyfor- ma in the Oyster Bay core. X-axis: *!°Pb geochronology (cm (year)). Florida Bay: the Hurricane of 1929, and the Great La- bor Day Hurricane of 1935. From 1956 + 2 to 1977 + 1, the ostracode assem- blage at this location exhibited high abundance and species diversity indicating a stable and robust ostra- code community. Population evenness was relatively high and constant at this time. Following this long, stable interval, in about 1978 + 1, a dramatic decline in assemblage diversity occurred (Text-fig. 3). The SWDI was reduced by half (from ~2 to ~1) and os- tracode abundance dramatically declined from more than 300 ostracodes per gram to less than 50. This marked the second long-term decline in ostracode community structure during the 20th century. The number of species dropped from an average of 18 spe- cies per sample to less than five and the ostracode assemblage became dominated by Peratocytheridea setipunctata (Text-fig. 4b). However, despite its high relative abundance, P. setipunctata displays low ab- solute abundance which suggests survivor type domi- nance rather than opportunistic behavior. SWDI and evenness increase slightly at the top of the core, al- though, ostracode abundance remains low. The most common ostracode species in the core were Peratocytheridea setipunctata, Malzella flori- dana, Neocaudites triplistriatus and Perissocytheridea brachyforma with maximum absolute abundances of 113, 80, 71 and 22 valves per gram, respectively. Ac- tinocythereis subquadrata, Loxoconcha matagordensis and Xestoleberis mixohalina were also common throughout the core, but their relative abundances nev- er exceed 15% of the total assemblage at any particular 138 BULLETIN 361 x Neocaudites tnplistratus 18 @ Actinocythereis subquadrata 0.5 (1995) 10.5 (1985) 20.5 (1975) 30.5 (1966) 40.5 (1958) 50.5 (1948) 60.5 (1940) 70.5 (1932) 80.5 (1923) 90.5 (1915) o 3 o) o r=) 5S @ Loxoconcha matagordensis Text-figure 5—Relative abundances of a) Neocaudites triplistria- tus, b) Actinocythereis subquadrata; and c) epiphytic ostracode spe- cies Loxoconcha matagordensis in the Oyster Bay core. X-axis: !0Pb geochronology (cm (year)) sediment interval. Inter-specific dominance among P. setipunctata, M. floridana, N. triplistriatus and P. bra- chyforma has changed through time (Text-fig. 4a,b,c; and Text-fig. 5a). The ostracode Peratocytheridea se- tipunctata showed a marked increase in relative abun- dance in about the late 1970s and remained the dom- inant species (>50%) well into the mid-1990s. In con- trast, the relative abundance of Malzella floridana re- mains rather constant throughout the core, exhibiting a peak in abundance in the mid-1940s, and a decline during the 1980s. Although P. setipunctata and M. floridana are the two most common species in the Oyster Bay core, their relative abundance appears to be inversely correlated (r: —0.72). In the other hand, the mesohaline species Perisso- cytheridea brachyforma is found sporadically in the lower portion of the Oyster Bay core in abundances of up to 50%. This corresponds to the time before 1950. Since then, abundance of P. brachyforma re- —@— Oligo-to-mesohaline ostracodes aioe ‘ rr nee aoe *!°b Geochronology 10.5 (1985) 20.5 (1975) 30.5 (1966) 40.5 (1958) 50.5 (1948) 60.5 (1940) 70.5 (1932) 80.5 (1923) 2 x D 2) wo (=) 90.5 (1915) 100.5 (1906) —#— Bairdia sp. —g-— Cytherella sp. Text-figure 6—Relative abundance of: a) Grouped oligohaline and B-mesohaline species: Candona sp., Cypridopsis okeechobei, Cytheridella illosvayi, Darwinula stephensoni, Limnocythere flori- densis and Phisocypria sp. A; and b) Euhaline species: Bairdia sp. and Cytherella sp. in the Oyster Bay core. X-axis: ?!°Pb geochro- nology (cm (year)) mained generally low until the early 1990s when its relative abundance increased again reaching 25% of the total ostracod assemblage. On the contrary, Neo- caudites triplistriatus exhibited its greatest abundance just before P. brachyforma in the early 1910s (>40%), and at about 1960 (~50%). Although present to some extent throughout the core, N. triplistriatus has been essentially absent from the Oyster Bay core since early in the 1980s (Text-fig. 5a). A group of oligo-mesohaline species, such as, Can- dona sp, Cypridopsis ockeechobei, Cytheridella illos- vayl, Darwinula stephensoni, Dolerocypria fastigata, Limnocythere floridensis and Physocypria sp. occurred at sporadic intervals in the sediment core correspond- ing to the mid-1910s, early 1930s, early 1960s, early 1980s, and in the early-1990s (Text-fig. 6a). Cypri- dopsis ockeechobei, Cytheridella illosvayi and Dar- winula stephensoni are the most common species of this group, reaching in some intervals over 7% of the total ostracode assemblage. In contrast, euhaline species such as Bairdia sp. and Cytherella sp. are only present in the Oyster Bay core at lower percentages (<4%). Although less significant in number, their distribution is clearly limited to the period of highest diversity and population abundance that occurred between the early 1950s and late 1970s OSTRACODE PALEOENVIRONMENTAL RECONSTRUCTION: ALVAREZ ZARIKIAN ET AL. 139 4 9 7 5 Ol(1995) cia > 7 9.5 (1986) 4 %e 19.5 (1976) 4 4° NY 2? 28.5(1968)} © e eee A 48.5(1950)} 4% , 58.5 (1942) 4 68.5 (1934) °® 78.5 (1925 ¢ (1925)7 6% 4 88.5 (1916) 7 @ e 98.5 (1908) % Bjejoundijas eapuayjAIO}e18q JO D.,2 } ejejOUuNdHas eapLEyjAIOJe/Ad JOO, 2 @ Ado[OUoIYyIOAH qdO [TZ wo 7 5 3 4 Text-figure 7.—Staple isotopic composition (8'°O and 6'°C) of the ostracode species Peratocytheridea setipunctata in the Oyster Bay core. (Text-fig. 6b). A gap in the occurrence of euhaline spe- cies 1s visible around 1960. The 6!°O isotopic composition of the ostracode Per- atocytheridea setipunctata ranged from —2.80 to +2.37%c. Strong negative excursions are found prior to 1925 + 4, while the most positive values occurred during the 1980s (Text-fig. 7). Between the early 1950s and 1970s, the 'SO values do not show large deviations. During this time, values oscillate between —1 and +1%c on time scales of | to 3 years. The 5'°C of Peratocytheridea setipunctata at Oyster Bay exhibits very negative values, ranging from —7.59 to —10.72. Relatively constant and lighter values (ap- proximately —10%c) occur between early 1900s and late 1950s. Isotopic trends during this time are gradual, trending to more positive or negative values in roughly decadal timescales. In contrast, abrupt positive shifts in the 5%C record take place at about 1970 + 1| and 1983 + 1. The 56°C of P. setipunctata at these times is enriched by more than 2%c. An increase in the mag- nitude of fluctuations of the 6'°C is evident upcore. DISCUSSION MICROFAUNAL RESPONSE Large decreases in ostracode abundance and diversity and shifts in species dominance that occurred in the Oys- ter Bay core represent episodes of environmental stress due to natural and/or anthropogenic forces. Distinctive characteristics of the ostracode assemblages from the core locality were used to divide the 100-year ostracode record into three zones. The first zone extends from the turn of the century to about 1950; the second, from the early 1950s to the late 1970s; and the third to the time of core recovery in 1995. Before 1950, the significant declines in ostracode community structure that occurred in 1915 + 4, 1929 + 4, 1941 + 3 and 1948 + 2 are temporally coincident with severe tropical storms or hur- ricanes: the tropical storm of 1916, the hurricane of 1929, the Great Labor Day hurricane in 1935, and the hurricane of 1948. Hurricanes are capable of causing im- mediate or long-term environmental changes in coastal areas due to sediment erosion and deposition, and storm induced bi-directional sediment transport (Tabb and Jones, 1962; Smith eft al., 1994; Wanless er al., 1994). Decline in the ostracode populations and the input of reworked freshwater species as seen in the Oyster Bay core are evidence of hurricane disturbance. However, ac- cording to our data, reasonably rapid population recov- eries from these events indicate a relatively resilient com- munity. The first zone culminated with a decade-long diversity low, and an ostracode assemblage dominated initially by Malzella floridana and later by Peratocy- theridea setipunctata. Rainfall data from the Homestead station (Nelsen ef al., in press) showed lower than av- erage rainfall during the early 1940s, with a later increase in rainfall from the mid to late 1940s (Text-fig. 8). In contrast, freshwater flow data for Shark River Slough during that time shows a diminished flow during most of the 1940s (Nelsen ef al, in press). The Homestead rainfall data are used as a comparison in this case be- cause the record is longer (back to 1911) than that of the Flamingo meteorological station, whose data only extend from 1951 to the present. The second zone, between the late 1950s and late 1970s, exhibited the richest ostracode fauna (average: >200 valves/g) and the highest diversity (SWDI >2). Community fluctuations during this interval are more gradual and can be temporally correlated to SFWMD policies. The second zone generally represents a “bloom” period interrupted only by a brief hiatus in 140 250 200 - rainfall (cm/yr) 100 - 50 1997 1992 1987 1982 1977 1972 1967 1962 1957 BULLETIN 361 1952 1947 1942 1937 1932 1927 1922 1917 1912 == Hmstd (trend) -e- Homestead —«— Flamingo Text-figure 8.—Rainfall record during the 20th century from the Flamingo and Homestead meteorological stations (NOAA's National Climate Data Center). Gray area: trend analysis for Homestead rainfall station (right axis). the ostracode assemblage continuity about 1960, co- incident with Hurricane Donna. During this period ma- jor construction also occurred (1960—63) with vast ar- eas of the Everglades north of Tamiami Trail delimited with new levees and canals. Water flow into the Shark River Slough (SRS) at this time, began to be controlled by a series of gate spillways in order to create the current system of Water Conservation areas (Light and Dinnen, 1994). In addition, higher concentrations of organic carbon in the sediment intervals of this period, and at about 1935 (Nelsen er al., in press), support the hypothesis of hurricane effects. Large amounts of or- ganics derived from sediment transport and subsequent settling of suspended material occurred at this time. Oxidation of high concentrations of organic material at the sediment/water interface may have reduced ox- gen levels, temporarily inhibiting occupation by most of the benthic microfaunal assemblage. During the late 1950s through late 1970s, small num- bers of the euhaline ostracodes Bairdia sp. and Cyther- ella sp. also appeared (up to 4%, see Text-fig. 6b). Typ- ical marine species were not present in relative abun- dances greater than 0.3% anywhere in the core until this time. Two reasons potentially explain the appear- ance of euhaline taxa at the core locality. First, hurri- cane-related onshore sediment transport due to the Hur- ricane of 1948 and Hurricane Donna (1960). Second, less than average rainfall in the area during the 1950s may have favored marine water input from the Gulf of Mexico, allowing shelf taxa to adapt to the otherwise brackish waters of Oyster and Whitewater bays. Be- tween the 1960s and early 80s, the SFWMD imple- mented a series of short-term water management plans (1963-70), and more importantly the congressionally mandated Monthly Minimum Allocation Plan of water supply to SRS (Light and Dineen, 1994). The latter practice resulted in essentially, no correlation between rainfall and flow (r = —0.06) (Nelsen ef al., in press). The time interval encompassed in zone 2 was also tem- porally coincident with the opening and closing of the Buttonwood Canal (late-1950s and late-1970s). The Buttonwood Canal may have led to improved water ex- change between Florida Bay, Whitewater Bay and the Gulf of Mexico by means of tidal water movements, ultimately improving water quality in Whitewater Bay. The second ostracode zone ended circa 1979, when an abrupt decline in population diversity and abundance occurred, from which the ostracode assemblage had not yet fully recovered as of 1995. The third zone extends from about 1979 until 1995 when the sediment core was taken. It is highlighted by a large decline in ostracode diversity and abundance at about 1980 and the survivor-mode dominance ex- hibited by Peratocytheridea setipunctata, one of the two most common species in the core, known to be tolerant to extreme salinity fluctuations (<5 to 42) (Keyser, 1977; pers. comm., 1999). The early 1980s marked the end of the SFWMD’s Monthly Minimum Water Delivery Plan, which was replaced by a regu- lated flow plan believed to be more natural, known as the Rainfall Plan. In addition, a great part of the nat- ural flow of freshwater running through Shark River Slough was deviated into the drainage basin of Taylor Slough. This cutback in freshwater renovation is likely to have induced strong evaporative conditions in Oys- ter Bay at this time. Natural climatic variability (the mid-1980s drought in South Florida) appears to have further impacted environmental conditions and prob- OSTRACODE PALEOENVIRONMENTAL RECONSTRUCTION: ALVAREZ ZARIKIAN ET AL. 141 ably outweigh the impact of anthropogenic forces in this time period. Extracting information embedded in the ostracode record to assess and isolate the effects of water management practices may then, not be easy in this case. The modest presence of the oligohaline species Cypridopsis vidua, Cytheridella illosvayi, Dar- winula stephensoni (7, 3 and 7% respectively) in the early 1980s is considered the result of sediment transport. INTERPRETATION OF STABLE ISOTOPIC COMPOSITION Stable isotopic analysis of coastal ostracodes is not routine and it is fraught with many complexities as such studies are still in an early stage. Freshwater and deep sea ostracodes are comparatively simpler than in coastal taxa because variations in salinity and temper- ature in those environments are relatively small and require the understanding of control by only a few parameters (7.e., ice volume). Coastal species are con- trolled by many other environmental parameters (i.e., rainfall, evaporation) that have the potential to change dramatically in a seasonal basis. Therefore, the under- standing of the interaction between these processes and the isotopic composition of ostracode valves is not straightforward, but we will attempt to demonstrate the feasibility of such studies in paleoenvironmental re- construction of coastal ecosystems. The ubiquitous occurrence of Peratocytheridea se- tipunctata made this species ideal for an evaluation of the utility of stable isotopic analysis as a paleoenvi- ronmental tool. The stable isotopic composition (6!°O and 6"%C) of ostracodes principally responds to two factors: water chemistry and temperature (Chivas er al., 1986). Differences in the physiology of organisms give rise to the so-called vital effects (von Grafenstein et al., 1999). This means that different species inhab- iting the same environment have similar responses to environmental factors, but can be offset from one an- other. Vital effects can explain when an organism ap- pears to be out of equilibrium from the predicted values. Important to this study is the understanding of the environmental factors that control 6!*O and 6'C in- corporation in ostracode valves. These are primarily water chemistry and in the case of 5!8O, temperature, rainfall and evaporation (Swart er al., 1996). Strong excursions to more negative values of 5'8O of Pera- tocytheridea setipunctata that take place prior to 1925 + 4 correlate to high-rainfall years, and are consistent with relatively fresher conditions or rather constant brackish water conditions in a typical estuary. In con- trast, strong positive excursions to heavier 5!*O values occurred during the mid-1980s. As evaporation pro- ceeds, it preferentially removes '°O and leaves the wa- ter behind enriched in '%O; thus, the 6!°O value of the water becomes more positive. This may have been the case for the mid-1980s when heavier oxygen isotopic values were concurrent with a major regional drought in South Florida, as well as with algal blooms and a major die-off of sea grasses (Swart er al., 1999). Evap- oration of marine or brackish waters will result in a correlation between salinity and 6!°O, whereas evap- oration of freshwater produces no such correlation. Some of the intricacies this difference causes in inter- pretation of 'SO results in the Everglades/Florida Bay system are as follows. Commonly marine waters have 6'8O values between O and +1%o SMOW, while freshwater values are more negative. In South Florida, the 6'%O of rainfall is ap- proximately —3%c (Swart ef al., 1989). During drier years, when precipitation is appreciably lower than the annual mean of 150 cm, the intense evaporation in the Everglades can cause freshwater to have a 5!*O value as high as +3%o (in contrast to the marine signal of 0 to + 1%c). Reduction in freshwater flow may also allow a greater intrusion of marine water resulting in an in- crease of isotopic composition as well. However, in this instance the 6'°O will increase because of the movement of the salt water/freshwater transition in- land and not because of the enhanced evaporation. Both cases will result in a negative correlation between salinity and 6'8O. In wet years, the Everglades water is closer in isotopic composition to the original rainfall value (~—3%c). Finally, during very wet periods, the freshwater will retain its original negative 6'8O value and when mixing with marine water it will produce a positive covariance between oxygen and salinity (Nel- sen et al., in press). In coastal waters, the 61°C is also highly variable and the dissolved inorganic carbon (DIC) will be high- ly depleted as a result. The carbon isotopic composi- tion of calcareous organisms can be principally related to the 8'°C of the DIC pool as well as the physiological state of the organism. Under normal marine condi- tions, physiological processes are probably most im- portant in controlling interannual variations in the 6%C of the calcitic skeleton. In situations such as Oyster Bay, variations in the DIC probably dominate. Varia- tions in the 6%C of the DIC are caused by a combi- nation of the oxidation of organic material, which pro- duces water highly depleted in 5'°C, and the introduc- tion of marine waters, which are relatively enriched in 54C (Nelsen et al., in press). During the wet season, Oyster Bay will be inundated by freshwater that will be isotopically depleted in 6'°O and 6/3C. In contrast, during the dry season, the area will be influenced more by marine water from the Gulf, which will be heavier in 6!8O and 6'°C. Generally, the ostracode isotopic data from Oyster Bay shows positive correlations between 5C and '8O suggesting a normal interaction between 142 BULLETIN 361 freshwater and marine waters (Text-fig. 7). Positively correlated 5'°O and 6'°C deviations suggest an asso- ciation between terrestrially derived, isotopically light, C and O. Exceptions to the positive correlation between the 6'8O and 6'C in the ostracode data occur in the 1970s, and the 1930s and 1940s. The offset in the 1970s is significant because it occurs immediately prior to a substantial shift towards more positive oxygen and carbon isotopic compositions that are evident in the ostracode isotopic record. At this time, flow in the Shark River Slough and the rainfall record at Home- stead and Flamingo are decoupled (Nelsen ef al., in press), suggesting a major modification in water flow prior to this time period. The other periods (1930s and 1940s), which exhibit a negative correlation between dC and 6'8O, are more difficult to understand because of an absence of hydrological data and the lower abun- dance of ostracodes. CONCLUSIONS The following conclusions can be derived from the ostracode fauna and isotopic data. Natural variability in the ostracode communities over time is the result of natural seasonal fluctuations in climate and hydrolog- ical conditions. Hurricane events and their effects are the major cause for immediate modifications within ostracode populations. However, these populations are capable of a rapid recovery. Rainfall is the dominant natural driving force behind long-term variability in microfaunal assemblages. The Oyster Bay core showed a large decline in os- tracode diversity and abundance at about 1980. The timing of this event is best correlated to the onset of the SFWMD “Rainfall Plan” and the modification of the natural flow of freshwater running through Shark River Slough to the drainage basin of Taylor Slough. This cutback in freshwater renovation to Oyster Bay is likely to have induced strong evaporative conditions. In addition, the closing of the Buttonwood canal, also at this time, may have reduced water exchange be- tween Whitewater Bay and Florida Bay, and further stressing Oyster Bay’s microfaunal communities. Strong positive deviations in 6'C and 6!*O for both species, Peratocytheridea setipunctata and Ammonia parkinsoniana in the mid 1980s were concurrent with a documented major regional drought in South Florida, as well as with algal blooms and a major die-off of sea grasses in Florida Bay (Fourqurean and Robblee, 1999; Robblee er al., 1991). In general, the isotopic data from Oyster Bay shows positive correlations between '%C and '8O for both P. setipunctata and A. parkinsoniana suggesting a normal interaction between freshwater and marine waters. An exception that occurred in the 1970s is probably the result of decoupling of rainfall and freshwater flow down Shark River Slough during this time period due to changes in water management. REFERENCES CITED Alvarez Zarikian, C.A., Hood, T., Blackwelder, P.L., Swart, P.K., Nelsen, T.A., Wanless, H.R., Trefry, H.J., and Kang, W-J. 1999a. 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Effect of Hurricane Donna on the aquatic fauna of North Florida Bay. Transactions of the American Fisheries So- ciety, vol. 9, p. 375. Turpen, J. B., and Angell, R.W. 1971. Aspects of molting and calcification in the ostracod Het- erocypris. Biological Bulletin, vol. 140, pp. 331—338. Von Grafenstein, U., Erlernkeuser, H., and Trimborn, P. 1999. Oxygen and carbon isotopes in modern fresh-water ostra- code valves: assessing vital effects and autecological ef- fects of interest for paleoclimate studies. Palaeogeogra- phy, Palaeoclimatology, Palaeoecology, vol. 148, pp. 133-152. Wanless, H.R., and Tagett, M.G. 1989. Origin, growth and evolution of carbonate mudbanks in Florida Bay. Bulletin of Marine Science, vol. 44, p. 454. Wanless, H.R., Parkinson, R.W., and Tedesco, L.P. 1994. Sea level control on stability of Everglades wetlands, in Davis, S.M., and Ogden, J.C. eds., Everglades: The Eco- system and its Restoration. St. Lucie Press, Delray Beach, Florida, pp. 199-223. we ie it Ww af? i ms af é wt yoy 7 yy » a) & i hee ‘ ° a 13 ini tel a in) 7 5 7 “ U . ha" oh nah eh ae ae s\ Se. ot co ay one ; — \b uh wey - 198 7 awe a i, d ie Saas | nae: 2 Va Wi Wiel”? is n qe é Pcotm 7 ” ~ oe | | mee ; a any S Co Der: » 7 _ i be : — Od, sy te : ~ ete eres | ree ae) ms _ ap ta Peel Ti mh : ‘a) previ 7 py wh l= j vad tee wr: 7 sie sv : i ea Ti) Y, si) oe en re oat Oona = Ohi tnt a Set aa<- fiat @ 5 Psy =e “aut Acer —_ : Aw = 4 =i) » aw '\ | ae? AR swe | Py Cee este 7 9a = ae, ) re py Se =~ ke ee a f a "ii ican -_— reat a tera ' ies 0 oer 2 y a - ~~ CHAPTER 8 DIATOMS AS INDICATORS OF ENVIRONMENTAL CHANGE IN SEDIMENT CORES FROM NORTHEASTERN FLORIDA BAY J. K. HUVANE AND S. R. COOPER Duke University Wetland Center Nicholas School of the Environment Durham, NC 27708 ABSTRACT Diatom assemblages found in two sediment cores from northeastern Florida Bay indicate fluctuations in both salinity and extent of sub-aquatic vegetation cover during the past 100 years. Diatoms from Russell Bank core 19A indicate that salinity was high prior to the 20th century. Between 1890 and 1920, assemblages dominated by Mastogloia species prevail. After 1920, there is a dramatic shift to assemblages dominated by an epipelic taxon, Nitzschia granulata. Around 1950, this taxon declines in abundance and epiphytic species increase. Epiphytic species remain common until about 1972. After 1972, epiphytic diatoms decrease in abundance, and diatoms indicative of higher salinity increase. Similar trends are seen in the Pass Key core 37 (which only spans about 35 years, between 1960-1996). Epiphytic diatoms are common between about 1967 and 1977, and there is an overall trend towards increasing salinity upcore. These findings are in general agreement with other studies of fossil indicators related to salinity and seagrass cover found in Florida Bay sediment cores. These fluctuations may be related to anthropogenic activities, such as the reduction of freshwater flow to Florida Bay from the Everglades as a result of water management practices. INTRODUCTION In the past decade, the ecological health of South Florida has been questioned, particularly that of the Everglades and Florida Bay (e.g., Davis and Ogden, 1994; McPherson and Halley, 1996). For instance, re- cent seagrass die-offs, algal blooms and periods of hy- persalinity have generated interest in the extent of an- thropogenic impacts on Florida Bay. The advent of ecological studies and monitoring programs in Nation- al Parks has allowed managers to move from a belief- based management system to science-based ecosystem management (Davis and Halvorsen, 1996). For ex- ample, the Everglades Forever Act was passed in 1994, which mandates that the ecosystem be returned to its “natural state”. One of the pivotal issues that arise from this mandate is how this “natural state” should be defined. Commonly, the goal is to restore the environment to conditions that existed prior to ma- jor European anthropogenic disturbance, such as ur- banization (e.g., Holling et al., 1994; MacMahon, 1998). In the absence of historical monitoring data that defines the natural variation of the ecosystem, resto- ration management decisions are exceedingly difficult. Paleoecological applications, which allow for the re- construction of past environments, provide proxy data to managers interested in restoration (e.g., Brewster- Wingard et al., 1998). Paleoecological techniques have been used successfully to help solve environmental problems such as lake acidification (e.g., Battarbee et al., 1999) and eutrophication (e.g., Hall and Smol, 1999). More recently, paleoecological techniques have been applied to estuarine systems (e.g., Juggins, 1992; Cooper, 1995a; Brewster-Wingard et al., 1998a; Ish- man et al., 1998; Cooper, 1999). This study deals with the use of diatoms as indica- tors of environmental change in Florida Bay sediment cores. Diatoms are microscopic algae that commonly occur in aquatic environments. They have a siliceous shell, or frustule, that is generally well preserved in aquatic sedimentary environments. Species designa- tions are based on the morphology of their silica shell, making them particularly attractive as fossil indicators. In addition, species distributions are closely linked to water quality parameters such as pH, salinity, and nu- trient availability (e.g., Sweets et al., 1990; Fritz et al., 1991; Dixit et al., 1993; Fritz et al., 1993; Wilson et al., 1994; Cooper et al., 1999). We present diatom assemblage data from sediment cores from two sites in northeastern Florida Bay. The main objective of the study is to provide a diatom- based reconstruction of environmental conditions in this sub-region of Florida Bay during the last century. We examine past changes in salinity and sub-aquatic vegetation cover. ACKNOWLEDGMENTS Funding for this study was provided by the U.S. Geological Survey South Florida Ecosystem Program. The Duke University Wetland Center, Nicholas School 146 BULLETIN 361 | ADES NATIONAL’ | J PARK— —/ Text-figure 1—A map of Florida Bay with the 26 USGS monitoring sites labeled. The Russell Bank and the Pass Key sites are indicated by the “xX.” of the Environment, provided additional support. We thank Laura Pyle for performing the diatom counts for Pass Key core 37. We would also like to thank G. Lynn Brewster-Wingard of the U. S. Geological Sur- vey, Reston, VA, who provided sediment samples for diatom analyses. The Keys Marine Lab, Florida Insti- tute of Oceanography, Long Key, Florida provided field assistance. METHODS CORE COLLECTION AND CHRONOLOGY Sediment cores were collected from two sites: Rus- sell Bank and Pass Key (Text-fig. 1). Russell Bank sediment cores were collected in February 1995 by the U.S. Geological Survey (St. Petersburg, FL) in co- operation with the South Florida Water Management District and the Everglades National Park (Brewster- Wingard ef al., 1997). Cores were collected from the south side of Russell Bank (N 25° 03’ 50.04”, W 80° 37’ 29.28") from a seagrass bed, at a water depth of one half meter. Russell Bank core 19A (RB 19A) was taken alongside Russell Bank core 19B (RB 19B), and the two are considered replicate cores. A third core, Russell Bank 19C (RB 19C) was taken 54 m north of cores 19A and 19B. Cores were dated using 7!°Pb ra- diometric-dating techniques. At present, only cores RB 19B and RB 19C have been analyzed for 7!°Pb activity (Brewster- Wingard et al., 1997). Samples from core RB 19A were used for diatom analyses. Core RB 19A was 140 cm in length and subsamples were taken at | cm intervals between O— 30 cm and at 2 cm intervals between 30—140 cm. Se- lect samples were analyzed for diatoms. Pass Key core 37 (PK 37) was collected by the U. S. Geological Survey (St. Petersburg, FL) in May 1996. The core was taken at N 25° 08’52.08” W 80° 34'28.20". This core was 76 cm in length and was subsampled at 2 cm intervals. Core chronology was established by *!°Pb radiometric-dating techniques. De- tails of the dating methods can be found in Robbins et al. (in press). DIATOM EXTRACTIONS A modified version of the procedure described by Funkhauser and Evitt (1959) was used to extract dia- toms from sediment core samples. Approximately 0.5 mg dry weight sediment was digested for each sample from core RB 19A. For core PK 37, the amount of sediment digested varied between approximately 0.7 and 2.4 mg dry weight per sample. Samples were treat- ed with H,O,, followed by HCl, and finally an HNO, and K,Cr,O, digestion. Sand particles were removed by a coarse fractionation procedure. Measured aliquots of the final diatom slurries were permanently mounted in Naphrax® (Northern Biolog- ical Supply, Ipswich, UK) (Refractive Index = 1.7) on microscope slides. Slides were examined with a light microscope at a magnification of 1000X. Light micro- scope digital images of most diatom taxa were cap- tured via CCD video camera and frame grabber. These images are on file at the Duke University Wetland Center. DIATOMS AND ENVIRONMENTAL CHANGE: HUVANE AND COOPER 147 DIATOM IDENTIFICATIONS Taxonomic identifications were aided by a number of resources including Peragallo and Peragallo (1897— 1908); Hustedt (1927-1964, 1955); Patrick and Rei- mer (1966); DeFelice (1976); Stephens and Gibson (1979, 1980a, 1980b); Yohn and Gibson (1982a, 1982b); Foged (1986); Navarro (1982a, 1982b); Kram- mer and Lange-Bertalot (1986, 1988, 1991a,b); and Cooper (1995b). However, there are diatom taxa that have yet to be identified to species level. Some of these taxa may not be described in the literature. These taxa were identi- fied to the generic level and given a species letter des- ignation, e.g., sp. A. For core PK 37, 15 samples were analyzed and be- tween 300-500 diatom valves were enumerated and identified from each sample. For core RB 19A, 31 samples were analyzed and approximately 400 diatom valves were enumerated and identified from each sam- ple. DATA ANALYSIS Down-core changes in diatom assemblages were ini- tially analyzed by examining changes in the relative abundance of dominant taxa. Shannon-Wiener diver- sity, (~~ pn p;, where p; = the proportion of the total number of valves belonging to the ith taxa in the as- semblage) was calculated for each sample following Wetzel, 1983. Centric: Pennate (C:P) ratios were cal- culated for each sample. Centric and pennate are tax- onomic terms related to diatom valve (shell) symme- try. In these particular Florida Bay samples, the centric diatoms are primarily planktonic and the pennate dia- toms are benthic and epiphytic. The C:P ratio provides a simple index of the relative abundance of planktonic versus benthic and epiphytic diatoms in these samples. A multivariate ordination technique, detrended cor- respondence analysis (DCA), was used to analyze the species assemblage data. Detrended correspondence analysis is an indirect ordination analysis that arranges sites along axes based on species composition (ter Braak, 1995). Ordination analyses indicate which sites are similar in species composition. The ordination analyses were based on the percent abundances of the most common diatom taxa in each core. These anal- yses were done separately for each core. For core PK 37, a total of 43 taxa were included in the analysis. Each of these 43 taxa comprised at least 1% of the total diatom count in at least two samples. Similarly, for core RB 19A, 36 taxa that comprised at least 1% of the diatom assemblage in two or more samples were used. The gradient length for the Pass Key dataset was relatively short (<2.0 standard deviation units). There- fore, a linear ordination technique, principal compo- nents analysis (PCA) was used instead of the unimodal DCA in the final analysis of the Pass Key data (ter Braak, 1995). A stratigraphically constrained cluster analysis, CONISS (Grimm, 1987), was performed on the same data sets for both cores (PK 37 and RB 19A). This is a program that performs cluster analysis by incremen- tal sums of squares, with the constraint that only ad- jacent core samples can be merged. Diatom species distributions are displayed as a ratio to the individual species maximum in the core sam- ples. For example, if the maximum abundance of a given species were 30%, then a particular sample with a percent abundance (for that species) close to 30% would have a ratio close to 1. This form of display allows one to easily examine relative changes in the abundance of the less common species. Some of these less common species are indicative of certain environ- ments, and thus changes in their abundance provide information concerning past environmental conditions. RESULTS CORE CHRONOLOGIES The *!°Pb activity curves for cores RB 19A and RB 19C were very similar. Sedimentation rates for these two cores were estimated at 1.22 cm/yr + 0.05 cm (Brewster-Wingard et al., 1997). Given this sedimen- tation rate, core RB 19A is approximately 115 years old, spanning the period from about A.D. 1880 to 1995; The sedimentation rate for core PK 37 was esti- mated to be on the order of 2.06 cm/yr + 0.2. Evi- dence from other sources supports this estimation. Ae- rial photo evidence indicates that the opening south of Pass Key has been filling in since the 1950’s (Brew- ster-Wingard ef al., 1998b). In addition, Casuarina pollen is present throughout the core indicating rela- tively recent deposition (less than 100 years) because this species was not introduced to the region until the late 1800’s or early 1900’s and would therefore not be present at an earlier date. (Brewster-Wingard ef al., 1998b). Russell Bank Core 19A Diatom Flora A total of 157 diatom taxa have been identified from core RB 19A. The five most abundant taxa in the core samples examined are Cyclotella cf. litoralis Lange and Syversten, Nitzschia granulata Grunow, Cyclotel- la cf. striata (Kutz.) Grunow, Grammatophora cf. oceanica var. macilenta (Wm. Smith) Grunow, and Sy- nedra sp. A. Representative images of these taxa are BULLETIN 361 148 “ DIATOMS AND ENVIRONMENTAL CHANGE: HUVANE AND COOPER 149 max. = 71.8% Nitzchia granulata max. = 12.8% Depth (cm) Cocconeis cf. placentula var. euglypta max. = 7.3% 100 125 150 Mastogloia crucicula max. = 61.2% max. = 10.3% Synedra sp. A max. = 2.9% Mastogloia corsicana 1995 1970 1945 1920 max. = 15.5% Grammatophora cf. oceanica var. macilenta 1895 1870 1995 1970 max. = 11.9% | 1945 Date 1920 aes 1895 Mastogloia sp. A 1870 1995 1970 1945 max. = 2.8% 1920 1895 Mastogloia ovalis 1870 OOM O:2 10406) 0:8) 1101010" 0:2" 0:4 O16 0/8" 1.0. 010 0:2 0:4 016 0:8 1.0 Proportion Text-figure 3.—Relative abundances of select taxa from the Russell Bank core 19A. Relative abundances are standardized to the maximum abundance for each species. Values of 1 indicate a maximum abundance for that species. Samples are plotted by sample depth in centimeters. Dates (based on the average sedimentation rate derived from Pb-210 analyses) are shown on the right. shown in Text-figure 2. The percent abundance of these species standardized to the maximum abundance of each species are shown in Text-figure 3. The two species of Cyclotella are grouped together in the Cy- clotella graph (Text-fig. 3) because these species were sometimes difficult to distinguish. The maximum — abundance (71.8%) of Cyclotella species occurs in the lower part of the core at the 88—90 cm sample interval. A second peak occurs at the top of the core, where the percent abundance reaches 60% of the total diatom count. Mastogloia species are most common in the bottom third of the core, comprising an average abun- Text-figure 2.—Light microscopic photographic images of representative diatoms from Russell Bank core 19A. a) Mastogloia corsicana b) Mastogloia crucicula c) Mastogloia sp. R d) Cocconeis placentula var. euglypta e) Mastogloia ovalis f) Mastogloia sp. A g) Nitzschia granulata h) Cyclotella cf. striata i) Synedra sp. A j) Grammatophora cf. oceanica var. macilenta k) Cyclotella cf. littoralis. 150 BULLETIN 361 dance of 24% between the 124-126 and 90-92 cm samples. The most common Mastogloia species in this portion of the core are Mastogloia sp. A and Masto- gloia sp. R. Mastogloia species decline in abundance between 80 and 56 cm, with an average abundance of only 6% over this interval (Text-fig. 3). Above the 56— 58 cm sample, Mastogloia species once again increase with an average abundance of 15%. However, the spe- cies differ from those present in the bottom third of the core. In the upper portion of the core, Mastogloia crucicula Grunow, Mastogloia corsicana Grunow, and Mastogloia ovalis A. Schmidt are among the species that increase in abundance (Text-fig. 3). Nitzschia granulata is an important component of the diatom assemblages in the middle of the core be- tween 80 and 28 cm (Text-fig. 3), with an average relative abundance of 26% over this interval, and a maximum abundance of 61% at the 70—72 cm sample. Nitzschia granulata declines above 60 cm and decreas- es to less than 2% of the assemblage in samples above 28 cm. Grammatophora ct. oceanica var. macilenta becomes more common above 80 cm, with an average abundance increasing from 1.5% (below 80 cm) to 9% (above 80 cm), although abundances decline near the top of the core. Cocconeis placentula var. euglypta (Ehr.) Cleve is most abundant in the 50—52 cm sample, with a maximum abundance of over 12% (Text-fig. 3). The relative abundance of this species is fairly high until about 28 cm. Synedra sp. A occurs throughout the core, but percentages of this taxon increase above 30 cm, with a maximum abundance of 10.3% in the 20—21 cm sample (Text-fig. 3). Detrended Correspondence and Cluster Analyses In the DCA diagram, samples with similar diatom assemblages have similar axis | and 2 scores and are, therefore, closer together on the plot (Text-fig. 4). Ar- rows drawn between samples (from the bottom to the top of the core) show how the diatom assemblages have changed over the time period represented by the core. Several groups of samples emerge from this anal- ysis. These are the bottom-most group, between 136 and 130 cm, a second group between 130 and 90 cm, a transition group between 90 and 76 cm, a third group between 76 and 56 cm, another transition group be- tween 28 and 56 cm, and the uppermost samples be- tween 28 and 4 cm. The cluster analysis shows that the greatest change in diatom assemblages occurs between the 80-82 cm and 90—92 cm samples (Text-fig. 5). Other sub-clusters contain samples between 130 and 136 cm, 130 and 90 cm, 90 and 56 cm, 56 and 28 cm, and samples between 28 and 4 cm. These groupings indicate that the diatom flora can Russell Bank Core 19A Axis 2A =0.11 Axis 2A = 0.36 Text-figure 4.—Detrended correspondence analysis ordination plot based on the diatom assemblages in Russell Bank core 19A. The numbers on the figure indicate sample numbers (the top depth). Circles are drawn around the samples from each zone. Arrows are drawn sequentially from zone I to zone V and indicate how diatom assemblages have changed during the last century. Diatom zones are indicated by the following symbols: Zone I (136-130 cm; 1882— 1886 A.D.): filled circles. Zone I (130-90 cm; 1882-1921 A.D.) filled squares. Zone HI (90—56 cm; 1921—1949 A.D.) filled diamond. Zone IV (56—28 cm, 1949-1972 A.D.) open squares. Zone V (28— 4 cm; 1972-1992 A.D.) stars. be separated into five time zones represented by depth intervals in the core. The average sedimentation rate of 1.22 cm/yr was used to calculate approximate time intervals: Zone I ca. A.D. 1882—1886 (136-130 cm), zone II ca. A.D. 1886-1921 (130—90 cm), zone III ca. A.D. 1921-1949 (90-56 cm), zone IV ca. A.D. 1949— 1972 (56-28 cm), and zone V ca. A.D. 1972-1992 (28—4 cm). Zone I is characterized by higher percentages of Cy- clotella, and generally poorer valve preservation than the rest of the core. Zone II is best characterized by high percentages of Mastogloia species. Zone III shows a major shift to diatom assemblages dominated by Nitzschia granulata. Grammatophora cf. oceanica var. macilenta also increases during this zone. Zone IV has high percentages of N. granulata, as well as higher relative abundances of Mastogloia crucicula, M. cor- sicana, M. ovalis, and Cocconeis placentula var. eu- glypta. A decrease in N. granulata and increases in Synedra sp. A and Cyclotella species characterize zone V. According to the DCA, zone V and zone I are sim- ilar. This reflects the high abundance of Cyclotella in these samples and the low abundance of N. granulata. Due to the poorer preservation of valves in zone I, it is not clear if the two zones represent similar diatom communities in other respects. DIATOMS AND ENVIRONMENTAL CHANGE: HUVANE AND COOPER 151 o ee Russell Bank Core 19A FS 0 ¢ CONISS 1975 25 50 1950 i © & 8 ee (7) 19257 O 1004 1900 1254 1875 150° Total sum of squares Text-figure 5.—A stratigraphically constrained cluster analysis of the Russell Bank core 19A diatom assemblages. The Y axis shows sediment depth with the top of the core at the top of the diagram. The second Y axis shows dates based on Pb-210 analyses. The samples counted along with the diatom zones are indicated on the left. Diatom Species Diversity The Shannon-Weiner index of species diversity takes into account both the number of species (species richness) in an assemblage and the number of diatom valves represented by each species. For these samples, species richness mirrors the total diversity. For 1in- stance, when most of the valves belong to one or a few species, both species diversity and species rich- ness are low. There are several shifts in diatom diver- sity in core RB 19A (Text-fig. 6). Diversity is low in the bottom-most samples, partly due to a larger num- ber of poorly preserved valves that were difficult to identify, even to the generic level. However, the Pear- son correlation coefficient for diversity and the percent 1995 1970 1945 Date 1920 Depth (cm) 1895 1870 Difference Difference Text-figure 6.—Diversity and C:P profiles for Russell Bank core 19A. Both diversity and the C:P ratio are shown as a difference from the core average. The core mean diversity = 2.30. The core mean C:P = 0.56. unidentifiable valves (typically broken, poorly pre- served valves) is very weak (1? = 0.004), suggesting that low diversity of samples is not related to poor preservation of diatom valves. Diversity is highest be- tween 90-110 cm, where diatom assemblages are characterized by an increase in Mastogloia species, yet preservation quality of the valves is similar to that of the samples in the bottom of the core. There is a very sharp decrease in diversity at 88-90 cm, a sample dominated by Cyclotella species. Diversity values re- cover and then decrease between 56 and 70 cm. This decrease reflects the dominance of Nitzschia granulata valves in these samples. Above 50 cm in the core there is an increase in diatom diversity. In general, trends in diversity correspond to the five zones determined by diatom species composition. Diversity values are be- low average during zone I (A.D. 1882-1886). During zone II (A.D. 1882-1921), values increase and then drop to below average again during zone III (A.D. 1921-1949). Values are above average during zone IV (A.D. 1949-1972) and then decline slightly during zone V (A.D. 1972-1995), but do not fall much below average until ca. A.D. 1995. Centric : Pennate Ratio The C:P ratios in Russell Bank core 19A generally reflect the abundance of planktonic Cyclotella species. For example, there is a high C:P ratio in the bottom of the core and a high abundance of Cyclotella species 152 BULLETIN 361 max. = 45.3% Cyclotella spp. Nitzschia granulata max. = 14.2% Depth (cm) Mastogloia crucicula Mastogloia erythrea Fragilaria cf. tabulata Mastogloia ovalis 00 02 04 06 08 1000 02 04 06 08 1.0 0.0 Proportion Nitzschia frustulum Mastogloia elegans 1995 1985 max. = 12.2% max. = 9.4% Cocconeis placentula var. euglypta cconeis pi ul iglyp 1956 1985 1976 Date 1966 Mastogloi icana lastogloia corsical 1956 0.0 02 04 06 O08 1.0 1995 1985 1976 1966 rammatophora cf. peaaticay var. macilenta} 4956 02 04 06 O08 1.0 Text-figure 7.—Relative abundances of select taxa from the Pass Key core 37. Relative abundances are standardized to the maximum abundance for each species. Values of 1 indicate a maximum abundance for that species. Samples are plotted by sample depth in centimeters. Dates (based on the average sedimentation rate derived from Pb-210 analyses) are shown on the right. (Text-fig 6). The sharp increase in C:P at the 88—90 cm sample interval also reflects the large amount of Cyclotella valves in this sample. Above 88 cm, the ratio declines. There is a general increase in the C:P ratio between 70 and 40 cm. The ratio declines slightly between 40 and 30 cm, and above 30 cm there is a gradual increase. Pass Key Core 37 Diatom Flora A total of 95 diatom species and varieties were iden- tified from Pass Key core 37. The five species with the highest mean percent abundances are Cyclotella cf. litoralis, Nitzschia granulata, Mastogloia crucicula, Cocconeis placentula cf. var. euglypta, and Fragilaria cf. tabulata var. tabulata (Ag.) Lange-Bertalot. Select images of diatom taxa from PK 37 can be found in Pyle et al. (1998). The percent abundances of many of the more com- mon species show changes throughout the time period represented by the Pass Key core (Text-fig. 7). Nitz- schia granulata shows some of the largest changes in abundance (Text-fig. 7). This species is much more common deeper in the core, with percent abundances as high as 45% and 36% in the 64—66 cm and 50-52 cm samples, respectively. Above the 44—46 cm sam- ple, N. granulata is much less common, with percent abundances of 10% or less. Cyclotella cf. litoralis also shows changes in abundance, ranging from 12—18% in the deeper samples, and increasing to over 20% above the 44—46 cm sample (Text-fig. 7). The percent abun- dance of C. cf. litoralis reaches a high of 33% in the DIATOMS AND ENVIRONMENTAL CHANGE: HUVANE AND COOPER 15 Pass Key Core 37 PCA 0.13 Axis 2A Axis 1A = 0.69 Text-figure 8.—Principal components analysis ordination plot based on the diatom assemblages in Pass Key core 37. The numbers on the figure indicate sample numbers (the top depth). Circles are drawn around the samples from each zone. Arrows are drawn se- quentially from zone I to zone V and indicate how diatom assem- blages have changed during the last century. Zones are indicated by the following symbols next to the sample number: Zone I (70 cm; 1962 A.D.) filled circle. Zone II (64—50 cm; 1965-1972 A.D.) open square. Zone III (44—24 cm; 1974-1984 A.D.) diamond. Zone IV (20—4 cm; 1987-1995 A.D.) plus sign. Zone V (0 cm; 1996) open circle. 24—26 cm sample, decreases to 17% in the 20—22 cm sample, and resumes an increasing trend towards the surface of the core. Nitzschia cf. frustulum (Kutz) Grun. appears to have become less common through time (Text-fig. 7). The percent abundance of N. cf. frustulum decreases from a high of 12% in the 70—72 cm sample to <1% in the 64—66 cm sample. Relative abundance of this species remains low until the 10— 12 cm sample, where it increases to 5%. Principal Component and Cluster Analyses Several groups of samples can be identified from the PCA ordination diagram of the diatom assemblag- es from core PK 37 (Text-fig. 8). There is a shift in species composition from the bottom-most sample at 70-72 cm to the next sample at 64—66 cm. Samples between 64 and 54 cm group together on the ordina- tion diagram. Between 50 cm and 44 cm there is a transition group. The samples between 40 and 24 cm form a third group. Then there is a shift to a fourth group consisting of the 20—4 cm samples. The top oS) most sample (O—2 cm) contains an assemblage that is more like the third (40—24 cm) group. The cluster analysis clearly divides the samples into three main groups: 70-50 cm, 40—24 cm, and 20—0 cm (Text-fig. 9). Based on the cluster analysis and the PCA, five di- atom zones, spanning between 7 and 9 years each, are evident. The average sedimentation rate of 2.06 cm/yr was used to calculate the dates. Zone I ca. A.D. 1962 consists of only the one sample at 70—72 cm. Zone II occurs between ca. A.D. 1965 and 1972 (64—50 cm). The third zone occurs between ca. A.D. 1974 and 1984 (44—24 cm) and zone IV occurs between ca. A.D. 1987 and 1995 (20—4 cm). The last zone V occurs in A.D. 1996 and contains only the uppermost sample at 0—2 cm. Zone I is characterized by a peak (12%) in the rel- ative abundance of Nitzschia cf. frustulum (Text-fig. 7). Nitzschia granulata (Text-fig. 7) has an abundance of 9% in zone I, and during zone II, the average abun- dance increases to 34% with a maximum of 45% and a minimum of 25%. Epiphytic taxa, including Coc- coneis placentula var. euglypta, Mastogloia crucicula, and M. ovalis increase in abundance between ca. A.D. 1967-1969 (56—60 cm). These taxa show another in- crease at the lower boundary of zone III, between ca. A.D. 1963 and 1975 (44—40 cm). Zone III is also marked by a sharp decline in N. granulata to a zone average of 6%. Cyclotella cf. litoralis increases in zone III with a peak relative abundance of 33% (Text- fig. 7). In zone IV, there are increases in Amphora coffeaeformis (Ag.) Kutzing, which has an average of 6.3% during this zone compared to an average of 2% for the previous three zones combined. There is also an increase in Mastogloia elegans Lewis to a zone average of 2% (Text-fig. 7). The average abundance of this species in the previous three zones is only 0.6%. Zone V is marked by an increase in N. granu- lata to 7.5%, along with a slight increase in Cyclotella cf. litoralis. Diatom Species Diversity As in core RB 19A, species diversity in core PK 37 mirrors species richness (Pyle et al., 1998). Species diversity in this core is negatively correlated (1 = 0.75) with the abundance of Nitzschia granulata, the species that dominates the assemblages of zone II. In general, diversity is lowest in zone II and highest in zone IV when there are the lowest percentages of N. granulata (Text-fig. 10). Centric : Pennate Ratio C:P ratios increase in the Pass Key core from be- tween 0.12 and 0.22 in the deepest samples to over 154 BULLETIN 361 =) e@ ee Pass Key Core 37 ce as e CONISS yp ya 1990 1985 25 1980 E o S & r= 19754 o& fa) 1970 oo 1965 1960 0.2 0.4 0.6 75 Total sum of squares Text-figure 9.—A stratigraphically constrained cluster analysis of the Pass Key core 37 diatom assemblages. The Y axis shows sediment depth with the top of the core at the top of the diagram. The second Y axis shows dates based on Pb-210 analyses. The samples counted and diatom zones are indicated on the left. 0.35 in the 24—26 cm sample, decreasing to 0.18 in the 20—22 cm sample and then resuming a gradually increasing trend toward the top of the core. The high- est ratios occur between 36 and 24 cm (A.D. 1979— 1985). DISCUSSION RUSSELL BANK 1882-1949 The bottom zone I (A.D. 1882-1888; 130-138 cm) in Russell Bank core 19A is difficult to interpret due to the poor diatom valve preservation. Many of the 1995 Diversity mean = 3.00 1985 1976 Depth (cm) Date cP 1966 mean = 0.25 1956 Difference Difference Text-figure 10.—Diversity and C:P profiles for Pass Key core 37. Both diversity and the C:P ratio are shown as a difference from the core average. The core mean diversity = 3.0. The core mean C:P = 0.25. broken valve pieces were unidentifiable to species or even genus level. However, it was possible to deter- mine whether the valves were pennate or centric. Thus C:P values are probably not affected by preservation quality. However, the low species diversity may have been affected by preservation quality. Salinity may have been relatively high during this time, as Cyclo- tella litoralis is a marine species (Lange and Syver- ston, 1989). The prevalence of two Mastogloia species (sp. A and sp. R) in RB 19A zone II (A.D. 1888-1921; 130— 90 cm) is also difficult to interpret at the present time. Diversity was generally high during this zone. De- Felice (1976) found that epipelic (bottom-dwelling) di- atom communities were more diverse as compared to epiphytic communities in his study of Florida Bay di- atoms. Therefore, these taxa may be part of an epipelic assemblage. Further study of the literature is necessary in order to determine whether these particular Masto- gloia taxa have been described, and if any autecology is known. These species were not common in an anal- ysis of diatoms from modern surface sediment samples in Florida Bay (unpublished data). This suggests that there have been significant changes in the diatom as- semblages at the Russell Bank site in Florida Bay since around A.D. 1920. DIATOMS AND ENVIRONMENTAL CHANGE: HUVANE AND COOPER 15 During zone III (ca. A.D. 1921-1949; 90-56 cm), the salinity around Russell Bank was likely relatively low based on the abundance of Nitzschia granulata, a species found in modern assemblages from sites with salinities between 8 and 24 ppt (Huvane, in press). However, the presence of Grammatophora cf. ocean- ica var. macilenta, a taxon associated with more saline conditions in Florida Bay (Huvane, in press) increases during this period. This conflicting evidence may be explained by salinity fluctuations in the bay. The pres- ence of taxa indicative of less saline conditions may reflect average or minimum salinities during that time period. It is possible that intermittent periods of higher salinity allowed for the increase in the Grammatopho- ra species. RUSSELL BANK AND PASS KEy 1949-1996 The increase in Cocconeis placentula var. euglypta frustules during zone IV (A.D. 1949-1972; 56-28 cm) suggests that the water was at least periodically brack- ish at this time. This taxon is characteristic of fresh- water (e.g., Patrick and Reimer, 1966), but also occurs in brackish water (e.g., Cooper, 1995b). In a study of Florida Bay surface sediment samples, this taxon was most abundant at the least saline site that had an av- erage salinity of 7.7 ppt (Huvane, in press). Mastogloia corsicana, a taxon associated with sites in Florida Bay that have salinities between 20 and 33 ppt (Huvane, in press), increases after A.D. 1953 (zones IV and V), although there is also a peak around A.D. 1932 (76-78 cm) during zone III. Synedra sp. A, another taxon associated with higher salinity sites in Florida Bay (between 19 and 32 ppt: Huvane, in press) starts to increase at the upper boundary of zone IV. The increase in these taxa along with the decrease in Cocconeis placentula var. euglypta suggests that salin- ity was increasing during zone V (A.D. 1972-1992; 28—4 cm). The diatom assemblages in the Pass Key core 37 suggest that salinity increased during the same general time period, between A.D. 1974 and 1995. This is ev- idenced by a decrease in Nitzschia granulata, and in- creases in Mastogloia corsicana, and M. elegans that have been described in the literature as marine (Hu- vane, in press; Foged, 1984; Yohn and Gibson, 1983b). Mastogloia corsicana, M. crucicula, M. ovalis and Cocconeis placentula var. euglypta were found in sea- grass samples collected in February 1999 from Florida Bay (Huvane, unpublished data). These taxa have also been noted elsewhere in the literature as epiphytic (e.g., Patrick and Reimer, 1966; Hustedt, 1927-1964; Navarro, 1982; DeFelice, 1976; Stephens and Gibson, 1979). Higher percentages of these epiphytes in core RB 19A starting around A.D. 1953, indicate that dur- Nn ing zone IV (A.D. 1949-1972; 56-28 cm,) there was more sub-aquatic vegetation available for colonization by epiphytic diatoms. In the Pass Key core 37, a sim- ilar diatom-inferred increase in sub-aquatic vegetation occurs later, between A.D. 1967 and 1977. In the Russell Bank core 19A, increases in C:P ra- tios occur between A.D. 1972-1992 (zone V). In the Pass Key core, increases occur between A.D. 1979 and 1984 (zone III). These increases can be interpreted in several ways. The increase in the centric diatom Cy- clotella cf. litoralis could be an indication of increases in salinity as other changes in the stratigraphy of both the Pass Key and the Russell Bank cores suggest. This species has been described as a marine planktonic form (Lange and Syversten, 1989). Another explana- tion is that there are more planktonic algal blooms, possibly related to increases in nutrients. Such blooms could increase the number of centric planktonic dia- toms as well as decrease the number of pennate ben- thic diatoms by reducing light availability to the bot- tom. Increased levels of sediment suspension could also serve to inhibit the growth of benthic diatoms. Population declines of seagrass in Florida Bay could also increase this ratio, as many of the pennate diatoms are epiphytic. COMPARISONS TO OTHER INDICATORS The diatom inferences concerning salinity and sea- grass cover generally coincide with the inferences made from benthic faunal indicators. In the Russell Bank core 19B, benthic foraminifera show significant assemblage changes around 1940, indicating an in- crease in salinity (Brewster-Wingard ef al., 1997). Di- atom assemblages also show shifts during this interval, but the salinity inference is ambiguous. Foraminifera assemblages indicative of lower salinities are common between about A.D. 1960—1980 (42-18 cm) (Brew- ster-Wingard et al., 1997). The increase in the diatom Cocconeis placentula var. euglypta between A.D. 1953 and 1972 (28-50 cm) also suggests lower salinities. Foraminifera assemblages indicate a shift to higher sa- linities between A.D. 1975 and 1980 (24-18 cm) (Brewster- Wingard et al., 1997). This up-core increase in salinity is also indicated by changes in diatom as- semblages starting around A.D. 1972. In the Pass Key core 37, foraminifera remains in- dicate increases in salinity between A.D. 1965 and 1978 (64 and 38 cm), and after about A.D. 1989 (14 cm) (Brewster-Wingard ef al., 1998a). Diatom indi- cators suggest an increase in salinity starting around A.D. 1975 (44 cm). However, one of the salinity in- dicators, Mastogloia elegans, does not increase until after A.D. 1986 (20 cm), suggesting that there may 156 BULLETIN 361 have been shifts in salinity between A.D. 1975 and 1986. Mollusc data suggests that seagrass is the dominant substrate in the time period between A.D. 1921—1976 (88—22 cm) in core RB 19B (Brewster-Wingard et al., 1998b). However, the highest percentages of mollusc species indicative of seagrass occur after A.D. 1948. The relative abundances of epiphytic diatoms in core RB 19A indicate that seagrass is dominant between ca. A.D. 1953 and 1972 (50-28 cm). Between about A.D. 1921-1948 (88-56 cm), Nitzschia granulata abun- dances increase, and this species has not been noted in grass samples from Russell Bank, but it has been noted in surface sediments from both Russell Bank and Pass Key (unpublished data). Thus, the diatom data suggest that there was some bare sediment available for the colonization of this diatom species during this interval. In the Pass Key core, mollusc data suggest that sea- grass cover increases between A.D. 1965 and 1978. This agrees with the diatom assemblage data, which shows high abundances of epiphytic diatoms during this period. Minor discrepancies between diatom indicators and faunal indicators (foraminifera and molluscs) may be explained by a variety of factors. For example, the spatial scale that is reflected by each group may differ. Microscopic diatoms may be deposited in sediments further away from their original habitat than the larger mollusc shells. Other factors to consider are the relative sensitivity of the indicators to environmental change and the re- productive rates of the organisms. Diatoms are known to respond fairly quickly to changes in water quality (Dixit et al., 1992) and therefore may show an earlier response to changes in salinity. This appears to occur at the Russell Bank site where diatom indicators of increasing salinity appear around A.D. 1972, while faunal indicators do not appear until A.D. 1975. How- ever, this pattern was not recognized in the Pass Key core, and may only reflect variations in the sedimen- tation rates between cores RB 19A and RB 19B. IMPACTS ON DECISION MAKING These data have several implications for manage- ment decisions and research goals. Fluctuations in both seagrass cover and salinity suggest that management plans should be designed to incorporate some degree of natural variability. Future research should address questions concerning specific limits of natural vari- ability such as the natural extremes of salinity and the periodicity of such extremes. It would also be useful to know the extent of seagrass cover prior to the major anthropogenic disturbances in South Florida. The fos- sil data suggest that seagrass cover has fluctuated in the past, and these fluctuations are important in our understanding of seagrass population dynamics. In ad- dition, the mechanisms that initiate both natural and anthropogenic-induced variability need further explo- ration in order to implement remediation. SUMMARY The data from Russell Bank core 19A suggest that there have been fluctuations in salinity and seagrass cover during the last hundred years. This is consistent with what has been found in other studies of sediment cores from Florida Bay. Diatom indicators of salinity and seagrass coverage show the same general patterns as other fossil indicators from these cores. In the Rus- sell Bank core 19A, the earliest diatom assemblages indicate a period of higher salinity. Between A.D. 1890 and 1920, epiphytic diatoms were not common, supporting mollusc data that indicates bare sediment as the dominant substrate during this period. Epiphytic diatoms increase in abundance after about A.D. 1950 and remain common until about A.D. 1972, which is consistent with the mollusc data that indicates a de- cline in epiphytes around A.D. 1970. In the Pass Key core 37, diatom epiphytes increase at the same time as mollusc epiphytes (between A.D. 1967-1977). There are indications of salinity fluctuations after ca. A.D. 1950 in both cores. The presence of Cocconeis placentula var. euglypta between ca. A.D. 1953 and 1970 in core RB 19A suggests that salinities were low- er during this time. Diatom indicators suggest increas- es in salinity in both cores after ca. A.D. 1970. This is also consistent with faunal indicators of salinity. 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Botanica Marina, vol. 25, pp. 277-288. CHARTERS HISTORICAL TRENDS IN EPIPHYTAL OSTRACODES FROM FLORIDA BAY: IMPLICATIONS FOR SEAGRASS AND MACRO-BENTHIC ALGAL VARIABILITY T. M. CRonin!, C. W. HoLMeEs?, G. L. BREWSTER-WINGARD!, S. E. ISHMAN?, H. J. DowsettT', D. KEYSER*, AND N. WAIBEL! 'US Geological Survey, Reston, Virginia 20192 °US Geological Survey, St. Petersburg, Florida 33701 sDepartment of Geology, University of Southern Illinois, Carbondale, Illinois 62901 4Zoologisches Institut und Museum, Hamburg, Germany ABSTRACT Living and fossil epiphytal ostracodes from central and eastern Florida Bay were investigated to determine historical trends in seagrass and macro-benthic algal habitats during the past century. Living assemblages collected in February and July, 1998 from 15 sites throughout Florida Bay revealed that Loxoconcha matagordensts and Malzella floridana are the dominant species living on Thalassia and that Xestoleberis spp. is the most abundant ostracode group living on Syringodium and marine algae such as Chondria. Peratocytheridea setipunctata is a species that is common on muddy substrates and on Halodule. Temporal trends in epiphytal ostracode abundance were reconstructed from isotopically-dated sediment cores from Whipray mudbank, Russell Bank, Bob Allen mudbank, Pass and Park Keys, Taylor Creek (near Littlke Madeira Bay) and Manatee Bay. The results show that there have been frequent changes in the relative frequencies of L. matagordensis, M. floridana, and Xestoleberis over the past century. Prior to the mid-20" century, seagrass- and algal-dwelling ostracode species were relatively rare at our sites in central and eastern Florida Bay. Ostracode assemblages living between about 1900 and 1940 were characterized by moderate to large proportions (10O—>60%) of Peratocytheridea setipunctata when Thalassia- and macro-benthic algal-dwelling species were less common than during the later half of the 20" century. Beginning about 1930, and continuing until 1950, P. setipunctata populations experienced significant declines while L. matagordensis and Xestoleberis increased progressively from 0-10% to >25—40%, depending on the site. This faunal shift suggests that there has been a greater abundance and/or density of subaquatic vegetation in central Florida Bay over the past 50 years than in the prior half century. Since 1950, several sites in central and eastern Florida Bay have experienced large swings in the proportion of seagrass and macro-benthic algal-dwelling species suggesting subaquatic vegetation has been extremely dynamic spatially and temporally over decadal timescales. Some of these oscillations, such as the decline in L. matagordensis, Xestoleberis, and M. floridana during the 1970s and early 80s may represent large-scale dieoffs. The possible influence of climatological factors on salinity and epiphytal ostracodes is also discussed. INTRODUCTION Growing efforts to restore polluted and disturbed coastal and estuarine ecosystems to a more natural state rely increasingly on retrospective paleoecological analyses using isotopically-dated sediment cores to es- tablish ecosystem trends and to better understand eco- system functioning (e.g., Brush 1986; Vallette-Silver 1993). Paleoecological studies are especially important because few monitoring programs have been in place for a long enough period to sufficiently establish the natural range of habitat variability both prior to, and subsequent to human influence. Moreover, in addition to anthropogenic disturbance of ecosystems, extrinsic factors such as climatic variability are also critical as- pects to estuarine functioning (Peterson ef al., 1995; Cronin et al., 2000). Florida Bay, a large (2,200 km/?), shallow (<3 m), tropical to subtropical lagoon is one such ecosystem believed to have been affected by human activities over the past century. For example, Smith et al. (1989) sug- gested that canal construction from 1912 to 1931 de- creased freshwater flow into Florida Bay, especially through Shark River Slough, and led to hypersalinity. Declines in seagrass populations in parts of Florida Bay since 1987 have been attributed to chronic hypoxia re- sulting from human alteration of freshwater inflow from the Everglades, and to pathogenic slime molds (Zieman et al., 1989; Robblee er al., 1991). McIvor er al. (1994) pointed out that, in addition to its impact on seagrasses, hypersalinity of Florida Bay also may have contributed to recent increases in mangrove mortality. They com- piled measurements of salinity obtained over the past 40 years showing that, since at least the late 1950’s, seasonal hypersalinity has characterized some regions. Salinity values reached as high as 50 to 70 parts per thousand (ppt) in eastern and central parts of the bay. Light and Dineen (1994, p. 48) expressed the widely held view that human alteration of Everglades hydrol- ogy is unprecedented for the late Holocene as follows: 160 BULLETIN 361 “The first reclamation efforts in the Everglades began in 1881. Just over 100 years later, Governor Graham formally embraced a system-wide restora- tion initiative entitled “Save Our Everglades.’ More has happened to the Everglades between these two benchmarks than in the preceding 50 centuries.” Given the temporally and spatially incomplete his- torical monitoring record of Florida Bay, several pa- leoecological studies have been conducted to recon- struct various ecosystem parameters. Smith ef al. (1989) concluded, on the basis of analyses of autoflu- orescence of a Solenastrea coral skeleton from Peter- son Key in the Atlantic transition zone of Florida Bay that canal construction severely diminished fresh water inflow into Florida Bay, especially through Shark Riv- er Slough, reaching minimal flow around 1931. They argued that the hydrological impact of canal construc- tion was severe enough to disrupt the natural 4- to 6- year periodicity of freshwater inflow resulting in un- precedented episodes of hypersalinity. Swart ef al. (1996a) attributed carbon and oxygen isotopic vari- ability in a Solenastrea colony from the Lignumvitae Basin, also in the Atlantic transition zone of Florida Bay, to construction of the Florida East Coast Railway between 1905 and 1912. They also suggested that fre- quent hurricanes between 1912 and 1948 caused great- er exchange of water between the bay and reef areas, but that after 1948, decreased hurricane activity led to the retention of organic material in the bay and the initial stages of eutrophication. Brewster-Wingard ef al. (1998) analyzed mollusks and foraminifers from four of the sediment cores examined in this study (Bob Allen, Russell, Taylor, and Pass) to determine the long- term trends in salinity and benthic habitats. Their study shows that subtle shifts in the faunal distributions oc- cur around 1910, but after 1940, the pattern departs substantially from the pre-1900 pattern. The amplitude of shifts in salinity indicators increased from 15%— 20% about the pre-1900 mean to 40%—60% about the post-1940 mean. In general, there was an increase in epiphytal molluscan species throughout this century; which Brewster-Wingard ef al. suggested might be due to changes in water-management practices. Ishman er al. (1998) found on the basis of paleoecological data that environments of Manatee Bay had changed sig- nificantly over the past century. Despite the growing amount of paleoecological data, there is still a large degree of uncertainty about the ecosystem history of Florida Bay and the factors that cause interannual and interdecadal variability in Florida Bay environments. The present study is de- signed to address the scale, timing and possible causes of subaquatic vegetation (seagrasses and macro-ben- thic algae) variability in Florida Bay using quantitative analyses of ostracodes from sediment cores from cen- tral and eastern Florida Bay, and from Manatee Bay just outside the northeast margin of Florida Bay (Text- fig. 1). This study has two parts. First, we conducted a study of the dominant ostracode taxa living on mod- ern seagrass (especially Thalassia) and marine algae in Florida Bay. Second, we examined trends in sea- grass and algal-dwelling species preserved in sediment cores. ACKNOWLEDGMENTS We are especially grateful to Robert Halley and Eu- gene Shinn for obtaining cores and helping with the stratigraphy of mudbanks and to the South Florida Wa- ter Management District (SFWMD) for support and logistical aid throughout this study. We are grateful to John Repetski and Sarah Gerould for critical reviews. We also thank Dave Rudnick of SFWMD who has championed paleoecological research in Florida Bay. Mike Bothner and John Robbins kindly provided ac- cess to their age model for the Bob Allen and Russell cores. Jeffrey Stone and Kristi Alger, US Geological Survey, and Thomas Scott and Harley Means, Florida Geological Survey, assisted in collecting the modern samples. Jeffrey Stone developed and maintains the ecosystem history database. Sara Schwede, Marcy Ma- rot, Jill D’Ambrosio, lan Graham, and Jean Self-Trail helped with the laboratory processing of the ostra- codes. The study is a contribution to the USGS Eco- system Program. MATERIAL AND METHODS MODERN ECOLOGICAL SAMPLES Epiphytal ostracodes were studied from samples of living seagrasses and macro-benthic algae collected from 15 stations in February and July 1998 in order to obtain quantitative data on species that live on sub- aquatic vegetation during winter and summer months (Text-fig. 1). These samples were divided into three substrate groupings, those with mainly Thalassia, those with mainly macro-benthic algae, and those with primarily Halodule grasses. The macro-benthic algae included mostly Laurencia, Chondria, and Polysi- phonia; the seagrasses were Thalassia, Halodule and Syringodium. Two sites with coarse shelly substrate were also examined. After washing vegetation in a 63 4m sieve with tap water, the first 100 individual ostracode specimens were picked with fine brush under a binocular micro- scope from the size fraction >150 to 850 pm. This size fraction contains the adults and several juvenile instars of all common podocopid ostracodes living in Florida Bay. SEAGRASS OSTRACODES: CRONIN ET AL. 161 m Vegetation Sites [[-—~juggg “a i 0 2 4 6 @ Sediment Cores Text-figure 1.—Map showing location of modern ostracode samples (squares labeled FB-) and sediment cores at Whipray, Russell, Bob Allen, Park, Pass, Manatee Bay (MB-1), and Taylor Slough. SEDIMENT CORE SITES Seven sediment cores were collected along a south- west/northeast transect running from Whipray Key in central Florida Bay to Manatee Bay on the margin of Barnes Sound (Text-fig. 1, Table 1). Cores were taken by hand using a large-diameter hand-driven piston cor- er ranging in length from 74 cm (Pass Key) to 156 cm (Bob Allen Key). Five cores came from mudbanks in <1 m of water from the central part of Florida Bay (Text-fig. 1): one each from Whipray mudbank (WR- 25B), Bob Allen mudbank (BA-6-A), Russell Bank (RB-19-B). Pass Key (PA-37) and Park Key (PK 23- A). One core came from the transition zone in Little Madeira Bay near the mouth of Taylor Creek (T-24) and another core was taken from Manatee Bay (MB- 1) located on the western edge of Barnes Sound, near the northeast part of Florida Bay. Information on each core site is given in Table 1, in preliminary reports (Wingard et al., 1995; Brewster-Wingard et al., 1997; Ishman, 1997), and at the website http://geolo- gy.er.usgs/gmapeast/fla/home.html.) Whipray Keys are located in central Florida Bay; the core was taken on a mudflat on the eastern side of Whipray basin. The core has a top mixed layer to 12 cm representing the past ~ 15—20 years; below this, the 710Pb-determined sediment accumulation rate is 0.43 cm/year until reaching equilibrium at 40 cm. Below this level, the material is too old for *!°Pb dating. The Table 1.—Core site information for South Florida paleoecology of ostracodes.* Sediment accumulation Sampling Site Latitude Longitude Core length Water depth rate # interval Russell Key (19-B) 25°03.83'N 80°37.49'W 140 cm 0.51 m 1.22 2 cm Bob Allen Key (6-A) 25°01.39'N 80°39.41'W 156 cm 0.6 m 0.75-1.04** 2cm Manatee Bay (MB-1) 25°15.69'N 80°24.06'W 120 cm ~1.0 m ~1.0 2 cm Taylor Creek (T-24) 25°11.4'N 80°38.4'W. 86 cm ~0.5 m NA 2cm Park Key (PKK-23A) 25°10.45'N 80°57.46'W 86 cm ~lm 0.78 2cm Pass Key (PK-37) 25°14.78'N 80°40.82'W 74 cm ~lm 2.06 ~3 cm Whipray (WR-25B) 25°07.12'N 80°73.85'W 80 cm ~1.25 m 0.43 5 cm * Sources: Bob Allen and Russell cores: Wingard er al. (1995), Brewster-Wingard er al. (1997); Manatee Bay cores: Ishman et al. (1996, in press), respectively. # centimeters per year. ** Higher rate was used in Figures 8—11. BULLETIN 361 162 pnut yyos ur [jays DIIUAANDT ‘a/NPO|VE] “‘DISSV]DY TL, piuoydissjog pisspjoyy ‘vioydojng ‘piupuoyy DISSDIDYL, ‘VIUOYdIsSAJog ‘Dla4puoyy anpo]|PH piuoydisdjog ‘PIssv]OY UMIPOSULIKS, DIIUAANDT ‘ajNpo|PH] ‘vissvjpyy “viuoydissjog “viapuoyyD DISSDIDY], ‘VI4puoyy DIAPUOYD ‘DISSD]DY TL, anpopHY ‘vissvjpyy ‘vioydoing ‘piuoydissjog pisspjpyy, ‘vaoydoiwg ‘piauasnvy psoydolvg ‘DIQUAINDT ‘DISSD]VYL, DIIUIANDT ‘vISsDjDY], ‘ajnpojpH ‘piddny dIQRURA ‘DISSDIDY |. aynpo]DH DISSDIDYL. DISSDIDY], ‘DIQUaNDT ‘PiuoydisAjOg ‘pl4puoyy UNSSDSADS piuoydiskjog ‘Mi4puoyy ‘vIssv]vY DISSDIDYL, ‘a/NPo]D DISSDIDY], ‘DI4puoyD piuoydisdjog ‘PIssp]DY], DIIUAANDT ‘DIUOYAdISA]Og ‘DISSD]DY I. DIIUIANDT ‘Aa]NPOIVE] ‘DISSV]DY TL. DISSDIDY], ‘DIQUANDT ajnpo]PH DIQUIANDT ‘UMNIPOSULAAG ‘aj]npo -[DE] ‘DISSDIDY] *{,DIQUaANDT/VLUpUuoYy) ‘j,viupuoyyD/{,,viuoydisAjog A[NPO]VY ‘PIQUAANDT/VIAPUOY) ‘DIDUIANDT] “DISSD]DY TL, pluoydisajJod ‘PISSPIDY DIDSSDAIUL DpaMo]DP]T ‘WUiniposulsKg anpo]MH ‘syplomagd ‘piuoydiséjOg ‘DISsv]VY I, paoydolyg ‘vIIUAANDT] ‘VISSDIDY a/npolpH DISSD]DY [ ‘a/NPO|PH {Dlupuoy)/{,puoydisKjog ‘VISsP]DY uINSsDSADG ‘vAoydolwg ‘vISsv]DY], ‘DlADjNGvIaIy ‘{Dlupuoy,) ‘,,pluoydisdjog *{plouasnvT/piipuoyy DISSDIDY I, psoydolpg ‘,piuoydisasjog *{plouasnvy] *j,p14puoy)D DIIUAANDT ‘a]NPOI|DE] ‘DISSVIDY T. anpoppY ‘j,piuoydisjog “‘DIguasNVT ‘DISSD]DY [, uonRj}asaAQ, 86 901 OOl 88 L6 8Ol +8 [RI0OL OMNON OANA OnmrNDAONMl OC Xe} Yemnae) ata (oa) 6S Iv al oI S s1laqa] -O1SAX Lv n- ce v I DIDI -ound -1as d rat > (OV IQ (00 rt NON OS SO Saco pupp -MoUe ppyjaz TPW rn ononaa SISUAPAOS ,.dV.IS -DIDU “T (O) GOOG) (OAS) <0) ee (OI (2) 1) (OO) eee (GI ee eae, (ONG) ee <6 (9) 17) SE) ONSNONS) =e 1S) 1S) =e OOtO< -qng ve 6 8C qeus Ica 86-994 VC 68C I 1cd4 86-994 661 LI g 0cdH 86-494 6 6l AT v Oca 86-994 6 ol | 7e)! € Ocdd 86-494 661 ULI c Ocdd 86-994 66! 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SEAGRASS OSTRACODES: CRONIN ET AL. 163 slower sediment accumulation rate at Whipray Keys means that a 2-cm sample represents on average about j four years of sediment. = Russell Bank is a few hundred meters across and our uly & about | km long. Wanless and Tagett (1989) studied a3 Se Wao = the stratigraphy of Russell Bank and concluded that es SiS Gare during its construction, it had accreted in a southward 23 ey age apy = direction. The Russell Bank core (RB-19-B) was taken (oye a a iy > Ee et & Sis 853 w from the top of Russell Key mudbank. The Bob Allen = eS Sys Sey = core (BA-6-A) was obtained from the flank of another 4 = 38 Tf 2a so 0 4 Sj : 30 se Zé Si §6&s8 8 accretional mudbank located about 4 km to the south- A SG Soe ee. & west of Russell Key. Both the Russell and Bob Allen > 3 Gee aa & y Seon eS Sis ae & cores have been the subject of intensive isotopic dat- 3s 2s E= 5 8 Sic J Ip) ESS SSeo5R SES 8 ing, and the age model based on 7!°Pb and '*’Cs of Sa, Ss 8 5 83 S 0 Robbins er al. (2000) is used here. Sh EPs SSH ena as Park Key core was taken on the western side of the SseubvF Sessegssk 8 bank, which, based on aerial photographs, is the ac- OBS 5 a, 8 Ss] vcs p grap SMISTSSESSSSsus creting side of the bank. The core was taken in 10 cm SES IS ISianse Wheelie of water on top of the bank. The Whipray, Russell, Bob Allen, Park and Pass a Keys sites are strategically situated in the central and S12°S 2S & *A Ba eastern parts of Florida Bay where periods of sum- Fe mertime hypersalinity have occurred, especially during ne years with low freshwater discharge (Robblee ef al., 2S ES OS eS 1991; Fourqurean et al., 1993). aie The Manatee Bay core (MB-1) site is located to the Los By Aico AONE rae, northeast of Florida Bay (the “inner zone” of Wanless zs © and Tagett (1989) near the outflow of the C-111 canal. Nn o Manatee Bay is connected to the Biscayne Bay hydro- EEloon CAD A OD OM logic system. The C-111 canal was completed in the S815 t = =6©6 : ; Su 1960s and its outflow has a large impact on Manatee g P 42 Bay salinity (Light and Dineen, 1994; Ishman et al., S| eR ESO ays NAA ee 1998). Core MB-1 penetrates about 106 cm. The upper ~j S er 85-90 cm are carbonate muds; the lowermost 36 cm * a are a peat and peaty-shelly marl containing limnic and 1 9 & 5 . . 2 FIOOO OOS = aa BO] oligohaline microfaunas (Ishman et al., 1998). + Z The Taylor Slough core (T-24) is located in Little a : Madeira Bay, a region sensitive to changes in outflow ret || G2 a SX eh 2 n : ; S|Sah Raa A AA ARE from Taylor Slough, which drains the southeastern part 5 of the Everglades. Like the Manatee Bay core, T-24 3 does not have a isotopic age model, although the fau- FEinnvo orm oO Ne} Nowe) fo) ikine | al ak eiliorol Ue CIS NS Iie moat M nal patterns suggest that salinity-related changes oc- i 0 curred in this region over what is believed to be the 5 5p past century or so of sedimentation based on the first we) a 9 7 a E I As stratigraphic appearence of Casuarina (Ishman et dl., =) || sat Sb At = nN (coma) Be Sofiilll PB Be 1998). 5 a The seven cores cover a wide range of salinities that Q se vary over monthly and interannual timescales. For ex- Llano © 2 ample, Halley et al. (1995) showed that in June 1995, araaag Qa Yel al no ‘o a é : i SA eneeree ec pet bale pee Mine sed OPEN Coulee during a period of relatively low fresh water flow and oi 2 rainfall, salinities were high ranging from ~25 ppt at Ss 2 . . sleexw eer 2 2m we : Taylor and Manatee Bay to >36 ppt at Whipray Basin. E 4 aa 2 2 Sarita 2 Bale Conversely, in August 1995, during an apparently wet 21 ee Be ee ee lx period with higher fresh water flows, salinity ranged 164 BULLETIN 361 from 4—5 ppt at Taylor Creek to 30 ppt at Whipray. Even larger historical swings in salinity described by Mclvor et al. (1994) are likely to be a factor in inter- preting paleoecological records. Florida Bay sediments consist mostly of unconsol- idated muds containing abundant macro- and micro- fossils. Following lithological description and X-ray radiography, sediments were sampled every 2 centi- meters for *!°Pb dating and micropaleontological anal- ysis. Approximately 20—40 g of dry sediment was washed through 63 pm sieves and ostracodes in the size fraction >150 and 850 4m were picked with a fine brush. This size fraction yields adults and several juvenile molt stages of essentially all major species living in Florida Bay; our focus here is on trends in epiphytal species. OSTRACODE SPECIES CENSUS DATA The counts of key ostracode species from the mod- ern vegetation and sediment samples are given in Ta- ble 2 with the major seagrasses and/or macro-benthic algae genera found at each site. Appendix | contains the species counts for the seven sediment cores. Nore ABOUT OSTRACODE TAPHONOMY There are four lines of taphonomic evidence sug- gesting there is minimal transport of ostracode valves at the studied sites. First, the size of adult ostracode valves and carapaces (a carapace consists of two artic- ulated valves held together after death by a tooth-and socket hingement) are too large to have been trans- ported large distances in Florida Bay. Halley er al. (1997) showed that most mudbank sediment >~63 kLm is autochthonous within a mudbank. Depending on the species, adult ostracode valves and carapaces are >180 «m in length and thus, most adults are in the size fraction of sediment that is not transported. Sec- ond, juvenile valves representing | to 4 molt stages prior to the adult molt are commonly associated with conspecific adult valves and carapaces. Although time constraints precluded detailed analyses of species’ population structure, these qualitative observations in- dicate most species are represented by juvenile and adult individuals. Third, articulated ostracodes cara- paces are common in mudbank sediments and such preservation would not be expected had the ostracodes been transported by currents which tend to disarticu- late the carapace. Fourth, fossil assemblages consist of ecologically compatible species; there is no faunal ev- idence for transport of allochthonous species from oth- er parts of Florida Bay or adjacent habitats. In sum, ostracode taphonomy indicates that the majority of os- tracodes examined in this study from the >63 ym size fraction represent individuals that lived, died and were buried at the mudbank. STATISTICAL METHODS We used the changing proportions (also called rel- ative abundances) of ecologically significant indicator species to infer past environmental changes. In paleo- ecological research, the number of individuals of a par- ticular species n, is often expressed as S >a = 2 i=] where S is all species in the assemblage and n is the total number of individuals in the sample (see Buzas, 1990). The proportion of a species is expressed as p = n/n, and p has certain confidence limits that depend on both the value of p for that species and on the value n. Because n, the abundance of ostracodes, varies with- in each core and among cores, and because picking microfossils is so time intensive, it is important to con- sider what values of n ensure statistical reliability of species’ proportions and still yield meaningful tem- poral patterns. Ideally, the confidence limits for any given p value should not exceed the observed down- core temporal changes in p if trends and oscillations in p are to be considered meaningful. Confidence limits on species’ proportions are often expressed in paleoecology using the binomial distri- bution (e.g., Patterson and Fishbein, 1989; Buzas, 1990) as follows: o = (pq/n)!” where o = the binomial standard error, p = n/n, or the proportion of the i species, q = 1 — p. The con- fidence limits d are expressed as: d = =+to where t corresponds to the chosen level of confidence (i.e., t = 1.96 for 0.95 confidence). Table 3 illustrates the different confidence limits d, for three values of n, 100, 200, 300 and 1000 individ- uals. We see that for a species that comprises 10% of an assemblage (p = 0.1), d decreases progressively with increasing sample size (n) from 5.9% (100 indi- viduals), 4.2% (200 individuals) and 3.4% (300 indi- viduals). For a dominant species comprising 50% of an assemblage, the comparable values are higher, 9.8%, 6.9% and 5.7% respectively. The values of d are essentially meaningless for very rare species (p < 1%, Buzas, 1990). In general, the results presented below for Florida Bay suggest that the long-term variability in indicator species proportions (p) often exceeds the confidence limits (d) imposed by total abundance (n). Thus, we SEAGRASS OSTRACODES: CRONIN ET AL. 165 Table 3.—Confidence limits for 100, 200 and 300 individuals at different relative frequencies. Pp q n sigma t d 0.1 0.9 100 0.03 1.96 0.0588 0.2 0.8 100 0.04 1.96 0.0784 0.3 0.7 100 0.04582576 1.96 0.0898 1848 0.4 0.6 100 0.04898979 1.96 0.09602 0.5 0.5 100 0.05 1.96 0.098 0.6 0.4 100 0.04898979 1.96 0.09602 0.7 0.3 100 0.04582576 1.96 0.0898 1848 0.8 0.2 100 0.04 1.96 0.0784 0.9 0.1 100 0.03 1.96 0.0588 0.1 0.9 200 0.0212132 1.96 0.04157788 0.2 0.8 200 0.02828427 1.96 0.05543717 0.3 0.7 200 0.0324037 1.96 0.06351126 0.4 0.6 200 0.03464102 1.96 0.06789639 0.5 0.5 200 0.03535534 1.96 0.06929646 0.6 0.4 200 0.03464102 1.96 0.6789639 0.7 0.3 200, 0.0324037 1.96 0.06351126 0.8 0.2 200 0.02828427 1.96 0.05543717 0.9 0.1 200 0.0212132 1.96 0.04157788 0.1 0.9 300 0.01732051 1.96 0.0339482 0.2 0.8 300 0.02309401 1.96 0.04526426 0.3 0.7 300 0.02645751 1.96 0.05185673 0.4 0.6 300 0.02828427 1.96 0.05543717 0.5 0.5 300 0.02886751 1.96 0.05658033 0.6 0.4 300 0.02828427 1.96 0.05543717 0.7 0.3 300 0.02645751 1.96 0.05185673 0.8 0.2 300 0.02309401 1.96 0.04526426 0.9 0.1 300 0.01732051 1.96 0.0339482 0.1 0.9 1000 0.00948683 1.96 0.01859419 0.2 0.8 1000 0.01264911 1.96 0.02479226 0.3 0.7 1000 0.01449138 1.96 0.028403 1 0.4 0.6 1000 0.01549193 1.96 0.03036419 0.5 0.5 1000 0.01581139 1.96 0.03099032 0.6 0.4 1000 0.01549193 1.96 0.03036419 0.7 0.3 1000 0.01449138 1.96 0.028403 1 0.8 0.2 1000 0.01264911 1.96 0.02479226 0.9 0.1 1000 0.00948683 1.96 0.01859419 Pp = proportion of species; n = number of individuals, sigma = standard error, t = level of confidence, d = c. chose to obtain 100 individual valves and/or carapaces from each 2-cm interval (except in the Park Key core, where we picked 300 individuals) to determine decad- al and sub-decadal faunal trends across a wide area of Florida Bay. We were able to obtain about 100 indi- viduals +20 from most samples, with the important exception of the interval 72-134 cm in Bob Allen core where there were usually less than 10 individuals. Trends from this low abundance zone are interpreted with caution. TIME SERIES ANALYSES We examined trends in L. matagordensis at Russell Bank and compared them to trends in the Southern Oscillation index (SOI, a measure of strength of El Nino-Southern Oscillation) using time series analysis. For time series analysis, the age of each data point was estimated by linear interpolation between dated depths. We then interpolated the Loxoconcha and SOI records at constant |-year intervals. Both records were separated into pre-1940 and post-1940 segments. All segments were linearly detrended and the auto and cross correlation functions for pre-1940 and post-1940 calculated. From these functions the coherency and phase functions were calculated. DATING AND CORRELATION METHODS Isotopic dating by 7!°Pb and '*’Cs was carried out by Robbins ef al. (2000) to obtain age models for the Bob Allen and Russell Bank cores (see also Holmes et al., 2000). These investigators found that Bob Allen and Russell Bank cores BA-6-A and R-19-B have lin- ear sediment accumulation rates of 0.75—1.04 and 1.22 cm yr! respectively, for the period covering approx- imately the last 100-150 years. Park Key has an av- erage accumulation rate of about 0.78 cm yr~! and the 86-cm core represents approximately the last 100 years. Sediment accumulation at Whipray was much slower and there is an uncorrected radiocarbon age of ~3000 yr BP near the base. The age model for the Manatee Bay core is not as well established because 7!°Pb dating was unsuccessful for unknown reasons (see Ishman ef al., 1998). How- ever, a pollen age marker, the first appearance datum (FAD) of the genus Casuarina between 60 and 70 cm, suggests a maximum age for this interval at ~1890 and a probable age of 1920-1930, a time when this genus became abundant in South Florida (D. A. Wil- lard, personal communication). Similarly, the Casua- rina FAD in the Russell Key core lies between 94— 104 cm, a level consistent with the isotopic age model. TAXONOMIC AND ECOLOGICAL NOTES There is considerable taxonomic and ecological data on living ostracode populations collected from coastal bays and estuaries along the Atlantic and Gulf coasts. These include studies of Texas (Swain, 1955; King and Kornicker, 1970; Garbett and Maddocks, 1978) and Campeche, Mexico (Morales, 1966) lagoons; Baha- man (Kornicker, 1961, 1963), Veracruz (Krutak, 1982), and Belize carbonate platforms (Teeter, 1975); mangroves of southwest Florida (Keyser, 1975, 1976, 1977); the continental shelf off west Florida (Puri and Hulings, 1957; Benson and Colman, 1963; Hulings and Puri, 1964) and Florida Bay and other regions off western Florida (Puri, 1960), the Cape Romano region, northwest Florida (Benda and Puri, 1962); the Carib- bean and Gulf of Mexico (Maddocks, 1975), and the Atlantic coast (Cronin, 1979). Species were identified following the taxonomy of 166 BULLETIN Keyser (1976), Hazel (1983), Cronin (1979, 1990), and Garbett and Maddocks (1978). In Florida Bay sed- iment Malzella floridana (Benson and Coleman 1963) is synonymous with Radimella floridana littorala Grossman 1965 of Keyser (1976) and King and Kor- nicker (1970). Loxoconcha matagordensis Swain 1955 is a widespread epiphytal species living along the At- lantic and Gulf coasts. Xestoleberis spp. includes 3 to 4 species that were not distinguished from one another because it is difficult to identify species of Xestoleberis based solely on carapace features. Peratocytheridea setipunctata is conspecific with Haplocytheridea seti- punctata of some authors (see Hazel, 1983). SUBSTRATE AND MUDBANK STRATIGRAPHY Substrate is an important factor controlling the dis- tribution and abundance of organisms throughout Flor- ida Bay. Substrate types are generally divided into un- consolidated carbonate muds, hard bottoms (mostly in southern Florida Bay), mangrove islands (<2% of the Bay), and seagrass “‘meadows.” Seagrasses, which provide an important Florida Bay microhabitat for many species (e.g., Sheridan 1997), constitute an in- tegral component of mudbanks in the central part of the bay in that they stabilize and help build up the banks (Wanless and Tagett, 1989). The most important types of seagrass species in Florida Bay are: Thalassia testudinum (turtlegrass), Halodule (shoal grass,), Syr- ingodium (manatee grass), and Ruppia (Widgeon grass) (Robblee er al., 1991). There are also numerous species of marine algae living in Florida Bay, which provide habitat for ostracodes. Seagrasses play an important role in sedimentation on mudbanks in several ways. Wanless and Tagett (1989) reported that broad-bladed Thalassia tend to baffle wave and currents, an attribute that permits fine- grained sediment to accumulate. Thalassia rhizome mats also stabilize substrate. Swart and Kramer (1997) reviewed evidence that many organisms, primarily red algae and serpulid worms, and, to a lesser extent, mol- lusks, foraminifers and other organisms, encrust on Thalassia such that when seagrasses die, this carbonate material makes a large contribution to the total car- bonate production of the bay. In addition, Halley er al. (1997) observed that, although seagrasses are rare-to- absent in many mudbank sediment cores, seagrasses may still have been present when “‘grassless” deposits accumulated if those grasses had been living upstream of the core site. While this remains a tenable hypoth- esis at the local scale of mudbanks, our data on phytal ostracode species presented below suggest that over the last century, widespread changes in seagrass abun- dance have occurred. 361 RESULTS EPIPHYTAL OSTRACODE SPECIES IN MODERN FLORIDA BAY Vegetation and Substrate Many ostracode species are adapted to inhabit spe- cific substrates such as seagrasses and sandy bottoms. Text-figure 2 presents data on the four ostracode taxa from Florida Bay stations collected in February and July 1998. For February and July samples, L. mata- gordensis, M. floridana, and Xestoleberis spp. account for a combined total of 74.5% and 70.9% of the total assemblages, respectively. Two notable exceptions are one sample from FB21 and one from FB6 from Feb- ruary 1998, which are shelly substrate covering soft mud with sparse Halodule. These two samples con- tained abundant P. setipunctata. Another exception is the abundance of P. setipunctata at sample FB-14. Of the total 2,658 individuals collected from 36 marine algae and seagrass samples during February 1998, 808 (30.4%) were L. matagordensis, 668 (25.1%) were Xestoleberis spp., 614 (23.1%) were M. floridana, and only 91 (3.4%) were P. setipunctata. Of 1,379 total individuals obtained from 15 samples in July 1998, 248 (18%) were L. matagordensis, 274 (19.9%) were M. floridana, 173 (12.5%) were P. setipunctata, and 442 (32.1%) were Xestoleberis spp. Text-figures 3 and 4 compare the relative frequen- cies of these four taxa by season and by vegetation type. The relative frequencies of ostracode taxa living on macro-benthic algae, and the seagrasses Thalassia and Halodule are generally similar in both February and July collections, except that L. matagordensis is relatively more abundant on algae during February, and both L. matagordensis and M. floridana are more common on Thalassia in February. The species com- position of ostracode assemblages on Halodule is very similar during both months. Xestoleberis spp. predom- inates on marine algae in both February and July sam- ples. In general, these data show that L. matagordensis and M. floridana are characteristic epiphytal species living on Florida Bay seagrasses (Thalassia, Halodu- le), and that Xestoleberis spp. prefer macro-benthic al- gal habitats. P. setipunctata is most common in sam- ples with Halodule, a pattern that may be an artifact of the sampling of Halodule. Halodule is typically found on very soft substrates, therefore root material and adhering mud is often collected with the grass sample. These results confirm those of earlier studies that L. matagordensis (Tressler and Smith, 1948; Swain, 1955; Morales, 1966) and related species (i.e., Loxo- concha japonica, Kamiya 1988; L. fischeri, Teeter 1975) prefer mainly phytal habitats. Our evidence that SEAGRASS OSTRACODES: CRONIN ET AL. 167 July 1998 Xestoleberis P. setipunctata M. floridana L. matagordensis 25%) at winter temperatures of 19— 27°C. These may reflect different seasonal life histories for these two species, allowing them to inhabit the same epiphytal habitat on Thalassia. King and Kor- nicker (1970) found a similar relationship as they doc- umented seasonal changes in the relative abundance of SEAGRASS OSTRACODES: CRONIN ET AL. 169 Florida Bay Ostracode Taxa: Salinity and Temperature Relationships salinity temperature 100 75 5 50: Loxoconcha Malzella percent total assemblage P. setipunctata Xestoleberis 15 20 25 30 35 40 45 ppt February: open diamonds July: solid circles Text-figure 5—Relationships between temperature and salinity and four ostracode taxa based on 1998 collections from Florida Bay. 170 BULLETIN 361 M. floridana and L. matagordensis in Texas Bays and lagoons. M. floridana also seems to be relatively common at salinities between 15—20 ppt. However, King and Kor- nicker (1970) studied the seasonal ecology of M. flor- idana and demonstrated that this species dominated assemblages from Texas lagoons during the summer months when salinity often exceeded 35—40 ppt. Thus, M. floridana is a euryhaline species tolerating a wide range of salinities. The relationship of Florida Bay os- tracodes to salinity and its application to reconstruction of salinity history will be treated in a separate study. In summary, it must be emphasized that multiple environmental factors including, but not limited to, substrate, salinity, and temperature, ultimately deter- mine the relative proportion of various ostracode spe- cies in any assemblage. There is nonetheless compel- ling ecological evidence on Atlantic and Gulf Coast ostracodes, accumulated over several decades of re- search, in various marginal marine settings, and in the new analyses presented above, that certain ostracode species have preferences for phytal habitats. This hab- itat preference makes M. floridana, L. matagordensis and Xestoleberis spp. potentially valuable paleoecolog- ical “proxy” indicators of changes in the relative abundance of subaquatic vegetation in Florida Bay when they are studied in well-dated sediment cores. HISTORICAL TRENDS IN EPIPHYTAL OSTRACODES Florida Bay Mud Island Stratigraphy and Sedimentation The stratigraphy, sedimentation, and microfaunal ta- phonomy of Florida Bay mudbanks make them excel- lent sedimentary environments in which to study the paleoecology of Florida Bay. Before discussing his- torical trends in ostracodes, we briefly describe some important attributes of mudbank geology and paleon- tology based on papers by Enos and Perkins (1977, 1979), Wanless and Tagett (1989) and Swart and Kra- mer (1997) and references therein. Florida Bay is divided into semi-isolated, shallow (usually <1 to 2 m) sub-basins separated from each other by small, partially emergent islands barely ex- posed during low tide. These islands are called mud- banks (Enos and Perkins, 1979; Wanless and Tagett, 1989). “Mud island” is the term given to the small surfaces that sit on top of, or on the flanks of mud- banks. There are more than 200 mud islands in Florida Bay; they consist mostly of fine-grained carbonate mud whose internal stratigraphy and abundant micro- fossils make them amenable to isotopic dating and pa- leoecological analysis (Wanless and Tagett, 1989; Swart and Kramer, 1997; Robbins ef al., 2000). Understanding sedimentary processes in Florida Bay in general, and on mudbanks, in particular, is crit- ical for establishing faunal and ecosystem trends from sediment cores. Holocene sediment blankets the floor of Florida Bay forming a thin veneer covering the limestone “bedrock” consisting of the late Pleistocene Miami Limestone. These sediments consist of about 95% unconsolidated carbonate derived mainly from biogenic skeletal material from serpulids, calcareous algae, foraminifers, coelenterates, ostracodes, mol- lusks, and other organisms (Enos and Perkins, 1977; Nelson and Ginsberg, 1986). Most sediments that form the mudbanks are classified as bioturbated pelloidal and molluscan wackestones and/or mudstones (Enos and Perkins, 1979). In their review of the origin and stratigraphy of mudbanks, Wanless and Tagett (1989) classified Flor- ida Bay mudbanks into four categories reflecting bank morphology, stratigraphy, sedimentology and bank dy- namics. In the “‘Central Migration Zone” of Florida Bay, where the Bob Allen, Russell, and Park Keys are located, sedimentary processes that form mudbanks are generally dominated by erosion on the windward side and deposition on the leeward side. These pro- cesses produce features that have a history of migra- tion that is dependent on the predominant winds, sed- iment supply and wave energy (Enos and Perkins, 1979; Wanless and Tagett, 1989). Although mudbank sediments are often bioturbated, in some cases they consist of finely laminated muds suggesting little or no bioturbation. Stratigraphic and isotopic studies also in- dicate that some mudbanks have experienced relatively high rates of fairly continuous sedimentation over the past few centuries (Holmes ef al., 1997). The provenance of mudbank sediments is also im- portant in determining the significance of faunal and paleoecological trends. Halley et al. (1997) concluded on the basis of bomb-produced radiocarbon analyses that mudbank sediment coarser than 250 «.m is not transported, sediment between 63 and 250 ym is sometimes transported, and sediment finer than 63 4m is almost all transported. In sum, the stratigraphy and sedimentation of Flor- ida mudbanks is relatively well known, sediment ac- cumulation rates are high and provide interdecadal temporal resolution, and adult and most juvenile os- tracodes studied from the >150 ym size fraction are not transported (smaller juveniles are more likely to have been transported), and abundant. These attributes make paleoecological study of Florida Bay a viable means to reconstruct the history of Florida Bay. Trends in Epiphytal Species Text-figures 6 and 7 show changes in relative fre- quencies of the four indicator ostracode taxa in seven SEAGRASS OSTRACODES: CRONIN ET AL. a. Downcore Trends in Xestoleberis in Florida Bay percent total assemblage 0 10 20 30 40 O 10 20 30 40 0 10 20 30 40 0 ) 0 0 10 20 20 10 6 20 40 40 20 , ; 30 30 60 60 a 40 40 80 80 low abundance 50 50 100 aaa 100 Be Ee 60 120 120 an gS = <= 70 140 140 80 Qa ® 160 160 90 2 80 o , 6 Whipray Bob Allen Russell Oo 0 10 20 30 40 50 0 10 20 30 40 50 0 10 20 30 40 500 low abundance S 0 0 0 10 20 20 20 40 40 30 60 60 40 80 80 50 100 5 100 60 120 120 70 140 80 160 160 171 0 10 20 30 4 Ol. 10 20 30 40 0 0 20 25 40 50 60 80 75 100 100 120 Park & Pass Taylor Manatee 10 20 30 40 S50 0 10 20 30 40 50 O 10 20 30 40 50 0 0 20 25 40 50 60 80 75 100 100 120 b. Downcore trends in Loxoconcha matagordensis in Florida Bay Text-figure 6—Plot of relative frequencies of Xestoleberis (6a top) and L. matagordensis (6b, bottom) for seven cores. Park Key core is solid line, Pass Key core is dotted line. cores from Whipray, Bob Allen, Russell, Park, Pass, Taylor, and Manatee Bay, plotted against core depth. Several stratigraphic trends are evident from these re- cords: 1. All cores except that from Park Key show increases in the proportions of Xestoleberis from O to 10% in the lower intervals of the cores to 20—40% in upper intervals (Text-fig. 6a). All cores except Pass Key show increases in the proportions of L. matagordensis from O—10% to > 10-30% (Text-fig. 6b). 3. Proportions of M. floridana oscillate widely in all cores, generally with greater proportions in the up- per intervals, except at Manatee Bay where this species declines significantly (Text-fig. 7a). There is a net decline in the proportions of P. se- tipunctata in all cores (Text-fig. 7b). i) It is also noteworthy that at the Bob Allen and Rus- sell Bank cores, two cores with the most detailed sam- pling, the first order trends in all four taxa are gener- ally similar, taking into account the artifacts produced by low abundance between 70 and 120 cm at Bob Allen. The temporal significance of these trends is revealed by plotting the relative frequencies of each species against age derived from the lead-210 dating for five cores from central and eastern Florida Bay (Text-figs. 8-11; Table 1; Holmes et al., 1997). It should be kept in mind that the limitations of the *!°Pb dating preclude precise inter-site comparison of interannual trends, es- pecially during periods in the early 20" and late 19" century when the precision of 7!°Pb dating diminishes. Rather, our objective is to search for synchroneity or asynchroneity in trends in indicator species over inter- decadal timescales. During the period 1910 through the 20’s, L. mata- gordensis (Text-fig. 8) is relatively rare at Russell, Park and Bob Allen, though the Bob Allen core has sparse ostracodes in this interval. All three cores have 172 BULLETIN 361 a. Downcore Trends in Mailzella floridana in Florida Bay 10 20 30 40 50 60 0 102030405060 0 1020 30405060 0 0 0 0 10 20 20 10 , 20 20 40 40 30 30 60 60 40 40 80 80 a 50 50 100 100 a 60 120 120 70 70 140 140 80 80 160 160 90 Bob Allen abundance low Whipray Russell core depth (cm) 0 20 40 60 80 0 20 40 60 80 9 20 40 60 80 0 0 0 0 10 20 20 10 20 40 40 ay 3 30 60 60 a8 40 40 80 80 50 50 100 100 , 60 60 120 120 ae 70 140 ] 140 80 80 160 160 90 a lise 0 10 20 30 40 50 60 0 10 20 30 40 50 60 0 20 40 60 80 Manatee 20 40 60 80 O 20) 740) 1607 80 0 20 40 60 80 0 0 20 25 40 50 60 80 75 100 100 120 b. Downcore Trends in Peratocytheridea setipunctata in Florida Bay Text-figure 7.—Plot of relative frequencies of M. floridana (7a top) and P. setipunctata (7b, bottom) for seven cores. Park Key core is solid line, Pass Key core is dotted line. intervals where this species is relatively common (>20—30%) during the late 1940’s through the 1950’s. Another epiphytal ostracode species, Paracytheroma stephensoni (not shown in figure) is also relatively abundant in the Russell Bank core during this interval. After the 1950’s, the abundance of L. matagordensis fluctuates at Russell and Bob Allen Keys and shows a gradual increase in abundance at Park Key. Three cores exhibit significant declines in L. matagordensis during the late 1970’s and early 1980’s: Bob Allen (from 20 to 0%), Russell (from 28 to 8%) and Pass Key (from 40 to <10%). Malzella floridana appears to have been an impor- tant member of the assemblage during the late 19" and early 20" centuries at all sites (Text-fig. 9). At Russell Bank, there was a progressive decline in M. floridana between 1935 until the late 1950s when this species reaches its lowest percentages. The Russell and Park Key records suggest that following a period of mini- mum abundance in the 1950’s, M. floridana became a more abundant part of the ostracode assemblage (~50%) during the 1960’s through 1980’s. However, wide swings in its abundance (swings from less than 20% to almost 50%) occur over the past 30 years at all the sites. The most noteworthy pattern is reminis- cent of that observed for L. matagordensis. Two cores (Russell and Bob Allen) show oscillations in M. flor- idana during post-1960’s: Park Key shows a gradual increase of M. floridana with minor declines during the 1980’s and 1990’s, whereas Whipray shows a de- cline from 35 to ~20% since the 1960’s. A decline in M. floridana also occurred at Pass Key (from 40 to 10%) during the 1960s and 1970s. In general, these data provide evidence for fluctuating abundances of M. floridana including declines during the 1970s and ear- ly 1980s at some sites. An increase in the abundance of Xestoleberis (Text- fig. 10) is dated at between the 1920’s and 1960's at Whipray, Bob Allen and Russell Keys when Xestole- beris rose from less than 10-15% to 30—40%. Xesto- leberis abundance seems to have peaked during the 1950s and 1960s, declined during the 1970’s and the early 1980s, then increased again at all sites except Park Key during the late 1980’s and 1990’s. Except SEAGRASS OSTRACODES: CRONIN ET AL. 173 Historical Trends in L. matagordensis in Florida Bay 2000 1990 1980 1970 1960 1950 1940 1930 1920 year 1910 1900 1890 1880 1870 ® c ° N ) ° = © v = = a © S ° 1860 1850 1840 1830 1820 1810 0 10 20 30 40 50 0 10 20 30 40 S50 (0) 2000 2000 1990 1990 1980 1980 1970 1970 1960 1960 1950 1950 1940 1940 1930 1930 1920 1920 1910 1910 1900 1900 1890 1890 1880 1880 1870 1870 1860 1860 1850 1850 1840 1840 1830 1830 1820 1820 1810 1810 20 30 40 50 0 10 20 30 40 50 0 10 20 30 40 50 percent total ostracode assemblage Winipray ey Bob Allen Key Russell Key Park Key Pass Key Text-figure 8.—Trends in L. matagordensis in five cores from Florida Bay. for the two samples dated at around 1890-1900, the abundance of Xestoleberis at Park Key remained fairly steady over the past century. Significant declines in the relative frequencies of P. setipunctata (Text-fig. 11) begin in the early 1930s at Whipray, Bob Allen, Russell, and Park Keys and con- tinued, with short reversals at Bob Allen and Park, up through the 1990s. Reticulocythereis floridana (not shown), another species that lives on sediment, also declines in abundance from bottom to top of the Rus- sell Bank core. All cores suggest that P. setipunctata was a much more important part of the Florida Bay ostracode fauna during the late 19" century and first half of the 20" century that it was during the last half century. Because both L. matagordensis and M. floridana have similar ecological requirements in terms of their preference for Thalassia as a habitat, we lumped them into a single “Thalassia” indicator index and com- pared the temporal changes in their abundance in the Russell and Park Key cores (Text-fig. 12). These sites are located about eight kilometers apart, both have abundant ostracodes throughout the core, excellent *10Pb chronology and high sediment accumulation rates, and thus should be comparable if the observed trends are typical of the area. The results suggest that prior to ~1920 oscillations in “Thalassia” species are out of phase at the two sites, though we cannot exclude the possibility that the age model for the lower parts of these cores is incorrect. After a minimum abun- dance at both cores around 1920, both cores show the following similar fluctuations in the abundance of these species. After ~ 1920, there is an increase to 40— 50%, then, a peak in abundance ranging from 50% to 65% occurred at Russell and Park respectively ~1936 and 1948, followed by a decline to <40% in the late 1950s, a steep rise in the 1960s, a decline in the 1970s at Russell Key, and an increase to historically the high- est levels at times during the late 1970s to the 1990s. Thus, even though L. matagordensis and M. floridana are known to have different patterns of relative abun- dance during a single year due to seasonal effects (King and Kornicker, 1970), the first-order decadal patterns since ~1920 are similar at the two sites, sug- 174 BULLETIN 361 Historical Trends in M. floridana in Florida Bay Whipray Key Bob Allen Key Russell Key Park Key Pass Key 2000 2000 2000 2000 2000 peest 1990 1990 1990 1990 1990 1980 1980 1980 1980 1980 1970 970 1970 1970 1970 1960 960 1960 1960 1960 1950 950 1950 1950 1950 1940 1940 1940 1940 1940 1930 930 1930 1930 1930 1920 920 1920 1920 1920 i 1910 1910 e 1910 1910 1910 S 1900 1900 2 1900 1900 1900 1890 1890 E 1890 1890 1890 1880 1880 FI 1880 1880 1880 1870 1870 E 1870 1870 1870 1860 1860 1860 1860 1860 1850 1850 1850 1850 1850 1840 1840 1840 1840 1840 1830 1830 1830 1830 1830 1820 1820 1820 1820 1820 1810 1810 1810 1810 1810 10 20 30 40 50 60 0 10 20 30 40 50 60 0 10 20 30 40 50 60 10 20 30 40 50 60 0 10 20 30 40 50 60 percent total ostracode assemblage Text-figure 9.—Trends in M. floridana in five cores from Florida Bay. gesting that similar changes in seagrass and algal hab- itats have occurred. POSSIBLE CLIMATIC EFFECTS ON FLORIDA BAY EPIPHYTAL OSTRACODES Environmental factors such as salinity variability caused by climatological and hydrological processes may also contribute to the observed decadal changes in epiphytal ostracodes and their inferred seagrass hab- itats. Dwyer and Cronin (this volume) demonstrated that the influence of interannual and decadal variability in rainfall, especially during winter season, has a large impact on long-term salinity variability in Florida Bay. Salinity in this portion of Florida Bay can range from lower polyhaline values, <20 ppt, to hypersaline >45— 50 ppt. Thus, to examine the possible role of clima- tological factors on Florida Bay epiphytes, we com- pared trends in the relative frequency of L. matagor- densis from the Russell Bank, Park Key and Bob Allen cores with records of winter rainfall in south Florida (Text-fig. 13). We chose this species because it its eco- logical preference (salinity range is upper mesohaline- polyhaline and epiphyte habitats of Thalassia and Zos- tera beds) is well known from numerous studies along the Gulf of Mexico and Atlantic coast of North Amer- ica (see above). The trends shown in Text-figure 13 suggest that for most of the past century there is an inverse relationship between winter rainfall and L. matagordensis abun- dance. During wet periods (winter rainfall > 30 cm/ yr) such as the 1930s, 1950s and post-1980, L. mata- gordensis is relatively abundant compared to drier pe- riods (winter rainfall < 30 cm/yr) of the 1900-1910, 1915-1925, 1940s, 1960s and 70s. Two notable ex- ceptions occur in the Russell core where during the late 1940s/early 1950s and around 1970, L. matagor- densis is abundant during periods of low rainfall. A greater abundance of L. matagordensis, relative to oth- er more marine species, during periods of wet climate and lower Florida Bay salinity would be expected based on this species’ preference for polyhaline con- ditions. SEAGRASS OSTRACODES: CRONIN ET AL. 175 Historical Trends in Xestoleberis in Florida Bay 2000 2000 2000 2000 1990 1990 1990 1990 1980 1980 1980 1980 1970 1970 1970 1970 1960 1960 1960 1960 1950 1950 1950 1950 1940 1940 1940 1940 1930 1930 1930 1930 = 1920 1920 1920 we oO g 1910 5 1910 1910 1900 2 1900 1900 1890 : 1890 1890 1880 Fe 1880 1880 1870 é 1870 1870 1860 1860 1860 1850 1850 1850 1840 1840 1840 1830 1830 1830 1820 1820 1820 1810 1810 1810 0 10 20 30 40 0 10 20 30 40 0 10! 20) 30) 40 0 10 20 30 40 percent total ostracode assemblage Whipray Key Bob Allen Key Russell Key Park Key Pass Key Text-figure 10.—Trends in Xestoleberis in five cores from Florida Bay. There are two important sources of uncertainty in this analysis. First, it is not clear how rainfall-driven salinity variations might affect the various species of seagrass, especially Thalassia, which L. matagordensis prefers as its habitat. Salinity is probably influencing both the seagrass habitat of L. matagordensis as well as this species ability to reproduce and survive in a particular part of the bay (see Discussion). Second, we assume that there is no “‘lag”’ time in the response of populations to large-scale salinity oscillations such as those observed by Robblee ef al. (1991) and Dwyer and Cronin (this volume) for the past few decades. Nonetheless, the broad patterns suggest that salinity, as well as seagrass availability, is a factor in control- ling the abundance of L. matagordensis over decadal timescales. DISCUSSION The ecological data on ostracodes presented above provide evidence that certain ostracode species are pre- dominantly epiphytal in habitat in modern Florida Bay and the fossil data show that there have been signifi- cant interdecadal changes in their relative frequencies at several localities in central and eastern Florida Bay. The most important issue regarding the interpretation of these interdecadal faunal trends is whether changes at each site represent a local trend at a single mudbank or whether they signify synchronous, regional events that characterized the central and eastern parts of Flor- ida Bay. If these do indeed signify regional changes in Florida Bay benthic habitats, then what are their causes? It is unlikely that two of the major faunal trends discussed above would occur by chance simultaneous- ly at four or five mudbanks located kilometers apart. The first is the long-term decline in the sediment- and Halodule-dwelling P. setipunctata coincident with the rise in species that inhabit Thalassia and macro-ben- thic algae (L. matagordensis, M. floridana and Xesto- leberis spp.) during the mid-20" century. An increase in epiphytal species is not only evident in central and eastern Florida Bay, but also near the northern tran- 176 BULLETIN 361 Trends in P. setipunctata in Florida Bay 2000 2000 2000 2000 2000 1990 1990 1990 1990 1990 1980 1980 1980 1980 1980 1970 1970 1970 1970 1970 1960 1960 1960 1960 1960 1950 1950 1950 1950 1950 1940 1940 1940 1940 1940 1930 1930 1930 1930 1930 1920 1920 = 1920 1920 1920 1910 1910 : 1910 1910 1910 . S 1900 1900 FE 1900 1900 1900 > 1890 1890 5 1890 1890 1890 1880 ws === 2 1880 1880 1880 1870 1870 —1870 1870 1870 1860 1860 1860 1860 1860 1850 1850 1850 1850 1850 1840 1840 1840 1840 1840 1830 1830 1830 1830 1830 1820 1820 1820 1820 1820 1810 1810 1810 1810 1810 0 20 40 #460 0 20 40 60 0 20 40 #60 0 204 On GO 0 20 40 60 percent total ostracode assemblage Whipray Key Bob Allen Key Russell Key Park Key Pass Key Text-figure 11.—Trends in P. setipunctata in five cores from Florida Bay. sition zone at the Taylor core site and in Manatee Bay, though these sediments are not as well dated as the other sites. Thus, central Florida Bay most likely ex- perienced region-wide benthic habitat changes during the mid-20" century. Moreover, similar synchronous changes in mollusks and benthic foraminifers also oc- curred in these areas (Brewster-Wingard et al., 1998; Brewster-Wingard and Ishman, 1999). The second event is the decline in seagrass and al- gal-dwelling ostracodes species during the late 1970s and 1980s. Although the strength of the decline varied by species and by site, the stark contrast between the abundance of epiphytal species during the 1950s and 60s and the very low abundance at times during the following two decades suggests a broad regional shift occurred at this time. What were the causal factors behind these 20" cen- tury changes? Many hypotheses have been proposed to explain the causes of seagrass die-off in the late 1980s, but these theories do not address natural cycles of change in seagrass distribution, and the possibility that seagrass ““meadows”’ were not always as exten- sive as they were in the early 1980’s. The most sig- nificant and often cited factors proposed to explain the die-off include changes in salinity (Boesch ef al., 1993; Robblee et al., 1991; Eichinger et al., 1998; Blakesley, 1998), light availability (Boesch ef al., 1993; Stumpf and Frayer, 1998), water temperature (Robblee et al., 1991; Zieman, et al., 1998), nutrient availability (Lapointe ef al., 1994), disease (Blakesley et al., 1998; Boesch et al., 1993; Durako, M. J. and Kuss, 1994; Robblee et al., 1991), eutrophication (La- pointe ef al., 1994), and hypoxia of roots (Carlson et al., 1994; Robblee et al., 1991). One approach to addressing the question of seagrass dieoffs is to first examine what has caused both the build-up of sub-aquatic vegetation beginning around 1950, and the subsequent decline in recent decades. One hypothesis is that this mid-century shift was re- lated to anthropogenic disruption of freshwater fiow into Florida Bay, which has been described in papers by Light and Dineen (1994) and Mclvor et al. (1994). Beginning in 1910 and continuing for the next few decades, canal and levee construction caused the shut- SEAGRASS OSTRACODES: CRONIN ET AL. 177 Trends in seagrass ostracodes at Russell and Park Keys 2000 ae 1990 : Russell : G aN. Park 1970 oe 1960 6 oy es Key CEC rer Gitapncntaedsacassco ° = 1950 < oa on ~ 1940 & 1930 ~~ oO ae 1920 Fe < 1910 ; ee a > 1900 Ei nO eo “oe 1890} “0 1880 - 7 T a 100 percent total Text-figure 12.—Plot of summed proportion of L. matagordensis and M. floridana in Russell Bank and Park Key cores. off of freshwater flow southward from Lake Okeecho- bee diverting it towards the Atlantic Ocean. Smith et al. (1989) interpreted the changes in Florida Bay coral fluorescence as a manifestation of these freshwater di- versions. It is possible that as a result of these changes to the natural hydrology, Florida Bay has, over the past 5 decades, become more sensitive to variability in freshwater flow and/or to precipitation, at least com- pared to the period prior to ~1940. Another idea is that other anthropogenic events such as the construction of the railway between Miami and Key West disrupted the exchange of water between Florida Bay and the Gulf of Mexico (Swart et al., 1996a). This “railway” hypothesis holds that the 1907-1912 building of the railway restricted circula- tion, which allowed the products of the oxidation of organic carbon to build up in the bay. This event might, in theory, have also disrupted Florida Bay cir- culation and natural salinity variability. However, one would have to explain the mid-century faunal shifts preserved in central Florida Bay sediment cores in terms of a lagged faunal response to the completion of the railway. The decreased frequency of hurricanes since 1948 was also noted by Swart er al. (1996a) as a possible explanation for diminished exchange of Florida Bay and Gulf of Mexico water and increased late 20" cen- tury eutrophication that was evident from their coral isotope record. It is interesting to speculate that the carbon isotopic excursions recorded by Swart et al. may be related to the appearance of seagrasses and algae seen in our core records. It is nonetheless diffi- cult to separate the hurricane influence from that of ENSO (strong El Nino events are correlated with de- creased hurricane landfall for the U.S. Atlantic coast, Gray, 1984; O’Brien, 1996) and from the impact of engineering projects in the 1950s and 60s (Swart et al., 1996a). An alternative hypothesis to explain changes in epi- phytal ostracode species might be that, since the 1940’s, climatological factors have caused greater var- iability in regional precipitation, at least relative to the 19" and early 20" centuries. This *‘climatic’’ hypoth- esis would hold that post-1940 paleoecological vari- ability is related to “natural’’ changes in the climate system rather than human activities. There is, in fact, considerable evidence that beginning in the mid- 1970’s, ENSO has behaved irregularly compared to its behavior over the past few centuries. Trenberth and Hurrell (1994), for example, showed that El Nino ep- isodes became more frequent and La Nina episodes were weaker and less common since 1976. In addition, changes in longer-term climatic variability related to the Pacific-North American (PNA) pattern (Wallace and Gutzler, 1981) also occurred in the mid-1970s. Henderson and Robinson (1994) showed that during certain seasons changes in the PNA index coincided with precipitation variability in the southeastern Unit- ed States, though they cautioned that south Florida precipitation exhibits patterns quite distinct from those in states to the north. 178 Russell Bank Park Key BULLETIN 361 Bob Allen Key % L. matagordensis O10. 20,20. 20 5 10 2000 Sooo 1990 i on 1980 ew TSO. ae 1970 ; -——_ Fee 1960 = er _ 1950 saa w AES 2 1940 Be aaa 1930 3 Vee e 1920 [] f a 1910 “4, 1900 Cie 1890 1880 1870 40 LSS 2025) S035 3570 25) 20 45,40 35) S025 ae20 Winter rainfall (Nov.-April) cm/yr wetter (7-point smooth) ee ee Oe Text-figure 13.—Plot of relative frequency of L. matagordensis at Russell Bank, Park Key and Bob Allen Key compared to winter rainfall in South Florida (NOAA region #5) for the period 1880-1995. The rainfall record is a 7-point running mean. Note that during most dry periods, when Florida Bay salinity was high, L. matagordensis abundance is low; the opposite situation is seen during wet periods. See text. There is also a large body of literature on 20" cen- tury trends in extreme weather events, including trop- ical cyclones and extra-tropical storms (see Nicholls et al., 1996). Most studies, however, have been carried out on global or hemispheric scales and the impact of long-term climate trends on Florida is uncertain. One exception is the study of a 240-yr isotope record from a Monastrea coral from Biscayne Bay, Florida by Swart et al. (1996b). They discovered from oxygen isotopic patterns that the 20" century may have been significantly wetter that most of the 18" and 19" cen- turies. If such a trend were characteristic of the latter part of the 20" century in the nearby Florida Bay area, one would expect the net effect to be a long-term de- crease in salinity, rather than increasing periods of hy- persalinity. At this time, the climatological and canal hypotheses seem to account for observed temporal trends in epi- phytes and vegetation described above. Natural pro- cesses have certainly exerted strong influence on Flor- ida Bay habitats over the past century and continue to do so. But the degree of impact may have been altered, perhaps even exacerbated in some areas, by anthropo- genic diversion of freshwater inflow. The shift in Flor- ida Bay benthos during the mid-century, the relation- ship between Loxoconcha and rainfall/salinity, and the large amplitude of post-1950 faunal events, all suggest that further investigation of the relationship between cli- SEAGRASS OSTRACODES: CRONIN ET AL. 179 matological processes, such as ENSO and PNA, and the timing of Florida Bay ecosystem changes are war- ranted. Moreover, while climatological variability would have affected the entire Florida Bay ecosystem, information about the direct causes of seagrass die-offs, such as disease or light attenuation, need further study within the context of climate variability. In regard to the topic of restoration of the “natural state’’ of Florida Bay seagrass and algae, our data sup- port historical observations that central Florida Bay has experienced oscillations in the availability of sea- grass and macro-benthic algal habitats that have been especially severe during the past 30 years. Generally, seagrass and algal habitats in the studied part of Flor- ida Bay have been much more abundant and/or dense during the last 50 years than during the first half of the century. Thus, how one defines the “natural state”’ of Florida Bay then depends on the period one selects. It is very likely that central and eastern Florida Bay had extensive seagrass and macro-benthic algal “meadows” during the mid-20" century and these meadows diminished during the 1970’s and 1980’s. However, seagrass and macro-benthic algal habitats were probably sparse in this region during the 19" and early 20" centuries, at least relative to the 1950s and 1960s. REFERENCES CITED Benda, W.S., and Puri, H.S. 1962. The distribution of foraminifera and Ostracoda off the Gulf Coast of the Cape Romano area, Florida. Transac- tions, Gulf Coast Association of Geological Societies, vol. 12, pp. 303-340. Benson, R.H., and Coleman II, G.L. 1963. Recent marine ostracodes from the eastern Gulf of Mex- ico. Kansas Univeristy Paleontological Contributions no. 31, Arthropoda, article 2, 52 pp. Blakesley, B.A., Landsberg, J-H., Ackerman, B.B., Reese, R.O. Styer, J.R., Obordo, C.O., and Lukas-Black, S.E. 1998. 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Appendix la.—Pass Key Ostracode census data. Ie, seti- Total Depth punc- — Loxo- Mal- Xesto- Ostra- (cm) Year tata concha zella leberis codes 1 1997 0 13 52 16 118 3 1996 (0) 1 43 14 67 5) 1995 0 0 34 7 Sp) 9 1993 0 14 35 14 116 13 1991 0 15 35 15 124 17 1989 i 6 36 22 94 21 1987 0 8 50 15 112 25 1985 0 17 45 4 114 29 1983 0 21 33 7 94 33 1981 0 15 21 7 94 Si/ 1979 0 3 26 17 86 41 1977 0 39 11 iil 1 53 1971 0 48 16 8 121 69 1964 5 18 38 7 98 73 1962 0 47 20 14 108 182 BULLETIN 361 Appendix 1b.—Ostracode species census data, Bob Allen Key core 6-A. Actino- Acuticy- Cythero- Loxo- cythereis thereis Aglaio- morpha_ Cyther- Cyther- Dolero- Lepto- _ concha Loxo- Malzella _ Neone- Depth cf. sub- laevis- cypris Cytherel- paracas- ura ura cypriacythere matagor- concha flori- sidea (cm) quadrata —_sima sp. loidea tanea_ elongata fiscina sp- sp- densis spp. dana sp- 0 5 1 20 17 3 2 8 3 3 3 6 53 2 54 21 6 10 1 7 5 45 3 32 7 8 1 1 9 1 5 2 10 16 2 i 6 5 12 1 4 | 4 3 3 14 1 5 1 1 16 1 1 2 1 18 1 2 3 7 1 2 1 1 4 22 1 1 3 1 1 24 1 2 1 6 1 10 1 26 5 1 6 18 7 20 5 28 1 1 8 9 1 30 1 2 1 4 5 1 8 6 32 ] 1 1 6 2 6 3} 34 1 5 1 10 4 36 2, 1 12 3 10 2 38 2 2 1 1 8 5 3 40 4 2 2 49 2 19 17 42 2 1 1 1 12 2 11 6 44 1 | 9 1 5 2 46 1 10 1 2 29 2 19 2 48 1 1 1 3 7 1 8 4 50 2 10 I 3 8 + 34 39 I 52 1 4 2 1 1 itil 19 54 1 2 14 13 1 56 2 2 1 2 16 7 5 58 3 1 1 1 10 6 3 60 1 2 1 1 9 7 62 3 1 1 1 3 1 64 2 1 15 7 1 66 2 4 1 1 11 11 1 68 1 3 2 2 11 5) 70 3 13 2, 2 TP) | 1 1 74 1 | 1 2 76 78 3 80 1 1 82 2, 1 1 84 86 1 1 88 1 1 2 2 3 90 1 1 92 1 94 1 96 98 2 1 3 i 100 2 102 1 104 1 106 108 1 3 110 112 2 114 1 1 116 118 1 1 1 3 1 SEAGRASS OSTRACODES: CRONIN ET AL. 183 Appendix 1b.—Extended. Paracy- Peratocy- Paracy-. theroma_ Peratocy-__ theridea Radimella Reticulo- Triangulo- — Xesto- theroma stephen- theridea setipunc- Proponto- Proteo- | Puriana_ confra- cythereis cypris leberis | ?Micro- Total repexa soni bradii tata cypris — concha Spp- gosa_ floridana __laeva spp. cythere Ostracodes 1 7 1 2 10 67 9 4 2 14 3 1 3 13 67 269 12 1 33 3 1 4 5 28 197 5 4 1 1 30 3 3} 2 43 4 1 92 4 1 10 52 1 2 ) 4 99 2 6 46 1 8 3 3 77 1 11 2 1 20 3 2 6 1 5 31 2 8 1 2 19 3 5 1 6 22) 1 3 H 1 3 10 41 10 21 1 1 7 il} 115 2 2 1 7 13 45 3 4 1 1 1 8 19 65 1 8 2 1 16 48 3 17 ] 11 53 2 1 12 12 11 68 3 1 1 3 8 38 12 2 2 18 17 43 189 4 1 17 ] 10 6 75 1 ®) 5 5 39 9 3 4 25 3 2; 1 13 25 151 4 1 1 13 2 1 6 8 62 4 6 22 40 4 3 1 2 26 30 235 4 3 9 Sy 3 1 6 21 126 4 3 16 1 5 5 7 72 2 17 Ss) 3 2 5) 10 129 1 3 8 3 1 4 5) 50 1 16 1 7 46 3 4 18 6 6 1 48 4 10 1 5 8 54 4 23 7 8 2) 2 4 13 1 1 1 5 1 52 2 13 1 2 38 1 2 6 13 4 4 26 2 7) 4 2 2 7 2 5) 9 1 6 11 6 6 1 1 18 3 2 2 1 1 1 1 1 14 8 2 1 13 2 1 3 7 2 3 1 1 2 1 2 3 5) 24 1 1 3 1 8 1 2 1 1 3 2 1 3 2 1 3 3 | 14 1 1 1 3 1 7 13 l 16 184 BULLETIN 361 Appendix 1b.—Continued. Actino- Acuticy- Cythero- Loxo- cythereis thereis — Aglaio- morpha_ Cyther- Cyther- Dolero- Lepto- — concha Loxo- Malzella __Neone- Depth cf. sub- — laevis- cypris Cytherel- paracas- ura ura cypria cythere matagor- concha flori- sidea (cm) quadrata — sima sp. loidea tanea_ elongata fiscina sp. sp. densis spp. dana sp. 120 2 122 1 124 1 126 1 128 1 1 130 1 1 132 1 l 2 134 1 3 136 1 1 1 i 4 7 1 138 | 1 1 1 140 1 2 9 142 2 1 3 1 16 144 4 146 1 2 3 148 1 2 150 2 8 152 6 1 3) 154 1 15 3 1 2 5 11 156 3 4 ee SEAGRASS OSTRACODES: CRONIN ET AL. 185 Appendix 1b.—Extended Continued. Paracy- Peratocy- Paracy- theroma_ Peratocy- theridea Radimella Reticulo- Triangulo- Xesto- theroma stephen- theridea_ setipunc- Proponto- Proteo- Puriana_ confra- cythereis — cypris leberis — ?Micro- Total repexa soni bradti tata cypris — concha spp. gosa _floridana laeva spp. cythere Ostracodes 1 1 4 1 1 3 3 4 2) 6 1 10 2 4 2 6 1 2 13 2) 6 1 2 2 17 2 6 2 i 1 DZ 6 28 2 2 2 3 13 2 1 12 2 2 1 32 2 18 1 3 3 50 1 1 7 1 1 2 N7/ 3 1 10 6 1 3} 13 4 2 4 20 8 1 1 3 25 2 2 18 2 1 7 8 78 1 3 1 5) 4 21 186 BULLETIN 361 Appendix 1c.—Ostracode species census data, Manatee Bay core MB-1. Actino- Acuti- Cythero- cythereis cythereis Cytheri- morpha Depth sub- laevis- Candona Cyther- Cytherel- della Cytherura Cytherura — paracas- (cm) — quadrata sima Bairdrids annae Cytherid ellid loidea alosa spp. forulata tanea l 1 8 22 3 12 16 5 1 5) 16 7 l 1 15 9 8 16 11 e} 7] 3 13 2 4 15 15 2 25 1 Wii | 1 3 2 21 19 1 4 28 21 1 6 17 23 3 4 25 1 1 i 11 27 1 1 1 2 7 9 5 29 1 4 2 2 1 4 5 1 31 2 1 5 8 5 3 3 2 33 1 1 5) 1 5 5 3 4 35 5) 3 5) 1 5 4 4 5 5 3h 2 1 7 2 3 6 2 1 4 39 4 1 6 3 1 1 5) 41 7 4 5 l 2 4 6 1 3 43 2 6 2: 3 2 2 1 5 45 1 2 2 4 7 5 47 4 4 4 4 5 2 2 49 4 1 6 1 1 | 4 1 2 Sil 2 1 17 1 3 3 i 10 53 12 9 4 4 35 4 1 8 4 5 57 5 1 16 7 6 6 59 6 6 2 8 2 2 61 4 3 6 2 63 5 4 3 3 65 1 1 2 1 2 1 1 67 5 1 2 2 69 1 71 2 2 1 2 1 73 2 1 1 75 6 2 1 2 1 77 5 2 1 1 79 3 3 81 5 I | 83 3 ] 3 85 3 2 87 2) 1 7 89 3} 1 91 5) 1 93 2 1 8 1 95 2 4 1 1 97 1 12 11 99 2 2 101 1 5) 103 4 7 8 1 105 1 107 1 109 111 113 30 22 115 1 15 11 117 1 21 24 SEAGRASS OSTRACODES: CRONIN ET AL. 187 Appendix 1c.—Extended. Perato- Loxo- cythe- Cythero- — concha ridea Reticulo- Triangulo- Xesto- morpha matagor- — Malzella Mega- Paracy- setipunc- cythereis = Puriana Thalloso- cypris leberis Total sp. densis floridana cythere theridea tata floridana convoluta cypris? sp. spp. Ostracodes 15S 31 ] 16 36 1 17 148 17 20 2 14 32 13 126 12 11 3 1 15 30 6 9 109 23 23 ] 7 26 6 17 120 19 21 1 8 9 2 22 106 19 21 1 2 7 15 6 1 20 124 11 Ail 1 1 9 10 1 4 3 18 100 19 17 5 ] 13 9 3 2 10 107 15 20 2 12 14 6 | 11 109 17 PL] 2 ] 14 10 1 5 1 10 121 19 28 4 10 1 1 6 6 8 107 18 12 1 2 13 27 80 14 30 5 6 9 2 4 2 IN7/ 109 15 22 3 10 3 l 5 13 98 30 28 8 1 3 5 12 i 26 134 1 19 20 2 4 5 8 17 3 28 131 1 19 Di, 1 1 1 1 3 15 9 Ds) 128 22 32 3 3 2 4 2 3 3 26 137 18 28 2 3 5 4 2 5 8 20 123 1 20 37 2. 4 2 3 10 6 11 28 145 2 23 26 1 6 4 3 4 4 6 23 135 3 26 28 1 3 p) 7 14 41 148 3 7 38 6 1 2 8 7 5 45 148 2 15 39 2 5 1 3 5 8 8 37 150 3 24 20 1 3 3 4 12 5 26 122 3 25 15 1 1 3 2) 3 4 21 116 22 56 10 20 2; 4 31 175 1 19 31 4 1 1 8 4 2 29 122 1 19 31 3 1 6 5 8 3 30 148 1 14 54 2 2 1 6 3 5) 3 25 142 2 16 52 1 5 10 1 4 3 23 132 10 42 5 5 2 2 22 103 7 18 1 3 2 5 38 84 14 44 2 1 6 1 2 7 19 106 3 15 1 3 1 12 36 i 69 Z 1 10 16 4 i 6 5 129 4 41 2 24 14 1 2 3 95 5) 93 2 10 11 2 1 18 154 3 101 3 B 19 1 13 152 5 81 2 8 19 2 12 135 4 71 2) 5 10 12 111 3 92 3 5 7 2 1 12 132 2 83 1 6 13 11 121 4 90 2 9 12 6 133 2 90 7 12 1 116 B 88 1 16 16 7 137 74 4 14 5 104 81 1 4 13 10 117 1 48 2 10 17 1 5 108 18 3 3 28 1 32 7 5 1 52 56 12 19 3 110 14 3 3 1 22 3 3 1 8 0 0) 17 5 2 3 79 2 51 1 18 11 1 111 2 46 1 19 10 3 127 188 Apppendix 1d.—Park Key core Ostracode census data. BULLETIN 361 Depth Year 1 1995 3 1992 5 1990 7 1987 9 1984 11 1982 13 1979 15 1977 17 1974 19 1972 21 1969 23 1967 25 1964 27 1961 29 1959 31 1956 33 1954 35 1951 37 1949 39 1946 4] 1943 43 1941 45 1938 47 1936 49 1933 51 1931 53 1928 55 1925 57 1923 59 1920 61 1918 63 1915 65 1913 67 1910 69 1908 71 1905 73 1902 75 1900 77 1897 79 1895 81 1892 83 1890 85 1887 P. setipunctata Loxoconcha 5 18 9 16 11 14 ms Monn pf f wo 85 84 83 70 79 72 65 76 69 Malzella 140 111 155 143 128 127 115 140 88 Sil Xestoleberis 15 26 9 14 12 17 15S 13 Ww SS SS Ss SSS) NWN CO ere fw f Se NW eRe NWre fAIYW Ore lo} Ww Total ostracodes Appendix le.—Ostracode species census data, Russell Bank core 19-B. Depth Year 1995 1993 1992 1990 1988 1987 1985 1984 1982 1980 1979 LOTT 1975 1974 1972 1970 1969 1967 1965 1964 1962 1961 1959 1957 1956 1954 1952 1951 1949 1947 1946 1944 1943 1941 1939 1938 1936 1934 1933 1931 1929 1928 1926 1924 1923 1921 1920 1918 1916 1915 1913 1911 1910 1908 1906 1905 1903 1902 Actino- cyther- cyther- Acuti- eis cf. eis Aglaio- Aurila subqua- laevis- cypris laevi- drata — sima sp. cula 2 2 1 1 1 2 1 1 2 1 1 1 2 1 2 3} 2 1 1 1 1 1 1 1 1 2 2 1 3 2 1 3 3 2 1 1 1 1 3 2 3 5 6 2 2 1 3 2 3 1 2 7 6 3 10 5 9 5 7 2 1 2 9 1 8 6 4 q 3 4 5 1 2 5 2 8 6 3 2 2 2 3 1 2 4 2 3 3 1 3 a 2 1 1 1 4 5 3 SEAGRASS OSTRACODES: CRONIN ET AL. 189 Cythero- Cyther- Cyther- Loxo- Bytho- Cythe- morpha ura’ Cyther- ura Hemi- Lepto- concha _ Loxo- cy- rel- para- elon- ura sablen- cyther- cythere matagor- concha therid loidea castanea_ gata __ fiscina Sis ura sp. densis spp- 2 2 2 3 14 1 2 6 3 18 1 2 1 5 1 15 4 2 3 10 a 2 1 1 4 16 1 1 1 1 1 12 5 7) 1 14 3 3 4 2 2 35 4 1 Z 1 22 3 1 19 1 2 9 1 2 1 1 16 4 I 19 1 3} 1 1 1 28 3 4 1 5 15 2 4 1 1 2 22 2 3} 1 30 1 4 2 3} 3 22 2 4 2 3 9 3 1 5 1 17 2 4 3 1 12 4 6 5 3 25 5 5 5 14 5 4 2 22 4 9 4 18 3 6 9 28 1 4 1 3 1 3 24 2 2 2 1 35 1 4 4 1 30 7 1 3 29 4 1 2 15 7 5 3 2 1 27 1 2 9 1 1 25 1 9 4 4 14 1 2 10 4 2 2 18 3 4 1 12 1 1 2 6 1 13 1 1 1 1 2 7 2 1 2 4 1 1 1 2 1 7 1 2 1 2 2 8 1 4 2} 9 1 1 5 3 3 7 2 1 12 1 2 2 1 1 5 1 1 3 3) 1 1 5 1 1 2 3 1 8 1 1 3 1 2 6 1 3 1 3 2 1 4 3 1 3} 2 11 5 1 3) 1 9 5 1 2 11 2 6 1 10 2 2 1 6 1 1 8 5) 1 13 1 Z 4 2 2 e) 3 4 4 1 1 2 5 1 1 4 190, Appendix le.—Continued. Depth Year 100 102 104 106 108 110 112 114 1995 1993 1992 1990 1988 1987 1985 1984 1982 1980 1979 1977 1975 1974 1972 1970 1969 1967 1965 1964 1962 1961 1959 1957 1956 1954 1952 1951 1949 1947 1946 1944 1943 194] 1939 1938 1936 1934 1933 193] 1929 1928 1926 1924 1923 1921 1920 1918 1916 1915 1913 1911 1910 1908 1906 1905 1903 1902 BULLETIN 361 Perato- Neo- Para- Para- cythe- Reticu- Mai- caud- cyther- Para- cythe- Perato- ridea Radi- locyth- Tri- zella ?Mi- ites idea cythe- roma cythe- _ seti- Puri- mella_ ereis angulo- Xesto- flori- cro- triplis- Neone- tschop- roma steph- ridea_ punc- Proteo- ana con-_ flori- cypris leberis dana cythere triatus sidea pi repexa ensoni bradyi tata concha spp. fragosa dana laeva _ spp. 25 1 3 1 2 40 32 1 2 3 1 1 4 1 23 39 1 3 3 35 36 2 1 1 1 1 39 39 4 1 1 1 2 32 37 1 3 1 2 1 41 35 6 l 2 3 1 32 17 3 4 1 1 1 36 45 1 1 2 2 2 2 1 1 28 39 1 1 1 1 41 52 2 2 1 1 2 1 1 26 46 3 2 3 2 23 1 1 1 5 1 1 2 2 2 3 30 21 3 4 1 2 2 28 39 1 3 1 1 2 1 21 35 3 R) 3 1 6 4 2 2 15 39 2 6 1 7 2 1 1 12 36 2 4 i 4 1 2 1 1 16 46 1 1 1 1 2 1 2, 22 57 4 3 5 1 4 1 1 17 38 2 1 2 3 1 8 1 1 2 27 16 5 5 5 1 36 19 3 4 1 5 1 1 1 42 16 1 2 2: 9 2 4 36 25 1 5) 2 4 7 4 1 2 23 11 1 2 6 2 2 1 47 14 2 2 15 1 1 26 13 8 4 9 3 2 32 29 3 2 12 4 1 1 27 11 6 10 5 2 1 7 14 33 3 2 13 6 2 1 1 10 il7/ 23 1 2 2 14 7 ] 3 5 36 34 5 ] 1 11 v7 2 RS) 1 8 17 31 3 2 1 4 8 1 6 2 W 4 16 28 2 1 3 4 5) 2 4 2 4 13 46 2 2 3 9 4 11 4 4 4 3i7/ 1 2 3 5 2 9 3 10 1 5 10 42 2 5 ib) 2 8 1 3 5 5 51 1 2 1 3 23 2. 6 3 3) 3 42 1 23 3 8 1 3 6 9 40 2 1 4 2 2 12 3 10 5 2 4 44 1 3 2 13 3 6 1 3 4 9 43 4 2 6 2 5 2 2} 43 ] 1 3 2 1 15 4 3 4 5 9 35 8 2 15 2 10 1 1 3 10 32 1 5 i 19 3 1 5 8 30 1 2 1 4 11 2 6 4 4 14 47 1 5 3 6 6 3 9 3)5) 2 9 1 16 2 4 1 4 4 16 45 5 15 2 2 7 42 1 5 14 3 6 1 14 42 1 3 17 2 6 1 2 1 10 51 1 1 4 2 1 10 2: 6 5 1 21 42 1 1 2 1 10 5 4 3 1 14 31 6 1 1 5 3 10 1 2 17 31 2 4 2 3 14 1 6 1 3 9 33 1 3 1 18 3 3 4 6 9 28 3 1 21 1 1 4 Other Total SS 98 106 104 109 104 103 114 116 110 100 104 100 103 99 1 11S 108 106 99 122 112 114 109 105 112 121 98 113 121 97 115 147 137 120 112 113 122 109 124 123 112 118 92 124 106 96 1 103 105 114 99 109 110 132 103 115 2 102 1 107 73 SEAGRASS OSTRACODES: CRONIN ET AL. 19] Appendix le.—Continued. Actino- Acuti- cyther- cyther- Cythero- Cyther- Cyther- Loxo- eis cf. eis Aglaio- Aurila Bytho- Cythe- morpha ura Cyther- ura — Hemi- Lepto- concha_ Loxo- subqua- laevis- cypris laevi- cy- rel- para- elon- ura sablen- cyther- cythere matagor- concha Depth Year drata — sima sp. cula_ therid loidea castanea_ gata __ fiscina sis ura sp- densis spp. 116 1900 2 1 ] | 118 1898 2 2 1 1 3 il 2 12 1 120 1897 3 1 2 1 3 122 1895 4 3} I 6 124 1893 4 6 1 1 7 126 1892 2 2 1 1 3 1 1 1 128 1890 7 4 1 1 1 4 1 130 1888 3 1 2 1 1 3 5 132 1887 3 3 | 2 3 ] 134 1885 1 2 1 1 2 1 1 4 136 1883 1 6 1 6 2 1 2 9 1 138 1882 6 2 1 4 2 1 13 140 1880 5 5 1 i 2 2 1 142 1879 2 14 1 1 2 2 1 13 Appendix 1f.—Ostracode species census data, Taylor Core T-24. Acuti- Cypri- Cythero- Cytherura cythereis dopsis | morpha cf. Dolero- Hetero- Lepto- — Limno- Depth /aevis- Cypris Cyprideis okee-_ paracas- Cytherura’ reticu- — cypria cypris _cythere — cythere (cm) sima Candona Cypretta sp. salebrosa chobei tanea — sandbergi lata sp- punctata sp. floridana 10) 1 a 16 1 3 11 1 2 1 14 Z 17 4 1 9 1 23 1 6 3 11 2 12 1 1 8 1 1 11 1 8 18 2 1 10 1 2 22 1 2 12 1 3 12 2 2 5) 251 1 4 18 1 1 1 1 14 2 15 1 8 16 2 122 1 9 i 1 18 2 8) 1 4 1 20 1 9 1 3 1 22 11 1 3 1 2 2 24 1 10 1 2 26 4 26 3 1 28 3 6 2 1 30 1 1S 4 2 1 32 1 11 2 W 2 1 34 1 1 15 3 1 1 1 36 3 11 1 3 1 1 38 1 12 2 40 2 13 1 1 2 42 2 10 2 1 5 44 2 14 2 1 46 8 1 1 48 1 5 1 1 1 2 50 2 7 1 1 ny) 1 1 9 3 6 54 1 9 2 4 2 2 56 1 7 2 8 1 3 58 3 11 3 5 2 1 192 BULLETIN 361 Appendix le.—Extended. Neo- Para- Para- Perato- Reticu- caud- cyther- Para- cythe- Perato- cythe- Radi- locyth- Triang- Maizella ?Mi- _ ites idea cythe- roma cythe- ridea mella ereis ulo- Xesto- flori- cro- triplis- Neone-tschop- roma steph- ridea _ seti- Proteo- Puriana con-_ flori- cypris leberis dana_cythere triatus sidea pi repexa ensoni bradyi punctataconcha spp. fragosa dana _ laeva spp. Other Total 12 1 1 2 1 3 2 1 2 30 24 1 1 2 1 13 5 2 5 3 13 1 96 20 2 6 1 5 3 1 4 1 53 20 1 2 1 1 7 1 1 7 1 63 39 2 2, 4 8 2 3 95 39 1 1 1 3 YU 2 1 Z 1 10 86 34 1 1 3 4 10 3 11 ©) 2 7 104 48 1 1 4 1 1 15 4 6 1 1 8 107 46 1 1 11 1 8 2 14 97 49 1 1 8 1 6 1 8 88 35 1 1 2 1 13 4 2 6 14 108 35 4 2 d 1 6 2 2 6 94 Bi, 2 3 4 6 6 D 5 7 89 35 4 6 2 4 1 1 8 18 115 Appendix 1f.—Extended. Para- Loxo- Para- cythero- Peratocy- Perisso- Perisso- concha Parapon- cythero- ma theridea cytheridea cytheridea Reticulo- Xesto- matagor- Malzella _ toparta ma stephen- seti- brachy- cf. cythereis Thalasso- leberis Total densis __floridana sp. repexa soni punctata forma cribrosa_ floridana_ cypria spp. Other Ostracodes 19 48 2 1 28 4 1 10 148 18 48 38 5 2 7 152 24 50 2 ] 5 47 3 1 1 9 3 181 24 42 3 50 7 2 7 165 27 59 3 1 68 7 2 3 13 226 23 1S 1 1 3 74 8 2 5) 236 24 103 2 3 1 1 135 10 3 13 358 16 41 1 54 16 1 4 1 160 10 65 1 1 1 Wil 4 1 6 2 188 10 21 1 44 10 1 104 11 Sil 1 53 8 119 10 43 3 713 5 1 3 1 159 4 28 2 43 2 2 95 5 13 45 11 1 1 110 5 21 59 4 101 9 21 2. 42 7 3 107 5 20 2 54 1 2 108 5 21 1 2 3h7/ 6 3 1 1 100 10 23) 1 2 33) 8 3 100 5 20 3 1 54 2 3 103 14 24 1 3 32 3 1 1 98 1] 22 1 1 39 3 1 4 102 9 Sif 33 5 1 5 103 12 31 2 2 36 2 2 2 5 1 105 17 Dill 4 4 1 35 2 5 106 6 38 3} 3 1 32 3 5 102 11 40 1 1 1 29 3 5 111 12 Sil 2 36 6 1 2 110 6 19 1 45 22 2 3 100 7 19 2 2 51 3 2D) 111 SEAGRASS OSTRACODES: CRONIN ET AL. Appendix 1g.—Whipray Key Ostracode census data. Xesto- Total Depth P. seti-Loxo- leberis ostra- (cm) Year = punctata concha Malzella _ spp. codes 1 1995 11 8 6 11 57 5 1985 9 8 24 37 107 ®) 1976 0) 19 28 9 99 13 1967 2 10 31 23 95 17 1957 7 9 32 15 115 21 1948 6 10 27 14 109 25 1939 11 9 28 8 102 29 1930 29 9 22 5 101 33 1920 29 7 45 2 145 37 1911 PH] 5 32 3 100 41 1902 14 6 58 0) 97 45 1892 10 20 32 8 98 49 1883 12 3 17 8 52 53 1874 43 2 23 0) 81 S7/ 1864 34 3 6 2 56 61 1855 40 3 13 2 85 65 1846 Tih 10 21 1 127 69 1837 61 2 43 1 146 73 1827 40 2 31 1 108 77 1818 2 17 49 4 125 78) 1813 21 7 29 2 91 194 Appendix 2.—Ostracode species occurrence on Florida Bay seagrasses and marine algae. BULLETIN 361 Acuti- Loxo- cythe- Cythe- Cy- Hemi- concha Actino- Aglaio- reis Aurila Cythe- Cythe- rura _ thero- cythe- mata- Loxo- Sample ID Sub- cythe- cypris laevis- laevi- Bair- — rura rura — sand- morpha Cypri- Cythe- rura gor- concha ID number strate _reis sp. simacula_ diids_ cybaea fiscina bergi sp. deis reliids sp. densis sp. FB1 1 G 1 2 4 6 3 oy) FBI 4 G 4 1 2 3 21 FB1 5 G 2 3 5 1 2 29 FB11 1 G 1 2 1 2 i 17 1 FBI 2 A 1 3} 1 1 18 PBS 3 G 2 1 1 ralesill 3) G 1 7) g 2. 10 2 21 FB12 1 A 1 BRI 2 A 1 1 28 3 FBI2, 3 G 2 4 6 3 2 8 1 FBI2 4 G 1 2 FBI2 5 G 1 4 17 1 11 FBI4 1 G 1 3 4 2 35 FBI6 1 G 100 1 FB16 2 A 1 57 FBI6 3 A 1 70 FB17 1 G 1 1 2 7 laesily 2 A 1 50 5 2 3 2 18 BB A 1 17 1 40 FBS, 2 A 11 2 1 1 20 FB20 1 G 2 1 3) 15 FB20 2 G 1 1 5) | FB20 3 A 2 FB20 4 A | ] FB20 5 A 5 BB2I G 2 2 1 42 2 FB21 shell S 2 2 a 4 22 12 FB22 1 G 2 1 1 1 1 26 2 BB23 G 2 1 FB26) 1 G 5 1 1 oy) 1 FB26 2 G 9 FB4 4 G 1 1 1 2 3} 2 16 FBS 1 A 1 1 2 9 FB5 2 A 1 l 3 3 2 4 24 FB5 3 A 4 FB5 5 A 1 6 2 1 | 29 FB6 shell S 3 1 4 29 4 1 FB8 1 G 1 l 18 3 Total for 36 veg samples 15 17 1 12 85 35 29 16 56 7 30 5 808 14 % for 36 veg samples 0.564 0.64 0.038 0.451 3.198 1.317 1.091 0.602 2.107 0.263 1.129 0.188 304 0.527 Total for 2 sand samples 5 0 3 0 4 10) 7 0) 10) 33 0) 0 26 13 % for 2 sand samples 2.092 0) 1-255 10) 1.674 10) 2.929 (0) O 13.81 0 0) 10.88 5.439 Total for 15 algal samples 3 4 0) 12 74 14 9 0 6 0) 13 3 325) 3 % algal samples 0.281 0.375 0 1.126 6.942 1.313 0.844 0 0.563 0) 1.22 0.281 30.49 0.281 Total for 21 Grass samples 1 13 1 10) 11 21 20 16 50 W 17 2 483 11 % Grass samples 0.754 0.817 0.063 0) 0.691 1.319 1.256 1.005 3.141 0.44 1.068 0.126 30.34 0.691 * Perissocytheridea troglodyta and P. rugata. ** Some Triangulocypris, Thalassocypris, indeterminate taxa. # Includes Puriana, Leptocythere, Caudites. Mal- zella flori- dana 23 92 24 38 — WwW pond ONnNK DANK ODN WW — - aornnNneHe D~ i) Appendix 2.—Extended. SEAGRASS OSTRACODES: CRONIN ET AL. Perato- Para-_ cythe- Megacy- cythe- ridea_ Perato- there roma seti- cythe- Peris- Reticu- John-— steph-— punc- _ ridea_ socythe- locythe- soni ensoni tata bradyi ridea* reis 2 3 2 | 4 9 2 1 i 1 1 l 15 1 1 12 2 2 2 9 4 1 11 25 3 1 1 10 2 2 ] 2 1 2 2 1 1 l 1 1 4 47 1 1 1 1 1 1 1 2, 2 1 3 3 3 2 2 2 69 1 2 1 9 21 21 91 8 Pei} 13 0.79 0.79 3.424 0.301 1.016 0.489 4 0 116 1 0 3 1.674 0) 48.54 0.418 (0) 1.255 8 2 9 5 2 1 0.75 0.188 0.844 0.469 0.188 0.094 13 19 82 3 25 12 0.817 1.193 S25 OMS8 1257 0.754 Thal- asso. & Tri- ang.** 1 1 1 i) i) 14 0.879 Xesto- leberis Spp- 19 11 13 11 32 Other # BWNAD Ne i) Total 118 151 92 112 65 31 2658 Vegetation Laurencia, Thalassia Thalassia, Halodule, Laurencia Thalassia, Polysiphonia, Laurencia Thalassia, Polysiphonia Chondria, Thalassia Halodule, Thalassia Thalassia, Chondria, Polysiphonia Sargassum Chondria, Polysiphonia, Laurencia, Thalassia Thalassia Halodule Thalassia Ruppia, Halodule, Thalassia, Laurencia Thalassia, Laurencia, Batophora Laurencia, Batophora, Thalassia Polysiphonia, Batophora, Thalassia, Halodule Thalassia, Chondria Chondria, Thalassia Chondria, Polysiphonia, Thalassia, Halodule, Laurencia Syringodinium Thalassia, Polysiphonia Halodule Chondria, Polysiphonia, Thalassia Chondria, Batophora, Thalassia Polysiphonia Thalassia, Halodule, Laurencia shell Thalassia, Laurencia Syringodium, Thalassia, Chondria, feathery algae Halodule, tulip-like algae, Thalassia, Laurencia, Chondria Halodule, Thalassia Thalassia, Sargassum, Polysiphonia Siphonia, Batophora, Chondria (2 species), Thalassia, Laurencia, Halodule Laurencia, Acetabularia, Enteromorpha, Halodule, Batophora Laurencia, Chondria, filamentous green algae Laurencia, green mossy filamentous algae, Batophora, Chondria, Halodule, Thalassia shell Thalassia 196 BULLETIN 361 Appendix 3—Modern ostracode data for 1995. Cy- Actino- thero- cythe- mor- Cy- reis Proteo- pha _ ther- Cy- sub- Acuti concha para- ura ther- Dolero- quad- laevis- Aglaie- Caud- tuber- Cypri- Cythrel- cas- elon- Cyther- ura cypria Slide Location rata sima cypris ites culata deis Cypris loidea tanea gata ura sp. fiscina _ sp. 95GLW 16 Bob Allen Keys 1 1 q 1 95GLW 17 Bob Allen Keys 3 2 95SGLW18A Shell Creek—mouth 1 3 ®) 95GLW18B Shell Creek—mouth 4 1 2 2 3 2 9S5SGLWI19A Trout Creek—mouth 9 4 0 Wf 1 95GLW 19B Trout Creek—mouth 2 5 4 95GLW20A Duck Key 1 1 6 1 5 95GLW20B Duck Key 1 3 ; 1 + 1 7 1 95GLW21 Nest Key 5 1 2 3 11 9 3 1 95GLW22A Porjoe Key 1 1 1 1 3 1 95GLW22B Porjoe Key 1 3 2 5 3 95SGLW22C Porjoe Key 1 4 8 4 1 4 9S5GLW22D Porjoe Key 1 4 2 i 2 9SGLW23 Butternut Key 2 1 11 6 1 il 0 Bob Allen Keys 0.95 0 (0) 10) 0.95 0 (0) 0.95 0 0) OPS 0) 10) Bob Allen Keys 3516, 0 2-117 10 0 0 0 (0) 231 nO) 0 0 0 Shell Creek—mouth (0) (0) 0 (0) 10) 0 10) 1.01 0 3.03 0 9.09 0 Shell Creek—mouth (0) 10) 0 0 0 4.3 1.08 (0) 0 2.15 AMsy 3728} ZS Trout Creek—mouth 10) 0) 0) 0 0) 9 (0) 0 4 10) 10) 7 1 Trout Creek—mouth 0 (0) 0 10) (0) (0) (0) 0) 6.67 0 16.7 10) ils\33) Duck Key 1 0 0 1 (0) 6 10) 0 1 5 (0) 10) 0) Duck Key 12037 33:09. 2:06; 0 1.03 O 0 avid 0} 7/2? 1.03 0 0) Nest Key 4.5 0.9 1.8 0) Do 0 0) GO| fill We 0) 0 0.9 Porjoe Key 12 Dien De 10 0 1-22 10 0) 122 nO) 3.66 0 1.22 0 Porjoe Key 0 0) 0.96 0 0 0 (0) 2.88 1.92 4.81 10) 2.88 0 Porjoe Key 0.89 O (0) 0 (0) 0 (0) BS Gaia) BNe537/ 0.89 3.57 0 Porjoe Key 101 0 0 0) 0 0 0 4.04 2.02 7.07 (0) 0 2.02 Butternut Key 3.28 1.64 0O (0) 18 9.84 0 (0) 0 1.64 1.64 0 0 Bottle Key 122") 10:49" 0!5 0.07 1.71 2.08 0.08 1.98 2.8 2.92 167, E93 139) SEAGRASS OSTRACODES: CRONIN ET AL. 197 Appendix 3—Extended. Para- Perato- Peris- cy- cy- SO- Loxo- Para-_ thero- theri- Perisso- cythe- Limno- concha Mal- cy- ma Para- Perato- dea cythe- ridea Reti- Trian- cythere mata- zella Neo- thero- Ste- cy- cythe- seti- Perisso- ridea cf. cula gulo- Xesto- flori-— gor- flori- nesidea ma_ phen- the- ridea punc- cythe- brachy- cri- Puri- flori- Thal. cypris leberis dana densis dana sp. repexa soni ridea bradii tata ridea forma brosa ana dana vavrai laeva_ spp. Total 13 27 6 l 2 1 1 4 46 105 11 32 2 3 1 3 6 8 IF) 95 12 49 1 2 3 4 15 99 14 44 1 5 3 12 93 1 8 28 1 25 4 5 V 100 18 1 30 8 30 3 2 2 30 1 10 100 21 26 a) 1 4 4 5 1 1 12 97 22 20 3 2 5 1 | 19 111 36 16 1 2 2 1 16 82 22 32, 4 1 3 1 1 26 104 24 19 1 3 5 1 6 3 18 112 25 13 2 1 4 1 3 34 99 2 12 2 4 1 1 17 61 (0) 12742557 S271 0.95 129) 0:95 0 0 0 0 0 0.95 0 3.81 0 43.8 100 0 6S 3357, 10 2.11 10) 0 0) 3:16, 10 EOS 0) 3.16 632 842 0 17.9 100 (0) 12a 495 0 0) 1.01 0 0 (0) 10) 2102 3103; 10 0) 4.04 0O 15.2 100 (0) 15.1 473 O 108 0O (0) (0) (0) 0 5.38) 3123) 10 0) 0 0 12.9 100 1 8 2 (0) 1 10) 10) 10) 0) 10) 25 4 0 10) 5 (0) 76 ~=100 0 60 10) (0) 0) 10) 0 0) (0) (0) 0 (0) 0 3333770 (0) 0 100 (0) 8 30 3 0 2 0 0 2 30 10) 0 0 0) 1 0 10 100 0 DG 26:8 92:06) 50 N03) 4212) 451210 10) 10) Splisy 1.03 12035) 10 12.4 100 0 19.8 18 2.7 1.8 4.5 (0) (0) 0 0 10) 0 (0) 0.9 3.6 (0) 17.1 100 0 43.9 19.5 PP (0) 0) 0 (0) 244 O 10) (0) 244 O 12250) 19.5. 100 10) PIP) Shey Ifo) (0) 0.96 0 10) 2.88 0 10) 10) 0 0.96 0 0.96 25 100 10) 2A 2529" 10:89)" 2168" 4:46) 10. Ol89F 5:36) 70 0 10) 0 (0) 2.68 O 16.1 100 0 25.3 13.1 0 2.02 1.01 0 0 4.04 0O 10) 0 1.01 3:03' 0 0 34.3 100 10) 3.28 Ie @) 3.28 O 10) (0) 6.56 0 10) 10) 164 O 164 O 27.9 100 0.07 20135 26:3 1.39 1.07 1.21 0.36 0.36 1:89 2.14 2:39 1.1 0.66 1.11 2.32 0.07 18.5 CHAPTER 10 MOLLUSCAN FAUNAL DISTRIBUTION IN FLORIDA BAY, PAST AND PRESENT: AN INTEGRATION OF DOWN-CORE AND MODERN DATA G. LYNN BREWSTER-WINGARD!, JEFFERY R. STONE!, AND CHARLES W. HOLMES? 'U. S. Geological Survey, 926A National Center, Reston, Virginia 20192 2U. S. Geological Survey, 600 4" St., St. Petersburg, Florida 347011 ABSTRACT Statistical comparison of modern molluscan fauna to down-core molluscan assemblages in four cores elucidates changes in the Florida Bay ecosystem during the past 100 to 200 years. Fluctuations within molluscan faunal dominance and diversity patterns suggest a response to changing environmental conditions. Faunal dominance patterns indicate an increase in salinity in the northern transitional zone, and possibly the eastern portion of Florida Bay. Distinctive faunal shifts recorded at Russell Bank occur approximately between 1913 and 1933 and at Bob Allen mudbank between approximately 1900 and 1910. The period from approximately 1930 to 1980 within these cores shows rapid and dramatic fluctuations in species dominance and faunal richness. Beginning around 1980, the mussel Brachidontes exustus, which can tolerate diminished water quality and a wide range of salinities, increases in percent abundance in the upper portion of all four cores and becomes the dominant species at Russell Bank and Bob Allen Mudbank. While these fluctuations within assemblages are distinctive, they are not so profound that they represent a major shift in estuarine zonations within northern, eastern, and central Florida Bay during the past 100 to 200 years. The majority of the molluscan fauna that are present at the core sites today are generally present throughout the period of deposition. Fluctuations in the molluscan faunal record down-core primarily express changes in dominance and diversity within assemblages and do not reflect substantial changes in overall assemblages. It is these fluctuations in dominance and the appearance or disappearance of critical indicator species that are indicative of salinity changes. Understanding the dynamics of an ecosystem and the natural range of variation in the system over an extended period of time is a critical component of effective restoration. Analysis of the modern environment provides a means to interpret biological data preserved in cores, and to determine the physical and chemical variations in the environment indicated by the biota. Knowledge of the past provides the best insight to predicting the impact of future change on the environment. INTRODUCTION Molluscs are an abundant and diverse component of the shallow coastal ecosystems of Florida. Two hun- dred and twenty-one families, 646 genera, and 1407 species of molluscs have been documented from the shallow marine environments of the state (Camp, Ly- ons, and Perkins, 1998). In Florida Bay alone, 235 species of molluscs were recorded by Lyons (1999) over the course of a three-year sampling period (1994— 1996). This diversity can be attributed in part to south- ern Florida’s position at the junction of two molluscan faunal provinces: the Caribbean and the Carolinian. Molluscs are an integral part of the Florida Bay eco- system. Different groups of molluscs are components of the micro-, meio-, and macro-fauna of the bay and as some species pass through their life stages they move from the plankton to the benthos. In addition, molluscs employ a number of feeding strategies, in- cluding filter feeding, grazing, scavenging, and carniv- ory. Consequently, molluscs occupy a number of tro- phic levels within the ecosystem and they fill many important niches as both predators and prey. Analyzing historical patterns of change in molluscan assemblages is a very powerful tool in reconstructing the history of an ecosystem. Estuarine molluscs tolerate a wide range of fluctuating environmental conditions, yet on a scale of seasons, their populations will migrate to more ideal conditions (Dame, 1996). Lyons (1996, 1998) has demonstrated molluscan migration within Florida Bay in response to seasonal and annual varia- tions in salinity. Individual molluscs, however, are rel- atively limited in their movement in post larval stages, and typically provide information about a specific site for the duration of their lifetime. In addition, most mol- luscs are hard-shelled, and therefore well preserved in cores. Turney and Perkins (1972) related the distribu- tion of molluscan death assemblages to environmental influences. On the basis of these previous studies, and given the ecological preferences of molluscs, we be- lieve changes in molluscan assemblages identify signif- icant perturbations of an environment and filter out “noise”? caused by day to day or short-term fluctua- tions, such as those caused by tropical storms. By un- derstanding the factors controlling modern distributions of molluscs, we can interpret patterns of change in the past, and in turn, predict future responses to human- induced or natural environmental change. 200 BULLETIN 81/00i PARK BOUNDARY 25 J 00i WATER DEPTH 10 Kilometers 81/00: 361 80) 30i Sab Allen 6A0c%> g 25 J 00i a S | + PISTON CORE SITES _ © MODERN SAMPLING SITES ATLANTIC OCEAN 80/30i Text-figure 1—Map of Florida Bay showing location of 26 monitoring sites and four cores. Boundary of Everglades National Park is shown by bold dashed line. Table 1 gives latitude and longitude. ACKNOWLEDGMENTS Our work has been done in collaboration with col- leagues at a number of other agencies, including South Florida Water Management District, National Oceanic and Atmospheric Administration, and Everglades Na- tional Park. We would like to thank them for their cooperation and assistance in this investigation. We would especially like to thank William Lyons, Florida Marine Research Institute, for his invaluable and gen- erous help with current molluscan taxonomy, and for the many long discussions on the ecology and biology of Florida Bay molluscs; we have benefited greatly from his contributions. None of this work would have been possible with out the assistance of William Gibbs and the staff at the Keys Marine Laboratory, our base of operations during fieldwork. We are indebted to our colleagues Robert Halley and Eugene Shinn, U.S. Geological Survey, St. Petersburg, FL, for collecting the cores and making them available to us for analysis, and to John Robbins (NOAA) for collaborating on the development of the age model for the cores. We would like to thank our reviewers Lucy Ed- wards, U. S. Geological Survey, Reston, VA and John Pojeta, U.S. Geological Survey and U.S. National Museum of Natural History, Washington, DC for their thoughtful reviews and suggestions to improve this manuscript. Thomas Scott, and G. Harley Means, Flor- ida Geological Survey, have provided assistance in the field. The following U.S. Geological Survey person- nel have assisted in field work and sample preparation: Kristi Alger, Jill D’ Ambrosio, Alessandro Bagalia (volunteer), Nancy Carlin, Carey Costello, Lauren Hewitt, Sara Schwede, and Steve Wandrei. Sara Schwede and Luke Blair, USGS, produced the GIS salinity maps. METHODS OF INVESTIGATION FIELD METHODS Twenty-six sites throughout Florida Bay (Text-fig. 1, Table 1), visited biannually between February 1995 and July 1999, constitute the source of modern obser- vations. Biannual observation of sites always occurred between February 12-23 and July 6—13 for seasonal consistency. Sites 1-14, under regular observation MOLLUSKS PAST AND PRESENT: BREWSTER-WINGARD ET AL. 201 Table 1.—Location of 26 modern sampling sites and 4 cores shown on Figure 1. Site Number Site Name Latitude Longitude 1 Shell creek mouth N 25.20684 W 80.48701 2 Trout Creek water monitoring station N 25.21226 W 80.53345 3 Duck Key water monitoring station N 25.18012 W 80.48916 4 Northern Nest Key N 25.13104 W 80.50458 5) Porjoe Key S mud bank N 25.14121 W 80.47267 6 Butternut Key water monitoring station N 25.08677 W 80.51915 7 Bottle Key SE mud bank N 25.06092 W 80.55918 8 Little Madeira Bay mouth N 25.17580 W 80.63166 9 Mid basin S of Little Madeira Bay N 25.13433 W 80.62146 10 Mid basin (between Park & Russell Key) N 25.08494 W 80.58954 11 Park Key SW bank N 25.10628 W 80.56254 12 Russell Key SE bank N 25.07168 W 80.63814 13 Bob Allen Keys mud bank N 25.01892 W 80.66540 14 Bob Allen Key water monitoring station N 25.02647 W 80.68115 15 Gopher Pass N 24.98098 W 80.73686 16 Mud bank SE of Sid Key & SW of Corinne N 25.01227 W 80.76410 17 Little Rabbit Key water monitoring station N 24.98144 W 80.82515 18 Peterson Key bank water monitoring station N 24.91783 W 80.74662 19 Mid basin N of Barnes Key N 24.95348 W 80.78270 20 Pass Key S mud bank N 25.15314 W 80.57711 21 Buttonwood Keys water monitoring station N 25.07101 W 80.73588 22 Whipray basin mud bank N 25.08853 W 80.74182 23 Sprigger Bank N 24.9132] W 80.93768 24 Schooner Bank N 24.9597] W 80.97596 25 Cape Sable N 25.11344 W 81.07898 26 Johnson Key water monitoring station N 25.05240 W 80.90391 Core Number Date Collected T24 Taylor Creek at mouth of Little Madeira Bay N 25.2000 W 80.6417 PK37 Pass Key - mud bank to south of Key N 25.1478 W 80.5745 5/26/96 RB19B Russell Bank to south of Russell Key N 25.0639 W 80.6248 2/24/95 BA6A Bob Allen mudbank, south east of Bob Allen Keys N 25.0232 W 80.6568 5/26/94 since February 1995, have been visited consistently twice a year. Sites 15-26, added to the observations after February 1995, were typically less accessible in the ‘wet’ season (May—October) and as a result un- derwent more regular observation during ‘dry’ seasons (November—April) and less consistent observation dur- ing ‘wet’ seasons. Observations were obtained by wading or snorkeling at each site and recording the substrate, fauna and flora present (living and dead), and microhabitats. Observation procedures did not in- clude digging within the sediment for infaunal organ- isms or a systematic search of the site, but represent a careful examination of the area. One hundred and sev- enty-five detailed site observations from February 1996 to July 1999 are analyzed statistically in this pa- per. Each observation was coupled with a characteriza- tion of the water at the site and a sampling of the sediment. Water was characterized by salinity, tem- perature, depth, and clarity. Salinity values were cal- culated using a Hydrolab Surveyor 4, YSI Model 30/ 10 FT, or a refractometer. Temperature values were obtained using a Hydrolab Surveyor 4 or YSI Model 30/10 FT. In February and July 1998, seventeen sub-aquatic vegetation samples (macro-benthic algae and seagrass) were collected at sites 8, 12, 13, and 20. Sub-aquatic vegetation was sampled randomly, to characterize the types of flora present, and the associated epifaunal or- ganisms. Sub-aquatic vegetation was collected without the roots or holdfasts (where present) to reduce the chance of contamination by infaunal organisms. Veg- etation samples were collected with a small amount of concomitant water in an attempt to delay the effects of biodegradation before laboratory examination of the samples. Sediment samples were collected using a 1.5 inch diameter PVC tube (push core). Push cores were pressed into the substrate, and a vacuum was main- tained to extract the sediment. Push core tubes were cut at the water-substrate interface and sealed to pre- vent disruption of sediment during transport to the lab- oratory. The twenty-eight push cores described in this study were taken from four sites in northern and east- 202 BULLETIN 361 ern Florida Bay (Text-fig. 1) biannually between Feb- ruary 1995 and July 1998 (collection at site 20 began February 1997), and represent a subset of the total number of push cores obtained. Push core samples were chosen for this study based upon proximity of modern sampling sites to the location of the four pis- ton cores. The four short piston cores (<2 m) examined were taken from Florida Bay localities (Text-fig. 1) between February 1994 and March 1996 by researchers from the U. S. Geological Survey (St. Petersburg, Florida), in cooperation with South Florida Water Management District, Everglades National Park, and National Oce- anic and Atmospheric Administration (NOAA). Mod- ern sites 12, 13, and 20 occur at the same location as piston cores RB19B, BA6A, and PK37, respectively. Site 8, located at the mouth of Little Madeira Bay, is the closest modern observation site to the site of piston core T-24, located at the mouth of Taylor Creek in Little Madeira Bay. LABORATORY METHODS Vegetation samples were characterized by type of sub-aquatic vegetation present and condition of the vegetation. All vegetation samples were then carefully examined for extant epifaunal organisms before pro- cessing. Samples were vigorously scrubbed to remove epifaunal organisms, washed through 850 «m and 63 um sieves, and dried at 50°C. Dry vegetation material from each sample was weighed, re-hydrated, and washed through 850 jm and 63 jm sieves a second time to help remove any remaining epifaunal organ- isms. All push cores were cut to 10 cm below the water- substrate interface, and this upper 10 cm of sediment was retained for processing. Twenty-eight push core samples were analyzed for faunal content. Piston cores collected for historical reconstruction were x-rayed and visually examined for signs of sediment disrup- tion, including bioturbation. Samples from the piston cores were submitted for *!°Pb analysis (see Holmes, et al., 2001, for method; Wingard eft al., 1995, and Brewster-Wingard et al., 1997 for 7!°Pb results on cores discussed here). All four piston cores were sam- pled at 2-cm intervals. All push core and piston core samples were washed through 850 wm and 63 pm sieves to remove carbonate mud. Samples were dried at 50°C. All recognizable molluscs and molluscan fragments were picked from the 850 m-size fraction from each vegetation, push core, and piston core sample. Picked specimens were sorted, identified, and characterized by condition of the shell material present. Specimens were characterized by stage (adult or juvenile) as well as pristine (intact and retaining original shell material), whole (intact but lacking original shell material or col- or), broken (retaining original shell material and more than 50% of shell), worn, or fragmented (retaining less than 50% of the shell but still recognizable at the ge- neric level). Age models for the piston cores 6A and 19B are based on ?!°Pb analysis of the <63 ,m-size fraction of the samples. For details of the method, see Holmes, et al. (this volume). ANALYTICAL METHODS Univariate and bivariate statistical analyses, includ- ing minimum, maximum, mean, median, and standard deviation, were conducted on environmental data (sa- linity and temperature), and individual species distri- butions using Microsoft Excel 97. For site observa- tions, the presence-absence data were simplified for statistical analysis by deleting samples with no mol- luscs present and removing faunal groups that occur less than two times throughout the dataset. Observa- tion data were translated into a presence-absence data matrix.'! For the piston core, push-core and vegetation data, absolute species abundances were standardized by calculating percent relative abundance of the total molluscan component of the sample. Worn and frag- mented molluscan specimens were removed from the analysis of vegetation samples, and from one run of push core samples, in order to isolate extant material from older material. All multivariate analyses were done using MVSP (Kovach Computing Services, MVSP Plus, version 3.1) following the methods described by Kovach (1989, 1995). A cluster analysis of the presence-ab- sence data was conducted using unweighted paired group method, average-linkage (UPGMA), with So- renson’s Coefficient distance measurement, dual clus- tering procedure, and random input order. Cluster anal- yses of percent abundance data were conducted with log-ratio transformed and centered data, then clustered using UPGMA, with cosine theta distance measure- ment, dual clustering procedure, and random input or- der. Each cluster analysis was run several times using random input order to determine robustness of clusters. Constancy and fidelity measures were calculated for each cluster in both the presence-absence data analysis and the percent abundance data analysis. Method was adapted from Hazel (1977). Constancy is a measure of how frequently a species occurs within a given cluster, expressed as a percentage. The formula is ' The full data matrix can be found at http://flaecohist/database/ Reference/synthesis. MOLLUSKS PAST AND PRESENT: BREWSTER-WINGARD ET AL. 203 Total Observations 20 10 60 35 Oe 040 e) Oo 30 es ° ciet e ry i> > be Sali dues oe = Y g B 5 A oO : oa A 5 asia “aa AA 20 : te 15 SSF = 0 5 10 15) 20 D> 30 35 40 45 Salinity (ppt) Text-figure 2.—Plot of temperature (°C) versus salinity (ppt) recorded at sites from February 1996 through July 1999. Histogram on x axis shows frequency of observations in 5 ppt increments. Histogram on y axis shows frequency of observations in 5°C increments. Bimodal nature of temperature readings reflects seasonality. Constancy = (Occurrence: 100) + Total number of samples in cluster. A species with 100% constancy is present in every sample in a given cluster. Fidelity is a measure of how unique a species is to a given cluster (expressed as a percentage). The formula is Fidelity = [(Constancy in Cluster X) + (> constancy values for all clusters) ]-100. Thus, it is possible for a species to have a high con- stancy value, if it is present in most samples in a clus- ter, but a low fidelity value if it also is commonly present in other clusters. Conversely, a species can be very rare and have a low constancy for a cluster, but a high fidelity because it occurs only in that cluster. A species with 100% fidelity is unique to that cluster. Several measures of diversity were calculated on all piston core samples: 1) total number of individual mol- luscan specimens; 2) faunal richness; 3) evenness; and 4) Shannon’s diversity index. Faunal richness in this study is a measure of the number of faunal groups present in a given sample (in the case of the presence- absence data observed at a given site). In some cases, the fauna are grouped into genera and occasionally broader categories (e.g., marginellids), so this is not “species”’ richness in the usual sense. Evenness and Shannon’s diversity index were calculated using MVSP. Evenness is a measure of how evenly dispersed the total number of individuals are among the faunal categories; the higher the value, the more evenly dis- persed the individuals are. Shannon’s diversity index (Shannon and Weaver, 1949; Ludwig and Reynolds, 1988) is a measure of the degree of uncertainty that a randomly selected individual will belong to a certain species. The formula is as follows: 204 BULLETIN 361 Table 2.—Univariate statistics for temperature (degrees C) at each site. All years (February and July) Mini- Maxi- Standard Site 2-96 7-96 2-97 7-97 2-98 7-98 2-99 7-99 mum mum Mean Median deviation 1 19.00 30.40 23.00 30.50 21.00 31.30 20.62 29.16 19.00 31.30 25.62 26.08 Bysil@) 2 19.70 30.80 23.70 31.40 22.00 31.47 20.41 28.80 19.70 31.47 26.04 26.25 5.10 3 17.20 31.40 23.80 32.80 21.40 32.00 20.45 29.18 17.20 32.80 26.03 26.49 6.04 4 19.80 31.20 24.60 32.70 21.60 32.88 21.46 29.61 19.80 32.88 26.73 ALT 5.46 5 16.50 31.60 25.50 32.90 21.90 33.42 22.09 30.37 16.50 33.42 26.79 27.94 6.22 19.70 29.60 24.40 32.40 21.00 33.29 21.68 30.49 19.70 33.29 26.57 27.00 5.48 33.59 27.09 27.95 5.95 19.20 31.30 24.70 31.60 20.00 30.86 19.96 29.52 19.20 31.60 25.89 27 ull S05) 17.90 31.00 24.10 30.40 19.40 Siig? 19.96 28.31 17.90 31.32 25.30 26.21 5.65 10 17.50 31.40 24.20 31.30 18.40 31.94 19.96 28.39 17.50 31.94 25.39 26.30 6.15 11 19.80 30.50 23.60 33.30 19.40 32.99 20.19 30.53 19.40 33.30 26.29 27.05 6.14 12 18.50 31.50 24.50 30.10 21.60 34.58 21.60 28.95 18.50 34.58 26.42 26.73 5.67 13 19.80 31.30 24.60 30.80 22.20 32.10 22.37 30.90 19.80 32.10 26.76 27.70 5.01 14 19.40 31.30 26.00 31.70 23.80 33.01 22.92 34.10 19.40 34.10 27.78 28.65 5.45 6 7 19.40 30.80 25.10 32.70 20.70 33.59 21.89 32792 19.40 8 9 15 17.40 28.80 31.70 28.54 22.86 28.73 17.40 31.70 26.34 28.64 5.24 16 17.60 30.40 28.50 31.70 26.30 29.38 23.54 29.99 17.60 31.70 27.18 28.94 4.65 17 17.60 32.30 30.80 25.90 28.42 25.05 17.60 32.30 26.68 27.16 5.24 18 17.70 32.50 26.40 29.90 24.90 29.25 22.58 31.30 17.70 32.50 26.82 27.83 4.97 20 24.60 29.90 19.90 32.02 23.14 28.89 19.90 32.02 26.41 26.75 4.61 21 31.60 24.00 30.34 24.20 29.40 24.00 31.60 27.91 29.40 3.56 22, 32.60 24.90 30.42 23.90 29.72 23.90 32.60 28.31 29012) 3.74 23 31.00 23.50 31.94 21.47 29.14 21.47 31.94 27.41 29.14 4.66 24 31.20 23.90 32.08 21.54 29.28 21.54 32.08 27.60 29.28 4.64 25 32.70 24.90 32.42 30.70 24.90 32.70 30.18 31.56 3.63 26 34.20 27.60 33.26 23.82 29.28 23.82 34.20 29.63 29.28 4.24 Table 3.—Univariate statistics for salinity (ppt) at each site. All years (February and July) Mini- Maxi- Standard Site 2-96 7-96 2-97 7-97 2-98 7-98 2-99 7-99 mum mum Mean Median deviation 1 18.30 14.10 18.90 15.40 15.80 26.90 28.16 35.48 14.10 35.48 21.63 18.60 7.66 2 13.00 2.70 22.60 1.40 13.00 24.61 25.24 12.70 1.40 25.24 14.41 13.00 Oy 7H/ 3 18.50 19.60 25.10 18.80 17.10 29.10 29.27 37.12 17.10 SZ 24.32 22.35 7.08 4 17.50 17.40 24.50 21.40 16.70 32.15 27.81 36.47 16.70 36.47 24.24 PUPS) a-39, 5) 20.30 21.80 25.40 21.30 17.60 31.94 2.9)35) 36.84 17.60 36.84 AS\3)I 23.60 6.61 6 18.50 26.60 24.60 28.80 20.00 35.94 28.87 35.81 18.50 35.94 239) 27.70 6.44 7 22.10 26.40 24.60 30.50 20.60 37.43 30.47 36.92 20.60 37.43 28.63 28.44 6.34 8 15.80 10.20 19.90 10.90 15.20 23.88 19.38 31.31 10.20 sulesiil 18.32 1 7s)2) 6.97 9 18.10 21.10 21.50 19.20 18.40 28.80 24.06 33.58 18.10 33.58 23.09 21.30 5250) 10 18.10 24.60 21.70 22.30 20.50 35.47 26.86 34.70 18.10 35.47 2S):5)5) 23.45 6.45 11 18.70 24.00 21.50 22.80 19.30 S3ql3) 27.04 34.49 18.70 34.49 25.12 23.40 5.98 12 18.90 23.40 23.30 26.20 20.70 36.97 28.61 29.00 18.90 36.97 25.89 24.80 5.72 13 27.20 32.90 28.70 31.20 26.70 40.51 Ssehll7/ 29.80 26.70 40.51 SE2 7 30.50 4.44 14 28 33.4 28.9 29.2 41.03 32.94 30.1 28.00 41.03 31.94 30.10 4.50 15 31.30 31.30 33.30 26.90 36.75 34.62 40.00 26.90 40.00 33.45 33.30 4.23 16 31.40 34.50 29.60 33.20 30.10 38.73 35.34 36.85 29.60 38.73 8357/2, 33.85 3.25 17 30.70 34.40 33.30 31.70 36.25 32.54 30.70 36.25 33.15 32.92 1.98 18 31.30 35.00 35.10 35.30 29.70 37.15 35.76 29.00 29.00 37.15 33.54 35.05 3.07 20 22.60 19.80 17.10 28.15 24.97 33.39 17.10 33.39 24.34 23.79 5.88 21 25.60 28.90 39.34 34.72 39.71 25.60 SOM 33.65 34.72 6.28 22 24.40 30.20 39.93 35.11 41.30 24.40 41.30 34.19 35.11 7.00 23 34.30 33.00 36.76 34.04 38.39 33.00 38.39 35.30 34.30 2.21 24 34.30 31.90 35.93 35.13 39.00 31.90 39.00 35.25 35013 2.58 25 28.30 29.50 36.07 37.00 28.30 37.00 32.72 32.79 4.45 26 30.30 31.60 35.43 33°51 37.00 30.30 37.00 33.57 33.51 Pas MOLLUSKS PAST AND PRESENT: BREWSTER-WINGARD ET AL. 205 Table 2.—Extended. February (all years) July (all years) Number of Mini- Maxi- Standard Mini- Maxi- Seam CESe Neen mum mum Mean Median deviation mum mum Mean Median deviation Feb. July 19.00 23.00 20.91 20.81 1.64 29.16 31.30 30.34 30.45 0.88 4 4 19.70 23.70 21.45 21.21 1.78 28.80 31.47 30.62 31.10 1:25) 4 4 17.20 23.80 20.71 20.93 Af} 29.18 32.80 B1k35) 31.70 ESS 4 4 19.80 24.60 21.87 21.53 2.00 29.61 32.88 31.60 31.95 152) 4 4 16.50 25.50 21.50 22.00 3.72 30.37 33.42 32.07 32.25 1.37 4 4 19.70 24.40 21.70 21.34 1.98 29.60 33.29 31.45 31.45 1.70 4 4 19.40 25.10 21.77 21.30 2.44 30.80 83159) 32.40 32.61 ici / 4 4 19.20 24.70 20.97 19.98 2.52 29.52 31.60 30.82 31.08 0.92 4 4 17.90 24.10 20.34 19.68 2.65 28.31 Bir32 30.26 30.70 1.35 4 4 17.50 24.20 20.02 19.18 2.97 28.39 31.94 30.76 31.35 1.60 4 4 19.40 23.60 20.75 20.00 1.93 30.50 33.30 31.83 31.76 E52, 4 4 18.50 24.50 21.55 21.60 2.45 28.95 34.58 31.28 30.80 2.43 4 4 19.80 24.60 22.24 22.29 1.96 30.80 32.10 31.28 31.10 0.59 4 4 19.40 26.00 23.03 23.36 2.74 31.30 34.10 32.53 32.36 1.28 4 4 17.40 22.86 20.13 20.13 3.86 28.54 31.70 29.44 28.77 1.51 2 4 17.60 28.50 23.99 24.92 4.72 29.38 31.70 30.37 30.20 0.98 4 4 17.60 25.90 22.85 25.05 4.57 28.42 32.30 30.51 30.80 1.96 3} 3 17.70 26.40 22.90 23.74 3.80 29.25 32.50 30.74 30.60 1.45 4 4 19.90 24.60 225) 23.14 2.41 28.89 32.02 30.27 29.90 1.60 3 3 24.00 24.20 24.10 24.10 0.14 29.40 31.60 30.45 30.34 1.10 2 3 23.90 24.90 24.40 24.40 0.71 29.72 32.60 30.91 30.42 1.50 2 3 21.47 23.50 22.49 22.49 1.44 29.14 31.94 30.69 31.00 1.42 2 3 21.54 23.90 22.72 22.72 1.67 29.28 32.08 30.85 31.20 1.43 2 3 24.90 24.90 =. — — 30.70 32.70 31.94 32.42 1.08 1 3 23.82 27.60 25.71 25.71 2.67 29.28 34.20 82525) 33.26 2.61 2 3 Table 3.—Extended. February (all years) July (all years) Number of Mini- Maxi- Standard Mini- Maxi- Stamtierds me cesce waCHS mum mum Mean Median deviation mum mum Mean Median deviation Feb. July 15.80 28.16 20.29 18.60 5.42 14.10 35.48 22.97 2S 10.13 4 4 13.00 25.24 18.46 17.80 6.40 1.40 24.61 10.35 7.70 10.76 4 4 17.10 29.27 22.49 21.80 Sy7/i 18.80 SNP 26.16 24.35 8.68 4 4 16.70 27.81 21.63 21.00 5.41 17.40 36.47 26.86 26.78 8.94 4 4 17.60 29.35 23.16 22.85 5.24 21.30 36.84 27.97 26.87 7.68 4 4 18.50 28.87 22.99 22.30 4.70 26.60 35.94 31.79 32.31 4.80 4 4 20.60 30.47 24.44 23.35 4.34 26.40 37.43 32.81 33.71 Soil 4 4 15.20 19.90 Si 17.59 2.41 10.20 31.31 19.07 17.39 10.30 4 4 18.10 24.06 20.52 19.95 2.82 19.20 33.58 25.67 24.95 6.71 4 4 18.10 26.86 21.79 21.10 3-710) 22.30 35.47 29.27 29.65 6.79 4 4 18.70 27.04 21.64 20.40 3.80 22.80 34.49 28.61 28.57 6.06 4 4 18.90 28.61 22.88 22.00 4.23 23.40 36.97 28.89 27.60 5.85 4 4 26.70 33.17 28.94 27.95 2.94 29.80 40.51 33.60 32.05 4.78 4 4 28.00 32.94 29.95 28.90 2.63 29.20 41.03 33.43 31.75 5.38 3 4 26.90 34.62 30.94 31.30 3.87 31.30 40.00 35.34 35.03 3.84 3 4 29.60 35.34 31.61 30.75 2.60 33.20 38.73 35.82 35.68 2.46 4 4 30.70 32.54 31.65 31.70 0.92 33.30 36.25 34.65 34.40 1.49 3 3 29.70 35.76 32.97 33.20 2.93 29.00 S77 34.11 35.15 3.54 4 4 17.10 24.97 21.56 22.60 4.04 19.80 33.39 2m! 28.15 6.85 3 3 28.90 34.72 31.81 31.81 4.12 25.60 39.71 34.88 39.34 8.04 2 3 30.20 35.11 32.66 32.66 3.47 24.40 41.30 35.21 39.93 9.39 2 3 33.00 34.04 33.52 S852 0.74 34.30 38.39 36.48 36.76 2.06 2 3 31.90 85513) 33.52 33.52 2.28 34.30 39.00 36.41 35.93 2.39 2 3 29.50 29.50 — — = 28.30 37.00 33.79 36.07 4.78 1 3 31.60 BStor 32.56 32.56 1.35 30.30 37.00 34.24 35.43 3.50 2D, 3 206 BULLETIN 361 ‘Salinity | Range (ppt) | Salinity | i 10-15 Range (ppt) 15-20 i 15-20 GH 20-25 i 20-25 HB 25-30 GH 25-30 WB 30-35 | WH 30-35 February 1996 February 1997 Se aoa : Salinity | | ‘ange (ppt) | Range (ppt) | = os Sos | 5-10 5-0 | @ 10-45 | (i 10-15 | 15-20 | GB 15-20 | 20-25 | [20-25 | HM 25-30 GH 25-30 Gi 30-35 | MB 30-35 | MM 35-40 July 1996 July 1997 Text-figure 3—Maps showing 5 ppt salinity gradients and the prominent cluster designations from the presence-absence Q-mode analysis for the sampling periods from February 1996 through July 1999. Contours are primarily based on our own salinity measurements, however, in areas of sparse sampling we utilized data from Halley (http://sofia.usgs.gov/projects/circulation) to fill in the gaps. bay-wide salinity is less variable in the winter (dry) season than during the summer (wet) season, but the Opposite is true for water temperature. Recorded win- H' = = p,log Pi i=1 where s is the number of species of know proportions ter water temperatures have varied more than 10°C (P|, Pr, Ps - +++ P,) (see Ludwig and Reynolds, 1988, from one year to the next, ranging from a low of p. 92, for complete explanation). 16.5°C (site 5, 2/96) to a high of 28.5°C (site 16, 2/ RESULTS ON). Summer water temperatures have ranged from a low of 28.3°C (site 9, 7/99) to a high of 34.6°C (site MODERN ENVIRONMENTAL DATA 12, 7/98). Seasonal standard deviations for the period Text-figure 2 shows seasonal and annual variations of record are relatively low for water temperatures at recorded in temperature and salinity at our monitoring each site, and water temperatures do not display a sites in Florida Bay. These measurements show that strong geographic gradient (Table 2). MOLLUSKS PAST AND PRESENT: BREWSTER-WINGARD ET AL. 207 Salinity Range (ppt) February 19 FD tp, 4 Salinity | Range (ppt) 20-25 GB 25-30 GM 30-35 MM 35-40 WB 40+ July 1998 Salinity | Range (ppt) Salinity Range (ppt) | July 1999 | Text-figure 3.—Continued. In contrast to temperature, salinity does display a strong geographic gradient. Text-figure 3 illustrates seasonal changes in salinity and Table 3 lists standard deviations calculated for each site. In general, standard deviations for salinity decrease as you move to the south and west in the bay, indicating more stable sa- linity on a seasonal and annual basis. Summer salinity standard deviation values are significantly higher at most sites than the winter values. Salinity at three sites (1, 2, and 8) in the northern transition zone has varied over 20 ppt during the July sampling period from 1996-1999, compared to winter variations at the same sites of 5-12 ppt. Bay-wide salinity has ranged from a low of 1.4 ppt (site 2, 7/97) to a high of 41.3 ppt (site 22, 7/99). MODERN MOLLUSCAN PRESENCE-ABSENCE DATA An unweighted pair-group method (UPGM) dual- cluster analysis, using Sorenson’s coefficient on the modern presence-absence faunal dataset (rares delet- ed), produced the clusters seen in Text-figures 4 and 5. The dual clustering method (Kovach, 1989, 1995) allows direct comparison between the separate Q- mode and R-mode analyses. Q-mode analysis pro- duced seven primary clusters, grouping the modern sample sites based on species found alive at those 208 BULLETIN 361 0 0.2 0.4 0.6 0.8 1 Sorenson's Coefficient Distance Measure Text-figure 4.—Q-mode cluster of presence-absence data from modern monitoring sites. Cluster was generated through MVSP statistical package (Kovach Computing Services, MVSP Plus, version 3.1) using unweighted paired group method, average-linkage (UPGMA), with Sorenson’s Coefficient distance measurement, dual clustering procedure, and random input order. Full data matrix sorted in dendrogram order and labeled clusters can be viewed at http://flaecohist/database/Reference/synthesis. Table 4 indicates which species are responsible for the clusters seen. sites. An examination of the clusters and the associated data matrix, sorted in dendrogram order, indicated which fauna are responsible for the clustering of sam- ple sites seen. Text-figure 3 shows the distribution of the clusters by sampling period. Cluster A groups samples from sites 6, 7, 11, 12 and 14 in eastern and central Florida Bay. The occur- rence of Batillaria minima and/or Melongena corona defines this cluster; constancy (C) and fidelity (F) for Batillaria minima equal 83.3 and 80.0 and for Melon- gena corona 50.0 and 70.3 (Table 4). Fasciolaria spp. and Truncatella spp. also have high fidelity values for this cluster (Table 4). Sites in cluster A can be char- acterized as having a subenvironment with shallow MOoLLusksS PAST AND PRESENT: BREWSTER-WINGARD ET AL. 209 Il 0.68 0.84 1 0.04 0.2 0.36 0.52 Muricidae sp. Arcopsis adamsi Ostrea equestris — Cerithid Fasciolaria spp. Batillaria minima Chione cancellata Diodora sp. Cerithium spp. Carditamera floridana Argopecten irradians Modulus modulus Cerithium muscarum - Prunum sp. - Bittiolum varium Crepidula spp. Brachidontes exustus - Pteria longisquamosa Lucina spp. Tellinid Laevicardium mortoni Marginellid Bulla striata Limaria sp. cf. L. pellucida Truncatella spp. Melongena corona Acteocina canaliculata Parastarte triquetra Turridae sp. A Caecum pulchellum Transennella sp. Anomalocardia auberiana — Lithopoma americanum = Columbella spp. Melampus coffeus = Busycotypus spp. Pleuroploca gigantea — Pinnidae Sorenson's Coefficient Distance Measurement Text-figure 5—R-mode cluster of presence-absence data from modern monitoring sites. Cluster analysis and full data matrix as in Text- figure 4. (<20 cm) water depth in relatively close proximity to mangrove islands, sparse vegetation (<20% Halodule, scattered Thalassia may be present), and soft, “gelat- inous”’ calcareous mud is typical (799-6 is an excep- tion). Average salinity for the cluster is 28.4 ppt, and the range is 18.7—41.0 ppt. Average observed faunal richness? at sample sites in cluster A is three, with a maximum of six faunal groups seen alive during one observation period. ? Faunal richness for the modern presence-absence database is a measure of the number of faunal groups observed alive at a site during one field season. The fauna are frequently grouped into gen- era and occasionally into broader categories (e.g., Marginellids), so Cluster B is defined by the presence of Ostrea equestris (C = 76.9, F = 70.5) and/or Arcopsis adamsi (C = 46.2, F = 87.6), with Brachidontes exustus pre- sent in nine of the thirteen samples in this cluster (Ta- ble 4). The sample sites (1, 2, 3, 8, 9, and 24) are geographically widespread, encompassing the northern transitional zone, eastern, and western portions of this is not “species” richness in the usual sense. In addition, the observation and recording process is definitely biased towards epi- faunal molluscs, and so this is not meant to be a measure of the true richness of the environment. However, because the same categories were used at all sites and similar methods, we feel it is a basis for comparing the faunal richness from one site and one observation period to another. BULLETIN 361 210 (snoru =) = One I SI IS A OD VIE iS DOU VEL I fe) Me “Uul]) snjnpoi snjnpow —- — — woe 9¢ I — 3869 6ZIl 6 —- —- — — — — &eg wnivosnu wuniyiuad 9 rt ae Ae Ea Ri ORS I = eat = — =] Wine OWS We ae AS te LEVIED nC ‘ds wnuntg (Jay = a Se) SOON OS: ae we Se ef AS I NOS wits (5 iwWilfe isi C —_- —- ~~ ~ sed) wniiva unjouyg DO Lei Ol0 Caan. VET 68E L TCL O07 I GM Get FS WAG Wiis Ce (tell Iie 18 os €8 I ‘dds nynpidaid (snaeuurq) Se E18) OCS, MAY, VSt OOF G CS il iv SS (Ss I) te, reteh8) 0) ey OEE SnISNXA SowuOpIyIDAT (4oyunqd) Ee ORE OES I LOL 002 I Sy GNSS GUE MS NS iy EY, I (sie HEINE, DSOUPNDSISUO] Viald ey O;001 OOF (é — ‘dds puionT qd ££6 OOF c meee ee II OTE c PruyleL d (peiuo0)) css OOO! § en ee on /Le) MOLT} 9 oe ee Ge Dl. tee I IUOJLOW LUNIPADIIABVDT df 89 009 oye fSt3 IS OL iE ¢ ao) 9 ea SOE I pypeuisieyy er ANGIE OMS I CLe O07 I Sibi AS I Oe OG © arginsnig VIDLUS DING OD (suepy “€’D) »P = os eee OSS Pan OES) I = —- eet HOS YEAS I OT 67T (6 -1onyjad “7 ‘jo-ds vpiuvuryT gd EST Ore Cc Lop LL I [ty €8 I ‘dds vjjaipounty (uly 2 aii es vie Ole = oa = €0L OOS 9 -aWD) pUOIOD DUasUuojJaW OD (Aes) OOOL 67 G DIDINIYoOUYI YUIIOAIIyY =D (peiu0D) OOOL Ls b DAJNDLY AADISDIVY OOOL 67 c vy ds ovprun, 9 uosduins ig Cl ONG t (1b, (eth I —- —> — wnjjayajnd unzvavy 9 a ae ema (Gil7é BMS I OVSIE Wye ¢ EES LU. I -- — a ‘ds pyjauuasupty (AusiqiO.P) oe c a OLS aC 6¢r O0T I = —— — Fra JES t (sonlnt fll I — — — pupiiaqnyd pipipsojouIoUy qi (uljatu) Ve ONO Sol My T= Sere ae) po Yee I SiG Val I unupoiaup puodoyyntyT Ore O0T I 0199 68 LZ (u10g) MIMIOSP{ DjNBAaL OD cOc =O00T I fos OOS 6 aa a SE ie Stall IS GC 61 C th = YE7E I oe a! ee Ul[EUID VeUuDjsDD Ogun], ee ES Le L OS Se 0) ee ae Oe, Eva Cc Ocl 98 ©) ‘dds pyjaqunjoD 9 (snaeu OOO! FL Tc -urq) snaffoo sndunjaw Tvl O0¢ I 90t OS I es vl I ‘dds sndtjootsng 9 (s9uary) OQOOL OOF TC paquns1s8 poojdoinajgd =D TO08 O09 ¢€ (Sil WE ve ata: me) ONS LAS I sepiuuld d II d 2) O fa 9) O al o) O A e) O a e) O a 7) O A o) O dnoipH yeune{ Sse J3sn[D apoul-y 9) A el d o) d Vv Jasn[Q e2pow-— ‘epodonsey = 5 ‘epodAoajag = d :UONRUSISEp sse[D Jepso WieISOIpUap IpPpoul-yY UI PoLIOS ome eXEL, “SIsATeUR JO}SNID aduasqe-douasaid ay} WIZ Ja}SN{O YORA UT UOXE] YOR JOJ sanyRA (4) AWepy pue “(D) Aouvysuos (QO) 2:ouUeLNIIO— fF IIGBL Table 4.—Continued. Q-mode Cluster G R-mode Faunal Group Cluster Class P Argopecten irradians la (cont'd) (Lamarck) P Carditamera floridana 33.3 66.9 6 14.9 7.4 a Conrad G_ Cerithium spp. G 9 3 20.0 42.1 | 7.8 Diodora sp. MOLLUSKS PAST AND PRESENT: BREWSTER-WINGARD ET AL. 3 P Chione cancellata (Lin- naeus) G_ Batillaria minima (Gme- 3.6 Bo) 83.3 80.0 — 10 lin) G_ Fasciolaria spp. G_ Cerithid 16.7 3 41.7 48.0 5 1 20.0 3.4 Bu), 10 Ostrea equestris Say P 7.0 P Arcopsis adamsi G_ Muricidae sp. Outlier 18 70 Total number of samples/ cluster Florida Bay. The common characteristic of these sites is the presence of wood (mangrove roots, driftwood, or pilings) or exposed limestone bedrock that provides an attachment-point for the cemented Ostrea equestris, or bysally attached Arcopsis adamsi. Salinity values for the cluster range from 2.7—35.1 ppt, and the av- erage is 18.6 ppt. A maximum of seven faunal groups were found alive at sites in cluster B, and the average observed faunal richness is three. Cluster C comprises the largest group of samples (70) from sites 1-17, and 20—22 in the northern tran- sitional, eastern and central portions of Florida Bay. The nearly ubiquitous occurrence of Brachidontes ex- ustus (66 of our 70 samples, C = 94.3, F = 35.5) distinguishes this cluster (Table 4). Within the larger cluster C are six smaller groupings, characterized by species that co-occur with Brachidontes exustus. Av- erage salinity for cluster C is 28.1 ppt, and the range is 10.9—41.3 ppt. The environments represented by the 20 sites in this cluster are varied, including mud banks, mangrove islands, open basins, and channels, but all have at least some subaquatic vegetation present. Sites within cluster C attain the highest values for observed faunal richness; the average is five and the maximum value is 20. Cluster D includes samples from eastern, central, western, and Atlantic transition zone sites (3, 5—7, 10, 11, 13, 15-18, 20, 21, and 26). The occurrence of Pteria longisquamosa |=Pinctada radiata Turney and Perkins] (C = 85.2, F = 45.7) distinguishes cluster D; and the occurrence of Modulus modulus (C = 51.9, F = 71.8) is significant (Table 4). The environments rep- resented by these samples can generally be character- ized by the presence of healthy Thalassia beds (ex- ceptions, 6, 10, and 26). Average salinity for the sam- ples is 29.9 ppt and the range is 19.8—39.7 ppt. Ob- served faunal richness at sites in cluster D averages four, and the maximum value is eleven. A small group of five samples from the northern transitional zone, and eastern and central Florida Bay (sites 2, 3, 9, and 21) constitute Cluster E. The pres- ence of Laevicardium mortoni (C = 100, F = 85.5) distinguishes this cluster (Table 4). All of the sites have a subenvironment with exposed substrate and sparse vegetation. The average salinity for the cluster is 24.0 ppt and the range is 12.7—34.7 ppt. Observed faunal richness ranges from 2—6, and the average is 4. Cluster F includes two distinct sub-clusters, one dis- tinguished by the co-occurrence of Turbo castanea (C = 50, F = 50.5), Tegula fasciata (C = 38.9, F = 66) and Columbella spp. (C = 55.6, F = 77.7), the other by Columbella spp., Cerithium spp. (C 50, F = 64.4), Chione cancellata (C = 27.8, F 52.2) and Carditamera floridana (C = 33.3, F = 66.9) (Table PIMP BULLETIN 361 4). The cluster includes sites from the central, western, Gulf transition, and Atlantic transition zones of Florida Bay (13, 17, 18, 21, 23, 24, and 26). The sites can be characterized as having lush subaquatic vegetation and bare sediment areas available. Average salinity for cluster F is 34.6 ppt, and the range is 29.0—39.3 ppt. Average observed faunal richness is four and the max- imum value is eight for the sites in cluster F Cluster G comprises five samples from the western- most sites (23 and 24) in the Gulf transition zone. Pin- nidae (C = 60, F = 80.2), and Pleuroploca gigantea (C = 40, F = 100) define this cluster (Table 4). Av- erage salinity is 34.1 ppt, and the range is 31.9 to 36.8 ppt. These sites are predominantly calcareous sand bars, with lush beds of mixed subaquatic vegetation present, including Thalassia, Halodule, Syringodium, and many species of calcareous algae, and macro-ben- thic red, green and brown algae. The sites at cluster G have the lowest observed faunal richness, with an av- erage of two and a maximum of five faunal groups found alive at the sites. R-mode analysis produced two primary divisions of the faunal categories, based on the samples in which they are found (Text-fig. 5). In general, fauna in cluster I tolerate a wide range of conditions and can be found in the northern transitional, eastern, central and west- ern portions of the bay. Fauna in cluster I were found alive in salinities ranging from 2.7—41.3 ppt. The re- mainder of the faunal groups fall into cluster I, with the exception of Muricidae sp., a rare species that is an outlier on the dendrogram. Cluster II groups fauna that are typically found in the western portions of the Bay, or at sites with near normal marine salinities. The average salinity recorded at sites where fauna from cluster II are found is 33.3 ppt and the range is 17.6— 40.0 ppt. The exception in cluster Il is Melampus cof- feus. The presence of Melampus is indicative only of the presence of a supratidal environment and the pres- ence of mangroves. MODERN VEGETATION SAMPLE DATA Sixteen vegetation samples and one surficial mud sample were analyzed from sites 8, 12, 13, and 20, collected in February and July 1998.! Brachidontes ex- ustus and Bittiolum varium account for 95% (10,981 individuals) of the 35 molluscan faunal groups found alive in the samples from all four sites. These two species were most frequently found in polytypic sub- aquatic vegetation samples, including Thalassia and macro-benthic algae. Crepidula spp., Cerithium mus- carum, Pteria longisquamosa and Prunum spp. com- bined constitute only 2.25% (260 individuals) of the living fauna collected. MODERN PUSH CoRE DATA Twenty-eight push core samples were analyzed from sites 8, 12, 13, and 20, collected in February and July beginning in 1995.' The push core samples represent death assemblages at each site, and thus the push core data provide a link between modern living assemblage data and down-core assemblages from the core data set. Two cluster analyses were done (Text-fig. 6); one included all specimens, regardless of preservation; the other was limited to only pristine and broken shells. The purpose was to contrast the death assemblage at each site with the living or recently expired fauna. The two clusters produced similar results. All samples from site 8 formed a distinct cluster in both analyses. In general, samples tended to cluster with other samples from the same site in both analyses. Brachidontes exustus and Bittiolum varium are among the four most abundant species in the push cores at all four sites (8, 12, 13, and 20), based on the cumulative data. When the individual push core data are examined for each site, Bittiolum varium is among the four most abundant species and Brachidontes ex- ustus 1S among the six most abundant species. Tran- sennella sp. is among the four most abundant species at sites 12, 13, and 20, and Crepidula spp. at sites 12 and 13. The discrete clustering of site 8 can be ex- plained by the prominence of Hydrobiidae, Truncatel- la bilabiata, and Anomalocardia auberiana. HISTORICAL PISTON CORE DATA Details of the individual core analyses have been previously published (Brewster-Wingard ef al., 1997, 1998a, 1998b; Brewster-Wingard and Ishman, 1999; Ishman ef al., 1996; Wingard et al., 1995).> Text-fig- ures 7—10 illustrate the down-core distribution of key species identified in the modern presence-absence data analysis and in previous core analyses. Shannon’s di- versity index, faunal evenness, the number of faunal groups, and the number of specimens present are also shown on the down-core plots (Text-figs. 7-10). The age model for cores 6A and 19B 1s based on sedimen- tation rates calculated from 2!°Pb analysis. The rate for core 6A is 0.75 cm/yr + 0.08 and for core 19B is 1.27 cm/yr + 0.08 (Holmes, et al., this volume). COMPILED DATA SET Percent abundance data were compiled from the modern vegetation samples and push cores from sites 8, 12, 13, and 20, and from the corresponding piston cores. The compiled database was analyzed using the unweighted pair-group method (UPGM) dual-cluster ‘ All open-file reports and data tables for each core are available on line at http://sofia.usgs.gov/flaecohist. MOLLUSKS PAST AND PRESENT: BREWSTER-WINGARD ET AL. tO — Ww ER 795-8A 798-8A 796-84 | 298-8A 297-8A 296-8A 797-8A | 295-8A = — 795-128 | 797-20A 798-20A 298-20A 796-12B 798-12B 797-12B 298-12B 297-12B 296-12B Push Cores Pristine and Broken Components Counted 12 1 0.8 0.6 Cosine Theta Distance Measurement 298-13C 297-20A 796-13C 797-13C 297-13C 296-13C 295-13C 798-13C 795-13B 295-12B 04 0.2 0 795-8A 798-8A 298-8A 796-8A 797-8A 297-8A 296-8A 295-8A 797-20A 298-13C 797-13C 297-13C 296-13C 796-13C 795-13B Push Cores All Identifiable Components Counted 12 1 0.8 0.6 Cosine Theta Distance Measurement 295-13C 797-12B mm) 798-128 my) 298-128 } 297-20A 297-12B Se) 296-128 " 295-128 0.4 0.2 0 Text-figure 6—Q-mode cluster of push-core data from modern monitoring sites. Top cluster illustrates the results when only the pristine and broken (retaining original material and more than 50% of shell) material are included. Bottom cluster includes all identifiable molluscan components. Clusters were generated using MVSP statistical package (Kovach Computing Services, MVSP Plus, version 3.1) on log-ratio transformed and centered percent abundance data, using unweighted paired group method, average-linkage (UPGMA), with cosine theta distance measurement, dual clustering procedure, and random input order. procedure, with cosine theta distance measures on a log-transformed data matrix (Text-figs. 11 and 12). Q- mode analysis produced three main clusters, grouping the individual samples based on the faun they contain. Faunal groups responsible for the Q-mode clusters were determined by an examination of the associated data matrix, sorted in dendrogram order.* Cluster J is divided into two very distinct compo- +See footnote 1, p. 202. 214 BULLETIN 361 Taylor Creek 24 Hydrobiidae Anomalocardia RXIc Group Transennella sp. Br Crepidula spp. Cerithium Bittiolumt variant Evenness No. of specimens Q-Mode Cluster auberiana muscarum 0 09 coc ASS ; = £ = ] | Evenness G c 40 = Taal i onge o ( 60 — L & = — z E 80 = 2 g 2 Index B 86 ~ 60 0 30 60 0 15 0 15 0 15 0 15 0 15 0 1 2 0 10 20 Percent abundance Shannon's Diversity Faunal Richness Index Text-figure 7—Down-core changes in core T24 from the mouth mode clusters (see Text-fig. 11), significant molluscan fauna (show of Taylor Creek in Little Madeira Bay. Columns illustrate changes in Q- n as percent abundance), Shannon’s diversity index, evenness, number of faunal groups, and number of individual specimens. RXIc group refers to the R-mode cluster shown in Text-figure 12; this group is composed primarily of species that prefer salinities less than 18 ppt. Depth is nents (Text-fig. 11). Cluster JI is primarily composed of modern push core samples, the majority of these from site 8. Cluster J2 is exclusively composed of samples from core T24. A diverse faunal assemblage, blending components of R-mode clusters XIa and XIc (Text-fig. 12) defines cluster J. Anomalocardia auber- iana (C = 93.4, F = 65.4), Acteocina canaliculata (C shown in cm. = 93.4, F = 69), and Hydrobiidae (C = 85.2, F = 92.9) are the dominant fauna in cluster J, and Poly- mesoda maritima, and Cerithidea spp. are character- istic (Table 5). Cluster J1 is further distinguished by a group of species from R-mode cluster XII (Odostomia spp.. Prunum sp., Schwartziella catesbyana, Bittiolum varium juy., and Truncatella spp.). A number of faunal No, of specimens Anomalocardia Pass Key 37 Pteria longisquamosa Cerith L di Evenness s Brachidontes ransennella ol 70 « Modulus modulus auberiana & erenium Crepidul: aevicardium Ags ~ 0 QMode Cluster piles Transennella sp. Bittiolum varium & Modulus modulus RX Group sisdaviinn Crepidula spp. Sa 5 ss oe 8 Sj Zz 20 - at 6 = 3 3 & 3 ta} 8 § | ® cs a. = aS B40 KI = us L a | | | | | | 60 = | > }———4 K2 A KI : = rs = 0 50 0 50 0 20 0 20 0 20 0 20 0 1 2 0 10 20 = Shannon's Diversity Faunal Richness Index Percent Abundance Text-figure 8—Down-core changes in core PK37 from south of Pass Key in eastern Florida Bay. Columns illustrate changes in Q-mode clusters (see Text-fig. 11), significant molluscan fauna (shown as percent abundance), Shannon’s diversity index, evenness, number of faunal groups, and number of individual specimens. RXIc group refers to the R-mode cluster shown in Text-figure 12; this group is composed primarily of species that prefer salinities less than 18 ppt. Depth is shown in cm. MOLLUSKS PAST AND PRESENT: BREWSTER-WINGARD ET AL. Crepidula spp. Cerithiurt mu: Russell Bank 19B Q-Mode Clu iS) nr Evenness No. of specimens 0 1 0 500 1000 7 KI 20 40 z Depth in cm Ki 100 120 {SST K1 140 ai inne 1994 44 4 Evenness 1980 ), of specimens. 1960 1ed4, Index 1940 1920 Faunal 1900 Richness = = — ora Talento T 0 50 100 0 50 100 0 50 0 50 0 Percent abundance : ~ ——— tot “eon SOO 30) Foe eee SOs 10-520 100 200 Shannon's Diversity Index Faunal Richness Rainfall (cm), Text-figure 9 —Down-core changes in core RB19B trom Russell Bank in eastern Florida Bay. Columns illustrate changes in Q-mode clusters (see Text-fig. 11), significant molluscan fauna (shown as percent abundance), Shannon’s diversity index, evenness, number of faunal groups, and number of individual specimens. Rainfall data is compiled from NOAA NCDC website http://www.ncde.noaa.gov/. RXIc group refers to the R-mode cluster shown in Text-figure 12; this group is composed primarily of species that prefer salinities less than 18 ppt. Depth is shown in cm. Age is based on *'°Pb analysis (Holmes ef al., this volume). groups occur in cluster J that are absent in other clus- ters (F = 100, Table 5), indicating cluster J represents a relatively unique and diverse assemblage. These re- sults are consistent with the analysis of the push cores (Text-fig. 6); site 8 push cores formed a distinct cluster, separate from the other sites. The average diversity measures for cluster J are relatively high: Shannon’s diversity index is 2.03; evenness is 0.74; and faunal richness is 16.8. Cluster K represents a mixture of samples from cores 6A, 19B, and 37, with modern push core samples from sites 12, 13, and 20, and modern vegetation sam- ples from sites 8, 12,13, and 20. The common unifying element for cluster K is the presence and relatively high abundance of Brachidontes exustus in all but a few samples (average abundance 32.13%, C = 98.1). A number of species are present in a high percentage of samples (Table 5), but at relatively low percent abundances, forming a distinct and diverse assemblage defined by R-mode clusters XIa and XIb. Cluster K can be subdivided into four components (Text-fig. 11). Cluster K1 is predominantly samples from cores 19B and 37. In addition to Brachidontes exustus, cluster K 1 is defined by the presence of Bittiolum varium, Ceri- thium muscarum juy., and Rissoidae. The core samples in K1 can be further divided based on the abundance of Pteria longisquamosa, Modulus modulus and mar- ginellids in Kla and Transennella sp., Chione cancel- lata, Olivella pusilla, and Vermicularia sp. in K1b. Cluster K2 is faunally diverse and contains a mixture of vegetation, push core and core samples primarily defined by R-mode cluster Xla species, including Laevicardium mortoni and Tellina spp., which distin- guishes this cluster from K1. The occurrence of Cer- ithidea spp. with abundant Brachidontes exustus iso- lates the four samples that constitute cluster K3. Clus- ter K4 is primarily vegetation samples and is lower in diversity that the rest of cluster K. Bittiolum varium, 216 BULLETIN 361 Bob Allen 6A Transennella sp. Brachidontes exustus Crepidula spp. Cerithium muscarum Bittiolum varium Pteria longisquamosa Chione cancellata_ Anomalocardia = Mae: Q-Mode Cluster & Modulus modulus & Perici auberiana a ashe : jen \ 1994 \ ~ Sy Zz wns & 1980 y a 3 < 3 20 | - — YS 2 3S fat 1960 6 : L = 1940 <> — <= <> => 1920 “< E > > o ¢ p> 1900 ¢ ) o. cy Eo les a : ae |e ) 80 ) Evenness| jl 2 7, . 1880 > >- > 100 = ) = J } LL > 1860 >> ’ 1840 120 } 4 =a 1820 Faunal 20 = Richnes§ Index A F p> | > > mS Hx Za 1800 = > > ES ) 37 9 8.4 63.1 G Crassispira spp. 9 8 82 1 1.9 18.0 12 Nucula proxima Say 7 6.5 77.9 1 1.9 22.1 G Rissoina cancellata Philippi 2 3 21 13 12 9 G Batillaria minima (Gmelin) 9 NS) 84 3 3 16 P Mysella planulata (Stimpson) 1 2 14 9 8.4 70.7 1 1.9 15.6 G Amaea retifera (Dall) | 2 10 16 15.0 90.1 G Muricidae sp. B 11 18 76 6 6 24 G Olivella ? sp. 5 4.7 71.6 1 1.9 28.4 G Muricidae sp. A 3 5) 32 9 8.4 55.4 1 1.9 12.2 G Finella sp. 6 6 75 1 1.9 24.8 G Conidae juv. 1 2, 23 6 5.6 77.4 G Pyramidellidae 6 10 47 8 a 36 2 3.7 17.6 1p Argopecten irradians (Lamarck) 1 2 14 7 6.5 55.0 2 aia Bi 12) Tagelus sp. 16 26 100 P Pitar simpsoni (Dall) 2 3 13 11 10.3 41.7 6 ates 45.0 G Vitrinellid 15 25 67 13 12 33 G Cyclostremiscus suppressus 5) 8 32 19 18 68 (Dall) P Limaria sp. cf. L. pellucida 4 7] 18 3] 29.0 TES 1 1.9 5.0 (C.B. Adams) XIIb Pp Arcopsis adamsi (Dall) 7 11 34 24 22.4 66.2 G Vermicularia sp. 2 3 16 18 17 84 G Caecum pulchellum Stimpson 4 7 20 26 24 74 1 1.9 5.7 G Rissoidae 2 3 8 38 3525 91.5 XIlc G Bittiolum varium (Pfeiffer) juv. 14 23} 39 38 36 61 G Odostomia spp. 10 16 39 27 25.2 60.6 G Prunum apicinum (Menke) 8 13) 69 220) 21 61 G Schwartziella catesbyana 13 21 46 23 DAS 46.2 2 Shi/ 8.0 (d’ Orbigny) G Truncatella spp. 16 26 85 5 4.7 15.1 Total number of samples/cluster 61 107 54 (Halley, http://sofia.usgs.gov/projects/circulation; Johns et al., 1999; NOAA NCDC website http:// www.ncde.noaa.gov/). In the northern and eastern portions of Florida Bay, salinity varies more than temperature at each site on both a seasonal and an annual scale. Typically at each site, there is less fluc- tuation in salinity from year to year in February (the “dry” season), than during July (the ““wet™ season). The exception is the 1998 pattern; during 1997-1998, a very strong El Nino affected regional rainfall throughout southern Florida, bringing heavy winter- time rain. This was followed by a strong La Nina causing a hot dry summer in southern Florida. Text- figure 3 illustrates the effect of the anomalous re- gional wintertime rainfall on the salinity of northern and eastern Florida Bay. February 1998 resembles a typical summer pattern, whereas July 1998 resembles a winter pattern. MODERN ANALOGUES Five distinct molluscan associations were identified from the analysis of the modern presence-absence da- tabase. Assemblages identified by clusters B and E (Text-fig. 4) are minor components of larger commu- 220 1.8 BULLETIN 361 Truncatella spp. Schwartziella catesbyana Prunum apicinum Odostomia spp. Bittiolum varium juv. Rissoidae Caecum pulchellum Vermicularia sp. Arcopsis adamsi Limaria sp. cf. L. pellucida Cyclostremiscus suppressus Vitrinellid Pitar simpsoni Tagelus sp. Argopecten irradians Pyramidellidae Conidae juv. Finella sp. Muricidae sp. A Olivella ? sp. Muricidae sp. B Amaea retifera Mysella planulata Batillaria minima Rissoina cancellata Nucula proxima Crassispira spp. Caecum cornucopiae Melongena corona Turbonilla spp. Lucina pectinata Eulimidae Lithopoma americanum Anodontia alba ? Codakia spp. Hyalina sp. Marshallora nigrocincta Gastrocopta sp. Eulithidium sp. Ostrea equestris Diodora sp. Cyrenoida floridana Lucina sp. Semele bellastriata Fasciolaria spp. Lucinisca nassula Parvilucina multilineata Naticidae Physidae Polygyridae Epitonium rupicola Haminoea sp. Turridae sp. A Melampus coffeus Busycotypus sp. Assiminea succinea Nassarius sp. Lymnaea columella Cerodrillia sp. At sp Rictaxis punctostriatus Acteocina canaliculata Anomalocardia auberiana Cerithidea spp. Hydrobiidae Polymesoda maritima Semele proficua Mytilid Mytilopsis leucophaeata Parastarte triquetra Cumingia tellinoides Bulla striata Marginellid | Olivella pusilla Chione cancellata Cerithium muscarum Transennella sp. Tellina spp. Laevicardium mortoni Pteria longisquamosa Modulus modulus Crepidula spp. Brachiodontes exustus Cerithium muscarum juv. J Bittiolum varium 1.5 iy 0.9 0.6 0.3 0 Cosine Theta Distance Measurement MOLLUSKS PAST AND PRESENT: BREWSTER-WINGARD ET AL. 221 Table 6.—Salinity and temperature ranges for molluscan taxa observed at monitoring sites. Salinity (ppt) Temperature (deg. C) Neue Minimum Maximum Average Minimum Maximum Average Observations Acteocina canaliculata 20.7 23.9 22.3 21.6 30.9 26.2 2 Anomalocardia auberiana 15.2 39.3 29.0 20.0 34.6 27.8 8 Arcopsis adamsi 15.8 35.1 24.8 19.2 32.0 24.8 9 Argopecten trradians 20.6 41.3 31.8 Wot 33.6 27.6 22 Batillaria minima 16.7 41.0 2TES) 19.4 34.6 26.6 24 Bittiolum varium 13.0 41.3 27.6 19.9 34.6 26.2 26 Brachiodontes exustus 10.2 41.3 27.4 1922. 34.6 27.4 85 Bulla striata 19.6 40.5 28.8 16.5 33.4 27.9 12 Busycotypus spp. Sil) 36.9 34.7 23.9 33.3 29m 3 Caecum pulchellum 15.2 28.2 22.4 20.0 32.0 27.6 3 Carditamera floridana 17.1 39.7 Sef 21.4 34.2 28.2 10 Cerithid 10.2 33.3 232 17.7 33.4 26.9 12 Cerithium muscarum 17.1 40.5 29.8 19.9 34.6 28.6 10 Cerithium spp. 15.8 38.4 30.9 21.0 34.6 28.8 21 Chione cancellata 24.4 41.3 34.1 25.5 34.2 30.4 18 Columbella spp. 17.6 40.0 34.3 DileS 34.2 29.0 18 Crepidula spp. 15.4 40.5 27] 19.4 34.6 26.3 43 Diodora sp. 20.6 37.0 30.0 20.7 34.6 28.5 9 Fasciolaria spp. 21.8 3957 31.4 17.4 34.2 All 19 Laevicardium mortoni 12.7 41.0 28.3 19.4 34.6 26.6 12 Limaria sp. cf. L. pellucida 27.0 36.9 30.9 20.2 32.0 27.0 4 Lithopoma americanum 29.0 36.8 33.4 PAGS) 32.3 28.1 5) Lucina pectinata NPT 25.1 18.9 23.8 28.8 26.3 2 Marginellid 12.7 36.5 24.4 17.4 32.9 2553 15 Melampus coffeus PIES} 34.4 27.9 32.3 32.9 32.6 2 Melongena corona 14.1 41.0 24.9 19.8 33.0 25.8 16 Modulus modulus 19.6 3I9)7/ 30.7 17.6 34.6 28.4 21 Muricidae sp. 26.9 36.8 Sills) 20.0 30.4 259) 5) Ostea equestris 2.7 39.0 20.5 19.2 31.3 24.8 1S Parastarte triquetra 20.7 40.5 31.6 21.6 34.6 30.1 4 Pinnidae 27.0 38.4 33.6 20.2 8251 2729) 6 Pleuroploca gigantea Si-9) 34.3 33.1 23.9 31.0 DUS 2 Prunum sp. 17.1 41.0 30.4 16.5 34.6 28.3 25 Pteria longisquamosa 10.2 40.5 29'3 17.4 33.4 QED 62 Tegula fasciata 29.0 38.4 34.6 2IES 31.9 2/3) 7 Tellinid WAG 40.5 27.6 24.0 32.1 29.2 4 Transennella sp. SEZ: 39.3 28.4 20.0 34.6 28.3 q/ Truncatella spp. 15.2 30.5 22.2 20.0 30.9 23:2 4 Turbo castanea 213 38.4 33.2 17.6 BORO) 26.4 16 Turridae sp. A 20.7 28.2 24.4 21.6 32.0 26.8 2 nities within Florida Bay, and are not considered sig- ditions. This assemblage frequently co-occurs with the nificant for this study. Text-figure 13 shows the geo- graphic range of five communities in Florida Bay, and Text-figure 3 shows the changing distribution from season to season over the period of observation. Batillaria/Melongena Assemblage The Batillaria/Melongena assemblage defined by cluster A represents a unique set of environmental con- Brachidontes assemblage (cluster C), but occupies a unique subenvironment at each site. Subenvironments were not analyzed separately, therefore, the occurrence of the Batillaria/Melongena assemblage is not always reflected on the distribution maps (Text-fig. 3). This assemblage appears to be restricted to eastern and cen- tral Florida Bay, in very shallow areas with sparse sub- aquatic vegetation and in close proximity to islands. ae Text-figure 12.—R-mode cluster of compiled data (cores, push-cores, and vegetation samples). Clusters were generated using MVSP statis- tical package (Kovach Computing Services, MVSP Plus, version 3.1) on log-ratio transformed and centered percent abundance data, using unweighted paired group method, average-linkage (UPGMA), with cosine theta distance measurement, dual clustering procedure, and random input order. Full data matrix sorted in dendrogram order can be viewed at http://flaecohist/database/Reference/synthesis. 22) BULLETIN 361 é oes D6 | ie Cluster G .@, Extent of Cluster ae, | Distribution | i = Cluster A | j~t— Cluster C © ® tt Cluster D | Cluster F Text-figure 13.—Map showing range of distribution of presence-absence clusters over course of sampling period from February 1996 through July 1999. This represents a compilation of data shown on individual seasonal plots in Text-figure 3. Clusters B and E are not shown; the distributions are limited and non-contiguous. Dense Batillaria minima consistently have been pre- sent at site 14 since the beginning of our observation period (Text-fig. 3). Salinity does not appear to be a strong controlling factor; Batillaria minima and Me- longena corona have been found from mesohaline to hypersaline conditions (Table 6). These observations are in general agreement with Turney and Perkins (1972). They identify Melongena corona as a com- mon species in the northern subenvironment and Ba- tillaria minima as an intertidal species found in sedi- ments near land; we have commonly found Melongena corona in the northern transitional and eastern divi- sions of Florida Bay. ° Turney and Perkins (1972) indicate it is unusual to find Batillaria anywhere but in the immediate vicinity of dry land, and they place a great deal of significance on finding it ““more than 1/4 mile from present land” at site 7403. Site 7403 is in close proximity to our site 11, on the southern end of the mud bank extending south from Park Key. We have observed live Batillaria at site 11, and on other mudbanks extending outward from land (sites 4, 7, 12). We believe this is a typical habitat for Batillaria and disagree with Turney and Perkin’s interpretation of its presence as being indicative of recent migration of Park Key (Turney and Perkins, 1972, p. 29). Brachidontes Assemblage The Brachidontes assemblage defined by cluster C is the most predominant molluscan community found in eastern and central Florida Bay. Brachidontes ex- ustus 18 commonly found alive at most sites in this region of the bay, regardless of salinity, water depth, substrate, or clarity. The low fidelity values for Brach- idontes exustus in cluster C (Table 4) are due to the ubiquitous nature of the species. Although Brachidon- tes exustus is euryhaline, ranging from 10.2—41.3 ppt, the average value is 27 ppt.° Brachidontes exustus have been found in the deepest parts of the basins in eastern Florida Bay, bysally attached to exposed lime- stone, and on the tops of mud banks attached to sub- aquatic vegetation. Brachidontes exustus are found at- tached to almost all common types of vegetation, in- cluding Thalassia, Halodule, Sargassum, Chondria, ° The mean and median salinity values for Brachidontes are 27.45 and 28.8 ppt, based on 85 observed occurrences of the species. These values do not take into account the abundance of the species at a site, and may in part reflect the frequency of sampling within higher salinity ranges (see Text-fig. 2). MOLLUSKS PAST AND PRESENT: BREWSTER-WINGARD ET AL. and Laurencia, and to exposed limestone and shell de- bris. When Brachidontes exustus are very abundant they commonly form “nests” in clumps of Chondria, Laurencia, and dead Thalassia, and they were ob- served forming a dense “Brachidontes-mat” by at- taching to each other across the top of an expansive shoaling area (2/97, site 12). The most abundant Brachidontes exustus concentrations we have observed are typically found on the sides of the mud banks in clumps of Chondria and/or Laurencia in relatively murky water. In the process of collecting and process- ing samples, we have determined that Brachidontes exustus are very tolerant of low water quality; they have been found alive several days after collection in sealed plastic bags, filled with decaying organic ma- terial. Given the wide range of environmental condi- tions under which Brachidontes exustus have been found, it is difficult to determine what factors control their distribution. Given these tolerances it is note- worthy that Brachidontes exustus are primarily re- stricted to the northern transitional, eastern, and central portions of Florida Bay. A possible explanation is that their distribution is a function of decreased competi- tion or fewer predators in this region of the bay. An examination of the associated species that sep- arate the sub-clusters within C indicates some of the environmental variables that control the distribution of the Brachidontes assemblages. Sub-cluster Cl is de- fined by the co-occurrence of Brachidontes exustus with Prunum apicinum; these species are most com- monly found together on clumps of Laurencia or Chondria. The co-occurrence of Brachidontes exustus and Pteria longisquamosa with Argopecten irradians or Chione cancellata delimits sub-cluster C2. This group of species is indicative of relatively clear water and abundant healthy Thalassia; macro-benthic algae may be present. Sites with Brachidontes exustus alone or with Batillaria minima form sub-cluster C3. Batil- laria minima are present when the water is very shal- low, the substrate is generally soft mud, and the veg- etation is sparse. Due to Brachidontes exustus toler- ance of varying salinity and substrate conditions and relatively poor water quality, the presence of B. ex- ustus alone may indicate the environment is not suit- able for other epifaunal molluscs. Sub-clusters C4 and C5 have relatively high values for faunal richness. Pteria longisquamosa, Crepidula spp., Bittiolum var- ium, and Prunum apicinum may be present with Brachidontes exustus, and a number of other species in R-mode cluster Ia. Species from R-mode cluster Ib are included in sub-cluster C5. These diverse faunas are typically present when the substrate consists of mixtures of Thalassia and macro-benthic algae includ- ing Polysiphonia, Chondria, and Laurencia. Sub-clus- i) i) eS) ter C6 is defined by the presence of Brachidontes ex- ustus and Crepidula spp.; Crepidula are generally found on Thalassia, and like Brachidontes exustus, ap- pear to be relatively tolerant of reduced water quality. Count-data from the modern vegetation samples and the push cores are in agreement with presence-absence observation data, and provide further evidence of the predominance of Brachidontes exustus in the mollus- can fauna of Florida Bay. Out of 11,597 total individ- uals collected on vegetation samples in July 1998, we found 5713 Brachidontes exustus (49.26%). These numbers are comparable to the findings of Lyons (1998). He found Brachidontes exustus comprised 78% of all the molluscs he collected in an extensive sampling program throughout Florida Bay in the sum- mer of 1994 that gathered nearly 14,000 living speci- mens greater than 3 mm. In the pristine fraction of the push core samples, Bittiolum varium comprises 30.3% of the specimens, and Brachidontes exustus 13.0%, followed closely by Transennella sp. at 11.43%. When all the fragments and worn specimens are included from the push core data, Brachidontes exustus com- prises 20.64% of the total molluscan specimens, and Bittiolum varium 19.74%. The lower values for Brach- idontes in the pristine sub-set are probably due to the fragility of the shell. Pteria Assemblage Pteria longisquamosa [=Pinctada radiata Turney and Perkins] and its associated species Modulus mod- ulus, and Argopecten irradians define cluster D. This association of species is typically found on the sides of mudbanks (40—150 cm of water) in dense Thalassia beds, relatively clear water, and salinities between 20 and 40 ppt’ (Table 6), in eastern, central, western and Atlantic transition zones of Florida Bay. Although Pteria longisquamosa has been found at its densest concentrations attached to Thalassia, it has also been found on macro-benthic algae, particularly Chondria and Laurencia, and it has the ability to camouflage itself to match the color of the vegetation to which it attaches. The occurrence of Preria longisquamosa in relatively clear water raises an interesting question of whether P. longisquamosa occurs there because the water is clear, or whether the water is clear due to the filtering activity of P. longisquamosa. The latter es- pecially may be true where Pteria longisquamosa are extremely abundant. Prteria longisquamosa, however, seem unable to survive in water of diminished quality; 7’ The mean and median salinity values for Pteria longisquamosa are 29.3 and 29.7 ppt, based on 62 observed occurrences of the species at a site. These values do not take into account the abun- dance of the species at a site, and may in part reflect the frequency of sampling within higher salinity ranges (see Text-fig. 2). 224 BULLETIN 361 they generally die within hours of collection. Typical- ly, the Preria assemblage occurs outside the 20-ppt contour and to the east, south, or west of the Brachi- dontes assemblage (Text-fig. 3). Based on our obser- vations, we believe the distribution of the Preria as- semblage is controlled by a combination of salinity, substrate, water depth, and water clarity.* The domi- nance of this combination of species in a death assem- blage would be indicative of polyhaline to euhaline relatively clear water, deposition on the side of a mud bank in 40-150 cm of water, and the presence of a relatively dense Thalassia bed. Turney and Perkins (1972) found Brachidontes ex- ustus, Pteria longisquamosa, Cerithium muscarum and Bittiolum varium to be the characteristic species of their interior subenvironment, which corresponds ap- proximately to the eastern and central divisions of our current usage. Their results agree with our analyses. The distribution of the Brachidontes and Pteria assem- blages overlap in central and eastern Florida Bay (Text-fig. 13). Turney and Perkins (1972, p. 10) state that the molluscs in the interior subenvironment are able to “survive large salinity fluctuations and other effects of poor circulation.” They point out the ability of the characteristic species to survive in other sub- environments, but suggest that one reason they flourish in the interior may be a lack of competition. Our data support the idea of wide salinity tolerances for these assemblages, but our data indicate Pteria longisqua- mosa is sensitive to water quality. This apparent dis- crepancy can be explained by the fact that Turney and Perkins were analyzing death assemblages. The “Western” Assemblages The Turbo, Tegula, and Columbella association that forms cluster Fl has been found at three sites (17, 18, 23) in the western, Atlantic and Gulf transition zones; these sites have a mixture of various types of sub- aquatic vegetation including Thalassia, Syringodium and Halodule and calcareous green algae. These sites also have varying substrates and water depths, because each site has a channel bordered by a mudbank or sandbar. Currents flowing through the channels can be strong at times, and the water is typically clear; salin- ities have ranged from 25—38 ppt. Based on our ob- servations, we consider this assemblage to be indica- tive of near normal marine conditions (upper polyha- line to euhaline), relatively clear water, and the pres- ence of sub-aquatic vegetation. Currents and varying substrates also may be determining factors in the dis- * Water depth, water clarity, and vegetation are not independent of each other. The tops of the mudbanks typically have less vege- tation and more material in suspension than the sides of the banks. tribution of the Fl assemblage, but we have not ob- served this assemblage frequently enough to reach a conclusion. Cluster F2 is a weak association of species including Cerithium spp., Chione cancellata, Carditimera flori- dana, and Columbella spp. and other faunal groups from R-mode cluster Ia. The cluster is formed of sam- ples from sites 13, 17, 21, 24, and 26 in the central, western and Gulf transition zones of Florida Bay. Sa- linities for the sites in cluster F2 range from 30—39. Our data suggest this assemblage represents euhaline conditions, but the limited observations and weak as- sociation of fauna make this a speculative conclusion. Pinnidae and Pleuroploca gigantea are the critical fauna in cluster G. These taxa are generally found in the western most sites (23 and 24) in the Gulf transi- tion zone and they are representative of open marine euhaline conditions. Pinnidae are found in shallow shoaling areas on top of banks, partially submerged in the substrate. The substrates have varied from muddy calcareous sand to firm calcareous mud. These fauna have been rarely observed, but seem indicative of eu- haline conditions. Our observations of the more euhaline marine as- semblages differ from Turney and Perkins (1972). Lithopoma americanum |=Astraea americana Turney and Perkins, 1972] and Tegula fasciata were listed as characteristic species of Turney and Perkin’s (1972, p. 13) Atlantic subenvironment, and they stated that “the Atlantic group is composed of species which are al- most entirely restricted to that part of the bay which is influenced by the Atlantic Ocean.” Although our observations of living Lithopoma americanum and Te- gula fasciata are limited, we have observed both spe- cies in the central (site 17), Atlantic (site 18), and Gulf transition (site 23) zones. Comparison of Presence-Absence Data with Other Data Through quantitative and qualitative comparisons of the death assemblages represented by the push core data with other data sets (Lyons, 1995, 1998; Turney and Perkins, 1972; and our modern vegetation and ob- servation data discussed above) we have determined that the push core data are a valid representation of the fauna that have lived at each site during the 0-10 years preceding collection. The prominence of Brach- idontes exustus and Bittiolum varium in the push cores from sites 8, 12, 13, and 20 agrees with our modern vegetation data from those sites. Transennella sp. and other infaunal organisms (absent in the presence-ab- sence observation data and the vegetation sample data) are a significant component of the push-core assem- blages. Their absence from the observation and veg- MOLLUSKS PAST AND PRESENT: BREWSTER-WINGARD ET AL. aS) etation data sets does not indicate a lack of agreement with the push core data but is simply an artifact of our method of observing and sampling (see discussion un- der methods). Turney and Perkins (1972) did a detailed analysis of the death assemblages at over 75 stations in Florida Bay in the 1950’s and they concluded that “transportation of shells larger than silt size is not sig- nificant in Florida Bay” (1972, p. 32). Only local mi- gration of shells takes place and “‘faunal dislocations” are rare. Diagenetic and depositional processes have little effect on the distribution of molluscan assem- blages (Turney and Perkins, 1972, p. 35). Thus, their work supports our conclusion that push core data pro- vide a valuable addition for down-core comparison to the historical data set. HISTORICAL PISTON CORE DATA Three primary clusters are formed by the analysis of the compiled data set (modern vegetation samples, push cores, and piston cores) (Text-fig. 11). Only the Brachidontes assemblage that defines cluster C in the modern analysis is represented in the compiled data set as cluster K. The other modern assemblages iden- tified in the cluster analysis of the presence-absence data set are not represented in the piston core data. The absence of the modern assemblages (with the exception of the Brachidontes assemblage) from the piston cores can be explained by a number of factors. The Batillaria/Melongena assemblage typically is lim- ited to shallow-shoaling areas in relatively close prox- imity to land. The four piston cores were not taken under these conditions in the modern environment, and the nearly complete absence of Batillaria minima and Melongena corona from the piston cores implies these conditions did not exist in the past at the localities where piston cores were taken. Clusters B and E, the Ostrea/Arcopsis assemblage and the Laevicardium as- semblage, are limited to only a few sites in the modern sampling, are loosely associated groups, and are gen- erally affiliated with Brachidontes. When these species are present within the piston core, the samples join with other clusters. Pteria longisquamosa are present in the piston cores (primarily RB19B and PK37), but do not form the discrete Pteria assemblage seen in cluster D of the modern analysis. Instead, Pteria lon- gisquamosa are a component of the Brachidontes as- semblage in cluster Kla. The fragility and low pres- ervation potential of Preria longisquamosa shells most likely affect their relative abundance in the piston core data, although they are easily recognizable from small fragments. This observation agrees with the results of Turney and Perkins (1972); they did not distinguish separate Pteria longisquamosa = [Pinctada radiata Turney and Perkins 1972] and Brachidontes exustus groups in the death assemblages from the interior sub- environment where they found both species to be abundant. The key species in the two western assemblages (clusters F and G) are completely missing from the piston cores. Turbo castanea, Tegula fasciata and Col- umbella spp., which comprise cluster Fl, are not pre- sent in any piston core samples. Cluster F2 is a more loosely associated group, defined by the presence of Columbella spp., Cerithium spp., Chione cancellata, and Carditimera floridana; Carditimera and Colum- bella are absent from all piston core samples. Ceri- thium and Chione are present, but typically in associ- ation with Brachidontes or Transennella dominated as- semblages. Pinnidae and Pleuroploca gigantea (cluster G) are absent from the piston cores, but Lithopoma americanum is a rare component in the upper 50 cm of piston core BA6A. The absence of the Turbo/Te- gula/Columbella and Pinnidae/Pleuroploca assem- blages from the piston cores indicates that during his- torical times conditions in northern, eastern and central Florida Bay did not reach the more open marine con- ditions currently seen in the western, Gulf, and Atlan- tic transition zones. Compiled Data The down-core distribution of the three primary clusters formed by the compiled data analysis, and the relationship of the modern vegetation and push core data to the historical piston core data, are shown in Text-figure 14. The unique character of the molluscan assemblage in Little Madeira Bay (site 8 and piston core T24 site) is apparent. Cluster J (Text-fig. 11) is predominantly composed of samples from piston core T24 and modern site 8. Abundant Hydrobiidae and Anomalocardia auberiana, combined with the less common Acteocina canaliculata, Polymesoda mariti- ma, and Cerithidea spp. (R-mode XIc group, Text-fig. 12), separate these samples from the samples in eastern and central Florida Bay. The species in R-mode cluster XIc are relatively rare outside of Little Madeira Bay. Only a few samples from other localities join cluster J (piston core PK37 10 cm; push cores from site 20, and a push core and vegetation sample from site 12); these samples join the cluster due to the presence of Anomalocardia and Acteocina. Turney and Perkins (1972) identified Anomalocardia auberiana [=Anom- alocardia cuniemeris Turney and Perkins, 1972] as the characteristic species of the northern transitional zone, and Acteocina canaliculata [=Retusa canaliculata Turney and Perkins, 1972] as a common species. Ly- ons (1996, 1999) has determined that zones of An- omalocardia occurrence will shift with changes in sa- linity. Thus, the higher abundance of Anomalocardia @ L#8-867 ‘€#V8-864 =| ‘ZHVS-B6L ‘THV8-86L fet HTS ae V8-967 ‘W8-L6L ‘V8-96L ‘W8-L6Z ‘W8-862 ‘V8-86L ‘V8-S6L ‘V8-S6Z ea on eee Seo ere eed S > ae £86 ig °F Uke Bere Sa mw ||O Ue 20s a Oe eOmemoES iS) al aa) gl S| = Es i?) + 2 ela | : = 1S) g GHOZ-B67 ‘ZHOZ-867 ‘FH0Z-867 Eee ‘EHV OC-R6L ‘THWOC-B6L C#07-86Z Se aie os a omen Sod tp MM. 07-867 °9 VOZ-86Z ‘VOZ-L6L is > is > bx v2) Pet {=| D Mi =: ™ ag WD om Ra a Pu ee) foe) Z iF WM, THTI-862 ‘FHTT-R62 THZT-B6Z a . PHATI-B6L sl AZI-L6Z ‘AZ1-962 ‘AZI-862 ‘AZI-L6L ‘ATI-S6Z ‘ATI-S6L ‘AZT-96L ra) = lop) >) 3) ea faa S716 VN 121-862 y Z e & | M M4 M3 S on 3 SS =. — Fs ‘ 3 w ba —— ia ZHEL-86L MB < cw ENEMA D€1-967 ‘DET-L6Z ‘DET-L6L ‘DET-B6Z ‘DET-S6Z ‘AET-S6L ‘DET-96L ‘DET-B6L e mera = = =; c = oo — SRLS Se ee eee 8 < 2 Sk Mh , BS Sa Sh, Se as aS SS S SS ot mo} i Bes ree =z Qs s Sy ~ Ses ° S fee eleva OS Nae SS, so pa pa ve oS ° ro) =) =) = iS) eS aovj1ayU] 18} -eoRJINS a Py ne Se = SS = vr © (wo) yidaq (co | Text-figure 14.—Relationship between Q-mode cluster assignment (compiled data set, Text-fig. 11) and sample position. Specific push-core and vegetation samples are identified. MOLLUSKS PAST AND PRESENT: BREWSTER-WINGARD ET AL. D2, Text-figure 15—*Blow-out” areas at Bob Allen mudbank, February 1999. Sharp transition between lush Thalassia beds and areas of gelatinous calcareous mud are visible. Photo courtesy of Thomas Scott, Florida Geological Survey. and Acteocina in some samples from Pass Key and Russell Bank may be indicative of lowered salinities. Samples from piston cores RB19B and PK37, and the upper portion of BA6A, are primarily grouped in cluster K (Text-figs. 11 and 14). This is equivalent to the Brachidontes assemblage identified in the modern presence-absence data analysis. Modern push cores and vegetation samples from the corresponding sites (12, 13, and 20) also fall into cluster K in the com- bined analysis. These sites occur within eastern and east-central Florida Bay, and they can be characterized as shallow mud banks with sub-aquatic vegetation and macro-benthic algae present. Salinities have ranged from 17—33 ppt at site 20, 19-37 ppt at site 12 and 27-41 ppt at site 13 during our periods of observation. Typically, either the Brachidontes or Pteria longisqua- mosa assemblages have dominated at these sites in the modern presence-absence data (Text-fig. 3). The prev- alence of the Brachidontes assemblage down-core for PK37 and RB19B, and down to approximately 54cm in BA6A, indicates that the general environmental conditions were the same in the past. The common species in cluster K correspond to the characteristic species identified by Turney and Perkins (1972) for their interior subenvironment. Samples from the lower portion of piston core BA6A are dominated by the Transennella assemblage that defines cluster L. This assemblage also is seen in portions of RB19B (30 cm and 118 cm) and PK37 (6 cm). This is an infaunal assemblage and so it was not identified in the modern presence-absence analysis. Transennella sp. are present in the modern push core samples, but they are components of diverse Brachi- dontes assemblages, and thus the samples join cluster K. Bob Allen mudbank today (site 13) is distinctive among the sites discussed here. Lush Thalassia beds adjoin “‘blow out” areas at site 13 (Text-fig. 15) and the transition from grass to gelatinous carbonate mud is very sharp. Low diversity Transennella assemblages seen in the piston core may be the down-core repre- sentation of these modern “‘blow-out” areas, but we have not sampled the modern analogue for this cluster and can only speculate on what it indicates about the environmental conditions. Piston Core T24 Historical changes in molluscan fauna at the mouth of Taylor Creek (piston core T24) are shown in Text- figure 7. The gradual decrease of the R-mode XIc and the increase in Brachidontes exustus, Crepidula spp.. and Cerithium muscarum up-core illustrate the gradual increase in salinity that has occurred at this site during 228 BULLETIN 361 the time of deposition. Brachidontes exustus increase significantly in the upper 20 cm of the core. Modern analogue data (discussed herein; Turney and Perkins, 1972; Lyons, 1996, 1998, 1999) have demonstrated that Brachidontes exustus seem most abundant in areas of fluctuating salinity and in areas where macro-ben- thic algae are available for habitation. Fluctuations in salinity at this site could be attributed to changes in fresh-water flow due to climatic change, or changes in water management practices, or it could be due to long-term changes in sea level. Fluctuations in the rel- ative abundance of Hydrobiidae may be directly in- dicative of changes in fresh water flow. Hydrobiidae are minute (generally less than 3 mm) fresh-water gas- tropods that cannot survive in estuarine waters. They arrive in Little Madeira Bay via terrestrial freshwater flow through Taylor Creek, and perhaps their abun- dance can be related to flow rates, but additional field- testing is necessary. Despite the obvious changes in the relative abundance of individual species, the entire piston core falls within cluster J and Anomalocardia auberiana, Turney and Perkins’ (1972) indicator of the northern subenvironment, is present throughout the piston core. In addition, diversity, evenness, faunal richness, and number of individuals remain relatively constant compared to the other piston cores. Piston Core PK37 Deposition at Pass Key (piston core PK37) (Text- fig. 8) has been relatively rapid, and the piston core represents only the latter half of this century. Brachi- dontes exustus has dominated the assemblage at this site during the period of deposition, and below 26 cm, the relative abundance of B. exustus is fairly constant. Above 26 cm, however, a great deal of fluctuation oc- curs. Seemingly dramatic changes in species domi- nance near the top of piston core PK37 are due to extremely low numbers of individual shells and low faunal richness; which is probably a result of the rapid sedimentation rate. The complete disappearance of all species except Brachidontes exustus and Transennella sp. in the upper 6 cm may be indicative of rapid sed- imentation at the site and/or conditions unfavorable to other species. The increases in Anomalocardia auberi- ana and R-mode XIc group may denote periods of de- creased salinity; this assemblage is characteristic of Lit- tle Madeira Bay, and the 10 cm sample joins cluster J. Piston Core RB19B The piston core from Russell Bank (RB19B) (Text- fig. 9) records approximately 110 years of change at the site. The lower portion of the piston core (~1880— 1922) shows fluctuations in faunal richness and num- bers of individuals, but the relative abundance of the key species does not fluctuate dramatically. Transen- nella sp. is the most abundant species in this portion of the core, but the presence of Brachidontes exustus, Cerithium muscarum, Bittiolum varium and other spe- cies in most of the samples indicates the presence of sub-aquatic vegetation. Significantly, Anomalocardia auberiana and other species from the R-mode XIc as- semblage typical of the northern transition zone, are present before 1922. The presence of these species may indicate lower salinities and possibly the influence of a lower salinity plume. In the modern Florida Bay, a less saline plume of water is sometimes present on the western edge of the basin south of Little Madeira Bay (Text-fig. 3, July 1996; Halley, http:// sofia.usgs.gov/projects/circulation). After 1922, signif- icant changes occur in the relative abundance of the key fauna. Transennella sp. decrease, and Brachidon- tes exustus, Bittiolum varium and other components of the Brachidontes assemblage increase somewhat. After 1942, fluctuations become even more pronounced, un- til approximately 1980 when Brachidontes exustus in- crease dramatically in relative abundance, and all other key species, with the exception of Pteria longisqua- mosa and Modulus modulus, decline. The increase in Brachidontes exustus in the upper 20 cm of the piston core corresponds to an increase in numbers of speci- mens (this is consistent with the findings of Lyons 1998) and a decrease in faunal richness, evenness and diversity. Piston Core BA6A Bob Allen mudbank (piston core BA6A) preserves a record of deposition since approximately 1784. No modern analogue has been identified for the Transen- nella sp. assemblage (cluster L) that dominates the lower portion of piston core BA6A, before 1922 (54 cm). The lowest portion of the piston core (140-158 cm) indicates either a rapidly fluctuating environment, or deposition at the transition zone between a grass bed (indicated by cluster K assemblage) and a low diversity, sparse Transennella sp. habitat. Beginning around 1890 to 1901, Brachidontes exustus becomes a significant component of the molluscan assemblage in piston core BA6A, and around 1901 the relative abundance of Transennella sp. declines and never again constitutes greater than 51% of the assemblage. The Brachidontes assemblage (cluster K), indicative of the presence of sub-aquatic vegetation) dominates the upper portion of piston core BA6A. Beginning in the late-1920’s, Lithopoma americanum, indicative of the more euhaline western environments, is occasionally present at Bob Allen mudbank. Around 1981, Brach- idontes exustus becomes the most dominant species in the piston core. In general, the measures of diversity MOLLUSKS PAST AND PRESENT: BREWSTER-WINGARD ET AL. 229 (faunal richness, evenness, and the Shannon’s diversity index) all fluctuate significantly throughout the depo- sition of this core, and the values for numbers of in- dividuals and faunal richness are lower in piston core BA6A, in comparison to the other piston cores ex- amined. SUMMARY OF SIGNIFICANT HISTORICAL FINDINGS 1) Molluscan assemblages that exist at each piston core locality today, typically existed there throughout the period of deposition represented by the piston cores. Shifts have occurred in the patterns of domi- nance and diversity within each piston core, but the faunal composition has not changed significantly. 2) Piston core T24, at the mouth of Taylor Creek, records gradually increasing salinity, an increase in eu- ryhaline molluscan fauna, and a decline in mesohaline molluscan fauna up core. Anomalocardia auberiana, typical of the northern transition zone, is present throughout the core. 3) Pass Key piston core (PK37), southeast of Little Madeira Bay, shows significant fluctuations in Anom- alocardia auberiana and the other species indicative of the northern transition zone. 4) Between 1913 and 1933, distinctive changes oc- cur in the molluscan assemblage at Russell Bank (pis- ton core RB19B). Anomalocardia auberiana, consis- tently present in low percentages prior to 1922, com- pletely disappears from the site after that time. 5) At Bob Allen mudbank (piston core BA6A) a dramatic change in faunal assemblages occurred be- tween 1890 and 1901, from a Transennella sp. domi- nated assemblage to a Brachidontes exustus dominated assemblage. 6) From approximately 1930 to 1980, Lithopoma americanum, typical of euhaline western and Gulf transition environments, is occasionally present at Bob Allen mudbank (piston core (BA6A). 7) From approximately 1930—1980 dramatic shifts in percent abundance of different species within the Brachidontes assemblage occur at both Bob Allen mudbank and Russell Bank. 8) Beginning around 1980, Brachidontes exustus becomes the dominant mollusc at Russell Bank, and faunal diversity and evenness decline. Similar increas- es in Brachidontes exustus are seen in the upper por- tion of all four piston cores analyzed. CONCLUSIONS Changes in ecosystems take place on many scales, from daily to decadal to millennial. Molluscs generally are tolerant of short-term perturbations in their envi- ronment, but they will respond to seasonal and annual changes in salinity. Thus, changes recorded in mollus- can populations are significant. A comparison of mol- luscan faunal distributions in modern Florida Bay to down-core faunal distributions has revealed important details about the last 100 years of Florida Bay history. All four cores examined show changes during the period of time represented by deposition at the indi- vidual sites, yet only the Bob Allen site recorded a complete change in molluscan assemblages. The mol- luscan fauna that occur throughout the cores are the same fauna that are present at those sites today. Chang- es that have occurred within the cores are fluctuations in patterns of dominance and diversity within a single assemblage, not complete replacement of the assem- blage. For example, the Turbo/Tegula/Columbella as- semblage indicative of more marine conditions has not existed at Bob Allen mudbank or at Russell Bank dur- ing the last 100-200 years. Nor has the northern tran- sitional assemblage, typical of the Little Madeira Bay sites, dominated at Bob Allen or Russell Bank. Even the change that occurs around 1900 at Bob Allen mud- bank does not represent complete replacement of a fauna. We have not identified a modern analogue for the Transennella assemblage that existed at Bob Allen prior to the turn of the century, but we do know that Transennella sp. occur at Bob Allen today. The changes indicated by shifts in dominance pat- terns, however, do suggest the influence of some en- vironmental factors on molluscan fauna in northern, eastern and central Florida Bay. The patterns in core T24 clearly demonstrate increasing salinity at the mouth of Taylor Creek. Freshwater outflow through Taylor Creek has been controlled by water manage- ment during the later half of this century. The change in salinity at this site may be due to water management practices, fluctuations in average annual precipitation, changes in sea level, or a combination of all of these. The record from Pass Key (core PK37) is not as clear, due in part to the rapid sedimentation rates at that site, but fluctuations in the abundance of Anomalocardia auberiana and other typical northern transition species at Pass Key probably reflect fluctuations in salinity. This conclusion is consistent with Lyons’ findings (1996, 1998). The age models for Russell Bank (core RB19B) and Bob Allen mudbank (core BA6A) allow us to compare changes in the molluscan fauna to historical data on human activities and rainfall (Text-figs. 9 and 10). The changes that occur between 1900 and 1910 at Bob Allen and between 1913 and 1933 at Russell indicate a shift toward less stable conditions. The disappear- ance of Anomalocardia auberiana from Russell Bank after 1922 may indicate more saline conditions. It is possible, given the increasing error in the age model with depth, or the possibility of varying sedimentation 230 BULLETIN 361 rates with depth, that these events occurred simulta- neously. During this time period, average rainfall did not fluctuate significantly in southern Florida, but sub- stantial human alteration of the environment occurred with the construction of the Flagler Railroad in the Keys. Given the current data, it is impossible to de- termine if the construction contributed to changes in the molluscan fauna, but evidence indicates that the railroad restricted the natural exchange of water be- tween the bay and the Atlantic (Swart et al., 1996). Between approximately 1930 and 1980, the mollus- can fauna at Bob Allen and Russell both went through a period of fairly rapid and dramatic fluctuations. These fluctuations correspond to a period of relatively dramatic shifts in regional rainfall and to a period of significant alteration of the terrestrial environment with the construction of canals, the implementation of water management practices, and a rapidly growing population. Lithopoma americanum, a typically west- ern Florida Bay euhaline species, is occasionally pre- sent at Bob Allen from approximately 1930 to 1980. The presence of Lithopoma may be indicative of pe- riods of increased salinity or of fluctuating marine in- fluence caused by the environmental perturbations. Beginning around 1980, Brachidontes exustus be- comes the most dominant species at Russell and Bob Allen, and it increases in dominance in the upper por- tion of the cores from Pass Key and Taylor. Brachi- dontes exustus is a euryhaline species that can tolerate diminished water quality, and it is nearly ubiquitous at sites in central and eastern Florida Bay today. The con- centration of this species in the upper portion of all the cores implies that salinity fluctuations have in- creased in the last 20 years, and/or water quality has diminished. Additional studies of the autoecology of molluscan species will refine our knowledge of the environmental parameters that control their distribution and will in- crease their utility as bioindicators. We have estab- lished that the following molluscan species can serve as important biological indicators of conditions in Florida Bay during restoration: Anomalocardia auber- iana, Brachidontes exustus, Cerithidea spp., Pteria longisquamosa, Polymesoda maritima, Turbo casta- nea, Tegula fasciata, and Hydrobiidae. Additional cores from eastern and central Florida Bay are being examined to geographically extend our coverage, and determine if the patterns seen here persist in other ar- eas as well. It is critical for effective restoration of the Florida Bay ecosystem that we understand the dynamics of the system and the degree to which physical, chemical and biological components of the system have varied in the past. Studies of modern fauna and flora provide a means to interpret biological data preserved in cores, and to determine the physical and chemical variations in the environment indicated by the biota. Once the patterns of the past are understood, we can better pre- dict the impact of future change on the environment. REFERENCES CITED Brewster-Wingard, G.L., Ishman, S.E., Willard, D.A., Edwards, L.E., and Holmes, C.W. 1997. Preliminary paleontologic report on cores 19A and 19B, from Russell Bank, Everglades National Park, Florida Bay. U.S. Geological Survey Open-file Report 97-460, 29 pp. Brewster-Wingard, G.L., Ishman, S.E., Waibel, N.J., Willard, D.A., Edwards, L.E., and Holmes, C.W. 1998a. Preliminary paleontologic report on Core 37, from Pass Key, Everglades National Park, Florida Bay. U.S. Geo- Brewster-Wingard, G.L., Ishman, S.E., and Holmes, C.W. 1998b. Environmental Impacts on the southern Florida Coastal Waters: A history of change in Florida Bay. Journal of Coastal Research, special issue 26, pp. 162-172. Brewster-Wingard, G.L. and Ishman, S.E. 1999. Historical trends in salinity and substrate in central Flor- ida Bay: A Paleoecological Reconstruction using modern analogue data. Estuaries, vol. 22, no. 2b, pp. 369-383. Camp, D.K., Lyons, W.G., and Perkins, T.H. 1998. Checklists of selected shallow-water marine invertebrates of Florida. Florida Department of Environmental Protec- tion, Florida Marine Research Institute Technical Report TR-3, 238 pp. Dame, R.F. 1996. Ecology of marine bivalves: an ecosystem approach. CRC Press, Boca Raton, 254 pp. Hazel, Joseph E. 1977. Use of certain multivariate and other techniques in assem- blage zonal biostratigraphy: examples utilizing Cambrian, Cretaceous, and Tertiary Benthic Invertebrates. in Con- cepts and Methods in Biostratigraphy. E.G. Kauffman and J.E. Hazel, eds., Dowden, Hutchinson, & Ross, Inc., Stroudsburg, PA, pp. 187—212. Holmes, C.W., Robbins, J., Halley, R., Bothner, M., Ten Brink, M., and Marot, M. 2001. Sediment Dynamics of Florida Bay Mud Banks on a De- cadal Time Scale. Bulletins of American Paleontology, no. 361, pp. 31—40. Ishman, S.E., Brewster-Wingard, G.L., Willard, D.A., Cronin, T.M., Edwards, L.E., and Holmes, C.W. 1996. Preliminary paleontologic report on Core T-24, Little Ma- deira Bay, Florida. U.S. Geological Survey Open-File Report 96-543, 27 pp. Johns, E., Wilson, D.W., and Lee, T.N. 1999. Surface salinity variability of Florida Bay and southwest Florida coastal waters. Program and Abstracts, 1999 Flor- ida Bay and Adjacent Marine Systems Science Confer- ence, pp. 169-171. MOLLUSKS PAST AND PRESENT: BREWSTER-WINGARD ET AL. 231 Kovach, W.L. 1989. Comparisons of multivariate analytical techniques for use in pre-quaternary plant paleoecology. Review of Palaeo- botany and Palynology, vol. 60, pp. 255-282. 1995. Multivariate Data Analysis. in Statistical Modeling of Quaternary Science Data, D. Maddy and J.S. Brew, eds., Quaternary Research Association, Technical Guide, no. 5, pp. 1-38. Ludwig, J.A. and Reynolds, J.F. 1988. Statistical ecology: a primer on methods of computing. John Wiley & Sons, New York, 337 pp. Lyons, W.G. 1995. Mapping Florida Bay benthic assemblages: using mol- lusks to assess faunal change. Programs and Abstracts, Florida Bay Science Conference, October 1995, Gaines- ville, Florida, Florida Sea Grant, University of Florida, pp. 167-169. 1996. An assessment of mollusks as indicators of environmental change in Florida Bay. Programs and Abstracts, Florida Bay Science Conference, December 1996, Key Largo, Florida, Florida Sea Grant, University of Florida, pp. 52— 54. 1998. Florida Bay molluscan community dynamics: shifting zones in a changing world. Proceedings, Florida Bay Sci- ence Conference, May 1998, Miami, Florida, Florida Sea Grant, University of Miami. 1999. Responses of benthic fauna to salinity shifts in Florida Bay: evidence from a more robust sample of the mollus- can community. Program and Abstracts, Florida Bay and Adjacent Marine Systems Science Conference, November 1999, Key Largo, Florida, pp. 47—5S0. Shannon, C.E., and Weaver, W. 1949. The mathematical theory of communication. University Illinois Press, Urbana, IL. Swart, P. K., Healy, G. F., Dodge, R. E., Kramer, P., Hudson, J. H., Halley, R. B., and Robblee, M. B. 1996. The stable oxygen and carbon isotopic record from a coral growing in Florida Bay: a 160 year record of climatic and anthropogenic influence. Paleogeography, Palaeoclimatol- ogy, Palaeoecology, vol. 123, pp. 219-237. Turney, W.J. and Perkins, B.F. 1972. Molluscan distribution in Florida Bay. University of Mi- ami, Miami, Florida, Sedimenta, vol. III, 37 pp. Wingard, G.L., Ishman, S.E., Cronin, T.M., Edwards, L.E., Wil- lard, D.A., and Halley, R.B. 1995. Preliminary analysis of down-core biotic assemblages: Bob Allen Keys, Everglades National Park, Florida Bay. U.S. Geological Survey Open-file Report 95-628, 35 pp. x c Sy » a ile : t _ mi av “Sen mil 12 nt ‘ ar A eB feet ila Z ere 0u ae a y i ea ee ) sine . | ait 2 e : es | r rs ath ae jo we) Ones fi oe aod } a a 2A . - ée tis o 7 - Tey o6f2 » « : , “ ; : i ikre® @ A +~ nes : va 7 ¢ 4 il rea ieee a =, F eabte 1) AA : y % nei ‘jm Goren O86 . ss a ie e) a Le. jhe a 7 - a pou ‘as ian!’ @F ema te PAE peter | Mie. Se ; : ; ‘ i , v= f > inn ee AR a) <, . , oa(tm ae —s | ¥ > ta » Se” ' - : fh .6i'S,_ eae : > he) mM 52215) 52-15) 0:00 Central Biscayne Bay SPO1 25 39'28 80 16'06 30.25 29.50 4.18 393 SHO 10:23) 150.00 16.83 33.65 50.48 0.00 BB22 25 45'21 80 10'28 30.00 33.80 5.60 458 1.90 0.22 19 0.00 0.00 42.28 42.28 0.00 BB26 25 44'50 80 11'06 29'S 33:40) 555 473 200 O13 26096 8.04 28.30 36.33 0.00 BB34 25 39'03 80 15/33 30.25 32.00 4.34 419 2ALOR OR 200.00 0.00 0.00 0.00 0.00 BB35 25 38/37 80 11/30 30.01 37.00 5.71 449 10) 0:08) 25) 10:00 4.69 0.00 4.69 0.00 BB36 25 35'58 80 14’11 2990) 37-40) 5:82) 4395230) ORS 26 ~=—-0..00 0.00 0.00 0.00 0.00 BB37 25 34'13 80 11/31 29 S45 S/-20) SO 45 1.80 0.08 29 0.00 0.00 0.00 0.00 0.00 South Biscayne Bay BB41 25 28'20 80 17'04 29716 S85 08 O04 SiO 2 aOR ON 2 ee 0.00 0.00 0.27 0.27 0.00 BB42 25 27/23 80 11'59 PENG) ifesK0) SHO} ISS) 1.30 0.24 9 0.00 0.00 0.00 0.00 0.00 BB44 25 24'02 80 15'20 29.67 37.60 5.53 448 ZO O85 5 267510200, 0.00 0.33 0.33 0.00 BB45 25 22'09 80 16/48 29.60 37.40 5.37 458 2.40 0.11 21 0.00 0.00 0.00 0.00 0.00 BB48 25 18'29 80 20'56 29373240 5:38) Als 2.60 0.14 24 0.00 0.32 0.63 0.95 0.00 BBS51 25 15'04 80 24'51 DIZ 2220) ee se 444 1.50 0.26 12 OL00) 0.00 25.00 25.00 0.00 fig. 2; SFWMD, 1994) occur in Central Biscayne Bay. These are supported on substrates including calcareous and quartz sands, calcareous mud, and organic-rich muds (Wanless, 1976). Salinities within Central Bis- cayne Bay range from 32.0 to 37.4 ppt in the open- bay and 29.5 ppt at the discharge of Snapper Creek Canal (Text-fig. 3; Table 1). Average August salinity since 1988 in the open-bay is 35.90 ppt. The coastal regions of Central Biscayne Bay vary significantly de- pendent on point-source freshwater run-off. The north- ern part of Central Biscayne Bay is strongly influenced by the Miami River, which accounts for the high tur- bidity, high nutrient, and high pollutant levels in this region. Further south, Snapper Creek, Coral Gables Waterway, and Cutler Drain have been identified as pollutant point-sources (SFWMD, 1994). However, flushing of these regions occurs on a regular basis due to Government and Norris Cuts. The southern part of Central Biscayne Bay becomes more pristine and in- cludes Biscayne National Park. Significant effects on the ecosystem in this region are localized, many relat- ed to watercraft use such as sewage and solid waste disposal, fuel leakage and _ spillage, scouring of seagrass beds. South Biscayne Bay includes the southern portion of Biscayne National Park and the northern part of the Florida Keys National Marine Sanctuary (Barnes and Card Sounds; Text-fig. 1). Sediments in South Bis- cayne Bay include non-tidal mud banks, calcareous mud, and sands (Wanless, 1976), and they support sea- grass and seagrass with hard-bottom matrix commu- nities (Text-fig. 2; SFWMD, 1994). Salinities range from between 38.5 and 37.3 ppt north of Card Sound, to less than 30 ppt in Barnes Sound with average Au- gust salinity since 1989 in Barnes Sound at 28.80 ppt (Text-fig. 3; Table 1). Although not as severely af- fected by urbanization as the North and Central Bay, Southern Biscayne Bay is affected by channelized freshwater input and nutrient enrichment from the ca- nal systems. In addition, Card and Barnes Sounds are very restricted, thus reducing their flushing cycles. Other factors that influence the ecosystem of South Biscayne Bay are pollutants from adjacent landfills, and propeller BENTHIC FORAMINIFERA: ISHMAN 237 Table 1.—Extended. Boli- Arti- Astro- Boli- __ Boli- vina Boliv- Buli- Buli- Archaias culina Asti- nonion — vina vina pseudo- ina mina Buli- minella_ Cassi- angula- mucro- gerina _ stella- low- pseudo- punc- Boliv- stria-_ margin- mina elegan- dulina Cibi- Clavu- Sample tus nata sp. tum mani plicata tata ina sp. tula ata striata tissima sp. cides sp.lina sp. North Biscayne Bay BBO2 0.00 0.00 0.00 0.00 0.31 0.94 5.66 0.00 4.09 1.89 0.00 1.57 0.00 0.63 0.00 BBO3 0.00 0.00 0.00 0.00 0.63 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 BBO4 15292 0.00 2.42 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 BBOSA 0.00. 0.00 0.00 10.47 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00. BBO9 0.00 0.00 0.00 0.00 0.29 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 BB1O 2.24 eT) 0.00 0.00. 0.00 0.45 0.90 0.00 0.45 0.00 0.00 0.45 1.35 0.00 0.00 BBI1 0.00 0.85 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 BB14 0.00 1.88 0.00 0.00 0.00 0.00 0.00 0.00 1.25 0.63 0.00 0.00 0.00 0.00 0.00 BBIS5 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 BB17 0.33 0.99 0.00 0.00 0.00. 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Central Biscayne Bay SPO1 0.00 0.00 0.63 0.00 0.32 0.00 0.00 0.32 0.00 0.00 0.00 0.32 0.00 0.00 0.00 BB22 0.00 1.68 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 BB26 0.00 0.64 0.00 0.00 1.93 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 BB34 12.58 3.23 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.65 BB35 12.64 2.17 1.08 0.00 0.00 0.00 0.00 0.00 1.81 0.00 0.00 0.36 0.00 0.00 0.00 BB36 32.23 0.66 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.33 0.00 0.00 0.00 0.00 BB37 18.18 4.17 0.00 0.00 0.38 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.89 South Biscayne Bay BB41 26.08 0.27 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 BB42 45.23 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 BB44 32.89 1.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.33 BB45 20.86 1.71 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.00 BB48 1.59 4.76 0.00 0.00 0.32 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 BBS1 0.00 0.82 0.00. 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 the Turkey Point power facility, and propeller scour in METHODOLOGY shallow regions. An additional consideration with respect to the Bis- cayne Bay ecosystem is the impact of ground water. Ground water seepage at the coastal margins and from subsurface springs has been noted historically (Kohout and Kolipinski, 1967). This acts as an additional source of fresh water, but also may provide an addi- tional source of contaminants by pollutant-enriched ground water. A significant source of groundwater dis- charge is apparent along the coastal margin of Central Biscayne Bay (V. Quinones, USGS, personal com- munication). The factors listed above play a primary role in the distribution of aquatic communities within the Bis- cayne Bay ecosystem (SFWMD, 1994). The identifi- cation of the significant factors in controlling the dis- tributions of the Bay’s biogenic components is critical for our interpretation and understanding of the evolu- tion of the Biscayne Bay ecosystem. This paper pre- sents the modern distributions of benthic foraminifera and their environmental controls within Biscayne Bay. A systematic collection of surficial sediment sam- ples from Biscayne Bay was conducted in collabora- tion with Metropolitan Dade County Department of Environmental Resources Management (DERM) dur- ing the months of June and August, 1996. A total of twenty-three localities (Text-fig. 1; Table 1) were sam- pled for surficial sediments using an Eckman Grab sampler. These sites have been sampled monthly start- ing in 1988 (DERM Bay Run Program) for a variety of water-quality variables of which the following are reported herein: salinity, temperature, dissolved oxy- gen, and oxygen-reduction potential (redox) (Table 1). Approximately 100 cubic centimeters (cc) of the up- per two centimeters of the grab samples were disag- gregated and sieved through a 63 um sieve. The great- er than 63 jm size fraction was recovered, dried at 50°C, and analyzed for foraminifera. More than 300 foraminifer specimens were picked randomly using a 45 compartment picking tray and random number ta- ble. Samples not producing greater than 300 specimens N Ww oo Table 1.—Extended. BULLETIN 361 Elphi- Elphi- Elphi- dium Globo- Cribro- Cyclo- dium — Elphi- dium galve- Elphi- Flori- Gaud- cassi- Milio- Milio- stom- — gyra_ Discor- cf. dium galve- stonense dium lus Fursen- ry- dulina linella linella Milio- oides — plan- bis adven- delica- sonense’ mexi-_ poey- auri-_—_koina ina subglo- circu- fich- __ linella Sample sp. orbis — mira um tulum typicum) canum anum _— culus sp. exilis bosa laris teliana labiosa North Biscayne Bay BBO2 0.00 1.26 4.72 0.00 2.52 0.00 0.94 0.00 0.00 2.20 2.83 1.26 1.26 0.00 0.94 BBO3 0.63 0.00 0.00 3.80 0.00 7.28 5.70 0.32 0.95 0.00. 0.32 0.00 0.00 0.00 0.00 BBO4 0.00 0.00 1.38 0.35 0.00 0.00 14.88 0.35 0.35 0.00 0.69 0.00 0.00 0.00 2.08 BBOSA 0.00 0.00 0.00 0.00 0.00 0.00 21.80 0.00 0.87 0.00 0.00 0.00 0.00 0.00 0.00 BBO9 0.00 0.00 0.00 0.00 0.00 0.00 37.97 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 BB10 0.00 0.00 4.48 0.00 8.07 0.00 0.00 0.45 0.00 0.90 0.00 0.45 0.00 0.00 0.00 BBI1 0.00. 0.00 0.00 0.00 0.00 0.28 37.18 0.00 0.00 0.00 0.00 0.00 0.85 0.00 0.00 BB14 0.00 0.00 0.00 0.00 0.00 2.19 35.74 0.00 0.00 0.00 0.00 0.00 0.31 0.00 0.94 BBI5 0.00 0.00 0.00 0.00 1.81 0.00 25.68 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.81 BB17 0.00. 0.00 0.00 0.00. 0.00 0.00 24.75 0.00 0.00 0.00 0.00 0.00 0.00 0.00 10.56 Central Biscayne Bay SPO1 0.00 0.00 0.00 0.00 0.00 25.71 1.27 0.00 0.00 0.00 0.00 0.00 0.32 0.00 0.00 BB22 0.00 0.67 0.00 0.00 0.00 6.04 16.11 0.00 0.67 0.00 0.00 0.00 1.34 0.00 0.00 BB26 0.00 0.00 0.32 0.00 1.61 9.65 13.18 0.00 2.89 0.32 0.00 0.00 1.61 0.00 0.64 BB34 0.00 0.00 0.00 2.26 0.00 0.00 0.00 0.65 0.00 0.00 0.00 0.00 0.65 0.65 1.61 BB35 0.00 0.00 0.00 0.00 0.00 10.83 1.81 0.00 1.81 0.00 0.00 0.36 0.00 0.00 0.00 BB36 0.00 0.00 0.66 0.33 0.00 0.00 2.99 0.00 0.00 0.00 0.00 0.00. 2.99 0.00 1.33 BB37 0.00 0.00 0.00 0.38 0.00 0.00 0.00 1.52 0.00 0.00 0.00 0.00 8.33 0.38 0.00 South Biscayne Bay BB41 0.00 0.00 0.00 0.27 0.00 0.00 2.42 1.08 0.00 0.00 0.00 0.00 11.83 0.00 0.00 BB42 0.00 0.00. 0.00 0.00 1.41 0.00. 0.00 0.00 0.00 0.00 0.00 0.00 1.41 0.00 0.35 BB44 0.00 0.00 1.00 0.00 2.33 0.00 1.00 0.66 0.00 0.00 0.00 0.00 3.99 0.00 0.00 BB45 0.00 0.00 0.00 1.43 8.86 0.00 0.00 2.00 0.00 0.00 0.00 0.00 DEST 0.00 0.86 BB48 0.00 0.00 0.00 0.63 27.30 0.00 Bale), 0.00 0.00 0.00 0.00 0.00 13.02 0.00 0.00 BBS1 0.00. 0.00 0.00 0.00 0.00 0.00 41.80 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.23 were picked of all their specimens and used in this study if they exceeded 50 counts (Table 1). The fora- minifera were identified based primarily on Bock (1971) and Poag (1981), counted, and species counts were standardized to percent of total assemblage (Ta- ble 1) and used as such in the quantitative analyses. Because the results of the analyses presented here are the basis on which future downcore paleoenvironmen- tal analyses will be interpreted, total assemblage data is presented. This is consistent with the findings of Scott and Medioli (1980) who concluded that total as- semblage data more accurately represent prevailing modern conditions and are more useful for paleoen- vironmental studies. The foraminiferal data were analyzed using two sta- tistical techniques, hierarchical cluster analysis and principal components analysis (PCA). The hierarchical clustering method, complete linkage of the Pearson correlation similarity coefficient was applied to the fo- raminiferal data to identify distinct sample groupings (Q-mode) and foraminiferal assemblages (R-mode). Q- mode varimax principal component analysis of the Pearson correlation similarity matrix was used to de- termine the robustness of the foraminiferal groupings defined in the cluster analyses and to quantify the data in multi-dimensional space, which places environmen- tal constraints on the faunal distributions. BENTHIC FORAMINIFERAL RESULTS A total of 69 taxa of benthic foraminifers common to the North American southeast coast and Gulf of Mexico were identified from the Biscayne Bay modern sediment samples (Table 1). Species diversity, as mea- sured using Simpson’s index (Simpson, 1949), ranged from 0.080 to 0.493. Simpson’s index is useful in that it identifies dominance patterns within the data. Com- bined with the number of species present the Simp- son’s index should reflect low diversity, high domi- nance assemblages associated with stress conditions and low dominance, high diversity assemblages asso- ciated with normal marine conditions. Rotaliid forms dominate the foraminiferal assem- blages with agglutinated taxa constituting a minor component in most of the assemblages. Species dom- inance varies considerably throughout the Bay with Ammonia parkinsoniana and Elphidium galvestonense BENTHIC FORAMINIFERA: ISHMAN 239 Table 1.—Extended. Quin- — Quin- Quin- Nodo- Nubecu- Patel- Pseudo- Pyrgo quelo- quelo- Quin- — quelo- bacular- Nodo- Nonio- laria lina Penero- clave- Pyrgo sub- culina culina — quelo- — culina iella sarl- nella luci- corru- plis Plank- lina ~~ denti- Pyrgo_ sphaer- agglu- bos- culina _ poly- Sample sp- idae sp. fuga gata proteus tonic. gracilis culata serrata ica tinans ciana poeyana gona North Biscayne Bay BBO2 0.00 0.94 8.18 0.00 0.31 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4.72 1.26 0.00 BBO3 0.00 0.00 0.00 0.00 0.00 0.00 0.63 0.00 0.00 0.00 0.32 0.00 0.63 0.63 0.63 BBO4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 AG Sita 1.73 0.35 2.08 BBOSA 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.03 0.29 1.45 0.87 0.00 BBO9 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.29 0.29 1.45 0.29 BB1O 0.00 0.00 0.00 0.00 0.00 0.45 0.00 0.00 0.00 0.00 0.00 1.35 5.38 2.24 0.90 BBI1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.28 0.85 0.00 0.00 0.00 BB14 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.94 0.00 0.00 0.31 BBI5 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.30 0.91 0.00 1.21 0.00 BB17 0.00 0.00 0.00 0.00 0.33 0.00 0.00 0.00 0.00 0.00 0.00 0.66 0.33 0.66 0.00 Central Biscayne Bay SPO1 0.00. 0.00 0.00. 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.95 BB22 0.00 0.00 0.00 0.00 0.00 1.68 0.00 0.00 0.00 0.00 4.03 235 5.70 1.34 0.00 BB26 0.00 0.00 0.00 0.00 0.00 0.32 0.32 0.00 0.00 0.32 1.29 0.64 6.11 4.18 By Py) BB34 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.26 0.00 6.13 3.87 1.61 3.87 3.87 BB35 0.00 0.00 0.00 0.36 0.00 0.00 0.00 0.00 0.00 0.00 0.72 6.14 9.03 8.66 5.05 BB36 0.00 0.00 0.00 0.00 0.00 2.66 0.00 0.00 0.00 0.33 0.33 2.99 3.32 10.63 7.97 BB37 0.00 0.00 0.00 0.00 0.00 7.58 0.00 1.52 0.38 0.76 0.76 3.41 3.41 3.03 3.79 South Biscayne Bay BB41 0.00 0.00 0.00 0.00 0.00 1.61 0.00 0.00 0.27 0.00 25 2.69 4.03 5.38 8.06 BB42 0.00 0.00 0.00 0.00 0.00 8.13 0.00 0.00 0.00 0.35 2.83 8.48 2.83 2.83 4.59 BB44 0.33 0.00 0.00 0.00 0.00 1.00 0.00 0.00 0.33 0.00 199 6.31 S52 6.31 3.65 BB45 0.00 0.00 0.00 0.00 0.00 2.00 0.00 0.00 0.00 0.00 3.43 2.00 7.43 6.86 6.86 BB48 0.00 0.00 0.32 0.32 0.00 0.32 0.00 0.00 0.63 0.00 0.32 0.63 18.41 8.89 2.54 BBS1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.23 4.51 0.00 TAS 2.46 constituting over 50% of the fauna in much of North- ern Biscayne Bay and Barnes Sound where the Simp- son’s index range from 0.114 to 0.493. Conversely, Archaias angulatus is dominant (up to 45%) in sam- ples collected from the open regions of Biscayne Bay where Simpson’s index averages ~0.011. Other cal- careous hyaline forms include Bolivina spp., Elphi- dium delicatulum, Rosalina floridana, and R. globu- laris. Common miliolids include Articulina mucrona- ta, Miliolinella circularis, M. labiosa, Pyrgo sub- sphaerica, Quinqueloculina agglutinans, Q. bosciana, Q. poeyana, Q. polygona, Q. seminula, Q. tenagos, and Triloculina spp. Soritids present are Archaias an- gulatus, Peneroplis proteus, and Sorites marginalis. Agglutinated taxa in Biscayne Bay include Ammoba- culites sp., Clavulina tricarinata, Pseudoclavulina gracilis, Textularia candeiana, T. conica, and Tro- chammina spp. Results of the quantitative analyses of the benthic foraminifer data are shown in Text-figure 4 and Table 2. Q-mode cluster analysis defines two sample groups or biotopes (Text-fig. 4a) with two sample outliers. Biotope one consists of samples from Central and northern South Biscayne Bay (BB34, BB35, BB36, BB37, BB41, BB42, BB44 and BB45; Text-fig. 4a) and represent open-marine conditions. The second bio- tope consists of samples from restricted environments or regions greatly effected by point-source freshwater input (SPO1), North Biscayne Bay, and Barnes Sound (BB3, BB4, BB5A, BB9, BB10, BB11, BB14, BB1I5, BB17, BB22, BB26, BB51 and SPO1; Text-fig. 4a). One outlier sample, BBO2, is from Dumbfoundling Bay, the northernmost sample locality. Sample BB48 is the second outlier and is from Card Sound, Southern Biscayne Bay. R-mode cluster and principal components (PC) anal- yses result in the definition of four major groups of benthic foraminifers or assemblages (Text-fig. 4b). The first group, Cluster 1, contains several significant spe- cies including Peneroplis proteus, Triloculina spp., Miliolinella circularis, Articulina mucronata, Quin- queloculina subpoeyana, and Q. bosciana (Text-fig. 4b) that have high positive PC1 and PC4 loadings (Ta- ble 2). Cluster 2 contains Quinqueloculina polygona, Q. agglutinans, Q. tenagos, Q. poeyana, Archaias an- gulatus, and Rosalina floridana that have high positive 240 Table 1.—Extended. BULLETIN 361 Quin- Spiro- Quin- quelo- Quin- Rosa- —_Rosa- sigmot- Stain- Trilo- Trilo- Trilo- quelo-culina’ quelo- Recto- Recur- lina lina lina Spirolo- Sorites forthia culina culina Trilo- culina culina sub- culina bolivina voides flori-— globu- antil- culina margin- compla- line-__ plac-_culina _ tricar- Sample seminula poeyana tenagos advena _ sp. dana laris larum sp- alis nata iana iana_ rotunda inata North Biscayne Bay BBO2 27.67 0.00 0.00 0.00 0.00 O75 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.20 BBO3 4.11 0.00 6.96 0.32 0.32 222. 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.22 BBO4 0.69 0.00 1°73 0.00 0.00 2.08 0.00 0.00 0.00 0.00 0.00 0.35 0.00 0.69 8.30 BBOSA 1.45 0.00 0.58 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 BBO9 2.32 0.00 1.45 0.00 0.00 0.29 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5:22 BB1O 17.94 0.00 4.48 0.00 0.00 6.73 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.45 3.59 BBII1 0.85 0.00 3.94 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.41 3.94 BBI4 3.45 0.00 4.39 0.00 0.00 0.63 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.31 0.63 BBI15 1.81 0.00 0.30 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.30 0.00 BBI7 0.00 0.00 AES) | 0.00 0.00 0.00 132 0.33 0.00 0.00 0.00 0.00 0.00 0.00 4.62 Central Biscayne Bay SPO1 13.02 0.00 0.95 0.00 0.00 2.54 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 ep) BB22 7.38 0.00 1.34 0.00 0.00 2.35 0.00 0.00 0.00 0.34 0.00 0.67 0.00 1.34 2.68 BB26 6.43 0.00 0.32 0.00 0.00 1.61 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4.50 BB34 0.00 0.00 8.71 0.00 0.00 20.97 0.00 0.32 0.00 0.00 0.00 0.65 0.00 0.00 16.13 BB35 7.58 0.00 0.36 0.00 0.00 6.50 0.00 0.00 0.00 0.36 0.72 1.08 1.44 1.08 12.64 BB36 13.62 0.00 1.00 0.00 0.00 1.99 0.00 0.00 0.66 0.33 0.00 0.33 0.00 0.66 8.64 BB37 0.76 1.89 9.09 0.00 0.00 9.47 0.00 1.89 1.14 0.76 0.00 7.20 1.89 1.14 1.14 South Biscayne Bay BB41 8.87 0.00 1.88 0.00 0.00 4.57 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.27 12.90 BB42 8.13 0.00 2.12 0.00 0.00 2.12 0.00 0.00 0.00 0.35 0.00 0.00 0.35 0.00 1.06 BB44 4.65 0.00 2.33 0.00 0.00 2.33 0.00 0.00 0.00 0.00 0.00 0.66 0.00 2:33 12.96 BB45 5.71 0.00 2.29 0.00 0.00 3.71 0.00 0.00 0.00 0.29 0.00 0.00 0.00 0.29 17.71 BB48 2.54 0.00 0.32 0.00 0.00 5.71 0.00 0.95 0.00 0.00 0.00 0.00 0.00 2.86 3.49 BBS51 10.25 0.00 0.00 0.00 0.00 2.87 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.64 PC3 and PC4 loadings (Text-fig. 4b, Table 2). The third cluster includes Bolivina spp., Bulimina margin- ata, Buliminella elegantissima, and Fursenkoina sp. that have high PC2 loadings (Text-fig. 4b, Table 2). The fourth cluster is composed predominantly of Am- monia parkinsoniana, Elphidium galvestonense, and Ammobaculites exiguus that are represented by high negative PC3 and PC4 loadings (Text-fig. 4b, Table 2). In the R-mode principal components analysis the first four principal components explain 94 percent of the variance in the data set (Table 2). High positive and negative (greater than 0.5 and —0O.5) principal component one (PC1) and principal component four (PC4) scores were obtained by foraminiferal species common to normal marine salinities and found on the continental shelf of the southeastern seaboard of the United States (Schnitker, 1971). Several of these spe- cies also are associated with epiphytal habitats. Spe- cies with high principal component two (PC2) scores are common to areas with high surface productivity and organic-rich, fine-grained sediments. Principal component three (PC3) contains species with high pos- itive and negative scores that have specific salinity preferences. High negative scores are associated with the species Ammonia parkinsoniana and Elphidium galvestonense, taxa associated with salinities ranging from 5 to 25 parts per thousand (ppt) in the south Florida region. Foraminifera associated with subtrop- ical to tropical marine conditions (salinities ~ 35 ppt) have high positive PC3 scores. DISCUSSION Few studies have considered the distribution of fo- raminifera within Biscayne Bay. Bush (1958) present- ed a descriptive account of benthic foraminifers from Biscayne Bay by defining thirteen biotopes. Cole (1972) observed benthic foraminifera from a specific locality and attributed test deformation within benthic foraminiferal populations to thermal stress associated with power plant discharge. Benthic foraminiferal studies from Florida Bay (Bock, 1971; Rose and Lidz, 1977: Lidz and Rose, 1989) showed foraminiferal dis- tributions associated with physiographic features and salinity conditions within the Bay. Results of the ben- thic foraminiferal analyses presented herein indicate BENTHIC FORAMINIFERA: ISHMAN 241 Table 1.—Extended. Textu- Textu- Trocham- Trocham- Valvulin- laria laria mina Trocham- mina Unident- Uvigerina Valvulina eria Wiesner- Sample candeiana — conica inflata mina sp. squamata ified sp. sp. laevigata ella sp. Counts North Biscayne Bay BBO2 0.31 0.00 0.00 0.00 0.00 0.00 0.94 0.00 0.00 0.63 318 BBO3 0.00 0.00 6.96 0.00 0.00 0.00 0.00 0.00 0.00 0.00 316 BBO4 DTT 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 289 BBOSA 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 344 BBO9 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 345 BB1O 0.00 0.45 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 223 BBI1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 855 BB14 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 319 BBI5 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 331 BB17 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 303 Central Biscayne Bay SPOL 0.00 0.00 0.00 0.00 0.32 0.00 0.00 0.00 1.59 0.00 315 BB22 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 298 BB26 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.64 311 BB34 0.00 0.00 0.00 0.00 0.00 0.00 0.00 9.35 0.00 0.00 310 BB35 0.00 0.72 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Die BB36 0.00 0.66 0.00 0.00 0.00 0.00 0.00 1.00 0.00 133 301 BB37 0.00 3.79 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 264 South Biscayne Bay BB41 0.00 0.00 0.00 0.27 0.00 0.00 0.00 4.84 0.00 0.00 372 BB42 0.00 0.00 0.00 0.00 0.00 0.00 0.00 7.42 0.00 0.00 283 BB44 0.00 0.00 0.00 0.00 0.00 0.33 0.00 ja 0.00 0.33 301 BB45 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.14 0.00 0.00 350 BB48 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 315 BBS1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.41 0.00 0.00 244 distinct distribution patterns associated with salinity and productivity. The easiest explained grouping is Cluster 4, with species having high negative PC3 and PC4 scores, Am- monia parkinsoniana, Elphidium galvestonense, and Ammobacculites sp. are interpreted as being controlled by salinity. Studies from Florida Bay (Rose and Lidz, 1977; Lidz and Rose, 1988; Brewster-Wingard and Ishman, 1999) and the Gulf Coast (Poag, 1981) indi- cate that these taxa are dominant in low salinity (<25 ppt) environments. These taxa are dominant in the samples that represent Biotope 2, samples from North Biscayne Bay, the outflow from Snapper Creek (SPO1), and Barnes Sound, areas of restricted environ- ments or near point-source freshwater input (Text-fig. 5) where salinities less than 35 ppt persist throughout the year. The distribution of these taxa in Biscayne Bay is consistent with their distribution in Florida Bay and other regions. Conversely, Clusters | and 2 are composed of taxa associated with more normal marine conditions (salin- ities ~35 ppt), Articulina mucronata, Archaias angu- latus, E. delicatulum, M. circularis, P. proteus, Q. po- lygona, Q. agglutinans, Q. bosciana, Q. poeyana, Q. subpoeyana, Q. tenagos, T. lineiana, T. rotunda, T. tricarinata, and S. antillarum. These taxa comprise the assemblages found in Biotope | from Central and northern South Biscayne Bay (Text-fig. 5). Several of these taxa, A. mucronata, T. lineiana, Q. bosciana, Q. poeyana, and Q. polygona in Cluster | are commonly associated with normal marine conditions on the southeastern U.S. continental shelf (Schnitker, 1971; Murray, 1991). In addition, at least two of these spe- cies, M. circularis and P. proteus, have epiphytal hab- itats in lagoonal environments (Brasier, 1975a). The species representing these two clusters have high pos- itive PC1, PC3, and PC4 scores. This indicates that the distribution of these species is partially controlled by normal marine salinity and the presence of seagrass. However, it may also be that the distinction between Clusters | and 2 represents a separation between a Central Biscayne Bay assemblage (1), influenced by an inflow of Atlantic shelf water, and a more southerly assemblage (2) with greater affinities to higher salinity assemblages found in Florida Bay. This pattern is con- sistent with the molluscan distributions in Biscayne 242 BULLETIN 361 Dumbfoundling Bay Salinity (ppt) REBE 1988 1989 1990 1991 1992 1993 1994 1995 1996 Yes North Bay Port of Miami Salinity (ppt) 24 _ 1988 1989 1990 1991 1992 1993 1994 1995 1996 Central Bay Year South Bay ca = = 2 = Ss a 1 E 1988 1989 1990 1991 1992 1993 1994 1995 1996 & Year ATLANTIC OCEAN Text-figure 3—Map of the Biscayne Bay region of South Florida showing August 1988 through 1996 salinity distributions in parts-per- thousand (ppt). The salinity contours represent August 1996. BENTHIC FORAMINIFERA: ISHMAN 243 BB34 B. striata BB3S Sea BB45 @) See ae = » graciis 1B aon r T.conica Cluster 1 Bioto e 1 pirosigmoilina sp BB36 P P ipretei BB42 A, mur ata % antillarum M. Le ae ected BB48 Q. bosciana BBO2 x 2 eae ricarinata SPO1 T tricarinata Q. polygona BBO3 a) poeyanaltendeos / ti BB26 Q. agelutinads BB22 La ese Cluster 2 3510 | hii BBO4+ fa | Biotope 2 Hees a BBSA | | Q. seminula inxs acta eaten : BBIS iBone: Cluster 3 BB17 (alae ee Bicpeantisiime BBO9 & | | | Ammobatulites sp. ~ , BB1I ® | een LES REA) ma Cluster 4 BBI4 & | sas sae au aio: | | . globularis isso D) S33 |) Aupartnconicna BANNER NESE as SS aa SS Se. el E. galvestonenee = a | nen me ie U 5 : 5) ge ees FO : 0.0 0.5 1.0 LS 2.0 Distances * Distances a Text-figure 4.—Dendrograms showing the results of the (a) Q-mode and (b) R-mode cluster analyses. Bay that show much stronger affinities to Atlantic mar- gin faunas than Florida Bay faunas (Brewster-Win- gard, USGS, personal communication). Cluster 3 contains an assemblage that has high PC2 scores (Table 2), is restricted to one sample from Bis- cayne Bay, BBO2, and represents one of the outliers on the Q-mode cluster (Text-fig. 4a). It is distinguished by the only occurrence of Bulimina marginata, Boli- vina spp., and Fursenkoina sp. in Biscayne Bay. Mor- phometric studies (Bernhard, 1986; Corliss and Chen, 1988) indicate that bolivinids are associated with or- ganic rich, low oxygen environments. Their distribu- tions are commonly associated with organic-rich sed- iments, as is B. marginata in the Gulf of Mexico (Phle- ger, 1951), South Atlantic (Mackensen ef al., 1993), and eastern Pacific (Phleger and Soutar, 1973). Sample BBO2 is from the northernmost part of Biscayne Bay, Dumbfoundling Bay. This region is characterized by high chlorophyll-a values, particularly at site BBO2. Canal input to North Biscayne Bay contains the high- est concentrations of dissolved nitrates and phosphates in all of Biscayne Bay (Lietz, WRD, USGS personal communication). Other data indicate that North Bis- cayne Bay is a region of high organic sedimentation (Wanless er al., 1984). Wanless et al. (1984) show the highest concentration of diatoms in North Biscayne Bay for a period from March 1982 through August 1983, with concentrations exceeding 600 10*/liter during November 1982. These values are an order of magnitude greater than those observed in South or Central Biscayne Bay, and are somewhat reflected in the high weight percent total organic content (up to 29 percent) reported for North Biscayne Bay sediments (Wanless et al., 1984). However, the coastal regions in Central and South Biscayne Bay are also rich in or- ganic content (vegetative material) therefore making it necessary to distinguish organics from phytoplankton productivity versus macrofloral contribution. The dis- tribution of the boliviniid taxa in Biscayne Bay indi- cates a relationship to phytoplankton productivity in Dumbfoundling Bay. The benthic foraminiferal assemblages described in this study of Biscayne Bay foraminifera are somewhat consistent with previous results from Biscayne Bay, Florida Bay, and similar environments in the western Atlantic (Bush, 1958; Brasier, 1975a; Brasier, 1975b; Rose and Lidz, 1977) that emphasize substrate as a con- trolling factor. Brasier (1975a, 1975b) studied forami- niferal ecology and distributions in the environments surrounding Barbuda, West Indies, concluding that sub- strate was a strong controlling factor in the distribution of benthic foraminiferal assemblages. His three domi- nant substrate conditions were stable back-reef facies, consisting of fine-grained sediments that support a sea- grass community in relatively clear water; mobile, bio- clastic calcarenite substrate where diversity increases with increased seagrass density; and a high-energy, mo- bile, coarse bioclastic fore-reef substrate. Bush (1958) described thirteen benthic foraminiferal biotopes from Biscayne Bay: open-water east of the keys, tidally ef- fected channel areas, turbulent shallow shoals, open- water shallow shoals, grass covered shoals, well-sorted 244 BULLETIN 361 Table 2.—Result of the R-mode principal components analysis of the Biscayne Bay foraminiferal data showing the first 4 varimax rotated principal components, which account for 59% of the variance in the data. Principal component scores Taxon PCl Trochammina conica —0.964 Triloculina lineiana —0.938 Spiroloculina sp. —0.907 Sorites marginalis —0.874 Triloculina planciana —0.850 Spirosigmoilina antillarum —(0.745 Peneroplis proteus —0.741 Clavulina tricarinata —0.602 Fursenkoina sp. 0.082 Bolivina spp. 0.043 Buliminella elegantissima 0.051 Nonionella sp. 0.057 Bulimina marginata 0.065 Quinqueloculina seminula 0.072 Cyclogyra planorbis 0.052 Discorbis mira 0.090 Valvulina sp. O.111 Ammonia parkinsoniana 0.326 Triloculina tricarinata 0.135 Quinqueloculina polygona —0.261 Pyrgo subsphaerica 0.106 Archaias angulatus —0.318 Quinqueloculina poeyana/tenagos —0.385 Pyrgo denticulata 0.072 Rosalina floridana =OIS)5) Quinqueloculina agglutinans —0.279 Elphidium galvestonense 0.240 Elphidium poeyanum —0.420 Miliolinella fichteliana (0S Elphidium delicatulum 0.176 Articulina mucronata —0.377 Quinqueloculina bosciana 0.002 Miliolinella circularis —0.267 Triloculina rotunda —0.123 Textularia candeiana 0.053 Amphistegina lessonit 0.047 Ammobaculites sp. 0.104 Miliolinella labiosa 0.086 Elphidium advenum 0.112 Wiesnerella sp. —0.071 Rosalina globularis 0.044 PC2 PC3 PC4 —0.002 —0.003 0.153 0.044 0.056 0.147 0.004 0.041 0.068 0.038 0.194 0.017 0.020 0.052 0.108 0.097 0.013 0.509 0.053 0.295 —0.100 0.093 0.369 0.186 —0.965 —0.084 0.024 —0.963 SOS 0.024 —0.961 —0.092 0.016 —0.942 —0.058 0.012 —0.891 —0.124 —0.016 —0.848 0.011 —0.058 —0.841 —0.095 —0.002 —0.826 —0.007 —0.041 0.116 0.821 —0.095 0.237 —0.800 —0.234 0.106 0.787 0.027 0.102 0.743 —0.006 0.206 0.740 —0.141 0.082 0.718 —0.265 0.187 0.641 0.409 O.L1S 0.640 0.343 —0.318 0.629 0.317 0.148 0.617 —0.243 0.330 —0.615 —0.204 0.096 0.527 0.127 0.093 0.506 0.173 —0.053 0.078 0.787 0.132 0.248 0.771 —0.161 0.266 0.713 0.040 0.292 0.603 0.122 0.101 0.588 —0.053 0.089 —0.481 0.052 0.095 —0.479 —0.077 —0.030 —0.471 0.129 —0.182 —0.174 O.151 0.354 0.160 —0.425 0.124 —0.141 0.159 —0.265 —0.046 sediment substrate, near-shore surface runoff, Bay deep- water axis, north bay, northeast bay, eastern margin, western bay, and southwestern bay. Cluster | is consis- tent with the composition of the back-reef biofacies of Brasier (1975a) and the channel areas, shallow shoals, vegetated shallow shoals, and well-sorted shoals bio- topes of Bush (1958). These faunal associations are dominated by miliolids, particularly Miliolinella circu- laris that is associated with seagrass in this environment (Brasier, 1975a). Cluster 2 contains taxa similar to the mobile substrate biofacies of Brasier (1975a) and deep- water bay axis biotope of Bush (1958), and is charac- terized by A. angulatus, Q. agglutinans, and E. poey- anwm. In addition to the similarity in species compo- sition, the Simpson’s index decreases and species di- versity of this assemblage increases as the density of seagrass increases and sediments become finer grained. Both Biscayne Bay assemblages contain species A. an- gulatus and P. proteus, which are considered epiphytal and commonly associated with Thalassia (Lee and Zucker, 1969; Levy, 1991; Steinker and Steinker, 1976). The spatial distribution of species such as A. angulatus and E. poeyanum in the current study may differentiate a seagrass-dominated substrate from a sediment domi- nated substrate, but does not indicate an absence of sea- grass. to iS Nn BENTHIC FORAMINIFERA: ISHMAN ATLANTIC OCEAN : ) = J ~ Biotope | Florida y , Biotope 2 Bay Ys Text-figure 5.—Map of the Biscayne Bay region of South Florida showing the distribution of the biotopes in Biscayne Bay: Biotope | (dark shade) represents marine salinities; Biotope 2 (light shade) represents restricted circulation and oligohaline to polyhaline conditions. 246 BULLETIN 361 Ammonia parkinsoniana and Elphidium galvesto- nense are dominant taxa (>25%) in samples from Bio- tope 2 in Northern Biscayne Bay, and Barnes Sound, Southern Biscayne Bay. The dominance of these taxa indicates conditions of high variability and relatively low salinity conditions. This assemblage is similar to the Ammonia-Elphidium assemblage (A-E assemblage) described from the Gulf of Mexico (Poag, 1981) and northeastern Florida Bay (Brewster-Wingard et al., 1996). The A-E assemblage is associated with oligo- to mesohaline (O0.5—18 ppt) environments. In contrast, benthic foraminiferal assemblages from the Gulf Coast (Poag, 1981) and Florida Bay (Brewster-Wingard et al., 1996) that are dominated by miliolid taxa are as- sociated with polyhaline to euhaline (18 to 35 ppt) conditions. Similarly, Brasier (1975a) found strong as- sociations between foraminifera and salinity, where low salinity habitats typically contained Ammonia bec- carii, and hypersaline habitats were dominated by mil- iolids Quinqueloculina spp. and Triloculina spp. SUMMARY Benthic foraminiferal analyses of 23 surficial sedi- ment samples, collected from Biscayne Bay, indicate four distinct foraminiferal assemblages identified using cluster and principal components analyses. The Cluster 4 assemblage is dominated by Ammonia parkinsoni- ana and Elphidium galvestonense, represents oligo- haline to polyhaline conditions in areas where circu- lation is restricted and point-source freshwater input occurs. The Cluster 3 assemblage, characterized by the presence of Bolivina spp. and Bulimina marginata, represents high nutrient input and organic flux to the substrate. The Cluster 2 assemblage is dominated by miliolids with Archaias angulatus and Elphidium poeyanum significant faunal components with affini- ties to Florida Bay foraminiferal assemblages. The Cluster | assemblage also is dominated by miliolids in which Articulina mucronata and Peneroplis proteus are significant components. This assemblage has affin- ities with Atlantic shelf assemblages. The latter two assemblages represent polyhaline to euhaline condi- tions where seagrass is an important factor. 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VI, p. 55. Schnitker, D. 1971. Distribution of foramininfera on the North Carolina con- tinental shelf. Tulane Studies in Geology and Paleontol- ogy, vol. 8, pp. 169-215. Scott, D.B., and Medioli, F.S. 1980. Living vs. total foraminiferal populations: their relative usefulness in paleoecology. Journal of Paleontology, vol. 54, pp. 814-831. SFWMD 1994. Surface Water Improvement and Management Plan for Biscayne Bay. Lower East Coast Planning Division South Florida Water Management District, West Palm Beach, FL, 139 pp. Simpson, E.H. 1949. Measurement of diversity. Nature, vol. 163, p. 688. Steinker, P.J., and Steinker, D.C. 1976. Shallow-water foraminifera, Jewfish Cay, Bahamas. Mar- itime Sediments Special Publication, vol. 1, pp. 171-180. Wanless, H.R. 1976. Geological setting and Recent sediments of the Biscayne Bay region in Biscayne Bay: Past, Present and Future, Thorhaug, L.P. and Volker, A., eds., University of Miami Sea Grant, Miami, FL, pp. 1-32. Wanless, H.R., Cotrell, D., Parkinson, R., and Burton, E. 1984. Sources and circulation of turbidity Biscayne Bay, Flori- da. Unpublished report to Dade County and Florida Sea Grant, 499 pp. = ¢ ve - ale i 5 at 1h Ap 5 ' & : Ta ie : . e 7 _ eine te a e . a > 7 | % , = pie AH sm Lhe CHAPTER 12 OSTRACODE SHELL CHEMISTRY AS A PALEOSALINITY PROXY IN FLORIDA BAY GARY S. DWYER Division of Earth and Ocean Sciences Duke University Durham, North Carolina 27708 AND THOMAS M. CRONIN U. S. Geological Survey 926A National Center Reston, Virginia 20192 ABSTRACT We investigated the use of ostracode metal/calcium ratios (Mg/Ca, Sr/Ca, and Na/Ca) to reconstruct the salinity history of central Florida Bay from its sedimentary record. We first developed provisional partition coefficients (Kp yj. and Ky.s,) from the average me/Ca ratio for modern Florida Bay water and 171 modern shells of Loxoconcha matagordensis at a mean Florida Bay water temperature of 26.5°C. Trends in Mg/Ca ratios for L. matagordensis and Peratocytheridea setipunctata from radiometrically dated sediment cores from Russell Bank, Park Key, and Bob Allen Keys appear to provide a reasonable estimate of Florida Bay salinity history for the past 130 years. The most complete Mg/Ca record from Russell Bank extends back to 1875 and shows a good correspondence between estimated paleosalinity and measured annual rainfall in south Florida. Paleosalinity estimates for the Russell Bank area range from ~13 to ~55 ppt. Estimates for the post-1950s period are comparable to instrumental mea- surements of salinity near the Russell Bank site. The overall record indicates a decadal-scale variability in salinity in which large amplitude shifts in ostracode Mg/Ca ratios with high Mg/Ca (higher salinity) values corresponding to periods of low rainfall from ~1895 to ~1920 and from 1940 to present. The intervening 20 years (~1920—1940) are characterized by relatively low amplitude shifts in Mg/Ca and rainfall. Since 1950, periods of high salinity (~45 to ~55 ppt) occur during each decade. Prior to 1940, salinity never exceeded ~45 ppt and generally remained below 40 ppt, despite evidence in the rainfall record of dry intervals in the early 1900s equivalent to those of the last 50 years. Salinity minima associated with the decadal-scale oscillations range from ~15 to ~25 ppt. Four of the five extreme low values (~1915, ~1940, times of strongly negative values of the Southern Oscillation Index, that is, El Nino conditions that bring anomalously high winter rainfall in the southeastern U.S. These results support the hypothesis that seasonal and decadal-scale salinity fluctuations are a natural part of the Florida Bay ecosystem, and that these fluctuations are largely a function of natural variability of regional climate (rainfall). The relatively low peak salinity values associated with apparent dry periods in the early 1900s suggests that, since ~ 1950, anthropogenic factors ~1983, ~1998) appear to correspond with may have played a role in the magnitude of the salinity fluctuations in more recent times. INTRODUCTION Salinity variations play an important role in the physical and biogeochemical processes of estuaries and marine embayments. Within these marginal ma- rine settings, either directly or indirectly, spatial and temporal variations in salinity control turbidity and sedimentation, the distribution of dissolved inorganic and organic constituents, and the distribution and abundance of flora and fauna (reviews in Chester, 1990; Berner and Berner, 1996). Recently, Florida Bay—an estuarine-like, shallow marine embayment that receives significant terrestrial runoff from peninsular Florida—has experienced dra- matic ecosystem changes including sea-grass die-offs, decreases in populations of fishes, pink shrimp, and water birds, and increased blooms of algae (Boesch er al., 1993). At the same time, the frequency and inten- sity of hypersaline events in Florida Bay have appar- ently increased leading to the hypothesis that the re- cent ecosystem changes in the bay have resulted from changes in salinity (MclIvor ef al., 1994). Further, it has been hypothesized that salinity variations within the bay are the result of anthropogenic factors, such as diversion of freshwater runoff from the Everglades, freshwater that would otherwise have drained into Florida Bay (Mclvor ef al., 1994). Hydrologic mod- eling studies support this hypothesis, showing that 250 BULLETIN 361 large-scale decreases in freshwater influx to Florida Bay from the Everglades will lead to extreme fluctu- ations in salinity and an increased occurrence of hy- persaline conditions, especially in near-shore sub-ba- sins of central and northeastern Florida Bay (Fennema et al., 1994). While it is clear from historical accounts that the bay has experienced hypersaline events in the last few decades, very little is known about the long-term sa- linity history of Florida Bay and whether or not the recent events of hypersalinity are unprecedented prior to human activities in South Florida. Unfortunately, only short and discontinuous instrumental records of Florida Bay salinity have been obtained over the last 50 years, and only anecdotal salinity data exists prior to this time. In place of instrumental data, longer re- cords of Bay salinity have been reconstructed from fossil material deposited and preserved in the bay. For example, on the basis of an oxygen isotopic (6'5O) record from a Florida Bay coral, Swart et al. (1996) postulated that there has been no major long-term in- crease in salinity in Florida Bay, implying that the events of hypersalinity are part of the natural variabil- ity of Florida Bay. They concluded, however, that fol- lowing construction of the Miami-to-Key West rail- road (1905-1910) there was a decrease in the vari- ability of the 6'SO signal, suggesting a stabilization of salinity conditions in Florida Bay during the period 1905-present relative to 1825—1905. Brewster-Wingard et al. (1998) and Brewster- Wingard and Ishman (1999) interpreted molluscan and foraminiferal assemblages from Florida Bay sediment cores to indicate progres- sively increasing salinity during the later part of the 20th century and an increase in the amplitude of sa- linity variability about 1940. The coral record of Swart et al. (1996) is from Lig- numvitae Basin near the southwestern bay-ocean boundary where seasonal and inter-annual salinity var- lations are substantially lower than in central Florida Bay. Although they argue that salinity variations in Lignumvitae Basin are representative of salinity changes throughout most of Florida Bay, no compa- rable studies from interior-basins (where corals are rare) have confirmed this hypothesis. Further, Swart et al. (1996) noted the complexity of the coral 5'°O sig- nal, which is controlled by temperature, rainfall, rela- tive fluxes to the bay of freshwater and seawater, and evaporation, and, consequently, the difficulty in inter- preting this record without ambiguity. In contrast to the coral 6'8O-based salinity record, paleoecological studies of salinity-dependent fauna and flora from sediment cores suggest multi-decadal scale fluctuations of Florida Bay salinity superimposed on an overall increase in salinity during the last 200 years (Wingard er al., 1995). Like the 6!8O record, interpreting paleoecological signals may also be com- plicated by a number of factors, including changes over time in bottom sediment type, temperature, sub- aquatic vegetation, food availability, and predation, leading to uncertainty in paleoecological-based salinity reconstructions. Here we develop a new geochemical proxy of Flor- ida Bay salinity—the metal/Ca ratios preserved in fos- sil ostracode shells—and use it to reconstruct the sa- linity of Florida Bay for the last 180 years. We also compare the paleosalinity record to instrumental rain- fall records of South Florida to examine the effects of regional climate variability on Florida Bay salinity. ACKNOWLEDGEMENTS We are grateful to L. Brewster-Wingard, S. Ishman, R. Halley, C. Holmes, J. Stone, S. Schwede, and S. Kim for their help in the field and in dating and pro- cessing the core samples. Funded by USGS Place- Based Studies Program. REGIONAL SETTING Florida Bay (Text-fig. |) is a triangular-shaped, shal- low, restricted marine embayment bounded to the north by the coastal wetlands of the Everglades and to the south by the Florida Keys which separate the bay from open ocean waters of the Straits of Florida. The western boundary of the bay is less distinct, made up of a system of shallow sediment banks that restrict exchange between Florida Bay and the Gulf of Mex- ico. Water depths range from less than | m to about 3 m generally deepening to the south and west (Text-fig. 1). Tidal effects are minimal throughout much of the bay. Within the bay are a series of sub-basins separated by a network of small islands, called keys, and mud- banks. The mudbanks are submerged, accretionary features and are the primary sites in the bay for the accumulation of sediment, most of which is fine- grained calcium carbonate (mud) derived from calcar- eous organisms living within the bay (Stockman ef al., 1967; Enos and Perkins, 1979). Waters of Florida Bay are composed primarily of a mixture of two salinity end-members: fresh, terrestrial runoff/discharge from the Everglades with a salinity of less than | ppt, and saline, surface waters from the Gulf of Mexico and Straits of Florida with salinity around 36 ppt. Mixing of these two end members leads to a general northeast-to-southwest salinity gradient. The bay’s salinity can also greatly exceed 36 ppt as a result of evaporation. Evaporative concentration of Florida Bay waters generally occurs during the dry season (~November to May) and salinity values ex- OSTRACODE SHELI ~~ ¥ ; OE, ly % \ 270 BY E y \ —2 — Water Depth (m) h Mudbanks cs (< 1m deep) cs y / os' 81° 55' 50' 45' CHEMISTRY: DWYER AND CRONIN 251 § A) “ee Atlantic Ocean o Modern Samples * Cores 40' 35' 80°30' 25' 20' Text-figure |—Map showing Florida Bay region and location of sample sites for this study. Also shown is the location of the coral studied by Swart et al. (1996). ceeding 50 ppt have been reported in interior portions of the Bay (Ginsburg, 1972, and see reviews in Swart et al., 1996 and Mclvor et al., 1994). Wet season (~May to October) rains bring new runoff from the Everglades and reverse the dry season trend of increas- ing salinity. The strong influence of rainfall/runoff on the salin- ity of Florida Bay is evident from recent monitoring studies and varies in magnitude and timing with dis- tance from the mainland (Text-fig. 2, Text-fig. 3). Shal- low groundwater levels in the Everglades, which are largely controlled by rainfall, show a significant cor- relation with Florida Bay salinity providing further ev- idence of the impact rainfall/runoff on the salinity of Florida Bay (Tabb, 1967; White, 1983; as reviewed in Mclvor et al., 1994). Unfortunately, these studies were conducted after significant modifications were made to the natural run- off system in South Florida, which previously was characterized by sheet flow south from Lake Okeecho- bee through the Everglades to Florida Bay (Miller, 1997). During this century, a complex network of ca- nals and levees has been constructed in order to control flooding and to drain wetlands for agriculture, ulti- mately resulting in a lowering of the water table and an alteration of the near-surface hydrogeology over much of in southern Florida (RAIL, 1973: Miller, 1997). Just after the onset of canal construction around the turn of the century, the Miami to Key West railroad was completed, resulting in partial or complete closing of many of the ocean inlets between the Florida Keys. This has led to the hypothesis that the salinity of Flor- ida Bay may have been markedly different prior to large-scale human activities in south Florida, an idea which we evaluate here by reconstructing the salinity history of central Florida Bay using the chemistry of fossil ostracode shells. CONTROLS ON OSTRACODE SHELL CHEMISTRY PREVIOUS STUDIES Ostracodes are microcrustaceans that inhabit fresh- water, brackish, marine, and hypersaline environments. They secrete a bivalved carapace, or shell, that is com- monly preserved in sediments and whose chemistry is increasingly being used for paleoenvironmental recon- structions in various aquatic ecosystems (Chivas er al., 1983; Holmes, 1996). The shell is composed mostly of the mineral calcite (CaCO,), which co-precipitates minor amounts of foreign metals such as magnesium DOD BULLETIN 361 —2 — Water Depth (m) , Mudbanks “-* (< 1m deep) Salinity October 1995 (ppt) EVERGLADES —— ms St — 2 — Water Depth (m) >», Mudbanks G@— (<1mdeep) > Salinity June 1996 (ppt) 80°30" 25' 20' Text-figure 2.—Examples of salinity distribution in Florida Bay near the end of the wet (October) and dry (June) seasons. Contoured from Halley et al. data (1995). and strontium, that substitute into the crystal lattice in place of calcium. The uptake of Mg or Sr into the calcitic ostracode shell can be described by the follow- ing equation: = (K )(me/Ca ) D-me water (me/Ca), »stracode calcite where me/Ca represents the atomic ratio of Mg (or Sr) to Ca, and Kj, 1s the element-specific partition co- efficient. Thus, if K is constant or can be con- D-me strained, then the me/Ca ratio in ostracode calcite can be used to determine the me/Ca ratio of the water in which the shell was secreted (see Wansard, 1996). In the waters of Florida Bay, me/Ca ratios appear to vary with salinity as a result of mixing of freshwater runoff and discharge from the Everglades, and sea- water (Text-fig. 4). Thus, (me/Ca),,,,¢,. from (Me/Ca) ciracode calcines COUld be used to estimate Florida Bay salinity. as calculated OSTRACODE SHELL CHEMISTRY: DWYER AND CRONIN D253 5 e g > = < oO = x 5 012345 6 7 8 9 101112131415161718192021 22 Jan Jan 28 Month 9° Rainfall ----O---- Mouth Little Madeira Bay ----2---- Russell Bank ---f--- Lignumvitae Basin Text-figure 3.—Time series of monthly rainfall in South Florida (Florida Area 5, NOAA Data Archive) and bi-monthly salinity (Hal- ley et al., 1995) at four locations in Florida Bay for the period from November 1994 to June 1996. Note apparent amplitude decrease and delayed response of salinity change to rainfall with increased distance from mainland. In addition to (me/Ca),,,.,, other factors potentially control the uptake of foreign ions into calcite. From experimental and field studies with inorganic and bio- genic calcite, Kj. has been shown to have a strong thermodependence (Chave, 1954; Chivas ef al., 1983; Cadot and Kaesler, 1977; Burton and Walter, 1991; Dwyer et al., 1995). And K,,5, appears to be controlled primarily by calcite precipitation rate (reviewed in Morse and McKenzie, 1990). Aside from temperature and Mg/Ca,,,,.,, salinity may independently affect Kp .4.. While most workers have concluded that Kj yj. 1s constant or increases with in- creasing salinity, two survey studies of shells of ostra- code genus Cyprideis trom shallow coastal ponds of widely varying salinity (0 to >120 ppt) indicated a negative relationship between Kp yj. and salinity (Tee- ter and Quick, 1990; Bodergat, 1985). Similarly, Wan- sard (1996) noted the apparent nonlinearity in Ky, for Cyprideis when comparing Kp, calculated for freshwater specimens from Lake Banyoles, Spain (0.0169) to the Kj. calculated for marine specimens by Chivas et al. (1986) (0.0045). Unfortunately, results of empirical field studies from sites with significant inter-annual environmental variability often are incon- clusive because, even for live specimens, it is difficult to verify that the ostracode shells grew under the en- vironmental conditions measured at the time of collec- tion (e.g., Xia et al., 1997). To avoid the inherent un- Atomic Ratio OF 1020 S040 S50 60R 70 Salinity (ppt) Text-figure 4—Model data (connected filled symbols) showing the salinity dependence of Mg/Ca (mol/mol) and Sr/Ca (mmol/mol) in waters of Florida Bay. The model assumes conservative mixing of freshwater from the South Florida surficial aquifer system and seawater with the following elemental concentrations (ppm): Ca Mg Sr Na Freshwater (Sonntag, 1987) 90 5.6 0.8 26 Seawater (salinity = 35 ppt, 412 1290 ES) 10,770 Chester, 1990) Open symbols are ratios calculated from Florida Bay water anal- yses reported by Berner (1966) and Burns and Swart (1992), and they generally agree with the model data. At salinity above normal seawater, me/Ca ratios of Florida Bay waters may behave in a num- ber of ways. Under simple evaporative concentration, ratios will remain unchanged. However, if evaporation concentration is accom- panied by significant amounts of CaCO, precipitation (biogenic or inorganic), me/Ca ratios of bay waters will continue to increase along with salinity. Relative to Mg/Ca, this effect may be diminished for St/Ca because of the relatively high Sr/Ca ratio of aragonite, a mineral that makes up around 60% of the sediments deposited in Florida Bay (Burns and Swart, 1992). certainties associated with field studies, DeDeckker et al. (1999) analyzed the chemistry of Cyprideis shells raised in laboratory cultures under controlled temper- ature, salinity, and Mg/Ca,,,,., conditions. Their results confirm the strong effects of water temperature and Meg/Ca,..-. on the uptake of Mg and the lack of any salinity effect, positive or negative. In addition to magnesium and strontium, ostracode shell calcite coprecipitates minor amounts of sodium. However, unlike Mg and Sr, Na is not incorporated in the calcite crystal lattice, but instead resides in crystal defect sites (Busenberg and Plummer, 1985). Evidently sodium uptake is controlled by the sulfate (SO,*-) con- centration of the mother solution (Busenberg and 254 BULLETIN 361 Plummer, 1985). As a conservative ion in estuarine settings (Chester, 1990), SO,?- likely covaries with sa- linity in Florida Bay much like Ca, Mg, Sr, and Na. Therefore, the Na/Ca ratio of ostracode calcite may also be indirectly controlled by salinity and be useful for paleosalinity reconstructions in Florida Bay. Phylogenetic and ontogenetic factors also influence Ky me and Kj, of ostracode calcite (Chave, 1954; Ca- dot and Kaesler, 1977; Chivas er al., 1983), requiring the use of shells of same genus and of the same on- togenetic stage for meaningful paleoenvironmental re- constructions based on shell chemistry. Thus it is nec- essary to calibrate K,.,,. for shells of the species se- lected for paleoenvironmental reconsrtructions. STRATEGY TO DEVELOP PALEOSALINITY EQUATIONS Our strategy was to determine partition coefficients (Kp.me) for foreign metals for adult shells of the com- mon species Loxoconcha matagordensis on the basis of average me/Ca ratios for Florida Bay water and for average me/Ca ratios in modern specimens of Loxo- concha matagordensis. Ky, Would then be used in conjunction with fossil shell me/Ca ratios to calculate past values of me/Ca,,,,.. Which in turn would be used to estimate salinity based on the relationship displayed in Text-figure 4. This modern-average calibration method was pre- ferred over a site-by-site direct calibration of measured salinity to modern shell Mg/Ca at the site (7.e., Dwyer et al., 1995) for three reasons. First, it is difficult to separate the effects of water temperature, which an- nually varies from about 15—33°C in Florida Bay, from those of salinity. Previous studies, as well as our own data shown below, suggest strong thermodependence of ostracode Mg/Ca ratios. Separating salinity and temperature effects in coastal environments is difficult for most geochemical and faunal proxies of past en- vironmental conditions. However, because temperature and salinity are often positively correlated in Florida Bay waters (Swart ef al., 1996; results below), it is quite probable that downcore variability in ostracode shell Mg/Ca is due to changes in both factors (see discussion). Second, although salinity and temperature were measured at the time of collection of modern L. ma- tagordensis, the exact time that each individual ostra- code secreted its adult shells was not known. Because adults of L. matagordensis live for several months and this species secretes its adult shells year round (King and Kornicker, 1970; Kamiya, 1988), then many adults, in fact, did not secrete their shell at the time of collection. Because salinity and temperature vary tem- porally and spatially, it is possible only to obtain a D-me range of possible salinities and temperatures for the site for the previous few months. Third, during our period of sampling, the mean sa- linity in the study area varied from ~23.9 ppt (Feb- ruary 1998) to ~33.6 ppt (July 1998). With few ex- ceptions, our material does not include individuals that lived in extremely high (>40 ppt) or low (<18 ppt) salinity environments such as those experienced by Florida Bay historically (Robblee ef al., 1991). Con- sequently, a revised calibration should be developed in the future using individuals grown in cultures at known temperatures, over the widest salinity range possible, which for L. matagordensis is 10 to >50 ppt. METHODOLOGY ANALYSES OF WATER AND LIVING OSTRACODE SHELLS Water and ostracode samples for this study were col- lected from 25 U.S. Geological Survey sites across most of Florida Bay (Text-fig. 1). As part of a larger study to characterize the Florida Bay ecosystem, most of these sites have been sampled seasonally (February and July) since 1994 (Wingard ef al., this volume). Water samples, filtered in the field using disposable 0.45 wm syringe filters, were collected from each of the 25 sites in July 1998 and February 1999. In ad- dition, water samples (unfiltered) were collected in August 1997 from 51 sites in Biscayne Bay and the small bays that lie between Biscayne and Florida Bays. At each site, water temperature and salinity were mea- sured in the field using routinely-calibrated YSI or Hy- drolabs brand field instruments (Brewster-Wingard et al., this volume). Ca, Mg, Sr, and Na concentrations of the water sam- ples were measured by direct current plasma atomic emission spectrophotometry (DCP) in the Plasma Lab at Duke University Earth and Ocean Sciences to de- termine the relationship between water me/Ca ratios and salinity of south Florida’s coastal waters. Final data are reported as Mg/Ca, Sr/Ca, and Na/Ca atomic ratios with analytical precision, based on replicate analysis of [APSO standard seawater, of +1%, +2%, and +3%, respectively. Ninety-seven living (whole carapaces with visible soft parts), adult specimens of Loxoconcha matagor- densis, a cosmopolitan phytal ostracode in Florida Bay (Keyser, 1975; Cronin et al., this volume), were col- lected from sub-aquatic vegetation from 16 of the 25 USGS sites in Florida Bay in February 1998, July 1998, and February 1999. Shell Mg/Ca, Sr/Ca, and Na/ Ca ratios of these specimens were measured by DCP. Procedures follow those in Dwyer er al. (1995). An additional step included an overnight soaking of shells in full-strength commercial bleach to remove organic OSTRACODE SHELL CHEMISTRY: DWYER AND CRONIN matter prior to triple rinsing in deionized water. Re- sults are reported as atomic ratios of Mg/Ca, Sr/Ca, and Na/Ca in mmol/mol. Analytical precision, based on replicate analysis of internal-consistency standards is less than +2% for Mg/Ca and Sr/Ca ratios, and around +8% for Na/Ca. From six of the sites we also analyzed the Mg/Ca, Sr/Ca, and Na/Ca ratios of shells of dead adult speci- mens of L. matagordensis collected from the upper 10 cm of sediment push cores. These core-top specimens allowed a comparative evaluation of possible post- mortem alteration effects on shell chemistry. FossiL MATERIAL FROM SEDIMENT CORES Mg/Ca, Sr/Ca, and Na/Ca ratios were measured on fossil ostracode shells from five 1 to 2 m long sedi- ment cores. Four cores lie along a roughly north-south transect in central Florida Bay (Text-fig. 1). These in- clude mudbank cores BA-6A, RB-19B, and PKK-23 collected in 1994 near Bob Allen, Russell, and Park Keys, respectively, and core T-24 collected from with- in Little Madeira Bay along the coast of the Everglades near the freshwater outflow region of Taylor Slough. The fifth core, MB-1, is from Manatee Bay in Barnes Sound, an adjacent embayment northeast of Florida Bay. Chronstratigraphy for the cores was determined by uranium disequilibrium series methods (Wingard ef al., 1995: Brewster-Wingard et al., 1997; Robbins ef al., in press) and preliminarily corroborated with exotic pollen horizon studies (Wingard ef al., 1995). Calcu- lated linear sediment accumulation rates for BA-6A, RB-19B, and PKK-23A are 1.04, 1.22, and 0.78 cm/ year, respectively, and were applied to the entire length of the core. Chronstratigraphic information for core T- 24 and core MB-| are still under development. Samples for ostracode analysis were collected at ap- proximately 2-cm intervals. Most intervals in the 5 cores contained ostracodes and the majority of these yielded adult valves for geochemical analysis. Shells of Loxoconcha matagordensis were sufficiently abun- dant to produce continuous records in the Russell and Park Key cores and the upper half of MB-1. Kp inc values for L. matagordensis calculated from modern studies were then used to estimate salinity from fossil me/Ca ratios. In cores or intervals with insufficient numbers of L. matagordensis in (Bob Allen, T-24, and the lower half of MB-1; Cronin er al., this volume) we analyzed adult shells of second genus, Peratocytheri- dea. However, no K,,,,. values are available for Per- atocytheridea, so any down-core trends Peratocyther- idea me/Ca ratios can only be interpreted qualitatively. Shells were prepared and analyzed for Ca, Mg, Sr, and Na by DCP as for modern specimens discussed above. i) Nn Nn RESULTS AND DISCUSSION WATER CHEMISTRY The results of water chemistry analysis are listed in Table | and summarized in Text-figure 5. As shown in Text-figure 5, Mg/Ca and Sr/Ca ratios of Florida and Biscayne Bay decrease with decreasing salinity, shift- ing gradually from 35 ppt and 15 ppt and more steeply from 15 ppt to 0 ppt. Na/Ca ratios (not shown) behave similarly. The trends observed are similar to that predicted from the preliminary water chemistry data presented in Text-figure 4 and the assumption of conservative mixing of Ca, Mg, Sr, and Na between seawater and freshwater runoff from southern peninsular Florida. Mg/Ca values overlap directly with Mg/Ca ratios cal- culated from the data of Berner (1966) who measured Mg and Ca concentrations at salinity ~5, 17, and 43 ppt in the 1960’s. The steep decrease in me/Ca ratios with salinity is not typical of estuaries of the eastern United States. More typically, estuarine waters show little or no change in Mg/Ca, Sr/Ca, or Na/Ca ratios, retaining seawater-like values well below 15 ppt. This occurs because, relative to South Florida runoff, terrestrial runoff is generally far more depleted in Ca, Mg, Sr, and Na and me/Ca ratios are thus overwhelmed by seawater. The relatively high concentration of these el- ements, especially Ca, in south Florida runoff is likely the result of interaction between surface water and up- per Tertiary carbonate rocks of southern Florida. Most importantly for this study, the similarities in water chemistry between Florida and Biscayne Bay sampled from 1997 to 1999 and the comparable Mg/ Ca ratios obtained by Berner (1966) for Florida Bay suggest that the relationships between me/Ca,,,,.. and salinity are regionally and temporally persistent. MODERN SHELL CHEMISTRY Results of shell chemistry analyses of modern spec- imens of adult Loxoconcha matagordensis from veg- etation samples and sediment core tops are listed in Table 2 and the results of vegetation specimens are summarized in Text-figure 6. Text-figure 6 shows shell Meg/Ca and Sr/Ca ratios versus measured ambient wa- ter salinity and temperature from sampling trips in February 1998, July 1998 and February 1999. It is clear from Text-figure 6 that there are no ob- vious trends between modern shell me/Ca ratios across the entire range of measured water temperature and salinity. Mg/Ca ratios range from 23 to 54 mmol/mol. Shells from February 1999, covering the fewest num- ber of sites in the three seasonal data sets, appear to show a positive correlation with both salinity and tem- 256 BULLETIN 361 Table 1.—Chemistry of waters from Florida and Biscayne Bays. Calcium, magnesium, strontium, and sodium concentrations reported in ppm; Mg/Ca and Na/Ca as mol/mol, and Sr/Ca as mmol/mol. * Salinity determined using sodium concentration. Florida Bay sites correspond to map (Text-fig. 1). Biscayne Bay sample locations available from the authors. Salinity Sample site (ppt) Ca Mg Sr Na Mg/Ca Str/Ca Na/Ca Florida Bay (July 1998) 1 26.9 332 1005 6 7792 4.99 8.39 40.86 2-Top 23.96 333 972 6 6098 4.81 8.59 31.89 3-Top 29.1 362 1105 7 8303 5.04 8.44 40.02 4 32.45 401 1272 8 9561 5.23 8.61 41.54 5 32.45 400 1249 7 9343 SAS 8.49 40.72 6 35.94 436 1379 8 10657 S22 8.58 42.63 6-Top 35.31 436 1370 8 10545 5.18 8.53 42.20 7 SMlaits) 457 1431 8 10745 5.17 8.50 41.01 8 23.51 319 914 6 5824 4.72 8.37 31.78 :) 28.24 412 1196 8 5831 4.79 8.52 24.67 10 34.63 435 1342 8 9860 5.08 8.48 39.47 11 30.78 380 1192 i 9161 Sel 8.56 41.98 12 36.85 432 1363 8 10523 5.20 8.60 42.42 13 40.12 503 1573 10 11372 5.16 8.67 39.45 14 40.1 498 1538 ) 11400 5.09 8.66 39.91 15 36.75 453 1386 8 10512 5.04 8.48 40.42 15-Top 36.18 450 1379 8 10684 5.05 8.61 41.41 16-Top 38.77 432 1327 8 10424 5.07 8.58 42.10 17-Top 34.61 422 1290 8 9573 5.04 8.46 39:52 18 36.74 438 1352 8 10454 5.09 8.56 41.63 20 27.82 349 1054 6 8023 4.97 8.29 40.03 21 39.34 469 1441 9 10946 5.06 8.67 40.66 21-Top 38.72 459 1405 9 10764 5.05 8.54 40.86 22-Top 38.56 469 1455 9 11104 5.11 8.69 41.24 23-Top 36.25 433 1368 8 10639 5.21 8.65 42.84 24 35.93 423 1307 8 10191 5.10 8.51 42.03 24-Top 35.65 431 1337 8 10326 Sez 8.50 41.80 25 35.57 427 1301 8 10126 5.02 8.46 41.31 26-Top 35.18 420 1304 8 10320 Spl 8.63 42.82 Florida Bay (February 1999) 1 28.16 298 824 6 5704 4.55 8.45 83332 1 28.16 299 814 5) 5384 4.48 8.24 31.34 2 25.24 359 1026 7 6205 4.71 8.35 30.14 3 29.27 385 1145 7 8520 4.90 8.30 38.54 4 27.81 366 1090 7 8281 4.91 8.33 39.43 5 2935 389 1145 7 8470 4.85 8.22 37.93 6 28.87 374 1111 7 8317 4.90 8.25 38.75 7 30.47 383 1160 7 9021 4.99 8.30 41.02 8 19.38 286 795 5) 5003 4.59 8.19 30.51 9 24.06 343 996 6 6141 4.79 8.35 31.23 10 26.86 367 1078 7 6357 4.84 8.38 30.19 11 27.04 358 1058 6 8047 4.88 8.24 89122 12 28.61 370 1106 7 8362 4.94 8.38 39.45 13 33a 418 1262 8 9454 4.97 8.21 39.41 14 32.94 422 1287 8 9735 5.03 8.37 40.24 15 34.62 443 1340 8 9880 4.99 8.34 38.87 16 35.34 447 1363 8 10012 5.03 8.50 39.06 17 32.54 427 1308 8 9953 5.05 8.65 40.63 17-banktop* 31.3 417 1262 8 9583 4.99 8.40 40.03 18 35.76 455 1401 9 10250 5.08 8.57 39.31 20 24.97 347 1023 6 6154 4.85 8.53 30.89 21 34.72 440 1313 8 9618 4.92 8.18 38.09 21 34.72 443 1333 8 9633 4.96 8.25 37.91 21-lake* 36.9 543 1646 11 11288 5.00 8.86 36.27 21-lake* 35.4 544 1638 10 10841 4.97 8.70 34.75 22 eppilil 427 1302 8 9753 5.03 8.56 39.81 23 34.04 428 1298 8 9707 5.00 8.49 39.54 24 35.13 416 1257 8 9426 4.98 8.37 39.48 26 33.51 409 1223 8 94.14 4.93 8.40 40.15 26 33.51 408 1215 V 9201 4.91 8.29 39.34 Table 1.—Continued. OSTRACODE SHELL CHEMISTRY: DWYER AND CRONIN Sample site Biscayne Bay (August 1997) MRO6 TMO2 MRO7 MROS5 MRO4 MRO3 WCO02 SPO1 SKOL MRO2 LRO3 PROI BLO2 AROI BLO1 MWOl1 GLO02 MRO1 BBS5S1 BBO1 LROI MIO1 CGO1 BBO3 CDOo1 BBS5O0 BB48 BB48 BBO9 BB39A BB34 BB47 BB10 BB27 BBSA BB23 BB29 BB31 BB28 BB44 BB41 BB45 BB45 BB32 NNH BB25 BB46 BBO7 BB35 BB42 BB36 BB43 BB37 BB39* Standards* IAPSO IAPSO IAPSO IAPSO IAPSO IAPSO Salinity (ppt) Ca Mg Sr Na 0.3 64 9 1 3 0.3 66 8 1 = 0.4 60 11 1 11 0.5 66 14 1 43 0.7 71 26 1 172 it 76 39 1 306 1.4 80 42 1 367 2.3 88 65 1 562 2.7 92 94 1 771 2.8 93 94 1 787 3.8 96 87 1 723 Spill 141 172 2 1380 9.4 174 334 3 2099 10.9 190 387 3 3020 12.4 203 469 3 3478 12.6 198 449 3} 3370 13.4 205 459 3 3408 16.4 142 279 2 2411 17.4 233 632 4 4418 18.2 267 697 5 4658 19.] 126 209 2 1835 20.8 269 708 5 5047 23.3 290, 755 5) 5253 23.6 328 918 6 5775 231) 319 874 6 5680 24.1 317 891 6 5798 26 320 945 6 7464 26 317 938 6 7537 26.4 314 919 6 7353 26.9 346 1029 6 7903 29 327 964 6 7562 30.2 366 1110 7 8686 Si 384 1166 7 8912 Shila7/ 386 1174 7 9009 Sl) 398 1220 7 9292 32 383 1165 7 9009 32.1 392 1191 7 9114 32.4 393 1206 1 9233 32.6 394 1200 7 9122 32.9 397 1219 7 9338 33 390, 1210 7 9274 $36). 400 1220 7 9240 B3el 393 1218 7 9362 33.8 372 1151 7 8917 33.9 412 1273 8 9538 8522 413 1283 8 10087 35.2 416 1305 8 10320 35.6 427 1330 8 10513 35.8 420 1322 8 10265 36.1 428 1353 8 10615 36.4 430 1335 8 10174 36.7 433 1354 8 10474 37.3 436 1374 8 10707 33.9 425 1329 8 10377 33.4 422 1314 8 10235 33.0 424 1310 8 10093 3257. 432 1328 8 10015 35.1 430 1334 8 10740 3355 440 1345 8 10247 32.9 436 1349 8 10077 251, 8.59 8.53 8.53 8.47 8.14 8.33 8.57 8.38 258 BULLETIN 361 Table 2—Chemistry of living and sediment coretop shells of Table 2.—Continued. adult specimens of Loxoconcha matagordensis. Mg/Ca, St/Ca, and Na/Ca ratios reported as mmol/mol. * Salinity determined using so- Sample Temp. Salinity dium concentration. Florida Bay sites correspond to map (Text-fig. Site CC) (pp) VPI Mg/Ca_ Sr/Ca_Na/Ca 1). Sample descriptors (e.g. #1, A) refer to separate subsamples from July 1998 the sites. Biscayne Bay sample BBS51 is located near the MB1 core site (Text-fig. 1). VPI (visual preservation index) is a measure of Lage BOSE 30.25 20s sO70 105 14.71 shell clarity ranging from | (clear, unaltered) to 7 (opaque, highly LA#3 31.3 26.9 2.5 39.71 4.31 17.09 Brereant 1A#3 31.3 26.9 25 35.88 3.96 13.99 23#1 31.94 36.76 2.5 4449 3.68 17.00 Sample Temp. Salinity 2241 30.42 39.93 2.5 36.11 420 14.34 Site (C) (ppt) VPI Mg/Ca Sr/Ca Na/Ca 2241 30142) 39193| 255) | 42.48) Ao 7 Sa Florida Bay Living Specimens 8A#2 30.86 23.88 2.5 38°22 35977 16.45 Febiny 1908 8A#2 30.86 23.88 2.5 43.36 4.16 14.66 os 526 Aas a Pye eRe eee 16#2 29338) 3878) 255) S7:85i 4 Olea 7 AAO a7 A Nats 850 “GOaN 16#2 29138) 38078) 225) S271 Se ie EO AI 4 a5 64 SMG. 1541 LLA#2 32:99 33:13 25 39195 3:83. mI400 7 75.9 317 4 3778 365 15.04 LLA#2 ewes) “eeulel Oey seis BOP 1238 17 25.9 317 4 5920 334 «13.77 1LA#2 Ewch) eis Os Ge B75 1G57 7 35.9 31.7 4 43.08 3.70 17.56 SA#2 33.42 31.94 2.5 39.79 3.55 15.46 l 21 15.8 4 3770). 3u19 15.70 12A#2 3458) 936197) 255 38.14 3.83 16.53 1 21 15.8 4 36.59 3.57 16.03 12A#2 34.58 36.97 DES) 35.41 4.02 14.87 | 21 15.8 3 38.64 3.86 15.85 18#1 ys 205 DS SER S89 14.65 1 21 15.8 D 46.84 3.29 17.03 18#1 29195, 3705-255) 44197 1 S4 misao 1#1 21 15.8 DSS HA StOS OWS 18#1 ps ey DS 309 BG less 1#1 21 15.8 25 27.01 418 14.53 20A#3 iy AIG AS Zyl 293} GO #1 21 15.8 2) 28-118) 73:60 18.45 20A#3 B10 AIS SS ESO) LSS 18.97 44 21.6 16.7 2:5 29.85 3:81! 26:86 26#2 3326) 35:48) 255) 32189) 32a 444 216 167 25 35.58 4.10 16.43 26#2 83126) 35:43) 255) 34°51 SsSiemlarsy SH 21.9 AG 2.5) 40:34 3:68" 14.57 26#2 33.26 35.43 25 35:40 341) ies? Se) ge ioe Oa palm gl ae 6A 33.29 35.94 2.5 39.06 3.97 16.24 ie as ie ae ee ee oe 6A 33.29 35.94 25) |4154) 3193) Netstas S#1 20 15.2 25 25.59 4.01 11.88 a 33:29 © 824s 28 NE ae ae 56 ae eee Sas At a Cavan 4A#1 B03 Spy PS SBR SOO iias 11#5 19.4 19.3 2.5 37.53 3.69 15.44 see Sma OE Ra eee HOS eS on foe 3 AAGR 580 AOE 4A#1 BD 88) 32051) 0 2654249) Omens antes 194 163 DS Aaah 2a eee 14#1 33.01 41.03 2.5 30.04 3.69 17.62 “uD ME AO AS) AAG AGE) TAGE 14#1 33.01 41.03 2.5 29.70 3.90 18.85 12#2 16 0.7 25 2594 3.78 14.04 14#1 33101 41003) 2558 3429) 423 enIaSD 14#1 IBS 269) 25) 20:85 876, SIS6 22 SUS Bee gy eee ead) sos 14#1 BS SOD AS TT BSB GT 22 30.4 39.9 3 35.30 4.18 16.90 16#1 26.3 30.1 AS OT BOL eA 22 30.4 39.9 > 37.46 4.32 27.50 16#1 26.3 30.1 DES 2 Sel S OS mls e28: 8 30.9 23.9 4 44.42 3.86 13.72 16#1 26.3 30.1 MS DEeO” BV AA 8 30.9 Me) al 3705) 4:47 eelGes 17#3 25.9 Bile OS AGS GME 87 8 30.9 23.9 1 50.39 4.02 16.04 17#3 25.9 31.7 AS SOO B59 Gey 8 30.9 2319) 4 Mle Mi TAG 18#2 24.9 29.7 AS OOM Ae NGA 8 30.9 23.9 4 44.62 3.75 12.76 18#2 24.9 29.7 25 29.74 3.76 16.13 20#1 OO ig DS MSG AOL iAGI Hep umes 20#1 19.9 17.1 VS Bln Al Sil 18 22.6 35.8 3 44.99 3.32 15.30 20#1 19.9 17.1 D5 WOl ANG Wie 18 22.6 35.8 3 3353 3.45 15.60 21 Shell 24 28.9 2.55 29.53 4.02 15.79 18 22.6 35.8 3 46.06 3.75 17.42 21 Shell 24 28.9 DS WO Aq) 1S 18 22.6 35.8 3 38.74 3.74 16.33 21 Shell 24 28.9 2551929193) Sh7 0406 18 22.6 35.8 3 53.83 3.36 14.16 22#1 24.9 30.2 D5 Weil BIO las 8 20 19.4 3 SETS S Sines 22#1 24.9 30.2 AS Me AO WCB 20 19.4 3 37.92 4.03 18.78 22#1 24.9 30.2 25 3089 3.54 14.83 8 20 19.4 3 A277 AOS 15.60 23#1 DBS 313) OFS) 26.94 B35) 15.56 8 20 19.4 2 37.34 4.42 15.65 26# | 27.6 31.6 2D 36:37 3270 14.94 8 20 19.4 3 BB 00m AS 15.35 26#1 27.6 31.6 25 3411 3.45 14.50 Table 2.—Continued. OSTRACODE SHELL CHEMISTRY: DWYER AND CRONIN 259 Table 2.—Continued. Sample Site Temp. (°C) Coretop Specimens Florida Bay (July 1998) ws) NNN NY DODO Deo ed oS >> 20A 30.42 30.42 33.26 33.26 33.26 33.26 30.34 30.34 30.34 30.34 31.94 31.94 sil 31 31 31 31 31 31 31 31 31 31 31 32. Sle Sik ln bo ww Ww WW WwW WHoWWwWWowWwWWwWwwwbw NNNNNN WY OO 0 O BE Salinity (ppv) Sample Temp. Salinity VPI Mg/Ca Sr/Ca_ Na/Ca Site CC) (ppt) VPI Mg/Ca Sr/Ca Na/Ca 9 3122 BBR Ae AROS) SH) BSE 9 Sl sy 28.8 DES 38.72 3.89 16.57 25 35.87 3.85 16.27 9 S132 28.8 DES 38.89 4.01 13.27 25 36.09 3.58 18.30 9 31.32 28.8 2.5 28.74 3.90 15.20 25 33.85 3.90 15.77 9 Silas 28.8 25) Siva 3153) 14.71 5 OW al) ivigg 15 28:54) 2675) 2 400083710 654 Pry esis) S/K2) 16.99 Biscayne Bay (August 1997) = see ie 15.50 BBSI Slee ww 33.14 3.64 16.39 a ae ae bass BBS1 3035) 14 3 EN "SUE ily Ze) ae Ae BGG eG BBS1 Bk35 17.4 3 37.59 4.11 SHG. ae Fase 413 16.69 BBS1 Siil33)5) 17.4 4 42.50 3.91 14.98 A) & 34.42 3.05 15.97 BBS1 31.35 17.4 3 32.50 3.46 Sys D5 37.62 3.84 16.73 BBS1 31.35 17.4 2 31.02 $}55) 16.47 25 40.72 3.85 16.13 BBS1 31.35 17.4 3 40.05 3.64 16.55 25 42.00 3.77 17.44 BBS1 S1k35 17.4 2 41.04 3.83 17.35 2.5 36.14 3.69 15.89 25 37.58 3.69 14.73 25 42.42 3.80 17.89 perature. There also seems to be broad positive cor- oe aes aul sae relation between Mg/Ca and temperature. Further- 25 3818 367 15.50 more, shells collected from July 1998, when both sa- 5) 30127) 30211 15.15 linity and temperature were relatively high, all have 2:5) 49:81 4214! 13:99 Mg/Ca ratios > ~30 mmol/mol. 2 SOUS! oUt ISS Sr/Ca ratios range from 3.3 to 4.6 mmol/mol and 25 4146 3.71 14.84 : : i : : 25 3625 3.75 15.06 appear to display a broad negative correlation with 25 3735 346 16.03 both salinity and temperature, especially within the D5 Sails Bs 1 11,0)5) February data. Na/Ca ratios (not shown) range from 2.5 48.07 4.02 15.59 12 to 19 mmol/mol and show no variation with salinity 25 39.17 3.52 IS}ES)7/ or temperature. IF) 42.45 4.28 14.08 : Le <. 25 40.73 3.68 1437 Core-top specimens (Table 2), consisting of both ar- 25 4859 3.38 £14.35 ticulated and disarticulated valves, yield Mg/Ca, Sr/Ca, 2S 019 37/6) 14°20 and Na/Ca ratios that are indistinguishable from those 25 46.59 3.80 17.16 of vegetation samples. This implies that post-mortem DiS5eees4'570 3:83) lial os Barres : i Wee. 4645 AT 17.40 effects on shell me/Ca ratios in Florida Bay are neg- Diy 36.07 B77) 16.75 DS 36.67 3.86 14.84 ; 25 51.86 2.90 12.46 Modern Water Chemistry IY) 44.47 3.24 15.40 DS 34.52 3.39 15.53 2.5 32.05 3.74 14.71 2.5 43.11 3.59 15.46 2.5 43.41 3.71 16.24 2.5 36.39 3.26 16.21 ° MS “S95 S75 i138 g DES 43.07 4.04 17.16 re) 25 39.89 3.75 15.58 E 2 39.55 3.98 17.76 x Pies) 36.94 Bear 15.11 2S 44.04 4.06 17.16 ae ae Aor ea oO Sr/Ca (mmol/mol) ae i e ates Fh J ° Mg/Ca (mol/mol) DS 34.23 3.51 13.89 2 Ee a S18 0 5 10 15 20 25 30 35 40 45 PMS) 42.95 3.96 14.50 SN 36.02 9337 15.86 Salinity (ppt) EES EN GAN: Joust) Text-figure 5—Mg/Ca and Sr/Ca ratios of waters from Florida PN) 46.61 3.69 15.99 and Biscayne Bays collected in 1997-99. 260 BULLETIN 361 Table 3—Chemistry of fossil shells of Loxochoncha matagordensis and Peratocytheridea setipunctata trom downcore portions of sediment cores from Florida Bay. Core numbers correspond to map (Text-fig. 1). Mg/Ca, Sr/Ca, and Na/Ca ratios reported as mmol/mol. Intra-sample average ratios reported in right three columns. Most shells analyzed were adult stage, though some juvenile molts were also analyzed. VPI (visual preservation index) is a measure of shell clarity ranging from | (clear, unaltered) to 7 (opaque, highly altered). Depth Mg/Ca Sr/Ca Na/Ca (cm) Year Genus Species Molt VPI Mg/Ca Sr/Ca Na/Ca (avg.) (avg.) (avg.) Russell Bank Core 19B Site 12* 1998.0 bs matagord. A D5, 29.20 3.93 16.55 SPRIIT/ 3.89 15.50 Sitemi24 1998.0 fs. matagord. A De) 25.94 3.78 14.04 Site 12* 1998.0 iby matagord. A DES 38.14 3.83 16.53 Site 12* 1998.0 he matagord. A py) 35.41 4.02 14.87 1 1994.2 ib matagord. A 1 40.57 4.07 16.60 37.84 4.03 16.25 | 1994.2 EE matagord. A 2 37.07 4.17 16.81 | 1994.2 Ibs matagord. A 1 35.89 3.85 15.34 3 1992.5 1b, matagord. A 3} 39.82 4.08 15.67 38.39 3.95 16.88 3 1992.5 16, matagord. A 3 36.97 3.81 18.10 5 1990.9 EE: matagord. A 3 40.19 3.44 16.04 39.46 3.78 15.64 5) 1990.9 Ih, matagord. A 2 36.97 3.98 16.23 5 1990.9 Ios matagord. A 1 41.22 3.93 14.66 7 1989.3 il, matagord. A 3 36.87 3.90 Sy 727/ 39.61 3.94 15.67 a 1989.3 1B matagord. A 3 42.35 3.98 16.07 9 1987.6 Ie, matagord. A 2 32.10 3.60 16.63 36.08 3.74 15.95 9 1987.6 ik matagord. A 4 36.94 3.56 15.48 9 1987.6 ie matagord. A 4 39.19 4.06 15.74 11 1986.0 IL; matagord. A 2D) 31.43 4.18 17.40 32.48 4.09 16.50 11 1986.0 Ji matagord. A 3 31.39 Sn? 16.68 11 1986.0 ibs matagord. A 4 34.61 4.37 15.42 13 1984.3 Ibs matagord. A 2 29.87 3.83 18.11 34.92 3.78 16.09 13 1984.3 iE matagord. A 4 36.75 3.68 15.44 13 1984.3 Ib matagord. A 4 38.14 3.84 14.71 NS) 1982.7 is matagord. A 4 41.81 3.97 i13}.113} 35.10 3.91 14.79 1S 1982.7 iL. matagord. A Dy 33.30 3)57/5) 15.58 15 1982.7 IL. matagord. A 3 30.17 4.01 15.65 17 1981.1 ee matagord. A 4 31.30 3t73 13.99 34.99 3.56 14.97 wi 1981.1 IL: matagord. A 4 39.24 3.18 15.58 17 1981.1 Ib matagord. A 3 34.42 3.76 15%33 19 1979.4 iL. matagord. A 2 35.40 3:79) 15373) 40.09 3.64 15.12 19 1979.4 ik matagord. A 4 44.78 3.50 14.50 21 1977.8 IE: matagord. A 3 36.75 4.27 18.29 36.75 4.27 18.29 23 1976.1 EE matagord. A 3 32.97 3.68 16.25 38.00 35)! 15.14 23 1976.1 BS matagord. A 3 43.43 3.36 15.78 23 1976.1 iE. matagord. A 3 37.60 Boi 13.40 25 1974.5 E, matagord. A 3 37.30 3.85 13.09 36.02 3.74 14.76 25 1974.5 Ib matagord. A 3 35.18 3.60 15.08 PPS) 1974.5 ib matagord. A 3 35.59 S75) 16.12 27 1972.9 ik, matagord. A 3 36.44 3.95 16.60 36.67 3.68 SSS) 27 1972.9 Jk. matagord. A 3 Sik25 3.60 16.36 27 1972.9 LE. matagord. A 3 42.33 3.50 12.42 29 1971.2 il, matagord. A 3 30.07 3555 16.42 SE95 3.78 16.92 29 1971.2 Ex matagord. A 3) 33.82 4.02 17.42 31 1969.6 1. matagord. A 3 28.06 3152 72) 37.85 3.78 15.53 31 1969.6 iL. matagord. A 4 42.47 4.13 14.05 31 1969.6 I: matagord. A 3} 43.01 3.68 15.36 33 1968.0 ibs matagord. A 4 33.07 3.88 15.93 36.21 4.09 15.39 33 1968.0 i matagord. A 3 39.89 4.24 15.71 39.59 3.78 15.11 33 1968.0 Ue: matagord. A D 35.68 4.13 14.53 35 1966.3 ib. matagord. A 3 41.36 4.06 15.71 35) 1966.3 ik: matagord. A 3 41.07 Si52 Sy 7/tl 41.37 4.03 15.63 35 1966.3 Ib, matagord. A 3} 36.34 ST 13.92 37 1964.7 ik. matagord. A 3 39.80 4.01 15.87 46.37 3.92 15.11 37/ 1964.7 JE; matagord. A 3 42.94 4.05 15.38 39 1963.0 ib. matagord. A 3 48.80 4.05 12.16 39 1963.0 ib. matagord. A 3 46.63 3.74 S\S7/7/ 41.16 4.09 15:29) OSTRACODE SHELL CHEMISTRY: DWYER AND CRONIN 261 Table 3.—Continued. Depth Mg/Ca Sr/Ca Na/Ca (cm) Year Genus Species Molt VPI Mg/Ca Sr/Ca Na/Ca (avg.) (avg.) (avg.) 39 1963.0 IL matagord. A 4 43.68 3.97 17.39 41 1961.4 i. matagord. A 2 41.97 3.94 17.50 41 1961.4 Ibe matagord. A 3 40.36 4.25 13.08 43 1959.8 I, matagord. A 3 33.40 4.17 IIS)7/5)} 41.29 3.92 16.19 43 1959.8 I, matagord. A —- 49.18 3.66 16.63 45 1958.1 IY, matagord. A 3 35.52 3.82 14.83 35.52 3.82 14.83 47 1956.5 Ibe matagord. A 3 39.51 3.27 712 42.27 3.77 15.51 47 1956.5 IU, matagord. A 3 48.59 4.00 13.49 47 1956.5 IL. matagord. A 3 38.70 4.02 15.93 49 1954.8 Ie matagord. A 3 36.08 3.93 15.54 42.15 3.81 14.81 49 1954.8 I. matagord. A 3 46.31 3.44 14.75 49 1954.8 1b. matagord. A 3 44.06 4.04 14.15 51 1953.2 IE. matagord. A 3 28.07 3.65 17.61 33.74 3.90 15!53) 51 1953.2 iL matagord. A 4 28.57 3.98 13.90 51 1953.2 Ik matagord. A 3 44.57 4.05 15.09 53 1951.6 ike matagord. A 3 31.80 3.48 15.48 37.71 3.80 14.54 38 1951.6 IE: matagord. A 3 40.79 4.20 14.00 53 1951.6 Ie: matagord. A 3 40.54 Sh9/5} 14.15 Si) 1949.9 jt matagord. A 355 36.35 3.88 13.88 35.38 3.86 14.96 55 1949.9 IE matagord. A 35) 35.20 3.92 16.28 55 1949.9 Ee matagord. A 3h5) 34.60 S/7/ 14.73 Si 1948.3 L. matagord. A 3.5 42.42 4.05 13.05 37.10 3.98 15225 57 1948.3 iE matagord. A She) 31.49 3.80 14.80 57 1948.3 6% matagord. A 355 37/39 4.09 17.92 59 1946.6 L. matagord. A 3.5 44.98 3133 14.41 41.53 3.65 1Sal2 59 1946.6 ik. matagord. A 355 36.70 3.88 16.87 59 1946.6 ik. matagord. A 35) 42.90 3.76 14.08 6l 1945.0 16 matagord. A 355 34.42 3.89 13372 41.67 3.57 14.99 61 1945.0 ibs matagord. A 3:5 48.91 325 16.26 63 1943.4 1B matagord. A 3 33.84 BP? 18.16 32.01 3.86 16.41 63 1943.4 Ik, matagord. A 385 26.60 3.93 15.67 63 1943.4 ie matagord. A 315) 35.59 3:93 15.39 65 1941.7 JE. matagord. A 35 42.19 4.19 15.56 35.44 3.70 15.63 65 1941.7 jks matagord. A 355 PIAA 3.22 15.40 65 1941.7 Ie matagord. A 3.5 38.35 3.68 15.92 67 1940.1 L. matagord. A ys) 26.85 375 14.89 33.16 3.91 15.45 67 1940.1 ik. matagord. A B35 39.48 4.08 16.00 69 1938.4 ik. matagord. A 3.5 31.24 3.94 16.06 38.52 3.62 15.15 69 1938.4 If, matagord. A 3.5 36.77 3.60 17.20 69 1938.4 1b. matagord. A Shp) 47.54 3.31 12.18 71 1936.8 b- matagord. A 35 35.45 3.94 20.43 32.76 4.06 E27, 71 1936.8 bs matagord. A Sha) 32.04 4.15 14.21 71 1936.8 Ee matagord. A BD 33.75 4.25 17.10 71 1936.8 Ih. matagord. A Sh5) 29.80 3.89 17535 73 1935.2 ib. matagord. A 3:5 43.92 S/T) 15.55 39.82 3.74 15.44 73 1935.2 Jb, matagord. A 3:5 29.10 3.94 18.92 73 1935.2 Ik matagord. A Si) 46.43 3.50 11.85 75 1933.5 ies matagord. A 3}5) 33.46 3.66 13.69 34.40 3}5y/ 14.66 75 1933.5 Ik. matagord. A 3}.5) 83555) 3.39 15.08 75 1933.5 Ib. matagord. A 3) 36.18 3.67 15222 77 1931.9 Ib matagord. A 35) 34.49 4.19 16.18 39.61 3.97 14.41 77 1931.9 Ibe matagord. A 3.5 44.74 ae) 12.64 79 1930.2 Ib matagord. A BS 36.38 3.85 14.29 38.18 3.85 15.18 79 1930.2 iE. matagord. A 3h5) 29.62 3.81 15.96 79 1930.2 Ib. matagord. A 3) 48.54 3.89 15.30 81 1928.6 Ee matagord. A 3.5 32.32 4.21 15.21 39.08 3.85 14.61 81 1928.6 ile matagord. A 3.5 42.56 Sh Si1/ 14.32 81 1928.6 E. matagord. A 315) 42.35 3.77 14.30 83 1927.0 ik. matagord. A 3.5 32.54 3.91 14.71 35.98 3.96 15.62 83 1927.0 ibs matagord. A 3.5 42.88 3.98 16.96 262 BULLETIN 361 Table 3.—Continued. Depth Mg/Ca St/Ca Na/Ca (cm) Year Genus Species Molt VPI Mg/Ca Sr/Ca Na/Ca (avg.) (avg.) (avg.) 83 1927.0 Is matagord. A 355 32.53 4.00 15.20 85 1925.3 L. matagord. A 355) 34.11 3.47 17.69 32.88 3.73 15.55 85 1925.3 IL matagord. A 355) 31.65 3.99 13.42 87 1923.7 IW matagord. A 3'5 33559) 3.83 16.18 39.36 3.70 16.40 87 1923.7 L: matagord. A 3S) 41.05 3.80 17.83 87 1923.7 IE: matagord. A 3.5 43.44 3.47 Heyl) 89 1922.0 Ie matagord. A 35) 37.86 4.20 14.07 35.43 4.12 14.22 89 1922.0 IL matagord. A 35) 34.23 4.05 14.43 89 1922.0 Ib matagord. A 3h) 34.21 4.12 14.16 93 1918.8 IL matagord. A 35 34.39 3.84 15.34 38.23 3.67 15.30 93 1918.8 1: matagord. A 3.5 32:25) 3.40 15.10 93 1918.8 IE matagord. A 355 28.03 S77 15.48 95 1917.1 ES matagord. A 3}5) 32.87 4.12 14.68 32.87 4.12 14.68 97 1915.5 Ih, matagord. A 3°) 28.97 3.60 14.84 28.97 3.60 14.84 99 1913.9 JE. matagord. A 3 32.60 3.98 16.64 32.60 3.98 16.64 101 1912.2 TE matagord. A 35 36.37 3.59 15.51 36.37 3559 15.51 103 1910.6 Ib: matagord. A 3:5 36.49 3.65 14.09 83222: 3.68 13.85 103 1910.6 Ib; matagord. A BS 32.29 3.79 13.60 103 1910.6 IL, matagord. A 3°5 30.87 3.60 13.84 105 1908.9 je. matagord. A Br 32.82 3.98 13.66 37.66 3.84 15.23 105 1908.9 IE matagord. A Shp) 45.68 3.70 16.77 105 1908.9 iL; matagord. A 355 34.47 3.84 15.25 107 1907.3 Es matagord. A 35 31.31 4.03 16.13 36.32 4.11 15.14 107 1907.3 Es matagord. A BES 41.34 4.20 14.15 109 1905.7 Ib. matagord. A 355 36.09 3.76 16.67 33.07 3.73 16.11 109 1905.7 is matagord. A Bh) 35.36 3.80 IAEQil 109 1905.7 I 6 matagord. A 3}5) 27.76 3.64 13.76 113 1902.4 IL. matagord. A 35) S255 3.66 13.96 32°38) 3.67 14.69 113 1902.4 ES matagord. A 35) 32°92. 3.68 15.43 115 1900.7 ib. matagord. A 35 32.88 3.88 MAST, 32.88 3.88 NZ/E3i7/ 119 1897.5 es matagord. A Bi) 48.35 3.43 15.21 48.35 3.43 15.21 121 1895.8 js matagord. A 35) 33.64 3.64 15.28 33.64 3.64 15.28 123 1894.2 iE matagord. A 3.5 37.04 3.84 15.89 123 1894.2 ih matagord. A 3.5 35.54 3.60 15.10 125 1892.5 Ib matagord. A Sh) 36.19 4.05 13:33) 85:35) 3.80 16.59 125 1892.5 iL. matagord. A SiS) 32.70 4.08 22.80 125 1892.5 Ii matagord. A 355 37.16 3.26 13.63 129 1889.3 es matagord. A BES) 38.87 3152 15.02 33.40 3.70 15.61 129 1889.3 Ike matagord. A B3e5 29.21 3.84 i>yils) 129 1889.3 L. matagord. A 335) 32.13 3.74 16.69 131 1887.6 ik matagord. A 355) 34.92 3.82 18.10 37.87 3.86 18.63 131 1887.6 Ik, matagord. A 315) 40.82 3.90 19.15 137 1882.7 Ik matagord. A 39) 47.33 3.78 15.79 STPSi, 3.74 14.52 137 1882.7 Ik; matagord. A 3h5) 28.12 3:99) 14.54 137 1882.7 ik. matagord. A 3'5 37.26 3.45 13.22 137 1882.7 Ee matagord. A 35 35.56 3572 177-333} 141 1879.4 ik, matagord. A 3.5 34.89 3.87 17.01 34.89 3.87 17.01 143 1877.8 IE, matagord. A 3h) 39.58 3.99 15632 40.26 3.84 14.80 143 1877.8 1E; matagord. A 355 42.35 3.89 13.19 143 1877.8 L. matagord. A 3.5 38.87 3.65 15.90 Bob Allen Keys Core 6A ! 1994.0 12% Setipunct. A or A-1 1 18.70 4.35 11.43 18.70 4.35 11.43 1 1994.0 12 setipunct. A or A-1 2 31.30 32011 12.76 ] 1994.0 12 setipunct. A or A-1 2) 30.50 4.03 13.05 1 1994.0 12 setipunct. A-2? 2 25.22 4.11 12.52 3 1992.1 1 setipunct. A 2; 20.27 3198 Se 20.27 3.93 LIS 3 1992.1 Ie setipunct. A-1 or A-2 1 20.88 4.58 12.25 3 1992.1 P. setipunct. A-3 1 20.12 3.99 12.55 3) 1992.1 (P setipunct. A-2 1 22.82 4.16 12.61 Table 3.—Continued. Depth (cm) iS) mMyNy hd td to nn ~ 101 101 105 107 107 109 113 113 117 121 125 125 127 133 Year 1986.3 1986.3 1986.3 1980.6 1980.6 1980.6 1978.7 1976.7 1976.7 1974.8 1974.8 1972.9 1971.0 1971.0 1969.0 1969.0 1965.2 1965.2 1963.3 1963.3 1961.3 1961.3 1959.4 1959.4 1955.6 1953.7 1953.7 1949.8 1949.8 1938.3 1934.4 1934.4 1930.6 1928.7 1926.7 1926.7 1921.0 1919.0 1919.0 1915.2 1L9I3"3 1911.3 1911.3 1907.5 1907.5 1905.6 1897.9 1897.9 1894.0 1892.1 1892.1 1890.2 1886.3 1886.3 1882.5 1878.7 1874.8 1874.8 1872.9 1867.1 Genus UNO MO URC UN URU NU RTUNC UN UR IU UUs UI Ul UUs, Ul. Un Ua 0) Ui UN Ul Ul Un sUrU: ss Un Un Uli 0! 5.20) 50 AUS 20) FU, AU) sU) FU) GUIrU FU 0 80 Ful Fu! Te) Tue! ro itd Species setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. Setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. Setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. setipunct. Setipunct. setipunct. setipunct. setipunct. OSTRACODE SHELL CHEMISTRY: DWYER AND CRONIN 263 Mg/Ca St/Ca Na/Ca Molt VPI Mg/Ca Sr/Ca Na/Ca (avg.) (avg.) (avg.) A or A-1 D 21.97 4.14 13.92 21.81 4.16 14.15 A or A-1 2 21.65 4.18 14.39 A-2 2 31.15 4.11 11.82 A I 22.22 4.15 14.27 22.22 4.15 14.27 A-l I 17.69 4.14 11.27 A-4 l 27.89 3.98 8.85 A-2 1 32.08 4.44 13.65 A-2? 2 26.26 3.99 11.79 A-3 2 19.93 3.94 11.08 A? I 22.57 4.30 12.83 26.53 4.39 13.19 A 1 30.49 4.48 13.54 A I 23.03 4.11 13.00 23.03 4.11 13.00 A 2 17.63 4.11 14.17 17.97 4.13 14.24 A 2 18.31 4.16 14.31 A l 22.56 4.12 11.35 21.82 3.82 10.94 A p 21.08 3.51 10.53 A 2 24.66 4.55 13.69 24.41 4.38 13.24 A or A-l 2 24.15 4.21 12.79 A 2 21.70 4.41 14.40 21.42 4.44 14.38 A 2 21.15 4.46 14.36 A 2 24.04 4.24 12.34 23.27 4.18 12.11 A 2 22.50 4.13 11.87 A 2 20.44 4.00 10.83 20.35 4.05 12.25 A 2 20.26 4.11 13.67 A 2 16.36 4.09 12.47 16.36 4.09 12.47 A 2 17.39 3.82 12.50 17.54 4.02 12.45 A 2 17.69 4.22 12.40 A D 19.61 4.36 13.72 19.46 4.37 13.96 A 2 19.32 4.38 14.20 A 2 24.36 3.83 10.39 4.36 3.83 10.39 A l 24.49 4.12 12.59 23.34 4.17 12.91 A 2 22.19 4.21 13:23 A 2 25.86 4.26 13.93 25.86 4.26 13.93 A I 20.71 4.39 14.09 20.71 4.39 14.09 A 2 29.29 4.22 13.29 26.33 4.23 12.66 A 2 23.36 4.25 12.02 A 2 18.58 4.07 13.04 18.58 4.07 13.04 A D 18.91 3.94 12.13 19.93 4.13 12.48 A l 20.96 4.32 12.82 A 2 21.36 4.14 13.46 21.36 4.14 13.46 A 2 23.06 4.11 13.03 23.06 4.11 3.03 A 2 21.83 4.11 12.43 20.96 4.23 12.29 A 2 20.09 4.35 12.16 A 2 24.06 4.73 12.07 20.53 4.31 12.40 A 2 17.00 3.90 12.73 A 2 16.90 4.27 13.58 16.90 4.27 13.58 A 2 17.82 4.03 11.15 18.64 4.18 11.06 A D) 19.45 4.34 10.96 A 2 23.10 4.26 12.42 23.10 4.26 12.42 A 1 22.67 4.43 11.92 22.79 4.37 11.95 A I 22.90 4.32 11.98 A 2 19.20 4.02 12.49 19.20 4.02 12.49 A 2 15.02 4.08 11.43 17.44 4.09 11.89 A 19.87 4.11 12.35 A 2 22.47 4.29 13.09 A 2 19.04 4.05 i17/ A 2 16.69 3.31 10.27 17.43 3.89 11.93 A 2 18.18 4.48 13.59 A 2 20.75 4.03 12.62 A 1 16.55 4.18 12.81 17.07 3.99 12.14 264 Table 3.—Continued. Depth (cm) Year Genus Species 133 1867.1 12, setipunct. 135 1865.2 Ps setipunct. 137 1863.3 12 setipunct. 137 1863.3 je, setipunct. 139 1861.3 P: setipunct. 141 1859.4 iP: setipunct. 141 1859.4 P: setipunct. 141 1859.4 ie setipunct. 143 1857.5 iP: setipunct. 143 1857.5 P: setipunct. 143 1857.5 12, setipunct. 145 1855.6 IZ setipunct. 145 1855.6 P: setipunct. 147 1853.7 P: setipunct. 151 1849.8 PR: setipunct. 153 1847.9 len setipunct. 153 1847.9 PB. setipunct. 155 1846.0 ie setipunct. 155 1846.0 12 setipunct. 157 1844.0 12 setipunct. Little Madeira Core T24 1 1991.4 IE setipunct. 1 1991.4 iP: setipunct. 11 1955.7 P. setipunct. 11 1955.7 lem setipunct. 27 1898.6 P: setipunct. 33 1877.1 iP setipunct. 37 1862.9 P. setipunct. 37 1862.9 12 setipunct. 39 1855.7 12 setipunct. 49 1820.0 1e. setipunct. 53 1805.7 P. setipunct. 59 1784.3 12 setipunct. 79 1712.9 P: setipunct. Park Key Core 23A Site 11 1998.0 E: matagord. 1 1993.7 IBS matagord. 1 1993.7 L. matagord. 1 1993.7 ib matagord. 3 1991.2 Ig; matagord. 3 1991.2 Ik; matagord. 3 1991.2 L. matagord. 5 1988.6 Ik, matagord. 5 1988.6 JE matagord. 5 1988.6 ibs matagord. 7 1986.0 Te matagord. 7 1986.0 ths matagord. 7 1986.0 IE matagord. 9 1983.5 | Be matagord. 9 1983.5 1B matagord. 9 1983.5 Ihe matagord. 11 1980.9 Ibs matagord. 11 1980.9 Ibs matagord. 11 1980.9 bs matagord. 13 1978.3 Ee matagord. 13 1978.3 E. matagord. 15 1975.8 E. matagord. 15 1975.8 Ee matagord. 17 1973.2 Ibs matagord. Prrrrrrrrrrrrrrrrrre | >>> rrr rrrrr sd ~) rrr rrrrrrrrrrrrrrrrrerre Molt BULLETIN 361 VPI NN wn NNNNNNNMNNNNNN VN Bo ey eo © CCE || eFNWN 34.569 S522 36.764 Sr/Ca 3.80 4.05 4.23 4.05 4.30 4.09 4.14 4.18 4.25 3.61 4.59 4.56 3.48 4.31 4.02 4.39 3.97 Na/Ca 11.47 9.88 12.76 12.68 13.07 13.10 12.24 10.84 12.39 9.63 12.36 11.44 9.98 10.31 11.66 12.71 10.46 12.68 12.26 12.64 8.64 10.54 10.00 10.26 9.96 8.64 8.23 11.05 10.19 6.74 10.03 8.92 8.49 14.895 15.444 17.609 23.407 16.441 16.880 17.019 14.916 14.189 18.559 19.459 14.429 14.765 17.307 17.574 15.879 15.149 13.350 19.202 14.738 20.084 14.296 13.189 19.534 Mg/Ca (avg.) 19.82 20.21 22.82 17.94 23.29 20.11 20.48 26.66 30.70 NNN = WwW fOr wn ~_ mnnv wn in Nn sot D Ww AN 35.69 37.42 40.07 36.89 37.56 41.27 34.92 38.09 Sr/Ca (avg.) 4.14 4.15 3.96 373. 3.78 Na/Ca (avg.) 11.46 9.59 10.13 9.96 8.64 9.64 10.19 6.74 10.03 8.92 8.49 14.895 18.82 16.78 15.89 16.22 16.92 15.90 17.41 13.74 16.40 Table 3.—Continued. OSTRACODE SHELL CHEMISTRY: DWYER AND CRONIN Depth (cm) 17 17 Ow = NNNNNNDN LV NIX NUNN WwW tN ~ 45 59 Sy) Year 1973.2 1973.2 1970.6 1970.6 1970.6 1968.1 1968.1 1968.1 1965.5 1965.5 1965.5 1962.9 1962.9 1960.4 1960.4 1960.4 1957.8 1957.8 1955.3 1955.3 1955:3 1952.7 1950.1 1950.1 1950.1 1947.6 1947.6 1947.6 1945.0 1942.4 1942.4 1939.9 1939.9 1939.9 1937.3 1937.3 1937.3 1934.7 1934.7 1934.7 1932.2 1932.2 1929.6 1929.6 1927.1 1927.1 1927.1 1924.5 1924.5 1921.9 1921.9 1919.4 1919.4 1919.4 1916.8 1916.8 1911.7 1960.5 Genus Species JSC URC SE Teer Sst fest [est fest dese lest jest fest fest Jose Jesh de=Falentolesialesu[estlest [St lente dgsd testitest deal leatalead dss tiles testes Tiles il este let lel ctl estal cfc] alesis etilea lls tal osted eas lel ss eilss lest ll sal esol Il ca) matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. matagord. rrr PrPrrrrrrrrrerrrrrrrrrPrrPrPrPrPrPrPerPrPrrPrrrrrrrrrrrrrrrrrrrrrrrrd>d Mg/Ca Sr/Ca Na/Ca 39.529 3.834 13.869 37.99] 3.627 15.795 40.801 3.941 16.625 46.646 3.505 17.558 34.976 4.248 19.266 43.454 3.955 18.219 38.430 3.916 18.228 31.993 3.815 15.805 41.083 3.730 13.934 44.853 3.805 17.531 44.190 3.815 12.135 43.813 3.832 14.306 27.063 3.099 10.673 37.161 3.845 15.234 35.081 3.762 14.894 39.754 3.661 18.617 42.313 4.079 14.168 34.934 4.025 15.124 38.633 3.834 18.052 36.882 3.639 15.555 47.863 4.055 13.613 38.465 35712 18.343 32.028 3.720 14.424 35.132 3.618 15.580 46.068 3.852 15.419 39.966 3.877 17.063 36.811 3.928 17.330 49.168 4.240 23.390 37.609 3.710 16.161 39.738 3.832 11.676 43.387 4.214 14.597 36.224 3.436 14.897 40.645 4.357 19.004 33.668 3.645 14.923 40.307 3.804 16.482 38.335 3.540 16.605 38.279 4.019 15.730 SESH 31935 16.233 34.743 3.170 13.040 34.881 3.667 16.925 33.969 3.978 15.483 46.949 4.500 13.614 34.572 3.568 14.314 35.948 4.032 18.054 30.785 375i 20.072 46.299 3.431 14.939 31.636 3.900 13.483 40.095 4.165 16.014 37.119 3.855 17.116 39.917 3.587 17.332 37.298 3.763 16.494 44.702 S725 13.998 42.021 3.638 15.739 43.679 4.002 16.583 37.332 4.188 16.794 47.322 3.608 17.898 32.995 SV IBY) 19.137 31.379 3.681 16.232 Mg/Ca (avg.) 40.81 37.96 38.62 41.13 37.74 41.98 37.61 41.56 36.85 38.97 35.59 33.00 35.54 Sr/Ca (avg.) 3.90 3.90 4.01 Na/Ca (avg.) 17.82 17.42 14.65 15.74 19.26 16.16 13.14 16.27 16.27 15.40 16.91 19.14 16.12 Table 3.—Continued. BULLETIN 361 Depth (cm) Year Genus Species 69 1906.5 Ib matagord. 69 1906.5 Ib matagord. 7p 1904.0 Ie: matagord. 71 1904.0 Te, matagord. 71 1904.0 E. matagord. 73 1901.4 os matagord. 73 1901.4 L. matagord. 73 1901.4 IG, matagord. 75 1898.8 Ibs matagord. WY 1896.3 1B matagord. 77 1896.3 E. matagord. 77 1896.3 1B matagord. 79 1893.7 1B matagord. 19) 1893.7 E. matagord. a2) 1893.7 Es: matagord. 83 1888.6 ibe matagord. 83 1888.6 Ih matagord. 83 1888.6 1B matagord. Manatee Bay Core MB1 1 — EE. matagord. 1 — 1B matagord. 1 — | es matagord. 3 — EE. matagord. 3 — E matagord. 3 = E. matagord. 5 a Es matagord. 5 — hs matagord. =) —_— iD matagord. 7 —- ES matagord. 7 —_ jb matagord. 7 — ES matagord. 9 — E. matagord. 9 — j be matagord. 9 —_— L. matagord. 11 — TE matagord. 11 — Ii matagord. 11 —_— E. matagord. 13 — 1B matagord. 13 — ike matagord. 13 — E. matagord. 15 —_ Be matagord. 15 — E. matagord. 15 — ib; matagord. 19 — Ib, matagord. 19 — 1B matagord. 19 — Ik. matagord. 21 — Jb matagord. 21 — / Bs matagord. 21 — ] Bs matagord. 25 — 1b matagord. 25 — iL. matagord. 25 — LE. matagord. 27 — 18s matagord. 27 — Ibs matagord. AG] — [hs matagord. 29 — Ik. matagord. 29 — iE. matagord. 29 — Ibs matagord. 31 — J be matagord. >PrPrPrrrrrrrrrrrrerre >SPPPr rr rrPrPrPrrrrEESeerrrrrrrrrrrrrrrrePrrrrrr VPI Wh PWW PW WW W es) WNONWH WWE HK KWH HE WN hy WwW WW WwW WwW oe WW Www Sr/Ca 3.825 3.495 3.837 3.877 S92 3.648 4.142 4.164 3.740 3.959 3.910 3.676 3.973 4.064 3.700 3.954 3.702 4.178 3.62 3.89 3.91 4.09 4.23 Si 3.71 3.85 4.19 3.92 3.83 4.26 4.31 4.22 3.78 3.91 4.13 4.10 3.61 3.60 4.38 4.31 4.13 4.00 3.59 3.61 4.07 3:93 S77 4.09 3.64 3.72 4.23 3.68 3.40 3.58 4.00 3.47 B07) 3152 Na/Ca 15.165 16.964 14.760 18.267 14.161 16.474 13.580 17.895 15.468 19.349 15.632 16.025 16.350 15.975 14.722 13.319 17.053 18.043 17.07 14.76 14.18 12.61 24.29 14.87 14.47 15.87 12.98 13.68 15.56 16.03 16.77 15.25 14.10 1539 16.93 13.79 14.47 10.24 17.05 16.24 SESS) 13.69 12.09 13.66 12.93 18.29 itil} 12.34 13.36 16.79 15.85 15.78 14.11 14.34 13221 14.85 14.76 12.85 Mg/Ca (avg.) 36.84 33.69 35.02 36.78 38.91 33.91 37.54 36.26 37.46 40.02 40.75 31.66 36.51 40.31 Sr/Ca (avg.) us (or) ie) eS) \o i) 4.00 4.10 4.15 3.76 WwW \o Ww 3.47 Na/Ca (avg.) 15273) 15.68 15.19 15.34 17.26 14.44 15.09 15.37 15.37 13.92 15.09 15.33 14.75 14.28 13.22 OSTRACODE SHELL CHEMISTRY: DWYER AND CRONIN 267 Table 3.—Continued. Depth Mg/Ca Sr/Ca Na/Ca (cm) Year Genus Species Molt VPI Mg/Ca St/Ca Na/Ca (avg.) (avg.) (avg.) 31 — Ee. matagord. A 2 34.09 3.43 13.58 33 — Ib. matagord. A 3 33.24 3332 10.93 38.04 3.69 12.56 33 — Ibs matagord. A 3} 42.84 4.06 14.19 35 — EE matagord. A 4 31.02 3.56 14.80 34.18 Shi/il 15.46 35 — T.. matagord. A 37.34 3.86 16.12 37 _ L. matagord. A 3 42.76 3.80 14.69 40.60 3.78 13.48 37 a IE matagord. A 3 38.44 S77 12.27 39 — L. matagord. A 3) 36.24 3.58 14.14 41.04 3.63 14.30 39 = iB; matagord. A 3 40.93 355 15.08 39 —_— Ee. matagord. A 3 45.96 SET) 13.68 41 — Ike matagord. A 3 41.12 3.30 11.88 37.72 3.71 12.72 41 — IES matagord. A 2 39.08 3.91 14.16 41 os EE matagord. A 2 32.97 3.93 12:12 43 — Ib matagord. A 3 35.84 3193 14.50 35.84 3.93 14.50 45 — E. matagord. A 3 36.79 3.64 12.61 Slat 3.66 Ne Igi7/ 45 _ Jb matagord. A 4 25:95 3.67 13.74 47 — IE matagord. A 3 39.23 S313 13.96 42.06 3:38 14.17 47 — Ibs matagord. A 3 41.76 3.38 13.80 47 — Te matagord. A 3 45.18 3.49 14.75 49 = IE. matagord. A 3 33.74 Sail 113'58) 39.42 3.45 13:33) 49 os jE. matagord. A 3 39.95 3.09 13.72 49 _- jb. matagord. A 3 44.58 3.47 12.73 Sl oS IE. matagord. A 4 40.64 3.65 13.92 35.47 3.62 14.16 Sil — Te matagord. A 3 29.99 3.80 EV 78} 51 a Ibe matagord. A 4 35579) 3.41 14.82 53 — jE matagord. A 3} 36.93 3.42 14.52 36.95 3.64 14.60 53) _ 1% matagord. A 3 35.61 3.61 13.45 53 — Es matagord. A 2 38.31 3.90 15.82 55 — IL, matagord. A 3 32.62 3.60 17.79 37.04 3.61 16.09 55 — cE matagord. A 4 38.62 3.48 15.51 55 — E. matagord. A 3) 39.87 375) 14.98 57 —_ 1b matagord. A 4 26.06 6.83 143.25 33.10 4.83 57.34 Sy/ — Ee: matagord. A 3 35.01 3.98 12.33 57 — IL. matagord. A 3 38.22 3.67 16.44 59 — IE. matagord. A 3 40.17 3.79 15.41 39.89 3.90 15.02 59 —_— 1B, matagord. A 3 3750 4.04 15.78 59 — IE. matagord. A 2 42.00 3.88 13.87 61 — Es matagord. A 2 26.79 3.46 14.73 32.40 3.49 14.30 61 — Ibs matagord. A 3 36.57 3.98 14.76 61 — IES matagord. A 3 33.83 3.05 13.40 63 — iE matagord. A 4 35.64 3.54 12:39 36.70 Br? 14.21 63 — 183 matagord. A 2 33.18 3.60 15.80 63 os EL. matagord. A 3 41.26 3.42 14.44 65 — JE matagord. A 3) 37725) 3.43 14.57 37.25 3.43 14.57 67 — EE matagord. A 3) 43.09 4.29 15.92 40.62 S107 14.41 67 — ih matagord. A 3} 35.03 3.75 eats 67 — IE: matagord. A 4 43.74 3.86 14.19 69 — iL. matagord. A 5 34.67 3.36 14.97 34.67 3.36 14.97 71 — IL, matagord. A 2 33.00 3.60 11.71 34.40 S12: 13.59 71 os ibs matagord. A 2 35.79 3.85 15.48 73 a Ihe matagord. A 3 35.69 3.64 14.28 37.16 3.81 14.20 73 — Jb matagord. A 3 47.17 3.78) 14.32 73 — Ib matagord. A 28.62 4.00 14.01 75 — IE matagord. A 36.67 3.99 15.10 41.07 4.00 16.15 75 — IE. matagord. A 45.46 4.02 17.20 117 = Je setipunct. A 5 24.49 3.91 8.94 23.96 3.61 9.07 117 — P: setipunct. A 5 21.25 B35 8.44 117 — P: setipunct. A 5 26.15 Shei) 9.84 115 — P. setipunct. A 5 24.22 3.97 6.64 23.79 3.67 7.71 Table 3.—Continued. BULLETIN 361 Molt Depth (cm) Year Genus Species 115 — PR setipunct. A 115 — 1p setipunct. A 113 — Ie setipunct. A 113 = P. setipunct. A 107 — P. setipunct. A 107 — P setipunct. A 105 — P setipunct. A 103 — 12 setipunct. A 103 = 12 setipunct. A 103 — 1? setipunct. A 101 — 1 setipunct. A 101 — P, setipunct. A 99 — Pp setipunct. A 9) = P. setipunct. A 97 — 12 setipunct. A 97 — Pp setipunct. A 97 — Pp setipunct. A 95 — Pp: setipunct. A 95 — P. setipunct. A 93 — 12% setipunct. A 93 — 1% setipunct. A 91 — Ps setipunct. A 91 — 12 setipunct. A 89 — iP setipunct. A 89 — / 2; setipunct. A 89 = 12. setipunct. A 87 — P: setipunct. A 85 — 12 setipunct. A 83 —_— 12. setipunct. A 83 — 1 setipunct. A 83 — 12 setipunct. A 81 — Be setipunct. A 81 _ P. setipunct. A 81 — lez setipunct. A 79 Pp: setipunct. A 79 — RP: setipunct. A 79 — le setipunct. A 77 — 1? setipunct. A WAL — P: setipunct. A 75 — 12 setipunct. A 75 — IP. setipunct. A Ws) — PB: setipunct. A 73 — Bs setipunct. A 73 so RB: setipunct. A 73 — P. setipunct. A 71 — Je setipunct. A 71 — Je, setipunct. A 67 — Jee setipunct. A 67 — P; setipunct. A 63 — PR: setipunct. A 61 — P: setipunct. A 61 a IP: setipunct. A 55 — P: setipunct. A 333) —- 12 setipunct. A 33 _— Pp: setipunct. A 51 — ied, setipunct. A VPI Nan h BOAAKHKHKHNANnaAnnnnnnnnnn wh RUAN HL WNWNA LA A n WwwWwn kW WWNN WwW WWnN WwW ty Sr/Ca Na/Ca 8.66 7.82 11.28 8.80 6.60 6.68 5.10 10.90 7.59 15.73 4.54 7.90 5.58 6.24 9.30 8.88 10.01 7.01 7.19 9.08 8.46 8.74 8.18 6.03 8.16 6.29 WAS) 9332 8.92 9.88 6.79 7.00 13.08 12.69 9.94 9.96 9.71 6.13 8.23 7.86 S)5)9) 8.96 8.14 UT 8.08 8.31 2.92 8.89 8.63 8.92 9.09 8.21 6.82 8.44 q95 8.57 Mg/Ca (avg.) 29,11 Sr/Ca (avg.) 4.00 3.85 Na/Ca (avg.) 7.10 8.46 6.83 Vas) 932 8.53 7.00 12.89 9.87 7.18 8.78 8.00 OSTRACODE SHELL CHEMISTRY: DWYER AND CRONIN 269 15 20 25 30 35 40 45 Salinity (ppt) Salinity (ppt) Water Temperature (°C) e Febraury 1998 + July 1998 o February 1999 Text-figure 6.—Mg/Ca and Sr/Ca ratios of shells of Loxoconcha matagordensis from modern vegetation samples plotted versus salinity and temperature at time of collection. 270 Text-figure 7—Mg/Ca, Sr/Ca, and Na/Ca ratios of fossil ostracode shells versus depth from sediment cores collected from Russell Bank, Park Key, Bob Allen Keys, Little Madeira Bay, and Manatee Bay. Loxoconcha matagordensis (filled circles); Pereatocytheridea setipunctata (open circles). Russell Bank Core 19B Mg/Ca (avg) 15 20 25 30 35 40 45 50 Depth (cm) Park Key Core 23A Mg/Ca (avg) 15 20 25 30 35 40 45 50 0 10 20 30 40 50 Depth (cm) 60 70 80 90 Bob Allen Core 6C Mg/Ca (avg) 15 20 25 30 35 40 45 50 Depth (cm) 160 BULLETIN 361 Sr/Ca (avg) 3.0 3.5 0 10 20 4.0 Sr/Ca (avg) 3.5 4.0 Sr/Ca (avg) 3.5 4.0 140 160 4.5 4.5 Na/Ca (avg) 5.0 80 Depth (cm) 100 110 120 130 140 150 Na/Ca (avg) Depth (cm) Na/Ca (avg) 12 4.5 15 18 20 pth (cm) De oh (2) oO 160 OSTRACODE SHELL CHEMISTRY: DWYER AND CRONIN 271 Manatee Bay Core MB1 Mg/Ca (avg) Sr/Ca (avg) Na/Ca (avg) 15 20 25 30 35 40 45 25S Ol 3-0) 4:0) 425) 50 5 10 15 20 Depth (cm) Depth (cm) Depth (cm) Little Madeira Bay Core T24 Mg/Ca (avg) Sr/Ca (avg) Na/Ca (avg) 15 20 25 30 35 40 45 3.0 35 40 45 5.0 5 10 15 20 10 20 30 40 Depth (cm) Depth (cm) Depth (cm) 50 60 60 70 70 O--------0, ce) i ! 1 1 70 ' I I fe) 80 80 Text-figure 7.—Continued. 272 BULLETIN 361 ligible which is further supported by the overlapping values obtained for down-core shells (below). DETERMINATION OF PARTITION COEFFICIENTS From the water and shell chemistry results, we de- termined the partition coefficients for Mg ands Sr for Loxoconcha matagordensis. For these determinations we used the grand average of Mg/Ca and Sr/Ca ratios for all of the Florida Bay water samples (Table |) and the grand average of Mg/Ca and Sr/Ca ratios measured on 171 modern shells (Table 2). The determinations also assume an average water temperature of 26.5°C (average calculated from over 100 February and July water temperature measurements from 1997 and 1998; Brewster-Wingard er al., this volume). Under these conditions the following K, are derived: Kp.me = (36.98 mmol/mol Mg/Ca) = (4980 mmol/mol Mg/Ca) = 0.00743 Ks, = (3.81 mmol/mol Sr/Ca) = (8.46 mmol/mol Sr/Ca) 0.4499 Il The Kj, 1. of 0.00743 is similar to the value of 0.00756 calculated from the Mg data reported for shells of liv- ing specimens of open-marine Loxoconcha by Cadot and Kaesler (1977). Kx, is not determined because Na is apparently a non-lattice bound foreign ion within calcite (Busenberg and Plummer 1985). The calculated K, values are used below, in conjunction with the wa- ter me/Ca-salinity relationship in Florida Bay, to cal- culate estimates of past salinity of Florida Bay. METAL/CA TRENDS IN FossiL SHELLS FROM SEDIMENT CORES Down-core shell me/Ca ratios are listed in Table 3 and summarized in Text-figure 7, which include data from two genera. Although changes in average salinity and temperature are considered the primary factors in controlling ostracode shell chemistry, some of the high frequency variability in Mg/Ca ratios may result from a combination of other factors. These include: (a) se- cretion of shells during different seasons, reflecting strong seasonal fluctuations in temperature and salinity of Florida Bay, (b) bioturbational mixing of penecon- temporaneous shells, and/or, (c) short-term (hours to days) variability in salinity and temperature at a site, which may not be representative of longer term con- ditions. In order to evaluate inter-annual- to decadal- scale variability, we minimized the high-frequency sig- nal by calculating intrasample means for each me/Ca ratio and these are shown in Text-figure 7 versus core depth. At Russell Bank, Park Key, and in Manatee Bay, Mg/Ca ratios for Loxoconcha fluctuate downcore be- tween about 30 and 45 mmol/mol. Overall, the values for down-core specimens of Loxoconcha overlap with values obtained for modern Loxoconcha shells. At Bob Allen Key and Little Madeira Bay, Loxo- concha was not as abundant downcore so we analyzed shells of the genus Peratocytheridea. Metal/Ca ratios for Peratocytheridea, however, appear to show sys- tematic differences from those of Loxoconcha. In gen- eral, Peratocytheridea Mg/Ca ratios are offset toward lower values, averaging between 20 and 25 mmol/mol, values that are comparable to the lowest values ob- tained for modern Loxoconcha shells. Sr/Ca ratios in Peratocytheridea shells generally show the opposite trend, yielding average values from 4.1 to 4.3 mmol/mol, approximately 15% higher than average values for Loxoconcha. Like Mg/Ca ratios, Peratocytheridea Na/Ca ratios are offset toward lower values relative to Na/Ca for Loxoconcha. The reason(s) for the differences observed between Loxoconcha and Peratocytheridea are unclear. The differences could be related to phylogenetic effects or might possibly indi- cate that these two genera preferentially secrete their adult shells at different times of the year, 7.e., Perato- cytheridea primarily during the winter months. Oscillations in the ostracode Sr/Ca ratio record from Russell Bank core generally show good correspondence with the pattern of variability observed in the Mg/Ca record (Text-fig. 7). However there are clear differences in the magnitude of the shifts in Sr/Ca and Mg/Ca and some of the changes appear to be out of phase. The reason for the variability between Sr/Ca and Mg/Ca re- cords is not known. Possibly, it results from a differ- ential response to changes in water temperature. Unlike the co-precipitation of Mg into CaCO , which is posi- tively correlated with temperature, Sr uptake may de- crease with increasing temperature (reviewed in Morse and Mackenzie). Another possible factor is the effect of calcium carbonate production within Florida Bay. Bio- genic aragonite, the dominant mineral produced in Flor- ida Bay (Stockman et al., 1967), co-precipitates large amounts of Sr at a Sr/Ca ratio that is similar to slightly lower than the Sr/Ca ratio of seawater. Thus, assuming continued high production of aragonite in Florida Bay, the Sr/Ca ratio of evaporatively concentrated, hypersa- line bay waters would likely show only a slight increase in Sr/Ca, whereas the Mg/Ca ratio of the same waters would increase more sharply as Ca is removed by ara- gonite formation and Mg is virtually unaffected because it is all but excluded from the aragonite lattice. A third possible factor is the relatively small shift in Sr/Ca ratio OSTRACODE SHELL CHEMISTRY: DWYER AND CRONIN 273. Russell Core 19B Mg/Ca (mmol/mol) L. matagordensis 2000 1990 1980 1970 1960 1950 1940 1930 1920 Year 1910 1900 1880 1870 1860 1850 --o-- Rainfall 1840 170 160 150 140 130 120 110 170 160 Annual Rainfall (cm) NOAA Area 5 5-year running mean Park Core 23A Mg/Ca (mmol/mol) L. matagordensis Annual Rainfall (cm) NOAA Area 5 5-year running mean Bob Allen Core 6A Mg/Ca (mmol/mol) P. setipunctata 5 10 15 20 25 30 2000 1990 1980 1970 1960 1950 1940 1930 1920 1910 1900 1890 1880 1870 1860 1850 1840 140 130 120 110 170 160 150 140 130 120 110 Annual Rainfall (cm) NOAA Area 5 5-year running mean Text-figure 8 —Ostracode Mg/Ca ratios versus age from Russell, Park, and Bob Allen Keys sediment cores plotted along with 5-year running mean of annual rainfall. Solid bars along left axis mark years of strong El Nino events. with salinity compared to that of Mg/Ca (Text-fig. 5). As a result of these potential temperature and water chemistry effects on Sr/Ca ratios, ostracode Mg/Ca ra- tios may be a more a sensitive indicator of salinity changes in Florida Bay. This contention is generally supported by the higher dynamic range displayed by the down-core Mg/Ca records and the apparent corre- lation between shell Mg/Ca ratios and rainfall (below). COMPARISON OF MG/CA AND HISTORICAL RAINFALL To investigate whether the ostracode Mg/Ca ratios might be related to salinity variability, we compared downcore trends to historical rainfall records. We fo- cus our discussion on the records from Russell, Bob Allen, and Park cores as they have the most robust chronostratigraphy. Text-figure 8 shows the down-core records of ostracode Mg/Ca ratios versus year. Because rainfall derived runoff from peninsular Florida is such an important factor controlling the salinity of Florida Bay, we also show an instrumental record of south Florida annual rainfall which is available back to 1895 (NOAA Data Archive). The rainfall data are shown as a 5-year running mean to approximate the sampling frequency of the sediment cores. In the Russell core, except for a single-specimen spike in the late 1890’s, Mg/Ca ratios show a gradual decrease with little variation from the 1870’s until around 1915, although the sampling resolution and age model are not as good as those for the upper part of this core. The succeeding interval, from 1915 to 1998 (the top most data point in the Russell record is an average of 4 living specimens collected from this site in 1998), is characterized by a slight overall increase in Mg/Ca that is punctuated by moderate to large-scale fluctuations. Eight periods of high Mg/Ca ratios are observed between 1900 and 1998 (Text-figure 8). 274 BULLETIN 361 Russell Bank Core 19B 100: 110: 120: Annual , Rainfall (cm) 140 oO i=} 150: 160: ; comnans Rainfall 170 Ostracode Mg/Ca - Based Salinity vs. Rainfall Russell Salinity 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 Text-figure 9.—Ostracode Mg/Ca-based salinity estimates for Russell core 19B and 5-year running mean of annual rainfall. Salinity derivation discussed in text. SM designates intervals of relative salinity maximum. A comparison of the Mg/Ca record from the Russell core to the rainfall record reveals many similarities (Text-figure 8). For example, the rainfall data indicate that since the late 1950’s there have been 3 quasi-de- cadal oscillations in precipitation over southern Flori- da. While the amplitude correspondence varies, within the resolution of sediment chronology, the three rain- fall oscillations are matched one-for-one by oscilla- tions in ostracode Mg/Ca ratios. Over this time inter- val, peaks in Mg/Ca occur during dry intervals in the early 1960’s, mid-to-late 1970's, and the late 1980’s, all periods of known hypersalinity within Florida Bay. The decadal-scale correlation between rainfall and Meg/Ca persists in the earlier part of the records as well. Based on the rainfall record, this was a period of low amplitude rainfall oscillations relative to the last 50 years, a pattern that also appears in the Mg/Ca record. Thus, Mg/Ca and rainfall show a correspon- dence over multi-decadal timescales. In addition to the longer-term correlation, it also ap- pears that single-year climate events may be recorded in the Mg/Ca record. For example, four of the extreme minima over the last century closely correspond with years when the El Nino southern oscillation index (SOD was strongly negative (Text-fig. 8). Typically, south Florida receives unusually high dry-season rain- fall under such climate conditions (Douglas and En- glehart, 1981), presumably leading to significantly lower salinity in Florida Bay. Meg/Ca records from the Park and Bob Allen cores also correspond with the rainfall record, though the similarities are not as strong as in the Russell core. This may be a result of the lower resolution sampling within these cores or in the case of Bob Allen, due to an ecological effect related to Peratocytheridea. An- other possibility is that these sites have stronger local effects than Russell Bank. The Bob Allen and Park core sites appear to be located on the leeward side of complexes of islands and broad, shallow mudbanks which often experience wide temperature and salinity shifts relative to more open waters of Florida Bay. In contrast, the Russell Bank core site appears to be lo- cated in a much smaller lee on a narrow mudbank that extends out into open waters of the largest and deepest sub-bay within the eastern sector of Florida Bay. Thus, the Russell Bank site may be better situated to monitor large-scale changes in Florida Bay. A PALEOSALINITY CURVE FOR CENTRAL FLORIDA BAY Using the down-core Loxoconcha Mg/Ca ratios and the provisional Kp. for Loxoconcha, we calculated estimates of past Mg/Ca ratios of Florida Bay water and converted them to estimates of past salinity based on the correlation between salinity and Mg/Ca,,,,., (Text-fig. 5). Text-figure 9 shows ostracode Mg/Ca- based salinity estimates derived for Russell Bank and the south Florida rainfall record. Two extreme values at intervals equivalent to 1963 (91 ppt) and 1897 (113 ppt) are excluded from this plot. Calculated salinity estimates range from 13 to over 50 ppt. The overall average is 32 ppt with around two thirds of the values falling between 20 and 43 ppt. The salinity estimates are quite reasonable, strongly overlapping with the range of instrumental salinity measurements taken at or near this site over the last 50 years which range from 10 to 55 ppt (Swart et al., 1996, Halley et al., 1995). One notable example is the salinity during the late 1980’s which has been widely discussed in the context of Florida Bay seagrass dieotfs. Another is the high salinity recorded during the mid 1970s (Swart et al., 1996). It is important to note that calculated salinity estimates that are greater OSTRACODE SHELL CHEMISTRY: DWYER AND CRONIN AY) than ~42 ppt lie outside the range of our modern cal- ibration data set and thus are unconstrained. These es- timates may be high because the slope of best-fit curve to the Mg/Ca,,.,.. versus salinity data increases contin- uously above 42 ppt, even though it appears that water Meg/Ca ratios begin to plateau near the seawater value. Thus, we might expect that ostracode shell Mg/Ca ra- tios would also plateau at a value around 38 mmol/ mol, a value that is actually exceeded in a number of intervals in the Russell core, perhaps suggesting that Meg/Ca ratios of Florida Bay water increases further with increasing salinity. An alternative interpretation of the trends in shell Meg/Ca is that the signal may be all or partially related to temperature. Temperature and salinity measure- ments collected seasonally for the last few years (Brewster-Wingard er al., 2001) near the Russell core site suggest that temperature and salinity covary at this site, more so than at Bob Allen and Park Key. Given the thermodependence on Mg uptake in Loxoconcha and other ostracode genera (Cadot and Kaesler, 1977; Dwyer et al., 1995), the increased uptake of Mg re- sulting from higher water Mg/Ca ratios at higher sa- linity is likely further enhanced by an accompanying increase in water temperature. This may also help to explain the better correspondence between Mg/Ca and rainfall in the Russell core. Until additional experiments in which adult ostracode shells are grown under controlled salinity and temper- ature conditions, the paleosalinity curve in Text-figure 9 must remain preliminary in nature. Still, the scale of variability in Mg/Ca ratios within all five cores and the estimated salinities are consistent with the hypothesis that salinity fluctuations occur over decadal timescales in Florida Bay. Moreover, the correspondence between interdecadal trends in rainfall and paleosalinity ex- tremes indicates a strong climatic control on Florida Bay salinity. 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Sac eaoa renee ou oanocne nde to eCc ree eoE mete nee caceeToneanreas 83 RARITSTITAD odeasnosacossuonoouoosDUceesadaencobasccononscoodocer 5,6 PELOPHUTCE Ia LOUIS Herter clerseisrleletelsiens sie etslsistlelsiesa settiretars ciaciersiele eerie aes 81 agnicultura Weng CHIMENG vserroctseinetosvsimaecincisicoee seceecer sie cieceeer ae 70 Haarewwiliueea irqbhoy nh eae eRe oanander oaaaAEnSeeenacessacdeenos-ScoskeeooodnG 70 Ei\eeil [DILoYeysi) sao onmenoonpedocuoasedecMarcecenaoare cecontnaaes IZA styl boe) JNVDIS) oo cngenbp eg oc aE ROROO Ene eeee eran 88, 107, 116, 118, 128, 131 PAIL ONECL RST INS S 5 Fotcpeh at tetera cs als Siatotererer a eValeels SisTetotaleledurerelarsielainae 88, 89, 90 AILOTLELL MPR Cet a cocina tite isc eistes io aad nine NTE A Hea 89, 90 PAllLermanthera-(G OMpPHTEn@ wane eni tence ccc de eiddssiseeiae re 88 PALLY ERAT NAVIN poy etcratatchctatotejnjorchsrs cove svolata lola otajtavateratele aterstatane siatetctsretsie bela 72,74, 82 VATIELAT CULLTES yoo sooo alo Siac aie cteroh la oleic wis ate ete ToTwlatelaTe fore Sorsto oem tls Geet 83 PEATIEEIIONNALCTELELES 1h takater, (oistars yetatanieleretdisis|afs oa le ss loots ola dladlieiaisla stave veeinena) LS INDOLE an Mae ean deeean se aecrmimecee gene laren 3 by dropernlodiee-ceaseeeneaa te 103, 105, 106, 107, 121, 130, 131 Ilex\ (dahoon holly) erect ee eee 106, 107, 123, 124, 127, 130 TLYOCHY Plus’ scoceeicetice teak Soe ae es RSE ORE SE ee 89, 90 Inductively Coupled Plasma-Optical Emission Spectrometry (ICP- (0) SS) eAnpaotescospocesenatocoassnpaececnaonacceos 61, 70, 71, 72,74 WON theta pide tein ode ection aieceict eeiseteeer sete carer 123133 TAS Oe, Tsoetes" «Tecan weeempeee she rece teehee eee 59, 85, 86, 94 Uoi-el Nise: qusencasoosoLocopencsseacda JUNIPETUS -x;s\ccidadaten sie saiocete ee se TUSULCI cates racers injeieleielovefelafeinte cloteie oietere are etereeteieta wea ata ae eerste eater Key Eargojllimestone sc saemcnsa- keer ceteeeenseeieeeiscisetteeetet 65 Waguna dewPetenxall (er. tke eases eee ee eee eee ereeeeee 82, 90, 92 Laguncularia (white mangrove) ... 83, 87, 88, 106, 118, 126, 130 INDEX 279 Wakes OKEeEchObDee sep -rienincaee rial cielleeeeelecicanerieeeer 59, 65, 104, 105 WAN SMU ANE sf yotafa cicresorwiarsiaersonmttosiomenvetrcioaer lesbian cecasioa senses secant 92 ATEN EIOLOCENES ccm sias-pe aaiteseteete econ ese 103, 106, 122, 132, 104 [La vnrgstelatalet ePns) nYerelt So opeanmcnaedsorenccsosunadesbnnacaeaoabat cea 915,93 MEAG ee ra caraycrctste se ste Sissieieeieletsraele eis I Cie eT=rsfere eloteiclororeceereyse 10N (2S IPE SUTAIMOSAS, c.-jcisseisiace ists siote seis tatdja stv afolsia eo eiateistaisiclaiotaiaicicteissstatetateictorsiarevs sreieis's 88 IG Cea aeescaaniaartcnte Vaan cae as conte nrinaccrn acco rnracaacccsore acne 67 65 LOG LG TR GRE SoCo SRECE ERE Ernene Somer CoE eae Teneo oOa oa cTonCedSr 89, 90 ILTUIOXES LD a pegarceacnncueacncnaatcbeoccercnonterenaatercaantoopcocae 6 HEL TPLOTALLAIII to Tatas mse eee one. NS SIS 8 2% ala oaiale s BAR OM aRia see iaioes MA a 87 WEL GULA AMBER, oie ociejersyeic\eis sie stats G5 viv sis felsic seiciofna stone rate celelepeleie eles Sales ts 129 AS har ene ore yo ote aie ie hie ici israotes esis sew oe See one mele aloe eee V5 13; 15 IL tHe SEIU) oy obeVes Se panengoeseaanoapcaaccasdosaeosodcoonoe sagaccecuupas 92 BUTTERS HAL KRAVE Ts a rclstay erences elejntstelsislere(aretctoroselareie sistotclaictaroatate steteeloe eens 106 live oak (Quercus) .. 106, 116, 118, 119, 120, 123, 124, 128, 131 HEOKOGONGHAY, tajoccstaistctare sions statalstalattigniee letaeictea alo eratnstetGeiate wlatae om ele wiser ls 5,6 EY COP OGULINAT were fiee ceases eee een eee eeiiceete 107, 123 MEY STLOMICN WAL GtAIM ATINNG) le erate settee sessile ictesoniserversers 106, 107 IM terol ava ley (abl lee ope ace pa deqoceacunotnanecen ann ommencoanocanorccacceoen 90 IN GBR A1bS QoustacsencccsoCereooSseAsBOESaHadCHeOSaeee ee eReCOee ea sanoan 90 MECMEN OTD cutqhoosdasemadader nae aAcasn encode noOmaneroseaAaeT suse 72, 74 TALON? (SUNG OIE) | 55a s0cs0bcndssasanaboosoBdoascopeassbasooaqnon 106 imrnntelamenine (CRaATATO)) cagnoendaccoontendoaaaageosodaoebeaganeacnace 106 1 GG Miewpsouetene ocogocad i aeeCUBaaee cee cnoncesacreracmoroemarcad 5-7 SDRINERINES -ssancnapascbcesadobnseacobadbansagsanoess 70, 72, 73, 74, 75 aan PLOV Caste eericeeen ence ate rsaaniae: 72, 83, 84, 85, 86, 87, 88, 94 (ATO KONS [DEEL Gonogansasaoueobonousodosuenacasosboas 105, 122, 123, 130 mangrove swamp ... 103, 106, 116, 117, 119, 120, 121, 122, 124, 12S SIO MIS2. 7, marl ... 59, 62, 63, 64, 65, 70, 76, 82, 84, 85, 86, 88, 91, 93, 94, 105, 122 PUTAS LIME PA ee cy atet ojc clots wie tine sic oe os cmticinemratclolen 59, 83, 84, 85, 86, 87 WIVAGSTOSIOIAN = sooo eescisiecisieisiess oisiciste 79, 80, 81, 83, 152-154, 157, 159 TEMBRAVINY soooqndosacaspoceagaococconsqce aa scoosaoDeOoAOSUGTOUSDnGGRC 69, 70 Wiramil Canal 332i vic 2/-/-teac aeietscicectesesebicicis acc e ete 2 atceietelearocetejenemeecicte 87 WTADAIPIETINES CONE! lais.tiee er aesrisesiers wate sewrase eitee cme mam sine 65, 105, 104 VIE CLOG) STIS epic t orca Cie neeree hicle se Siete eis ute sleictasieanclomteee Sues eeeeeneee 82 Mitlankovatchicy, Cledanseree rel cei ela mnatciere shir sere clasiaeeeen eee 93 LG OT GIT tape pocarrenosansanccesadacuseeeads 244, 245, 247, 249, 250 MADAME a ANALY SIS oo cstejas2 ea esate statone tate eteateTeneratotelclats wlat sya elerstolelaraamrsragynateiee 70-75 fauve} Moyel jal tee) Goaneanaenaaasenenaanpaaso seer scorn ecanoeonarcanodeeinc (3375 WA ONOCOLP GLE Sire teretotae cere 2 Ss Sass SS eI Sees sooo ero aes eas 131 VIOUS Sectrcec a Naon ites sis oie eeiae aes teint ete are 107, 116, 118, 127, 130 MUGS LONE ys olor os ciciereie seine ies saosin wieretaie ainisiete ala cloreraterehe sare 123, 130, 131 Muhlenbergia(Muhly/erass) ie s.tsca- cree eeseasseeeseeecee 76, 106 WAV IGA WAXY TUE) Waser tite ce seeecmareiaesinee ee tts 83, 88, 106 AVM ALE) » corigongbee cdSenOn nea COUSCa Aaa cMOnSER Tete ame ce bamretionaen conte 118 Myrtaceae we renner eicistcacscteclnerisece seco 83, 107, 116, 129 INE COG Gan ico Ua aas a Cocnat CoRR DE ene an: Aarrnar eee nas wane Heterinctas 82 IN AG Die esssecetcratctscsiotetavstevc mafia slo eletevsianatafarensete ciattictote(sicvaseteo)avele Rtcls ninleelars Stn Relste ae 82 IN AVEC chore osayctsitahara'aiors -Telosnrsectsaiaseeerereteleetee idlstereleroetes 77, 78, 79, 80, 81 INGA LT ue Renan s cao DD REECE OOBREEE Cac Cote aoe Cae ESOC USGOSOeTEE ace core 77, 78 PN COCOAUAUES Myer Te Se OTN ASP a a = biota ae ole elo cia Be olan shee OOE 5}, (9) MONS a aie oy otay aro stetaleainratorelstescioteseiaereciae Gio clelots Bele wns veisramtewieterneis W335 IE) MRT ENO SEMA apes oll atte ulate lat ctayatstst aj ctaleieersiale sa stcelafsse(olercieinlacicialeeereite 70, 82 UNEES CRG ee te rate Seite aercictoeieineoeeseisias one EER 78, 79, 80, 81, 151-159 Wodobaculartellancarcncsecmncccoen eer ceten eee een eneen aeenlee 245 INOdosarlidae s2iiscesi setae acters crate ste er olocis sioiste Date ste diclateclotwe wisi taheaeer 245 INonionellar cession ts see ee seas eee co ee ower eens 245, 250 INOMLISEEUL ee foe cee ie ee ca cei seceve nt once cae seae ecole 242 North Biscayne Bay 250 Nubecularia 245 INU DIO raetraacn nae tenes cok che mot eece eee 129 INymphacede) ae as-cidseteeteseinv me cencessemerace 77, 83, 84, 85, 86, 100 Nymphaea (water lily) .... 61, 83, 85, 86, 87, 106, 116, 117, 118, 119, 120, 122, 124, 126, 130 INDSSQ) Race ceposeasene eecprnsnke@acosteneadscene tees 107, 116, 118, 128 AKG. aise crsiotcmphisicce merece CeLenec Celie Misc oe pase CEReE Cocca eee eee Re 83 Oligohalines 3. cssicieistatmrorcmiaseiienciesiiesiis sins cateiorerese tees emacieeeeeee 679) OEE PI areas sada e fois aro stass resets tuce(epete lee wo so as e)ahaisyaia wlels oevsiosstersterorereerers 87 Osmunda ........ 83, 107, 116, 117, 118, 121, 123, 124, 129, 131 OSTACOGES SH ato meinieidisisiet ico eaiele seizes ee Meee cela ccs cee cee eee 4 Ovoidites ....... 107, 116, 117, 118, 119, 120, 123, 124, 128, 131 ORY UTOLIG sae sas Rass ser cise ee ies ones en ate aat sare 88, 89, 90 LOMAS MIEN ACO) (oe Saactencrmascoperasecnd imap aadecodtenenos bocacactocaaor 2, paleoecology =-...c-nee-- Palmae. a. ste: seemaeeese ee Panicum (maidencane) PAF QUIOy hi tanec eee EALCULING. merin.cisa se ocaee ceclaec tt eset cet ee by dating wroncn-nomsc cise actce oes eeneeee meee needa eee eee peat 2. 5951625163; 64516551695, 70; 76; 717,983, 85,1075 Sono los 3 94, 95 TEC HOT ATT heoeetoner teitacan ee erieccr noua iaccsccce dascoAnadsocus TS Ths} ReelDee Belemmite aa ccaeett cn rascme cee et ee tence eee ech e eee eee ere 4 IRENCTOPOLISS sercmcctes soe - acetic oe eee see LD RE ILA DO 2D. PET atOGy ther ided. 2o icteric cia aetasisee sila ease eer eee see 4, 5, 7-10 Persea) (Ted Day)