GULF RESEARCH REPORTS Vol. 9 No. 1 January 1994 ISSN: 0072-9027 Published by the f GULF COAST RESEARCH LABORATORY I Ocean Sprinas, Mississippi Gulf Research Reports Volume 9 | Issue 1 January 1994 Historic Trends in the Secchi Disk Transparency of Lake Pontchartrain J.C. Francis University of New Orleans M.A. Poirrier University of New Orleans D.E. Barbe University of New Orleans VWijesundera University of New Orleans M.M. Mulino Steimle and Associates, Inc. DOI: 10.18785/grr.0901.01 Follow this and additional works at: http:/ / aquila.usm.edu/ gcr Part of the Marine Biology Commons Recommended Citation Francis,}.; M. Poirrier, D. Barbe, V. Wijesundera and M. Mulino. 1994. Historic Trends in the Secchi Disk Transparency of Lake Pontchartrain. GulfResearch Reports 9 (l): 1-16. Retrieved from http:// aquila.usm.edu/gcr/vol9/issl / 1 This Article is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf and Caribbean Research by an authorized editor ofThe Aquila Digital Community. For more information, please contact Joshua.Cromwell^usm.edu. Gnif Research Reports, Vol. 9, No. 1, 1-16, 1994 Manuscript received March 3, 1993; accepted September L3, 1993 HISTORIC TRENDS IN THE SECCHI DISK TRANSPARENCY OF LAKE PONTCHARTRAIN J.C. FRANCIS', M.A.P01RRIER‘,D.E.BARB^:^V.WUESUNDERA^ AND M.M. MULINO’ ^Department ofDiotogicat Sciences, University of New Orleans, New Orleans, Louisiana 70148 ^Department of Civil Engineering, University of New Orleans, New Orleans, Louisiana 70148 ^Ste 'unle and Associates, Inc., Metairie, Louisiana 70004 ABSDiACT A major cnvironmenlal concern nboul Lakc Ponlchartrain is an assumed iong-icrm increase rn turbidity based on Secchi disk transparency obscrvalions. Regression of the available data on Sccchi disk, transparency versus lime (1953 through 1990) reveals a slatislically significanldecreascin transparency of about -40%. However, the data set is biased In that it does not adequately represent the seasonal effects of salinity and wind speed. Two analytical procedures were undertaken to determine the extent to which the apparent long-term decrease in transparency was dependent on the seasonal bias. One procedure involved sca.SQnal adjustment of the data for the effects of salinity and wind speed. The otlier procedure was to remove the seasonal bias by consirucling unbiased data sets. Seasonal adjustment for the effects of salinity and wind speed reduced the level of significance for the relationship between Sccchi disk transparency and lime from about 1% to about 10%. This result indicates that some of the apparent decrease in transparency in the original data is the result of inadequate representation of seasonal effects in the biased data set. In most years data are not available for all months with the result that the seasonal effects of salinity and wind speed are not adequately represented. When the bias was removed by constructing unbiased data sets, the data no longer supported the conclusion of a statistically significant change in Sccchi disk transparency from 1953 to 1990; p>0.5. IlSTRODUCnON Lake Ponichartrain is an einbaymenl in a large estua- rine system in southeastern Louisiana. Il has a mean salinity of 4 ppL a mean depth of 3.7 m, and a surface area of 1630 Saline water enters from adjacent estuaries through tidal passes. Fresh water sources are streams. New Orleans area outfall canals, and the Mississippi River during open- ing and leakage of the Bonnet Carrd Spillway (Barb6 and Povrricr, 1991). Over one million people live on the southern sliore of Lake Pontchar train. With increasing urbanization of the New Orleans area over the last century, concerns have arisen as to possible declines in water quality, fisheries, recreational use and commercial valueof theesiuary (Houck et aL, 1987). Increased lurbidiiy, for example, is regarded as an environmental problem in Lake Ponichartrain. Sup- port for iJiai concern is provided by Stone ei al. ( 1 980) who plotted four sets of selected Secchi disc transparency data from Lake Pontchartrain and concluded that water clarity had decreased by almost 50% between 1953 and 1978, Although Stone's report (Stone ei al., 1980) is often cited as indicating a major environmental change in Lake Pontchartrain, il did not mclude all available data or address die seasonal effects of wind and salinity on transparency values. Thompson and Fitzhugh (1985) found a relation- sliip between sal inity and lake clari ly w iih Lake Pontchartrain being clearer during periods of higher salinity and more turbid during fresher periods. Swenson ( 1980), found that winds blowing over Lake Poniciiamain are sufficient lo stir and mix bottom sediments ihrou ghoul the water column about 15% of the time. Thompson and Verret (1980) reported that occasional high winds during frontal passages, and at other limes, are capable of resuspending bottom sediments, especially in the winter. Dow and Turner (1980) also slated that turbid conditions may be caused by weather fronts and their wind systems. Storm-water runoff from the New Orleans area is currently discharged into Lake Pontchartrain without any treatment. Although the potential contribution of urban runoff lo the pollution of estuaries has been recognized for some time, few studies have actually documented specific adverse effects (Odum and Hawley, 1987). On an annual basis, pollution from urban runoff can contribute more suspended solids and plant nuirienis than any other pollu- tion source (Scheaffer et al., 1982). Urban runoff could 1 2 Franqs ft al. affect the Secchi disc transparency of Lake Ponichartrain Uirough the introduction of plant nulrienis which increase phytoplankton growth and by the introduction of suspended solids (Mancini and Plummer. 1987; Odum and Hawley, 1987). It is cunentJy assumed that the turbidity of Lake Ponichartrain has increased by almost 50% between 1953 and 1978 (Slone et al., 1980) due to the activities of man. Our study includes recent data, investigates the effects of salinity, wind and seasonal differences on transparency and tests long-tenn trends for statistical significance. The study was designed to provide a better understanding of trends and how natural factors affect water clarity. ResulLs of this study will provide realistic goals for the treatment of urban runoff in plans to restore Lake Ponichartrain. Materials and Methods Description of the Database The Secchi disc is widely used to estimate the depth of light penetration in aquatic habitats (Tyler. 1968). All data used in this study were obtained with a 20 cm disc with black and white quadrants. The raw data used in this study consisted of observations of Secchi disk transparency and salinity recorded by several investigators during the periods shown in Table L This data set contains Secchi disk transparency and salinity data from July 1953 through December 1990. In some years, data are not available for several months. For most months, data were only collected once amonth. Data collected by the Louisiana Department of Environmental Quality from 1985 through 1990 were recorded from the Causeway Bridge, which is about 20 feel above the water surface. Therefore, their transparency values may be lower because of the greater distance be- tween the observer and the water surface. In summary, the data set is incomplete: • It does not contain data for all years. • It does not contain data for all months. • It may not be representative of particular months because data were collected only once or twice a month, • U is not consistent witli regard to station location. Wind data used in this study were taken at New Orleans Intemadonal Airport bom 1953 through 1990 and published in Local Climatic Data by the National Weather Service Meteoro- logical Observation Office. The elevations at which the wind data were measured were not the same in all years. The data from January, 1953 to July, 1969 were taken at an elevation of 3 feet abovelhe ground, and iheoihcrs at aneievalion of 4 feet. TABLE 1 Sources of Secchi disk transparency and saKnity data. Investigators Period N* Sullkus el al. (1954) 8/19/53 - 6/30/54 155 Stern and Stem (1969) 6/2/69 - 7/22/69 71 Dugas and Tarver (1973) 3/18/70 - 5/18/71 109 Tarver and Savoie (1976) 9/26/72 - 8/22/74 279 Poirrier et a/. (1975) 7/17/73 - 11/1/73 73 Stone et al. (1980) 1/78 - 12/78 219 0‘Hara and Capello (1988); Louisiana Department of Environmental Quality (LADEQ) (unpublished 3/31/82 - 1 1/29/82 456 1/4/83 - 12/7/84 816 daut) 7/8/85 - 8/14/90 311 Steiinle and Associates (1985) Western lake 1/12/84 - 10/25/84 168 Eastern lake 2/16/84 - 11/1/84 149 * Number of observations Secchi Disk Transparency 3 The salinity data sei, STORET, obtained from the U.S . Army Corps of Engineers contains data from 1953 through 1980, and from 1986 through 1989. These data were only used in analysis of variance to determine the statistical significance of armual seasonality in salinity. Statistical Methods All criteria were met for application of parametric staiis- Ucal methods. Simple and multiple regression analyses and the analyses of variance were performed according lo standard procedures as described in Sokal and R ohlf (1981). Results Annual means, standard deviations, standard errors, and coefficients of variation of Secchi disk transparency were calculated for each year in which Secchi disk transpar- ency data were available and are presented in Table 2. The highest valuesof Secchi disk transparency occurred in 1953 and 1954 (Table 2). The lowest Secchi disk transparencies occurredfrom 1973 through 1983. This period was affected by Bonnet Carrd spillway openings in 1973, 1 975, 1 979 and 1983. The greatest relative dispersion (coefficient of variation) was recorded in 1974 and 1978 during iheperiod TABLE 2 Statistics for annual Secchi disk transparency calculated from the original data set. Secchi disk transparency (cm) Year N* Mean High Low SD* SE* CV* 1953 62 131.69 431 30 76.36 9.70 59.4 1954 93 133,00 366 30 84.57 8.76 63.2 1969 71 89.31 183 15 39.51 4.69 44.2 1970 72 144.15 304.8 45.72 66.57 7.85 46.2 1971 37 140.87 182.9 91.44 23.88 3.93 17.0 1972 44 1 14.60 274 15.2 52.40 7.90 45.7 1973 208 79.29 274.3 9.1 41.59 2.88 52.4 1974 100 63.70 243.8 9.1 54.20 5.42 85.1 1978 219 60.60 165 1.5 37.42 2.53 61.7 1982 456 100.71 236.22 30.48 36.36 1.70 36.1 1983 685 55.79 182.88 2.54 30.54 1.17 54.7 1984 448 70.35 347.98 5.08 39.64 1.87 56.3 1985 35 106.80 213.4 14 47.70 8.06 44.7 1986 60 109.50 302.3 30.5 53.10 6.86 48.5 1987 59 68.00 142.24 25 26.00 3.38 38.2 1988 59 79.65 203.2 15.24 40.88 5.32 51.3 1989 59 102.00 182.88 30.48 34.00 4.43 33.3 1990 58 85.57 152.4 30.48 34.81 4.57 40.7 N = Number of Observations SD = Standard Deviation SE = Standard Error CV = Coefficient of Variation 4 Franqs et al. of spillway openings, allhough 1953 and 1954 also realized high relative dispersion. The lowest relative dispersion was recorded 1971. Average annual Secchi disk transparency is plotted as a function time m Figure 1 . The period of time represented in the graph is 38 years: 1953 through 1990. Specific years are indicated above each point in the graph. Linear regression analysis was performed on annual means. The slope of the regression line, -1.47 cm/year, is siaiislically significant; 0.01 < p < 0.02. The regression line indicates an apparent decrease in Secchi disk transparency from about 130 cm in 1953 and 1954 to about 80 cm in 1990 - an apparent decrease of about 40%. The data set is biased in that it docs not adequately represent the seasonal effects of salinity and wind speed, two variables dial have significant effects on Secchi disk transparency. Figure 2 shows the annual seasonality in salinity. It is a graph of average monthly salinity versus months of the year. The highest saliniiies occur in the fall (September, October and November) and the lowest salinities occur in the spring (April , May and June), Monthly means are based on 32 years of data from the STORET data base (U.S . Army Corps of Engineers). Thai data base was used to lest the validity of the apparent seasonality in salinity with analysis of variance. The ANOVA table for two-way analysis of variance without replication is pre.scnied in Table 3. The variance ratio, 21.18, exceeds the critical value for the test, 1.8, indicating that hi^y significant differences exist among monthly mean salinities, producing a highly signifi- cant annual seasonality in salinity. Figure 3 shows the annual seasonality in wind speed. It is a graph of average monthly wind speed versus months of the year. The highest wind .speeds occur in February and March and the lowest wind speeds occur in July and August. Monthly means are based on 38 years of data from the National Weather Service. That data base was used to test the validity of the apparent seasonality in wind speed with analysis of variance. The ANOVA table for two-way analysis of variance wiilioul replication is presented in Table 4. The variance ratio, 10X42, exceeds the critical value for the lest, 1.8, indicating that highly significant TIME (years) Figure 1. Annual mean Secchi disk transparency of Lake Ponlcharlrain from 1953 through 1990. SALINITY (ppL) Secchi Disk Transparency 5 TIME (months) Figure 2. Monthly mean salinity. TABLE 3 Analysis of variance of monthly mean salinity. Source SS df MS F* Month 333.77 11 30.34 21.28 Year 711.25 31 22.94 Error 484.79 340 1.43 Total 1529.81 38 F(0.95) = 1.8 WIND SPEED 6 Franqs et al. TIME (months) Figure 3. Moothly mean wind speed. TABLE 4 Analysis of variance of monthly mean wind speed. Source SS df MS F* Monih 825.50 11 75.05 103.42 Year 240.54 37 6.50 Error 295.34 407 0.73 Total 1361.38 455 F(0.95) = 1.8 Secchi Disk Transparency 7 SALINITY (ppt) Figure 4. Secchi disk transparency (individual points) versus salinity. differences exist among monthly mean wind speeds, pro- ducing ahighly significant annual seasonality in wind speed. Seasonal adjustment of the Secchi disk transparency data for salinity and wind speed was conducted in an effort to compensate for the seasonal bias in the data set. The adjustment for salinity is presented first. Secchi disk transparency is plotted as a function of salinity in Figure 4. siinity ilaare from the original data set. (Transparency values above 160 cm and salinity values above 10 ppt are not included in the graph.) Linear regression analysis was performed on individual points. The slope of the regression line, 8.13 cm/ppi salinity, is statistically significant; 0.01 < p < 0.02. Figure 5 is a graph of average annual Secchi disk transparency plotted as a function of salinity. Figure 6 is a graph of salinity versus lime the 38-year period 1953 through 1990. Salinity data are from the original data set. Although there is considerable year-to- year variation in salinity, there has been no long-term change in salinity. The slope of the linearregression line, -0.02 cm/year, is not statistically significant. The long- term average salinity, 3.9 ppt, was used as a base for seasonally adjusting the data for salinity. There are two equivalent ways to seasonally adjust the Secchi disk transparency data. One way is to adjust annual means where annual mean Secchi disk visibilities and amiual mean salinities are used in the calculation to provide adjusted annual mean Secchi disk visibilities. An equivalent procedure is to adjust individual points where individual Secchi disk transparency observations and associated salinities are used in (he calculation; adjusted annual mean Secchi disk visibilities arc then calculated from (he adjusted points. Indiv idual points are adjusted in the foUowmg example: The adjustment procedure employed the regression equation presented in Figure 5 of Secchi disk transpar- 8 Franqs et al. SALINITY (ppt) Figure 5. Annual mean Secchi disk transparency as a function of salinity. ency versus salinity: Y = 63.82 + 8.13X. Two values of Secchi transparency were calculated for each point: (1) Secchi disk transparency using the long-ienn average salin- ity, 3.9 ppl; (2) Secchi disk transparency using the salinity associated with the specific point. The difference between those two values was the adjustment factor for that point. The adjustment factor was subtracted from Secchi disk transparency for that point. This operation adjusts the data to the long-term average salinity. RguieT isa graph of annual mean Secchi disk transparency adjusted for salinity versus time. Comparison with Figure 1 reveals thal very little change in slope has occurred -- 1.47 cin/year to - 1 .34 cm/year. The relationship between Secchi disk transparency and time is still significant al the 5% level, indicating that on average the Secchi disk transpar- ency values in the original data set are not associated with unusually high or low salinities because of unequal rcpie- seniation of the seasonal effects of salinity in the data set. Figure 8 is a graph of Secchi disk transparency versus wind speed. The graph includes Secchi disk transparency points in the original data set. (Transparency values above 160 cm are not included in the graph.) Wind speed is the five-day average of mean wind speed. Data are from the National Weather Service data set. Linear regression was performed on individual points. The slope of the regres- sion line, -4,36 cm/mph, is siatisiicalJy significant; p < 0 . 01 . Figure 9 is a graph of average annual wind speed versus lime - the 38-year period from 1953 through 1990. Al- though there is considerable year-to-year variation in wind speed, there has not been a long-ienn ehange in wind speed. Regression analysis was performed on annual means. The slope of the linear regression line, -0.02 mph/year, is not statistically significant. The long-term average wind speed, 8.13 mph, was used as a base for seasonally adjusting the data for wind. Secchi Disk Transparency 9 Figure 6. Annual mean salinity of Lake Pontchartrain from 1953 through 1990. The adjustment procedure was the same as that de- scribed above for sahniiy. It employed the regression equation presented in Figure 7 of Secchi disk transparency versus wind speed: Y = 121.43 - 4.36X. Figure 10 is a graph of Secchi disk transparency adjusted for wind speed versus lime. Comparison with Figure 1 reveals that significant change in slope has oc- curred — L47 cm^ear to -1.06 cm/year. The relationship between Secchi disk transparency and time is no longer signiricaniaiihe5%levek0.050.5 Secchi Disk Transparency 11 selected because in 1953 Secchi disk transparency readings were available only from August through December. It is not surprising that Secchi disk transparency was high in 1953 whffli one considers that salinity is highest in October and November (contributing lo high transparency values), and that wind speed is lowest in August and September (also contributing to high transparency values). Other years have even higher average Secchi disk transparency values for the August through December period. Annual means in Table 5 were calculated by taking the average of monthly means ralher than an average of all data points. Regression of annual Secchi disk transparency versus time produced the following equation: Y = 120.05 - 0.64X. The slope, -0.64 cm/year, is not statistically significant, p > 0 . 5 . On the basis of this analysis, it is concluded that there has been no change in Secchi transparency over the 38-year period from 1953 through 1990, Example 2. Table 6coniauis Secchi disk traasparency values for those years in which conimuous data was avail- able from January through June. This period was selected because in 1954 Secchi disk transparency observations were available only from January through June. The seasonal bias in the original data set was removed by constructing a data set consisting only of years in which Secchi disk transparency observations were recorded from January through June. Annual means in Table 6 were calculated by taking the average of monthly means rather than an average of all data points. Regression of annual Secchi disk transparency versus time produced the follow- ing linear regression equation: Y = 75.13 -0.49X. The slope, -0.49 cm/year, was not statistically significant, p > 0,4. On the basis of this analysis, it is concluded that there has been no change in Sccchi disk transparency over the 37-year period from 1954 through 1990. Example 3. The original Secchi disk transparency data set, obtained by combining data from the soiirce.s indicated in Table 1, is incomplete. Data arc missing for several months in most years. Table 7 includes all years for which there is at least some Secchi disk transparency data. Secchi disk transparency was estimated for those months in which data are noravailable - the so-callcd missing months in the dataset. Missing data points were estimated with the multiple regression equation, Y = 97.83 + 8.03 X I - 5. 15 X2. and the appropriate monthly average wind speed and monthly average sahnlty. After estimating values for missing months, annual inccUis for Secchi disk transparency were calculated for 1953 through 1990. Regression of annual TABLE 6 Secchi disk transparency for years in which data are available - January through June, Year Time (yr) Transparency (cm) 1954 2 97.46 1973 21 57.44 1974 22 4755 1978 26 38.04 1983 31 29.95 1984 32 47.97 1986 34 80.65 1987 35 57.49 1988 36 65.28 1989 37 87.27 1990 38 64.58 Regression transparency vs. lime; Y = 75.13 - 0.49X P>0.4 TABLE 7 Secchi disk transparency with estimated values in missing months. Year Time (yr) Transparency (cm) 1953 1 94.89 1954 2 89.80 1969 17 87.13 1970 18 122.57 1971 19 101.54 1972 20 92.80 1973 21 75.37 1974 22 75.14 1978 26 59.12 1982 30 94.84 1983 31 43.86 1984 32 67.32 1985 33 91.71 1986 34 109.45 1987 35 67.48 1988 36 79.93 1989 37 102.23 1990 38 80.97 Regression transparency vs, lime: Y = 95.52 - 0.42X P>0.5 12 Francis et al. WIND SPEED (mph) Figure 8. Seech i disk transparencji (individual points) versus wind speed. Secchi disk transparency versus time produced the follow- LRg linear regression equation; Y = 95.52 - 0.42X. The slope, -0.42 ciWycar, is not statistically significant, p > 0.5 . On the basis of this analysis, it is concluded that there has been no change in Secchi transparency over the 38-year period from 1953 through 1990, In summary, the historic data set on Secchi disk transparency in Lake Pontchartnun is biased 'm that it does not adequately represent the seasonal effects of salinity and wind speed. When the seasonal bias is removed from the data, it no longer supports the conclusion of a long-term decrease in Secchi disk transparency. Discussion Regression of the origmal data on Secchi disk transpar- ency versus lime (1953 through 1990) reveals a statistically significant decrease in transparency with dme. The regres- sion line suggests a decrease in transparency of about 40%. However, the original data set is biased in that it does not adequately represent the seasonal effects of salinity and wind speed. Tlte data set was subjected to two analytical procedures to determine the extern to which the apparent long-tenn decrease in Secchi disk transparency was depen- dent on the seasonal bias . One procedure involved seasonal adjustment of the data for tlie effects of salinity and wind sp^. Tlie olherprtKcdure was to remove the seasonal bias by constructing unbiased data sets. Secchi Disk Transparency 13 10.4 10.2 10.0 9.8 9.6 9.4 PL. ^ 9-2 9.0 P W 8.8 H a, 8.6 m 8.4 Q ^ 8.2 ^ 8.0 7.8 7.6 7.4 7.2 7.0 TIME (years) Figure 9. Annual mean wind speed for I.^ke Pontchartrain area from 1953 through 1990. Regres.sion analysis revealed a statistically significant, positive relationship between Secchi disk transparency and salinity, and a siaiisiically sig nificani. negative relationship between Secchi disk transparency and wind speed. Further analysis indicated that neither average annual salinity nor average annual wind speed had changed significanUy from 1953 through 1990. Secchi disk transparency dam were seasonally adjusted for the effects of salinity aiKl wind speed. The base for adjustment in each case was the long-term average of the variable for which adjustment was being made. Regression of Secchi disk transparency (adjusted for salinity) versus time revealed a statistically significant relationship, indi- cating that the adjustment procedure had not influenced the statistical significance of the long-term relationship be- tween Secchi disk transparency and time. This result indicates that on average the Secchi disk transparency values in the original data set are not associated with unusually high or low salinities because of unequal repre- sentation of the seasonal effects of salinity in the biased data set. Regression of Sccchi disk transparency (adjusted for w md speed) versus lime indicated that there was no longer a statistically signincant relationship between Secchi disk transparency and time; 0.05 < p < O.IO. Adjust'mg the data for the effect of wind speed had reduced the level of significance for the relationship from about 1% to about 10%. This result indicates that some Secchi disk transpar- ency values in the original data set are associated with unusually high or low wind speeds because of the unequal representation of the seasonal effects of wind speed in the biased data set. Multiple regression of Secchi disk transparency (ad- justed for both salinity and wind speed) versus time also 14 Francis et al. Figure 10. Annual mean Secchidlsk transparency from 1953 through 1990 adjusted for wind speed. indicated that there was no longer a siaiistically significant relationship between Secchi disk transparency and time; 0.05 < p < 0. 10. Seasonal adjustment had reduced the level of significance to about 10%. One can. therefore, con- clude that some of the apparent decrease in Secchi disk transparency in the original data is the result of unusually high and low salinities and wind speeds realized because of unequal representation of the seasonal effects of salinity and wind speed in the biased data set. Another analytical procedure undertaken with the original data set was to remove the seasonal bias by consuucting unbiased data sets. In most of the years represented in the data set, data are not available for all 12 months of the year, especially before 1983. Only in the late 1 980s arc daia consistently available for all 1 2 months of the year. Analysis of variance of monthly salinity data from 1953 through 1980, and 1986 through 1989 (32 years) revealed a statistically significant annual seasonality, with the highest values occurring in November and the lowest values occurring in May. Similarly, analysis of variance of monthly wind speed data from 1953 through 1990 (38 years) revealed a statistically significant annual seasonality, with the highest values occurring in February and the lowest values occurring in August. These seasonal effects arc not adequately represented in the available data on Secchi disk transparency in Lake Pontchartrain. The seasonal bias was removed from the data by constructing unbiased data sets in three ways: (1) The derived data set contained Secchi disk transparency values for those years in which continuous data were available from August through December; (2) The derived data set contained SEccm Disk Transparency 15 Figure 11. Anoual mean Secchi disk transparency from 1953 through 1990 adjusted for salinity and wind speed. Secchi disk transparency values for those years in which continuous data were available from January through June; (3) The derived data set contained all of the original data on Secchi disk transparency in addition to estimated values for those months in which data was not available. In each case, when the seasonal bias was removed from the original data, it no longer supported the conclusion of a statistically significant change in Secchi disk transpar- ency from 1953 to 1990; p > 0.4. Results of this study do not support the long-term increase in turbidity of almost 50% reported by Stone ( 1 980). Although urban runoff is known to produce short- term increases in water turbidity near outfall canals (Stem and Stem, 1969), data examined in this study do not indicate a long-ienn, lake-wide increase. Acknowledgments This project was funded by the University of New Orleans Urban Waste Management and Research Center under project number 92-B-003, Unpublished data used in this study were provided by the Louisiana Department of Environmcnial Quality and the U.S. Army Corps of Engineers. 16 Francis et al. LriERATURE CriED Barbc D.E. and M. A. Poirricr. 1991. Unique Water Quality Aspects of Lake Pomchartrain, ln\ J, L. Anderson (ed,), Water Re- sources Planning and Management and Urban Water Re- sources. I’roccedings of the 18lh Annual Conference and Symposium, Water Resources Planning and Managcmcnl Division of the American Society of Civil Engineers, New Orleans. Louisiana, May 20-22, 1991. pp. 187-191. Dow. D.D. and R.E. Turner. 1980. Structure and function of the phytoplankton community in Lake Pontchartrain, Louisi- ana. In: J. H. Stone (ed.), Environmental Analysis of Lake Pontchartrain, Louisiana, It’s Surrounding Wetlands and Selected Land Uses. Vol. 1. Prepared for the U, S. 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Physical, chemical, bacterial and plankton dynamics of Lake Pontchartrain, Louisiana. Technical Report No. 4, Louisiana Water Resources Re- search Institute, pp. 3-4 and 12-18. Stone, J.H. (ed.). 1980. Environmental Attalysis of Lake Pontchartrain, Louisiana, Its Surrounding Wet-Lands, and Selected Land Uses, Volumes 1 & 2. Louisiana State University Center for Wetland Resources, Baton Rouge, LA. Prepared for the U. S. Army Engineering District, New Orleans. Contract No. DACW -29- 77-C-0253. 1219 pp. Sutikus, R.D., R.M. Darnell and J.H. Darnell. 1954. Biological study of Lake Pontchartrain. Annual report for the year, July I, 1953 to June 30, 1954. Tulanc University, Zoology Department, New Oilcans, Louisiana, pp. 36-44. Swenson, E.M. 1980. General hydrography of the tidal passes of Lake Pontchartrain. In: J. H. Stone (ed.), Environmental Analysis of Lake Pontchartrain, Louisiana, It' sSurrounding Wetlands and Selected Land U ses. Vol. 1 . Prepared for the U. S. Army Engineering District, New Orleans, Contract NO.DACW-29-77-C-0253. pp. 57-156, Tarver, J.W. and J.B. Savoie. 1976. An inventory and study of the Lake Pontchartrain - Lake Maurepas estuarine complex. Phase I, n, HI - hydrology and water chemistry. Technical Bulletin No. 19, Louisiana Wildlife and Fisheries Commis- sion, Baton Rouge, Louisiana. Thompson, B.A. and G.R. Filzhugh. 1985. Synthesis and analysis of Lake Pontchartrain environments, influencing factors and trends. Center for Wetland Rc.sources, Louisiana Stale University, Baton Rouge, Louisiana. Thompson, B.A. and J.S. Vcirct. 1980. Nekton of Lake Pontchartrain, Louisiana, and its surrounding wetlands. In: J. H. Stone, (ed.), Environmental Analysis of Lake Pontchartrain, Louisiana, Us Surrounding Wetlands and Selected Land Uses. Vol. 2. Prepared for the U. S. Army Engineering District, New Orleans. Contract No. DACW- 29-77-C-0253. pp. 711-825, Tyler, J.E. 1968. The Sccchi Disc. Limnology and Oceanogra- phy 13(1):1-12. Gulf Research Reports Volume 9 | Issue 1 January 1994 Namalycastis abiuma (Muller in Grube) 1 87 1, an Aberrant Nereidid Polychaete of a Georgia Salt Marsh Area and its Faunal Associations Erik Rasmussen University of Copenhagen DOI: 10.18785/grr.0901.02 Follow this and additional works at: http:/ / aquila.usm.edu/ gcr Part of the Marine Biology Commons Recommended Citation Rasmussen, E. 1994. Namalycastis ahiuma (Muller in Grube) 1871, an Aberrant Nereidid Polychaete of a Georgia Salt Marsh Area and its Faunal Associations. Gulf Research Reports 9 (l): 17-28. Retrieved from http:// aquila.usm.edu/gcr/vol9/iss 1/2 This Article is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf and Caribbean Research by an authorized editor ofThe Aquila Digital Community. For more information, please contact Joshua.Cromwell^usm.edu. Gulf Research Reports, Vol. 9. No. 1, 17-28, 1994 Manuscript leceived December 16, 1991; accepted October 18. 1993 NAMALYCASTIS ABIUMA (MULLER IN GRUBE) 1871, AN ABERRANT NEREIDID POLYCHAETE OF A GEORGIA SALT MARSH AREA AND ITS FAUNAL ASSOCIATIONS ERIK RASMUSSEN Zoological Museum, University of Copenhagen. UniversUetsparken 15. DK-2100 Copenhagen, Denmark ABSTRACT The moiphology of the aberrant ncreidid Namalycastis abiuma, Namanereidinae U described on the basis of material collected 1 971-72 and 1976 in the brackish water drainage ditch system of Sapelo Island, Georgia, USA, The syslcmatics of the species is briefly reviewed. The habitat and ecological conditions under which the species lives in these brackish ditches are described. At various times, M abiuma lives out of water under the bark of trunks and branches of fallen trees. Decaying wood is ingested. It is suggested that future studies should concentrate on the reproductive biology of the widely- spread, mainly tropical populations of what may prove to be not one, but several species of Namalycastis. A list of the invertebrate fauna associated with N. abiuma is included with notes on these associates. iNTRODUCnCW Namalycastis abiuma (Namanereinae, Nereidae) was described by Muller in Grube, 1 87 1 as Paranereis abiuma. Eleven closcly-relaied species subsequently wcjnc described under the generic name Lycasiis. These species occur in ftesh water lo brackish or almost fully marine habitats (Wesenberg-Lund, 1958). All species were referred to by the new generic name Namalycastis by Hartman (1959), with the comment that all “are believed to refer either to a single species resembling the type, or to closely related, and generically identical forms*' (p. 163). Hartman's diagnosis, based on material from Florida, has been generally ac- cepted (Foster, 1972; Gardiner, 1976; Gardiner and Wilson, 1977; Heard, 1975, 1982). Heard (1982) ^onymized Lycastopsis Rioja, 1946,L.ponr/caJakubova, 1930, ami L. hummel incki Augener, 1933, all from North Carolina, Georgia, Florida and Louisiana with N, abiuma, N. abiuma was reported from Australia by Russell (1962) and N. cf. abiuma by Hutchings and Glasby (1985), Al- though it may seem difficult lo accept that Hartman rightly synonymized 1 1 species of Abiuma^ considering the diver- sity of their habitats, it must be noted that only a limited number of systematic characteristics are available, e.g., a pharynx without paragnaihs or papillae, reduced paiapodia, elc. Therefore, until a more thorough revision of the many forms is available, it seems reasonable to accept Hartman's inclusion of them as members of Abiuma. In this paper, the systematicsofN. ab/amn were briefly reviewed and some morphological details were described based on material from brackish water in Georgia. An attempt has been made to characterize ecological condi- tions under which the species occurred, its mode of life, and its faunal associates. Materials and Methods Site Description The study area encompassed shallow drainage ditches on Sapelo Island connected to the sea only during periods of extreme high water, A scries of ditches, dwindling into pools at low water with different salinity conditions, were chosen for sampling. Populations of M abiuma were found at only two of 10 stations surveyed: Station 1, the main station regularly examined during 1971-72, and Station 10, a supplementary station visited only a few times in 1976 (Figure 1). Station I (Figure 2), situated one mile north of the Settlement, was a roadside ditch about 4 m wide and varying in depth from a few cm during dry periods to more than 0.5 m at spring tides. The bottom layer was soft, fine, blackish mud with some smell of hydrogen sulphide . Fallen tree trunks and decaying branches from the siuiounding pine forest were piled up in part of the ditch system. Rickards (1968) gave a short description of this study area. Except fora smallpatch ofRuppia maritima L., present only in 1976, the ditches had no submerged vascular plants. The surface of the mud was covered with adense brownish layer of diatoms during periods with clear direct sunshine. Tufts of perennial glasswon (Salicornia virginiana L.) 17 18 Rasmussen Figure 1. Sapelo Island, Georgia, with tidal creeks, ditches and pools. Numbers indicate sampling stations. were found on the bank of the ditch near the saltgrass cover {Spartina altern ijlora Lois.) occurred in some places along {Disdchlis spicata (L.) Greene). Low bushes of marsh elder the bank edges and often extended across the ditch to form (Iva frutescens L.) fonned a transitional border near the thresholds that often impeded the upstream flow of sea forest in the Disdchlis marsh clearings. Saltmaish grass water. Aberkant Nereidid Polychaete of Gh)rgia Salt Marsh 19 Figure 2. Pholograph showing part of Station 1, a roadside ditch with Spartina grass along the banks (to the right, opposite the ro^). Behind the DistUhtis grass cover bushes of marsh elder {Iva frutescens) are bordering the pine tree forest in the background (April 23, 1971). Station 10 was a ditch located between steep bluffs which ran parallel to (he road between the King Savannah clearing and the Bell Maish near the High Point road. It was surrounded by dense forest. The steep banks of the ditch reached 2 m above the bottom. The bottom sediment was virtually clean sand with plant remnants and scattered Spartina. The banks were topped with a dense growth of marsh elder. The ditch was nearly dry during sampling periods. Direct access to sea water gave this di ich a regular tidal cycle. Salinity Salinity was measured with a T/C re&actometer( Ameri- can Optical Orp.). Salinity at Station 1 varied greatly according to the irregular rainfall pattern. During most of 197 1 -72, the salinity varied from ca. lO%o to ca. 307(»» but drought combined with high air temperature and intense sunlight raised the salinity to 56 in June 1971. However, heavy rains in June and July reduced that salinity to AVoo within a few days. In contrast. 1976 was an extraordinarily dry year. At Station I from March 1 3 to April 1 6. total precipitation was ca. 27 mm (seasonal noim 182 imn). The ditch became almost dry in April, and the remaining stagnant pools became hypersaline at ca. 807oo . But on April 12. a single intrusion of sea water al a spring tide raised the water level to 40 cm and lowered the salinity to thatof normal sea water. It appears that fructuatioas in salinity over arange of ca. 2Ww are a usual occurrence in spring and early summer. TheSfryoo event rcpre.sents an extreme dial the fauna of the ditches must endure occasionally, possibly by retreating to the underbark refuge out of water. This may present other stresses, such as high temperature and the risk of desicca- tion. Temperature Temperatures were measured from April to August 1971 with a mercury thermometer. From late September 1971 to early February 1972, water temperature was mea- sured each week with a permanently submersed maximum- 20 Rasmussen minimum mercuiy thennomeier that showed the tempera- ture rangeduringihcpastseveii days. From March 14-27» the temperature range was measured continuously with a Gram Miniature Temperature Recorder with siK channels registering the air temperature, water surface temperature in the middle of the ditch, water surface temperature near the bank, temperature near the bottom, temperature 1 cm in the mud bottom and temperature 1 5 cm deep in the mud with a water level ranging from 0.5 to about 40 cm (Figure 3). Rainfall records for 1 97 1 -72 were ob lained from the meteoro- logical station of the University of Georgia Marine Institute. During the 1976 sampling, precipitation was checked by a rain gauge placed on the ground close to Station 1. Water level was measured daily against a measuring rod placed in the ditch (Figure 2). The temperaturerange at Station 1 was very large, both seasonally and daily , influenced by changes in air lempera- tuie and solar radiation. A fter a period of rhythmic fluctua- tions in April and May 1971 varying between 22‘’C and 32'^C, the honest period in the 1971-72 study came in June and lasted through September, with a peak of nearly 37'’C in June. A more precise estimate of the temperauire range was achieved with the introduction of regular maximum- minimunv temperature recording of the ditch system water from September 26 through the rest of the research period. A minimum of O^C was recorded in January 1972, From March 14-27, 1976, the water level of the pool in Station 1 varied between 10 and 27 mm and the tempera- ture ranged between 12®C and nearly 3 PC, never attain- ing the low level of the air due to the strong solar radiation (Figure 3). Whatmay be more important is the fact that the narrower temperature range in the mud (15®C to 26.5° at 1 cmdeptli;20°to30°Cat 15 cm) might enable some mobile animals to survive under extremeenvircHunenval conditions by burrowing into the mud. However, such an escape may subject themtoanoxicconditions.andM was never actually found in the mud in this study. Namalycastis abwma Descriptive Notes Mature specimens measure about 50 to 100 mm in length, with up to 170 setigers. Body with two, not distinctly separable sections. Anterior third to half rather slender and cylindrical with relatively few segments, rest of body becoming flattened posteriorly, with segments in- creasingly shorter. Livingammalstranslucenkunpigmented. Color determined by contents of red blood, increasing in intensity posteriorly. Dorsal surface somewhat glossy in reflected light. Epidennis of each segment witli fine transverse wrinkles (Figure 4). Prostomium trapezoidal, anteriorly incised, with short median groove. Two small conical antennae and two conspicuous, broad palps with distinct palposiylcs; the palps arc rhythmically extended when the worm crawls. Posterior part of prostomium broader with two pairs of eyes, black in reflected light, the outer eye on each side larger (Figure 4). Four pairs of tentacular cirri, the hindmost pair longest. First segment achaetous. Pharynx strongly built, without paragnaihsorpf^- SAPELO ISLAND DITCH SYSTEM NO. 1 TEMP RANGE MARCH 14.-27.1976 ^C 5 10 15 20 25 30 35 I I I I • AIR SURFACE "j NEAR BANK I WATER NEAR BOTTOM J 1 CM IN ^ ^ 15 CM IN J I BOTTOM Figure 3. Temperature range in air and ditch at Station 1, Sapelo Island, Georgia, March 14-27, 1976. Measured continuously during this period with a six-channel temperature recorder. All measurements, except "near bank", made over and In the central and deepest part of the diteb. The “bank" channel was at the surface near the water edge. Depth during recording from 10 to 27 cm, falling to 9 cm. Aberrant Nereidid Polychaeie of Georgia Salt Marsh 21 Figure 4. A^orfui/))<;as/uofriomu(MuUermGrube, 1871). Adult specimen from Station l,Sapelolsland, Georgia, November 1971, showing anterior and posterior ends of Ibe body. Drawn IVom life with Ibe aid of a camera lucida. lafi. with two dark biowiL Strong chidnous jaws (Figures). Jaws ooncave,almosispoon-shaped, in living animals visible through the first2-3setigers;median edge of eachjaw with arowof teeth. The lenninal tooth, somewhat separated from the row of teeth, slightly larger than the rest Each jaw with Fine growth rings. Parapodia sub>biramoiis with noto* and neuiopodial aciculae. dark brown or almost black, Notopodia normally reduced, without setae except for an occasional, slender heterogomph spiniger. Dorsal cirri anteriorly slender and small, conically sh 2 y)ed; postcriody long, flattened leaflike in structure with constricted terminal tips and a very' rich supply of fine c^illary vessels. Ventral cirri small throughout. Aberrant Nereidid Polychaete of Georgia Salt Marsh 23 Mature individuals wilh 11 to 21 neuroselae in each fascicle; neurosctae of two types: hctciogomph falcigers, numbering maximally 9 per fascicle, and heterogomph spinigers with up to 12 per fascicle (Figure 5). Highest number of each sctal type per fascicle found in the firs t third of the body, declining in number posteriorly. Any bundle of setae wiihdominanccof spinigers. Heterogomph falcigers with blades finely denticulated, sometimes at base onJ y and of varying lengths (Figure 5B-C). Heterogomph spinigers with long, finel y den ticulate blade tapering into hair like tip. Both falcigers and spinigers wilh dense structure of trans- verse lamellae in cote of shafi, most distinct in falcigers. The dorsal, longitudinal vessel has a slightly meandcr- ing course in the first few segments, with meanders increas- ing in amplitude considerably toward the posterior end (Figure 4) (normally straight in ncieidids (Lindroth, 1938; Nicoll, 1954). Ihecapillarysupplyisextracmhiiaiilyiichinche dorsal part of theposterior segments and iniheleaflike, flattoied dorsal cirri. Fresh dissection and sectioning of adult worms from Sapelo Island has shown that each segment in the worm body has pulsating “gill hearts” composed of two contractile chambers (Figure Fcuertxrm (1931) has de- scribed such hearts in Namalycastis ranaaensisi otherwise, they arc rarely reported in nereidid wonns (Nicoll, 1954). Biological Observations N, abiuma was recorded from early November 1971 to January 1972 and February-March 1976, with greatest abundance in fall and winter. It was found under the bark of rotten pine trunks and branches in or above the ditch water. Heard (1982) also noted the presence of N. abiuma in Mississippi living under nearly semi-terrestrial condi- tions. Except during the period from November 1971 to March 1972. N. abiuma was not observed anywhere in the ditches, not even the mud bottom. AH specimens recorded had guts filled with wood pieces (Figures7-8) and the inside of the surrounding bark had distinct marks made by the jaws of the worms. N. abiuma lives freely under thebaik and has no permanent tubes; the worms crawled away quickly when bark was removed from the branches. In some cases, they could live semi-terrestrially in the wood pieces since parts of the branches protruded freely in the atmosphere. The worm proved to be a very fast swimmer when released from the wood. It seems likely that the wonns under the bark were foraging, perhaps prior to reproduction. AH worms taken in November were large, mature individuals with smaU eggs in their segments. The spring specimens were smaller and without sexual products. Earlier accounts (Heard, 1982) have established that N. abiuma is able to survive under very extreme environ- mental conditions. At very low oxygen tensions, the posterior end of the worm, wilh its foliaceous cirri rich in capillary vessels, is seen extended from holes in the bark and waving freely in the surrounding water (aquarium observations. Sapelo Island). This was also observed by Feuerbom (1931, p. 650) for Lycastis (Namalycastis) ranauensis and personally lotbJereissuccinea from Sapelo Island (see below). Figure6. (Muller In Grube, 1971). Schematic diagram of the vascular system showing the main segmental vessels. CIV, drcum-intesllnal vessel; DC, dorsal cirrus; DLV, dorsal longitudinal vessel; G, gut; GH, gill heart; VLV* ventral longitudinal vessel; VNC, ventral nerve cord. 24 Rasmussen Figure?. Namalycastisabiiuna, Sapelo Island, Georgia, November 1971, Station 1. Middle section ofadult, preserved specimen with wood and bark pieces in the gut Little is known about the reproduction and develop- ment of N. abiuma. Only small egg cells were observed in the coelom in the material froin Sapelo Island (November 197 1 ), and developmental details were not obtained. The only more extensive breeding information for a member of the Namalycastis group is given by Feuerbom (193 1 , Figure 10) ioxLycastis {Namalycasns) ranauensis from Java. He found the species to be hermaphroditic with relatively small eggs» 125-135 p in diameter and laid in a common jelly mass. After about four days the larvae, about 300 p long, hatched into what Feuerborn described and figured as a ciliated neciochaete stage with three setigers and clearly biramous parapodia. The subsequent fate of the larvae was not described. Because of its freshwater habitat, it seems Aberrant Nereidid Polychaete of Georgia Salt Marsh 25 I I—. i I 3mm Figures, Namalycastis abiuma, Sapelo Island, Georgia, November 1971. Fecal pellets from adult specimen with remnants of bark and wood particles. very unlikely that N. abiuwa has a rrcc-swimmingpelagic stage. Only Heard (1982), who kept individuals of N. abiurm in aquaria, mentioned large eggs with direct devclopmeni as the most likely form of propagation of the species, but gave no further mformaiioa Otherwise, there are virtually no details of file propagation of other Namafyatstis species. Faunal Assodations The survey below comprises benfliic species living associ- ated with Namalycastis abiuma on or under the bark of dead and windfallcn branches mostly of pine trees, predominantly the loblolly pine, Pimis laeda L„ lying in the brackish waiter of S^qielo Island ditches. A indicates presence under bark and in wood A indicates presence on surface of branches POLYCHAETA A Nereis (Neanthes) succinea (Frey and Leuckari, 1847). Very common at all examined places, both in 1 971-72 and 1 976, Often large specimens; maximum length of living animal 170 mm. It burrows under baik and seems to feed on decaying wood. The animals were surrounded by brownish excrement masses, undoubt- edly originating from devoured wood remnants. Indi- viduals from March 24, 1976 werealmost sexually ripe and in the heteronereid stage. Under low oxygen tensions combined with high water temperatures, the posieriorend of the worm , with its many ligules rich in capillary vessels, was seen e^ttended aiRl waving freely in the water (laboratory observations). In case of extreme low oxygen conditions, the species may leave the water aiMi live partly amphibious under the bark of branches exposed to the air. 26 Rasmussen A Stettoninereis martini Wescnbcrg-Lund, 1958 This tiny aberrant nereid species is another remark- able member of the decaying wood biotope of the tidal ditches of Sapelo IslandL It was found both during 1971-72 and in March- April 1976, frequently in groups of up to six individuaLs at a time and always in grooves under the bark. AU specimens were taken only in the spring in different parts of the ditches. Living individuals measured 7- 12 mm. One ripe male specimen was collected on April 16, 1976. The morphology and systematic characters of the exam- ined specimens agree with the description given by Petdbone, 1971. TTic species occurs mainly in tropical-subtropical America. Since first described in 1958 by Wesenberg- Lund from St. Martin in the West Indies, it has been recorded from the eastern and northwestern parts of the Gulf of Mexico and from North Carolina. It is known from open water and tidal ponds with great fluctuations in salinity (St. Marlin) and penetrates into environments characterized by widely fluctuat- ing conditions: warm mineral springs (Florida), salt marshes (Texas and Mississippi)^ Spariina marsh (North Carolina), and on silt and muddy substrate with litUe or no oxygen (Hartman, 1958; Petlibone, 1971; Williams et al., 1976; Gardiner and Wilson, 1977; Heard, 1982). ^Poiydora fign/ Webster, 1879 Unee smaller specimens inmud tubesunderpine tiecbaik. A Hobsonia florida (Hartman, 1951) A single, ca. 12 mm long specimen in mud tube under bark, BeU Marsh ditch system (Station 10), March 28, 1976, salinity 8. The systematic characters agree with the description by Banse, 1979. CRUSTACEA A Balanus eburneus Gould, 1841 Fairly common, especially on the undersides of the branches; maximum basic diameter 25 mm. Newly settled individuals present on March 28, 1976 in the Bell Marsh ditch system. A Balanus improvisus Darwin, 1854 Common, predominantly on the sheltered sides of the branches. On November 11, 1979, numerous small, newly-seiilcd specimens present, less than 1 mm across. On April 23, 1976, pelagic larvae in abundance at Station 1. A Hargeria rapax (Harger, 1879) = Leptochelia rapax Harger, 1879 1 female with eggs, 3.5 mm long, under bark, Bell Marsh diich system, March 28, 1976. A Cyaihura polita Stimpson, 1855 Single specimen under bark. Bell Marsh ditch system, March 28, 1976. ^A Cassidinidea ovalts (Say, 1818) = C. lunifrons (Richardson, 1900) In quantity under bark. From both Station 1 and the Bell Marsh ditch system, where a few individuals were observed crawling cm branches. Females with eggs, March 28, 1976. A Sphaeroma terebrans Bate, 1866 = S, destructor Richardson, 1897 In quantity under bark and inship worm-bored branches in all ditches examined. ^A Gammerus daiberi Bousfleld, 1969 Adult specimens numerous on and under the park of pine branches, al.so in wood bored by shipworms, salinity 87oq. Females with eggs, March 28, 1976. This American endemic species is rather newly de- scribed by Bousfleld (1969). IthasarestricteddLstribution in estuarine systems from the Delaware and Chesapeake Bay rcgKXis south to SouihCarolina AocordingtoBousfield, the most dense populations arcatsalinitiesofl-57i» andin mid-water to near bottom depths. It may be found at 15®Aw salinity, then largely pelagic: and devek^ent within one year. Ovigenous females occur from March to October. Its occmience on Sapelo Island seems to be the most southern on recoid. AA Melita nitida Smith, 1873 Adult specimens (both sexes) common under pine tree bark at Station 1 , November 1971 and January 1972. In March 1976 on and in rotten ranches. A Uhlorchestia uhleri (Shoemaker, 1936) Often in numbers, crawling on submerged parts of branches close to the water surface. A Panopeus herbsii H. Milne-Edwards, 1834 Two young females, carapace width 12 and 13 mm, in empty shipwomi tubes. A Euryiium limosum (Say, 1818) Two males, carapace width 5.5 mm, under bark, Sta- tion 1, January 20, 1972. A Sesartna reticulatum (Say, 1817) One female, carapace width 7 mm, under bark, Station 1, January 20, 1^2. A Sesarma cinereum (Bose, 1801 or 1802) Common under bark, carapace width 2.5 to 16nim, Station 1, 1971-72 and 1976, INSECTA A Chironomkl larvae, blood-red species, a few *m mud tubes under bark. A Odonata, unidentified species, a single larva under bark; November 11, 1971 at 20“/® salinity. MOLLUSCA A A Melampus bidenlam Say, 1822 A few small specimens under bark in water; also observed crawling on submerged parts of the branches. Aberrant Nereidid Polychaete of Georgia Salt Marsh 27 A Geukensia demissa (DiUwyn, 1817) = Modiolus demissus (JDillyfyn, 1817) A few byssally^attached specimens under bark, length about 1 5 nun, A Crassoslrea virginica (Gmelin, 1791) Common on branch surfaces, maximum size 80 mm, many dead sheUs. A Bankia gouldi Bartsch, 1908 Fairly common, often in small and thin branch pieces. A Teredo bartschi Clapp, 1923 Fairly common, often in small and thin branch pieces. ENTOPROCTA ^ Barentsia sp. Not very common, on surface of bark in various ditch systems. ECTOPROCTA Living colonies of the following species were found in abundance on the surfaces of branches, attached barnacles and oysters, A Membranipora tenuis Desor, 1848 A Electro monostachys (Busk, 1854) A Conopeutn temissimum (Canu, 1928) A Bowerbankia gracilis O’Donoghue, 1926 A Alcyonidium polyoum (Hassall, 1841) A Victorella sp. ASCIDIACEA A Molgula manhattensis (De Kay, 1843) Present, but uncommon, as large specimens on the outer surface of branch pieces. ACTINURIA A Even one tiny unidendfied flesh-colored sea anemone was taken under loose pine bark below sea water. Discussion In considering the taxonomic status of Abimm, even generally established systematic characters must be used with care. For example, the position of theeyes of /V. abiuma may be differeiUaccx)ixlingtothecofidiUonoft]iejHeservcdiTiaisrial. In the Sapelo Island material, living woims had the eyes in a transverse row (Hgure4), while they were behind each other in preserved and somewhat shrunken ^)ecimcns. An aid in species scpaiaiion within the genus Atortfl/ycas/« may be offered by possible differences in i nodes of propagation and developinenL Hartman (1959, p. 163) mendmis one form of the type species (Paranereis (Namalycastis) abiuma Muller in Giube, 1871) from Brazil, which was described as having small eggs and separated sexes, with no mention of fimher development. Another form {N. ranauensis) widi small eggs. hennaphioditism,andafux:tochaetestago(pcihapspelagic)was described by Feueiboni( 1931). Both forms wereftom freshwa- ter. The results of Heard (1982) indicaie large eggs and diiea developmcnl for what he consideis to be the type species N. abiuma from brackish water. Still rather incomplete, these descriptions, apparently with the same external characters, may suggest llueediffereruspedesatany rate. Furihersludiesonthe bteedingbiology of this aberrant group may providcaclue to the ^xsciaiion problems within the genus Namalycastis. The ingestion of decaying and rotten wood seems to be unknown for nereidids and pediaps for polychaete worms as a whole (Fauchald and Jumars, 1979). Not only Namalycastis has this peculiar feeding patterns, hulNereislNeanihes) suednea also consumes decaying wood, as shown in this study. It seems reasonable to assumeihat the fractionof importance for the two species is the microargarusnis of the wood. Off ttre German coast, N. succinea is a deposil-feeder and detritus-feeder(Goerke, 1971). N.ab/u/Twinayalsobeadeposil- feederinotherparisofiisrangeofdistnbution. Thus their diets may vary greatly and both may be characterized as omnivoies. However, aspobiled ouvby Fauchaldand Jumars ( 1979, p. 255), widely dLspersed species feeds on a limited range of inatcrials, indicting that, while the species as a whole may be omnivoroiis, eachpopulation may be functionally specialized.” The ifouna associated with N. abiuma in or on fallen branches in the ditch watercompriscs 34 benthic species. Apart from the two freshwater insects, the remaining arc brackish- waier.estuarineoreuryhaline marine species. There is a clear dominance of crustaceans with 13 species, followed by five polychaetes, five molluscs, and six ectoprocts (bryozoans). Acknowledgments Special thanks arc expressed to Professor V.J. Henry, former director of the University of Georgia Marine Institute, for arranging my visit in 1971-72 as a staff member at the station. Thanks are also extended to all personnel for their kind help and assistance during my visits. I am indebted to Professor W.D. Burbanck and the late Professor Ralph 1. Smith for helpful comments in reviewing the manuscript, and to Professor C. Overgaard Nielsen for correcting and revLsmg the manuscript. I am indebted to the following experts for their aid in the identification work: Dr. J. Just, Zoological Museum, Copenhagen; Dr. R. Turner, Museum of Comparative Zoology, Harvard University; Dr. K.B. Hansen, Zoologi- cal Museum. Copenhagen: and Dr. Pairicia Kotl, Queensland Museum, Australia. Lastly, I would like to acknowledge financial support provided by the Danish Natural Science Research Council and the Carlsberg Foundation. The material collected is deposited in the Zoological Museum, Copenhagen. 28 Rasmussen Lf 1' 1 ilRA'ITJRE OrTED Bous field, E.L. 1969. New records of Gammarus (CrustaccaiAmphipoda) from ihc Middle Atlantic Region. ChesQpeak£ Sci. 10.1-17. Fauchald,K.andP,A. Jumars. 1979. Thcdietofwoims: a study of polychaete feeding guilds, Oceanogr, Mar. Biol. Ann. Rev. 17:193-254. Feuerbom, HJ. 1931. Ein Rhizocephale und zwei Polychacten aus dem SUsswaascr von Java und Sumatra. Verh. Jm. Verein. Theor. Angew. Limnol. 5:618:660. Foster, N .M. 1972. Freahw atcr polychaetes (Annelida) of North America. Bioia of Freshwater Ecosystems Identification Manual, U.S. Government Printing Office, Washington, DC. pp. 1-15. Gardiner, S.L. 1976(1975). Errant polychactc annelids from North Carolina. J. Elisha Mitchell Sci. Soc. 91(3);77-220. Gardiner. S.L. and W.H. Wilson. 1979(1977). New records of polychactc annelids from North Carolina with the descrip- tion of a new species of Sphaerosyll'is (Syllidac). J. Elisha Mitchell Sci. Soc. 93(4): 159-172. Goerkc, H. 1971. Die &nJilirungsweisc dcr Nereis-AiiXsn. (Polychacta,Nercidac) der deubchen Ktisten. Verdf. Inst. Meeresforsch. Bremerh. 13:1-50. Grube, E. 1871. tJber die Gattung Lycaslis und cin Paar ncuc Arten derselbcn. Jahresber. Schles.Gesetls. Vaterl.Kultur, Breslau 49:47-48. Hartman, O. 1958. A new ncreid worm from warm mineral springs, Ra., with a review of the genus Nicon Kinberg, J, Wash, Acad. Sci. 48:263-266. , 1959, Capitellidac and Ncrcidae (marine annelids) from the Gulf side of Horida, with a review of freshwater Neieidac. Bull. Mar. Sci. GuJfCaribb. 9(2): 153-168. Heard, R.W. 1975. Feeding habits of white catfish from a Georgia estuary, Biol. Sci. 38(l):20-28. . 1982. Guide to Common Tidal Marsh Invertebrates of l he Northeastern Gulf of Mexico. Missi ssippi- Alabam a Sea Grant Consortium, pp. 1-82. Hutchings, P.A. and C.J. Glasby. 1985. Additional mcreidids (Polychacla) from eastern Australia, together with a rede- scription of Namanereis quadraticeps (Gay) and the synonymising of Ceratonereis pseudoerythraeensis Hutchings and Turvey with C. aequiset 'ts (Augener). Rec. Austr. Miir.37(2):101-110. Lindroth, A. 1938. Studien liber die rcspiratorischenMechanismcn von Nereis virens Sars. loot. Bidr. Upps. 17:367-497. NicoU.P.A. 1954, Theanalomyandbehaviourofdievascularsystenis in Nereis virens and Nereis limbaia. Biol. Bull. 106:69-82. Pettibone, M.H. 1971. Revision of some spuncs referred to Leptonereis,Nicon^m(iLaeonereis(Po[ych^la:Nerci6id3£). Smithson. Contr.Zool. 104:1-53. Rickards, W.L. 1968. Ecology and growth of juvenile tarpon Megalops atlaruicus in a Georgia saltmarsh. Bull, Mar. Sci. 18(l);220-239. Russell, B. 1962. Some nereid polychaetes from Queensland. Papers Department of Zoology, University of Queensland 2(1):M2. Wesenberg-Lund.E. 1958. Lesser Antillean polychaetes, chiefly from hrackish-watcr, with a survey and a bibliography of fresh and brackish- water polychaetes. St ltd, Famaof Curasao and Other Caribbean Islands 8:1-41. Williams, G.E. in e/ o/. 1976. WeatemGulf of Mexico records of 5renoni/terefr/nar/ini Wesenberg-Lund 1958 (Polychaeta, Ncrcidae) with contributions to its habitat ecology. Contr. Mar. Sci, 20:83-85. Gulf Research Reports Volume 9 | Issue 1 January 1994 A New Species and Two Known Species of Free-Living Marine Nematodes (Nematoda: Monoposthiidae) from Northwest Florida^ U.S.A. Edwin J. Keppner DOI: 10.18785/grr.0901.03 Follow this and additional works at: http:/ / aquila.usm.edu/ gcr Part of the Marine Biology Commons Recommended Citation Keppner, E. J. 1994. A New Species and Two Known Species of Free-Living Marine Nematodes (Nematoda: Monoposthiidae) from Northwest Florida, U.S.A.. Gulf Research Reports 9 (l): 29-38. Retrieved from http://aquila.usm.edu/gcr /vol9/issl/3 This Article is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf and Caribbean Research by an authorized editor ofThe Aquila Digital Community. For more information, please contact Joshua.Cromwell^usm.edu. Guif Research Reports,\ol 9, No. 1, 29^38, 1994 Manuscript received March 19, 1993; accepted June 1, 1993 A NEW SPECIES AND TWO KNOWN SPECIES OF FREE-LIVING MARINE NEMATODES (NEMATODA; MONOPOSTHIIDAE) FROM NORTHWEST FLORIDA, U.S.A. EDWIN J.KEPPNER 4406 Garrison Hoad, Panama City, Florida 32404 ABSTRACr Two known free-living marine nematodes, Monopost hioides mayri Wicser and Hopper, 1967 and Monoposlhia hexalata Chitwood, 1936 arc redescribed from sediments in St. Andrew Bay and Lake Powell, Bay County, Florida, U.S. A, One new species of free-living marine nematode, Monoposthia baxterin. sp., is described from nonvegetated sediments in St Andrew Bay, Bay County, Florida. Af. baxteri n. sp. differs from the other members of the genus in the shape of the gubemaculum which is more similar to that of the species of Monopost hioides than that of Monoposthia. Introduction According lo Lorenzen (1981), the family Monoposthiidae Filipjev, 1934 contains the genera Monoposthia de Man, 1889; Monoposthioides Hopper, xmiNudora Cobh, 1920, m6Rhinema Cobb, 1920. Tlie Monoposthiidae are characterized by the presence of a cuticle w ith strong transverse striations forming annuli, and a number of longitudinal cuticular ridges that appear as V-shaped markings. Vanreusel and Vincx (1989) referred to these structures as costae. The amphids are circular and are situated on the second annulus. The buccal cavity has a well-developed dorsal tooth and may have one or more ventral teeth or denticles. Specimens of two of the four genera of the Monoposthiidae were collected from estuarine waters in northwest Florida. The two known and one new species of frec-h ving marine nematodes in the gGnemMonoposthioides Hopper, 1963 and Monoposthia de Man, 1889 redescribed and described, respectively, herein were collected from subtidal sediments in St. Andrew Bay and Lake PowcD, Bay County, Florida. The sediments from the collection sites in St. Andrew Bay and Lake Powell were nonvegetated fine sand and silt. Materials and Methods Sediment samples were obtained with a cylindrical core sampler lo a depth of 4- 10 cm, depending on the site. Nematodes were extracted from the sediment by repeated decantation. The suspended material from four washings was allowed to settle forl5-20minutes,and the supernatant water was decanted. Nematodes were removed alive from the settled material and fixed in hot alcohol-formalin-acetic acid or hot 4% formalin in seawater for 24 hours. Speci- mens were dehydrated 'm glycerine by gradually bringing them 10 70% ethyl alcohol and glycerine (9: 1) and allowing the alcohol to evaporate. Specimens were mounted in anhydrous glycerine on Cobb slides. Specimens were deposited in the Florida Nematode Collection, University of Florida, Gainesville, Florida (UFNC). All measurements are given in pm unless otherwise staled , and the mean is followed by the range in parentheses. Abbreviations; 1 = length of body in nun. w = width at midbody, hd = head diameter at level of first annulus, cs = length of cephalic sensilla. ad = width of amphid. aa= anterior end to anterior margin of amphid. be = length of buccal cavity, nr = anterior end lo nerve ring, es = length of esophagus. i = length of tail, cw = width at cloaca, aw s: width at anus. av=: anterior lo vulva. a,b,c,V=demanian ratios. Taxonomic Account (After Lorenzen, 1981) Chromadorida FUipjev, 1929 Monoposthiidae Filipjev, 1934 Monoposthioides Hopper, 1963 Monoposthioides $nayri Wieser and Hopper, 1967 Figures 1-12 Description: Body relatively short, broad. Cuticle coarsely aimulated; annuli originate immediately posterior to cephalic sensilla; first and second annuli larger than succeeding annuli. Annuli are complete lateral to cloaca. 29 30 KHTNOt Costae in 12 longitudinal rows; fully developed V-shaped costae originate between annuls 10and20frDfn anterioroid [(38.5(30-56) in males; 60(50-77) in females). Apex of costae directed posleriorly then reverse to anterior duection 234.7(218-256) from antedor end in males, 3 19.7(301-346) in females. In males, lateral, subvential, and ventral rows of costae termifiate at level of clocal opening; remaining rows terminate immediately posterior to cloacal opening. In females, suhventral and ventral tows of costae tenninate at level of vulva; remaining rows terminate posterior to anal opening. Head withcircleof six, $mall,iimerlabialsensiUa immediately adjacent to oral opening. Circle of six papilliform outer labial sensill and four long, setiform ce{Mic sensilla present. Long cervical, somatic, and caudal scnsilla present as subdorsal andsubvcncral rows on each lateral suri^ace. Amphid circular, situated on second annulus. Buccal cavity with cyathifoim anterior chamber with circle of 12 small, flap-like structures. Anterior cliainber of buccal cavity elongate with culicularized, parallel walls. Esophagus with asymmetrical peribuccal expansion; dorsal side larger. Large, muscular, bipartite, posterior, esophageal bulb present with moderately cuticuiarized lumen. Excretory pore not observed. Tail conical, terminal one third without annuli; spinneret and caudal glands present. Males (a = 6); 1 = 1.15(1.01-1,28). w =40.1(38-43). hd= 16(14-17). cs = 22(21-24). ad = 2.8(2.5-3.n). aa = 13.8(13-16). be = 23.7(19-27). nr=68(61-75). es= 144.2 (125-155), 1 = 99.8(93406). cw = 31<29-34>. a = 28.6 (26.6-31.6). b = 7.98(7.23-8.53). c = 12,1(10.6-15.3). Male reproductive system diorehic. Large, non-striated, precloat^piocesspresenL SpiculesabsenL Single, heavily cuticuiarized gubemaculum present. 46.6(45-48)arc.51(48- 56) chord long, arcuate with proximal flange, dorsally directed process of flange longer than ventmlly directed process. Females (n =3): 1=1,15(1.11-1.20). w = 50(48-51). hd= 16.7(16-18). cs= 19.7(19-21). ad = 4.0(3.0-5.0). aa = 13.3(1344), be = 25.3(22-27). nr = 78(72-82). e5 = 157(144-173). t = 94(90-101). aw = 25.7(24-27). av = 979(949-1020). a =22.9(2 1.8-23.5). b= 7.33(6.94-7.85). c= 12,2(11.9-12,6). V=85.3%(85-86). Female reproduc- tive system monodelphic, prodelphic, ovary reflexed. Vulva with cuticular flap. Specimens: Males. UFNC A157. A158, A159; fe- males, TJFNC A160. Locality: St. Andrew Bay, Bay County, Rorida (SODS’SS^N, 85'*42M3''W). Nonvegetated fine sand and sill. Remarks; The specimens described above arc consid- ered to be Monopoithioides mayri based on the shape and size of the gubernaculum of the male, Ihe enlarged second annulus, and the shape and size of the amphid. In the original description of M. mayri, the buccal cavity was described as having a single, large, dorsal tooth and small subventrsl projections. These projections are part of three circles of small denticles that are not easily observed. The presence of inner labial sensilla was not mentioned in the original description or figured on the drawings. The male specimens described above differ from the original descrip- tiem of the male in that the costae reverse at a greater distance from the anteriorend [234.7(218-256) vs. 140] and the cephalic sensilla are longer [22(21-24) vs. 17]. The female specimens described above differ from the original description of the females of M. mayri in that the “V” value is less than that of M mayri (85-86% vs. 9ft;92%) and the costaereverse somewhat mote posteriorly than inM. mayri (301-346 vs. 240-250 from the anterior end). Monopostkia de Man, 1889 Monopostbia baxteri n. sp. Figures 13-21 Description; Body relatively short, broad, (^ticlc coarsely annulated; second annulus with anterior bulge at location of amphid. Annuli incomplete subventrally and ventrally in cloacal region of male. Costae in eight longi- tudinal rows; dorsal, subdorsal, suhventral, and ventral rows originate on tliird annulus, lateral rows originate on annulus 13-15. Apex ofoostne directed postcrioily. reverse direction on annulus 83-88 from amerior end (posterior to esophageal bulb) in males; costae did not reverse in single female examined. In males, laterals, subvenirals, and ventral rows of costae tenninate at about level of cloacal opening; subdorsals and dorsal rows of costae terminate posterior tocloacal opening, frifemale.laterals, subvemrals. and ventral rows of costae tenninate at vulva; subdorsals and dorsal rows terminate immediately posterior to anal opening. Head with circle of six. setifoim. inner labial sensillaimmediately adjacent to oral opening. Circleof six, setiform, outer labial sensilla and circle of four, long, sedfonn cephalic sensilla present Amphid circular; situ- atedon second annulus. Long cervical, somatic, and caudal setifoim sensilla present as suhventral and subdorsal rows on each lateral surface. Buccal cavity with anterior cyatfiifonn chamber with 12 Qap-like structures. Large, heavily cuticuiarized, dorsal tooth and three circles of denticles present. Circles of denticles broken subdorsally and dorsally. Posterior chamber of buccal cavity elongate with cuticuiarized, parallel walls. Peribuccal region of esophagus expanded, asymmetrical; dorsal side larger. Large, muscular, bipartite, esophageal bulb with we^y cuiicularizcdlumenprescntposieriorly. Excretory pore not observed. Tail conical, terminal one third without annuli; Spinneret and caudal glands present. Males (n =2); 1=1.05(1.04-1.06). w=56(54-58). hd = 22(22-22). cs = 26.5(26-27). ad = 3.0(3.0-3.0}. aa = New and Known Species of Marine Nematodes 31 10(10-10). be = 30.5(29-32). nr = 81(80-82). es = 157.5(155-160). cw = 36(35-37). l = 55(54-56), a = 18.8(18.3-19.3). b= 6.67(6.50-6.84). c = 11.6(11.4-11.8). Reproductive system diorchic. Non-slriated. precloacal process present. Spicules absent GubemacuJum large, 55(54-56) arc, 60(59-6 1) chord Iong,arcuaie, thorn-shaped with inner cuticularization. Distal end expanded with ventral process longer than dorsal process. Small teeth present on ventral surface of proximal tip of gubemaculnm in paratype male, not observed in holoiype male. Cuticle inflated in one place on midventral surface anterior to cloaca. Female (n = 1): 1= 1.02. w = 51. hd= 18. cs = 21. ad = 4. aa=ll. be = 29. nr =77. es=144. aw = 27. t = 83. av = 914. a = 20.0. b = 7.08. c = 12.3. V == 90%. Reproductive system monodelphic, prodelphic, ovary re- flexed. Vulva with cuticular flap. Specimens: Male, holotype, UFNC A166; male, paratype, UFNC A168; female, allotype, UFNC A167. Locality: St. Andrew Bay, Bay County, Florida (3(>f)833"N, 85'^42’43"W). Nonvegeiatcd fine sand and silt. Remarks: Hopper (1963) erected the genus Monoposthioides to accommodate the species Monoposthioides anonoposthia Hopper, 1963 that was collected from the northern coast of the Gulf of Mexico. The genus Monoposthioides can be differentiated from the genera Nudora, Rhinema and Monoposthia in that the costae originate about midlevel of esophagus in Monoposhtioides rather than on the second or third annulus as in the other Uiree genera. In addition, Monoposthioides differs from Nudora and Rhinema hi in the absence of spicules. Monoposthioides is most similar to the genus Monoposthia in that the spicules are absent and a single well-developed gubemaculum is present. Hopper (1963) differenliaied Monoposthioides from Monoposthia on the basis that the costae originate much more posteriorly in Monoposthioides^ the gubemaculum of the male in Monoposthioides is relatively larger and more arcuate with a large, ventrally directed process proximally and long spine distally, and the reproductive system of the male in Monoposthioides is diorchic. Wieser and Hopper (1967) emended the diagnosis of Monoposthioides to include the species Monoposthioides mayri Wie-ser and Hopper, 1967. In M. mayri, the long, distal spine of the gubemaculum is absent and the dorsal process of the proximal end of the gubemaculum is longer than the vcnual process. The diorchic male reproductive system cannot be used as a differentiating character of Monoposthiodes, because diorchic males of known species of Monoposthia have been described by Kilo (1981 ) and Vanreusel and Vincx ( 1 989). Plait and Warwick (1988) use the diorchic condition of the male reproductive system as a character of the family Monoposthikiae. Therefore, the genus Monoposthioides currently differs from Monoposthia in that the costae originate more posteriorly, and the gubemaculum is rela- tively larger and more arcuate in Monoposthioides. Monoposthia haxteri n. sp. has characters of both Monoposthia and Monoposthioides. It is similar to Monoposthia in that (he costae begin on the third annulus and to Monoposthioides in that the gubemaculum is rela- tively large, arcuate, and the proximal end has a large ventral process. Monoposthia baxteri n.sp. is placed in the gtnus Monoposthia based on the origin of the costae on the third annulus. Monoposthia baxteri n. sp. is differentiated from all other members of the genus Monoposthia on the basis of the shape of the gubemaculum. It is the only species with a large, arcuate gubemaculum with an expanded proximal end with the ventral proce.s.s longer than the dorsal proces.s. Etymology: Monoposthia baxteri n. sp. is named for Dr. George Baxter, Professor Emeritus, University of Wyoming, in recognition of his work and teaching in aquatic biology. Monoposthia hexataia ChitwoodT 1936 Figures 22-29 Descriprion; Body relatively short, broad. Cuticle coarsely annululated. Second annulus not significantly larger than succeeding annuli but with an anterior bulge where the amphid i.s located. Annuli complete laterally and ventrally in cloacal region of male, but these annuli are not as distinct as the surrounding annuli. Costae in six longitu- dinal rows; originate on third amiulus. Apex of costae directed posteriorly, reverse direction immediately poste- rior to esophageal bulb in males, immediately anterior to vulva in females. In males, subventral and ventral rows of costae terminate immediately anterior to cloaca; remaining rows terminate posterior to cloaca. In females, subventral and ventral rows of costae lertninatc immediately anterior to vulva; remaining rows terminate at or near last annulus on tail. Head with circle of six seiifonn inner labial sensilla immediately adjacent to oral opening . Circle of six setiform outer labial sensilla and four long, setiform, cephalic sen- silla present. Amphid circular, situated on second annulus. Cervical, somatic, and caudal setiform sensilla present as subdorsal and subventral rows on each lateral surface. Buccal cavity with anterior cyathiform chamber with 12 flap-like structures. Anterior chamberof buccal cavity with single, large, heavily cuticularized dorsal tooth and pair of small, subventral, denticles; circles of denticles not ob- served. Posterior chamber of buccal cavity elongate with cuticularized. parallel walls. Peribuccal region of esopha- gus expanded, asymmetrical; dorsal side larger. Large, muscular, bipartite, esophageal bulb with weakly 32 Keppner cuticulaiized lumen present posteriorly. Excretory pore not observed. Tail conical; leiminal one third without annuli; spinneret and caudal glands present, Malea(n=5); 1=0.963(0.831-1,06), w= 48.4(43-53). hd= 18.6(17-19). cs = 24,8(22-26). ad = 3. 1(3 .0-3.2). aa = 7.4(7-10). be = 25.6(22-29). nr = 77,6(67-86). cs = 148,8(133-165). cw = 36.6(2443). 1 = 92.2(80-99). a = 20.0(15.7-22.1). b = 6.47(6.1 1-6.82). c= 10.6(8.4-13.0). Reproductive system diorchic. Spicules absent. Gubemaculum claw-shaped 392(34-43) arc, 42.4(36-47) chord long, with proximal expansion with dorsally directed process, internal cuticularizalion, and arcuate distal part. Single large, subvcntral, papillifoim, precloacal sensiilum presenton each lateral surface. Cuticle inflated midventially in two places anterior to cloaca, particularly evident when tail is bent ventrally. Female (n = 1): 1 = 0.945. w = 67. hd = 22. cs=19. ad = 5. aa = 1 1. be = 29. nr = 80. es = 174. aw = 26. t = 82. av = 788. a =14.1, b = 5.43. c=ll.5. V = 83%. Reproductive system monodelphic, prodelphic, ovary re- flexed. Vulva with cuticulariz^ flap. Specimens: Males, UFNC A 16 1 , A162, A 163, A 164; one female, UFNC A 165, Locality: St. Andrew Bay, Bay County, Florida (3(K)8’3 3‘'N, 8542*43 "W) and Lake PoweU, Bay County, Florida (30^16*45"N* 85^* 58’50"W). Nonvegetated fine sand and silt. Remarks: The specimens described above agree closely with the descriptiem and drawings of M. hexalata provided in the original description given by Chitwood (1936). They differ from the original description in that there is a pair of precloacal papillae in the males that were not mentione. Vanreusel,A.andM. Vincx. 1989. Free-living marine nematodes from the Southern Bight ofthe North Sea. IQ. Species of the Monoposthiidae Filipjev, 1934. Cah.Biol. Mar. 30:69-83. Wieser, W. and B.E, Hoiq)er. 1967. Marine nematodes of the East Coast of North America. I. Florida, Bull. Mas. Comp. Zool. Harv. 135:239-344. Gulf Research Reports Volume 9 | Issue 1 January 1994 Behavioral Ecology of Two Teal Species (Blue-Winged Tesl^Anas discors, and Green- Winged Teal; Anas crecca) Overwintering in Marshes of Coastal Louisiana; USA Gary R. Gaston University of Mississippi Jeanne G. Nasci DOI: 10.18785/grr.0901.04 Follow this and additional works at: http:/ / aquila.usm.edu/ gcr Part of the Marine Biology Commons Recommended Citation Gaston, G. R. and J. C. Nasci. 1994. Behavioral Ecology of Two Teal Species (Blue Winged Teal, Anas discors, and Green Winged Teal, Anas crecca) Overwintering in Marshes of Coastal Louisiana, USA. Gulf Research Reports 9 (l): 39-48. Retrieved from http://aquila.usm.edu/gcr/vol9/issl/4 This Article is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf and Caribbean Research by an authorized editor ofThe Aquila Digital Community. For more information, please contact Joshua.Cromwell^usm.edu. Gulf Research Reports, Vol. 9, No. 1, 39-48, 1994 Manuscript received July 21, 1993; accq>ied October 20, 1993 BEHAVIORAL ECOLOGY OF TWO TEAL SPECIES (BLUE- WINGED TEAL, ANAS DISCORS, AND GREEN-WINGED TEAL, ANAS CRECCA) OVERWINTERING IN MARSHES OF COASTAL LOUISIANA, USA GARY R. GASTON' AND JEANNE C. NASCP ‘Department of Biology, University of Mississippi, University, Mississippi 38677 ^3186 Worthington Avenue. Fort Collins, Colorado 80526 ABSTRACT Feeding and other dominant activities of Blue- winged Teal (BWT; Anas discors) and Green-winged Teal (GWT; Anas crecca) were compared from October 1987 to March 1988 in southwestern Louisiana, USA. Three observation towers were constructed near similar inlermediale marsh habitats in areas where BWT and GWT concentrated for feeding. These observation towers allowed activities of the two species to be compared throughout the nonbreeding season. Although BWT and GWT often fed together, time spent in various activities differed. Feeding was the most frequent activity of both BWT (64.5%) and GWT (55.3%), but BWT spent more time feeding (P < 0.01) and alert (P < 0.05), but spent less (P < 0.01) time resting than GWT. Within each species there were differences in activity budgets among daily time blocks and among months, but few differences among the three habitats studied. Temperature and light intensity were correlated with resting (+), feeding (-), locomotion (-), and preening (+). Daily and monthly activity budgets of BWT and GWT were similar, as were ingested foods, suggesting that these two species used the study areas primarily for foraging, and left the areas for other activities. Predation and diminished resources during late winter may have affected activities of BWT and GWT as well. Introduction Blue-winged Teal (BWT; Anas discors) and Green- winged Teal (GWT; Anas crecca) arc two of the most common waterfowl species in North America. Most BWT migrate to Central and South America during thenonbreeding season, but some remain along the U.S. Gulf Coast and overwinter with GWT and other waterfowl. This is the first comparative study of the two species. Most previous studies of BWT concerned breeding or poslbreeding feeding ecology (reviewed by EhiBowy, 1985); however, several studies were conducted recently on activi- ties of nonbreeding GWT (Tamisier, 1976; Bakjassane and Bolen, 1984;QuinlanandBaldassarre, 1 984; Euliss and Harris, 1987; Rave, 1987; Rave and Baldassane, 1989; Gaston, 1992). The purpose of this study was to compare activities of BWT and GWT concurrently, 'niisallowedustocomparcthe two species under identical conditions, which is not possible unless the birds are observed simultaneously. Specifically, our goals were to (1) determine whether BWT and GWT required similar foraging times in habitats used primarily for feeding (inlermediale marshes), since previous studies indicated that BWT and GWT food preferences differed during winter (Bellrose, 1980); (2) determine whether predators affected BWT and GWT foraging and habitat selection, as suggested in studies of other waterfowl species in these coastal Louisiana marshes (Gaston and Nasci, 1989); and (3) determine whether the role of their habitat changed as food resources diminished during winter. Materials and Methods Blue-winged Teal were observed at the 30,756 ha Rockefeller State Wildlife Refuge (S WR) in southwestern Louisiana (sec Paulus, 1982). The area is closed to hunting, public access is limited, and much of it is impounded to control water levels. Birds were observed from blinds (4 m high) located on leveesadjaccnt to three intermediatemarsh impoundments. Intermediate marshes are generally lower salinity (annual salinity range: 0-5 ppL) than brackish marshes, and are transition zones between salt marshes and fresh marshes. The dominant vegetation of intermediate marshes in the study area was wiregrass (Spartina patens), cattail (Typha spp.), bulrush (Scirpus californicus), common reed (Phragmites australis), andbearded sprangletop (Leptochloa fascicularis). Levees surrounding the study areas sup- ported d^ise stands of common reed, which allowed access to the towers with minimal disturbance to waterfowl. The three areas were described by Gaston and Nasci ( 1989). The areas were generally similar, but varied in water level ranges and pond sizes. Observadon was planned in these similaraieasin order tocompareeCfectsof water depdi, weather, andtonporalfdctors. Previous investigaiorscompared vastly different habitats (e.g., Quinlan and Baldassane, 1984; Rave, 1987; Rave and Baldassane, 1989), where extreme variance in teal bdiavior would be most likely, but effects of specific habitat factors could not be assessed adequately. 39 40 Gaston and Nasci Weekly observations of BWT and GWT were made concunenily at three stations from October 1987 to March 1988. Observations were made from 15 minutes before sunrise to 15 minutes after sunset Days were divided into three equal time blocks (morning, midday, and afternoon), and each time block was divided into equal numbers of 15- minute time periods. Random numbers tables were used to select 30 to 36 observation periods per tower each day. Asinglescan was made during selected 15-minute time periods with a 60x spotting scope using scan sampling techniques (sensu Baldassarre et ai, 1988), and all BWT and GWT within 200 m were included in the observations. The activities {sensu Paulus, 1988) were recorded on tally meters as resting (sleeping and loafing), feeding (ingestion of surface or subsurface food), locomotion (swimming, walking, or flying), courting (pair formation and social displays), preening (body maintenance or bathing), alert (attentive to disturbance), and agonistic activities (threat displays). The sex of each individual was recorded. Ail teal within view were counted during every 15-minute period to estimate number of leal using the study areas. During each 15-minute observation period, ambient temperature, cloud cover, wind velocity, rainfall inteiLsity, and light intensity were recorded. Light was measured with an Environmental Concepts LIM 2300 light-intensity meter mounted on a ring stand to measure reflected light from a photographic gray card. Percent cloud cover was estimated by the observer at Station 2, and wind velocity was mea- sured by an anemometer at the Rockefeller SWR weather station. Analysis of variance ( ANO VA) and Duncan’s multiple range test were used to test for significant differences among activities, time blocks, andmonths. Activities were compared among stations using ANOVA and Duncan’s lest (BWT: Stations 1 to 3, a = 297, 254, 196; GWT: Stations 1 to3,a=264,368, 135). Specific activities and differences between sexes (paired sets) of the two species were tested withi-tests. Percent-time data were arcsine transformed for these analyses. Numbers of individuals were totaled for each time block, then percent time spent in each activity was calculated by dividing the number of observations of an activity by the total number of observations, times one hundred, Pearson’s correlation analyses were used to determine relationships between activities and physical variables. Progressive values were used for correlations involving factors of time: 1 to 6 for months, and 1 to 3 for daily time periods (morning, midday, altemoon). To compare the variables of habitat and how they affected each species, principal components analyses were conducted on untransformed data to determine which physical factors varied most with activities. Results Activities Observations of BWT and GWT totaled 424 hours (no occurrence was not recorded as time). Throughout most of the study , there were more males than females of BWT (9:1) and GWT (10: 1) observed; however, there were no signifi- cant differences (P > 0.05) between sexes in time spent in any activity. Sex of BWT could not be confidently deter- mined during October and early November, because most BWT individuals were in eclipse plumage. Male and female BWT observed after November were not signifi- cantly different in their activities. Thus, sexes were not distinguished in the analyses below. Generally BWT spent more time (P < 0.01) feeding (65.4%), more time (P < 0.05) alert (3.1 %), and less time (P<0.01)resting(15.8%)thanGWT (Table 1). Therewere nodifferences (P>0.05) between the species in locomoting, courting, or preening activities. Feeding (BWT: 18.4 to 75.8%; GWT: 10.5 to 77.7%) was the most frequentactivity of these species (P < 0.05) during most months, followed by resting (8.2 to 50.9%; 5.0 to 64.1%) and locomotion (8.2 to 40.7%; 5.5 to 25.5%). Neither species spent much time courting (until March) or alert. Agonistic behavior never represented over 0. 12% of activities per month, and there- fore was excluded from further analyses. Habitat Comparisons Stations 1 and 2 were generally similar habitats, but Station 3 had deeper water and some different vegetation. However, the only significant differences (£= 6.47, 2 d.f. . P < 0.05) in activities among the three stations occurred in BWT during December and January, when BWT at Station 2 fed less than those elsewhere (Table 2). Numbers of BWT at Station 2 (15,533 observed) greatly exceeded those at Stations 1 (5919) and 3 (5922). GWT were also more numerous at Station 2 (36,782) than at either Stations 1 (7825) or 3 (3356). Relatively few BWT or GWT were observed at Station 3 after December, probably due to high water (greater than 1 m depth). Temporal EfTects During October, most BWT and GWT had a regular pattern of morning feeding, resting during midday, and preening for up to an hour thereafter. Few BWT or GWT were seen using the study areas when the observers arrived before dawn, but teal began arriving soon thereafter. Dur- ing October and November, many BWT and GWT were observed leaving the observation areas at Stations 1 and 3 TABLE 1 Activity budgets by month for Blue-ivinged Teal and Green-Winged Teal wintering at Rockefeller SWR, (Cameron Parish, Louisiana). Ecology of Two Waterfowl Species 41 Calculated from total numbers of individuals observed. 42 Gaston and Nasq TABLE 2 Activi^ budgets by month and station for Bine-winged Teal (BWT) and Green-winged Teal (GWT) wintering at Rockefeller SWR, Louisiana. Activity Station October November December January February March Resting 1 (BWT) 18.2 8.5 2.5 7.3 17.1 50.1 1 (GWT) 43.6 10.7 - 9.4 15.0 34.9 2 (BWT) 15.7 8.2 17.9 28.3 7.2 — 2 (GWT) 14.6 2.9 64.2 33.0 5.1 - 3 (BWT) 13.9 19.5 0 0 - — 3 (GWT) 15.8 10.2 0 82.4 - - Feeding 1 (BWT) 46.0 70.9 70.0* 76.9* 63.7 18.4 1 (GWT) 31.0 71.0 - 71.6 70.7 29.3 2 (BWT) 69.2 67.4 11.9^ 41.7" 673 - 2 (GWT) 75.4 78.1 10.5 51.1 79.6 - 3 (BWT) 68.6 68.3 50.0* 963* - ~ 3 (GWT) 66.3 77.3 0 11.8 - - Locomotion l(BWT) 12.5 15.0 18.8 9.9 9.6 10.9 1 (GWT) 8.2 12.2 - 15.7 63 253 2 (BWT) 9.1 14.5 68.7 26.7 17.0 — 2 (GWT) 4.5 12.1 19.8 10.9 9.8 - 3 (BWT) 2.9 2.7 25.0 0 - - 3 (GWT) 3.0 9.4 0 0 - - Courting 1 (BWT) 2.6 0 0 0.1 1.9 6.0 1 (GWT) 0 0 - 0 1.2 2.8 2 (BWT) 0 0 0 0 0 - 2 (GWT) 0 0 03 2.1 1.2 - 3 (BWT) 0.7 0 0 3.9 - - 3 (GWT) 0.1 0 0 0 - — Preening 1 (BWT) 13.5 3.2 0 4.9 7.4 12.2 1 (GWT) 10.7 4.0 - 2.0 6.3 0.9 2 (BWT) 2.9 9.7 13 33 6.0 - 2 (GWT) 4.9 5.8 53 2.9 33 — 3 (BWT) 10.0 9.6 25.0 0 - - 3 (GWT) 9.1 3.2 99.0 5.9 - - Alert 1 (BWT) 7.2 2.4 8.8 0.9 0.4 1.7 1 (GWT) 6.6 2.1 ~ 1.3 0.3 6.6 2 (BWT) 3.0 0.2 0 0 2.4 - 2 (GWT) 0.6 1.0 0 0.1 1.2 - 3 (BWT) 3.9 0 0 0 - - 3 (GWT) 5.8 0 1.0 0 -- -- a,b,c Percentages for each station denoted by different letters are significantly different (P < 0.05). EC0LCM3Y OF Two Waterfowl Species 43 after morning feeding, presumably to rest elsewhere. Hun- dreds of BWT and GWT were observed resting in densely vegetated salt marsh areas (outside the study area) near Station 3 during midday . Similarly, most resting within the observation areas occurred during midday (Table 3). The greatest differences in activities between the two speciesoccurred during December, whcnGWT spent 64. 1 % of the time resting and BWT spent only 9% of the time resting (Table 1). After December, BWT and GWT loco- motion was most frequent during morning (Table 3). Time spent courting and alert did not differ (P > 0.05) among time blocks in either species. Physical and Biological Factors (jenerally BWT and GWT responded to physical con- ditions in similar manners. In both species, resting and feeding were highly correlated (BWT: a = 747; GWT: jq = 767; P < 0.01) with temperature (+) and light intensity (-). Locomotion was highly correlated with light intensity (-), and preening was highly correlated with temperature (+; Table 4). However, the responses of the two species to physical conditions were not identical. Locomotion was highly correlated with rainfall intensity (+) only in BWT. Preening was most closely correlated with lime of day in BWT, but not so in GWT. Courting by GWT was related (P < 0.0 1) to both temperature (-) and liglii intensity (-), but the factors were not related (P > 0.05) in BWT. The significant relationships among feeding, resting, preening, temperature, and light support the observations of teal resting and preening after morning feeding. The consistent pattern of afternoon preening during early months of the study accounted for the inverse relationship (P < 0.01) between preening and date. Not unexpectedly, courting increased (P < 0.01) during the study period (Table 4) and was most frequent in March (Table 1). Principal components analysis was conducted on a matrix of percent time spent per activity and physical variables including data from all stations and time blocks. The BWT first principal component (PC I) showed load- ings with five variables: water depth, month, temperature, light intensity, and cloud cover (Table 5). In GWT, the first principal component (PC-I) showed high correlation with four variables: month, temperature, light intensity, and cloud cover (Table 5). The correlation with so many variables indicates that the aciiviiies of both species gener- ally varied as a group. PC-II was not highly correlated witli any variables. Thus, mosiseparationof the BWT and GWT activities occurred along a single axis (vertical) when the first two principal component scores were plotted in two dimensions (Figure I). In both species, feeding and resting were separated from other activities, indicating that physi- cal data (especially temperdlure and light iniensiiy, Table 4) were very useful in mterpreting teal feeding and resting behavior. Several factors (cloud cover, time, temperature, and light intensity) also distinguished the activities (hori- zontally), but to a lesser degree. Together PC-I and PC-II accounted for 36.7% of the variance in BWT and 35.4% in GWT. Discussion Feeding values of BWT (65.4%) were similar to those reported during poslbreeding (68.6%, DuBowy, 1985) and incubating (60%, Miller, 1976), and GWT values (55.3%) were similar to those for GWT feeding in natural marshes of Soulh Carolina (56%, Hepp, 1982). However, GWT feeding values were well above averages reported else- where along the Gulf Coast (Texas, < 23%, Quinlan and Baldassarre, 1984; Louisiana, 33.3%, Rave and Baldassarre, 1989). Some of the discrepancy among studies likely resulted from variation in the habitats studied. For example, studies in Texas were conducted in agricultural areas where less foraging may be necessary to meet metabolic needs ( < 23%, (Juinlan and Baldassarre, 1984). Also, inclusion of several habitats in a study may lower the overall values for time spent feeding, assuming the activities vary with habitat. We used only intermediate marshes for our study. Rave and Baldassarre (1989), who also studied GWT on Rockefeller SWR, observed at several habitats, including intermediate marshes where GWT fed 41,3% of the time. Overall, BWT spent more lime feeding (65.4%) than GWT (55.3%). Bcllrose (1980) reported that these two teal species often feed together, although GWT have a greater preference for seeds, and species that feed on seeds may allocate less time to feeding (Paulus, 1984). Gut contents of BWT and GWT collected during the study period indicated they fed on similar diets, primarily of wild seeds and chironomids, and seldom ingested agricultural seeds. Therefore, though the differences between the two species in time spent feeding could have resulted solely from greater preference for seeds by GWT, we suggest that the differences resulted from di.screpancies in selections of habitats as well. The frequency of feeding and locomotion of both species increased with decreasing temperatures (Table 4), probably aresponsetogreaiermetabolic needs (Jorde etal,^ 1983), but perhaps also because food availability decreased from fall to winter. At Rockefeller SWR, chironomid and .seed denaties diminished from fall to winter in ihe three study areas (Gaston and Nasci, 1989). Mean number of chironomids during fall (October to December) was 912 m'^ (range 20 to 2422 m*^), while winter (January and February) means were 365 chironomids m (range, 60 to 760 m*’). Total number of seeds averaged 8917 m-^ during the fall (range, 1240 to 23,660 m'^) and 4075 m*^ (range, 2400 to 6650 m*^) during the winter. 44 Gaston and Nasq TABLE 3 Activity budgets by month and time of day for Blue-wii^ed Teal (BWT) and Green-winged Teal (GWT) wintering at Rockefeller SWR, Louisiana. Activity Time October November December January February March Resting (BWT) Morning 6.2 12.7 0 10.8 15,4 23.9 Midday 26.2 14.7 30.0 6.9 7.9 70,0 Afternoon 15.9 26.6 6.9 17.7 29.7 42.1 Resting (GW’O Morning 11 . 9 ^ 9.0* 15.1* 13.4* 16.7* - Midday 63.3*^ IS - tf * 48.8'* 37. r * 5.6** - Afternoon 15.5* 12.2'* 52.21* 18.8* 21.5* 29.8 Feeding (BWT) MonnDg 76.8* 70.8* 72.0* 71.0* 45.4* 30.8* Midday 54.8*^ 72.1* 30.0^ 66.^* 77.1'* 00 Afternoon 60.9^ 55.3'> 29.^ 62.7“ 53.9* 23.6^* Feeding (GWT) Morning 76.1* 68.6* 50.0* 59.5* 53.4* ~ Midday 25.3*' 48.5^ 24.4'* 43.6 f * 84.2'* - Afternoon 63.6* 67.8* 25.1“ 64.8* 63.3* 26.7 Locomotion (BWT) Morning 8.8 13.1* 14.6* 17.9* 25.9* 23.2* Midday 10.1 2.6'* 40.0^* 16.3* 8.1'* 6.3'* Afterooon 8.7 ll.T'* 515“ 7.9“ 7.6** 12.^ Locomotion (GWT) Morning 4.8 17.6* 21.1 21.0 22.8* - Midday 0.9 25.7'* 21.4 155 5.0^ - Afternoon 7.1 14.3* 19.4 10.0 6.6'* 33.2 Conning (BWT) Morning 0.3 0 0 0 2.6 12.6 Midday 0.8 0 0 4.2 0.6 3.0 Afternoon 0.3 0 0 0.2 0.6 5.4 Courting (GWT) Morning 0 0 0.1 4.0 1.3 - Midday 0.1 0 0.8 0.9 1.3 - Afternoon 0.1 0 0 0.8 0.8 2.7 Preening (BWT) Morning 3.4 2.5 0 0.2 7.9 95 Midday 6.8 10.6 0 1.4 35 11.4 Afternoon 9.3 6.3 6.3 112 7.4 12.9 Preening (GWT) Morning 4.5* 4.7 13.7* 1.8 3.2 - Midday 9.3'* 6.1 4.6“ 1.2 3.8 - Afternoon 8.7*’ 4.5 3.4“ 4.0 7.4 0.9 Alert (BWT) Morning 4.5 0.9 13.4 0.1 2.8 0 Midday 1.2 0 0 4.6 2.9 0.4 Afternoon 4.8 0 5.6 0.3 0.9 3.3 Alert (GWT) Morning 2.6 0 0 0.3 2.6 - Midday 1.1 1.1 0 1.1 0.1 - Afternoon 5.1 1.2 0 15 0.4 6.7 a,b Percentages for each time of day denoted by different letters are significantly different (P < 0.05). Ecology of Two Waterfowl Species 45 TABLE 4 Correlation coefficients of selected physical variables and activities of Blue-winged Teal and Green-winged Teal wintering at Rockefeller SWR, Louisiana. Variable Resting Feeding Blue-winged Teal Locomotion Courting Preening Alert Date 0.073 -0.087* 0.106* 0.139** -0.001 -0.028 Time 0.102* -0.142* -0.047 -0.026 0.172** 0.034 Rainfall -0.045 -0.022 0.238** -0.026 -0.086* 0.053 Wind -0.005 0.007 -0.107* -0.060 0.081* -0.021 Temperature 0.186** -0.193** -0.121** 0.011 0.139** 0.028 Light intensity 0.138** -0.118** -0.141** -0.005 0.085* -0.015 Cloud Cover -0.144** 0.076 0.141** -0.056 -0.047 0.050 Green-winged Teal Variable Resting Feeding Locomotion Courting Preening Alert Date -0.062 -0.055 0.156** 0.241** -0.125** -0.065 Time 0.047 -0.032 -0.097* -0.105* 0.036 0.091* Rainfall 0.004 -0.073 0.059 0.077 0.027 -0.003 Wind -0.059 0.063 -0.085* -0.062 0.005 0.009 Temperature 0.213** -0.127** -0.063 -0.159** 0.155** 0.030 Light intensity 0.393** -0.210** -0.158** -0.136** 0.151** -0.027 Cloud Cover -0.112* 0.002 0.010 0.057 -0.018 0.053 P < 0.05 P < 0.01 Activity budgets of BWT and GWT were similar among the three areas we studied, even though the habitats varied somewhat in water depth and related variables. We had much less habitat diversity for comparisons than in previous studies in Texas (White and James, 1978), Ala- bama (Turnbull and Baldassanre, 1987), or Louisiana (Rave and Baldassarre, 1989) where investigators demonstrated significant differences in activity budgets of waterfowl using widely different habitats. The inverse relationship between feeding and tempera- ture (Table 4) stresses the impact of cold fronts, morning low temperatures, and decreasing temperatures on teal activities. Highest numbers of BWT were observed during October and November, indicating that most of them were on migration flights and later left the area. Thus, since many of the BWT probably arrived in the smdy areas in associa- tion with weather fronts (as suggested by Bellrose, 1980), the relationship between feeding and tcmperauiie was not unexpected. The lack of close correlations between time of day and feeding or resting of the leal (Table 4) emphasizes the loss of pattern in activities after fall. Wc suggest this occurred because metabolic demands increased after De- cember, and because seeds and chironomids, which had been abundant in the study areas during the fall, were more 46 Gaston and Nasq TABLE S Correlations with first and second principal components based on physical variables and activities of Blue-winged Teal and Green-winged Teal wintering in southwestern Louisiana. ! Blue-winged Teal 1 1 1 , Green-winged Teal Physical Variables ! PC-I 1 pc-n 1 1 PC-I PC-fl Water Depth 1 1 j -0.51 -0.33 1 1 1 1 1 -0.27 -0.11 Date j 0.73 0.33 1 1 0.78 0.22 Time j -0.31 0.30 1 1 -0.24 -0.23 Rainfall Intensity j 0.50 0.11 1 1 0.40 0.34 Wind Velocity ! -0.03 0.08 1 1 0.01 -0,31 Temperature j -0.84 0,16 1 1 -0.84 -0.02 Light Intensity j -0.79 0.03 1 1 -0.84 0.08 Cloud Cover 1 0.69 t 1 0.02 1 1 1 0.62 0.04 scarce after December. This scarcity in food probably accounted for the increased time spent in locomotion during late winter and early spring mornings (Table 3). Appar- ently, since food was scarce, the B WT and GWT spent more time in search of feeding areas or spent more time feeding elsewhere. Both teal species fed more during the mornings than during (he afternoons. This pattern was especially evident during the fall (Table 3) when thousands of migrating BWT actively fed in the area. Several hypotheses could be propos^ to explain the pattern of morning feeding. Per- haps some teal were arriving during morning (migrants) or were fasting ovemight.asproposedbyRaveand Baldassarre (1989). Perhaps most of the teal left the study area after morning feeding, and those that remained fed little because they had met their metabolic requirements. Perhaps morn- ing feeding was more efficacious than midday or afternoon feeding because of less predation pressure during morning. Eulissand Harris (1987) hypothesized that disturbance by Northern Harriers (Circus cyaneus) played a major role in diumal activities of GWT. However, Gadwalls (Anas strepera) feeding in the same study area were not disturbed by the presence of Northern Harriers (Gaston and Nasci, 1989). We ob.served that Northern Harriers caused both BWT and GWT in our study areas to take flight regularly, and Northern Harriers were especially active during mid- day and afternoon. Significantly greater morning feeding by these teal is consistent with the hypothesis that predation pressure influenced the time of day that teal fed, and may account for the use of refuge vegetation during resting periods. There were differences in overall time spent feeding, resting, and alert bet ween BWT and GWT, but the daily and monthly patterns inactivities were generally similar and the role of habitat remained unchanged during the study. The study area provided resources for both species, and both apparently used the area for most of their feeding. How- ever, BWT and GWT responded differently to certain environmental and habitat conditions. As food was de- pleted during middle and late winter, many GWT left the shallow intermediate marsh ponds and fed in salt marsh mudflats (see Gaston, 1992). Those BWT and GWT that remained in the study area spent more time foraging for diminishing resources. During our study, many GWT used salt marshes for midday resting and preening. BWT did not use mudflats or salt marsh areas as often, and either u sed the intermediate marshes for all of their activities or emigrated from the study area (i.e., across the Gulf of Mexico). Acknowledgments We are grateful to the personnel at Rockefeller S WR for their support and interest throughout the study, espe- cially T. Joanen, D. Richard, T. Hess, and L. McNease. Rockefeller SWR provided boats, fuel, field supplies, meals, and lodging forthe project We also thank McNeese students J. Pitre, K. Savoie, and L. Vandemiolen for their assistance in field observations, and J. DeRouen, J. Carter, J. Wing, L. Vandermolen, and J. Pitre for their help in the laboratory. This project was funded by the Louisiana Board of Regents* Research and Development Program. Ecology of Two Waterfowl Species 47 BLUE-WINGED TEAL GREEN- WINGED TEAL Figure 1. First (abscissa) and second (ordinate) unrotated e^envectors of a principal components analysis of Blue-winged Teal and Green-winged Teal activities and associated physical variables in southwestern Louisiana. 48 Gaston and Nasq LrreRATURE CriED Baldassaire.G.A. and E.G. Bolen. 1984. Field feeding ecology of waterfowl wintering on the Southern High Plains of Texas. J. WildL Mgmi, 48:63-71. Baldassarre, G.A., S.L. Paulus, A. Tamaisier and R.D. Titman. 1988. Workshop summary: techniques fortiming activity of wintering waterfowl, pp. 181-188. In-. Waterfowl in winter (M.W. Weller, ed,). University of Minnesota Press, Minne- apolis. Bellrose,F.C, 1980. Ducks, Geese, and Swans ofNoith America. Third ed. Staclqx>le Books, Harrisburg, Pennsylvania. 543 pp. DuBowy,PJ. 1985. Feedingecologyandbehaviorof postbreeding Blue-winged Teal and Northern Shovelers. Canadian J. Zoai. 63:1292-1297. Euliss.N.H.andS.W. Harris. 1987. Feeding ecology of Northern Pintails and Gieen-winged Teal wintering in California. J. Wildl.Mgmt, 51:124-732. Gaston, G.R. 1992. Green-winged teal ingest epibenthic meiofauna. Estuaries 15:227-229. Gaston, G.R. and J.C.Nasci. 1989- Diurnal time-activity budgets of nonbreeding Gadwalls {Anas streperd) in Louisiana. Proc. Louisiana Acad. Sci. 52:43-54. Hepp, G.R. 1982. Effects of environmental parameters on the foraging behavior of three species of wintering dabbling ducks (Anatini). Canadians, Zool. 63:289-294. Jorde, D.G,, G.L, Krapu and R.D. Crawford, 1983. Feeding ecology of Mallards wintering in Nebraska. J. WildL Mgmt. 47:1044-1053. Miller, K.J. 1976. Activity patterns, vocalizations, and site selection in nesting Blue-winged Teal. Wilc^owl 27:33- 43. Paulus, S.L. 1982. Feeding ecology ofGadwalls in Louisiana in winter. J. WildL Mgmt. 4611-79. . 1984. Activity budgets of nonbreeding Gadwalls in Louisiana. /. WildL AfgmT. 48:371-380. . 1988. Time-activity budgets of nonbreeding Anatidae: a review, pp. 135-152. In: Waterfowl in winter (M.W. Weller, ed.). University of Minnesota Press, Minneapolis. Quinlan, E.E. and G. A. Baldassarre. 1984. Activity budgets of nonbreeding Green-winged Teal on playa lakes in Texas. J. WildL Mgmt. 48:838-845. Rave, D.P. 1987. Activity budgets of Green-winged Teal wintering in coastal wetlands of Louisiana. Unpub. M.S. Thesis, Auburn University, Auburn, Alabama. 28 pp. Rave, D.P.andG.A. Baldassarre. 1989. Activity budget of green- winged teal wintering in coastal wetlands of Louisiana. J. WiUL Mgmt. 53:753-759. Tamisicr, A. 1976. Diurnal activitie.s of green-winged teal and pintail wintering in Louisiana. Wildfowl 27:19-32, Turnbull, R.E. and G.A. Baldassane. 1987. Activity budgets of Mallaids and American Wigeon wintering in east-central Alabama. Wilson Bull, 99:457-464. White, D.H. and D. James. 1978. Differential use of fresh water environments by wintering waterfowl of coastal Texas. Wilson BulL 90:99-111. Gulf Research Reports Volume 9 | Issue 1 January 1994 Fatty Acid Pattern Differences Among Individuals of Two Estuarine Fishes (Leiostomus xanthurus Sind Mugil cephalus) Julia S. Lytle Gulf Coast Research Laboratory Thomas F. Lytle Gulf Coast Research Laboratory DOI: 10.18785/grr.0901.05 Follow this and additional works at: http:/ / aquila.usm.edu/ gcr Part of the Marine Biology Commons Recommended Citation Lytle; J. S. and T. R Lytle. 1994. Fatty Acid Pattern Differences Among Individuals of Two Estuarine Fishes (Leiostomus xanthurus and Mugil cephalus). Gulf Research Reports 9 (l): 49-56. Retrieved from http://aquila.usm.edu/gcr /vol9/issl/5 This Article is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf and Caribbean Research by an authorized editor of The Aquila Digital Community. For more information, please contact Joshua.Cromwell(®usm.edu. Gtdf Research Reports, Vol. 9. No. 1. 49-56, 1994 Manuscript received January 26, 1993; accepted April 29, 1993 FATTY ACID PATTERN DIFFERENCES AMONG INDIVIDUALS OF TWO ESTUARINE FISHES (LEIOSTOMUS XANTHURUS AND MUGIL CEPHALUS) JULIA S. LYTLE AND THOMAS V. LYTLE Gulf Coast Research Laboratory, P.O. Box 7000, Ocean Springs, Mississippi 39566-7000 ABSTRACT Ten individual fish of two estuarine species, spot {Leiostomm xanthurus) and striped mullet (Mugil cephalus), were analyzed for fatty acids. Fish of similar size were obtained from a single collection to minimize variability due to age, size, location and season. Analysis of variance (ANOVA) of each fatty acid provided statistically similar groups for each acid that existed among individual fish. Fatty acids in the striped mullet provided a greater numb^ of statistically similar groups than those in spot, 'mdicating greater variability among individual striped mullet, which probably reflected a greater diversity in the feeding regime for this species, ANOVA results within classes of fatty acids of both species indicated greater diversity in monounsaturated and polyunsaturated than saturated fatty acids. Eicosapentaenoic acid (EPA) showed more mdividual variability in both species than did docosahexaenoic acid (DHA). Dietary lipids and metabolic needs of the two species are distinct and may be the key factors in explaining individual differences observed in these two fish species. Introduction Natural populations of fishes contain fatty acids and other nutritional components that are highly variable. Stansby (1981) has addressed some sources of variability in fatty acid composition of fish oils within a given species. Other studies have focused on individual species and variations with respect to age (Hayashi and Tal^gi, 1978), season (Ueda, 1976; Hayashi and Takagi, 1977. 1978; Gallagher et ah, 1989), size (Gallagher et al., 1984) and geographical location (Addison et «/., 1973; Whyte and BoutiUier. 1991), but have not addressed variations among individuals of these species. Assessing importance of these variables is dependent upon appraisal of individual vari- ability, since inherent biochemical differences exist from fish to fish even when al! other variables are minimized. It was essential that specimens be carefully selected of two species of coastal Gulf finfishes which differed little in size, development stage, weight or location of catch. This selection permitted specific examination of those fluctua- tions in individual fatty acids that may occur due only to individual differences. By using a non-random selection process for samples, results could not be used to character- ize overall trends in the two species. However, it was felt that results would define some mdividual variations that are uniquely characteristic for these two fishes that would permit informative and useful comparisons to be made and that suggestions for these variability differences would be suitable. Two species of coastal Gulf finfishes, spot and striped mullet, were chosen for assessing mdividual variability because they met several criteria. They represented fishes with differcni feeding regimes, they were collected easily in large numbers from a given area in one catch, and they were numerous enough to permit selection of fish having little variation in size. Additionally, the biology of spot (Gunter, 1945; Dawson, 1958; Hodson etal., 1981; Chest- nut, 1983; Sheridan et al.y 1984) and striped mullet (Odom, 1966; Thompson, 1966) is well established, and both species are found abundantly in local coastal estuaries. Spot is a dominant bottom fish and is considered to feed in schools over sand-mud bottoms on polychaeies, harpacticoid copepods, bivalves and possibly some detritus (Hildebrand and Schroeder, 1928; Darnell, 1958; Hodson et al., 1981). Spot has a fairly small mouth and possesses gill rakers that permit retention of small food particles and prevent ingestion of relatively large food items such as fish, shrimp and crabs (Darnell, 1958; Hodson et al., 1981; Chesmut, 1983; Sheridan et al., 1984). On the other hand, the striped mullet begins its life by eating planktonic plants and animals, but it changes its diet to include a broad range of detritus and plant material as it develops (Moore, 1974). It filler-feeds above organic muds containing microplant material and macroplant detritus (Odum, 1966, 1970), and it is generally considered to be a broad spectrum herbivore. Occasionally, however, car- nivorous feeding has been observed in striped mullet (Bishop and Miglarese, 1978), Fatty acids in marine dietary lipids, whether plant or animal, serve as an energy source for metabolism and provide polyunsaturated fatty acids (PUFA) essential for membrane structure and function. Lipids in muscle tissue of fish generally reflect those fatty acids obtained from the diet. Since these two species have a widely different natural diet, they provide an opportunity to examine mdividual variability within and between species. 49 50 Lytle and Lytle Materials and Methods Collection Striped mullet were collected on January 21, 1988 in the shallow estuary of Biloxi Bay, Mississippi. Spot were collected on April 13, 1988 at Ship Island, a barrier island 15 miles south of Gultjport, Mississippi, in the northeastern Gulf of Mexico. All fish were collected by gill net and maintained on ice until examined. Standard lengths were measured and weights recorded. Fish of approximately the same size were filleted and individual Unplaced separately in polyethylene bags, flushed with Nj, rapidly frozen and stored at *20°C. Average body weight of striped mullet was 230 g (± 12% relative standard deviation: RSD) and average standard length was 22 1 mm (±4.5%RSD). Average body weight of spot was 147 g (±5.2%RSD), and average stan- dard length was 174 mm (±3.5%RSD). Analytical Procedure All solvents used in analysis were HPLC grade or analytical reagent grade. Standards were purchased from NuCheck Prep, Inc. (Elysian, MN). Fillets were homogenized using a Waring blender and 0.5 g aliquots weighed into screw-capped (Teflon-lined) centrifuge tubes (30 ml) and saponified at ambienttemperature withethanolic KOH under Nj using a magnetic stirrer for one hour. Care was exercised in the volumes of saponifying mixtures used to keep the water level, derived from tissue, sufficiently high to prevent trans-esterification. Solvent ratios were those suggested by Nelson (1966). After dilution with distilled water, the neutral fraction was extracted with hexane. The remaining alkaline solution was acidified with 6N HCI. and free fatty acids were extracted with benzene. Benzene aliquots were combined and concentrated using a rotary evaporator. All evaporations were closely monitored to ensure that distillation temperatures did not exceed 25®C. Fatty acids were converted to methyl esters using 7% BF^- MeOH by the method of Metcalfe et al (1966) modified to use ambient temperatures and a one-hour reaction period. Identification of fatty acid methyl esters (FANE) was obtained by capillary gas chromatography (GC) using a Perkin-Elmer model Sigma 2000 gas chromatograph equipped with flame ionization detector and fined with a 30 m X 0.25 mm i.d. fused silica capillary column coated with a 0.25 m film thickness of Dura Bond WAX (J & W Scientific) and operated with a split ratio of 100:1. The carricrgas.He.wasmaintainedatiopsi, Oven temperature was programmed at 90-250‘^C at a linear rate of 4°Aninute. Data was processed using a Perkin-Ehner Sigma 10 data system with quantification of ah compounds based on individual peak area response by GC compared to the internal standard methyl tricosanoate. Quantitative data were corrected for differences in detector responses that were determined through analysis of authentic standards of each reported fatty acid. FAME were tentatively identified by comparison with retention times with those of authentic standards. Verification of identification on select samples was accomplished through gas chromatography mass spec- trometry analysis conducted by National Marine Fisheries Service, Charleston Laboratory. Concentrations of indi- vidual isomers of PUFA were separately tabulated; separate isomers of monounsaturates (e.g. 18:1) were not reported. Sample Protection Several precautions were taken to ensure that no degradation or other alteration of lipids occurred during extraction and saponification. All analytical steps were conducted at ambient temperatures, and samples were constantly flushed with N^ to prevent oxidation. Further, as many steps as possible were conducted in a single extraction mbe to reduce loss and degradation that occurs with sample transfer. All solvents were flushed with N^ immediately before use to remove dissolved and to prevent oxidative degradation. Likewise, samples requiring storage were placed in sample bags which were flushed with N^ before being frozen (-20®C). In addition, the antioxidant butylated hydroxytoluene (BHT) was added in a concentration of 0.005% (w/v) to extraction solvents to prevent oxidative degradation of unsaturaied lipids. Data Analysis One way analysis of variance (ANOVA) with post facto 95% confidence level range test (Statistical Graphics Corporation, 1988) was used to compare individual fatty acids as well as certain parameters d^ved from fatty acid data of individual fish. Similarity groups were established of individuals for each variable which were statistically indistinguishable (p<0.05). In addition, the number of groups was tallied as a further measure of individual variability. Results Figures 1 and 2 depict mean concentration of fatty acids in the samples of individual spot and striped mullet as well as mean % composition of total saturated, monounsaturaied and PUPA. Figures 1 and 2 also include the standard deviations of the means of the ten individual fish and are shown by the dark bars in the graphs. Concen- trations are shown in both wt% of the total fatty acids and Fatty Acid Variations in Two Estuarine Fishes 51 Wt% /jg/g(1000) ■ Meal y SD Figure 1. Leiostomus xanthurus. Distribution of fatty acids in spot. Empty bars to the left represent mean concentrations in wt% of total reported fatty acids of 10 individual fish. Bars to the right depict mean concentrations in pg/g (wet tissue). Gray bars are standard deviations computed on the mean of the 10 mean values for individual fish. t H Mean ^ SD Figure 2. Mugil cephalm. Distribution of fotty acids in striped mullet See caption for Figure 1. 52 Lytle and Lytle in absolute concentrations of pg/g of wet tissue. Absolute concentrations are useful when assessing muscle tissue for nutritive value, particularly for omega-3 (n-3) content, since there is an increased interest in possible health benefits (Lands, 1986), while weight percent concentra- tions are useful in assessing biochemical significance of fatty acid distributions. Tables 1 and 2 contain fatty acid data computed on a wt % basis for fatty acids in muscle tissue from spot and striped mullet, respectively . Also included are sununations and ratios that are helpful in characteriz'mg fatty acid profiles in finfish. Superscripts signify the statistically similar group(s) that each individual fish falls within for ANOVA treatment of each fatty acid or fatty acid param- eter. At the end of each row is the number of groups produced by ANOVA examination of that fatly acid. Individuals of both species varied in fat content. Striped mullet ranged from 1.82-6.38%, while spot ranged from 4.75-8.10%. Fatty Acid Distribution in Spot and Striped Mullet Fatty acid profiles (Figures 1 and 2) were similar from bodi species, particularly in content of saturated fatty acids. Hexadecanoic acid (16:0) was dominant, followed in decreasing order by octadccanoic acid (18:0) and tetradecanoic acid (14:0). The remaining saturated acids constimted less than one percent of the total fatty acids. The predominant monounsaiuraied acid in both fish was 16: 1 . Relative to 16: 1, the contents of 18; 1 and 20: 1 acids were higher in spot than in striped mullet, whether ex- pressed in wt% or pg/g. The two principal PUFA in both fishes were eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3). These n-3 PUFA constitute a higher percentage of the total fatty acids of striped mullet (23 J%) than the spot (13.5%), although in absolute concentration, these PUFA are enriched in spot (4,530 pg/g) relative to striped mullet (3,120 pg/g). A narrow range (2.25 to 2.86%) as well as low concentration of arachidonic acid (AA, 20;4n-6) was found in spot, whereas a wider range and higher concentrations (1.70- 7.00%) were found in striped mullet. Statistical Comparisons of Component Fatty Acids Octadccanoic acid, 18:0, was the second most domi- nant saturated fatty acid in both spot and striped mullet. In spot, no significant difference in values was found among any of the individual fish (i.e. only one similarity group shown in Table 1). On the other hand, there were seven statistically similar groups for 18:0 in striped mullet (Table 2). Minor saturated components, 20:0 and 22:0 in striped mullet (22:0 in spot), showed no significant differ- ences among any of the ten individual fish. Except for 22: 1 in spot, each monounsanirate in both spot and striped mullet showed high diversity among individual fish (four to six similarity groups). Among the PUFA, there were more ANOVA similarity groups for EPA in both spot and striped mullet than for DHA, indicating a greater diversity of EPA than DHA in muscle tissue. In striped mullet, ANOVA treatment of arachidonic (20:4n'6), iinolenic (18:3n-3) and octadecanoic acid (18:0) each produced seven similarity groups, the most diverse fatly acids in either fish. Fatty Acid Classes Figures 1 and 2 indicate that both fishes showed a prevalence of monounsaturates, with spot having 46% monoonsaturated, 23% PUFA and 31% saturated, as com- pared to 40%, 31%, and 29%, respectively, for these fatty acid classes in striped mullet. The saturates for both fishes were less diverse than for either the monounsaturates or PUFA, Likewise, the average value of ANOVA similarity groups for individual saturated fatty acids was less than that found for either of the other fatty acid classes in both spot and striped mullet. Fatty acids occurring in concentrations above 1% of total fatty acids showed a higher degree of individual variability than fatty acids occurring in less than 1% for both spot and striped mullet. The average number of similarity groups for all fatty acids whose concentrations are above 1 % was 3.8 for spot and 5.0 for striped mullet, with 2.5 and 4.3 groups for fatty acids comprising less than 1%. Fatty Acid Parameters Total n-3/n-6 ratio showed little variation among individual spot with ANOVA, separating into only two statistically similar groups. Excluding individual spot No. 1, no di-stinclion occurred among individuals (Table 1). Conversely, the separate sums of n-3 and n-6 fatty acids in spot were separated into five and three similarity groups, respectively. The n-3/n-6 ratio also varied less among individual striped mullet (four groups) than the separate total n-3 and total n-6 fatly acid parameters (five and seven groups, respectively). ANOVA treatment applied to total PUFA in both spot and striped mullet produced five similarity groups. In spot, the unsaturated/saturated and (EPA+DHA)/n-3 parameters produced two and four ANOVA groups, but in striped mullet, it was four and six groups. ANOVA treatment separated the calculated parameters of striped mullet into a largernumberof groups than those of spot, demonstrating the higher degree of individual diversity for component fatty acids in the striped mullet. TABLE 1 Leiostomus xanthurus. Fatty acids in spot Entries are means for three replicate analyses of homogenized muscle tissue from each of 10 individual fish. Values in parentheses are % relative standard deviations. Entries In rows sharing the same supercript letter are not statistically different (p<0.05) and are referred to as similarity groups; group numbers refer to numbers of similarity groups computed for each fatty add. 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In general, plants synthesize all of their fauy acids, and phytoplankton is the basic food in the aquatic field, 'lliose species tlutt feed directly on plant material (phytoplankton and algae) reflect those plant fatty acids, while higher order carnivores accumulate n-3 and n- 6 PUFA contained in their prey which have progressed through the food chain from the original plant source (Sargent. 1976; Sargeniand Whittle. 1981). Red and brown macroalgae found in both the northern and southern hemi- spheres are rich in arachidonic acid and EPA (Jamieson and Reid. 1972). Dunstan ei at. (1988) reported high concen- trations of both EPA and arachidonic acid in finfishes who feed on macroalgae in temperate Australian waters which is consistent with findings of Evans et aL (1986); high levels of both fatty acids were also observed with the striped mulleiin this study. Gibson etal.il 984) reported fatty acids in 24 Australian finfishes. of whichonly the members of the mulletfamily (Mugilidae). whiting, turbot and leatheijacket had higher EPA concentrations dian DHA. A diet contain- ing macroalgae may help explain the elevated levels of both arachidonic acid and EPA in the striped mullet. The pronounced variability in the fatty acid levels in individual striped mullet is most likely due to inclusion of detrital material in the diet, rather than the macroalgae. Organic detrinis in estuarine waters and sediments is com- posed primarily of small amorphous aggregates which may originate from several sources, including benthic microalgae, phytoplankton, microbes and aggregates of dissolved or- ganic carbon excreted or leached from plants and animals as well as salt marsh plants (Boesch and Tamer, 1984). Organic carbon in estuarine sediments is extremely vari- able (Lytle and Lytle, 1985) and would account for the more highly variable diet of striped mullet which is derived in large measure from sedimentary organic matter. Spot feed almost exclusively on invertebrates, prima- rily marine polychaetes and small bivalves. Because of their selective feeding h^its. their diet is more consistent than the diet of striped mullet, particularly those feeding in the same areas. N^'me polychaete worms, a dietary item of spot but not mullet, contain high concentrations of n-3 PUFA with EPA (20:5n-3) concentrations much higher than DHA (22:6n-3) (Lytle and Lytle. 1990a). Similarly. EPA concentrations were higher than DHA concentrations in the individual spot Over 90% of 40 species of Gulf finfishes analyzed in our laboratory (Lytle and Lytle. 1990b) contained higher concentrations of DHA than EPA Spot was one of the exceptions. Saturated fatty acids, both individually and as a class, are conservative, i.e. are relatively constant and in this case demonstrate little fluctu ation in level and distribution among individuals of either spot or striped mullet On the other hand, the monounsaturales, both individually and as a class, exhibited a wider variation among the individual fish for both species. Individual striped mullet showed a considerable range in 16:1 concentrations; again, this could be a result of the broad spectrum of plant and detrital material in the diet The narrower range of concentrations of 16:1 among individual spot may reflect the consistent invertebrate diet. Arachidonic acid, the major n-6 PUFA found in both spot and mullet, was one of the most variable constituents in mullet, producing seven statistically similar groups with four groups in spot. That variation provides strong evidence that this n-6 PUFA is a non-conservative compo- nent in both species. High proportions as well as high variability of arachidonic acid are characteristic of tropi- cal Australian marine fish and shellfish (Gibson, 1983; Sincl^, 1983). However, significant levels have been reported in some northern hemisphere fish (Kinsella et aL, 1977; Gunstone et aL, 1978; Gibson et aL, 1984; Gooch et aL, 1987). In summary, the results of this study, based upon a small but selective group of fish, indicate that each constituent fatty acid as well as fatty acid class varies in individuals within a species of marine fish, even when all environmental and physiological effects are minimized. The extent of individo^ fish variation differs between the two species that were studied, with striped mullet showing much greater variability in fatty acid composition and lipid content than did individual spot. Diet is most likely the primary cause of variations in individual fish, and a more diverse diet probably accounts for the accentuation in individual variability in striped mullet. It is possible that samples collected from other locales or during another season would have shown entirely different trends. This canonly be established from more definitive investigations (m the composition of fish diets under a variety of fish collection conditions. Acknowledgments The authors thank Constancia Ramos for technical assistance and Robin Overstreet for manuscript review. The work was supported by NOAA National Marine Fisheries Service Grant No. NA88AA-H-SK018 and the State of Mississippi. 56 Lytle and Lytle Literature Cited Addison, R.F.,R.G.Ackman and J.Hingley. 1973. Seasonal and local variations in odd-chain fatty acid levels in Nova Scotian rainbow smelt {Osmerus mordax). J. Fish. Res. Board Can. 30: 1 13-1 15, Bishop, J.M. and J,V. Miglaresc. 1978. 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Concentrations of inorganic elements and fatty acids in geographic popula- tions of the spot prawn Pandalus platyceros. Can. J. Fish. Aquat. Sci. 4%:3%2-390. Gulf Research Reports Volume 9 | Issue 1 January 1994 Long-Term Study of Benthic Communities on the Continental Shelf Off Cameron^ Louisiana: A Review of Brine Effects and Hypoxia Gary R. Gaston University of Mississippi Kenneth A. Edds Louisiana Department of Wildlife and Fisheries DOI: 10.18785/grr.0901.06 Follow this and additional works at: http:/ / aquila.usm.edu/ gcr Part of the Marine Biology Commons Recommended Citation Gaston, G. R. and K. A. Edds. 1994. Long-Term Study of Benthic Communities on the Continental Shelf Off Cameron, Louisiana: A Review of Brine Effects and Hypoxia. Gulf Research Reports 9 (l): 57-64. Retrieved from http://aquila.usm.edu/gcr /vol9/issl/6 This Article is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf and Caribbean Research by an authorized editor ofThe Aquila Digital Community. For more information, please contact Joshua.Cromwell^usm.edu. Gulf Research Reports, VoL 9, No. 1, 57-64, 1994 Manuscript received September 22, 1993; accepted October 6, 1993 LONG-TERM STUDY OF BENTHIC COMMUNITIES ON THE CONTINENTAL SHELF OFF CAMERON, LOUISIANA: A REVIEW OF BRINE EFFECTS AND HYPOXIA GARY R. GASTON* AND KENNETH A. EDDS* ^Depariment of Biology, University of Mississippi, University, Mississippi 38677 ^Louisiana Department ofWildl^e and Fisheries, P.O. Box 98000, Baton Rouge, Louisiana 70898 ABSTRACT A long-term data set compiled from our studies and a variety of investigations was analyzed to determine the effects of nine years of discharged brine (concentrated salt water) on benthic organisms surrounding a brine diffuser off Cameron, Louisiana (USA). These investigarions began three months before brine discharge was initiated in 1981. A preliminary summary by Giammona and Darnell (1990) relied on just three years of discharge data and gave misleading reports of brine impacts. Brine effects over the nine years of study were minimal, in part because the fine sediments of the study area were numerically dominated by opportunistic species, mostly estuarine taxa, that showed dramatic population fluctuations both spatially and temporally. These fluctuations in benthic densities were the most salient characteristic of the study area. 'Fhey resulted from summer hypoxia and anoxia in bottom waters, not from brine. Hie hypoxia was related to Mississippi River discharge and subsequent salinity stratification. Hypoxia climmated some taxa and severely reduced populations of most benthic species. The only significant differences between communities near the diffuser and those outside the influeoce of its discharged brine resulted from water-column mixing by the discharged brine, which oxygenated waters around the diffuser and stabilized the salinity of bottom water at the stations near the diffuser. This enhanced benthic diversity around the diffuser and resulted in greater populations during some seasons. Introduction The United States established the Strategic Petroleum Reserve (SPR) following the 1 972 Middle East oil embargo to ensure adequate oil reserves and prevent future petro- leum shortages in the United States. The SH^ design^ and implonented a plan for storage of approximately 1 billion bbl of erode oil in underground caverns hollowed from salt domes along the U.S. Gulf Coast. These caverns were created and subsequently enlarged by high-pressure jets of water blasted against cavern walls, producing up to 80 million liters (1 million bbl) of saturate brine per day that was pumped into the ocean. The purpose of this study was to assess long-term effects of discharged brine on the maciobenthic communi- ties surrounding the diffuser, in water approximately 10 m deep. Giammona and Darnell ( 1990) reported an impact of brine on the benthic communities during 198 1 - 1983, and suggested that the communities might return to background levels once discharge ceased. Gaston et al. (1985) studied colonization near the discharge site during 1982, and concluded that there were no obvious effects of brine on functional feeding groups of benthos. Data were collected on benthic communities surrounding the West Hackbeny brine difftiser during 1981 - 1984 and 1988 - 1989 to test the hypothesis that the maciobenthic-community species com- position and taxon abundance in the area of the diffuser returned to background levels by 1988 - 1989 by comparing benthic community data near the diffuser and at several distances away. Background The U.S. Depaitm^t of Energy (DOE) began dis- charging saturated brine (salt water up to 150 ppt) into the Gulf of Mexico from its SPR West Hackbeny site during May 1981 . There were several SPR sites established along the Louisiana and Texas coasts. West Hackberry was an SPR site located near Hackbeny, Louisiana, just inland of the coastal fishing city of Cameron. Louisiana. Brine was pumped from salt-dome caverns to a holding pond, then to a discharge site in the Gulf of Mexico approximately 1 1.5 km southwest of Calcasieu Pass, near Cameron, Louisiana. The brine entered the Gulf through diffuser heads at the end of a pipeline. The brine was generally comparable to sea water in ionic ratios, except for slightly higher calcium and slightly lower magnesium concenfrations (Jeffrey et al., 1983) . Except for short-term shutdowns, the disclwge was continuous al rates of 40 to 80 million liiers/day until November 1984. Brine flow thereafter occurred irregu- larly, and discharge volume varied widely through 1989. 57 58 Gaston and Edds However, some discharges occurred every year at rates of up to 80 million Uters/day. The area was first studied for an environmental impact report by Science Applications Incorporated (1976). A second study was conducted by the U.S. Etepaitment of Commerce (1981), and a review by Parker e( a!. (1980) included macrobenthic communities surrounding all proposed brine disposal sites in the Gulf of Mexico. A comprehensive study of the local macrobenthic community was conducted by Weston and Gaston (1982), who established the long-term sampling sites during the three months prior to the initiation of brine discharge. The effects of first year brine discharge on the macrobenthic communities were addressed in a multidisciplinary study by Gaston and Weston (1983). Gaston (1985) and Gaston et al. (1985) investigated the trophic structure and recolonizaiion ct^)abililies of macrobenthic organisms in the area of the brine plume. Benthic investigations centered on comparisons of community parameters near the diffuser with those at various distances away, including comparisons with reference sites outside the plume of discharged brine. Gaston and Weston (1983) and Harm et al. (1985a) reported a significantly greater abundance of benthic organisms and greater numbers of species near the diffuser, in paitdue to the elimination of all benthos at sampling sites outside the brine plume during summer hypoxia (Gaston, 1985). Physical mixing of the water colunm by the diffuser apparently disrupted stratification of the water colunm and kept the bottom water and sediments around the diffuser oxygenated. Giammona and Darnell (1990) erroneously referred to this discrepancy in community parameters as a “long-term cumulative effect” of discharge, and suggested that benthic communities around the diffuser might return to background levels once brine discharge ceased. We collecteddala under (he auspices of theLouisianaDepartment of Wildlife and Fisheries (LDWF) during 1988 - 1989. Study Area The study area centered around the West Hackbeiry brine diffuser located on the continental shelf off Cameron, Louisiana (Figure 1). Figure 1. Sampling sites located In a transect across a Strategic Petroleum Reserve (SPR) brine diffuser in the GuirofMexico off Cameron, Louisiana. All stations were located at 10-m water depth. Brine was pumped to the diffuser from the West Hackbeiry SPR facility. Effects of Brine and Hypoxia on Macrobenthos 59 The physical environment of the study area was described by Hann et al. (1985a) and Gaston et al. (1985). Sediments of the area were generally silty sand (50 - 90% silt-clny). Bottom salinity (15 - 32ppt) ranged widely with seasonand tidal cycles, due to the proximity of the Calcasieu, Atchafalaya, and Mississippi Rivers. Temperatures of bottom water varied from winter lows of approximately 12^C to 30*^0 during the summer. Water currents varied with wind speed and direction, but westerly currents dominated, thereby generally moving the brine plume west of the diffuser site (MlOA) and away from the control site (M20) (Gaston and Weston, 1983; Gaston et a/., 1985; Hann et al,, 1985a). Bottom oxygen levels during summer months often dropped below 2 ppm (hypoxia) and periodically reached anoxic conditions (Gaston, 1985). Hypoxia occuired during summer months of most years, although it was periodically disrupted by strong winds or storms. Hypoxia had a dramatic effect on bcnihic communities in the study area, depleting benthic populations, and resulting in domination by relatively small benthos and first-year populations (Gaston, 1985; Gaston et al., 1985). Materials and Methods Six stations (DE, DW, M3, MlOA, M18, and M20) were sampled along an east- west transect across the diffiiser (Figure 1). All stations were at 10 m depth. Samples were taken monthly during 1981 and 1982, and less often thereaftCT. The eastern-most site (Station M20) was located 10 km east of the diffuser, and was outside the eflects of discharge (Gaston and Weston, 1983). StationM18was5km east of the diffuser and rarely within the brine plume. The other four sites were within the plume fairly regularly, depending on their distance from the diffuser, the discharge rate, and prevailing currents. Lower water-column salinity near the diffuser was generally 3 - 8 ppt above ambient due to brine discharge (Hann et al., 1985a). Six replicate samples were taken at each station. Number of replicates necessary to assess the macrobenthic communities of the study area was determined by Gaston and Weston (1983). Samples were taken with a 0.1 m^ SmiUi-McIntyre sediment grab, washed on a 0.5 mm sieve, preserved in buffered formalin in the field, and transferred to 70% ethanol in the laboratory. Most specimens were identified to species. Statistical analyses included a Model I Analysis of Variance (ANOVA, SokalandRohlf, 1981)among stations (when the Bartlett Test indicated homogeneity of variance) using dominant-species densities and total numbers of macrofauna in each replicate as entities. If statistically significant differences were indicaiedby ANOVA, Duncan’s Multiple Range Tests were used to test for statistical diffid- ences ( a = 0.05) among stations. Additional information concerning the study area, its physical regime, and methods of sampling was provided by Gaston and Weston (1983), Gaston (1985), and Gaston et al. (1985). Results and Discussion There were no notable changes in the sedimentary regime of the study area following the initiation of brine discharge (Hann et al., 1985a). Sediments consisted primarily of silty clay to sandy mud, with never more than 48% sand at any site. During the entire study period, the benthic community was characterized by strong numerical dominance of relatively few species that showed dramatic population fluctuations both spatially and temporally. Most noteworthy among the species that numerically dominated prior to brine discharge were deposit-feeding polychaetes (especially Sabellides sp.) and a suspension-feeding t^oronid, Phoronis muelleri (Weston and Gaston, 1982). Weston and Gaston concluded that the dominance by opportunistic species lessened the potential for assessment of impact from brine, even though there was a general homogeneity of the benthic faunal distributions in the area. Populations of oppoitunistic species are characterized by wide fluctuations in densities. During the first year following initiation of brine discharge, the benthic communities showed no changes that could be attributed to brine impact (Weston and Gaston, 1982). The macrobenthic communities of the area were dominated by a rapidly changing suite of young individuals of oppoitunistic species, mostly detritivores (Gaston and Weston, 1983). Suspension-feeding and deposit-feeding polychaetes, such as Afage/ofwr cf. phyllisae, Paraprionospio pinnata, Mediomastus calif omiensis, and Cirratulus cf. filiformis dominated. Gaston and Weston (1983) reported higher numbers of ^)ecies and higher populations of some taxa around the brine diffuser (P < 0.05), believed related to salinity stability near the diffuser. Populations of M. cf. phyllisae were significantly higher around the diffuser during six of the twelve months following initiation of discharge. Mediomastus californiensis populations were also periodically elevated around the diffuser (Station MlOA) during the first year of discharge, but matched background levels thereafter. There were predictioas that discharged brine might be toxic to planktoniclarvacofthe benthos. Indeed, Vecdiione et al, ( 1983) reported reduced numbers of zooplankton and some sublcthal effects on zooplankton near the diffuser. Colonization studies of macrobenthos were subsequently conducted by placing defaunated sediment boxes in areas 60 Gaston and Edds near the diffuser and outside the brine plume (Gaston et al,^ 1983; Gaston et aU, 1985). These studies indicated that most colonization of the sediments resulted from settling meroplanktonic larvae, the macrobenthos in the area of the brine diffuser rapidly colonized, and no significant differ- ences were found between the diffuser and control sites. Perhaps the most salient aspect of the West Hackbeiry SPR diffuser study area was apparent by 1981. Thediffuser was located in an area of the northern Gulf of Mexico continental shelf affected by summer hypoxia which annu- ally eliminated much of the benthic community, thus leading to domination by first-year benthos (Gaston, 1985). The dominant species of the area following hypoxic condi- tions was most commonly the polychacte, Magelona cf. phyllisae, perhaps indicative of its tolerance to high levels of hydrogen sulfide and low dissolved oxyg^ All of the dominant species in the area were opportunistic species. There was often high^ abundance and more species at stations surrounding the difiuser, Staiiofi MlOA CTsibtes 1-2). Gaston (1985) proposed that the differences between com- munities near the diffuser and those outside the brine plume resulted from effects of hypoxia and brine discharge, especially physical mixing of the water column by the diffuser, resulting in breakup of density stratification, and stabilization of the bottom salinity surrounding the diffiiser. Salinity stability in an area with widely fluctuating tidal conditions may lead to higher diversities and colonization by more high-salinity laxa (Gaston e/fl/., 1985). Asaresult, populations of many taxa surrounding the diffuser survived hypoxic events of 1982, and many high-salinity taxa colo- nized the area around the diffuser (Gaston and Weston, 1983; Gaston, 1985; Gaston et aL, 1985). No major impacts to the macrobenthic community from brine discha^e were detected during 1983 - 1984 (Hann et al.^ 1985a). Summer hypoxia again was the primary factor in structuring benthic communities of the area. Hann et aL (1985a) reported that sediments matched predischarge conditions, species diversity was highest at the diffusersite, and greater abundance of macrofaunaoften occurred around the diffuser (Tables 1 - 2). Giammona and Darnell (1990) referred to these diffCTences between dif- fuser and control sites as an “impaa”; however, the term "impact" was misleading, since the effect was a reduced impact from hypoxia, rather than a toxic effect of brine discharge. Giammona and Darnell further hypothe.sized that benthic-community characteristics should return to background levels once brine discharge ended. Abundance of macrobenthos in the study area varied widely during 1981 - 1984 (Tables 1 - 2). During the summer of 1981, abundance was reduced by hypoxia at every station, though the effects were generally lessened around the diffiiser as evidenced by greater number of taxa surviving at Station MlOA (Table 2; Gaston, 1985). Num- bers at one site (M3) reached over 20,000 individuals during June 1981, but dropped below KXX) individuals elsewhere (M18) following the 1981 summer hypoxia. Hypoxia was not as persistent during summer of 1982; abundance that summer was higher at most stations (2(XX)- 30(X) individuals m'^). Hypoxia again eliminated most macrobenihos during summer of 1983 and 1984, and com- munities dropped to below 1000 individuals m*^ at most sites (Hann et al., 1985a). Macrobenthic densities and taxacoUected during sum- mer 1988 - 1989 (Table 3) were similar to those reported soon after die initiation of brine discharge by Gaston and Weston (1983), Hann et aL (1985a), Gaston (1985). and Gaston e/fl/. (1985). Abundance during summer (1988 - 1989) was low; fewer than 1000 individuals m^ occurred at some sites during August 1988. During August 1989, however, densities at all sites exceeded 2(X)0 individuals m'^, perhaps indicative of lessened effects of hypoxia. There were no differences in numbers of taxa or number of individuals (F> 0.05) between diffuser and control stations during 1988; however, there were elevated numbers of individuals around the diffuser during 1989. These 1989 data suggest that the brine diffuser may have enhanced colonization by benthic communities or reduced effects of dissolved oxygen. Opportunistic species, primarily estuarine polychaetes, were numerically dominant throughout the study, and there were no substantial changes in the functional feeding groups during the nine-year period. Suspension-feeding and deposit-feeding polychaetes, especially Magelona cf, phyllisae and Paraprionospio pinnata , dominated through- out the study. The phoronid, Phoronis muellerL and polychaetes, SabellUies sp. and Cirratulus cf. filiformis, that were so abundant during the early 1 980s diminished in mean density to below five individuals at every site by 1989. Other opportunistic polychaetes, Cossura soyeri and Sigambra tentaculatay increased in abundance during the late 1980s. Such shifts among dominant taxa are common in many continental shelf macroinvertebrate communities (reviewed by Gaston, 1987; Parker et fl/., 1980) and was reported in previous investigations of the area (Gaston and Weston, 1983; Gaston, 1985; Gaston et aL, 1985), Large molluscs and other equilibrium (long-lived) species were never collected. Juveniles of the bivalve mollusc, Mulinia lateralis, dominated the taxa at most stations during June 1988 (mean of 476 up to 1066 m'^), but were eliminated by August 1988 and were not abundant during August 1989. This species often was among the numerically dominant taxa during late winter and spring of the early 1980s. but its populations were eliminated or severely reduced during summ^ hypoxia (Gaston and Weston, 1983; Gaston, 1985; Hann et aL, 1985a). Other molluscs that were severely impacted by hypoxia included Epitonium sp., Anachis obesa, Nassarius vibex, N, acutus, and Macoma mitchelli. A similar pattern of colonization TABLE 1 Arerage abimdaoce (n := 6) of macrobenthos (m^) by month and by year. Collections were made at tbe West Hackbenry brine discharge stndy area off Cameron, Louisiana* No collection of data is indicated by a dash* Data from Gaston (1985, 1992), Gaston et at (1985), and Hann et al. (1985). Effects of Brine and Hypoxia on Macrobenthos 61 - ? i § I a K R 2 2 jq 2 2 S: S ^ S w 2 gj 2 g gj 2 ^ 2 2 ^ g 2 S 2 2 2 2 2 2 Q CO *0 I i I i I i§i§si jq CO 2 ^ § 8 S g 5 2 I !S ? !!! a 2 I 5 I S P g r> CO CM Q cn S 15 ^ I S CO ^ 2 fT*i 2 2 S Q S Q S S ■ till 5 § 3 ?? JQ g g 2 S 2 2 ^ « g! 2 S g 8 $ 2 g ?l g ^ S S 3 g 2 g Co 8 2^882 GO Os wo <-1 VO S ^ ^ :s (N to to to CO O 00 CM S S § 2 - § Tf ^ \0 p. wo J 2 o o o o o o o> *-• CM 00 to ^ W Ov OV OO CM wo ^ to wo wo VO g g g g 2 8 i ^ ^ 00 OK o\ o r- ov ^ ^ M CO CM CM ^ I w S2 g Q s 3 s s I ■ I wo wo CO 00 to VO _ ^ VO VO wo 8 « I I I I 1 I I 8 1C 2 2 S S I I i s ! i i I i S 2 g fi S s 2 ® 2 2 I I • 1 I I I I I I I « I § I £ 8 I I I m ^ w 2 8 S n S a S S VO to Os wo 00 CM ^ CM WO ^ VO VO O WO ^ O cq 00 t ) I I I I I I I I I 2 a ^ S 2 00 2 § 00 *2 2 Sv 2 2 2 2 2? 2 So ^ J8 S O 2 VO !C s S 8 S S s § S s i I I I I I S w 8 00 P tn 8 8 9 8 2 2 I I I I I * •a B 4> s X I i 0 U 1 ^4 •§« a eg S .9 CQ .SB .a "* ■S.S s ”'6 ii •g-3 2 ^ Ii aw J ^ rrt f-H Q s a :s I I I Co ^ ^ iR 5 • I I I ^ q: 5 :$ 5 52 ie gj r> ^ oo 't cn m ^ cn S 5S 9 s s s Sg 9 Si $ «o •'t O 00 o § I S g s S I I I eg 5? ^ 5 ^ S S » 52 jq ^ jq 2 S 2 ?q ?R ^ ?q ?q ^ ^ jq I I I vS ^ S ^ 5 Co S CS tn ^ I a I I I I m cn 'O \o cs an I I I I I Effects of Brine and Hypoxia on Macrobenthos 63 TABLE 3 Number of macrobenthic taxa (total in six replicates) and mean densities (m*^ at six stations during sampiing periods in 1988 and 1989. Collections were made at the West Hackberry brine discharge study area off Cameron, Louisiana. Values with s imilar superscript letters are not significantly different (P > 0.05). M3 DW MlOA DE M18 M20 TAXA 58 63 43 57 37 42 June 1988 INDIV. 3372 3898 2065 3543 1660 1962 TAXA 38 28 37 42 48 45 Au&ust 1988 _ INDIV. 977 872 1245 983 1530 1028 August 1989 TAXA 26 32 27 24 25 27 INDIV. 2080* 3945* 520tf’ 2775‘ 4918* 3027“ followed by elimination occurred among the brittle star species, Hemipholis elongata^ which had been very abun- dant during the June 1988 sampling (mean of 460 m*^; up to 606 m"*), but was completely eliminated by August 1989. Conclusions Macrobenthic communities in the study area were not catastrophically impacted by brine discharge as was pre- dicted (Science Applications Incorporated, 1976) before brine discharge began. It appeared that discharged brine had only minor effects on the macrobenthos of the West Hackberry SPR brine diffuser study area, and those effects were mostly enhancements of the benthic communities. Indeed, the only significant differences between commu- nities near the brine diffuser and those outside the influ- ence of its discharged brine resulted from turbulent mixing of the water column by the discharged water, which apparently also affected zooplankton (Vecchione et aL, 1983), decreased effects of hypoxia around the diffuser (Gaston, 1985), and stabilized the lower water-column salinity at the station closest to the diffuser (MlOA) (Gaston et aL, 1985). Similarly, Hann et a/. (1985b) found fewer species and lower abundance of benthos around the Bryan Mound diffuser during 1983 - 1984 andan enhance- ment of the communities at the near-field sites, but few consistent patterns of impacts of brine on the macrobenthos. The hypothesis posed by Giammona and Darnell (1990) that benthic communities might return to back- ground levels after brine discharge ended was erroneous. Benthic communities surrounding the diffuser often matched background (control site) levels during discharge. Physical mixing of the water column and salinity stability due to brine discharge, both enhancement feadires of discharge operations, were the primary features that dis- tinguished impact from control sites. Those distinctions resulted from greater densities of benthos within the affected area of thcdiffuscr. Benthic communities around the diffuser did match background levels, except when those enhancement characteristics were in play. The West Hackberry study area may be unique in many ways, and probably should not be used solely as an example of the potential for brine effects in other areas. Other offshore brine discharge sites were probably not so fortuitously placed. The Bryan Mound SPR site off Freeport, Texas was located in deeper water (21 m depth), had a more diverse and well-established macrobenthic community, and was not affected armually by hypoxia (Hann et al, 1985b). Summer hypoxia in the West Hackberry study area, without question, was the primary factor in structuring benthic conununities. Hypoxia occurred almost annually, and so severely affected the benthic coimnunities of the study area that brine effects were difficult to assess, especially since the brine effects appeared to be minimal. Hypoxia led to wide seasonal variations in populations of macrobenthos in the study area, and confounded year-to- year comparisons of brine effects (Gaston, 1985; Gaston et 1985). Gaston er a/. (1985) used the colonization study to investigate brine effects within the immediate area of the diffuser, and concluded that effects of brine were minor compared to the impact of hypoxia. 64 Gaston and Edds This study emphasized the necessity of long-tenn assessments of potential contaminants on benthic commu- nities. The analyses were especially enhanced by multidisciplinary research projects in the area, manipula- tive studies of brine effects on colonization potential of settling larvae, investigations on macrobenthic functional- feeding groups, and intensified sampling efforts during hypoxic events that helped distinguish the effects of brine and hypoxia. Acknowledgments The authors gratefully acknowledge the help of person- nel at McNeese State University, especially D. Weston, M. Walther, P. Rutledge andL. DeRooen. We are grateful to A. McAllister and C. Lehner at the University of Missis- sippi, personnel at the Louisiana Department of Wildlife and Fisheries, especially J. Hanifen, K. Foote and B. Barrett, and personnel at the U.S. Department of Energy (DOB), especially M. Smith. This project was funded by a grant from DOE to the Louisiana Department of Wildlife and Fisheries (LDWF). LDWF sub^uently funded re- search at McNeese State University and the University of Mississippi. Literature Cited Gaston, G.R. 1985. Effects of hypoxia on macrobenthos of the inner shelf off Cameron, Louisiana, Estuarine. Coastal and Shelf Science 20:603-613. . 1987. Benthic Polychaeta of the Middle Atlantic Bight: feeding and distribution. Marine Ecology-Progress Series 36:251-262. . 1992. Macrobenthic communities on the continental shelf sunounding a brine discharge site off Cameron, Loui- siana. A final report for the Louisiana Department of Wildlife and Fisheries and Department of Energy. May 1992. Gaston, G.R.iP.A.RutiedgeandM.L. Walther. 1985. Theeffccts of hypoxia and brine on recolonization by macrobenthos off Cameron, Louisiana (USA), Contributions in Marine Sci- ence 28:79-93. Gaston, G.R., M. Walther and P. Rutledge. 1983. The effects of brine on recolonization by macrobenthos off Carncron, Louisiana. EOS, T ransactions of the American Geophysical Union 64(52)11064. Gaston, G.R. and D.P. Weston. 1983. Benthos. Chapter 6, 153 pp., fn: L.R. DeRouen, D.M. Casaerly, VJ. Lascara, R.W. Hann, Jr. and C. Giammona (eds.). West Hackbeny Brine Disposal. U.S. Department of Energy Publication. Wash- ington, D.C. Giammona, C.P. and R.M. Darnell. 1990. Divironmental effects of the Strategic Pefioleum Reserve Program on Louisiana continental shelf communities. American Zoologist 30:37- 43. Hann, R.W., Jr., C.P. Giammona and R.E. Randall (eds.). 1 985a. Offshore oceanographic and environmental monitoring ser- vices for the strategic petroleum reserve. Annual report for the West Hackbeny site from November 1983 through November 1984. . 1985b, Offshore oceanographic and environmental monitoring servicca for the strategic petroleum reserve. Annual report for the Bryan Mound site from September 1983 through August 1984. U.S. Department of Energy Publication. Washington, D.C. Jeffrey, L.M., H.E. Murray, J.F. Slowey, J. Beck, C. Webre and G. Grout. 1983. Water and sediment quality. Chapter 5, 77 pp., /n: L.R. DeRouen, DM, Casscrly, VJ. Lascara, R.W. Hann, Jr. and C, Giammona (eds.). West Hackbeny Brine Disposal. U.S. Department of Energy Publication. Wash- ington, D.C. Parker, R.H.,A.L.CroweandL.S.Bohmc. 1980. Describe living and dead benthic (macro-meio-) communities. Volume 1. In: W.B . Jackson and G.M. Fa w (eds.). Biological/chemical survey of Texoma and Capline Sector salt dome brine disposal sites off Louisiana, 1978 - 1979. U.S. Department of Commerce. Washington, D.C. Science Applicationsincorporated. 1976. Environmental impact report for the Strategic Petroleum Reserve Program, West Hackbeny Site. U.S. Federal Energy Administration. Wash- ington, D.C. Sokal, R.R, and F J, Rohlf. 1981. Bio/w/fy (2nd edition). W.H. Freeman and Company, San Francisco. 859 pp. U.S. Department of Commerce. 1981. Brine disposal in the Gulf of Mexico: projected impacts for West Hackbeny based on Bryan Mound experience. Report for the U.S. Department of Energy by the National Oceanographic and Atmospheric Administration. Vecchione, M.,C.M. Lascara, C.L. StubblefieldandW.O. James. 1983. The relationship between brine-diffuser operation and zooplankton distribution. Chapter 9, 125 pp.. In: L.R. DeRouen, D.M. Casserly, V.J. Lascara, R.W. Hann. Jr. and C. Giammona (eds.). West Hackbeny Brine Disposal. U .S. Department of Energy Publicaticm. Washington, D.C. Weston, D.P. and G.R Gaston. 1982. Benthic communities around a brine diffuser. Chapter 5, 126 pp.. In: L.R. DeRouen, et al. (eds.). West Hackbeny Brine Disposal. Community Characterization. U.S. Department of Energy Publication. Washington, D.C. Gulf Research Reports Volume 9 | Issue 1 January 1994 Hepatocellular Neoplasm in a Wild- Caught Sheepshead Minnow (Cyprinodon variegatus) from the Northern Gulf of Mexico Marcos FT. Oliveira Gulf Coast Research Laboratory William E. Hawkins Gulf Coast Research Laboratory , William.Hawkins^usm.edu Robin M. Overstreet Gulf Coast Research Laboratory , robin.overstreet^usm.edu William W Walker Gulf Coast Research Laboratory DOI; 10.18785/grr.0901.07 Follow this and additional works at: http:/ / aquila.usm.edu/ gcr Recommended Citation Oliveira; M. E; W. E. Hawkins, R. M. Overstreet and W. W. Walker. 1994. Hepatocellular Neoplasm in a Wild-Caught Sheepshead Minnow (Cyprinodon variegatus) from the Northern Gulf ofMexico. Gulf Research Reports 9 (l): 65-67. Retrieved from http://aquila.usm.edu/gcr /vol9/issl/7 This Article is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf and Caribbean Research by an authorized editor of The Aquila Digital Community. For more information, please contact Joshua.Cromwell(®usm.edu. Gidf Research Reports^ Vol 9. No. 1, 65-67, 1994 Manuscript received September 13, 1993; accepted October 1, 1993 HEPATOCELLULAR NEOPLASM IN A WILD-CAUGHT SHEEPSHEAD MINNOW {CYPRINODON VARIEGATUS) FROM THE NORTHERN GULF OF MEXICO MARCOS F.T. OLIVEIRA, WILLIAM E. HAWKINS, ROBIN M. OVERSTREET AND WILLIAM W. WALKER Gulf Coost Research Laboratory, P.O. Box 7000, Ocean Springs, Mississippi 39566-7000 Introduction The sheepshead minnow, Cyprinodon variegatus, is a widely distributed small fish species that inhabits estuaries and inshore waters from New England to northern South America, This species has been used extensively in aquatic environmental toxicity and carcinogenicity tests (Couch et ah, 1981; Courtney and Couch, 1984). Hepatic neoplasms have been induced in the sheepshead minnow by exposure to several known chemical carcinogens including diethylnitrosamine (Couch and Courtney, 1987), methylazoxymethanol acetate (Hawldns et al., 1985), and dimethylbenz(a)anthracene (Hawldns et aL, 1991). Because of its widespread distribution, limited home range, andproven sensitivity tocarcinogens, the sheqishead minnow appears to be a good candidate to serve as an in situ monitor of environmental carcmogons and other toxicants in coastal waters, especially those of the Gulf of Mexico and Caribbean Sea. To establish background information on the histopathological lesions in sheepshead minnows taken from the wild, we collected and examined specimens from an offshore site presumed to be free of chemical contamination. The present report concerns a hepatic neoplastic lesion, diagnosed as a hepatocellular adenoma, found in a wild sheepshead minnow. Neoplasms from wild sheepshead minnows or spontaneous neoplasms from laboratory specimens previously have not been reported. Materials and Meitiods The collecting site was Big Lagoon on Horn Island in the Mississippi Sound approximately 18 kilometers from the mainland Horn Island is part of the Gulf Islands National Seashore of the United States Paik Service. About 300 specimens were collected by seining, returned to the laboratory under aeration, anesthetized with tricaine methanesulfonate (TMS), and examined for external lesions. After internal organs were examined for visible lesions, the liver, gUls, and kidney were removed, fixed in Lillie’s solution (Humason, 1972) for 48 hours, washed in running water for 24 hours, stored in 70% ethanol at room temp^atuie, cleared in Shandonxylene substitute (Shandon Inc., Pittsburg, PA) and embedded in paraffin following routine procedures. Sections weiecutonaroiary microtome at 5 to 6 pm thickness and stained with hematoxylin and eosiiL Results and Discussion A neoplastic lesion was found in the liver of a sheepshead minnow collected from Big Lagoon on Horn Island. No other signs of disease were observed. The specimen was a female estimated to be about one year old. In the plane of section in which it was detected, the neoplasm was l.I mm by 0.78 mm and occupied approximately 12% of the liver (Figure 1). Figure 1. Low power micrograph showing hepatocellular neoplasm (HN) occupying a large portion of the liver of a sheepshead minnow. Arrowheads indicate border of lesion with surrounding normal tissue. Hematoxylin and eosin. 65 66 Oliveira ET AL. We diagnosed the lesion as a hq)atoceUular adenoma, but recognize that depending on the pathologist’s particular criteria, a diagnosis of hepatocellular carcinoma might be justified. In our opinion, however, most of the criteria fit the diagnosis of adenoma, Cytologicaily, the lesion was well differentiated. That is, the organization and form of the cells in the lesion resembled those features in surrounding normal tissues (Figure 2). The neoplastic hepatocyies were larger and had larger nuclei than normal hepatocytes. Several mitotic figures were observed in the lesion (Figure 3). At its periphery, the lesion appeared to compress adjacent normal liver. No other neoplastic lesions were found in sections from specimens from that collection site. Epizootics of hepatic neoplasms in fishes arc highly correlated with environmental contamination (Harshbarger and Clark, 1990; Harshbarger e/ 1993). T^ose authors considered an epizootic to be the occurrence of three or more cases of a neoplastic lesion from a specific cell lineage occuiring in a single species from a defined geographic location. Although most neoplasm epizootics have involved large fish species, Vogelbein 990) recently reported epizootic hepatic neoplasia in a large percentage of mummichog {Fundulus heteroditus) from a creosote- contaminated site along the Elizabeth River, VA. This present case of a hepatocellular neoplasm in a sheepshead minnow does not constitute an epizootic. The specimen Figure 2. Higher power micrcigniph showing boundary between neoplastic cells (N) and normal surrounding tissue. Note binucleaie cell (arrowhead) and enlarged nucleus (arrow) in lesion. Hematoxylin and eosln. was collected from a site considered to be uncontaminated by chemicals. The lesion is significant, however, because it is the first report of a hepatic neoplasm in a wild sheepshead minnow and, possibly, is the first repoit of a hepatic neoplasm from a fish from the Gulf of Mexico. The occunence of a single neoplasm-bearing specimen from over 300 examined fish could represent a spontaneous or background rate. Couch and Courtney (1987), however, rcportedno spontaneous liver neoplasms in several thousand sheepshead minnows examined over about 15 years. Nevertheless, the sensitivity of the sheepshead minnow to several carcinogens in laboratory and the widespread geographic distribution of the species suggest that the sheepshead minnow would be a good subject for surveys of aquatic environmental carcinogens in warm southemmarine and estuarine waters. Acknowledgments We wish to thank Dr. Jan Everaarts, The Netherlands Institute for Sea Research, Texel, The Netherlands, and Nate Jordan for assistance in collecting the specimens. We also wish to thank Retha Edwards, Rena Krol, and Robert Allen for their histological assistance. Figure 3. Mitotic figure (arrowhead) in lesion. Hematoxylin and eosln. Hepatic Neoplasm in Sheepshead Minnow 67 Literature Cited Couch, J.A. and L.A. Courtney. 1987. N-nitrosodiethylamine- induced hepatocarcinogenesis in estuarine sheepshead min- now (Cyprinodon variegaius) neoplasms and related lesions compar<^ with mammalian lesions. /. Natl. Cancer Inst. 79:297-321. Couch, J.A., L.A. Courtney and S.S. Foss. 1981. Laboratory evaluation of marine fishes as carcinogen assay subjects. In: C.J. Dawe, J.C. Harshbarger, S. Kondo, T. Sugimura and S. Takayama (eds.). Phyletic Approaches to Cancer. Japan Science Society Press, Toiqro. pp. 125-139. Courtney, L.A, and J. A. Couch. 1984. Usefulness of variegatus and Fundulus grandis in carcinogenicity testing: advantages and special problems. Natl. Cancer Inst. Monogr. 65:83-96. Harshbarger, J.C. and J.B. Clark. 1990. Epizootiology of neoplasms in bony fish of North America. Sci, Tot. Environ. 94:1-32. Harshbarger, J.C., P.M. Spero and NJM. Wolcott. 1993. Neo- plasms in wild fish from the marine ecosystem emphasizing environmental interactions. In: J.A. Couch and J.WFoumie (eds.), Patkobiology of Marine and Estuarine Organisms. CRC Press, Boca R^n, FL. pp. 157-176. Hawkins, W.E, W.W. Walker, T.F. LyUe, J.S. Lyde and R,M. Overstreet. 1991. Studies on the carcinogenic effects of benzo(