: 55.2: ES 8/5/ V.4 NOAA's Estuarine Eutrophication Survey Volume 4: Gulf of Mexico Region November 1997 Office of Ocean Resources Conservation and Assessment National Ocean Service National Oceanic and Atmospheric Administration U.S. Department of Commerce I The National Estuarine Inventory The National Estuarine Inventory (NEI) represents a series of activities conducted by NOAA's Office of Ocean Resources Conservation and Assessment (ORCA) since the early 1980s to define the nation's estuarine resource base and develop a national assessment capability. Over 120 estuaries are included (Appendix 3), representing over 90 percent of the estuarine surface water and freshwater inflow to the coastal regions of the contiguous United States. Each estuary is defined spatially by an estuarine drainage area (EDA) — the land and water area of a watershed that directly affects the estuary. The EDAs provide a framework for organizing information and for conducting analyses between and among systems. To date, ORCA has compiled a broad base of descriptive and analytical information for the NEI. Descriptive topics include physical and hydrologic characteristics, distribution and abundance of selected fishes and inver- tebrates, trends in human population, building permits, coastal recreation, coastal wetlands, classified shellfish growing waters, organic and inorganic pollutants in fish tissues and sediments, point and nonpoint pollution for selected parameters, and pesticide use. Analytical topics include relative susceptibility to nutrient discharges, structure and variability of salinity, habitat suitability modeling, and socioeconomic assessments. For a list of publications or more information about the NEI, contact C. John Klein, Chief, Physical Environ- ments Characterization Branch, at the address below. | NOAA's Estuarine Eutrophication Survey ORCA initiated NOAA's Estuarine Eutrophication Survey in October 1992. The goal is to comprehensively assess the scale and scope of nutrient enrichment and eutrophication in the NEI estuaries (see above) and to provide an information base for formulating a national response that may include future research and monitor- ing. The Survey is based, in part, upon a series of workshops conducted by ORCA in 1991-92 to facilitate the exchange of ideas on eutrophication in U.S. estuaries and to develop recommendations for conducting a nation- wide survey. The survey process involves the systematic acquisition of a consistent and detailed set of qualita- tive data from the existing expert knowledge base (i.e., coastal and estuarine scientists) through a series of surveys, site visits, and regional workshops. The original survey forms were mailed to over 400 experts in 1993. The methods and initial results were evalu- ated in May 1994 by a panel of NOAA, state, and academic experts. The panel recommended that ORCA pro- ceed with a regional approach for completing data collection, including site visits with selected experts to fill data gaps, regional workshops to finalize and reach consensus on the responses to each question, and regional reports on the results. The Gulf of Mexico regional workshop was held in July 1996; this document, Volume 4, is the regional report. It was preceeded by the South Atlantic (Volume 1, September 1996), Mid- Atlantic (Volume 2, March 1997), and North Atlantic (Volume 3, July 1997) reports. A regional report will be completed for the Pacific Coast in the next six months. A national assessment report of the status and health of the nation's estuaries will be developed from the survey results. In addition, an "indica- tor" of ecosystem health will also be published. Both national products will require one or more workshops to discuss and reach consensus on the methods proposed for conducting these analyses. ORCA also expects to recommend a series of follow-up activities that may include additional and/or improved water quality moni- toring, and case studies in specific estuaries for further characterization and analysis. For publications or additional information, contact Suzanne Bricker, Project Manager, at the address below. Strategic Environmental Assessments Division/ORCA 1305 East West Highway, 9th Floor Silver Spring, MD 20910 301/713-3000 http: / /seaserver.nos. noaa.gov NOAA's Estuarine Eutrophication Survey Volume 4: Gulf of Mexico Region Office of Ocean Resources Conservation and Assessment National Ocean Service National Oceanic and Atmospheric Administration Silver Spring, MD 20910 Pennsylvania Stars Universfly Libraries JAN 2 1 1998 Documents Collection U.S. Depository Copy November 1997 This report should be cited as: National Oceanic and Atmospheric Administration (NOAA). 1997. NOAA's Estuarine Eutrophication Survey, Volume 4: Gulf of Mexico Region. Silver Spring, MD: Office of Ocean Resources Conservation and Assessment. 77 pp. Digitized by the Internet Archive in 2012 with funding from LYRASIS Members and Sloan Foundation http://archive.org/details/noaasestuarineOOunit I ORCA Organization The Office of Ocean Resources Conservation and As- sessment (ORCA) is one of four major line offices of the National Oceanic and Atmospheric Administration's (NOAA) National Ocean Service. ORCA provides data, information, and knowledge for decisions that affect the quality of natural resources in the nation's coastal, estuarine, and marine areas. It also manages NOAA's marine pollution programs. ORCA consists of three divisions and a center: the Strategic Environmental Assessments Division (SEA), the Coastal Monitoring and Bioeffects Assessment Divi- sion (CMBAD), the Hazardous Materials Response and Assessment Division (HAZMAT), and the Dam- age Assessment Center (DAC), part of NOAA's Dam- age Assessment and Restoration Program. \\ Project Team Suzanne Bricker, Project Manager Christopher Clement Scot Frew Michelle Harmon Miranda Harris Douglas Pirhalla J Acknowledgments The Project Team would like to thank SEA Division Chief Daniel J. Basta, as well as Charles Alexander and C. John Klein of the SEA Division, for providing di- rection and support throughout the development of the report and the survey process. Our thanks also go to Elaine Knight of South Carolina Sea Grant for lo- gistical support during the Gulf of Mexico Regional Workshop. Finally, we gratefully acknowledge Pam Rubin of the SEA Division for her editorial review. Contents Introduction 1 About this Report 1 The Problem 1 Objectives 1 Methods 2 Next Steps 5 Regional Overview 6 The Setting: Regional Geography 6 About the Results 9 Algal Conditions 9 Chlorophyll a Turbidity Total Suspended Solids Nuisance Algae Toxic Algae Macroalgal Abundance Epiphyte Abundance Nutrients 13 Nitrogen Phosphorus Dissolved Oxygen 16 Anoxia Hypoxia Biological Stress Ecosystem /Community Response 17 Primary Productivity Pelagic Community Benthic Community Submerged Aquatic Vegetation (SAV) References 20 Estuary Summaries 22 Regional Summary. 62 Appendix 1: Participants 63 Appendix 2: Estuary References 67 Appendix 3: NEI Estuaries 77 Introduction This section presents an overview of how the Estuarine Eutrophication Survey is being conducted. It includes a statement of the problem, a summary of the project objectives, and a discussion of the project origins and methods. A diagram illus- trates the project process and a table details the data, being collected. The section closes with a brief description of the remaining tasks. For additional information, please see inside the front cover of this report. | About This Report This report presents the results of ORCA's Estuarine Eutrophication Survey for 37 estuaries of the Gulf of Mexico region of the United States, plus the Missis- sippi/Atchafalaya River Plume. It is the fourth in a series of five regional summaries (South Atlantic (NOAA, 1996), Mid-Atlantic (NOAA, 1997), Gulf of Mexico, North Atlantic (NOAA, 1997) and Pacific Coast). A national report on the overall project results is also planned. The Survey is a component of ORCA's National Estuarine Inventory (NEI) - an ongoing se- ries of activities that provide a better understanding of the nation's estuaries and their attendant resources (see inside front cover). The report is organized into five sections: Introduc- tion, Regional Overview, References, Estuary Summa- ries and Regional Summary. It also includes three ap- pendices. The Introduction provides background in- formation on project objectives, process, and methods. The Regional Overview presents a summary of find- ings for each parameter and includes a regional map as well as maps illustrating the results for selected pa- rameters. Next are the Estuary Summaries — one-page summaries of Survey results for each of the 37 Gulf of Mexico estuaries. Each page includes a narrative sum- mary, a salinity map, a table of key physical and hy- drologic information, and a matrix summary of data results. The Regional Summary displays existing pa- rameter conditions and their spatial coverage across the region. Appendix 1 lists the regional experts who participated in the survey. Appendix 2 presents the references suggested by workshop participants as use- ful background material on the status and trends of nutrient enrichment in Gulf of Mexico estuaries. Ap- pendix 3 presents a complete list of NEI estuaries. I The Problem Between 1960-2010, the U.S. population has increased, and is projected to continue to increase, most signifi- cantly in coastal states (Culliton et al., 1990). This in- flux of people is placing unprecedented stress on the Nation's coasts and estuaries. Ironically, these changes threaten the quality of life that many new coastal resi- dents seek. One of the most prominent barometers of coastal environmental stress is estuarine water qual- ity, particularly with respect to the inputs of nutrients. Coastal and estuarine waters are now among the most heavily fertilized environments in the world (Nixon et al., 1986). Nutrient sources include point (e.g., waste- water treatment plants) and nonpoint (e.g., agricul- ture, lawns, gardens) discharges. These inputs are known to have direct effects on water quality. For ex- ample, in extreme conditions, excess nutrients can stimulate excessive algal blooms that can lead to in- creased metabolism and turbidity, decreased dissolved oxygen, and changes in community structure — a con- dition described by ecologists as eutrophication (Day et al., 1989; Nixon, 1995; NOAA, 1989). Indirect ef- fects can include impacts to commercial fisheries, rec- reation, and even public health (e.g. Boynton et al., 1982; Rabalais and Harper, 1992; Rabalais, 1992; Paerl, 1988; Whitledge and Pulich, 1991; NOAA, 1992; Burkholder et al., 1992; Cooper, 1995; Lowe et al., 1991; Orth and Moore, 1984; Kemp et al., 1983; Stevenson et al., 1993; Burkholder et al., 1992a, Ryther and Dunstan, 1971; Smayda, 1989; Whitledge, 1985; Nixon, 1983). Reports and papers from workshops, panels and com- missions have consistently identified nutrient enrich- ment and eutrophication as increasingly serious prob- lems in U.S. estuaries (National Academy of Science, 1969; Ryther and Dunstan, 1971; Likens, 1972; NOAA, 1991; Frithsen, 1989; Jaworski, 1981; EPA, 1995). These conclusions are based on numerous local and regional investigations into the location and severity of nutri- ent problems, and into the specific causes. However, evaluating this problem on a national scale and for- mulating a meaningful strategy for improvements re- quires a different approach. | Objectives The Estuarine Eutrophication Survey will provide the first comprehensive assessment of the temporal scale, scope, and severity of nutrient enrichment and eutrophication-related phenomena in the Nation's major estuaries. The goal is not necessarily to define one or more estuaries as eutrophic. Rather, it is to sys- tematically and accurately characterize the scale and scope of eutrophication-related water-quality param- eters in over 100 U.S. estuaries. The project has four specific objectives: NOAA's Estuanne Eutmphicatwn Sun 1 mg/ 1, medium > 0.1 < 1 mg/1, low > 0 <0.1 mg/1, or un- known). The ranges were determined from nationwide data and from discussions with eutrophication experts. The thresholds used to classify ranges are designed to distinguish conditions among estuaries on a national basis and may not distinguish among estuaries within a region. Temporal Framework: Existing Conditions and Trends For each parameter, information is requested for ex- isting conditions and recent trends. Existing conditions describe maximum parameter values observed over a typical annual cycle (e.g., normal freshwater inflow, average temperatures, etc.). For instance, for nutrients, ORCA collected information characterizing peak con- centrations observed during the annual cycle such as those associated with the spring runoff and/or turn- over. For chlorophyll a, ORCA collected information on peak concentrations that are typically reached dur- ing a bloom period. Ancillary information is also re- quested to describe the riming and duration of elevated concentrations (or low levels in the case of dissolved oxygen). This information is collected because all re- gions do not show the same periodicity, and, for some estuaries, high concentrations can occur at any time depending upon estuarine conditions. For some parameters, such as nuisance and toxic blooms, there is no standard threshold concentration that causes problems. In these cases, a parameter is considered a problem if it causes a detrimental impact on biological resources. Ancillary descriptive informa- tion is also collected for these parameters (Table 1). NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico PARAMETERS EXISTING CONDITIONS (maximum values observed over a typical annual cyde) TRENDS (1970- 1995) CHLOROPHYLL A -t--. ! V, ' " . TURBIDITY SUSPENDED SOUDS NUISANCE ALGAE TOXIC ALGAE MACROALGAE EPIPHYTES • Surface concentration*: Hypereutrophlc (>60 up. chl-a/1) High (>20, £60 ug chl-a/1) Medium (>5, £20 ug chl-a/1) Low (>0, £5 ug chl-a/1) • Limiting factors to algal Womasa (N, P. SI, light, other) • Spatial coverage1 , Months of occurrence. Frequency of occurrence2 • SecchidlaK depths: ■ Hlgh(<1m), Medium (1 am, £3m), Low(>3m), Blackwater area • Spatial coverage1 , Months of occurrence. Frequency of occurrence2 •Concentrations: Problem (significant Impact upon biological reeourcee) No Problem (no significant Impact) • Months of occurrence, Frequency of occurrence2 • Occurrence Problem (significant Impact upon biological reeourcee) No Problem (no significant Impact) • Dominant species • Event duration (Hours, Days, Weeks, Seasonal, Other) • Months of occurrence, Frequency of occurrence2 • Abundance Problem (significant Impact upon biological resources) No Problem (no significant Impact) • Months of occurrence. Frequency of occurrence2 • Concentrations3'4 • Limiting lectors Contributing factors5 • Concentrations3.4 ■ Contributing factors5 (no trends Information collected) • Event duration3'4 • Frequency of occurrence3.4 • Contributing factors5 ndance3-4 • Contributing factors5 CO LU tc z NITROGEN * Maximum disaoived surface concentration: High (S1 mg/I), Medium (ao.1. <1 mg/I), Low {20, < 0. 1 mg/I) • Spatial coverage1 . Months of occurrence • Concentrations3.4 • Contributing factors5 PHOSPHORUS • Maximum dissolved surface concentration: High (£0.1 mg/1), Medium (iO. 01. <0.1 mg/I). Low (».< 0.01 mgfl) • Spatial coverage1 . Months of occurrence •Concentrations3.4 • Contributing factors5 z HI o Q LU > 5 0mgfl i 2mg/T) BIOL. STRESS (>2mg/l £ Smgfl) • Dissolved oxygen condition Observed No Occurrence • Stratification (degree of Influence): (High. Medium, Low. Not a factor) • Water column depth: (Surface, Bottom, Throughout water column) • Spatial coverage1 , Months of occurrence, Frequency of occurrence2 • Min. avg. monthly bottom dissolved oxygen cone. *4 • Frequency of occurrence3-4 • Event duration3.4 • Spatial coverage3-4 • Contributing factors5 LU tn z o 0. CO LU rr \ z 2 2 O o 2 LU 1- (n 5- 05 O O LU PRIMARY PRODUCTIVITY • Dominant primary producer Pelagic. Benthic Other • Temporal shift • Contributing factors5 PLANKTONIC COMMUNITY • Dominant taxonomlc group (number of ceils): Diatoms, Flagellates, Blue-green algae. Diverse mixture, Other • Temporal shift • Contributing factors5 BENTHIC COMMUNITY • Dominant taxonomlc group (number of organisms): Crustaceans, Molluscs, Annelids, Diverse mixture. Other • Temporal shift ♦ Contributing factors5 SUBMERGED AQUATIC VEG. INTERTIDAL WETLANDS • Spatial coverage1 • Spatial coverage3-4 • Contributing factors5 NOTES (1) SPATIAL COVERAGE (% of salinity zone): High (>50. 5100%), Medium (>25. £50% ), Low (>10. £25%). Very Low (>0. £10% ). No SAV / Wetlands In system (2) FREQUENCY OF OCCURRENCE: Episodic (conditions occur randomly), Periodic (conditions occur annually or predictably), Persistent (conditions occur continually throughout the year) (3) DIRECTION OF CHANGE: Increase, Decrease. No trend (4) MAGNITUDE OF CHANGE: High (>50%. £100%). Medium (>25%. £50%). Low (>0%. £25%) (5) POINT SOURCE(S), NONPOINT SOURCE(S), OTHER Table 1: Project parameters and characteristics. NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico Trends information is requested for characterization of the direction, magnitude, and time period of change for the past 20 to 25 years. In cases where a trend has been observed, ancillary information is requested about the factors influencing the trend. Spatial Framework A consistently applied spatial framework was also re- quired. ORCA's National Estuarine Inventory (NEI) was used (see inside front cover). For the survey, each parameter is characterized for three salinity zones as defined in the NEI (tidal fresh 0-0.5 ppt, mixing 0.5-25 ppt, seawater >25 ppt). Not all zones are present in all NEI estuaries; thus, the NEI model provides a consis- tent basis for comparisons among these highly vari- able estuarine systems. Reliability of Responses Finally, respondents were asked to rank the reliability of their responses for each parameter as either highly certain or speculative inference, reflecting the robust- ness of the data upon which the response is based. This is especially important given that responses are based upon a range of information sources, from statistically tested monitoring data to general observations. The objective is to exploit all available information that can provide insight into the existing and historic condi- tions in each estuary, and to understand its limitations. The survey questions were reviewed by selected ex- perts and then tested and revised prior to initiating the national survey. Salinity maps, based upon the NEI salinity zones, were distributed with the survey questions for orientation. Updates and/or revisions to these maps were made as appropriate. Collecting the Data Over 400 experts and managers agreed to participate in the initial survey. Survey forms were mailed to the experts, who then mailed in their responses. The re- sponse rate was approximately 25 percent with at least one response for 112 of the 129 estuaries being sur- veyed. The initial survey methods and results were evaluated in May 1994 by a panel of NOAA, state, and academic eutrophication experts. The panel recommended that ORCA continue the project and adopt a regional ap- proach for data collection involving site visits to se- lected experts to fill data gaps and revise salinity maps, regional workshops to finalize and reach consensus on the responses to each question (including salinity maps), and regional reports on the results. The revised strategy was implemented in the summer of 1994 start- ing with the 22 estuaries of the Mid- Atlantic region (Figure 1). Estuaries are targeted for site visits based upon the completeness of the data received from the original mailed survey forms. The new information is incor- porated into the project data base and summary ma- terials are then prepared for a regional workshop. Workshop participants are local and regional experts (at least one per estuary representing the group of people with the most extensive knowledge and insight about an estuary). In general, these individuals have either filled out a survey form and /or participated in a site visit. Preparations include sending all regional data to participants prior to the workshop. Participants are also encouraged to bring to the workshop relevant data and reports. At the workshop, at least two work Figure 1: Diagram of process. Survey Design — > National Survey 1992-93 Ji Regional Strategy (to complete data doOecrton) next repton 1993-94 Site Visits Workshops ) N.Atlvrtio, QuHofMajdco MM-Amntic MsiCoatt S.Attantic r National Works hop(s) Next Steps | • national monitoring strategy? ' • research / case i studies? 1 Regional Reports • Indicator Report • National Report 1995-96 1996-98 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico groups are established based upon geography. The survey data and salinity maps for each estuary are then carefully reviewed. ORCA staff facilitate the discus- sions and record the results. At the close of the work- shop, participants are asked to identify "critical" refer- ences such as reports and other publications that de- scribe nutrient enrichment in one or more of the region's estuaries. Workshop results are summarized for each estuary and mailed to workshop participants for review. The data are then compiled for presentation in a regional re- port that is also reviewed by participants prior to pub- lication. The regional process, from site visits to publi- cation of a regional report, takes approximately six months to complete. Some tasks are conducted con- currently. J Next Steps The regional report is in progress for the Pacific Coast (Figure 1). A national assessment report of the status and health of the nation's estuaries will be developed from the survey results. The regional results and final national data base will be available over the Internet through the ORCA SEA Division's World Wide Web site (see inside front cover). Formulating a national re- sponse to estuarine nutrient enrichment, and devel- oping a national "indicator" on coastal ecosystem health, will require one or more workshops to discuss and reach consensus on the methods and products resulting from these analyses. This work is currently scheduled for early 1998. ORCA is funding a series of small contracts with regional experts to provide addi- tional technical support for these tasks. Regional Overview This section presents an overview of the survey results. It begins with a brief introduction to the regional geography and a summary of how tfie results were compiled. Narrative summaries are then presented for each parameter in four subsections: Algal Conditions, Nutrients, Dissolved Oxygen, and Ecosystem/ Community Response. Figures include a regional map showing the location of 37 Gulf of Mexico estuaries and the Mississippi/Atchafalya River Plume, a summary ofprobable- months-of-occurrence by parameter, four maps illustrating existing conditions for selected parameters, and a summary of recent trends by estuary for selected parameters. The Setting: Regional Geography The Gulf of Mexico Region includes 37 estuarine sys- tems plus the Mississippi/Atchafalaya River Plume, encompassing a total water surface area of more than 23, 938 mi2. The entire region is part of the Gulf Coastal Plain, which consists of the Eastern and Western Gulf Plain and the Mississippi Alluvial Plain (Hunt, 1967). The Gulf Coast is characteristic of a gently sloping, lowland environment. Historical periods of coastal flooding and intense sediment deposition have sculpted the Gulf of Mexico shoreline. Today, much of the region is comprised of extensive wetland areas, sandy beaches and barrier islands. For this report, the Gulf of Mexico Region is divided into four distinct subregions: The Western Florida Coast, the Big Bend/ Panhandle Coast, the Mississippi Delta /Louisiana Coast and the Texas Coast. The Western Florida Coast extends from Florida Bay to near Tarpon Springs, Florida. The Big Bend /Panhandle Coast includes all Highlights of Regional Results Note: Tidal fresh = 6%, Mixing = 57%, Seawater = 37% of regional estuarine surface area (1 1,682 mi?) Mississippi/Atchafalya River Plume = 12,256 mi* Hypereutrophic concentrations (>60 ug/1) are observed episodically in four of 37 estuaries and persistently in three estuaries, affecting less than 1% of the regional estuarine area. High concentrations (>20 ug/1) are observed in 18 estuaries, with highest concentrations occurring in spring and winter in 1/3 of the estuaries, in summer in 1/3, and persistently in the remaining 1/3. Concentrations increased in 13 estuaries, decreased in 6, were unchanged in 13, and were unknown in 5 estuaries. Concentrations are high in the mixing zone of Mississippi/Atchafalaya Plume between February and May, with increasing trends. High nitrogen concentrations (>1.0 mg/1) were reported in 18 of 37 estuaries throughout the year, though in some estuaries they are highest during winter months. Concentrations are reported to have increased in 14 estuaries, decreased in 9 estuaries, showed no trend in 7 estuaries, and trends were unknown for 7 estuaries. High concentrations are observed in the mixing zone of the Mississippi/ Atchafalaya Plume, with increasing I trends. Hypoxia is observed periodically June - October in 30 of 37 estuaries and is persistent in Lower Laguna Madre, affecting up to 25% of the regional estuarine area. It is observed in bottom waters in about half the estuaries, and throughout the water column in the other half. Water column stratification was reported to be a major influence on hypoxia. Spatial coverage of hypoxic occurrences have decreased in five estuaries, increased in four, remained the same in 14 estuaries, and was unknown in 13 estuaries. Hypoxia is observed in bottom waters of the Mississippi/Atchafalaya Plume, and the spatial extent has increased. Toxic algal blooms, primarily Gymnodinium spp., are reported to occur in 25 estuaries, mostly on an episodic basis lasting from days to weeks. These blooms typically occur June - October or January - March. There was no trend in the frequency of occurrence of toxic blooms for all or part of 21 estuaries, and trends were unknown for all or parts of 14 estuaries. Frequency of occurrence of these blooms increased in one estuary and decreased in one. Toxic blooms occur in the Mississippi/Atchafalaya Plume, but it is unknown if they pose a problem to biological resources. High phosphorus concentrations (>0.1 mg/1) were observed in 22 estuaries, affecting up to 33% of the regional estuarine area. Concentrations for about half of the estuaries were high all year, and were highest in winter and spring for the rest. Concentrations have increased in 12 estuaries, decreased in 11 estuaries, remained unchanged in 8 estuaries and were unknown in 6 estuaries. Highest concentrations in the mixing zone of the Mississippi/Atchafalaya Plume are medium, with increasing trends. Anoxia is observed periodically in bottom waters of 16 estuaries and throughout the water column in five estuaries, over a maximum of 6% of the regional estuarine area. These events occur during June - October and water column stratification is a significant influence. The spatial coverage of anoxic events has decreased in 4 estuaries, increased in 3 estuaries, remained the same for 13 estuaries and are unknown in 18 estuaries. Anoxia is observed in bottom waters of the Mississippi/ Atchafalaya Plume mixing zone in July and August. Trends in the Plume were unknown. NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico Figure 2: Regional map of the Gulf of Mexico's 37 estuaries and the Mississippi/Atchafalaya River Plume. — NOAA's Esluanne Eutmphication Sunry: Volume 4 - Gulf of Mexico of the Big Bend area of Florida, the Florida Panhandle and Mobile Bay in Alabama. The Mississippi Delta/ Louisiana Coast spans the coastline from the Missis- sippi-Alabama border west to the chenier plain sys- tems of western Louisiana. The Texas Coast subregion stretches from Galveston Bay to Lower Laguna Madre near the U.S. -Mexican border. Western Florida Coast The Western Florida Coast contains eight estuarine systems characterized in this report, encompassing ap- proximately 1,737 mi2 of water surface area (883 mi2 within Florida Bay). The systems located in the south- ernmost reaches of Florida are dominated by man- grove islands, tidal channels and extensive wetlands found along the coastal fringe of the Everglades (Mitsch and Gosselink, 1986). The coastal lowland area of southern Florida is extremely complex and highly affected by tidal action, weather-related events and canal structures. From Cape Romano northward, the shoreline consists of sandy beaches, some rocky ar- eas, swamplands and tidal marshes. In this area, the nearly level coastal plain is covered with sand of vary- ing thickness over a limestone or Karst topography (Beccasio, 1982). Freshwater inflow in the Western Florida Coast is dominated by the Hillsborough, Alafia, Peace and Caloosahatchee river systems. Tidal range is approximately 2 to 3 ft. throughout the sub- region. Big Bend/Panhandle Coast The Big Bend /Panhandle Coast consists of eight es- tuarine systems encompassing approximately 1,588 mi2 of water surface area. The Big Bend area of Florida is composed of a drowned Karst topography and dominated by rugged shoreline, wide, shallow pools and expansive areas of freshwater and tidal marshes. Tidal range in the Big Bend area is approximately 3.5 ft. Freshwater inflow is dominated by the Suwannee River, which is responsible for 15% of the total flow to the west coast of Florida (Beccasio, 1982). Estuaries of the Panhandle Coast consist mainly of smooth, sandy beaches and well developed dune systems. The coast- line is partially enclosed and protected by barrier is- lands. The protected bays typically have mud bottoms and high discharge rates from freshwater sources. Tidal range in the Panhandle Coast is 1.5 to 2.0 ft. The Mississippi Delta/Louisiana Coast The Mississippi Delta/Louisiana Coast consists of 12 estuarine systems encompassing approximately 5,791 mi2 of water surface area, and the Mississippi/ Atchafalaya River Plume (12,256 mi2). The Mississippi Delta area contains seven estuarine systems and sub- systems extending from eastern Mississippi Sound through Atchafalaya Bay. The entire Mississippi Delta area is greatly affected by the Mississippi River and indirectly by the Atchafalaya River (Beccasio, 1982). Nearshore environments in this subregion are typically characterized by shallow, turbid embayments and ex- tensive marsh systems located throughout most estu- aries. The drainage patterns of this subregion have been highly altered by man-made channels. Tidal range within the Mississippi Delta subregion is 1.2 ft. The three remaining chenier plains estuaries to the west (Mermentau, Calcasieu Lake and Sabine Lake) make up the Louisiana Coast portion of this subregion. The coastline is exposed to ocean waters without the pro- tection of barrier islands. The semi-permanent currents, prevailing southeasterly winds and wave-driven cur- rents control circulation patterns in the immediate nearshore areas of these estuaries (Gosselink et al., 1979). Significant inflow from the Mississippi and Atchafalaya rivers and from small coastal rivers reduce nearshore salinities and bring about density gradients near the estuary mouths (see p. 10). Many of the low- lying inland areas surrounding these estuaries contain extensive brackish and freshwater marshes. The marshes are often partitioned by stranded beach ridges, cheniers or by spoil banks produced from dredged materials (Beccasio, 1982). Texas Coast The Texas Coast contains nine estuarine systems en- compassing 2,565 mi2 of water surface area. The sub- region is composed of a shoreline dominated by large bays, lagoons and barrier islands. The estuaries are typically bordered by tidal marshes and mud-sand flats (Orlando et al., 1993). As in the Florida Panhandle es- tuaries, the shallow, lagoonal estuaries of Texas are semi-enclosed by barrier islands. Freshwater discharge is mainly from river systems such as the Trinity, Brazos and Guadelupe. The presence of barrier islands, coupled with low runoff and high evaporation rates along the southern Texas coast, produces hypersaline conditions in these estuaries, especially in the summer months. The lack of a dominant freshwater source can also influence water levels within southern Texas es- tuaries during dry periods (Orlando et al., 1993). Di- rect precipitation contributes significantly to the total freshwater discharge into the estuaries of southern Texas. Tidal range in this subregion is from 0.5 ft. to 1.5 ft. 8 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico About the Results The survey results are organized into four sections: Algal Conditions, Nutrients, Dissolved Oxygen, and Ecosystem Response. Each section contains a general overview followed by more detailed summaries for each parameter. This material is based on the indi- vidual estuary summaries presented later in this re- port. Regional patterns and anomalies are highlighted and existing conditions and trends are reviewed. Prob- able months of occurrence by parameter and by salin- Algal Conditions ity zone are presented in Figure 3. Regional maps sum- marizing existing conditions for selected parameters are presented in Figure 4 (p. 11). A summary of recent trends for all parameters is presented in Figure 5 (pp. 14-15). evant, speculative inferences are noted in the narra- tive below and on the estuary summaries that follow. A highly certain response is based upon temporally and spatially representative data from long-term moni- toring, special studies or literature. A speculative in- ference is based upon either very limited data or gen- eral observations. When respondents could not offer even a speculative inference, the value was recorded as "unknown." Data Reliability As described in the introduction, participants were asked to rank the reliability of their responses as ei- ther highly certain or speculative inference. Over 90 percent of the responses are highly certain. Where rel- Algal conditions were examined in the Gulf of Mexico region by characterizing existing conditions and trends for chlorophyll a, turbidity, suspended solids, nuisance and toxic algae, macroalgal abundance and epiphyte abundance (Table 1). High concentrations and prob- lem conditions are fairly evenly distributed through- out the region for most of the parameters. Extreme conditions generally occur between April and Octo- ber, although in some estuaries extreme conditions occur throughout the year. High or greater chlorophyll a concentrations (>20 ug/1) occur in 18 estuaries. High Figure 3: Probable months of occurrence by parameter and by salinity zone (average). This figure illustrates the probable months, over a typical annual cycle, for which parameters are reported to occur at their maximum value. The black tone represents months where maximum values occur in at least 65 percent of the 37 Gulf of Mexico estuaries for a particular salinity zone. For example, tidal fresh zones occur in 24 estuaries; therefore, a black tone indicates a maximum value was recorded in 16 or more estuaries. Similarly, for the mixing zone, black represents 23 or more estuaries, and for the seawater zone it represents 19 or more estuaries. Gray represents months where maximum values occur in 39 to 64 percent of the estuaries in that salinity zone, and unshaded boxes (white) represent months where maximum values occur between 1 and 38 percent of the estuaries in that zone. "Months-of -occurrence'' data were not collected for Ecosystem/Community Response parameters (i.e., primary productivity, planktonic community, benthic com- munity, SAV, and intertidal wetlands). TIDAL FRESH ZONE 24 MtuartM '■-]'■" OHO at* 1 1 1 1 ■ 1 1 1 1 1 Turbidity taparitd Sotkta 1 1 1 1 1 1 NukUM Alga* 1 1 1 1 1 1 1 1 1 1 Toxic Algaa 1 1 1 1 M»c66% or txj ««uaUttM in tMCh ront) ti— — n 39% and 94% of r* i □ ttttttt t« and m of tn ■ NOAA's Estuanne Eutrophication Survey: Volume 4 - Gulf of Mexico turbidity (secchi disk depths <1 m) occurs in 33 estu- aries and suspended solids are problematic in 12 estu- aries. Nuisance algae causes biological resource im- pacts in 22 estuaries, and toxic algae causes biological resource impacts in 25 estuaries. Macroalgal and epi- phyte abundance each cause resource impacts in 10 estuaries. Chlorophyll a Medium or greater concentrations (>5 Hg/1) were re- ported in 34 estuaries, occurring across a maximum of 65 percent of the regional estuarine surface area. However, as chlorophyll a concentrations increase across a gradient of medium to hypereutrophic, the number of affected estuaries and the amount of re- gional surface area decreases. That is, high or greater concentrations (>20 (ig/1) occur in 18 estuaries across a maximum of 22 percent of the regional estuarine sur- face area, and hypereutrophic concentrations occur in seven estuaries over only four percent of the regional surface area. Except for a very small area in Pensacola Bay, the Big Bend /Panhandle Coast is the only subre- gion in which high or greater concentrations do not typically occur. High or greater concentrations were reported to occur over a larger area (64 percent) of the regional tidal fresh zone surface area than concentra- tions in the mixing and seawater zones (20 and 19 per- cent, respectively). High or greater concentrations gen- erally occur periodically for one or more months be- tween March and October. In Barataria Bay, San Anto- nio Bay, Aransas Bay and the Laguna Madre system, the concentrations occur throughout the year. Concen- trations reported for four estuaries are based in part on speculative inference. During the period ca. 1970-1995, chlorophyll a concen- trations decreased in six estuaries and increased in 13 estuaries. Concentrations remained unchanged in 13 estuaries and were unknown in five. Concentrations increased and decreased simultaneously in different parts of the seawater zone of Florida Bay from 1990 to Mississippi and Atchafalaya River Plume The Mississippi and Atchafalaya River Plume is a 12,256 mi2 zone located west of the confluence of the Missis- sippi and Atchafalaya Rivers and the Gulf of Mexico (Rabalais et al., 1992). The plume is included in this report because it has many estuarine characteristics; is a major influ- ence on the water quality of pro- ductive estuaries lying to the west (e.g., Barataria, Terrebonne, Timbalier, Atch- afalaya, Vermilion Bays); and 28% of the total U.S. annual commercial fishery yield is har- vested there. The watershed for the Missis- sippi and Atchafalaya Rivers encompasses over one million mi2 (approximately 40% of the area of the contiguous 48 states), and has an average annual in- flow of approximately 700,000 cfs, making it the largest single source of freshwater to the Loui- siana continental shelf. This in- flow is a major feature of the continental shelf and can be traced as far west as Port Aransas on the South Texas coast (Rabalais et al., 1996). This is also the single largest source of nutrients to the shelf, thus, nutrient-associated water quality degradation in the plume is a major concern. Nutrient-enhanced productivity on the continental shelf has caused a spatially extensive and seasonally prevalent zone of hy- poxia, and to a lesser degree, an- oxia, that is observed every sum- mer in bottom waters off the coast of Louisiana and Texas (Rabalais et al., 1992). The loadings from the Mississippi and Atchafalaya Riv- ers are the source of this wide- spread hypoxia (Turner and Rabalais, 1994). Evidence from sediment cores and recent sam- pling surveys shows that the fre- quency, duration and spatial cov- erage of these annual hypoxic events have increased during the past century (Eadie et al, 1992; Rabalais et al., 1996). The increase is attributed to land use changes in the watershed since 1900 that have resulted in significant in- creases in nitrogen and phos- phorus inputs and declines in silica (Turner and Rabalais, 1994). These changes in nutrient ratios have resulted in changes in the composition of phytoplanton species; for ex- ample, toxic and noxious forms are now present that were pre- viously either absent or less dominant (Rabalais et al., 1996). The increase ofthese toxic forms has obvious implications for hu- man health and fisheries. In ad- dition, as the less preferentially grazed phytoplankton become more dominant, the food chain stucture may be altered (Turner and Rabalais, 1991). Please note: Conditions in the Plume are not discussed in the general text. For more informa- tion on algal conditions, nutri- ents, dissolved oxygen and eco- system/community responses, see the Mississippi/ Atchafalaya River Plume estuary summary on p. 49. 10 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico 11 NOAA's Estuanne Eutrvphication Survey: Volume 4 - Gulf of Mexico 1996. The trends reported are based in part on specu- lative inference for 10 estuaries. Turbidity High turbidity concentrations (secchi disk depths <1 m) were reported to occur in 32 estuaries covering 68 percent of the regional estuarine surface area. Although high concentrations occur in all subregions, the Big Bend /Panhandle Coast area is characterized more by moderate turbidity conditions and naturally occurring blackwater areas. High concentrations occur in up to 96 percent of the surface area of the tidal fresh zone, 79 percent of the mixing zone, and 46 percent of the seawater zone. Medium or greater concentrations (secchi disk depths <3 m) were reported to occur in 36 estuaries with a spatial extent of up to 96 percent of the tidal fresh zone, 88 percent of the mixing zone, and 84 percent of the seawater zone. Medium and high concentrations occur persistently throughout the year in 29 estuaries, during the summer in four estuaries and during the winter in three. During the period 1970-1995, turbidity concentrations were reported to have decreased in nine estuaries, in- creased in eight estuaries, and remained unchanged in 17 estuaries. Trends were unknown for three estu- aries and were based in part on speculative inference in five estuaries (Figure 5). Total Suspended Solids Suspended solids were reported as impacting biologi- cal resources (e.g., submerged aquatic vegetation, fil- ter feeders, etc.) in 12 estuaries. The impacts are re- ported to occur all year in four estuaries, periodically from May through September in five estuaries and during the winter months in three estuaries. Informa- tion reported was based in part on speculative infer- ence for four estuaries. Trends information was not collected for suspended solids. Nuisance Algae Biological resource impacts due to nuisance algae were reported to occur in 22 estuaries throughout the Gulf of Mexico region. In the Western Florida Coast sub re- gion, impacts from Synechococcus spp., Anabaena spp., Chlorococcus minutus, Microcystis aeruginosa and other unidentified blue-green algae and dinoflagellate spe- cies occur fromApril to November. Events are weeks to seasonal in duration. In the Panhandle Coast, nui- sance algal events are mostly episodic, have a dura- tion of days, and occur between July and September. In Choctawhatchee Bay, however, the events occur pe- riodically and are seasonal in duration. Species iden- tified as impacting resources in the Panhandle Coast are Anacystis spp., Anabaena spp., Cladophora spp., Enteromorpha spp., Chlamydomonas spp. and Apfmnocapsa spp. In the Mississippi Delta/ Louisiana Coast subregion, events are mostly episodic and last from days in some estuaries to seasons in others. Im- pacts generally occur between May and September; in Mississippi Sound however, nuisance algae impacts may also occur from January to February, and in Barataria Bay, blue-green algal blooms occur persis- tently throughout the year. Species identified as im- pacting resources in the Mississippi Delta/Louisiana Coast subregion are Exuviella spp., Prorocentrum mini- mum, Alexandrium spp., Anabaena circinalis, Katodinium rotundum, Microcystis aeruginosa, Anacystis spp., Gymnodinium sanguinium and other unidentified di- noflagellates. Nuisance algae impacts along the Texas coast occur mostly episodically between May and Sep- tember. Event durations vary from days to weeks to months. In Upper Laguna Madre, Baffin Bay and part of Lower Laguna Madre, Aureoumbra lagunensis im- pacts occur throughout the year. Other species identi- fied as impacting resources are Noctiluca spp. and uni- dentified blue-green algae and flagellates. The reported information on nuisance algae was based on specula- tive inference for five estuaries. During the period 1970-1995, the frequency and/or duration of event occurrences increased, mostly at a high magnitude of change in eight estuaries. Decreases of low to high magnitude occurred in Tampa Bay and Galveston Bay. Conditions remained unchanged in 18 estuaries, and were unknown in 10 estuaries. Trends information was based on speculative inference for seven estuaries (Figure 5). Toxic Algae Biological resource impacts due to toxic species were reported to occur in 25 estuaries throughout the Gulf of Mexico region. The impacts occur episodically in 18 of the estuaries and periodically in parts of Florida Bay, Choctawhatchee Bay and Perdido Bay. In Lake Borgne, Brazos River, Matagorda Bay and San Anto- nio Bay, the toxic algae impacts were reported to have occurred one time only. Toxic algal events in the Gulf of Mexico estuaries are variable in duration, lasting days to weeks in some estuaries and months to sea- sonally in others. Impacts generally occur between June and October, except in Florida Bay and Apalachee Bay, where impacts occur between January and March. Additionally, in five estuaries, toxic algal events are unpredictable and may occur during any month of the year. The toxic species Gymnodinium breve was associ- ated with biological resource impacts in 16 of the 21 impacted estuaries. Other toxic species reported as causing resource impacts are Alexandrium monilata, Anabaena circinalis, Anacystis spp. and Prorocentrum 12 NOAA's Estuarine Eutrophication Survey: Volume 4 ■ Gulf of Mexico minimum. Toxic algae also occur in some Gulf estuar- ies, such as Atchafalaya/ Vermilion Bays, but the im- pacts to biological resources are unknown. Toxic al- gae information was based on speculative inference for six estuaries. During the period 1970-1995, increases in the dura- tion and frequency of toxic algal events were reported to occur in Apalachicola Bay. In Tampa Bay, the dura- tion and frequency of toxic algal events decreased during the years 1980 to 1995. Conditions were re- ported as unchanged in 21 estuaries and were un- known in 14 estuaries. Trends information was based on speculative inference for six estuaries (Figure 5). Macroalgal Abundance Biological resource impacts due to macroalgae were reported to occur periodically between April and Oc- tober in nine estuaries. In Sarasota Bay and San Anto- nio Bay, impacts occur in February, and in parts of Florida Bay, impacts occur persistently throughout the year. Also, impacts were speculated to occur episodi- cally during May in the Suwannee River mixing zone. Macroalgal conditions were unknown in two estuar- ies. Reported macroalgal abundance information was based in part on speculative inference for two estuar- ies. During the period 1970-1995, macroalgal abundance impacts increased in Florida Bay, Lake Pontchartrain, San Antonio Bay, Aransas Bay and Corpus Christi Bay. Declines of a high magnitude occurred in Tampa Bay and were speculated to have occurred in Sarasota Bay. Conditions remained unchanged in 19 estuaries and were unknown in 12 estuaries. Reported macroalgal abundance trends were based in part on speculative inference for four estuaries (Figure 5). Epiphyte Abundance Biological resource impacts due to epiphytes were re- ported to occur in 10 estuaries. Conditions occur throughout the year in four estuaries and periodically between April and October in six estuaries. Epiphyte abundance conditions are unknown in four estuaries. Reported epiphyte abundance information was based in part on speculative inference for four estuaries. Epiphyte abundance impacts increased (ca. 1970-1995) in Florida Bay, Lake Pontchartrain, San Antonio Bay, Aransas Bay and Corpus Christi Bay. No decreases in epiphyte abundance were reported, and conditions re- mained unchanged in 20 estuaries. Epiphyte abun- dance was unknown for 13 estuaries and based in part on speculative inference for three estuaries (Figure 5). Nutrients Nutrient concentrations were characterized by collect- ing information on existing conditions (maximum val- ues observed over a typical annual cycle) and trends. The intent was to collect information for total dissolved nitrogen and phosphorus, since it is the dissolved forms that are most available for uptake by phy- toplankton. Unless specifically noted, information for nutrients presented in this report refers to total dis- solved nitrogen (TDN) and phosphorus (TDP), includ- ing the inorganic and organic forms. The individual estuary pages should be consulted for more in-depth summaries of reported nutrient concentrations. Results indicate that medium and high concentrations of both nitrogen and phosphorus are pervasive in the Gulf of Mexico region. High concentrations of phos- phorus (> 0.1 mg/1) were reported in 22 estuaries. For 10 estuaries, concentrations were high all year. High concentrations of nitrogen (>1.0 mg/1) occurred in 18 estuaries; in eight estuaries, concentrations were high all year. Medium concentrations of nitrogen (>0.1, <1.0 mg/1) occurred in 29 estuaries; persistently in 12. Me- dium phosphorus concentrations (> 0.01, <0.1 mg/1) were observed in 36 estuaries, occurring throughout the year in 11 estuaries. Nitrogen High nitrogen concentrations have been observed in 18 of the 37 estuaries in up to 78 percent of the regional tidal fresh zones, 22 percent of the mixing zone, and up to 5 percent of the seawater zone. High nitrogen concentrations are observed in up to 19 percent of the regional estuarine area mostly during the summer and fall, but for eight estuaries concentrations are persis- tently high. Medium concentrations of nitrogen were reported in 29 estuaries in up to seven percent of the region tidal fresh zone, up to 50 percent of the mixing zone and up to 21 percent of the seawater zone. Between 1970 and 1995, nitrogen concentrations have increased in 13 estuaries and decreased in nine estu- aries. For eight estuaries concentrations did not change, and for seven estuaries trends were unknown. Responses were based on speculative inference for six estuaries. Phosphorus High phosphorus concentrations were reported in 22 of the 37 estuaries in up to 78 percent of the regional tidal fresh zone, up to 44 percent of the regional mix- ing zone and up to 11 percent of the regional seawater zone. High concentrations were observed in up to 33 13 blOAA's Estuanne Eutrophication Survey: Volume 4 - Gulf of Mexico Figure 5: Recent trends (1970 - present) for selected parameters by estuary by salinity zone (T, tidal fresh; M, mixing; S, seawater). All salinity zones are not present in all estuaries. Most of the 2,016 possible values are no trend (940). There are 154 decreasing trends, 155 increasing trends, and 737 unknowns. The remaining 30 responses display shifts in the primary Chlrophyfl a iwi • t t • 7 4 444 • • • •4 • • • t ' 7 ♦ - • • • 7 7 17 i •♦■ Turbidity Nuisance otraOon Algae frequency • t I 4 444 ... ••4 • !• e 4 7 '4 4 t e • • • 7 7 7 • It 7 44 • 7 7 t 7 7 7 • t ? 4h° 7 7 7 • t 7 7 7 • e Toxic duration Algae frvquancy t t 7 7 7 7 7 7 t t 7 7 7 7 7 7 Macroelgal • t 7 7 7 7 • 7 • 4 444 • • 7 7 • • • 7 7 7 7 7 Epiphyte Abundance Nitrogen • t 7 7 7 7 . 7 • ? 7 7 • • • 7 7 • • • 7 7 7 7 7 1 1 t * • • • t «• 4 j« « ^r 4 t ' »|t ' t ' 7 7 7 7 7 Phosphorus 4 • • • III 1 4 444 • • •- •4 • « t ' 'it ' l t|« » 7 7 7 4 ' 8ottomD.O. 11 • ' • * * 7 7 • ' • • tt • T 7 7 t 4 7 4 . 4tt Anoxia duration BUBJHWPy •pan/ oovarapa ? ? 7 7 7 e- •■ 444 7 7 7 4 7 7 7 7 7 t » i 7 ? ? 7 7 7 •- •■ '4- 7 7 7 4 7 7 7 7 7 7 7 7 7 7 7 7 7 7 ? ? 7 7 7 • • 444 T 7 7 4 7 7 7 7 • • • t ' ' 7 • • • e 7 Hypoxia duration mtquancy KMtmlcowrmgt » t > t 7 7 7 •' •' 444 '4« 7 7 7 7 4 4 7 7 7 7 7 t ' ' 7 7 e • • • 7 7 7 ? e- •■ 7 7 t 7 7 7 7 7 7 7 7 7 7 7 7 7 e- •• 444 7 7 17 •k t 7 7 7 7 7 e • • t 7 e • • a 7 Biological duTaSon Stress tmqutncy •pauaf seiBaaei 7 7 7 ar •■ 444 7 7 7 4 ■ • 7 7 7 7 t 7 ' - 7 • • • • I 7 7 7 •• •• '4« iffli 7 7 7 4 t 7 7 7 7 7 7 ? 7 7 7 7 7 7 7 •• •• 7 4 t ? 7 7 7 • e t 7 e • • e 7 Primary Productivity Plankton • © 3 • • • ? •■ ? * 7 • • • • 7 Q ®Q>© a e e e 7 • Q 7 7© • • • • • i* 1 7 7 l • •' 7 • •' B«nthtc • I in ? 7 7 • ' • • • 4 t 'tt •■ •- • • t f 1 7 '4 ' • 44 •' • 4 • • 7 T4 ffli - no tfwid of enR 4 t (T\ ■ M from banrhte to paiagfc (£) - ah*) trom annatda to <*vat*a (7) - aMI to amargant and paiagtc (7) ■ ahtft from <*var*a lo annaada (J) ■ ahifl from dkaraa lo diatom, and tlaoalataa (t) ■ ahfl from datoma and blua-ontan algaa to 14 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico productivity, planktonic community or benthic community. 151 values are based on speculative inferences. For a more complete listing of the trends parameters, see Table 1 on page 3 7 ? ? I ? 7 t * f 4 7 • 7 • 7 • 7 7 7 7 7 7 7 ? 7 7 • • • • ? 7 ? 7 ft • 7 t ' t ' ? ? t 7 7 7 7 f|f t • ? »|t • • '44 41 • i • • t t t t W Chlorophyll a Turbidity ( 00O0#* 0 BkU 1 ■ ) duration Nuisance Algae hwqumvy 44 7 7 7 7 ? 7 7 7 7 7 7 7 • • t 444 >4- • • 7 • • 7 * t t • • • • • 7 • T t t t • • t t 7 7 7 • •|t '4» • • 7 • ' •' •' • • • • • • t • t t • t 7 7 durmbon Toxic Algae frequency Macroalgal Abundance 7 • 7 7 7 7 7 7 7 7 7 7 7 7 j i , ? 7 • • • • ? ? 7 7 1 ! ? • 7 7 ' • • • •jt •■ •t • >|t • • • • 7 7 7 1 • 7 1 1 ' • 7 * : 7 • • • .f .• * t • »|f • • • • Epiphyte Abundance ? ? ? 7 tjf 7 • 7 1 • 7 7 •1 7 • • tit t tt t » • 44 •4 444 • • 7 ' 4 • t • • 44 7 • • • 4 t • Nitrogen • • • • f « • • • t * 4 • • 44 4 44 • • 7 ' • t ttt • t 't » t 4 t t Phosphorus 7 7 7 7 7 7 4- ti« 4 ' 7 7 • • • jt t • tt t Bottom D.O. 7 • ' • • 4* 4 4 • • • 7 • • • 7 7 7 duration Anoxia Iraquancy apabaJ covamga duration Hypoxia myamV covaraga 7 7 • 7 • ' • ! • 7 7 7 t * 7 1 7 • 7 • 4* 4 4 • • • ? • • • 7 7 7 ? 7 • 7 • ' • • 7 7 7 t« 7 i 7 • t|« 11- 4 4 • • • ! 1 • • • 7 7 7 7 7 • ? • ' • i • | 7 ] 7 7 tl- th • t|4 M9 4 4- • • • 7 • • • 7 7 7 4 • t ? 7 7 7 7 • 7 • 7 • 7 •" • • 7 7 7 th tU • >4 4» 4 4' • • • 7 • • 7 • • • • 7 7 7 4 • t 7 •' 7 •' • • • • 7 7 7 7 7 7 t • t • t > t » • • t4 t • 4- 4 4j« • • 7 7 7 4 • 4 • 4 41 • • • 7 • • • 7 7 7 4 • duration Biological Stress Iraquancy aoaaaJ oovtmga 7 • 7 •' • • 7 7 7 t • t » • 7 • 4 • 4 4* • • 7 • • • 7 7 7 l|« 7 7 • 7 •* • • 7 7 7 t • t ' • t « 4 • 4 4 • • • 7 • • • 7 7 • 4 • 7 • • • • • t 7 • © • 7 • : • 7 © ® © » 8 8 • ® © Primary Productivity Plankton Community Benthic Community 7 7 © 7 7 • • 7 7 • • • • • 7 • • •' • 7 7 ? 7 7 7 7 © © 8 © 7 • 4 •4 • • tt t t » 4 t 7 t «-. ~~.SAV (j) - ftNft from b*u*-jjne»n alga* to diatom* (^ - tNTl from wrttervte to paiagic and wvttands (0\ - thtft from pKj* JrWB aiga« to dKart* i , 0 1 • traTI tram amarpant to patogic and banthic (u) - aNR from patagic lo b*nc bta p#*ag c (^) - aNft from aHlnupuUa to oVaraa , , 5s. • thft from barrihic lo pa*ag«cSA V (14) - ahtfl from oVaraa lo Auraourrtjra ® • 15 NOAA's Estuarme Eutrophicatwn Survey: Volume 4 - Gulf of Mexico percent of the regional esruarine area during the sum- mer and fall for most estuaries, but persistently in 10 estuaries. Medium phosphorus concentrations were reported for 22 estuaries in up to six percent of the tidal fresh area, up to 41 percent of the regional mix- ing zone and up to 22 percent of the regional seawater zone. Between 1970 and 1995, phosphorus concentrations decreased in 11 estuaries and increased in 11 estuar- ies. Phosphorus concentrations remained the same in nine estuaries; trends were unknown in six estuaries. For six estuaries, responses were based on specula- tive inference (Figure 5). Dissolved Oxygen Dissolved oxygen conditions were characterized by collecting information about existing conditions and trends for anoxia (0 mg/1), hypoxia (>0 mg/1, <2 mg/ 1), and biologically stressful concentrations (>2 mg/1, <5 mg/1). The occurrence, timing (both time of year and duration), frequency of occurrence (periodic or episodic), location in the water column (surface, bot- tom, or throughout) and spatial extent (high, medium, or low) of each observed condition is recorded. The influence of water column stratification (high, me- dium, low, not a factor) on development of low dis- solved oxygen was also noted. Anoxic conditions were reported to occur in 21 estu- aries, and hypoxia in 31 estuaries. In general, both con- ditions are observed annually during the summer and early fall (June to October) and water column stratifi- cation is reported to influence their development. Typi- cally, these conditions are observed in bottom waters; however, anoxia and hypoxia occur throughout the water column in some estuaries. In general, anoxia is observed in all subregions except Texas, while hypoxia is observed in estuaries throughout the region. Bio- logically stressful concentrations were reported to occur annually in the summer and early fall in all 37 estuaries. For the majority of estuaries, biologically stressful concentrations occur throughout the water column; stratification was reported as a factor in the development of this condition. Minimum bottom water dissolved oxygen concentra- tions were reported as unchanged in 16 estuaries from 1970 to 1995. Concentrations increased in nine estuar- ies, decreased in four estuaries and trends were un- known for seven estuaries. In Perdido Bay, concentra- tions were reported to have increased in the mixing and seawater zones and to have decreased in the tidal fresh zone. For six estuaries, responses were based on speculative inference. Anoxia Anoxic conditions were reported to occur mostly in bottom waters of 21 estuaries, accounting for two to six percent of the regional esruarine area and occur- ring throughout all subregions except for Texas. This condition occurs on a periodic basis from June through October. The influence of water column stratification on the development of anoxia ranged from low to high except for North Ten Thousand Islands, Sarasota Bay, Barataria Bay and Calcasieu Lake, for which it was not a factor. The spatial extent of anoxia is low in the tidal fresh zone (up to 16 percent of area), and very low in the mixing (up to five percent) and seawater zone (up to seven percent) zones. For part or all of three estuar- ies it is unknown whether anoxia occurs, and for part or all of five estuaries, responses were based on specu- lative inference. Declines in duration, frequency of occurrence, and spatial coverage of anoxic events were reported for Tampa Bay, Apalachee Bay, Sabine Lake and Galveston Bay. Increases in duration and spatial coverage were reported for Perdido Bay, Atchafalaya/ Vermilion Bays, and Calcasieu Lake, and increases in frequency of oc- currence were also noted for A tchalafaya/ Vermilion Bays. For 17 estuaries anoxia trends were reported as unchanged, and for 14 estuaries trends were reported as unknown. Trend assessments were based on specu- lative inference for four estuaries (Figure 5). Hypoxia Hypoxic conditions (>0 mg/1, <2 mg/1) were reported to occur in bottom waters in 26 estuaries and through- out the water column in five estuaries. For the major- ity of estuaries, this condition is observed periodically from June through October, with the exception of Lower Laguna Madre where it is observed year-round. The spatial extent of observed hypoxia is up to a maxi- mum of 25 percent of the regional esruarine area, up to 39 percent of the tidal fresh zone, up to 18 percent of the mixing zone and up to 35 percent of the seawa- ter zone. This assessment was based on speculative inference for two estuaries. Decreases in the duration, frequency of occurrence and spatial coverage of hypoxic events were reported for Tampa Bay, Apalachee Bay, Sabine Lake, Galveston Bay and Aransas Bay Increases in one or all characteristics of hypoxia were reported for Atchafalaya/Vermilion Bays, Lower Laguna Madre, Florida Bay, Perdido Bay and Apalachicola Bay. Trends for the remaining Gulf estuaries were almost equally split between no change (14 estuaries) in hypoxia and unknown (12 estuaries). Duration and spatial coverage increased in the tidal fresh zone of Calcasieu Lake, but in the mixing zone 16 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico all three characteristics decreased. For five estuaries, trends assessments were based on speculative infer- ence (Figure 5). Biological Stress Biologically stressful levels of dissolved oxygen (>2 mg/1, <5 mg/1) were reported to occur in all Gulf of Mexico estuaries, except Lake Borgne and Mermentau River. This condition occurs on a periodic basis in bot- tom waters of 19 estuaries and throughout the water column in part or all of 23 estuaries. In the majority of estuaries it occurs from June through October, though in some Texas estuaries it begins in April, and in Lower Laguna Madre the condition is persistent. Stratifica- tion is a factor in most estuaries, but for all or part of 15 estuaries it is not a factor. The cumulative area over which it is reported accounts for a maximum of 48 percent of the total regional estuarine area, up to 67 percent of the tidal fresh zone, up to 41 percent of the mixing zone and up to 57 percent of the seawater zone. For two estuaries, responses were based on specula- tive inference. Decreases in duration, frequency of occurrence, and spatial extent were reported for Tampa Bay, Apalachee Bay, Sabine Lake, Galveston Bay and Aransas Bay. In- creases in one or all characteristics of biologically stressful concentrations were noted for Apalachicola Bay, Perdido Bay, Atchafalaya/Vermilion Bays, Calcasieu Lake and Lower Laguna Madre. For 15 es- tuaries, biologically stressful trends were unchanged; trends were reported to be unknown for 12 estuaries. For seven estuaries, responses were based on specula- tive inference (Figure 5). J Ecosystem/Community Response The responses of estuarine ecosystems to nutrient in- puts were characterized by collecting information on the status and trends of four parameters: primary pro- ductivity, pelagic and benthic communities, and sub- merged aquatic vegetation (SAV). Results indicated that primary productivity in the Gulf of Mexico re- gion is dominated by the pelagic community or a mix- ture of pelagic and other communities (i.e., benthic, submergent and /or emergent). Diatoms, or a diverse mixture that includes diatoms, dominate the plank- ton community, while annelids, or a diverse mixture that includes annelids, dominate the benthic commu- nity. SAV was reported in all but three of the region's estuaries, mostly in the mixing and seawater zones at a low or very low spatial coverage. Information regarding historical shifts in the estuarine ecosystem indicated that changes took place in 27 Gulf of Mexico estuaries during the period 1970-95, prima- rily in the mixing and seawater zones. Changes in all four ecosystem parameters occurred in three estuar- ies at opposite ends of the Gulf of Mexico region - Florida Bay and Upper and Lower Laguna Madre. Changes in three parameters (mostly primary produc- tivity, the benthic community and SAV spatial cover- age) were reported in Lake Pontchartrain, Barataria Bay, Terrebonne/Timbalier Bays and Baffin Bay. In general, where changes in primary productivity oc- curred, dominance shifted from a benthic to a pelagic community or from an emergent to a submergent com- munity. Within the pelagic community, dominance shifted from blue-green algae to diatoms in a number of Florida estuaries and from diatoms or a diverse mix- ture of plankton groups to the brown tide algae, Aureoumbra lagunensis, in estuaries of southern Texas. A shift from a diversely mixed benthic community to one dominated increasingly by annelids was reported in six estuaries, mostly in the Texas Coast subregion. The spatial coverage of SAV was reported to have de- clined in parts of 17 estuaries and to have increased in parts of 12 estuaries. The factors most attributed to shifts/trends in the ecosystem parameters were changes in point and nonpoint sources, changes in hy- drology and the physical alteration of the watershed. Primary Productivity Pelagic (plankton) communities were identified as the dominant primary producer in one or more salinity zones in 27 Gulf of Mexico estuaries, representing 47 percent of the region's estuarine surface area. In most of the region's remaining area, the dominant producer reported was a diverse mixture of pelagic communi- ties and one of three other producers: emergent (wet- land) communities in parts of 12 estuaries, benthic communities in parts of nine estuaries, and SAV in parts of three estuaries. Across the region, pelagic or- ganisms were the most reported primary producer in each salinity zone. A diverse mixture of pelagic and benthic communities was dominant in 50 percent of the region's tidal fresh zone, although this area was comprised of only two estuaries: Barataria Bay and the Atchafalaya/Vermilion Bays. Pelagic communities were the most reported primary producer in all Gulf subregions except the Mississippi Delta /Louisiana Coast, where a mixture of pelagic and benthic organ- isms were dominant. Wetlands, or a mixture of wet- lands and pelagic communities, were reported mostly in the mixing zone within the Mississippi Delta/Loui- siana Coast and Panhandle Coast subregions. SAV, or a diverse mixture of SAV and pelagic communities, was the dominant primary producer in the seawater zone of Florida Bay and estuaries of the Texas Coast. Historical shifts in dominance (ca. 1970-95) from one primary producer to another, were reported in parts 17 NOAA's Estuarine Eutrvphication Survey: Volume 4 - Gulf of Mexico of 13 estuaries, mostly in the mixing and seawater zones. In six estuaries, dominance shifted from benthic to pelagic organisms, primarily due to changes in non point sources and /or the physical alteration of the wa- tershed. In five other estuaries, primary production shifted from an emergent to a submergent system (ei- ther pelagic, benthic and /or SAV) as a result of distur- bances to the estuarine basin. A shift from pelagic to benthic organisms in the Apalachee Bay seawater zone was attributed to changes in point sources; a similar shift in the Atchafalaya/ Vermilion Bays tidal fresh zone was attributed to physical alteration of the wa- tershed. Shifts were reported as unchanged in all or parts of 27 estuaries (51 percent of the region's estua- rine surface area). No information was available for the remaining 17 percent of the region. Pelagic Community Diatoms were reported as the dominant plankton group, in terms of abundance, in the Gulf of Mexico region, occurring in at least one salinity zone in 20 es- tuaries, particularly in the mixing and seawater zones and in the Western Florida Coast and Big Bend /Pan- handle Coast subregions. In parts of 17 estuaries, no single plankton group was identified as dominant, but rather a mixture of groups, including diatoms, flagel- lates, and /or blue-green algae. Communities domi- nated by blue-green algae, or a diverse mixture that included blue-green algae, were reported in parts of eight estuaries, including 65 percent of the region's tidal fresh zone. Flagellates, or a diverse mixture that included flagellates, were reported in parts of eight estuaries. No information was available for parts of 16 estuaries. During the period 1970-1995, shifts in plankton domi- nance from one taxonomic group to another were re- ported in eight estuaries, primarily in the mixing and seawater zones. In three estuaries within the Western Florida Coast and Panhandle Coast subregions, domi- nance shifted from blue-green algae to diatoms, due to changes in point and nonpoint sources. A shift from diatoms, or a diverse mixture of plankton groups to the brown tide alga, Aureoumbra lagunensis, was re- ported in the seawater zone of Baffin Bay and the Up- per and Lower Laguna Madre, and was attributed to transport from offshore waters and changes in nonpoint sources. Dominance shifted to blue-green al- gae from diatoms in the seawater zone of Florida Bay as a result of changes in point and nonpoint sources, and from green algae in the mixing zone of Lake Pontchartrain due to unknown factors. Shifts were re- ported as unchanged in all or parts of 26 estuaries (59 percent of the region's estuarine surface area). No in- formation was available for parts of 18 estuaries. Benthic Community In parts of 28 estuaries, no single group was identified as the dominant (most abundant) benthic community, but rather a diverse mixture of groups, including an- nelids, crustaceans, mollusks, and /or insects. Anne- lids were reported as the dominant community in all or parts of 24 estuaries, and a diverse mixture that in- cluded annelids was reported in parts of nine estuar- ies. Communities dominated by insects, or a diverse mixture that included insects, were reported in the tidal fresh zone of seven estuaries within the Panhandle Coast and Mississippi Delta/ Louisiana Coast subre- gions. Mollusks, or a diverse mixture that included mollusks, were reported in parts of five estuaries, in- cluding 54 percent of the region's tidal fresh zone. The tidal fresh and mixing zones of Atchafalaya /Vermil- ion Bays were reported to be a diverse mixture with mollusks and crustaceans dominating. Shifts in benthic dominance from one taxonomic group to another were reported to have occurred in eight Gulf of Mexico estuaries during the period 1970-1995. In five estuaries within the Texas Coast and one within the Louisiana Coast, a shift from a diversely mixed community to one dominated increasingly by anne- lids was reported, mostly in the mixing and seawater zones. The contributing factors attributed to this shift were changes in point sources and the occurrence of brown tides. Crustaceans declined in dominance in the mixing zone of Barataria Bay and the Terrebonne/ Timbalier Bays due to physical alteration of the wa- tershed. A shift from annelids to mollusks was reported in the mixing zone of Florida Bay; however, the fac- tors contributing to the shift were unknown. The benthic community shifted from a diverse mixture to one increasingly dominated by an unnamed exotic species in the tidal fresh zone of Charlotte Harbor. Shifts were reported as unchanged in parts of all but five Gulf of Mexico estuaries; in two of those estuaries (Sarasota Bay and Lake Borgne), no information was available. Submerged Aquatic Vegetation (SAV) The presence of SAV was reported in parts of every Gulf of Mexico estuary except three in the Mississippi Delta /Louisiana Coast subregion (Mississippi River, Atchafalaya/Vermilion Bays, Mermentau River). No SAV was reported in parts of 17 estuaries. The spatial coverage of SAV (to depths of one meter below mean low water) was reported to be low (>10<25 percent surface area) or very low (<10 percent surface area) in 32 estuaries, particularly in the mixing zone. A me- dium spatial coverage (>25<50 percent surface area) was reported in nine estuaries, primarily in the sea- water zone and in the Western Florida Coast subre- 18 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico gion. The spatial coverage was high (>50 percent sur- face area) in the seawater zone of Apalachee Bay and the Upper and Lower Laguna Madre. For all estuaries in which SAV was reported, the combined spatial cov- erage was equivalent to between 12 and 24% of the region's estuarine surface area. The spatial coverage of SAV was reported to have de- clined in 15 estuaries, primarily in the mixing and sea- water zones. Declining trends generally occurred at a low or medium magnitude (0-50 percent change), with the exception of the mixing zone of Lake Pontchartrain and Galveston Bay, where the magnitude was high (>50 percent change). Several factors were attributed to the declines, including physical alteration of the wa- tershed in seven estuaries, changes in nonpoint sources in five estuaries and changes in hydrology in three es- tuaries. Epiphytes and macroalgae were reported to contribute to the declining coverage in the mixing zone of Lake Pontchartrain and the seawater zone of the Lower Laguna Madre. A decrease in coverage in the mixing zone of Choctawhatchee Bay was associated with an increase in suspended solids. Other factors attributed to declining coverages included an increase in suspended solids in the mixing zone of Choctawhatchee Bay, competition with an exotic spe- cies (Hydrilla) in the Atchafalaya River, changes in point sources in the mixing zone of San Antonio Bay, and brown tide occurrence in Lower Laguna Madre. No change in spatial coverage was reported in six es- tuaries. An increase in coverage was reported in 11 estuaries, particularly in the Mississippi Delta/Loui- siana Coast and Texas Coast subregions. Increasing trends occurred mostly at a low magnitude (0-25 per- cent change), with the exception of the seawater zone of the Upper Laguna Madre and Baffin Bay, where the magnitude was medium (>25<50 percent change), and the tidal fresh zone of Apalachicola, where the magni- tude was high (>50 percent change). Factors attributed to the increases included changes in nonpoint sources in seven estuaries, changes in point sources in three estuaries, and physical alteration of the watershed in six estuaries. Climate fluctuations were reported to contribute to increased coverage in the mixing zone of Matagorda Bay and the seawater zone of the Upper Laguna Madre. An increase in mixing zone of the Western Mississippi Sound was associated with changes in hydrology. No information was available for parts of 16 estuaries. 19 NOAA's Estuarine Eutmphication Survey: Volume 4 - Gulf of Mexico References Becassio, A.D., N. Fotheringham, A.E. Redfield, R.L. Frew, W.M. Levitan, J.E. Smith, and J.O. Woodrow Jr. 1982. Gulf Coast ecological inventory: User's guide and information base. U.S. Fish and Wildlife Service. 191 P- Boynton, W.R., W.M. Kemp, and C.W Keefe. 1982. A comparative analysis of nutrients and other factors influencing estuarine phytoplankton production. In: V.S. Kennedy (ed.), Estuarine Comparisons. New York City: Academic Press, pp. 69-90. Burkholder, J.M., KM. Mason, and H.B. Glasgow Jr. 1992. Water-column nitrate enrichment promotes de- cline of eelgrass Zostera marina evidence from seasonal mesocosm experiments. Mar. Ecol. Prog. Ser. 81:163- 178. Burkholder, J.M., E.J. Noga, C.H. Hobbs, and H.B. Glasgow Jr. 1992. New "phantom" dinoflagellate is the causative agent of major estuarine fish kills. Nature 358:407-410. Cooper, S.R. 1995. Chesapeake Bay watershed histori- cal land use: Impacts on water quality and diatom com- munities. Ecol. App. 5. Culliton, T.J., M.A. Warren, T.R. Goodspeed, D.G. Remer, CM. Blackwell, and J.D. McDonough III. 1990. 50 years of population change along the nation's coasts 1960-2010. Coastal Trends Series report no. 2. Rockville, MD: National Oceanic and Atmospheric Administra- tion, Strategic Assessment Branch. 41 p. Day, J.W. Jr., C.A.S. Hall, W.M. Kemp, and A. Yanez- Arancibia. 1989. Estuarine Ecology. New York City: John Wiley and Sons. 558 p. Eadie, B.J., J.A. Robbins, P, Blackwelder, S. Metz, J.H. Trefrey, B. McKee, and T.A. Nelson. 1992. A retrospec- tive analysis of nutrient enhanced coastal ocean pro- ductivity in sediments from the Louisiana conti- nental shelf. In: Proceedings of a conference on nutri- ent-enhanced coastal ocean productivity, Louisiana Universities Marine Consortium, Oct. 1991.TAMU-SG- 92-109. NOAA, Coastal Ocean Program Office; and Texas A&M University Sea Grant Program, pp. 7 - 14. Frithsen, J.B. 1989 (draft). Marine eutrophication: Nu- trient loading, nutrient effects and the federal response. Washington D.C: American Association for the Ad- vancement of Science/EPA Environmental Science and Engineering. 66 p. Hinga, K.R., D.W. Stanley, C.J. Klein, D.T Lucid, and M.J. Katz (eds.). 1991. The national estuarine eutrophi- cation project: Workshop proceedings. Rockville, MD: National Oceanic and Atmospheric Administration and the University of Rhode Island Graduate School of Oceanography. 41 p. Jaworski, N.A. 1981. Sources of nutrients and the scale of eutrophication problems in estuaries. In: B.J. Neilson and L.E. Cronin (eds.), Estuaries and Nutrients. Clifton, NJ: Humana Press, pp. 83-110. Kemp, W.M., R.R. Twilley, J.C. Stevenson, W.R. Boynton, and J.C. Means. 1983. The decline of sub- merged vascular plants in upper Chesapeake Bay: Summary of results concerning possible causes. Mar. Tech. Soc. Journal 17(2):78-89. Likens, G.E. 1972. Nutrients and eutrophication: The limiting nutrient controversy. Proceedings of a sym- posium on nutrients and eutrophication, W.K. Kellogg Biological Station, Michigan State University, Hickory Corners, MI, Feb. 11-12, 1971. Lawrence, KS: Allen Press, Inc., for the American Society of Limnology and Oceanography, Inc. 328 p. Lowe, J. A., D.R.G. Farrow, A.S. Pait, S.J. Arenstam, and E.F. Lavan. 1991. Fish kills in coastal waters, 1980-1989. Rockville, MD: NOAA, Office of Ocean Resources Conservation and Assessment, Strategic Environmen- tal Assessments Division. 69 p. National Academy of Sciences (NAS). 1969. Eutrophi- cation: Causes, consequences, correctives. Proceedings of an international symposium on eutrophication, Uni- versity of Wisconsin, 1967. Washington, DC: NAS Printing and Publishing Office. 661 p. National Oceanic and Atmospheric Administration (NOAA). 1996. NOAA's Estuarine Eutrophication Survey, Vol. 1: South Atlantic Region. Silver Spring, MD: Office of Ocean Resources and Conservation As- sessment. 50 p. NOAA. 1992a. Red tides: A summary of issues and activities in the United States. Rockville, MD: Office of Ocean Resources and Conservation Assessment. 23 P- NOAA. 1991. Nutrient-enhanced coastal ocean pro- ductivity. In: Proceedings of a conference on nutrient- enhanced coastal ocean productivity, Louisiana Uni- versities Marine Consortium, Oct. 1991.TAMU-SG-92- 109. NOAA, Coastal Ocean Program Office; and Texas A&M University Sea Grant Program, pp. 150-153. 20 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico NOAA. 1989. Susceptibility and status of East Coast estuaries to nutrient discharges: Albemarle /Pamlico Sounds to Biscayne Bay. Rockville, MD: Office of Ocean Resources Conservation and Assessment. 31 p. Nixon, S.W. 1995. Coastal marine eutrophication: A definition, social causes, and future concerns. Ophelia 41:199-219. Nixon, S.W. 1983. Estuarine ecology: A comparative and experimental analysis using 14 estuaries and the MER1 mesocosms. Final report to the U.S. Environ- mental Protection Agency, Chesapeake Bay Program, Grant No. X-003259-01. April 1993. Nixon, S.W., CD. Hunt, and B.N. Nowicki. 1986. The retention of nutrients (C,N,P), heavy metals (Mn, Cd, Pb, Cu), and petroleum hydrocarbons in Narragansett Bay. In: P. Lasserre and J.M. Martin (eds.), Bio- geochemical Processes at the Land-Sea Boundary. Amsterdam: Elsevier Press, pp. 99-122. Orlando, S.P Jr., L.P Rozas, G.H. Ward, and C.J. Klein. 1993. Salinity characteristics of Gulf of Mexico estuar- ies. Silver Spring, MD: NOAA, Office of Ocean Re- sources Conservation and Assessment. 209 p. Orth, R.J. and K.A. Moore. 1984. Distribution and abundance of submerged aquatic vegetation in Chesa- peake Bay: An historical perspective. Estuaries 7:531- 540. Paerl, H.W. 1988. Nuisance phytoplankton blooms in coastal estuarine and inland waters. Limnology and Oceanography 33:823-847. Rabalais, N.N. 1992. An updated summary of status and trends in indicators of nutrient enrichment in the Gulf of Mexico. Prepared for: Gulf of Mexico Program, Technical Steering Committee, Nutrient Subcommit- tee. Publication No. EPA/800-R-92-004. Stennis Space Center, MS; GOM Program. 421 pp. Rabalais, N.N. and D.E. Harper Jr. 1992. Studies of benthic biota in areas affected by moderate and severe hypoxia. In: Proceedings of a conference on nutrient- enhanced coastal ocean productivity, Louisiana Uni- versities Marine Consortium, Oct. 1991TAMU-SG-92- 109. NOAA, Coastal Ocean Program Office; and Texas A&M University Sea Grant Program, pp. 150-153. Rabalais, N.N., R.E. Turner, and Q. Dortch. 1992. Loui- siana continental shelf sediments: Indicators of river- ine influence. In: Proceedings of a conference on nutri- ent-enhanced coastal ocean productivity, Louisiana Universities Marine Consortium, Oct. 1991 TAMU-SG- 92-109. NOAA, Coastal Ocean Program Office; and Texas A&M University Sea Grant Program, pp. 31 - 35 Rabalais, N.N., R.E. Turner, D. Justic, Q. Dortch, W.J. Wiseman, Jr. and B.K. Sen Gupta. 1996. Nutrient changes in the Mississippi River and system response on the adjacent continental shelf. Estuaries 19(2B): 386- 407. Ryther, J.H. and W.N. Dunstan. 1971. Nitrogen and eutrophication in the coastal marine environment. Sci- ence 171:1008-1013. Smayda, T.J. 1989. Primary production and the global epidemic of phytoplankton blooms in the sea: A link- age? In: E.M. Cosper, V.M. Bricelj, and E.J. Carpenter (eds.), Novel phytoplankton blooms: Causes and ef- fects of recurrent brown tides and other unusual blooms. Coastal and Estuarine Series 35. Berlin: Springer- Verlag. pp. 449-483. Stevenson, J.C., L.W Staver, and K.W. Staver. 1993. Wa- ter quality associated with survival of submersed aquatic vegetation along an estuarine gradient. Estu- aries 16(2):346-361. Turner, R.E. and N.N. Rabalais. 1994. Coastal eutrophi- cation near the Mississippi river delta. Nature 368:619- 621. Turner, R.E. and N.N. Rabalais. 1991. Changes in Mis- sissippi River water quality this century, implications for coastal food webs. BioScience 41(3):1340-147. Whitledge, T.E. 1985. Nationwide review of oxygen depletion and eutrophication in estuarine and coastal waters: Executive summary. (Completion report sub- mitted to U.S. Dept. of Commerce.) Rockville, MD: NOAA, NOS. 28 p. Whitledge, T.E. and W.M. Pulich Jr. 1991. Report of the brown tide symposium and workshop, July 15-16, 1991. Port Aransas, TX: Marine Science Institute, Uni- versity of Texas. 44 p. 21 Estuary Summaries This section presents one-page summaries on the status and trends of eutrophication conditions for the 37 Gulf of Mexico estuaries and the Mississippi/Atchafalaya River Plume. The summary information is organized into four sections: algal conditions, nutrients, dissolved oxygen, and ecosystem/community responses. Each page also includes a salinity map depicting the spatial framework for which survey information was collected, selected physical and hydrologic characteris- tics, and a narrative overview of the survey information. Salinity Maps. Salinity maps depict the estuary extent, salinity zones, and subareas within salinity zones. Salinity zones are divided into tidal fresh (0.0-0.5 ppt), mixing (0.5-25.0 ppt) and seawater ( >25.0 ppt) based on average annual salinity found throughout the water column. Subareas were identified by survey participants as regions that were either better understood than the rest of a salinity zone, or that behaved differently, or both. Each map also has an inset showing the location of the estuary and its estuarine drainage area (EDA) (see below). Physical and Hydrologic Data. Physical and hydrologic characteristics data are included so that readers can better understand the survey results and make meaningful comparisons among the estuaries. The EDA is the land and water component of a watershed that drains into and most directly affects estuarine waters. The average daily inflow is the estimated discharge of freshwater into the estuary. Surface area includes the area from the head of tide to the boundary with other water bodies. Average depth is the mean depth from mid-tide level. Volume is the product of the surface area and the average depth. Survey Results. Selected data are presented in a unique format that is intended to highlight survey results for each estuary. The existing conditions symbols represent either the maximum conditions predominating for one or more months in a typical year, or indicate resource impacts due to bloom events. The trends (circa 1970- 1995 unless otherwise stated) symbols indicate either the direction and magnitude of change in concentrations, or in the frequency of occurrence. The four sections on each page include a text block to highlight additional information such as probable months of occurrence and periodicity for each parameter, limiting factors to algal biomass, nuisance and toxic algal species, nutrient forms and degree of water column stratification. Some parameters are not characterized by symbols on the estuary pages. These include macroalgal and epi- phyte abundance, biological stress, minimum average monthly bottom dissolved oxygen trends, temporal shifts in primary productivity, benthic community shifts, intertidal wetlands and planktonic community shifts. These parameters are described in the Regional Overview section (starting on page 6) and, where relevant, are highlighted in the text blocks under each parameter section on the estuary pages. See the next page for a key that explains the symbols used on the summary pages. See Table 1 on page 3 for complete details about the characteristics of each parameter. Estuary Page Estuary Page Estuary Page Florida Bay 24 Pensacola Bay 37 Mermentau River 50 South Ten Thousand Islands 25 Perdido Bay 38 Calcasieu Lake 51 North Ten Thousand Islands 26 Mobile Bay 39 Sabine Lake 52 Rookery Bay 27 East Mississippi Sound 40 Galveston Bay 53 Charlotte Harbor 28 West Mississippi Sound 41 Brazos River 54 Caloosahatchee River 29 Lake Borgne 42 Matagorda Bay 55 Sarasota Bay 30 Lake Pontchartrain 43 San Antonio Bay 56 Tampa Bay 31 Breton/Chandeleur Sounds 44 Aransas Bay 57 Suwannee River 32 Mississippi River 45 Corpus Christi Bay 58 Apalachee Bay 33 Barataria Bay 46 Upper Laguna Madre 59 Apalachicola Bay 34 Terrebonne/Timbalier Bays 47 Baffin Bay 60 St. Andrew Bay 35 Atchafalaya/ Vermilion Bays 48 Lower Laguna Madre 61 Choctawhatchee Bay 36 Miss./Atchaf. River Plume 49 22 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico Key to Symbols Used on Estuary Summaries Tidal Fresh Mixing M 25-50% *\ Seawater Subarea X Subarea Y M O 50-100% l 60ug/l H high chl-a: >20, <60 ug/l turbidity: secchi <1m TDN: >1 mg/l TDP: >0.1 mg/l SAV >50, £100 % coverage fj[ medium chl-a: >5, <20 ug/l turbidity: secchi ^1 m, <3m TDN:>0.1,<1 mg/l TDP:>0.01,<0.1 mg/l SAV >25, £ 50 % coverage L low chl-a: >0, <5_ug/l turbidity: secchi >3m TDN: >0, <0.1 mg/l TDP: >0, <0.01 mg/l SAV >10, < 25 % coverage Y[_ very low SAV >0, £10 % coverage N§ no SAV in zone B blackwater area 9 unknown Event Occurrences (Nuisance/Toxic Algae, d.o.) Y impacts on resources nuisance algae: impacts occur toxic algae: impacts occur or low d.o. is observed anoxia: 0 mg/l hypoxia: >0, <2 mg/l N no resource impacts no nuisance algae impacts no toxic algae impacts or low d.o. not observed no anoxic events no hypoxic events 9 unknown Direction of Change Magnitude of Change (Concentrations or Frequency of Event Occunences) "^K increase "^K high no trend *> unknown >50%, <100% decrease <> medium U >25%. <50% /\ low LJ>0%, <25% /^\ magnitude LI unknown 23 NOAA's Estuarine Eutwphication Survey: Volume 4 - Gulf of Mexico Florida Bay Uarathon Algal Conditions TF Mixing L — M 60-100% N N Saawatef M 10-25% 0" H 50-100% t M 25-50% t H 50-100% t H 50-100% t H 25-50% t N - Yt Y * N - N - Y — Maximum Chl-a concentrations occur periodically In January in Zone 1 with phosphorus iirnitingJurketoJanuaryinZoM2wimplv36phcfliisa^ January in Zone 3 with nitrogen and silica limiting, 199046 Chl-a decrease in Zone 1 attributed to hydrologic changes, and increases in Zones 2 and 3 attributed to external salinities. Ina^asemhjrbidity speculated to r^atrribu ternal sources in Zone 2, and external sources and SAV in Zone 3. Nuisance blue-green Synechococcus spp. occurs periodically June to January in Zcm 2 And October to Febru- ary in Zone 3, and toxic Gymnodirdum breve occurs periodically February to March. In- crease in nuisance blooms reported for 1976-86. ' Ecosystem/Community Responses J TF Mixing Seawatar Zone 1 Zom2 Zon«3 M — M & M * M * Primary productivity dominated by emergent and pelagic communities in mixing zone, benthic in Zone 1, pelagic in Zone 2, and pelagSc/benthic in Zone 3; Zones 2 and 3 were historically bentrdc. Planktonk community is diverse in mixing zone and Zone 1, domi- nated by blue-green algae and diatoms in Zone 2, and diatoms in Zone 3; benthic commu- rdty dominated by annelids in mixing zone and Zone 3, diverse in Zones land 2 External oandioon* contributed to loss of annelid dominance in Zone 2. In Florida Bay, chlorophyll a concentrations range from low to high and turbidity and nitrogen concentrations range from medium to high. Phosphorus concentrations are low. Nui- sance and toxic blooms occur only in the seawater zone. Anoxia and hypoxia are also observed. SAV spatial cover- age is medium. Trends for chlorophyll a, turbidity, nuisance algae, and ni- trogen increased, while SAV spatial coverage and phospho- rus concentrations decreased. Most trends for anoxia and hypoxia are unknown, except an increase in hypoxia in Zone 2. Toxic algal blooms have remained unchanged. Physical and Hydrologic Characteristics Estuarine Drainage Area (mi2) 991 Avg. Daily Inflow (cfs) n/a Estuary TF Mixing Seawater Surface Area<£$ 883.1 14.5 Zone 1 Zone 2 Zone 3 352.1 89.0 427.5 Average Depth m 7.3 1.0 n/a n/a n/a Volume (b&oncultl 179 0.4 n/a n/a n/a A shallow, lagoonal estuary. Salinity patterns largely affected by periodic discharges from water control structures. Salinity variability dominated by prevailing wind-driven circulation and weather events. A vertically mixed water column persists and salinities are high to hypersaline. Tidal range is approximately 2 ft near Cape Sable. Nutrients TF M 50-100% ft L 0 Zone 1 Zone 2 Zones M so-100% 1> H 60-100% M 60-100% , n , ... , Rgure shows dissolved organic nitrogen. Dissolved inorganic is low except in Zone 2 where it is medium. Maximum concentrations occur May /June through September, ex- cept m Zone 3 wriere mecUum roncentraticuu are cifc^rve^ Dissolved Oxygen 1 TF Mixing Seawater l*i Zone 1 Zona 2 Zona 3 N 9 ■ N 9 ■ Y 9 ■ Y 9 ■ 50-100% 0-10% Y 60-100% 9 ■ Y 9 ■ Y 1> Y 9 ■ BO-100% 60-100% 60-100% Low dissolved oxygen conditons occur throughout the water column periodically be- tween June and October. 24 Key on page 23 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico South Ten Thousand Islands Salinity Zones 0 Tidal Fresh ■ Mixing Zone ■ SeawaterZone Algal Conditions Tidal Fresh Mixing Seawater E M * M ■ 25-50% 50-100% H 9 ■ H * 50-100% 50-100% m 9 ■ 9 ■ N Erf N 9 ■ N Maximum Chl-a concentrations occur throughout the year with co- limiting factors of phosphorus and nitrogen. Increase in Chl-a attributed to hydrologic changes. High turbidity occurs throughout the year. Ecosystem/Community Responses Tidal Fresh Mixing Seawater r L * L 0 ■ I Primary productivity is a mix of salt marsh and pelagic in mixing zone and emergent, pelagic and bentnk in seawater zone. Mixing zone productivity historically dominated by salt marsh, but speculated to have changed due to alterations of hydrology. Planktonk community dominated by diatoms; benthic community is a diverse mixture. In South Ten Thousand Islands, chlorophyll a concentrations are medium, turbidity is high, and no toxic or nuisance blooms are observed. Nitrogen concentrations range from medium to high and phosphorus concentrations are me- dium. Anoxia and hypoxia are observed in both the mixing and seawater zones. Spatial coverage of SAV is low. Chlorophyll a and nitrogen concentrations have increased and SAV spatial coverage has decreased. Nuisance and toxic blooms, nitrogen, phosphorus, anoxia and hypoxia were unchanged. Physical and Hydrologic Characteristics Estuarine Drainage Area (mP) -\ (244 Avg. Daily Inflow (cfs) n/a Estuary Tidal Fresh Mixing Seawater Surface Areafm*; 78.2 57.4 20.8 Average Depth w 6.5 6.0 6.9 Volume (btkmcun) 14 9.6 4.0 I A shallow, lagoonal estuary consisting of Whitewater Bay, small tidal rivers, small mangrove islands, and tidal marshes. Receives majority of freshwater as overland sheet flow from Shark River Slough and! regulated canals from Lake Okeechobee. Circulation is wind driven and a vertically mixed water column exists. Tidal range is 3.6 ft near mouth of Whitewater Bay. Nutrients Tidal Fresh Mixing Seawater H H 50-100% ft M 50-100% M 50-100% M 50-100% In mixing zone, nitrogen concentrations are for dissolved organic nitrogen. Conditions occur December - May. Dissolved Oxygen THal Fresh Mixing Goawator KJ Y • Y - 50-100%' 50-100%" Y • Y - 50-100%' 50-100%' Conditions occur throughout the water column July and September episodically for anoxia, and periodically for hypoxia. Key on page 23 25 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico North Ten Thousand Islands s ^ ^ \ n 1 ^^^Hjfc« ^♦$F *L Gulf of Mexico \w* Mlftmr Salinity Zones North 0 4 8 0 Tidal Fresh ■ Mixing Zone ■ Seawater Zone Miles Algal Conditions Tidal Fresh Mixing Seawater M 50-1 00°X M 25-50% H 50-100% H 25-50% N N N N Maximum Chki concentrations occurperiodlcally in flw summer Willi co- limiting factors of phosphorus and nitrogen. High turbidity occurs periodically in summer. Ecosystem/Community Responses Tidal Fresh Mixing " Seawater VL 9 ■ M 9 ■ Primary productivity is emergent and pelagic in mixing zone, and pelagic in seawater zone. Planktonic community dominated by diatoms in seawater zone; benthfc community is a diverse mixture. ' In North Ten Thousand Islands, chlorophyll a and phospho- rus concentrations are medium. Nitrogen concentrations range from low to medium and turbidity is high. Nuisance and toxic blooms are not observed, but anoxia and hypoxia are. SAV spatial coverage ranges from very low to medium. Chlorophyll a, turbidity, nuisance and toxic blooms remained unchanged. Nutrients, dissolved oxygen and SAV trends were unknown. Physical and Hydrologlc Characteristics Estuarine Drainage Area (mi2)902 Avg. Daily Inflow (cfs) n/a Estuary Tidal Fr«sh Mixing Seawater Surface AreaM!> 130.8 42.1 88.7 Average Depth dv 5.7 5.3 5.8 Volume (bttoncutl) 21 6.2 14 A shallow estuary consisting of smalt mangrove islands, small tidal channels and tidal marshes. Receives majority of freshwater from overland sheet flow and regulated canal structures connected to Lake Okeechobee. Circulation is wind driven and a vertically mixed water column is typical. Tidal range is 35 ft near Chatham River mouth. Nutrients Tkfei Fresh Mixing wcHxWcuOT I M 50-100% 9 ■ L 9 ■ I M 50-100% 9 ■ M 50-100% 9 ■ In the mixing zone nitrogen ccwxntratiorts reported are dissolved otgank: nitrogen. Medium concentrations occur December through May. Dissolved Oxygen I TWbJ Fresh Mixing Seawater Y 9 ■ * Y 9 ■ 10-25% 0-10% I Y 9 ■ Y 9 ■ 25-50% 10-25% Biological stress is observed in 50 - 100 percent of the mixing zone and 25 - 50 percent of the seawater zones. D.O. ccmdtrlons occur throughout water column between July and September. Anoxia occurrences are episodic, hypoxia and biological stress occurrences are periodic. 26 Key on page 23 NOAA's Estuarine Eutrovhication Survey: Volume 4 - Gulf of Mexico Rookery Bay Salinity Zone* 0 Tidal Froh ■ Mixing Zone ■ Sawiter Zone /^ p i) Gulf of Mexico Lowmr pj\ J£aW< - (No OJulWyi, Si-*™1 lC*3 jfc^JRX North 0 1 2 Miles ^4 Algal Conditions ! Tklal Fresh Mbdng Seawater B* Upper Bay M 25-50% M 25-50% H 50-100% H 50-100* B^j N • N • B N * N * Maximum Chl-u concentrations occur episodically with a limiting factor of nitrogen, speculated to be co-limiting with phosphorus in seawater zone. High turbidity occurs all year fat mixing zone and episodically in seawater zone. Ecosystem/Community Responses Tidal Fresh Mbdng VL m Seawater Upper Bay # L — Primary productivity is dominated by emergent and pelagic < Pbnktonk community dominated by diatoms; benthk dominated by annelids. communities, community In Rookery Bay, chlorophyll a concentrations are medium, turbidity is high, nitrogen concentrations are medium and phosphorus concentrations range from medium to high. There are no observed nuisance and toxic blooms. Anoxia and hypoxia are reported to occur in the mixing zone. SAV spatial coverage ranges from low to very low. Parameters for lower bay are unknown. Trends were stable with the exception of unknown trends for anoxia, hypoxia, and SAV coverage in the mixing zone. Physical and Hydrologlc Characteristics Estuarine Drainage Area (mP) \q\ Avg. Daily Inflow (cfs) n/a Estuary Tidal Fresh Mixing Seawater Surface Are&(mP) 15.2 0.2 Upper Bay Lower Bay 6.3 8.7 Average Depth ft) 5.0 3.7 n/a rt/a Volume (bOonajft) 2.1 0.09 n/a n/a A shallow estuary consisting of Rookery Bay, and small embayments whit small mangrove islands and tidal channels. Receives majority of freshwater from Henderson Creek and overland sheet flow. Circulation is wind driven and a vertically mixed water column is typical. Tidal range is 1.7 ft near the mouth of the Addison Bay. Nutrients Tidal Fresh Mbdng Seawater Upper Bay M M 25-50% 50-100% M H 50-100% 25-50% Nitrogen concentrations reported are dissolved inorganic nitrogen. Conditions occur July to October. Dissolved Oxygen Tidal Fresh Mi Seawater Lt=9 Upper Bay Y 7 9 ■ N 9 ■ * Y 7 9 ■ N 9 ■ Biological stress is observed in mixing and seawater zones. Months 0/ occurrence, frequency, and water column stratification effects are unknown. Key on page 23 27 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico Charlotte Harbor Salinity Zones Q Tidal Fresh ■ Mixing Zone ■ Seawater Zone Algal Conditions Tidal Fresh E * 50-100% B Y ? Y ? Mixing E 25-50% B Y — N Seawater M B N Y — Maximum CH-u concentrations occur periodically in spring in tidal fresh zone wi th a limiting factor of light, period Ically in summer in mixing zone with limiting factors of light and nitrogen, and episodically in fall in seawater zone with a limiting factor of nitrogen. Nuisance Ambaena spp.,Chiowcoccus minuius, and Microcystis aeruginosa occur episodically April to June. Toxic Gymnodimum breve occurs episodically. Ecosystem/Community Responses _| UrjaifiBsh Mbdng Seawater W^ NS — L — M — m Primary productivity dominated by pelagic community. Plelagic community dominated by blue-green algae in tidal fresh zone, flagellates and diatoms in mixing zone, and diatoms to seawater zone; benthic community dominated by annelids in tidal fresh and mixing zones and is diverse in seawater zone. Introduction of exotic species speculated to contribute to toss of benthic diversity in tidal fresh zone. SAV trend is from 1982-1994. In Charlotte Harbor, chlorophyll a concentrations range from medium to hypereutrophic and turbidity is characteristic of a blackwater system. Nuisance and toxic algal blooms occur and anoxia and hypoxia are also observed. Nitrogen con- centrations range from low to high, and phosphorus con- centrations are high. SAV spatial coverage is low in the mix- ing zone and medium in the seawater zone. Parameters for Pine Island Sound are unknown. Conditions remained mostly unchanged. The exceptions are a decrease in phosphorus concentrations and a speculated increase in nitrogen. Physical and Hydrologlc Characteristics Estuarine Drainage Area (mP) 4,877 Avg. Daily Inflow (cfs) 3,958 Estuary Tkjal Fresh Mbdng Seawater Surface Area fm#; 209.0 2.0 86.8 120.2 Average Depth Seawater Elevated concentrations occur persistently throughout the year. Dissolved Oxygen TWal Fresh Mbdna Seawater Upper River Lower River N 9 ■ N ■ Y 10-25% 9 ■ N 9 ■ Hypoxia occurs periodically an bottom May through August Biological stress occurs throughout the water column periodically over a high spatial extent of die Upper River and over a very low extent of the Lower River from May through September. Key on page 23 29 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico Sarasota Bay Gulf of Mexico Salinity Zone* 0 Tidal Fresh ■ Mixing Zone ■ Sea water Zone Miles Algal Conditions Tidal Fresh Mixing Seawater 1 H 10-25% 0 M 50-100% 0 : J i I i Y 9 ■ ; i Y 9 ■ Chl-a concentratloris occur periodically in summer with a limiting factor of nitrogen. Medium turbidity occurs throughout the year. Decrease in Chl-a and turbidity associated with point and non-point sources. Toxic Gymnodbtium breve occurs in seawater zone episodically. Ecosystem/Community Responses TWeJ Fresh Mixta Seawater r^ M tf Primary productivity is dominated by pelagic community. Pelagic community was diverse, now dominated by diatoms and flagellates; benthic community is dominated by annelids. Increase in SAV is attributed to changes in point and non-point sources- In Sarasota Bay, chlorophyll a and phosphorus concentra- tions are high, and turbidity and nitrogen concentrations are medium. Nuisance and toxic blooms, as well as anoxia and hypoxia, are observed. SAV spatial coverage is medium. Chlorophyll a, turbidity, nitrogen and phosphorus concen- trations declined, while SAV spatial coverage increased. Trends for nuisance and toxic blooms, and for anoxia and hypoxia, are unknown. Physical and Hydrologlc Characteristics Estuarine Drainage Area (mP) 282 Avg. Daily Inflow (cfs) 380 Estuary Tidal Fresh Mixing Seawater Surface Area (in?/ 51.0 51.0 Average Depth m 6.4 6.4 Volume {b0hn ai ft) 9.1 9.1 An elongated bar-built coastal lagoon. Wind and tidal flows at Longboat and Big Pass influence circulation patterns. Receives majority of freshwater inflow from several small tributaries and storm- water drains. Salinity structure is determined by seasonal patterns of precipitation and evaporation. Tidal range is 13 ft in the bay. Nutrients Tidal Fresh Mixta SG8W9t0f M 50-100% ^> H 50-100% $ Concentrations are reported as total nitrogen and total phosphorus. Elevated concentrations occur throughout the year. Dissolved Oxygen ! Tidal Fresh Mixta Seawater Y 9 ■ 10-25% | Y 9 ■ 10-25% Anoxia and hypoxia occur on bottom periodically between June and September. Biological stress occurs over a medium spatial extent and throughout the water column June to September. 30 Key on page 23 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico Tampa Bay *^ Salinity Zones 0 Tidal Fresh ■ Mixing Zone B Sea water Zone Miles Algal Conditions Tidal Fresh Mixing Seawater | Upper Bay Lower Bay I M \7 E 25-50% 4- H 50-100% \7 M 50-100% ■ ■ I M * 50-100%! H 10-25% * M 50-100°/< L I s i y * Y * N N [ ! S N * N N Y M Maximum Chl-« concentrations occur periodically June to October with limiting factors of nitrogen and light. Highest turbidity occurs periodically July to October. Nuisance blue-greens and dinoflagellat.es occur periodically in summer and toxic Gymnodinium breve occurs in seawater zone episodically. Trends in algal conditions 1980-1995 attributed to changes in point and non-point sources. Ecosystem/Community Responses Tidal Fresh Mixing Seawater ■f 1 Upper Bay Lower Bay E L 9 ■ L O M tf M ■L Primary productivity is dominated by the pelagic community. Pelagic community dominated by diatoms; benthic community dominated by annelids in tidal fresh and mixing zones and Is diverse in seawater zone. Increase in SAV due to changes In point and non-point sources. In Tampa Bay, chlorophyll a concentrations range from me- dium to hypereutrophic and turbidity from medium to high. Nuisance and toxic blooms are observed, as well as anoxia and hypoxia. Nitrogen concentrations range from medium to high and phosphorus concentrations are high. SAV spa- tial coverage ranges from low to medium. Algal conditions, nutrients, anoxia and hypoxia all de- creased, while SAV spatial coverage increased. Physical and Hydrologlc Characteristics Estuarine Drainage Area (mi2) 2,538 Avg. Daily Inflow (cis) 2,400 Estuary Tidal Fresh Mixing Seawater Surface Area (mft 346.1 1.0 84.2 Upper Bay Lower Bay 107.3 153.6 Average Depth Nitrogen concentrations are for dissolved inorganic nitrogen. Total nitrogen is high in mixing and upper seawater zones. Elevated concentrations in tidal fresh zone occur July 'o September/October and December to January. Trends reported for 1980- 95. Dissolved Oxygen TWaJ Fresh Mixing Seawater Upper Bay Lower Bay Y 9 ■ Y 0-10% * Y 9 ■ N 10-25% 10-25*. 1 y: 10-25% ■ Y 1025% * Y ? 10-25% I N Low dissolved oxygen conditions occur periodically July to October in bottom waters. Biological stress occurs on bottom in 25 to 50 percent of lower seawater July to October. Water column stratification contributes moderately to low dissolved oxygen conditions in tidal fresh zone. Trends reported for 1980-95. Minimum average monthly bottom dissolved oxygen increased to a low extent in tidal fresh and mixing zones. Key on page 23 31 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico Suwannee River Gulf of Mexico North t 2.5 1) 0 5 Miles Algal Conditions Tidal Fresh Mixing Seawater E I L * M 50-100% * 9 ■ 9 ■ - ; B B M 50-100% * i I N 9 ■ N 9 ■ N 1 8 N 9 ■ N 9 ■ Y H Maximum Chl-a concentrations occur periodically May to September wife a touting factor of nitrogen. Toxic blooms occur episodically. Ecosystem/Community Responses TidalFre8h Mixing Seawater ■ B L * VL * M mi Primary productivity is dominated by marshes in tidal fresh zone, by the pelagic and marsh communities in mixing zone, and by fee pelagic and benmfc communities in seawater zone. Flanktonic community dominated by diatoms; benthic community dominated by aquatic insects in tidal fresh zone and is diverse in mixing and seawater zones. In Suwannee River, chlorophyll a concentrations range from low to medium. The tidal fresh and mixing zones are black- water; turbidity in the seawater zone is moderate. There are no observed nuisance blooms but toxic blooms occur episodically. Concentrations of nitrogen are medium and phosphorus concentrations range from medium to high. Anoxia and hypoxia are not observed. SAV spatial cover- age ranges from very low to medium. Algal conditions, phosphorous concentrations and SAV re- mained unchanged, while nitrogen concentrations in- creased. Dissolved oxygen trends are unknown. Physical and Hydrologic Characteristics Estuarine Drainage Area (mP) 1 ,845 Avg. Daily Inflow (cfs) 1 1 ,200 Estuary Tidal Fresh Mixing Seawater Surface Areafmf?! 49.9 3.0 28.8 18.1 Average Depth m 4.9 3.5 4.6 5.5 Volume (bUoncutQ 6.8 0.3 3.7 2.8 Consists of Suwannee Sound, the Suwannee River delta, and extensive wetland areas. Freshwater discharge dominated by Suwannee River (2nd largest freshwater source in Florida) and from groundw: sources. Salinity structure is governed by seasonal discharge. Salinity variability most apparent in Suwannee Sound where: tides are a dominant influence and range is approximately 3 ft Nutrients ! TWal Fresh fvBxtng Seawater ! 1 M 50-100% • * M 50-100% * 1> M 50-100% * V. 1 H 50-100% H 50-100% M 50-100% • ":\ Maximum total dissolved nitrogen concentrations occur June to September. Maximum total dissolved phosporus concentrations occur January to April. Dissolved Oxygen I Tidal Fresh Mixing Seawater N ■ N 9 ■ N ■ N 9 ■ N 9 ■ N 9 ■ Biological stress is speculated to occur over a tow i fresh zone in bottom waters periodically from June to? 32 Key on page 23 Apalachee Bay TIM TIM \yaMi* |»jrfly Ajpjf 'mm Gulf Of Mexico Ml North ^ "ft Salinity Zones 0 10 20 0 Tidal Froh ■ Mixing Zone ■ Seawater Zone \J Miles Algal Conditions J TWal Fresh Mixing Seawater j Apalachee Bay Fenholloway River L * M M * 25-50% 50-100% 1 B • M H £ 25-50% 50-100% j N • N N L N * Y N Maximum Chl-a concentrations occur periodically March to May in mixing zone and are persistent in seawater zone, with a speculated limiting factor of nitrogen for both zones. Turbidity concentrations occur all year. Decrease in Chl-a and turbidity reported for 1975-95 and due to changes in point sources. Ecosystem/Community Responses I Tidal Fresh Mixing Seawater c Apalachee Bay Fenholloway River VL H • L ft Primary productivity is dominated by the pelagic community in mixing zone and Fenholloway River, and is benthic and pelagic in seawater zone. Planktonic community dominated by diatoms; benthic community dominated by annelids in mixing zone and Fenholloway River and is diverse In seawater zone. Increase in SAV attributed to change m point sources. NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico In Apalachee Bay, chlorophyll a, nitrogen and phosphorus concentrations range from low to medium. Turbidity is black- water in the tidal fresh zone and medium to high in the mixing and seawater zones. Nuisance blooms are not ob- served, but toxic blooms are observed in the seawater zone. Anoxia and hypoxia are observed. SAV spatial coverage ranges from very low to high. In the Fenholloway River, SAV spatial coverage increased, while declines were reported for chlorophyll a, turbidity, nitrogen, phosphorus, anoxia and hypoxia. Physical and Hydrologlc Characteristics Estuarine Drainage Area (m\2) 3,836 Avg. Dairy Inflow (cfs) 5,300 Estuary TF Mixing Seawater Surface Arearm^j 710.6 0.1 16.5 ApalachM Bey Penhoiowey R 153.0 16.7 Average Depth «» 10.2 7.3 5.8 n/a n/a Volume (bmoncu*) 202.1 0.02 2.7 n/a n/a An open-water estuarine system whose boundaries are not consistently defined. Periphery is lined by many small estuaries, streams, springs, lakes, and freshwater marshes. Salinity structure determined by seasonal freshwater discharge from the Econfina, Fenholloway and Oduockonee Rivers. Tides typically range 2.1 ft near the entrances to major rivets. Nutrients J TWal Fresh Mixing Seawater Apalachee Bay Fenholloway River M L M 4 50-100%' 50-100% M L M * 50-100%" 50-100% Elevated concentrations occur November to April in mixing zone and all year in Fenholloway River. Decreases attributed to changes in point sources. Dissolved Oxygen J TWal Fresh Mixing Coftwttw f Apalachee Bay FenhoSoway Rive* N N Y • 10-25% N Y Y • 4- 0-10% 2S-50N Conditions occur on bottom periodically June to September. Biological stress observed over 50 to 100 percent of Fenholloway River. Water column stratification contributes moderately to dissolved oxygen conditions Decreases in frequency, duration, and spatial coverage of low dissolved oxygen attributed to changes in point sources. Key on page 23 33 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico Apalachicola Bay Algal Conditions Tidal Fresh i ... B N N Mixing M 50-100% H 50-100% N Y * Seawater I — M 50-100% N Maximum Chl-d concentrations occur periodically December to April with a limiting factor of nitrogen in mixing zone and tight in tidal fresh zone. Turbidity occurs throughout year. Toxic Gymnodintum breve occurs In seawater zone episodically June to October. Ecosystem/Community Responses TWal Fresh L t Mbdnfl VL L — Primary productivity is a mix of emergent, benthk and pelagic in tidal fresh zone, and dominated by the pelagic community in mixing and seawater zones. Pknktonk community dominated by diatoms in mixing and seawater zones; benthk: community dominated by annelids and aquatic insects in tidal fresh zone. Is diverse in mixing zone, and dominated by annelids in seawater zone. In Apalachicola Bay, chlorophyll a concentrations range from low to medium. The tidal fresh zone is blackwater, but in the mixing and seawater zones, turbidity is medium to high. Nuisance blooms are not observed, but toxic blooms occur. Nitrogen and phosphorus concentrations range from low to high. Hypoxia is observed, but anoxia does not occur. SAV spatial coverage ranges from very low to low. Trends for most parameters were unchanged. SAV spatial coverage and observations of toxic algal blooms and hypoxia have increased. Physical and Hydrologlc Characteristics Estuarine Drainage Area (mP) 1 ,921 Avg. Dally Inflow (cfs) 29,1 00 Estuary TkJai Fresh Mixing Seawater : Surface Areafm^) 229.2 16.2 133.3 79.7 Average Deptn# 9.0 9.0 7.9 12.9 Volume' (bUoncufQ 57.5 4.1 29.4 28.7 A broad, shallow lagoonal system separated from the Gulf of Mexico by three barrier islands. Consists of Apalachicola Bay and several smaller embayments. Apalachicola River is primary source of freshwater (largest freshwater source in Florida). Salinity structure is determined by Its discharge and by tidal influence near the passes. Tidal range is 1.6 ft near the passes. Nutrients ! TWal Fresh Mixing Seawater . i H 50-100% M 50-100% * L i H 50-100% M 50-100% * L Elevated concentrations occur December through April. Dissolved Oxygen Tkfat Fresh N N — • — : N Y 10-25% 0 N N Biological stress observed in up to 10 percent of tidal fresh and 50 to 100 percent of mixing zone. Low dissolved oxygen conditions occur in bottom waters periodically June to October. Water column stratification is a highly significant factor. Increase in frequency and spatial coverage attributed to non-point sources. 34 Key on page 23 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico St. Andrew Bay Gulf of Mexico North 4 Miles Salinity Zone* 0 Tidal Fresh ■ Mixing Zone ■ Seawater Zone Algal Conditions 1 TWal Fresh Mixing Seawater E M s. -\. 9 ■ ■ 50-100% El M * M 9 ■ 50-100% 50-100% Y •> m Y 9 ■ Y 9 ■ Y 9 ■ * 1 1 Maximum CM-a concentrations occur periodically in summer with a miring factor of phosphorus; increase associated with point and non- >olnt sources. Highest turbidity occurs periodically February to October. Nuisance Atucystis spp., Ambaena spp. and toxic Gymnodinium breve occur ■pisodically for days in summer. Ecosystem/Community Responses I TWal Fresh Mixing Seawater S * L •> m L 9 ■ Primary productivity dominated by the pelagic community. Planktonic community dominated by diatoms; benthic community dominated by annelids in mixing zone and is a diverse mixture with annelids dominating in seawater zone. In St. Andrew Bay, chlorophyll a concentrations are medium in the mixing zone and unknown in the seawater zone. Tur- bidity, nitrogen and phosphorus concentrations are medium. Nuisance and toxic blooms, and anoxia and hypoxia, are observed. SAV spatial coverage is low. In the North Bay and East Bay mixing zones, chlorophyll a and nutrient concentrations increased, while turbidity de- creased. All other conditions are unknown. Physical and Hydrologlc Characteristics Estuarine Drainage Area (im£J1 ,160 Avg. Daily Inflow (cfs) 4,500 Estuary TWal Fresh Mixing Seawater Surface Area (m#> 98.3 52.0 45.3 Average Depth mi 11.9 8.6 17.0 Volume (bmooait) 32.6 12.5 21.5 I A relatively deep, Y-shaped embayment which includes St. Andrew, West, North, and East Bays. Minimal freshwater is supplied by Econfina Creek and Bear Creek (not pictured) across the Deer Point Lake Dam. Salinity structure determined by seasonal freshwater discharge from Econfina Creek and precipitation. Tide range is 1.3 ft near West Pass. Nutrients TWal Fresh Mixing Seawater M 50-100% * M 50-100"'= 9 ■ M 50-100% ♦ M 50-100% 9 ■ Elevated nitrogen occurs April to September. Elevated phosphorus occurs February /March to September. Dissolved Oxygen TWal Fresh Mixing Seawater 1 Y 9 ■ N ■ 10-25% I Y 9 ■ N 9 ■ 10-25% Biological stress observed over a high spatial extent of mixing zone and low extent of seawater zone. Low dissolved oxygen conditions occur in bottom waters periodically July to September. Water col- >:nn stratification contributes to a low extent to dissolved oxygen conditions. Minimum average monthly bottom dissolved oxygen concentxabens decreased in mixing zone from 1970-95. Key on page 23 35 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico Choctawhatchee Bay Ri - VOpMbo ycrmk Fr»«port V* «££**»** .jCFUT. .; .:. fl*. Gutf Mexico North Salinity Zones 0 4 8 □ Tidal Fresh ■ Mixing Zone ■ SeawaterZone Miles Algal Conditions 1 TulaJ Fresh Mixing Seawater I 9 ■ 9 ■ M M 50-100% 50-100% 1 H 9 ■ M * M H 50-100% 50-100% 50-100% j \ 9 ■ 9 ■ Y Y 1 ! | 9 ■ 9 ■ Y Y 1 Maximum Chl-a concentration* occur periodically in summer with a limiting factor of phosphorus. High turbidity occurs persistently in tidal fresh zone, and periodically March to September in mixing and seawater zones. Nuisance Anacystis, Atubaem mABidddphia spp. and toxic Amq/stis and Aiubaena spp. occur periodically in summer in mixing zone and nuisance Ckdophora and Btteromorpha spp. and toxic Gymnodinium breve and Gonyaulax momlata occur periodically in summer in seawater zone. Ecosystem/Community Responses Tidal Fresh Mbdno Seawater ■g— s NS ■ VL * VL 9 ■ ■_ Primary productivity dominated by the pelagic community. Planlctonic community dominated by diatoms in mixing and seawater zones, although blue-green algae previously dominated in mixing zone; benthic community is diverse tidal fresh zone, dominated by annelids in mixing zone, and speculated to be diverse in seawater zone Decrease in SAV •peculated to be due to increased suspended solids and coastal erosion. In Choctawhatchee Bay, chlorophyll a concentrations are medium, turbidity ranges from medium to high, and both nuisance and toxic blooms are observed. Nitrogen and phos- phorus concentrations range from low to medium. Anoxia and hypoxia are observed. SAV spatial coverage ranges from none to very low. In the mixing zone, turbidity concentrations and SAV spa- tial coverage decreased, while nitrogen and phosphorus con- centrations increased. Trends in the tidal fresh zone were unknown, as were all trends for dissolved oxygen. Physical and Hydrologlc Characteristics Estuarine Drainage Area (m?) 2,226 Avg. Daily Inflow (cfe;8,500 Estuary Tidal Fresh Mixing Seawater Surface Areapn/2) 130.2 1.0 119.1 10.1 Average Depth ft) 14.2 13.0 13.8 18.6 Volume (b&oncul$ 51.5 0.4 45.8 5.2 A relatively deep, and narrow lagoon consisting of Choctawhatchee Bay, Choctawhatchee River delta, and several smaller ernhayments. Separated from the Gulf of Mexico by a barrier spit along the southern shore. Vertical salinity stratification determined by seasonal freshwater discharge from Choctawhatchee River, tidal range is 0.6 ft near East Pass. Nutrients Tidal Fresh Mbdna Seawater 1 M 50-100% 9 ■ M 50-100% f> L 9 ■ | R 1 M 50-100% 9 ■ M 50-100% t L 9 ■ Elevated nutrient concentrations occur all year in tidal fresh zone and May to September in the mixing zone Increase attributed to non-point sources. Dissolved Oxygen TWai Fresh Mixing Seawater N 9 ■ Y 9 ■ N 9 ■ 10-25% Y 9 ■ Y 9 ■ Y ? 9 ■ 25-50% 25-50% Biological stress observed over 50 to 100 percent of tidal fresh and mixing zones and 25 to 50 percent of seawater zone. Conditions occur mostly in bottom waters June to October. Water column stratification is a moderate to highly significant factor in mixing zone. 36 Key on page 23 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico Pensacola Bay North t 4 Miles Salinity Zone* 0 Tidal Fresh ■ Mixing Zone ■ Sea water Zone Algal Conditions TWal Fresh Mixing Seawater In General Escambia River In General Bayou Texar I M 10-2S% 9 ■ L ... M 50-100% t E 0-10% ^ L H B ... M 50-100% o M 50-100% ... M 50-100% 4 [m | 50-100% B 1 N 9 N 9 ■ N 9 ■ N 9 ■ N 9 ■ 1 9 N 9 N 9 ■ N 9 ■ N 9 ■ N 9 ■ H In mixing zone, maximum Chl-a concentrations occur periodically March to August with a limiting factor of phosphorus. Nitrogen is limiting in Bayou Texar. Increase in Chl-a reported tor 1977-91 associated with point and non- point sources. Turbidity occurs throughout the year; decrease due to changes In point and non-point sources and increase attributed to point sources. Ecosystem/Community Responses ! TWalFresh Mbdng Seawater aaa E In General scambia River In General Bayou Texar E NS ... VL ... VL ... L* pi- VL * Primary productivity dominated by the pelagic community in Escambia River, Bayou Texar, and seawater zone, and by pelagic and benthic communities in mixing zone. Planktonic community is diverse; benthic community dominated by aquatic insects in tidal fresh zone, annelids in mixing zone, and is diverse in seawater zone. Decrease in SAV attributed to point and non-point sources. In Pensacola Bay, chlorophyll a concentrations range from low to hypereutorphic. The tidal fresh zone is mostly black- water; turbidity is moderate in the rest of the estuary. Nui- sance and toxic blooms are not observed. Nitrogen and phos- phorus concentrations range from low to high. Anoxia is not observed, but hypoxia is observed in the Escambia River and in the mixing zone. SAV spatial coverage is very low. Chlorophyll a concentrations increased to a high extent in the mixing zone. Turbidity decreased in the Escambia River but increased in Bayou Texar. SAV spatial coverage decreased to a high extent in Bayou Texar and in the seawater zone. Trends for nuisance and toxic algae, nutrients and dissolved oxygen are unknown. Physical and Hydrologic Characteristics Estuarine Drainage Area ("12)3,449 Avg. Daily Inflow (cis) 1 1 ,600 Estuary Tidal Fresh Mixing | Seawater Surface 190.1 In General Escambia R In Ganaral Bayou Texar 0.9 0.6 117.4 0.5 70.7 Average Depth m 12.7 n/a n/a n/a n/a 20.4 Volume (bUoncviQ 67.3 n/a n/a n/a n/a 40.2 A drowned river estuary and lagoon consisting of Santa Rosa Sound and Pensacola, Escambia, East, and Blackwater Bays. Separated from the Gulf of Mexico by Santa Rosa Island. Navigation channels are important conduits for salinity intrusion. Salinity structure is determined by. seasonal freshwater discharge primarily from the Escambia River. Tidal range is 3.2 ft near the mouth of the bay. Nutrients Tidal Fresh Mbdr SMwstor 1 In General Escambia River In General Bayou Taxar 1 M 1 50-100* 9 H 50-100% 9 M 50-100% 9 H 50-100% 9 ■ L 9 ■ I I M E 50-100% 9 H 50-100% 9 M 50100% 9 Ml? 50-100% L! 9 ■ M Elevated concentrations occur March to August except in Bayou Texar where they occur all year. Dissolved Oxygen Tidal Frath In General Escambia River N ? N ? N ? Y 10-25% 9 • In General Bayou Texar N N ? 10-J5N 9 • N ? N 9 ■ N 9 • Biological stress observed In 25 to 50 percent of tidal fresh zone, 50 to MX) percent of general mixing zone, and 10 to 25 percent of seawater zone. Conditions occur periodically June to September in bottom waters Water column stratification Is moderate factor in general mixing zone. Spatial coverage of conditions has not changed during 1970-95. Key on page 23 37 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico Perdido Bay Miles Algal Conditions Tidal Fresh M 25-50% # B N ft Y ? Mixing M 50-100% • H 50-100% Y ? 9 9 ■ ■ Seawater M 50-100% N N Maximum Chl-« concentrations occur periodically in summer with a limiting factor of light in adal fresh zone, nitrogen and phosphorus in mixing zone, and phosphorus in seawater zone. Turbidity occurs persistently all year. Nuisance Chlamydomonas and Aptumocapsa spp. and toxic Anaafstis and Anabaena spp. occur in summer. Ecosystem/Community Responses TWal Fresh Mixing Seawater ■ E NS • VL • L * ■_ Primary productivity is dominated by the pelagic community. Planktonic community is a diverse mixture; Denthic community dominated by aquatic insects in tidal fresh zone, annelids in mixing zone and is diverse in seawater zone. In Perdidio Bay, chlorophyll a, nitrogen and phosphorus concentrations range from low to medium. The tidal fresh zone is blackwater and turbidity in the mixing and seawa- ter is medium or high. Nuisance and toxic blooms and an- oxia and hypoxia are observed. SAV spatial coverage ranges from none to low. Nuisance blooms and nutrient concentrations increased in the tidal fresh zone. Chlorophyll a, turbidity and SAV re- mained unchanged. All other trends were unknown. Physical and Hydrologic Characteristics Estuarine Drainage Area (mP) 1 ,1 85 Avg. Daily Inflow (cfs) 2,200 Estuary Tidal Fresh Mixing Seawater Surface Area fm£> 50.0 0.4 48.3 1.3 Average Depth w 6.9 6.0 7.1 3.7 Volume (bifoncuft) 9.6 0.1 9.6 0.1 A small system consisting of Perdido Bay and several small creeks, separated from the Gulf of Mexico by Perdido Key. Direct exchange is restricted to Perdido Pass. Deep areas influence stratification by trapping saline bottom, waters and maintaining moderate to highly stratified conditions. Salinity structure also determined by seasonal discharge from Perdido River. Tidal range within bay is 1.6 ft Nutrients Tidal Fresh Mixing Seawater 1 M 50-100% ft M 50-100% 9 ■ L 9 ■ : ; ! S 1 M 50-100% ft M 50-100% 9 ■ L 9 ■ ■ Elevated concentrations occur April to October. Dissolved Oxygen TWal Fresh Mixina Seawater Y 50-100% 9 ■ N 9 ■ N 9 ■ Y 10-25% 9 ■ Y 25-50% 9 ■ N 9 ■ Anoxia and hypoxia occur periodically June to October in bottom waters. Biological strew occurs periodically June to September throughout water column in 10 to 25 percent of tidal fresh, 50 to 100 percent of mixing zone, and 25 to 50 percent of bottom seawater. Water column stratification is a highly significant factor in dissolved oxygen conditions. Minimum average monthly bottom dissolved oxygen decreased in tidal fresh wd increased in mixing and seawater zones. Duration and spatial coverage of low dissolved oxygen increased to a low extent in tidal fresh zone. 38 Key on page 23 NOAA's Estnarine Eutrophication Survey: Volume 4 - Gulf of Mexico Mobile Bay I \ Q Tidal Fresh ■ Mixing Zone ■ Sea water Zone Algal Conditions Tidal Fresh Mixing Seawater ■ ■ H 50-100% 9 ■ 9 9 ■ ■ M 50-100% H 25-50% 9 ■ ? ? M 10-25% M 50-100% 9 ■ N O 9 ■ ■ Y ? Y ? Maximum Chl-a concentrations occur periodically April to September in mixing zone and December to May in seawater zone, with co-limiting factors of nitrogen and phosphorus. Turbidity occurs throughout the year. Gymrwdinnm breve reported October to December 1996. Ecosystem/Community Responses Tidal Fresh M • Mixing VL Seawater NS Primary productivity is a mixture of pelagic, wetlands and SAV in the tidal fresh zone, and dominated by the pelagic community in the mixing and seawater zones. Planktonic community dominance is unknown; benthic community dominated by annelids. In Mobile Bay, chlorophyll a concentrations are medium. Turbidity ranges from medium to high. Nitrogen concen- trations range from low to medium and phosphorus con- centrations are medium. Nuisance blooms do not occur, but toxic blooms are reported. Both anoxia and hypoxia occur. SAV spatial coverage is very low in the mixing zone and medium in the seawater zone. SAV spatial coverage decreased in the tidal fresh zone. Trends are mostly unknown for the remaining conditions. Physical and Hydrologic Characteristics Estuarine Drainage Area (mP) 4,841 Avg. Daily Inflow (cfs)79,30Q Estuary Tidal Fresh Mixing O08W3l8f Surface Area (m?) 417.5 22.8 320.9 73.8 Average Depth (ft) 9.9 17.9 8.9 11.8 Volume (bUoncutO 115.2 11.4 79.6 24.3 A drowned river valley estuary consisting of the main bay, Mobile River, Tensaw River, and small embayments. Navigation channels are an important mechanism for salinity intrusion. Salinity structure is determined by Mobile River and the bay is moderately stratified throughout the year. Tidal range is 1.3 ft near Main Pass. Nutrients Tidal Fresh Mixing Seawater 1 M 50-100% 9 ■ M 50-100% 9 ■ L 9 ■ H 1 M 50-100% 9 ■ M 25-50% 9 ■ Ml 25-50% 9 ■ ■ Elevated concentrations occur all year in tidal fresh zone and January to May in seawater zone. Dissolved Oxygen Tidal Fresh Mbdna Seawater E N 9 ■ Y 9 ■ N 9 ■ 0-10% Yll? y| <> Y! 9 | 25-50% | I 25-50% [_' 10-25% Conditions occur periodically Jury to October in bottom waters. In mixing zone, anoxia occurs only in ship channel, but biological stress occurs throughout the water column. Minimum average monthly bottom dissolved oxygen concentrations did not change during 1970 to 1995. Key on page 23 39 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico East Mississippi Sound Algal Conditions Tidal Freeh MWna Seawater H 1 9 ■ 9 ■ M * M 50-100% 50-100% Esl 1 9 9 ■ H H 50-100% 50-100% 3 I 9 ■ 9 ■ Y 9 ■ \ i 9 ■ 9 ■ Y Y ■_ Maximum Saawater L O Primary productivity dominated by wetland and pelagic communities In tidal fresh, and speculated to be pelagic In mixing zone, and benthic/pelagic In seawater zone. Planktonic community speculated to be diverse in mixing and diatom dominated in seawater zone. Bentfuc community dominated by aquatic Insects in tidal fresh and annelids In mixing zone. SAV Increase reported for 199045; decrease in Bay Saint Louis and seawater zone due to alteration of watershed, freshwater inflow and non-point sources. In West Mississippi Sound, chlorophyll a and turbidity con- centrations range from medium to high. Nuisance and toxic blooms, and anoxia and hypoxia, are observed. Nitrogen and phosphorus concentrations range from low to high. SAV spatial coverage is low to very low. Chlorophyll a and phosphorus concentrations decreased. Turbidity concentrations, and nuisance and toxic bloom oc- currence, remained unchanged. SAV coverage decreased in Bay Saint Louis and the seawater zone, and increased in all other areas of the mixing zone. Physical and Hydrologlc Characteristics Estuarine Drainage Area (mP) n/a Avg. Daily Inflow (ctsjrjt Estuary Tktel Freeh Mbdng 8urfaos Area**) •354 0.3 W««S»n 8d. B«y ». UxM C*nb*l Sd Bk»J B*y 300.9 16.0 214J 11.8 91.5 Average Depth « n/a n/a n/a n/a rva n/a n/a Volume jNHMava nJa n/a n/a n/a n/a n/a n/a Western portion of Mississippi Sound, includes Bay St Louis delta complex, Biloxi River and Bay. In Western Sound, salinity structure is determined primarily by seasonal freshwater discharge from Pearl River and from Mississippi River through Lake Borgne and Pontchartrain. Vertically homogeneous salinity structure in Central Sound determined primarily by winds and tides. Salinity is lower in Western Sound than in Central or Eastern Sound, and it is highly variable. Tidal range is 1.7 ft near the main passes. Nutrients Tidal Freeh 9 9 Mfaano VMMStl Barsanioai Canrasn a*xe«y M •0-100% 9 M ■0-100% 9 M at too* 9 H BBw«0% 9 a L ? L ? M^ 11 * I !•*«*». 1 | I ttan L ? Elevated concentratioris occur June to August In Biloxi Bay and April to Septemtoo in rest of mixing zone. Decreases from 1985-95 attributed to changes in pomt sources. Dissolved Oxygen TWa! Fresh Mbdng 1 6»asis*af wiimi 8a B*rS*r*iaM cwasa. Btotami Y 9 a N 9 a N ? N 9 N 7 N ? 50-100% i 9 \h_ 9 a N ? Y 10-26% 9 a IMS* 9 a n-w. 9 a Biological stress observed in 10 to 25 percent of Western Sound and Bay St Louis, 25 to 50 percent of Central Sound and seawater zone, and 50 to 100 percent of tidal fresh zone. Conditions occur periodically July to September, throughout water column to tidal fresh zone, and In bottom waters in mixing and seawater aones. Water column stratification is a highly significant factor. Key on page 23 41 NOAA 's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico Lake Borgne Algal Conditions Tidal Fresh Mixing 9 9 ■ ■ H 50-100% 9 ■ Y ? Seawater High turbidity occurs throughout the year. Toxic Anabaena spp. occurred in 1.997. Ecosystem/Community Responses TWal Fresh Mixing Seawater ■ 1 VL 9 ■ ■ Primary productivity dominated by pelagic community. Planktonic community is speculated to be diverse; ben thic community dominated by annelids. For Lake Borgne, very little information was reported for existing conditions. Turbidity is high, SAV spatial coverage is very low, and no anoxia or hypoxia is observed. Trends for this system are unknown. Physical and Hydrologic Characteristics Estuarine Drainage Area (mi2)7J9Q Avg. Daily Inflow (cfs) 25,100 Estuary Tidal Fresh Mixing Seawater Surface mmam 272.1 272.1 Average Depth m 9.5 9.5 Volume (bUton cufl) 72.1 72.1 Located in the Mississippi River deltiac plain, with the Pearl River as major source of freshwater inflow. Salinities have been altered since construction of Mississippi River Gulf Outlet (MRGO) and other channels connecting the lake with Breton and Mississippi Sounds. Density currents within MRGO setup vertical stratification. Tidal range is 0.9 ft near mouth of the Pearl River. Nutrients Tidal Fresh Mixing Seawater 9 ■ 9 ■ 9 ■ 9 ■ Dissolved Oxygen Tidal Fresh Mixing Seawater ! N m N 9 ■ 42 Key on page 23 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico Lake Pontchartrain Algal Conditions 1 Tidal Fresh Mixing sw E Lake Maurepas Amite River Other Tributaries I L ft 9 ■ ft 9 ■ ft M 50-100% ■ I H lil 50-100% * H 50-100% * t H 50-100% * t H 50-100% * H 1 ! n ■ N ■ N m Y i ! | N 9 ■ N 9 ■ N 9 ■ Y i Maximum Chl-a concentrations in mixing zone occur periodically May to Jury with co-limiting factors of nitrogen and light Increase in Chl-a speculated to be due to population increase and diversion. Turbidity occurs all year with decrease attributed to cessation of shell dredging, and increase due to watershed alterations. Nuisance Anabaam circinelis, Kaiodinium rotundtm artd Microcystis aeruginosa. Toxic A nabaena areinalis occurs periodically May to July speculated to be result of spllhvater from Bonnet Carre diversion in March 1997. Ecosystem/Community Responses i Tidal Freeh Mbdng sw Lake Maurepas Amite River Other Tributaries 1 NS 9 ■ 9 ■ 9 • 9 ■ VL * ■ Primary productivity in take Maurepas and mixing xone is dominated by pelagic and wetland communities. Planktonic community Is diverse in mixing xone with blue-green algae dominating; benthic community dominated by mollusks and aquatic insects in Lake Maurepas and mollusks in mixing rone. SAV decrease due to shoreline alteration, epiphytes, and non-point sources. In Lake Pontchartrain, chlorophyll a concentrations range from low to medium and turbidity is high. Nuisance and toxic blooms, and anoxia and hypoxia, occur. Nitrogen con- centrations range from medium to high and phosphorus from low to medium. SAV spatial coverage is very low. Chlorophyll a, nitrogen and phosphorus concentrations in- creased. Turbidity increased in the tidal fresh zone and de- creased in the mixing zone. SAV spatial coverage decreased. Nuisance and toxic algae and dissolved oxygen conditions have remained unchanged in the mixing zone. Physical and Hydrologlc Characteristics Estuarine Drainage Area (mi2) 5,399 Avg. Daily Inflow (els) 10,700 Estuary Tidal Fresh Mbdng Seawatef Surface Areaf/n*) 748.2 Lake Maurepu Amite R. Other Trfce. 650.2 96.0 1.0 1.0 Average Depth ft> 11.1 n/a n/a n/a 10 J Volume (tMoncufO 231.5 n/a n/a n/a 195.8 Located in the Mississippi River delbac plain, consists of Lake Pontchartrain, Lake Maurepas, and Pass Manchac. The Amite-Comite and Tangipahoa Rivers are major sources of freshwater inflow. Eastern portion salinities have been altered since the construction of the Inner Harbor Navigation Channel. The Rigolets account for 60% of the tidal exchange Winds and density currents are a dominant farcing mechanism on salinity structure. Tidal range is 0.9 ft near mouth of Pearl River. Nutrients TWal Fresh Mbdng SW Lake Maurepas Amite River Other Tributaries n 9 ■ 9 ■ H 50-100% * Mf 50-100% M 50-100% E 9 ■ 9 ■ M 50-100% * * L * M 50-100% * ati Elevated concentrations observed all year in Amite River and February March in mixing rone. Dissolved Oxygen TWal Fresh Mbdng sw; Lake Maurepas Amite River Other Tributariee N 9 ■ X 50-100% 9 ■ 9 ■ 9 • Y 0-10% 1 Y 10-15% 9 ■ Y 50-100%" 9 ■ 9 ■ 9 ■ Y I 10^9% 1 In Lake Maurepas, low dissolved oxygen conditons occur periodically July to September in bottom waters. In Amite River, low dissolved oxygen conditons occur periodically July to September in bottom waters for anoxia and throughout water column for hypoxia. In mbdng zone, conditions occur June to October, anoxia occurs episodically at bottom, hypoxia periodically a: bottom, and biological stress periodically tftrougtout water eolutrm. Key on page 23 43 NOAA 's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico Breton/Chandeleur Sounds Q Tidal Fresh ■ Mixing Zone ■ Seawater Zone Miles In Breton/Chandeleur Sounds, turbidity concentrations range from medium to high. Nitrogen is low and phospho- rus is high in the mixing zone. Nuisance algal blooms are not observed in the seawater zone. Anoxia and hypoxia are observed. SAV spatial coverage is very low. All other condi- tions are unknown. SAV spatial coverage declined and anoxia and hypoxia were unchanged in the mixing zone. All other trends are unknown. Physical and Hydrologic Characteristics Estuarine Drainage Area (mi2) 2,491 Avg. Daily Inflow (cfs) 1 0,300 Algal Conditions Estuary Ttdaf Fresh Mixing Seawater Surface Area #1*9 1,662.4 781.6 880.8 Average Depth 0/ 8.9 5.6 12.2 Volume (bffloncutQ 412.5 122.0 299.6 Located in the Mississippi River deltaic plain. Consists of Breton and Chandekur Sounds with many small embayments and tidal marshes throughout. Pearl River is major source of freshwater inflow. Winds, density currents, and tidal influences are dominant forcing mechanisms on salinity structure, tidal range is 0.9 ft near mouth of Pearl River. Ecosystem/Community Responses Tidal Fresh NS Seawater Tidal Fresh Mixing Seawater E 9 ■ 9 ■ 9 ■ 9 ■ p| H 25-50% 9 ■ M 9 ■ 50-100% K 9 ■ 9 ■ N 9 ■ H 9 ■ 9 ■ 9 ■ 9 ■ Turbidity concentrations occur throughout the year. Nutrients VL * O Primary productivity is dominated by pelagic and wetland communities in mixing zone, and by pelagic community in seawater zone. Planktonk community dominance Is unknown; benthic community dominated by annelids in mixing zone and is diverse in seawater zone. Decrease in SAV attributed to hurricanes, tropical storms, and cold fronts. Tidal Fresh Mixing Seawater L 9 ■ 9 ■ 9 ■ H 9 ■ 9 ■ 9 ■ ? Nitrogen concentrations are nitrite and nitrate. Phosphorus is reported as total phosphorus. High phosphorus observed all year. Dissolved Oxygen Tidal Fresh Mixing Seawater N Y 9 ■ 0-10% N Y 9 ■ 10-25% Biological stress observed over 10 to 25 percent of mixing zone and 25 to 50 percent of seawater zone. Anoxic and hypoxic onditions occur periodically July to September, at bottom, except for biological stress, which occurs throughout water column in seawater zone. 44 Key on page 23 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico Mississippi River Lake Pontchartrain Miles Algal Conditions Tidal Fresh Mixing Seawater [ L M 50-100%| } 1 H 50-100% H 50-100% _ [ N 9 ■ N 9 ■ ,,! I N 9 ■ N 9 ■ ■ In mixing zone, maximum Chl-a concentrations occur periodically in summer with limiting factor of light. Turbidity occurs all year. Ecosystem/Community Responses Tidal Fresh Mixing Seawater ■ [ NS NS ■ Primary productivity is dominated by the pelagic community. Planktanic community is a diverse mixture; penthJc community dominated by annelids and crustaceans in tidal fresh zone and annelids in mixing zone. In the Mississippi River, chlorophyll a concentrations range from low to medium and turbidity is high. Nuisance and toxic blooms are not observed. Nitrogen and phosphorus concentrations are high. Anoxia and hypoxia do not occur and there is no SAV in the system. Trends were stable for all parameters except nuisance and toxic blooms, for which trends are unknown. Physical and Hydrologlc Characteristics Estuarine Drainage Area (mi2) -\ ,846 Avg. Daily Inflow (cfs) 464,400 Estuary Tidal Fresh | Mixing Seawater Surface Area (n&) 378.3 | 54.9 323.4 Average Depth m 23.1 60.4 17.6 Volume (bMoncun) 243.0 92.0 159.0 A river dominated estuarine system consisting of the Mississippi River and delta area with many small embayments and tidal marshes. As the largest single freshwater source in the U.S., the Mississippi River influences salinity distributions throughout the entire Louisiana and Texas Coast Tidal range is 1 .2 ft near the Southwest Pass. Nutrients Tidal Fresh H 50-100% H Mixing H 50-100% H 50-100% Seawater High concentrations occur all year. A high magnitude increase in nutrients due to non-point sources occurred from 1940-70 then leveled off. Dissolved Oxygen TWal Fresh Mixing Seawater 1 N N N N Biological stress periodically observed in up to 10 percent of mixing a on bottom from July to September. Water column stratification is a nighty significant factor. Key on page 23 45 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico Barataria Bay Salinity Zone* Q Tidal Freah ■ Mixing Zone ■ Sea writer Zone Algal Conditions TWai Fresh .' Mfcdna Saawater m 1 E ♦ H * e| 50-100% 50-100% I H H 50-100% 50-100% Y * 9 ■ 9 ■ •> ■ ■ 9 ■ 9 ■ 1 Maximum CMi-a concentrations occur throughout the year with limiting actors of nitrogen, phosphorus and silica In tidal fresh 2one, and nitrogen md phosphorus in mixing zone. Turbidity is high throughout the year. Mtusance blue-green algae occurs persistently. Increase in Chl-a and uiisance blooms due to point and non-point sources. Ecosystem/Community Responses "DM Fresh Mixing a~~>» mT t M ft L m N ■ 1 1 9 ■ 9 ■ 9 ■ 9 ■ N 9 ■ ■ Maximum CM-a ooricerttratlona occur periodically April to September with Iim- ttb^ factor of Ught to Atcrafaiya River, ligta Bght, nitrogen and phosphorus In mixing zone. High turbkflryisperaMastChl- • and turbidity trends attributed to non-poirtt source*. Nuisance and toxic spe- cies present in mixing zone, but unknown if a problem. Ecosystem/Community Responses TkjalFreaft In General Atchafalaya Rlvw H 4 NS 9 ■ NS ■ Seawater Primary productivity is pelagic and benthk in AtchaAiaya R., pelagic, benthic and emergent in tidal freah zone, and pelagic and emergent in mixing zone. Pe- lagic productivity declined in Atduualaya £ due to watershed alteratfeos. Flank- tome community (tommated by bjue-green algae; benmk immunity dominated byarthrc^x>dsmAtcha£tfaymR.,moflu*k»and»rth^ moUuaks and itmeUds In mixing zone Decreaae In SAV due to introduction of Hy ■ 6 N — Y 10-26% * n N — Y 26-50% ♦ N 9 ■ Biological stress observed in 50 to 100 percent est both zones. CcmdttfarsB occur pertodJcaUy June to October in bottom waters. Water column stratification, fe a highly significant factor. Increases in frequency, duration; and spatial coverage attributed to changes in non-potai sources. 48 Key on page 23 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico Mississippi/ Atchaf alaya River Plume In the Mississippi/ Atchaf alay a River Plume, chlorophyll a concentrations range from low to high. Turbidity ranges from low to medium. Nitrogen concentrations range from low to high and phosphorus from low to medium. Nuisance and toxic blooms occur. Hypoxia and anoxia are observed over this area. There is no SAV in this system. Chlorophyll a, nitrogen, phosphorus and hypoxia have in- creased and turbidity has decreased. Trends for nuisance and toxic blooms and, anoxia are unknown. Physical and Hydrologlc Characteristics Estuarine Drainage Area (mi2) n/a Avg. Daily Inflow (cfs) n/a Algal Conditions Tidal Fresh Mixing Seawater E H ft L 50-100% H M * L 50-100% ^E Y m N 9 ■ B * Y 9 ■ N 9 ■ Chl-a concentrations occur periodically February to May with limiting factors of nitrogen, light and silica and increase due to non-point sources. Medium turbidity occurs throughout the year with the decrease reported from 1982-97 due to increased productivity. Nuisance Sktletonema spp., and some toxic spedes occur in bloom proportion, but speculative if a problem to biological resources. Ecosystem/Community Responses I Tidal Fresh Mixing Seawater ■ B NS — NS — ■ Primary productivity has increased and is dominated by the pelagic community. Flanktonic community dominated by diatoms in spring and blue-green algae in summer; benthic community dominated by annelids in mixing zone and is diverse with annelids dominant in seawater zone. Non-point sources contributed to loss of benthic diversity in mixing zone. Estuary Tidal Fresh Mixing Seawater Surface Area (mfi) 12,256.0 8,672.0 3,584.0 Average Depth w n/a n/a n/a Volume (baton cut!) n/a n/a n/a A product of freshwater discharged from the Mississippi and Atchafalaya Rivers. During high inflow periods, a substantial volume of freshwater Is carried in a westerly direction via a semipermanent offshore current, causing nearshore waters to become diluted along the Louisiana coast. The diluted oceanic water is periodically adverted into estuaries along the Mississippi Deltaic Plain affecting salinity distributions and circulation within these estuaries. Nutrients Tidal Fresh Mixlno. Seawater H t L 25-50% M t L 25-50% Elevated nitrogen occurs February to April, phosphorus months unknown. Trends attributed to non-point sources. Dissolved Oxygen THaJ Fresh Mixing Seawater Y 9 ■ N 9 ■ 10-25% Y * Y 9 50-100% 50-100% Biological stress observed in 50 to 100 percent of mixing and seawater zones. In mixing zone anoxia observed July to August, hypoxia and biological stress April to September. Anoxia occurs at bottom, hypoxia in tower half of column, and biological stress throughout water column. In seawater zone, hypoxia occurs at bottom May to August and biological stress throughout water column April to September. Water column stratification is moderate to highly sigrdffcant factor in both zones. Key on page 23 49 NOAA 's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico Mermentau River Salinity Zones □ Tidal Fresh ■ Mixing Zone ■ Seawater Zone Algal Conditions Tidal Fresh Mixing H 60-100% N 9 ■ Seawater High turbidity occurs periodically and episodically December to January and ApriL Nuisance species are present, but not considered a problem. Ecosystem/Community Responses TkJal Fresh Mixing Seawater ■ NS — 1 Primary productivity is dominated by emergent wetlands. Planktordc and ben thfc community dominance are unknown. In Mermentau River, chlorophyll a concentrations are un- known. Turbidity and phosphorus are high and nitrogen concentrations are medium. Nuisance, toxic blooms, anoxia and hypoxia are not observed. There is no SAV in this sys- tem. Trends for turbidity, anoxia, hypoxia, nitrogen and SAV were unchanged; phosphorus concentrations decreased. Nuisance and toxic bloom trends are unknown. Physical and Hydrologic Characteristics Estuarine Drainage Area (mP) 1 ,391 Avg. Daily Inflow (cfs) 4,393 Estuary Tidal Fresh Mixing Seawater Surface Afea/mft 7.0 7.0 Average Depth 09 3.9 0.0 Volume 0.8 0.8 Extends from the head of tide at the Catfish Point Control Structure near Grand Lake to its terminus at the mouth. Impoundments built in early 1950's near Grand and White Lakes control salinity intrusion into those water bodies. Seasonal responses to freshwater discharge occur; in the unregulated lower Mermentau River. This estuary is most influenced by periodic control structure releases and frontal passages. Nutrients 1 Tidal Fresh Mixing Seawater [ M ? H ? * Concentrations reported are for nitrite and nitrate and total phosphor Medium nitrogen concentrations occur all year, high phosphorus occurs December and March through April. Decrease attributed to changes in non-point sources. Dissolved Oxygen ! Tidal Fresh Mixing beawater ■ N N 50 Key on page 23 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico Calcasieu Lake *^' CahMfcfl 113 % *1 7 . > ,„ 1x1— , ■ — j / [ North IVCamron }T*^~ ■ — -^ Salinity Zonct ' 0 Tidal Fresh I ■ Mixing Zone ■ Seawater Zone . Guliot Mexico Miles Algal Conditions TktelFresh Mixing Seawater B • H ■ * H t E 50-100% 50-100% H H H ? ? N 9 ■ Y N 9 ■ Y K ti n laximum Chl-o concentrations occur February to April with nitrogen as te limiting factor. High turbidity occurs in summer. Nuisance Anacystis wnlana occurs periodically in summer and toxic Alexandrium monilala and ivrocentrum mmimum occurs episodically August to October. Ecosystem/Community Responses I TWal Fresh NS Mixing Seawater Primary productivity is dominated by pelagic community in tidal fresh zone, and is emergent, pelagic and benthic in mixing zone. Planktonic community dominated by diatoms in tidal fresh zone and is diverse in mixing zone; benthic community dominated by annelids in tidal fresh zone and is diverse in mixing zone. Decrease in SAV attributed to alterations to watershed and point sources. In Calcasieu Lake, chlorophyll a and turbidity concentra- tions are high. Nuisance and toxic blooms, and anoxia and hypoxia, are observed. Nitrogen and phosphorus concen- trations range from medium to high. SAV spatial coverage is low. Chlorophyll a concentrations have increased. Turbidity, nui- sance and toxic blooms, phosphorus and anoxia have re- mained unchanged. SAV spatial coverage, nitrogen concen- trations and hypoxia decreased. Physical and Hydrologic Characteristics Estuarine Drainage Area (mP) -\ ,045 Avg. Dally Inflow (cfs) 6,300 Estuary TWal Fresh Mixing Seawater Surface AreaMJ 99.7 0.6 99.1 Average Depth m 9.4 26.3 9.2 Volume {bmoncuig 26.1 0.4 25.4 Consists of Calcasieu Lake and several secondary embayments. Receives majority of freshwater from Calcasieu River. Freshwater also flows between Mermentau and Calcasieu rivers by way of Calcasieu Lock. Several small navigation canals exist throughout the Calcasieu River basin. Seasonal flows influence the upper lake and Calcasieu River more than the lower estuary. Nutrients TWal Fresh Mixing Seawater 1 M * 0 IT • 50-100% 10-25% H 1 M H 50-100% 10-25% m Elevated nutrient concentrations occur March to May. Decrease* are attributed to changes in point sources. Dissolved Oxygen TWal Fresh Mbdng Seawater Y 9 ■ Y 0-10% 0-10% Y 9 ■ Y • 10-25% 25-50% Biological stress observed in 50 to 100 percent of tidal fresh and mixing zones. Conditions occur July to September throughout water column (anoxia on bottom in mixing zone). Minimum average monthly bottom dissolved oxygen increased to a low extent in seawater zone from 1985-95. Decreases in frequency, duration, and spatial coverage of hypoxia attributed to point source changes. Key on page 23 51 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico Sabine Lake Salinity Zones 0 Tidal Fresh ■ Mixing Zone ■ Sea water Zone Miles Algal Conditions Tidal Fresh Mixing Seawater Eg M M 25-50% 25-50% PI H H 50-100% 50-100% ■t I N Y ^- z 1 1 N N 1 ■ 1 Maximum Chl-d concentrations occur periodically April to September with light as the limiting factor. Turbidity occurs persistently throughout the year. Nuisance Gymttodinhm sanguinium occurs episodically May to July with increase speculated to be attributed to non-pomt sources. Ecosystem/Community Responses Tidal Fresh Mixing Seawater ■ [ NS VL ■ Primary productivity is dominated by the pelagic community in tidal fresh zone and pelagic and wetland communities in mixing zone. Plank tonic community dominated by blue-green algae in tidal fresh zone and diatoms in mixing zone; benthic community dominated by mouusks in tidal fresh zone and is diverse in mixing zone. In Sabine Lake, concentrations of chlorophyll a, nitrogen and phosphorus are medium and turbidity is high. Nuisance blooms occur but toxic blooms do not. Hypoxia is observed over a very low area. SAV spatial coverage is very low. Nitrogen and phosphorus concentrations decreased and nuisance blooms increased. For all other parameters, trends have remained unchanged. Physical and Hydrologlc Characteristics Estuarine Drainage Area (mP) 4,786 Avg. Daily Inflow (cfs) 1 7,200 Estuary Tidal Fresh Mixing Seawater Surface Area cm*) 102.2 3.2 99.0 Average Depths 8.2 15.0 8.1 sax 23.3 1.3 22.3 Consists of a relatively broad and shallow open bay, and a narrow, deep channel on the western side. Receives majority of freshwater from i Neches Rivers. depth) significantly influences circulation and salinity patterns. Since 1948, actuations approximately 20 reservoirs that have been constructed within the Nutrients Tkiaf Fresh Mixing • M 50-100% M 50-100% * M 50-100% _ M 50-100% * Medium concentrations occur all year. Decreases attributed to pointsources. Dissolved Oxygen I Tidal Fresh Mixing ■•:-;■, -■- jj N + N N * Y 0-10% Hypoxia observed periodically July to August in bottom waters. Biological stress observed in mixing zone periodically July to September throughout water column. Water column stratification is moderate factor contributing to hypoxic conditions. Decreases in frequency, duration, and spatial coverage attributed to changes in point sources. 52 Key on page 23 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico Galveston Bay V s HMMton J V/ V m ^^Qahreeton Gulf of Mexico Mrtt Salinity Zone* ^>hs7 ♦ 0 « 1 MU» 0 Tidal Fresh ■ Mixing Zone ■ Seawater Zone Algal Conditions Tidal Fresh Mixing Seawater | In General Trinity Rrvef Lower Qalveetor 1 Christmas Bay I M 50-100H ? M 50-100% ? M 60-100% 4- M 10-26% 4- * L ... ■ J H 5O-100W + H 60-100% * H 50-100% * H 60-100% 4 M 50-100% ... ! B 1 l!! ? N 9 ■ N * * Y ... N ? H H 1 N ? N ? Y -- * Y ... N ? H Maximum Chl-o concentrations occur episodically spring and summer with limiting factors of nitrogen in all zone* co-limiting with light in tidal fresh zone and phosphorus and light in mixing zone. Chl-o trends reported for 1989-% in mixing and 1970-95 in seawater zone. Turbidity occurs all year except in tidal fresh where it occurs episodically and periodically February to June. Decreases in Chi -a and turbidity associated with changes in point and non-point sources. Toxic Gonyaulax spp. occur episodically in summer. Ecosystem/Community Responses Tidal Fresh Mixing Seawater r In General Trtnly River .ower Oatveeton Chrlatmaa Bay I NS ... VL ? VL * NS ... L 4 ■_ Primary productivity dominated by pelagic community except Trinity River (salt marsh) and Christinas Bay (pelagk/benthic). PUnktomc community dominance unknown; benthk community dominated by annelids in tidal fresh and mixing zones, and mollusks in Trinity River and Christmas Bay. Decrease in SAV in mixing zone due to watershed alterations and physical disturbances, and in Christmas Bay from changes in point and non-point sources. In Galveston Bay, chlorophyll a concentrations range from low to medium. Turbidity ranges from medium to high, and nitrogen and phosphorus concentrations range from low to high. Nuisance and toxic blooms, and hypoxia and anoxia, are observed. SAV spatial coverage is very low. Trends for all parameters have decreased with the excep- tion of toxic blooms, which have remained stable. Physical and Hydrologic Characteristics Estuarine Drainage Area (7r)/2;4,441 Avg. Dally Inflow (cfe;15,414 Estuary TWal Fresh Mixing Seawater Surface Area cm*} 5S3.0 In General TrWty River 1.6 9.6 462.1 Lot CUtVeWtan CtAmtm* B*y 70.1 9.6 Average Depths 6.2 n/a n/a 6.4 n/a n/a Volume QMoncutt) 95.6 n/a n/a 82.4 n/a n/a Consists of several major embayments including Trinity, Galveston, East, West, and Christmas Bays. Receives majority of freshwater inflow from Trinity River. During high flow, Texas City Dike inhibits low salinity water from entering West Bay. Seasonal freshwater discharge from Trinity River determines salinity structure. Winds from frontal passages promote water column mixing. Tidal range is 1.4 ft near Bolivar Roads. Nutrients Tidal Fresh Trlnly River H 50-100% 4- M 50-100% ... .J±* M 50-100% ... Mixing M H 50-100% * Seawater Lower OaVsalon Crtrietrnee Bey 50-100% I ... 50-100% I ... Elevated concentrations in tidal fresh zone occur April to October and in mixing zone May to December. In Lower Galveston Bay, medium nitrogen occurs April to June, and medium phosphorus occurs all year. Dissolved Oxygen Tidal Fresh In General TrWty River X* N ... * N ... Mixing N & Y 10-25% i Seawaler lower OarVeelor Cmetmee Bay N ... N ... N ... N ... In tidal fresh zone, low dissolved oxygen occurs periodically June to September in bottom. In mixing zone, conditions occur July to September In bottom, episodically for hypoxia and periodically for biological stress. Water column stratification has moderate influence on dissolved oxygen conditions. Key on page 23 53 NOAA 's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico Brazos River Salinity Zone* □ Tidal Fresh ■ Mixing Zone ■ Seawater Zone Gulf of Mexico o Algal Conditions Tidal Fresh Mixing Seawater M 50-100% * M 25-50% 9 ■ ■ Pi H 50-100% H 50-100% H ? 9 ■ N N N 9 ■ N N Y 9 ■ Maximum Qd-«concentratlons occur periodJcaByto summer in tidal fresh zone, and episodically all year in mixing zone with light as limiting factor in both zones. Decrease m Chkt reported for 1990-94, Turbidity oceans throughout me year. One occurrence of toxic Gyrnnodinbm met was reported in the seawater zone (year uradentified). Ecosystem/Community Responses Tidal Fresh NS — Mixing VL — „ ywiiyBwjr.,, NS 9 ■ Primary productivity dominated by pelagic community in tidal fresh and mixing zones. Hanktonk community dominance is unknown; benthic community speculated to be diverse in tidal fresh zone and dominated by annelids in mixing and seawater zones. In Brazos River, chlorophyll a concentrations are medium and turbidity is high. Nuisance blooms do not occur and toxic blooms occur only in the seawater zone. Nitrogen con- centrations are medium and phosphorus ranges from me- dium to high. Anoxia is not observed but hypoxia occurs. SAV spatial coverage is very low. Trends for all parameters were stable with the exception of chlorophyll a concentrations, which have decreased in the tidal fresh zone. Physical and Hydrologic Characteristics Estuarine Drainage Area (mP) 2,792 Avg. Daily Inflow (cfs) 7,400 Estuary Tidal Fresh Mixing Seawater Surface Areafrti£> 18.1 1.1 16.9 0.1 Average Depth w 3.8 8.0 3.4 12.0 Volume 1.9 0.2 1.6 0.03 Includes Brazos and San Bernard Rivers, Cedar Lakes and the GIWW (Gulf Intercoastal Waterway). Floodgates block flow between Brazos River and the GrWW. Flows from San Bernard River are not as confined to river channel as Brazos River and may influence salinities over a larger portion of the estuary. Tide range is 0.6 ft near mouth of BrazosRiver. Nutrients [_ Tkial Fresh Mixing Seawater 1 M M 9 ■ 9 ■ 50-100% 50-100% J 1 H M 9 ■ 9 ■ 50-100% 50-100% ■ Elevated nitrogen concentrations occur all year in tidal fresh and December to July in mixing zone. Elevated phosphorus occurs April to June in tidal fresh and all year in mixing zone. Dissolved Oxygen I TWaJFfdsh Mixing Seawater N N 9 ■ 9 ■ N Y 25-50% 9 ■ 9 ■ Biological stress is observed in 10 to 25 percent of tidal fresh and 25 1< percent of mixing zone. Conditions occur periodically in bottom ' from June to September. Water column stratification is a highly i ' factor in mixing zone. 54 Key on page 23 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico Matagorda Bay Salinity Zones "1 Q lldil Fresh ■ Mixing Zone ■ Seawiter Zone X B tssj I / ^/ ^ «. A yiw VI Ub/ kJ^A iP^ *Jft Gulf of Mexico North 0 4 8 Miles Algal Conditions TWal Fresh Mixing Seawater i In General All subareas I H M 50-100% E 60-100% L K 50-100"* in cu ft) B5.8 0.2 n/a n/a n/a 19.9 — — — , — , A broad shallow Iagoonal system separated from the Gulf of Mexico try Matagorda Peninsula. Includes Colorado River, and Matagorda, East Matagorda, Lavaca, Carancahua, and Tres Palacios Bays. Receives majority of freshwater inflow from Colorado, Lavaca/Navidad and Ties Palacios basins. Vertically homogeneous conditions commonly exist in the open bay. Nutrients TWal Fresh Mbdna Seawater In General Subareas H H 50-100% 9 ■ H 10-25% ... H 10-25% Una Ej* vt M 50-100% E H 50-100% 9 ■ H 50-100% ... H 50-100% V t H 50-100% tf Concentrations are for total nitrogen and total phosphorus. Elevated nitrogen concentrations occur April to July plus October to November In seawater. Elevated phosphorus occurs March to August in tidal fresh, April to July and October to November in mixing and seawater zones. Increases in Bast Arm attributed to diversion channel plus changes in point and non-point sources. Decreases attributed to point source changes. Dissolved Oxygen I TWal Fresh Mixing SoAwatsr N N N 1 Y 50-100% 10-25% Y 10-25% Low dissolved oxygen conditions occur episodically August to October to bottom waters (throughout water column in mixing cone for biological stress). Water column stratification is moderate to highly significant factor. , Key on page 23 55 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico San Antonio Bay Q Tidal Fresh ■ Mixing Zone K ■ Seawater Zone ' Algal Conditions TWal Fresh Mixing Seawater 1 L H 10-25% M 50-100% H ft H 50-100% ft H 50-100% 50-100% N * Y * Y N Y Y Maximum Chl-« concentrations occur episodically all year with limiting factor of phosphorus speculated to be co-limiting with nitrogen. Turbidity occurs persistently all year with increases speculated to be due with point and non-point source*. Nuisance blue-greens occurred episodically for days in September of 1990 and toxic Gymnodhmtm meat occurred episodically uifaU of 1986. Ecosystem/Community Responses Tktal Fresh Mixing Seawater ■ 1 NS VL ^> L ■_ Primary productivity dominated by pelagic community. Planktonic and benthic communities are diverse Decrease in SAV associated with point and non-point sources. In San Antonio Bay, chlorophyll a concentrations range from low to high and turbidity is high. Nuisance and toxic blooms have occurred infrequently. Nitrogen and phosphorus con- centrations range from low to high. Anoxia does not occur, but hypoxia is observed episodically. SAV spatial coverage is low or very low. Chlorophyll a concentrations and nuisance and toxic bloom events have remained stable. Turbidity, nitrogen and phos- phorus concentrations have increased; SAV spatial cover- age has decreased. Trends for anoxia and hypoxia are un- known. Physical and Hydrologlc Characteristics Estuarine Drainage Area (mP) 1,556 Avg. Daily Inflow (cfs) 4,100 Estuary Tidal Fresh Mixing Seawater Surface Area^nfZ) 215.0 11.2 168.7 35.1 Average Depth ft} 4.3 4.0 4.3 4.3 Volume (bmancvfi) 25.7 1.2 20.4 4.2 Consists of San Antonio, Espiriru Santo and Mesquite Bays, and several secondary bays. Receives majority of freshwater Inflow from Guadalupe and San Antonio Rivers. Construction of navigation channels has modified circulation patterns. Freshwater inflow is retained in system for extended periods thereby lowering salinities. Meteorologic forcing can alter salinities by increasing saltwater intrusion from adjacent estuaries. North winds associated with cold fronts tend to increase water column mixing. Nutrients I Tidal Frash Mixing Seawater | H 50-100% ft H 25-50% L *■ 1 H 50-100% ft H 25-50% ft L • ft H High nutrient concentrations occur all year in tidal fresh zone and November to March in mixing zone. Dissolved Oxygen Tidal Fresh Mixing Seawati N ■ N 9 ■ N 7 ■ 1 N 9 ■ Y 10-25% 9 ■ N 9 ■ j Biological stress observed in 10 to 25 percent of mixing and zones. Conditioris occur April to October. Hypoxia occurs episc bottom, biological stress periodically mroughout the water column. Water I column stratification is a higmyslgrdf^^ 56 Key on page 23 NOAA's Estuarine Eutrophication Survey: Volume 4 - Gulf of Mexico Aransas Bay Algal Conditions Tidal Fresh Mixing In General Creeks M 50-100% H 50-100% H 50-100% H 50-100% Y ... Y - Y N Saawater M 10-25% H 10-25% N Maximum Chl-a concentrations occur episodically all year in Creeks, and April to August in mixing and seawater zones with limiting factor of nitrogen in oil zones. Turbidity occurs persistently. Nuisance Aureoumbra lagumnsis occurs episodically all year in Creeks and in summer in mixing zone. Toxic Gymncdimum breoe occurred in July of 1986 and 1991 in mixing zone, and occurs episodically in fall in seawater zone. Ecosystem/Community Responses Tidal Fresh JixkKL C reeks VL 9 ■ NS — Seawater M ^ Primary productivity is dominated by pelagic community in Creeks, is a mix of pelagic wetland and SAV in mixing zone, and wetlands and SAV m seawater zone. Planktonic community dominated by Avnoumbra laguntnsis in Creeks and by dia torn* in mixing and seawater zones; ben tbic community dominated by annelids. Decrease in SAV due to non-point sources, macroalgae, epiphyte*, and physical disturbance. In Aransas Bay, chlorophyll a concentrations range from medium to high and turbidity is high. Nuisance and toxic blooms are observed but anoxia and hypoxia are not. Nitro- gen and phosphorus concentrations range from low to me- dium. SAV spatial coverage ranges from very low in the mixing zone to medium in the seawater zone. SAV spatial coverage, nitrogen concentrations and hypoxia occurrences have decreased; phosphorus concentrations have increased. All other parameters remained unchanged. Physical and Hydrologlc Characteristics Estuarine Drainage Area (m?) 2,671 Avg. Daily Inflow (cfs) 1 ,000 Estuary TWal Fresh Mixing Seawater Surface Area