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projects > linking land, air and water management in the southern everglades and coastal zone to water quality and ecosystem restoration: task 2, sulfur and nutrient contamination, biogeochemical cycling, and effects > work plan

Project Work Plan

U.S. Geological Survey, Greater Everglades Priority Ecosystems Science (GE PES)

Fiscal Year 2006 Study Work Plan

Study Title: Integrated Biogeochemical Studies of Contaminants in the Everglades: Task 1 - Nutrients, Sulfur, and Organics
Study Start Date: 10/01/2000 Study End Date: 9/30/2006
Web Sites: http://sofia.usgs.gov; http://energy.er.usgs.gov/
Location: Total Ecosystem
Funding Source: USGS Greater Everglades Priority Ecosystems Science (GE PES)
Other Complementary Funding Source(s): (1) Assessment of Groundwater Input and Biogeochemical Characteristics in the Loxahatchee River and Floodplain Ecosystem (Mcpherson/Orem/Swarzenski; SFWMD Contract C-15349), (2) Sulfur Toxicity to Macrophytes in the Florida Everglades (I. Mendelssohn/LSU cooperator with Orem; FDEP), (3) Aquatic Cycling of Mercury in the Everglades: Linking Everglades Restoration, Land and Air Management (C. Gilmour/SI cooperator with Krabbenhoft and Orem, FDEP SP-632)
Funding History: Task 1-FY98; FY99; FY00; FY01; FY02; FY03; FY04; FY05; FY06;
Principal Investigator(s): William H Orem (borem@usgs.gov, 703.648.6273) and David P. Krabbenhoft (dpkrabbe@usgs.gov, 608.821.3843)
Study Personnel: H.E. Lerch (tlerch@usgs.gov, 703.648.6278); A.L. Bates, (abates@usgs.gov; 703.648.6279); M. Corum (mcorum@usgs.gov, 703.648.6488); R.A. Zielinski (rzielinski@usgs.gov, 303.236.4719); K. Simmons (ksimmons@usgs.gov, 303.236.7321); B. McPherson (bmcphers@usgs.gov, 813.975.8620)
Supporting Organizations: SFWMD, FLDEP, ENP, USFWS, USEPA, BCNP
Associated / Linked Studies: (1) Interactions of Mercury with Dissolved Organic Carbon in the Everglades (George Aiken, graiken@usgs.gov), (2) Development and Stability of Everglades Tree Islands, Ridge and Slough, and Marl Prairies (Debra Willard, dwillard@usgs.gov), (3) The Effects of Water Flow on the Transport of Suspended Particles and Particle-Associated Nutrients in the Everglades (Judson Harvey, jwharvey@usgs.gov), (4) Ecological Risk Assessment of Toxic Substances in the South Florida Ecosystem: Wildlife Effects and Exposure Assessment (Tim Gross, tim_s_gross@usgs.gov), (5) Historical Changes in Salinity, Water Quality and Vegetation in Biscayne Bay (G. Lynn Wingard, lwingard@usgs.gov), (6) Ecosystem History of the Southwest Coast-Shark River Slough Outflow Area (G. Lynn Wingard, lwingard@usgs.gov).

Overview & Objective(s): The south Florida ecosystem, including the Everglades, has been greatly impacted by many disturbances: over 35 percent of the original natural ecosystem has been converted to agricultural or urban use, much of the remaining wetlands are threatened by altered (unnatural) hydroperiods that result in too much water in wet years and drought and fires in dry years, over 2,250 km of canals dissect what was once continuum of wetlands and discharge contaminated water into the ecosystem, and all of these factors contribute to a steady loss of wildlife habitat (McPherson et al., 1976). Water quality remains one of the biggest issues facing restoration of the Everglades. The interrelated tasks of this project utilize a biogeochemical approach to examine several of the major water quality issues affecting this ecosystem (phosphorus, nitrogen, sulfur, organics and mercury loading), and the impacts on the biological systems that have resulted.

The scientific focus of the project is to examine the complex interactions of these contaminants (synergistic and antagonistic), ecosystem responses to variations in contaminant loading (time and space dimensions), and how imminent ecosystem restoration steps may affect existing contaminant pools. The Everglades restoration program is prescribing ecosystem-wide changes to some of the physical, hydrological and chemical components of this ecosystem. It remains uncertain, however, what overall effects will occur as these components react to the perturbations (especially the biological and chemical components) and toward what type of "new ecosystem" the Everglades will evolve. The approaches used will be extensions of previous efforts by the lead investigators, whereby we will enhance our abilities to address land management and ecosystem restoration questions. Laboratory experiments use incubated mini-cores (microcosms) to examine the effects of drought and fire on the recycling of contaminant pools from sediments and the resulting stimulation of microbial methylmercury production. Environmental chambers (controlled enclosures or mesocosms) in the ecosystem, and isotopic tracers are used to provide a more definitive means addressing specific management questions, such as:

  • What reductions in toxicity (methylation and bioaccumulation) would be realized if atmospheric mercury emissions were reduced by 75%?
  • What environmental factors control high methylmercury production in Stormwater Treatment Areas (STA's)?
  • Over what time scales will improvements to the ecosystem occur if nutrient and sulfur loading are reduced by implementation of agricultural best management practices and the STA's?
  • What are the toxic effects of sulfur contamination of the ecosystem?

Results of these investigations will provide critical elements for building ecosystem models and screening-level risk assessment for contaminants in the ecosystem, and this project will be linked to studies addressing ecosystem modeling (Reed Harris, Everglades and TMDL mercury modeling) and risk assessments.

The major objectives of this project are to use an integrated biogeochemical approach to examine: (1) anthropogenic-induced changes in the water chemistry (quality) of the Everglades ecosystem, (2) biogeochemical processes within the ecosystem affecting water chemistry, and (3) the predicted impacts of restoration efforts on water chemistry. The project uses a combination of field investigations, experimental approaches (mesocosm experiments in the ecosystem, and controlled laboratory experiments), and modeling to achieve these objectives. Integration of the individual tasks within the project is achieved by co-location of field sampling sites, and cooperative planning and execution of laboratory and mesocosm experiments. Results from all tasks within the project are archived within a single database for use in Decision Management GIS systems and ecosystem models. The needs of ecsosytem land and water managers to understand the sources of contamination, the ecosystem response to contamination, and the likely effects of restoration on water chemistry are the principal driving forces behind the work plan proposed in this study.

We propose to carry out work in the following areas: (1) water quality studies; (2) Field-scale and laboratory-scale experimental studies; and (3) coordinating input of geochemical results into ecosystem models and risk assessment studies being conducted by others. Our work tasks in these areas will be framed within the context of the Everglades restoration effort, and needs of ecosystem land and water managers to understand how the restoration may affect water chemistry, biology, and contaminant toxicity. The overall question we are addressing with this effort is, "Near term changes to the Everglades are certain, but what will be the ecosystem-level result of these changes and over what time scales can we expect these changes to occur?" Our previous work has answered many key questions regarding mercury, sulfur, and nutrient cycling in the Everglades, and redefined several previously existing paradigms about the general environmental chemistry of mercury. At the same time, however, our work has revealed several critical information gaps that we propose to address with this proposal.

The proposed work will employ a variety of investigative approaches to achieve these objectives, including: field studies, controlled experiments (both field and lab scale), and modeling. Contaminants of concern will include nutrients, sulfur, mercury, organic compounds, and other metals. Protocols for the collection of samples and chemical analysis developed during earlier studies will be employed in these efforts. Integration of the individual tasks within the project will be achieved by co-location of field sampling sites, and cooperative planning and contemporaneous execution of laboratory and field-enclosure experiments. Results from all tasks within the project will be archived within a single database, which will be made available through a Decision Support System (Web enabled) in a GIS framework to facilitate its use by ecosystem managers.

This project is designed to meet the needs of state and federal natural resource managers who need information on environmental pollutants in the Everglades, and what can be done to mitigate problems resulting from these pollutants. Many actions related to the Everglades Restoration project could potentially affect the expression of mercury loading in terms of its toxicity, including water levels, flushing rates, STA implementation for sulfur and nutrient reductions and the use of periphyton-based treatment cells, dissolved organic carbon releases, etc. Our field and lab experiments are designed to address many of the questions that surround how restoration plans may affect mercury toxicity. Mercury emissions reduction is a enforcement decision facing not only the State of Florida, but our Nation. Currently, we cannot say with great confidence whether the mercury levels observed in the Everglades are limited by the amount of mercury continually entering the system, or some other substrate. Although the existing data from ACME suggest that seasonal Hg loading from the atmosphere is concomitant with higher observed methylmercury levels, there are many other co-factors that could be causing this apparent correlation. Studies proposed herein will address this critical management decision.

This project addresses the major water chemistry issues currently affecting the Everglades: (1) eutrophication from excess nutrients entering the ecosystem, (2) sulfur contamination of the Everglades and its relation to mercury methylation, (3) mercury loading and bioaccumulation in the Everglades food web, and (4) other contaminants of concern, including organic substances and metals. Study results will provide critical elements for building ecosystem models and screening-level risk assessment for the principal contaminants impacting water quality in the ecosystem (nutrients/sulfur/mercury/organics). Results will provide CERP (3005-1;3050-1,2,3,6,7,11;3060-1;3080 3,4,8,9,10), and GEER management with quantitative information for critical decisions regarding water quality and other competing issues (e.g. hydroperiod).

Results on water quality studies from Lake Okeechobee, and the Kissimmee River Basin will assist in plans for Aquifer Storage and Recovery. Mesocosm studies will provide quantitative estimates of the maximum sulfur, nutrient, and mercury loads producing permissable levels of methylmercury in the ecosystem. Biogeochemical recycling studies will provide information that will assist in estimating the time required for ecosystem recovery from chemical contamination. Geochemical results will also be incorporated into conceptual, mathematical, and risk assessment models of the Everglades ecosystem.

Nutrient studies are focused on examining the sources of nutrients, and determining the rates of nutrient recycling and nutrient sinks in the ecosystem. Results will assist managers in determining the fate of excess nutrients stored in contaminated sediments. The sediment studies will also provide managers with information relevant to the effectiveness of planned remediation methods. For example, will the STA's be effective for long-term storage of nutrients removed from agricultural runoff water? Also, what will be the effect of increased hydrologic flow from the replumbing of the canal network in the Everglades on nutrient mobility and recycling in the wetlands? How will this replumbing affect nutrient flow to the mangrove areas and Florida Bay?

All of the scientific efforts related to mercury will be directly related to management questions surrounding how mercury toxicity will be affected by the restoration efforts. Studies of sulfur contamination relate directly to the issue of methylmercury production and bioaccumulation within the ecosystem, a threat to wildlife and people in south Florida. We will continue active participation in the South Florida Mercury Science Program, and provide our findings to relevant management agencies in verbal and written formats. We will solicit direct input from relevant management agencies on the design of our mesocosm and laboratory experiments. We will continue to be closely aligned with the Everglades Mercury Model development to assure field and laboratory studies are in concert with the model construction, coding, and the predictive questions being asked of the model. We will coordinate our studies with the risk assessment studies related to mercury. Finally, we intend to integrate all the information from this project into one consistent data base, and be in a Management Decision Support System that will be enabled with a GIS driver (ARC View).

Major products from the study include USGS Open-File Reports, articles in peer-reviewed international scientific journals, USGS Fact Sheets, abstracts and presentations at national and international scientific meetings and at client agencies, contributions to USGS and interagency synopsis reports, databases, and the electronic posting of reports and databases on the Web (sofia.usgs.gov). Input of geochemical data into ecosystem models and risk assessment studies will also be a principal product of this project.

Specific Relevance to Major Unanswered Questions and Information Needs Identified: (Page numbers below refer to DOI Science Plan.)

This study supports several of the projects listed in the DOI science plan. It provides information supporting the Comprehensive Integrated Water Quality Feasibility Study in the Landscape Science needs of the DOI Science Plan (p. 85), by examining links between water quality and ecosystem structure and function, identifying degraded parts of the ecosystem and quantifying links to contaminants (nutrients, sulfur, organics, and mercury), and investigating the impacts of ASR on the ecosystem. It also addresses risks to wildlife from soil-borne contaminants (sulfur, mercury, organics), through studies of the effects of dry/rewet cycles (Threats Associated with Rehydration of Agricultural Lands, p. 87; Predicting bioavailability of mercury (methylation) following inundation of dry land based on soil and water chemistry, p. 89) on methylmercury formation in STA's. The study supports the Arthur R. Marshall Loxahatchee NWR Internal Canal Structure Project by addressing the impacts of water quality (sulfur/nutrients/mercury) and water management practices on refuge resources, p. 40. The study addresses the Combined Structural and Operational Plan (CSOP) and the Water Conservation Area 3 Decompartmentalization and Sheetflow Enhancement by addressing the potential for increases in toxic contaminant loads (especially sulfur) and its ecological impact, p. 71.

Status: Major efforts during FY05 included the following research studies:
(1) Sulfur Toxicity Experiment - A major effort in FY05 was the continuation of a sulfur toxicity experiment in WCA 3A. This experiment tests the hypothesis that excess sulfate entering the Everglades from agricultural runoff has a significant effect on biogeochemistry, macrophyte growth, and the microbial community in the ecosystem. Sulfate entering the system diffuses into anoxic sediments and is reduced to sulfide. Sulfide toxicity has been shown in several environments to negatively impact freshwater aquatic plants. Current thinking is that excess phosphorus entering the ecosystem in agricultural runoff accounts for the change in macrophyte species (cattails displacing sawgrass) observed in WCA 2A. However, excess sulfate and subsequent buildup of sulfide in sediment porewater may also be a factor. A total of 30 mesocosms were placed in central WCA 3A in FY03; half in sawgrass and half in cattails. Dosing of these mesocosms with varying amounts of sulfate began in November 2003 and will continue through November 2006. Sampling of the mesocosms was conducted in November, 2004, and March and August 2005. Sampling includes geochemical studies of surface water, porewater, and sediments, and biological studies of macrophytes, microbial populations, and infauna. Collaborators include D. Krabbenhoft (USGS), C. Gilmour (Smithsonian), I. Mendelssohn (LSU), and G. Aiken (USGS).

(2) Mercury Methylation in Coastal Environments - A major unanswered question regarding water quality and contaminants in the south Florida ecosystem is how marine fish obtain the high levels of methylmercury observed. Is this methylmercury obtained from trophic transfer involving freshwater fish moving down coastal streams and marine species feeding on the freshwater species? Is methylmercury delivered from the freshwater Everglades to the coastal zone in runoff, and then incorporated in the coastal foodchain? Or, is methylmercury produced in coastal sediments, and thence transferred up the food chain to large predator species, popular with commercial and sport fisherman? These answers to these questions are unknown at this time. This work seeks to explore the biogeochemical dynamics of methylmercury in the coastal zone. Initial work is focused on a survey of coastal sites in Florida bay and the SW coast to examine the concentrations and biogeochemical processes influencing methylmercury production and bioaccumulation. In FY05, a total of 7 sites along the SW coast of Florida were sampled for surface water, pore water, and sediments. Samples were analyzed for mercury species, sulfur species, nutrients, FY06.

(3) Mercury Mesocosm Studies - This experiment begun in FY03 tested the effect of additions of sulfate, Hg, and methylmercury (MeHg) production in the Everglades. Task 1 of the project examines the sulfur, major anion, and nutrient geochemistry of the mesocosms. In conjunction with mercury studies conducted by others (Krabbenhoft-USGS and Gilmour-Smithsonian) and DOC work (Aiken-USGS), the study provides fundamental information on the major processes controlling MeHg production in the Everglades. Mesocosms were sampled in November 2003, March 2004, and September 2004. Results to date show that added sulfate stimulates MeHg production up to concentrations of about 15 mg/l, but depresses MeHg production above this concentration due to sulfide inhibition effects. This study was completed in FY05, and results presented at the Restoration Science Meeting held in Orlando in December 2004. A publication is expected in FY06.

(4) Big Cypress National Preserve (BCNP)- Analyses of samples from a preliminary water quality survey (December 2003) of were completed in FY05, including the first Hg and MeHg data for the Preserve. A follow-up field survey during the wet season (August 2005) was also conducted. The soil MeHg levels at some sites are rather high (0.1 to 8 ng/g MeHg), but the reasons for this are presently unknown. Sulfate concentrations in surface water from within BCNP are low, but some canals external to BCNP (notably L28), have relatively high sulfate concentrations. A concern is that movement of sulfate-contaminated canal water from L28 or other canals into BCNP to enhance water levels may have the unwanted effect of stimulating MeHg production. Results of the first survey were presented at the Restoration Science Conference in Orlando in December 2004. A paper on this work will be completed in FY06.

(4) Other - (a) Collaboration with Paul McCormick (USGS) of sulfur geochemistry of WCA 1 (Loxahatchee NWR). (b) Completed yearly monitoring of canal sites in EAA and the Everglades for sulfate concentration and sulfur isotope composition; 32 samples analyzed and put into database.

Recent Products:

(1) Louda, Orem et al. (2004) J. Coastal Res. 20, 448-463. (2) Orem (2004) Impacts of sulfate contamination on the Florida Everglades ecosystem. USGS Fact Sheet FS 109-03, 4 pp. (3) Kolker, Orem, Lechler (2003) Environmental Geology 43, 245-246. (4) Wingard G. Lynn, Orem William, and others (2004) U.S. Geological Survey Open File Report 2004-1312. (5) Wingard, Orem et al. (2004) Paleoecological, biochemical, and geochemical analyses of estuarine sediment cores: pieces in the south Florida ecosystem restoration puzzle. NE/SE Regional GSA Meeting, March 2004, Tysons Corner, VA, Abstract. (6) Bates, Orem, et al. (2004) Everglades water quality issues: II. Sulfur contamination and links to methylmercury production. NE/SE Regional GSA Meeting, March 2004, Tysons Corner, VA, Abstract. (7) Orem, et al. (2004) Everglades water quality issues: I. Phosphorus contamination. NE/SE Regional GSA Meeting, March 2004, Tysons Corner, VA, Abstract. (8) Gilmour, Krabbenhoft, Orem, and Aiken (2004) The influence of drying and rewetting on Hg and S cycling in Everglades soils. The 7th International Conference on Mercury as a Global Pollutant, September 2004, Lujubjina, Slovenia, Abstract. (9) Wingard G.L., Orem W.H., and others (2004) Natural Variability versus Anthropogenic Change: A case study in Biscayne Bay, Florida. First National Conference on Ecosystem Restoration, Lake Buena Vista, FL, December 2004, Abstract, p. 479. (10) Orem W., and others (2004) Sulfur Contamination in the Florida Everglades: Where Does it Come From, What is its Extent, What are Its Impacts, and What Can We do About it? First National Conference on Ecosystem Restoration, Lake Buena Vista, FL, December 2004, Abstract, p. 323. (11) Orem W., and others (2004) Water Quality in Big Cypress National Preserve: Present Conditions and Potential Impacts of Restoration Plans. First National Conference on Ecosystem Restoration, Lake Buena Vista, FL, December 2004, Abstract, p. 324. (12) Krabbenhoft D., Orem W., Aiken G., and Gilmour C. (2004) Mercury Contamination and Land-Management: The Convergence of Two Issues in the Everglades to Control Methylmercury Contamination at the Ecosystem Scale. Invited Keynote presentation at the 7th International Conference on Mercury as a Global Pollutant, September 2004, Lujubjina, Slovenia, Abstract. (13) Krabbenhoft, D., Orem, W., Aiken, G., Gilmour, C., Olson, M., DeWild, J., and Olund, S. (2004) Mercury contamination of the Florida Everglades: a convergence of external forces and natural ecosystem sensitivity. First National Conference on Ecosystem Restoration, Lake Buena Vista, FL, December 2004, Abstract, p. 235. (14) Swarzenski P., Orem W., McPherson B., and Baskaran M. (2005) Biogeochemical transport in the Loxahatchee River estuary, Florida: The role of submarine groundwater discharge. American Geophysical Union Meeting, New Orleans, LA, May 2005, Abstract. (15) Zielinski R.A., Orem W.H., and others (2005) Fertilizer-derived uranium and sulfur in rangeland soil and runoff: a case study in central Florida. J. Air, Water and Soil Sci., submitted. (16) Orem W.H., and others (2005) Assessment of groundwater input and water quality changes impacting natural vegetation in the Loxahatchee River and floodplain ecosystem, Florida. (17) Orem W.H., and others (2005) Synopsis Report: Sulfur Contamination in the Everglades and Sulfur Controls on Methylmercury Production. In: Mercury Synopsis Report (Krabbenhoft D.P., Ed.), USGS Publication, in review. (18) Zielinski, R.A., Orem, W.H., et al., Fertilizer-derived uranium and sulfur in rangeland soil and runoff: a case study in central Florida. J. Water, Soil, and Air (in review).

Planned Products: (1) Phosphorus on Everglades' Tree Islands Paper, USGS Open-File Report. (2) Joint papers (with Krabbenhoft and Gilmour) on (a) Mercury Mesocosm Studies, and (Environ. Sci. and Tch)., (b) Dry/Rewet Studies of Sulfur Remobilization and Methylmercury Production, (3) Biscayne Bay Nutrient History paper. (4) Big Cypress water quality paper. (5) Sulfur geochemistry of the Everglades paper.

WORK PLAN

Title of Task 1: Integrated Biogeochemical Studies in the Everglades: Task 1 - Nutrients, Sulfur, and Organics
Task Funding: USGS Greater Everglades Priority Ecosystems Science (GE PES)
Task Leaders: William H. Orem
Phone: 703-648-6273
FAX: 703-648-6419
Task Status (proposed or active): active
Task priority: High
Time Frame for Task 1: FY98; FY99; FY00; FY01; FY02; FY03; FY04; FY05; FY06

Task Personnel: H.E. Lerch (tlerch@usgs.gov, 703.648.6278); A.L. Bates, (abates@usgs.gov; 703.648.6279); M. Corum (mcorum@usgs.gov, 703.648.6488); R.A. Zielinski (rzielinski@usgs.gov, 303.236.4719); K. Simmons (ksimmons@usgs.gov, 303.236.7321); B. McPherson (bmcphers@usgs.gov, 813.975.8620)

Task Summary and Objectives: This study addresses the major water quality issues in the greater Everglades (nutrients, sulfur, mercury, organics), by investigating the sources, cycling, and sinks of these contaminants, and their effects on the natural resources within the ecosystem. Understanding the sources, sinks, cycling, and effects of contaminants is the first step in developing mitigation or resource management strategies to minimize the impacts of these contaminants on natural resources, while balancing other restoration priorities. Task 1 of this study (described here), focuses on nutrients, sulfur, and organics, and in collaboration with Task 2 also examines the complex interactions of these substances (especially sulfur) with mercury (synergistic and antagonistic). Emphasis is placed on ecosystem responses to variations in contaminant loading (changes in external and internal loading over time and space dimensions), and how imminent ecosystem restoration may affect existing contaminant pools and their impacts on natural resources in the ecosystem. The major objectives are to determine: (1) anthropogenic-induced changes in the water chemistry of the Everglades ecosystem, (2) biogeochemical processes within the ecosystem affecting water chemistry, (3) the predicted impacts of restoration efforts on water chemistry, and (4) the impacts of contaminants on natural resources in the ecosystem. The approach used includes a combination of field surveys, contaminant monitoring at key sites, experimental studies in the ecosystem using experimental chambers (mesocosms), and laboratory experiments using microcosms. The experimental field and laboratory studies are utilized to confirm conceptual models and hypotheses developed from field surveys. Study results will provide critical elements for building ecosystem models and screening-level risk assessment for the principal contaminants impacting water quality in the ecosystem (nutrients/sulfur/mercury/organics), and provide CERP (3005-1;3050-1,2,3,6,7,11;3060-1;3080-3,4,8,9,10), and GEER management with quantitative information for critical decisions, such as estimates of the maximum sulfur, nutrient, and mercury loads producing permissable levels of methylmercury in the ecosystem, the toxic effects of sulfur on macrophytes and other biota, estimates of the time required for ecosystem recovery from chemical contamination, and the effects of restoration on contaminant loads and impacts of contaminants. Results are incorporated into conceptual, mathematical, and risk assessment models of the Everglades ecosystem.

Work to be undertaken during the proposal year and a description of the methods and procedures:

(1) Sulfur Toxicity Experiment - This experiment will continue in FY06, with major sampling efforts in November 2005, and March and August 2006. The experiment tests the hypothesis that excess sulfate entering the Everglades from agricultural runoff has a toxicological impact on native macrophytes in the ecosystem. Sulfate entering the system diffuses into anoxic sediments and is reduced to sulfide. Sulfide toxicity has been shown in several environments to negatively impact freshwater aquatic plants. The current This experiment will test the hypothesis that excess sulfate entering the Everglades from agricultural runoff has a significant effect on macrophytes in the ecosystem. Sulfate entering the system diffuses into anoxic sediments and is reduced to sulfide. Sulfide toxicity has been shown in several environments to negatively impact freshwater aquatic plants. The current paradigm is that excess phosphorus entering the ecosystem in agricultural runoff accounts for the change in macrophyte species (cattails displacing sawgrass) observed in WCA 2A. However, excess sulfate and subsequent buildup of sulfide in sediment porewater may also be a factor. A total of 30 mesocosms were placed in central WCA 3A in FY03; half in sawgrass and half in cattails. Monthly dosing of these mesocosms with varying amounts of sulfate began in November 2003 and will continue through November 2006. Sampling includes geochemical studies of surface water, porewater, and sediments, and biological studies of macrophytes and microbial populations. Collaborators include D. Krabbenhoft (USGS), C. Gilmour (Smithsonian), I. Mendelssohn (LSU), and G. Aiken (USGS). A presentation on preliminary results from the experiment is planned for FY06 at an appropriate meeting. Probable publication in FY07. Work is closely coordinated with Task 2 and with work funded by Florida DEP. This experiment provides information supporting the Comprehensive Integrated Water Quality Feasibility Study in the Landscape Science needs of the DOI Science Plan (p. 85), by examining links between water quality and ecosystem structure and function, identifying degraded parts of the ecosystem and quantifying links to contaminants (nutrients, sulfur, organics, and mercury). It also provides CERP (3005-1;3050-1,2,3,6,7,11;3060-1;3080-3,4,8,9,10), and GEER management with quantitative information on the toxic effects of sulfur on macrophytes and other biota.

(2) Iron/Selenium Mesocosm Experiment - This experiment begun in FY05 is testing the effect of additions of iron and selenium on methylmercury (MeHg) production in the Everglades. Task 1 of the project examines the sulfur, major anion, and nutrient geochemistry of the mesocosms. In conjunction with mercury studies conducted by others (Krabbenhoft-USGS and Gilmour-Smithsonian) and USGS), the study provides fundamental information on the major processes controlling MeHg production in the Everglades. The initial experiment was begun with iron additions into mesocosms set up in WCA 3A in June 2005. Work is closely coordinated with Task 2 of this project (Krabbenhoft et al.). Work in FY06 will focus on analysis of samples collected in June and August 2005, and on additional sampling in FY06 (Fall, winter, and summer). This experiment provides information supporting the Comprehensive Integrated Water Quality Feasibility Study in the Landscape Science needs of the DOI Science Plan (p. 85), by examining links between water quality and ecosystem structure and function, identifying degraded parts of the ecosystem and quantifying links to contaminants (nutrients, sulfur, organics, and mercury). It also provides CERP (3005-1;3050-1,2,3,6,7,11;3060-1;3080-3,4,8,9,10), and GEER management with quantitative information for critical decisions, such as examination of the effects of iron and selenium contamination on levels of methylmercury in the ecosystem. Results are incorporated into conceptual, mathematical, and risk assessment models of the Everglades ecosystem.

(3) Big Cypress National Preserve (BCNP) - Results from a preliminary water quality survey in BCNP conducted in FY04 and indicate that some areas of BCNP have higher than anticipated methylmercury (MeHg) concentrations. Additional sampling was conducted in wet season (August 2005). While most of the Preserve has very low levels of sulfate, much higher concentrations are found in canals outside the Preserve, especially the L28. Restoration plans call for diverting water from the L28 into BCNP to increase water levels. However, the resulting increased sulfate load entering the Preserve in this canal water may have the unwanted effect of stimulating MeHg production and bioaccumulation here. Work in FY06 will include analysis of the samples collected in August 2005, and preparation of a preliminary report on the FY04 and 05 sampling in BCNP. We have proposed (BAA CESI/PES, FY07-09) to conduct further field and mesocsom studies of MeHg production in response to increased sulfate loads in BCNP, similar to studies we have already conducted in the central Everglades. Results will provide managers with information on the effects of diverting water of high sulfate concentrations into BCNP, so that costs and benefits of this planned diversion can be assessed. Coordination with Task 2, studies by Aiken (USGS), and outside collaborators (BCNP and Smithsonian) is critical. This experiment provides information supporting the Comprehensive Integrated Water Quality Feasibility Study in the Landscape Science needs of the DOI Science Plan (p. 85), by examining links between water quality and ecosystem structure and function, identifying degraded parts of the ecosystem and quantifying links to contaminants (nutrients, sulfur, organics, and mercury). It also provides CERP (3005-1;3050-1,2,3,6,7,11;3060-1;3080-3,4,8,9,10), and GEER management with quantitative information for critical decisions, such as estimates of the maximum sulfur, nutrient, and mercury loads producing permissable levels of methylmercury in the ecosystem, and the effects of restoration on contaminant loads and impacts of contaminants.

(4) MeHg Production in the Coastal Zone - Results of research conducted by this project in the Everglades, including field surveys, mesocosm studies, and laboratory experiments have provided a working model for MeHg production and bioaccumulation in the freshwater Everglades and similar environments. This model, however, does not appear to apply to coastal marine systems. Work in >FY05 included initial survey sampling at 7 sites in the SW coastal area of the greater Everglades (June 2005) to examine the mechanism by which MeHg is produced in the coastal zone of the greater Everglades. Work in FY06 will focus on analysis of the samples collected in June 2005, as well as additional survey work. Task 1 will specifically focus on the role of sulfur species in MeHg production in coastal environments, and how the process differs from the freshwater environment. Work on this will be closely coordinated with Task 2 studies. Initial work in FY05 will focus on field surveys, similar to our approach in the freshwater Everglades. This will be followed by experimental work in later years. The project provide CERP (3005-1;3050-1,2,3,6,7,11;3060-1;3080-3,4,8,9,10), and GEER management with quantitative information for critical decisions, such as estimates of the maximum sulfur, nutrient, and mercury loads producing permissable levels of methylmercury in the ecosystem and the impacts of these contaminants. Investigations aimed at understanding MeHg production and bioaccumulation in the coastal marine environment has been identified as a principal objective of future Hg research at a recent USGS mercury Workshop for DOI scientists and land managers.

(5) Other - (a) Collaboration with Krabbenhoft and Gilmour in surveys to establish MeHg hotspots in Everglades National Park. This addresses the Combined Structural and Operational Plan (CSOP) and the Water Conservation Area 3 Decompartmentalization and Sheetflow Enhancement by addressing the potential for increases in toxic contaminant loads (especially sulfur) and its ecological impact, p. 71. (b) Collaboration with Gilmour and Krabbenhoft on STA MeHg and sulfur surveys. This addresses risks to wildlife from soil-borne contaminants (sulfur, mercury, organics), through studies of the effects of dry/rewet cycles (Threats Associated with Rehydration of Agricultural Lands, p. 87; Predicting bioavailability of mercury (methylation) following inundation of dry land based on soil and water chemistry, p. 89) on methylmercury formation. (c) Collaboration with Krabbenhoft and Gilmour on follow-up dry/rewet studies of MeHg production. This addresses risks to wildlife from soil-borne contaminants (sulfur, mercury, organics), through studies of the effects of dry/rewet cycles (Threats Associated with Rehydration of Agricultural Lands, p. 87; Predicting bioavailability of mercury (methylation) following inundation of dry land based on soil and water chemistry, p. 89) on methylmercury formation. (d) We will continue collaboration with Paul McCormick on water quality in WCA 1 (Loxahatchee NWR), specifically focused on sulfur geochemistry and the paleoenvironmental chemical conditions in WCA 1. This supports the Arthur R. Marshall Loxahatchee NWR Internal Canal Structure Project by addressing the impacts of water quality (sulfur/nutrients/mercury) and water management practices on refuge resources, p. 40. (e) We will continue monitoring of canal sites for sulfate concentration and sulfur isotope composition. This addresses the Combined Structural and Operational Plan (CSOP) and the Water Conservation Area 3 Decompartmentalization and Sheetflow Enhancement by addressing the potential for increases in toxic contaminant loads (especially sulfur) and its ecological impact, p. 71.

Specific Task Product(s): (1) Synopsis Report: Sulfur Contamination in the Everglades and Sulfur Controls on Methylmercury Production (July 05), (2) Phosphorus on Everglades' Tree Islands Paper (September 05), (3) Two presentations at Restoration Science Meeting, Orlando (December 04), (4) paper on Sulfur and Mercury in Big Cypress National Preserve (May 05), (5) Fact Sheet on Big Cypress Water Quality (June 05), (6) Joint papers (with Krabbenhoft and Gilmour) on (a) Mercury Mesocosm Studies (June 05), and (b) Dry/Rewet Studies of Sulfur Remobilization and Methylmercury Production (August 05), (7) Biscayne Bay Nutrient History paper (January 05).



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