Project Summary Sheet

Study Title: Integrated Biogeochemical Studies in the Everglades: Task 1 - Nutrients, Sulfur, and Organics
Study Start Date: 10/01/2000   Study End Date: 9/30/2007
Web Sites: http://sofia.usgs.gov; http://www.energy.er.usgs.gov
Location (Subregions, Counties, Park or Refuge): Total Everglades Ecosystem
Funding Source: USGS Greater Everglades Priority Ecosystems Science (GE PES) Initiative
Principal Investigator(s): William H Orem (borem@usgs.gov, 703.648.6273)
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
Associated / Linked Studies: (1) Integrated Biogeochemical Studies in the Everglades: Task 2 - Mercury Cycling and Bioaccumulation (David Krabbenhoft, dpkrabbe@usgs.gov), (2) Interactions of Mercury with Dissolved Organic Carbon in the Everglades (George Aiken, graiken@usgs.gov), (3) Development and Stability of Everglades Tree Islands, Ridge and Slough, and Marl Prairies (Debra Willard, dwillard@usgs.gov), (4) The Effects of Water Flow on the Transport of Suspended Particles and Particle-Associated Nutrients in the Everglades (Judson Harvey, jwharvey@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): 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 focuses on nutrients, sulfur (S), and organics, and in collaboration with Task 2 also examines the complex interactions of these substances (especially S) with mercury (Hg). 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 are first developed into conceptual models, and then provide critical elements for building ecosystem models and screening-level risk assessment for the principal contaminants impacting water quality in the ecosystem (nutrients/S/Hg/organics), and provide CERP and GEER management with quantitative information for critical decisions, such as estimates of the maximum S, nutrient, and Hg loads producing permissible levels of methylmercury (MeHg) in the ecosystem, the toxic effects of S 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.

Status: Research conducted during phase 1 of this study (1995-2000) focused primarily on field surveys to establish: (1) the natural, background levels of nutrients, S, organics, and Hg in the ecosystem, (2) the extent of contamination from these substances in the environment, (3) sources of these contaminants, (4) major sinks of these contaminants, and (5) biogeochemical processes in the ecosystem affecting contaminants. A major finding from phase 1 studies was the discovery of extensive S contamination of the Everglades originating from EAA canal discharge, and links between S contamination and MeHg production and bioaccumulation in the ecosystem (Goldilocks Hypothesis). Sulfur contamination has an arguably greater impact on the ecosystem than phosphorus. Phase 2 studies, beginning in 2000, took a more experimental approach using environmental chambers (mesocosms) and laboratory studies to establish the impacts of contaminants on biota, and to quantify the concentrations of S (sulfate and sulfide) producing specific levels of MeHg production and bioaccumulation in the Everglades. This data will be useful for managers in determining what levels of S contamination produce acceptable levels of MeHg in Everglades' biota. Sulfur contamination may also represent a threat to macrophytes and other organisms in the ecosystem through buildup of toxic sulfide in sediments. Mesocosm studies are currently underway (FY04-FY07) to evaluate the impact of sulfide on soil redox, macrophyte growth, soil biota, and nutrient recycling. Laboratory studies have been used to show the effects of dry/rewet cycles on S and nutrient remobilization from organic soils, and MeHg production and bioaccumulation. Limiting dry/rewet cycles in critical areas can be used as a management tool to reduce levels of MeHg in biota. Work is also underway to work with modelers for incorporation of a S module in the mercury cycling model. This will be critical for assessing the impacts of restoration efforts to restore sheet flow to the Everglades (with resulting higher S loads to the ecosystem) on MeHg production and bioaccumulation, especially in Everglades National Park (ENP). Work in FY07 will begin to examine the biogeochemical processes important in MeHg production in the coastal marine zone of Florida Bay and the Gulf coast, where high levels of MeHg are found in fish. Task 1 work will focus on the role of S and biogeochemical processes in coastal sediments in MeHg production.

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 (2006) Fertilizer-derived uranium and sulfur in rangeland soil and runoff: a case study in central Florida. J. Air, Water and Soil Sci. 176: 163-183.
(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 (2006) 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) Gilmour C., Orem W, Krabbenhoft D., Roy S., Mendelssohn I (2006) 2006 SFER Appendix 3B-3 Preliminary Assessment of Sulfur Sources, Trends and Effects in the Everglades.
(19) Gilmour C., Krabbenhoft D., Orem W., Aiken G., Roden E. (2006) 2006 SFER Appendix 3B-2 Status Report on ACME Studies on the Control of Hg Methylation and Bioaccumulation in the Everglades.

Planned Products: (1) Orem W. and others (2007) Sulfur controls on mercury methylation in the Florida Everglades (2) Joint papers (with Krabbenhoft and Gilmour) on (a) Mercury Mesocosm Studies, and (b) Dry/Rewet Studies of Sulfur Remobilization and Methylmercury Production, (3) Big Cypress water quality paper.

Specific Relevance to Information Needs Identified in DOI's Science Plan in Support of Ecosystem Restoration, Preservation, and Protection in South Florida (DOI's Everglades Science Plan) [See Plan on SOFIA's Web site: http://sofia.usgs.gov/publications/reports/doi-science-plan/]:

This study supports several of the projects listed in the DOI science plan. The study supports 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 (S, 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 MeHg formation in STA's. The study supports the Arthur R. Marshall Loxahatchee NWR Internal Canal Structure Project by addressing the impacts of water quality (S/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 S) and its ecological impact, p. 71.

Key Findings:

1. Sulfur from EAA canal discharge contaminates about 1/3 of the Everglades at levels up to 100x background, and is linked to high MeHg production and bioaccumulation in the ecosystem. Achieving acceptable levels of toxic MeHg in Everglades' fish and wildlife will require reduction of both mercury and S contamination, including limits on S use in the EAA.
2. Recent decreases in MeHg in fish in the north and central Everglades is closely linked to decreases in sulfate concentrations here. Decreases in Hg emissions may also be a factor. Excess sulfate is now diverted to ENP as part of restoration efforts, and may trigger increased MeHg production and bioaccumulation in ENP. Planned diversions of canal water may also impact MeHg production and bioaccumulation in BCNP.
3. Dry/rewet cycles in the Everglades play a major role in remobilizing S and nutrients from organic sediments, and stimulating methylmercury production and bioaccumulation. Effective management of dry/rewet cycles is important for minimizing MeHg levels in Everglades fish and wildlife.
4. Excess sulfate entering the ecosystem stimulates microbial sulfate reduction and production of toxic sulfide in Everglades soil, impacting redox conditions, nutrient recycling, and possibly macrophytes and infauna.