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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 > project summary

Project Summary Sheet

U.S. Geological Survey, Greater Everglades Science Initiative (Place-Based Studies)

Fiscal Year 2003 Project Summary Report

Project Title: Integrated Biogeochemical Studies in the Everglades, Task 1: Nutrients, Sulfur, and Organics

Project Start Date: 2000 Project End Date: 2005

Web Sites:,

Location (Subregions, Counties, Park or Refuge): Covers Whole Ecosystem, including Kissimmee River Basin, Lake Okeechobee, EAA, Water Conservation Areas and LNWR, BCNP, ENP, Florida and Biscayne Bays, SW Coast

Funding Source: USGS's Greater Everglades Science Initiative (PBS), Florida Dept. of Environmental Protection, South Florida Water Management District

Principal Investigator(s): William H. Orem

Project Personnel: H. Lerch, A. Bates, M. Corum, M. Beck, R. Zielinski, K. Simmons, C. Holmes, M. Marot

Supporting Organizations: Florida Dept. of Environmental Protection, South Florida Water Management District, USFWS Loxahatchee National Wildlife Refuge, Big Cypress National Preserve, Everglades National Park

Associated / Linked Projects: Int. Biogeochem. Task 2: Mercury (Krabbenhoft), DOC and Mercury Interactions (Aiken), Tree Islands (Willard), Water Quality - Biscayne Bay (Wingard), Ecosystem Histroy - SW Coast (Wingard)

Overview & Objective(s): This project integrates interrelated tasks that use geochemical approaches to address contaminant and water quality issues in the Everglades. Task 1 focuses on nutrients, sulfur (S), and organics. The objectives of Task 1 are to examine the complex interactions of these contaminants and mercury, ecosystem responses to variations in contaminant loading, and how imminent ecosystem restoration may affect existing contaminant pools. Field and experimental approaches are used, including the use of mesocosums, laboratory microcosm experiments, and isotopic tracers to address specific management questions. Earlier work showed that excess P and S enters the Everglades in canal discharge originating from the EAA. These contaminants have altered biotic assemblages within the ecosystem. The extent of S contamination in the Everglades was first documented by this project. Unnaturally high levels of S in the Everglades have increased levels of toxic hydrogen sulfide, and are a key control on toxic methylmercury (MeHg) production and bioaccumulation.

Status: Initial mesocosm studies of the impacts of S, DOC, and isotope tracer Hg additiona on MeHg production were completed in 2002-2003. Joint publication planned for FY04. More detailed mesocosm experiments are planned for FY04 and 05. Laboratory microcosm experiments in 2002-2003 examined the effects of drying and rewetting Everglades soils on S remobilization and MeHg production. Drying and rewetting the soils dramatically increased S in water and stimulated MeHg production. Results have major implications for management of STA's. Preliminary studies of S biogeochemistry and MeHg in SW Florida mangrove fringe and BCNP completed in 2003. Continued monitoring of canals for S contamination. Continued nutrient and S studies in drainages north of Lake Okeechobee.

Selected Recent & Planned Products: (1) Bates A.L., Orem W.H., Harvey J.W. and Spiker E.C. (2002) J. Environ. Qual. 31, 287-299. (2) Orem, W.H. et al., 2002, Chapter 5 In "Tree Islands of the Everglades" Van der Valk and Sklar (eds.), Kluwer Academic Publishers. (3) Orem, W., et al., 2003, Greater Everglades Ecosystem Restoration (GEER) Meeting, April 2003 (4) Krabbenhoft, D.P., Orem, W.H., Aiken, G., and Gilmour C., 2003, Greater Everglades Ecosystem Restoration (GEER) Meeting, April 2003. (5) Orem, W.H., 2002, Geological Society of Washington Meeting, Washington, DC, October 2002, (6) Orem, W.H. (2003) USGS Fact Sheet (planned for summer 2003) on Sulfur Contamination in the Everglades. (7) Joint Hg/S papers by ACME on Mesocosm studies and Dry/Rewet Experiments.

Relevance to Greater Everglades Restoration Information Needs: Results provide critical elements for building ecosystem conceptual, mathematical and screening-level risk assessment models for the principal contaminants impacting water quality in the Everglades. 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). Experimental studies provide quantitative estimates of the maximum sulfur, nutrient, and mercury loads producing permissible levels of methylmercury in the ecosystem and impacting biota. Biogeochemical recycling studies provide information that will assist in estimating the time required for ecosystem recovery from chemical contamination.

Key Findings:

  • Large portions of the northern Everglades are contaminated with S (up to 100x background) primarily originating from canal discharge of agricultural runoff.
  • Field and mesocosm studies showed that S contamination of the Everglades is a key factor controlling the intensity and distribution of MeHg production and bioaccumulation, and impacting redox conditions in the ecosystem.
  • Field and laboratory studies showed that Everglades soils impacted by drought/fire remobilized large amounts of S following rewet, stimulating massive MeHg production plumes, especially in new STA's.
  • U tracer studies showed that P contamination of the Everglades is linked to fertilizer use in the EAA and elsewhere.
  • Nutrient history studies showed that P contamination commenced @1920 in northern Everglades, but more recently in Biscayne Bay and Florida Bay.

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