Project Summary Sheet

Project: Integrated Biogeochemical Studies in the Everglades: Task 1 - Nutrients, Sulfur, and Organic Matter

Web Sites: http://sofis.usgs.gov; http://www.energy.er.usgs.gov

Location (Subregions & Counties): Total Everglades Ecosystem; Palm Beach, Broward, Miami-Dade, Monroe, Okeechobee, Martin, Highlands, Glades, Hendry, and Collier Counties

Funding (Source): USGS Place-Based Studies

Principal Investigator(s): William H Orem (borem@usgs.gov, 703.648.6273)

Project Personnel: H.E. Lerch (tlerch@usgs.gov, 703.648.6278); A.L. Bates (abates@usgs.gov, 703.648.6279); R.A. Zielinski (rzielinski@usgs.gov, 303.236.4719); C. Holmes (cholmes@usgs.gov, 727.803.8747 x3056

Supporting Organizations: USGS, SFWMD, FLDEP, ENP, USFWS-Loxahatchee NWR, USEPA

Associated / Linked Projects: Evolution of Everglades Tree Islands (Debra Willard, dwillard@usgs.gov, 703.648.5320), Groundwater Hydrology of the Everglades (Judson Harvey, jwharvey@usgs.gov, 703.648.5876

Overview & Status: This project integrates a number of individual but interrelated tasks that use geochemical approaches to address contaminant and water-quality issues in the south Florida ecosystem. Task 1 of this project focuses on biogeochemical processes and the sources and cycling of nutrients, sulfur, and organics in the ecosystem. It coordinates with other tasks to examine the complex involvement of nutrients, organics, and especially sulfur in methylmercury production and bioaccumulation. A major focus is on ecosystem responses to variations in contaminant loading (changes in external and internal loading in time and space), and how imminent ecosystem restoration may affect existing contaminant pools. Phase I studies showed that large portions of the northern Everglades are contaminated with sulfur and nutrients. Isotope tracer studies demonstrated that the sulfur and phosphorus originates from canals draining the Everglades Agricultural Area, and is consistent with a source from fertilizer. Sulfur entering the ecosystem from contaminated canal water plays a key role in regulating the amount and distribution of methylmercury production, a major contaminant issue in the Everglades. Other findings were: (1) Taylor Slough is not a major source of nutrients to eastern Florida Bay. (2) Phosphorus and nitrogen are enriched in post 1980’s sediments from Florida Bay, about the same time as the first observations of seagrass dieoff. (3) Drought and fire play a key role in remobilizing sequestered contaminants from sediments (especially sulfur), and stimulate methylmercury production in drought/fire-affected areas. Phase II emphasizes experimental studies to amplify and expand on phase I field results. This includes the use of environmental chambers (mesocosms), and laboratory studies (microcosms) to examine the effects of changing environmental conditions (increased contaminant loading, changes in hydroperiod, drought/fire) on contaminant concentrations and methylmercury production. Phase II work also includes contaminant (nutrients, sulfur, and organics) source, loading, sequestration, and cycling studies in portions of the ecosystem not previously targeted, including Lake Okeechobee and the Kissimmee River Basin, Big Cypress National Preserve, and Shark River Slough and the southwest coast.

Needs & Products: Geochemical results provide information crucial for developing conceptual models of contaminant loading and biogeochemical cycling in the ecosystem. Data and conceptual models provide a basis for mathematical models used in predicting ecosystem response to changing environmental conditions relating to contaminants, including those accompanying restoration. Products include refereed journal articles, USGS reports, synopsis reports, database, geochemical maps, and oral presentation of results.

Application to Everglades Restoration: Results provide critical elements for building conceptual, mathematical, and screening-level risk assessment models for the principal contaminants impacting water quality in the ecosystem. Project work provides CERP (3005-1; 3050-1,2,3,6,7,11; 3060-1; 3080-3,4,8,9,10), and GEER management quantitative information for decision-making on water quality and competing issues (e.g. hydroperiod). Water quality studies in Lake Okeechobee and the Kissimmee River Basin will assist in plans for Aquifer Storage and Recovery. Mesocosm and microcosm studies provide quantitative estimates of the maximum sulfur, nutrient, and mercury loads producing permissible levels of methylmercury in the ecosystem, and the effects of fire/drought on contaminant recycling from sediments and methylmercury production and bioaccumulation. Biogeochemical recycling studies will provide crucial information for estimating time requirements for ecosystem recovery from chemical contamination.