INTRODUCTION

This study was funded by the Integrated Natural Resources Science Program of the U.S. Geological Survey (USGS) to address the general issue of south Florida wetland ("Everglades") restoration. In 1995, as part of this effort, the USGS initiated the Aquatic Cycling of Mercury in the Everglades (ACME) project to evaluate Hg cycling processes (Krabbenhoft, 1996). A major goal of ACME is to determine fluxes, rates, and factors that affect Hg transport, cycling, and bioaccumulation. Work is conducted in close coordination with land management agencies such as the South Florida Water Management District (SFWMD), National Park Service (NPS), and U.S. Fish and Wildlife Service (FWS). Concern for the loss of wetland ecosystem (Everglades) integrity is the result of both elevated Hg levels (primarily methylmercury) in biota (especially high trophic level fish, alligators, and the endangered Florida panther) and changes in the major floristic composition of the region attributed to variations in nutrient levels in water (Loftus and Bass, 1992; Spalding and others, 1994; Sepulveda and others, 1995; DeBusk and others, 1994; Vaithiyanathan and Richardson, 1999).

Figure 1. The south Florida ACME study area. Regions of emphasis in the ACME project include the Water Conservation Areas, the Everglades Agricultural Area and Everglades National Park including Taylor Slough. Click on image to open larger version.

Our task (Geochemical Processes in Organic-Rich Sediments of South Florida–Mercury and Metals) within the ACME project seeks to define the sources, distribution, and processes involved in the biogeochemical cycling of major and trace elements, including Hg. The task has three sub-elements: (1) studies of the distribution of inorganic major and trace elements (with an attempt to define generalized baseline levels), (2) definition of the historical variation of elements in cores, and (3) assessment of the relation of element bioavailability and cycling to sediment diagenesis (Gough and Kotra, 1996). An understanding of the relation between organic-rich sediments and the concentration and speciation of elements of environmental importance is essential for water quality planners in developing long-term remediation and management strategies for the South Florida wetlands (Orem, 1997; Hurley and others, 1998). For example, such information is critical for making informed decisions regarding the regulation of water levels and in the evaluation of the effectiveness of constructed wetlands for remediation of contaminated waters. This project’s studies of the Taylor Slough portion of the Everglades system will provide a historical perspective of ecosystem conditions and variability.

This report focuses on studies conducted in the spring of 1996 in the Taylor Slough region of Everglades National Park (ENP, fig. 1). Taylor Slough, a natural watershed, extends north/south for about 27 km on the east side of ENP (Orem, 1997). A portion of the water that historically would flow in the Slough has been diverted into a major canal system (C-111, fig. 1). Nevertheless, the Slough is the primary source of freshwater to the shallow, and ecologically sensitive, eastern Florida Bay (McPherson and Halley, 1996). Users of these data are encouraged to contact the authors. Additional reports by the authors of these and other data are currently being prepared.

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