Project Summary Sheet

Project: Mercury Transfer Through an Everglades Aquatic Food Web

Web Sites: http://everglades.fiu.edu/; http://www.fcsc.usgs.gov (see http://cars.er.usgs.gov/)

Location: Central Everglades

Principal Investigator: 1) William F. Loftus, 305.242.7835, bill_loftus@usgs.gov; 2) Joel Trexler, 305.348.1966, trexlerj@fiu.edu; 3) Ronald Jones, 305.348.3095, SERC@fiu.edu

Project Personnel:

Other Supporting Organizations: NPS and FFWCC. Mesocosm at ENP

Associated Projects: ATLSS (USGS study); Everglades Restudy (RESTORE); EPA REMAP, and USGS-ACME.

Overview & Status: The goal of this study was to identify the important routes and processes by which mercury is being passed to the top trophic levels in the Everglades system. There were three study objectives. The first described the food habits and trophic positions of Everglades marsh fishes, and the changes in diet associated with seasonal water-level fluctuations. The dietary patterns for the Everglades community were compared with data for tropical wetlands from the literature. The data were used to construct a food web leading to the fishes. The second segment correlated total mercury concentrations in Everglades fishes and invertebrates with their trophic positions to test for bioaccumulation. The third segment examined the effects of time-of-year and site hydroperiod on mercury levels of wild and caged mosquitofish at three pairs of locations. This project is completed and manuscripts are in preparation for journal submission.

Needs & Products: This is the first community-wide diet study for Everglades marsh fishes. The diet data have been used to describe the structure of the aquatic food web and its changes with water-level fluctuations. The statistical analyses indicated a strong positive correlation between the trophic position of both fishes and invertebrates and their mercury levels, demonstrating bioaccumulation with diet. Results demonstrated that mosquitofish is a good candidate for measuring in situ uptake of mercury in field cages. Patterns of mercury concentrations in wild and caged fishes at the same locations were similar across hydroperiod and season, but site hydroperiod did not explain much of the variation in mercury in the fishes. Loftus, W. F., J. C. Trexler, and R. D. Jones. 1998. Mercury Transfer Through an Everglades Aquatic Food Web. Final report to Florida Dept. of Environmental Protection. Tallahassee.

Application to Everglades Restoration: These data, combined with landscape-level studies of mercury geochemistry and patterns of concentrations in biota, will be useful as Performance Measures in the Restudy. The results were used in Phase 1 of the South Florida Mercury Program, in the development of the EPA BASS model of bioaccumulation, and in comparison with other studies in the Everglades.