A Comparison of Mercury in Estuarine Fish between Florida Bay and the Indian River Lagoon, Florida, USA

Abstract

Concentrations of mercury (Hg) in fish were compared between two Florida estuaries, the Indian River Lagoon and Florida Bay. The objective was to determine if differences in Hg concentration exist and to attempt to relate those differences to sources of Hg. Five hundred and thirteen estuarine fish were collected and analyzed for Hg concentration. Fish species collected were black drum, bluefish, bonnethead shark, common snook, crevalle jack, gafftopsail catfish, gray snapper, Mayan cichlid, pompano, red drum, sheepshead, southern flounder, spadefish, and spotted seatrout. Analysis of variance of species-specific Hg data among the three defined regions of eastern and western Florida Bay and the Indian River Lagoon substantiated regional differences. Proximity to known anthropogenic sources of Hg appeared to be a significant factor in the distribution of Hg concentration among the fish collected. Sufficient numbers of crevalle jack, gray snapper, and spotted seatrout were collected to permit statistical analysis among regions. Hg concentrations in all three of these species from eastern Florida Bay were higher than those collected in the other two areas. A major fraction of the estuarine fish collected in eastern Florida Bay exceeded one or more State of Florida or U.S. Food and Drug Administration fish consumption health advisory criteria. In general, fish from western Florida Bay contained less Hg than those from the Indian River Lagoon, and fish from the Indian River contained less Hg than those from eastern Florida Bay. Crevalle jack from all areas and spotted seatrout from Florida Bay were placed on a consumption advisory in Florida. Detailed study of Florida Bay food web dynamics and Hg biogeochemical cycling is recommended to better understand the processes underlying the elevated Hg levels in fish from eastern Florida Bay. This information may be vital in the formulation of appropriate strategies in the ongoing South Florida restoration process.