Chapter 3B: Mercury and Sulfur Monitoring, Research and Environmental Assessment in South Florida

SUMMARY Elevated concentrations of mercury and sulfur are evident in the Everglades. The highly bioaccumulative form of mercury, methylmercury (MeHg), is a concern due to the neurotoxic threat it poses for Everglades wildlife and humans who consume Everglades fish. Sulfur is a concern because (1) as sulfate, it promotes methylation of mercury; (2) as sulfate or sulfide it affects the biogeochemical cycling of numerous elements including phosphorus; and (3) as sulfide, it may be toxic to aquatic plants and animals. The very high mercury concentrations evident in fish in the Water Conservation Areas (WCAs) from the late 1980s to the early 1990s have declined substantially. Mercury levels in largemouth bass (LMB) (Micropterus salmoides) in the WCAs, however, remain generally above the proposed U.S. Environmental Protection Agency (USEPA) human health criterion for fish consumption for MeHg of 0.3 micrograms per gram (µg/g). In contrast to the mercury reductions in LMB in the WCAs, mercury levels in these fish have increased or remain unchanged at high levels in Everglades National Park (ENP or Park). Concentrations within the Holey Land Wildlife Management Area (Holey Land WMA) show a downward trend in starting in 2008, which is opposite of the monotonic increase observed in previous years. In the ENP and WCAs, LMB and sunfish (Lepomis spp.) mercury levels are both above USEPA wildlife and human consumption criteria. Across all water bodies within the Kissimmee Basin average LMB mercury levels range from 0.4 to 1.3 milligrams per kilogram (mg/kg), which is comparable to current levels found in the Everglades Protection Area (EPA) and the ENP. The similarity between largemouth bass levels in