Mercury contamination and its effects in the everglades ecosystem

摘要

The Everglades is an ecosystem that is highly contaminated with mercury, in that concentrations in tissues of virtually all hight trophic level fauna exceed or are in the range of human consumption criteria, and of negative biotic effects. In this review the possible sources of mercury, the abiotic and biotic mechanisms of methylation and bioaccumulation, and an analysis of potential effects of current contamination levels on community dynamics, are presented. Sources of mercury include both atmospheric and local deposition, though the proportions of each are not clear. Rates of methylation of mercury are high, geographically variable, and probably sensitive to several abiotic factors, especially the availability of sulfur. Most effects of mercury on biota are likely to be of a sublethal nature. Evidence of effects is prominent for piscivorous birds and mammals, and recent research suggests that population dynamics of fishes and invertebrates also could be affected through endocrine disruption, behavioral changes, and embryonic mortality. The potential for this contaminant to alter community composition and biotic processes seems high, through either bottom-up or top-down mechanisms. This review demonstrates an immediate need for further work on sublethal effects of mercury at virtually all trophic levels, especially at ecologically relevant doses, and under conditions that include multiple natural stresses.