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FIGURE 4-15 Annual summaries of mercury concentrations in largemouth bass collected from canal and marsh sites in WCAs -1, -2, and -3 from 1989 to 2010. Note that mercury concentrations are normalized to a standard fish length of 356 mm. The red line indicates the EPA methyl mercury criterion of 0.3 ppm.

SOURCE: Axelrad et al. (2011).

al., 2010). At Shark River Slough, long-term measurements of mercury concentrations in largemouth bass show considerable year-to-year variability, with no significant trends (Gu et al., 2012).

Using the current understanding of the patterns and mechanisms driving fish mercury concentrations in the Everglades, one can speculate on the trajectories that fish mercury concentrations might take under various future management strategies. The two major drivers of fish mercury concentrations that might be affected by restoration management changes are: (1) agricultural sulfate inputs that control the production of methyl mercury and (2) phosphorus inputs that control fish mercury concentrations. Based on the available monitoring data, it appears that fish mercury concentrations are in quasi steady-state with respect to these drivers and that they respond relatively quickly to environmental change (~ years to a decade). If water and phosphorus inputs to the Everglades remain steady, then fish mercury concentrations should remain relatively constant through time. With improved hydrology (i.e., increased water discharge, decom-



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