How will Everglades restoration affect mercury risks?

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Are filter marshes likely to be significant new sources of mercury in water and fish?

The ENR Project as a prototype filter marsh 3,815-acre constructed wetland Expected to remove 75% of total phosphorus in Everglades Agricultural Area storm water runoff Discharge to Loxahatchee National Wildlife Refuge Consists of two parallel treatment trains each of which is comprised of a flowway cell and a polishing cell Three of the four cells are dominated by emergent macrophytes Cell 4 is actively maintained as a submerged aquatic vegetation system

(Click on image for larger version.)

(Click on image for larger version.)

Mercury monitoring Over 7,000 samples collected and analyzed for mercury since August, 1994 Sampling of inflow, outflow and interior culverts biweekly Sampling of interior marsh waters monthly Sampling of rainfall monthly Sampling of inflow, outflow, interior culvert and marsh fish quarterly Sampling of vegetation semi-annually Sampling of sediment annually

Results of mass budget studies Atmospheric deposition is a significant source pathway State standard was never exceeded Outflow lower than inflow 50% to 75% removal efficiency

Total Mercury Annual Mass Budget for the ENR Project (4-Yr Annual Average) (Click on image for larger version.)

Three year average of quarterly mosquitofish mercury concentrations with standard deviations. (Click on image for larger version.)

Results of fish studies Interior fish significantly lower than reference sites Cell 4 fish significantly higher than fish in other cells Methylmercury production higher in Cell 3 than in Cell 4 Cell 4 fish consume less vegetation and more invertebrates than fish in Cell 3 Methylmercury bioaccumulation factors higher in Cell 4 than in Cell 3

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