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Evan Malczyk - Microbial Ecology and Metals Lab

Western Washington University, Bellingham, WA

Effects of iron addition on methylmercury production in everglades soils

 I spent the summer interning with the microbial ecology and metals laboratory at the Smithsonian Environmental Research Center.  This laboratory is currently researching environmental influences on mercury methylation in the environment.  Elemental mercury must first be methylated by bacteria living in the sediments before it is turned into a form that accumulates into living organisms.  Sulfate reducing bacteria are thought to be responsible for the majority of methylmercury production in the environment.  Methylmercury is many times more toxic than any other form of mercury, and is readily absorbed into animal and human tissue.  Its effects can be most harmful to young children and pregnant women.  The laboratory currently has 3 research projects underway; the Chesapeake Bay, the Everglades, and a small lake in the Boreal forest of Canada.  Each experimental site is providing valuable information in an effort to model mercury methylation and the many biological/geological/chemical processes that influence it.  I spent most of my summer helping the lab sample sediment at all three sites.  I learned many new methods relating to sediment and water sampling.    I also helped complete a project in the Florida Everglades where we looked at the effects of iron on mercury methylation.  Iron influences on mercury methylation are poorly understood.  Since sulfate reduction is one of the main influences on mercury methylation, we think that iron could interact with sulfur chemistry and change mercury methylation rates.  Past literature shows that iron may have an inhibitory effect on methylmercury production.  We conducted a mesocosm experiment in the north central everglades and examined the effects of three concentrations of iron on methylmercury production of a mercury tracer spike.  While many more analyses are pending, we completed data for pH, sulfide, Fe II/III, AVS/CRS, methylmercury.  We found no effect of either three concentrations of iron on methylmercury production.  This is possibly due to the low amount of sulfur and sulfate reduction in this ecosystem.  Since there is little sulfide for our added iron to sequester, there may have been no influences on sulfur chemistry and methylmercury production.  More analyses are pending from this experiment that will help us better interpret our results.

This project won best student poster at SETAC Northwest Regional Chapter Meeting in April 2006. 

Funding provided by National Science Foundation - REU