In many hydroelectric reservoirs across Canada, fish exhibit elevated mercury burdens. This is thought to occur due to the flooding of soil with water level fluctuations. Periods ofhigh water level may cause mercury from shoreline soil to be released into the water, which may make it available for methylation by sulfur-reducing bacteria in the sedimentand phytoplankton on plants. The amount of methylmercury produced during periods of high water level may depend on the topography of the shoreline; if the shoreline has agentle slope, more of its surface area would be covered during rises in water level than if the shoreline has a steep slope. I hypothesize that bays within a reservoir that have a gentle slope and a relatively large amount of vegetation (vegetation provides habitat for periphyton) will have more mercury than steeply-sloped bays with little vegetation. Totest this hypothesis, I have collected 10 each of the 3 most abundant fish (≤100 mm) from 3 bays in eastern Lake St. Lawrence (an impoundment reservoir with water fluctuations ≤2meters throughout the year) at Massena, NY. I will use stable isotopes to infer the trophic level and food web of each fish in order to determine spatial patterns of mercurydistribution. This study may improve our knowledge of mercury methylation patters in water reservoirs, and provide us with information necessary to properly manage the StLawrenceRiver water reservoirs.
Water physicochemistry and benthic macroinvertebrate communities in a tropical reservoir: The role of water level fluctuations and water depth
