To determine the season concentration of mercury (Hg) in water and plankton in western Lake Erie, to assess the flux of Hg into the lake and to determine Hg bioaccumulation up the food chain.

Mercury (Hg) contamination and bioaccumulation up the food chain is considered one of the primary pollutant concerns within the Great Lakes. The introduction of Hg from the atmosphere is the most important regional source of Hg to most watersheds (Fitzgerald et al. 1998). Although Hg is introduced into aquatic environments through natural processes, about 60% of the atmospheric Hg deposition is thought to be due to anthropogenic sources (Fitzgerald and Mason 1996). Currently in the U.S., ~37% of anthropogenically introduced Hg is from waste combustion while ~41% comes from the burning of coal (Porcella et al. 1996). Modeling suggests that 85% of the Hg deposition to the Great Lakes is from anthropogenic sources (Shannon and Voldner 1995). Of the Hg input to Lake Erie proper, it has been estimated that 22% comes from direct atmospheric input while the majority (i.e. 78%) comes from tributary input, primarily from the Detroit River (Kelly et al. 1991). Eventually the atmospherically derived Hg that is deposited onto the landscape is transported into aquatic systems, where it can be deposited with aquatic sediments. If the sedimentary conditions are optimal, this inorganic Hg can be methylated, solubilized and bioaccumulated within the aquatic food chain (U.S. EPA 1999). Because the primary vector of Hg to humans is via fish consumption, the bioaccumulation of Hg within aquatic food chains is of major public heath concern, not just an academic curiosity. Hence there has been much interest in developing a better understanding of Hg biodynamics in water bodies where fish are taken for human consumption. Currently the U.S. EPA has issued state wide lake advisories for both Ohio and Michigan with regard to Hg in fish.

Although there have been many studies of Hg biogeochemistry in many aquatic systems, globally as well as in the Great Lakes region, surprisingly little real data exist on the concentration of Hg in Lake Erie.

The data from the samples collected will give a more comprehensive understanding of the distribution, dynamics and bioacculation of Hg through-out Lake Erie and the entire Great Lakes system. Managers and policy makers can then use this information to help estimate anthropogenic impact, ensure water quality and public health, and economic interests within the Lake Erie basin.

Will use ultra clean sampling and analytical techniques according to Gill and Fitzgerald (1985) and Bloom and Fitzgerald (1985) which are similar to EPA methods 1630 and 1631 for Hg and methyl-Hg determination.

We were able to sample on Lake Erie seasonally as originally planned. Although we had hoped to sample the rivers monthly, we were only able to maintain a sampling schedule of approximately every two months. 

Water and plankton (<202 and >202μm) were collected at two depths in July ’05, October ’05 and May ’06 in four basins in western Lake Erie.  River waters were also obtained from the Detroit and Maumee Rivers five times between September ’05 and July ’06.

Mean total Hg, dissolved Hg and particulate Hg in the western basisns were 2.0, 0.41 and 1.61 ng L^-1, respectively.  Detroit and Maumee River means of total Hg were 2.7 and 4.8 ng L^-1.  Bioaccumulation factors averaged between 3x10⁵ and 2.4x10⁶ for the various basins.  These are similar to what have been observed in other lakes.  The residence time of Hg in the western portion of fLake Erie calculated by us fits well with what is known about the behavior of other trace metals in the lake.