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(108) Microbial Facilitation of Contaminant Transfer in the Lake Superior Aquatic Foodweb.
Hudson, Matt*,1, Cotner, James1, Swackhamer, Deborah1, 1 University of Minnesota, Minneapolis, MN, USA
ABSTRACT- A missing link in our understanding of contaminant transfer food web dynamics in Lake Superior has prompted a field and laboratory study. Good data on phytoplankton uptake and incorporation of PCBs exist, but not for the bacterial size fraction (<1um). In nutrient-poor, unproductive systems such as Lake Superior, heterotrophic bacteria <1um dominate the seston biomass and carbon flux. Their small size and large surface area (0.2-4m2/m3) allow them to reach equilibrium rapidly with the surrounding environment. At low bacterial growth efficiencies, like those found in nutrient-poor systems such as Lake Superior, a higher amount of organic carbon is processed per unit of organic biomass produced. These properties of bacteria make them potentially very important in accumulating organic contaminants such as PCBs and transferring them up the food web through the microbial loop, especially in an unproductive system such as Lake Superior. Because little is known about bacterial uptake of PCBs, both field and lab experiments are being conducted to determine bacterial accumulation and the role of bacterial growth efficiency in the accumulation of PCBs. Our main objective is to determine the impact of bacterial metabolism and biomass on pollutant bioaccumulation in Lake Superior.
Key words: polychlorinated biphenyls, microbial loop, bioaccumulation, aquatic foodweb transfer
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