Food web structure, mercury biomagnification and carbon pathways in an experimentally flooded wetland

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Embury, John David
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The objective of this thesis was to determine the role of food web structures and carbon sources in contributing to elevated organic mercury (OHg) in a flooded reservoir food web compared to a non flooded lake. Stable isotopes of carbon indicated the different sources of food energy that could potentially transfer OHg through the food web to top predators. Stable isotopes of nitrogen related trophic position of organisms to contaminant loading and allowed quantification of biomagnification. The components of the pelagic food webs in the Experimental Lake had higher concentrations of OHg relative to other food webs based on littoral benthic algal production of the Experimental Lake and food webs in the Control Lake. Consequently, the higher OHg concentrations in the pelagic food web were caused by higher OHg concentrations at the base of the pelagic food web. Consequently, this study found that impoundment affects mercury burdens in pelagic food webs more so than littoral/benthic food webs. (Abstract shortened by UMI.)