Electronic Thesis and Dissertation Repository

Degree

Master of Science

Program

Biology

Supervisor

Dr. Brian Branfireun

Abstract

Increasing mercury (Hg) concentrations in top predatory fish is concerning for human and wildlife health. This study examined the amount of Hg available to the food web of Lake Erie, and explored the role that two recently established non-native species, dreissenid mussels and round goby, have played in the trophic transfer of Hg to sport fish. A comprehensive sampling of total Hg (THg) and methylmercury (MeHg) within Lake Erie water, sediment and seston with high temporal and spatial resolution describes environmental concentrations. In addition, biotic THg and MeHg are quantified in benthic invertebrates and three fish species. A steep spatial gradient in aqueous and sediment Hg concentrations, decreasing from West to East, was not reflected in Hg concentrations in seston and benthic invertebrates. Mean seasonal THg concentrations in dreissenids (53.38 ± 3.99 ng/g) were consistently lowest amongst all invertebrates sampled, which ranged in mean THg concentrations from 102.56 ± 9.12 ng/g to 203.65 ± 19.02 ng/g. Fish THg concentrations showed little difference among basins, further reflecting biotic disconnect from the spatial gradient in abiotic THg and MeHg concentrations, and indicating similar food web biomagnification among basins. Low THg concentrations in both of the non-native species, relative to other invertebrates and fish, suggest they play a minor role in the bulk transfer of THg to top predatory fish.

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