Patterns of Contaminant Accumulation in Brook Trout from Streams Receiving Great Lakes Salmon Runs

Pacific Salmon (Oncorhynchus spp.) introduced to the Great Lakes bioaccumulate contaminants over their lifespan and deposit contaminated tissue in tributaries during spawning. This ecosystem linkage is a key factor regulating the concentration and pattern of persistent organic pollutants contaminants (POPs) in stream fish. However, uncertainty exists regarding salmon-mediated transport of heavy metals such as mercury (Hg) in the Great Lakes. We simultaneously compared salmon-mediated POP and Hg concentrations in resident Brook Trout (Salvelinus fontinalis) sampled from streams with and without salmon spawners across the upper Great Lakes. First, we assessed the relationship between POPs and Hg concentrations to determine if bioaccumulation patterns were similar. Second, we considered whether patterns of Brook Trout Hg concentrations in streams with salmon spawners varied similarly to POPs across Great Lakes basins. We found that Hg was positively related to POP concentration suggesting similar bioaccumulation processes associated with increasing fish length, age, and trophic position. Further, we found evidence for basin-specific variation in Brook Trout POP and Hg concentrations, suggesting fish in Lake Michigan streams, especially from reaches with salmon spawners, have elevated contaminant levels. Our research provides a framework for understanding and managing POP and Hg contaminant biotransport in the Great Lakes.