Date of Award

Spring 2021


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Document Type


Degree Name

Master of Science (MS) in Biology




Aquatic habitats impacted by anthropogenic activities such as mining can contain metal mixtures of nonessential and essential trace metals. The consequences of chronic exposure to metal mixtures on the life history of benthic organisms are unclear, as are the potential effects on host-associated microbial communities. I use an energy-budget based methodology to ask whether exposure to metal mixtures influences the life histories of freshwater fingernail clams (Sphaeriidae) and if fingernail clams are selecting a different microbial community if chronically exposed to metal mixtures than if in a site that is not impacted by metal pollution. Fingernail clams are small, cosmopolitan, sedentary, ovoviparous bivalves found at sediment-water interfaces. Previous work indicates that reproductive output is correlated with adult size in benign environments. Sampling four impacted and reference lake, which is not impacted by metal pollution, I measured clam somatic growth (adult shell length), brood production, tissue Cd levels, RNA:DNA and the clam tissue and lake water microbial communities. I found that clams living in a benign lake display significantly larger shell length and greater reproductive effort than clams living along a lake polymetal gradient. Additionally, the five lake water microbial communities were indistinguishable but clams from each of the five populations contained significantly different microbial communities. While I found the overall expected patterns amongst the life history data, I was not able to discriminate clearly amongst the four chain lakes with regards to bioenergetic partitioning, within-population clam growth and reproduction, and lake water microbial communities.