Testing for effects of pollution on a snail-borne parasite in Michigan Lakes


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My thesis project focused on testing for potential effects of herbicides, specifically 2,4-D and glyphosate, on avian schistosome parasites in Michigan lakes. Avian schistosomes are a diverse group of snail-borne flatworm parasites that cause a rash called “swimmer’s itch” in humans. My project was part of a larger effort by Dr. Raffel’s lab team to measure the abundance of these parasites at 38 inland lake shorelines across Michigan. My own project focused on how pollutants affect the parasite’s intermediate hosts, snails. Chemical pollutants might affect snail populations by killing the invertebrate predators of snails or by influencing the growth rates of the snail’s food source (algae). We collected water samples from each site at two time points during the summer and brought them back to the lab for chemical analysis. We also measured population densities of snails and potential invertebrate predators of snails (i.e., crayfish), and measure algal growth rates using standard periphyton samplers and a chlorophyll assay. Ultimately, I hope my work will help to inform management efforts by local lake associations by determining whether and how pollution influences these parasites and their snail hosts.



Swimmer's itch, Herbicides, Pollutants, Snails, Periphyton