E.Coli and Coliform Bacteria Levels in Sediment of Lake Wingra
By: Ana Dvorak, Cortney Joosten, Dana Prochnow, Katie Thibaudeau
Bacteria levels (specifically E. coli) in Lake Wingra are closely monitored in the summer by the City of Madison Public Health Department to assess swimming safety. Vilas Beach, Madison’s most heavily used beach, is often closed to swimming because of elevated bacterial levels (Health). Geese feces contain high levels of bacteria, and it is believed that these feces contribute to the high levels in Lake Wingra. We sampled both water and lake sediment from five locations in Lake Wingra to determine the potential importance of sediment as a reservoir for E. coli. We found the levels of both total coliform bacteria and E. coli in lake sediments were much higher than those of the overlying water, supporting the idea that the sediment is serving as a reservoir for bacteria, perhaps arising from goose feces. We discuss the implication of our results for Lake Wingra water quality and the safety of its users. Our results should be a concern to the Madison Public Health Department, since they do not test lake sediments to determine if Lake Wingra and other lakes in Madison are safe for swimming.
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