As late as 1988, Cedar Creek was home to 27 species of freshwater mussels. But a decade later, only four of 26 species previously identified near Cedarville could be found; and near Waterloo, only six of 11 previously-identified species were found. In between, no living or freshly-dead mussel specimens of any species were located.

What happened to cause such a drastic decline? The USGS study that made these findings compared Cedar Creek with two other streams in the St. Joseph watershed: Fish Creek in Indiana and Ohio, and the West Branch of the St. Joseph in Michigan and Ohio, each of which showed declines in mussel diversity, but which still maintained greater diversity than Cedar Creek.


The study found that Cedar Creek had high concentrations of certain contaminants, especially phosphorus, at the sites where mussel concentrations were lowest. Although other factors such as stream-channel stability may also affect mussel populations, young mussels are especially vulnerable to contaminants in streambed sediments, making pollution the mostly likely explanation for the loss of mussel diversity in Cedar Creek. Source: United States Geological Survey, What Makes a Healthy Environment for Native Freshwater Mussels? Fact Sheet 124-00 (October 2000).