From about Memorial Day through Labor Day, the Iowa Department of Natural Resources (DNR) conducts weekly monitoring of bacterial pollution in Iowa’s 39 state park beaches.
The DNR analyzes water samples from the beaches for certain one-celled microorganisms, known as indicator bacteria, that are visible only under a microscope. High levels of E. coli, a common indicator bacteria, indicate feces is in the water. Livestock are the most common source of feces in surface waters in Iowa.
These indicator bacteria are commonly used by state environmental agencies and by the U.S. Environmental Protection Agency to determine the suitability of beaches for swimming-type uses…