(Des Moines)--Swimming is not recommended at 16 of Iowa's public beaches this weekend, according to the Iowa Department of Natural Resources.

The list includes Crandall’s Beach and Emerson Bay Beach in the Iowa Great Lakes.

Most of the beaches on this week's list showed high levels of E.Coli, which is an indicator of other potentially harmful bacteria in the water, or algal toxin.

The DNR tests 40-some beaches each week between Memorial Day weekend and Labor Day weekend. Sampling and testing happen during the week, with the results posted online Friday mornings.