With Iowa’s swimming season still in prime time, 15 state parks beaches have posted warnings due to high levels of fecal bacteria or toxins from algae. Saylorville Lake’s beaches are closed because of blue-green algae, which can emit toxins.

The Iowa Department of Natural Resources recommends against swimming at these state-park beaches, which either had high levels of bacteria this week or have averaged high readings over the past month: McIntosh Woods at Clear Lake, Backbone, Brushy Creek, Rock Creek, Geode, Lacey-Keosauqua, Lake of Three Fires, Green Valley, Springbrook, Wapello, Macbride, Ahquabi, Gull Point on West Okoboji Lake, Black Hawk and Darling.

Levels can change by the hour. The most recent readings were from samples taken earlier this week. Because readings can change quickly, and often improve if the sun has been out, the state has chosen only to warn swimmers, without closing the beaches.

High levels of bacteria can mean the presence of organisms that can give people intestinal illnesses or skin rashes. The toxic algae can cause similar problems plus neurological problems, and can be fatal to pets and livestock. Swimmers are advised to stay out of water with a foul odor and areas that are covered with scum.

The Iowa Department of Public Health recommends swimmers bathe soon after they finish swimming. Avoid swallowing the lake water.

Some of the readings were extremely high. Lake of Three Fires was running 55 times the swimming limit for E. coli. Lake Macbride was 72 times the limit.

See the statewide readings here.