Lake Macbride State Park, a popular Johnson County swimming and boating spot, had high enough bacteria levels for the state to issue no-swim advisories 12 of 15 weeks of the summer.
The Iowa Department of Natural Resources issued 111 beach advisories for Iowa’s 39 state park beaches from Memorial Day weekend through Labor Day. This is up slightly from 96 advisories in the summer of 2017.
The bulk of the advisories, 105, were for E. coli, an indicator for fecal material that can carry parasites or other pathogens that sicken swimmers. High E. coli levels were what triggered no-swim warnings at Lake Macbride in Solon.
Iowa’s state park beaches had six advisories for microcystins, toxins produced by some blue-green algae that can cause gastroenteritis, skin irritation and allergic responses, as well as potentially life-threatening liver damage, according to the U.S. Centers for Disease Control and Prevention.
The microcystin warnings were concentrated at two state park beaches, Viking Lake Beach in Stanton with four advisories, and at Green Valley Beach in Creston, which had two advisories.
Iowa’s beach monitoring program, started in 2000, involves technicians taking weekly water samples at state park beaches. If counties or cities want to test local beaches, the DNR provides a protocol for collecting samples and pays for water testing.
A color-coded map on the DNR’s beach monitoring website shows which state and local beaches are safe for swimming each week.
At beaches that exceed Iowa’s standards for bacteria or microcystins, signs are posted warning “Swimming is not recommended.”
State officials often don’t know what causes high levels of bacteria or toxins at public beaches, said Dan Kendall, the DNR’s Ambient Lake and Beach Monitoring coordinator.
“The test we run doesn’t allow us to source track the E.coli, and the current technology to source tracking is very specific and expensive,” Kendall said. “The goal of the beach program is to collect for notification of advisories to the public during the primary recreational season and to track trends over time.”
Mary Skopec, who supervised DNR water monitoring for many years and was beach monitoring coordinator for 2014 through 2016, said Lake Macbride, an 812-acre man-made lake, has had serious problems in past years with goose droppings on the beach.
“At one point, I made a strong statement to the park manager about dealing with the amount of goose fecal matter on the beach. They made a concerted effort to clean it up, and numbers dropped below detection for E. coli,” Skopec said. “I suspect that maintaining the beach has been a challenge for DNR given cuts in staff — especially temporary staff that can clean beaches.”
Park managers can remove goose droppings mechanically or use dogs or lights to scare geese away, Skopec said.
Weather can influence the level of toxins in lakes and rivers, officials said. During heavy rain, fertilizer and manure wash into streams and can cause spikes in E. coli or microcystins, while sunny weather encourages growth of blue-green algae.
Backbone State Park in Delaware County had the highest number of advisories in the state in 2018 with 14. Lake Macbride was second, followed MacIntosh Woods beach in Ventura with 10 no-swim warnings.
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The last two weeks of July saw the highest number of beach advisories statewide with 11 each week. That means, for those weeks, the DNR warned against swimming at more than one-quarter of Iowa’s state park beaches.
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