Two-thirds of state beaches had swim advisories this year, group says

By: - September 29, 2022 3:37 pm

Emerson Bay beach, to the north of this area of West Okoboji Lake, has had 47 swim warnings since 2014. (Photo by Perry Beeman/Iowa Capital Dispatch)

There were 25 state beaches this summer where swimming was not advised at least one week because of elevated levels of bacteria or toxins or both, according to the Iowa Environmental Council.

The Iowa Department of Natural Resources samples water at the beaches weekly from late May until early September, when people are most likely to come in contact with the water. The department tests for concentrations of E. coli bacteria and blue-green algae toxins, which can cause skin irritations, illnesses and infections.

The 25 beaches with swim warnings this year represent about two-thirds of the total beaches at state parks and was a comparable number to last summer, when 24 beaches had the advisories.

The IEC has been monitoring the state testing program for nearly 20 years but has not been able to identify a definitive trend in the bacteria and toxin levels, said Alicia Vasto, the group’s water program director.

“Overall, what we understand is that we consistently have beach advisories in the state,” she said. “We consistently see contamination from E. coli.”

The toxins are produced by cyanobacteria that can proliferate — or “bloom” — when lake water is hot and calm and rich in nutrients, often from farm fertilizer runoff. The blooms turn blue as food wanes and the bacteria perish.

This summer, there were 12 weekly advisories for the toxins, according to the IEC data. That was about half of last year’s number.

But this summer there were 107 advisories for elevated E. coli concentrations, a 22% increase from last year.

Spikes in the bacteria’s presence often follows rainfall that washes it into the lakes, perhaps from the feces of geese and livestock, for example. E. coli bacteria also feed on the remains of cyanobacteria blooms.

The water of Lake Darling in southeast Iowa most consistently had elevated levels of bacteria this year, the IEC reported. There was only one week when Darling didn’t have a swim advisory in effect. The lake had a total of 14 E. coli advisories and two for toxins.

Bacteria levels can change considerably over the span of days. An example: The concentrations of E. coli at Crandall’s Beach at Spirit Lake was so high in August it was immeasurable by the DNR’s tests, which can detect up to 24,000 viable bacteria per 100 milliliters of water — or less than a half cup of water.

That concentration is more than 100 times the amount that can trigger swim warnings. But the week after that test, the beach water’s test showed just 52 bacteria per 100 milliliters, which was less than the safety threshold of 235.

The DNR has worked to limit watershed pollution — including bacteria, nutrients from farm fertilizers and manure, and eroded soil — from reaching the state’s lakes, but Vasto said more needs to be done.

“It’s really concerning because we have so few public places in our state — we have so few public lands,” she said. “And so the public beaches and parks that we have, we really need to protect them and do more to address this issue.”

In a December overview of major lake restoration projects, the DNR reported it had completed 29 projects, 21 were in progress and 14 were being planned.

Sometimes the projects do not fix the water-quality issues, though. A $12 million restoration of Lake Darling was completed in 2014, yet it frequently has elevated levels of bacteria.

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Jared Strong
Jared Strong

Senior reporter Jared Strong has written about Iowans and the important issues that affect them for more than 15 years, previously for the Carroll Times Herald and the Des Moines Register.