Iowa DNR issues advisory for Lake Darling

BRIGHTON — Lake Darling State Park is one of seven beaches where the Iowa Department of Natural Resources has issued an advisory against swimming, and one of two where the recommendation is based on algal toxin levels, rather than E. coli.

The microcystin value for the lake was 10.407 ug/L, according to a data entry table last updated June 28, available on the DNR website. The level was 21.76 the week before that. As of 2020, the action threshold is 8, according to the Iowa Environmental Council.

The data does not show harmful levels of E. coli bacteria, a more commonly occurring hazard in the lake, based on state data.

Microcystin is a toxin commonly produced by blue-green algae blooms, which themselves are commonly caused by excess nutrients from agricultural runoff according to the Department of Health and Human Services, although state beach monitoring offers no confirmation of the current hazard’s cause.

While not all algal blooms produce toxins, DNR documents show that the current one in Lake Darling does. The Iowa Department of Health and Human Services says those levels present a hazard.

“People who accidentally swallow water or breathe in water droplets containing microcystin can develop gastrointestinal symptoms, such as nausea, vomiting, and diarrhea,” the department said on an informational page about algae blooms. “Other symptoms can include cough, runny eyes and nose, sore throat, and asthma-like symptoms. Skin rashes can also develop. In severe cases, liver failure can occur.“

The problem is especially bad at Lake Darling, according to DNR data. The state agency has issued a “swimming not recommended” advisory for the park at least once every summer since 2020.

“With 14 advisories for E. coli and 2 for microcystin, Lake Darling was under a swim advisory for all but the week of June 17, the fourth week of the recreation season,” the Iowa Environmental Council said in a statement about the water body’s testing results from 2022.

The recommendation is the highest level of Iowa DNR response to water hazards according to Iowa Environmental Council Water Program Director Ingrid Gronstal, who said the state did not close beaches for public health concerns

“In all of our conversations with DNR in the last several years, they’re fairly adamant that they don’t close beaches,” Gronstal said in an interview with the Union last year. “So if there’s an advisory, that means it’s a pretty serious situation … there’s not a more serious scenario.”

Comments: Kalen.McCain@southeastiowaunion.com