The number of swimming advisories for algae toxins has dropped from a year ago, even though the state used a tougher standard, Iowa Department of Natural Resources records show.
But the more prevalent fecal bacteria problems at state-park beaches led to a near-doubling of advisories for E. coli. High levels of that fecal bacteria typically mean the presence of organisms that can cause infections, intestinal illnesses or worse.
From Memorial Day to Labor Day, the state recorded 12 swimming advisories for microcystin, one of the main toxins emitted by blue-green algae in Iowa lakes. That was down from 21 last year and the third-lowest number since 2011.
Backbone State Park, the state’s oldest park, celebrated its centennial this year. The swimming area at Backbone’s lake, which is an impoundment on the Maquoketa River, had the most significant toxic algae problems this year. Swimming was not recommended near Backbone’s beach for 14 of the 16 weeks the state pulled water samples at the beaches.
DNR decided to use the U.S. Environmental Protection Agency’s new recommended standard of 8 micrograms per liter this year while continuing to review methodologies. EPA had recommended 4 micrograms in 2016, but protests from Iowa and other states led to the recommended health level of 8 micrograms.
DNR had been using a standard of 20 micrograms before this year. The beaches that have had the most algae toxin issues include Green Valley, Black Hawk, Lake of Three Fires and Union Grove.
Microcystin is a big issue for drinking-water systems, which must either find other sources of water to treat, or pay for expensive activated carbon systems to remove the toxins. Des Moines Water Works, which serves 500,000 customers in Central Iowa, declared the Des Moines River “essentially unusable” because of microcystin levels this summer.
The 112 state swimming area advisories for fecal bacteria came after 60 postings in 2019. The 112 warnings were the third-highest total since 2014.
The beaches with bacteria issues included several that have perennial issues, including Backbone, Beads Lake, McIntosh Woods at Clear Lake, Lower Pine Lake near Eldora and Emerson Bay at West Okoboji Lake.
The high readings led to advisories at nine swimming areas as late as Labor Day weekend.
“The severe drought that impacted much of the state this summer makes it more challenging to draw conclusions about this year’s advisory numbers,” Alicia Vasto, who follows water quality issues for the nonprofit Iowa Environmental Council, said in a statement. “Despite that, the pattern that we see year after year remains — contaminated beaches that put swimmers’ health at risk.
“These issues aren’t going away and that’s why we need to continue to fight for clean, safe water,” Vasto added.
DNR tracks its beach monitoring online with an interactive map.