Harmful algae at Lake Macbride causes first-ever swim warning for toxins

'Pea soup as far as the eye can see'

The green color of Lake Macbride near Solon, pictured June 22, 2019, was caused by a harmful algal bloom, officials conf
The green color of Lake Macbride near Solon, pictured June 22, 2019, was caused by a harmful algal bloom, officials confirmed. Microcystins, a toxin produced when the algae die, were so high June 18 that the state issued its first-ever microcystin swim warning for the Lake Macbride beach. (Photo supplied by Chris Jones)

SOLON — Harmful algae that bloomed at Lake Macbride earlier this month, turning the water to a murky green, caused the first-ever swim advisory for microcystins at the popular beach.

The spike in toxins that can sicken humans and animals occurred despite millions of dollars spent by the state in recent decades to improve water quality at the lake.

“We’re not very good at guarding our investments,” said Chris Jones, a University of Iowa research scientist who blogged about the lake last week after a camping trip, saying it looked like “pea soup as far as the eye can see.”

Water tests June 18 at the Lake Macbride beach showed microcystin levels were 22.26 micrograms per liter of water, above the 20 micrograms-per-liter standard the Iowa Department of Natural Resources uses for recreational waters. The Iowa DNR posted a swim advisory June 21.

“This is the first time we have detected a microcystin value above the 20 ug/l threshold in a sample collected at Lake Macbride Beach,” said Daniel Kendall, Iowa DNR coordinator of beach and lake monitoring programs.

Tests last Tuesday showed microcystin levels back down at 1.7 micrograms per liter. However, E. coli bacteria were over the state recreational standard, so the swim advisory remained.

Lake Macbride is one of 39 state park beaches that get weekly water monitoring for E. coli bacteria and microcystins. E. coli is an indicator of fecal material, which can carry parasites or other pathogens that can sicken swimmers. Microcystins, generated when blue-green algae die, can cause gastroenteritis, skin irritation, liver damage and nerve damage.


Lake Macbride, a 940-acre lake with a maximum depth of 45 feet, developed a harmful algal bloom in mid-June, Park Manager Ron Puettmann said.

A sign by the Lake Macbride beach warned against swimming and the Iowa DNR Beach Monitoring website showed the microcystin levels were above the state recreational standard. But not everyone sees the warnings before they wade in, he said.

Lake Macbride State Park had 531,000 visitors last year, the sixth highest annual attendance of Iowa state parks.

“It’s really up to folks to monitor the beach monitoring website or listen to the news to find out if there are advisories,” Puettmann said. “We do have people who stand there reading the sign. If we are in the beach area patrolling, they can ask questions.”

Joy Mann, 40, of Cedar Rapids, brought her daughter, Tessa, 12, and McKenna Taylor, 11, on Thursday to the Macbride beach. They had not spotted the swim advisory posted on a sign at the beach entrance.

“Does that mean we have to leave?” Tessa asked, pulling her goggles up onto her forehead.

“You’ve already been in there, so what’s the point?” Mann said.

The primary concern with microcystin pollution is very young children who play in the shallows and may put their hands in their mouths.

Mann said she avoided Lake Macbride in the past when she heard about swim warnings, but she also wonders if Iowa lakes are any more polluted today than they were when she was Tessa’s age.


“I grew up going to the lake,” she said. “I don’t know if they even tested 30 years ago.”

Iowa had no confirmed cases of microcystin poisoning in 2018, but people have gotten sick in other states in recent years. A 2015 article in the journal “Toxins” said there were 34 reports of human and animal illnesses from harmful algal blooms in Kansas in 2011, with the cases including five dog deaths and hospitalization of two humans.

Farm fertilizer washing into streams and lakes often sparks harmful algal blooms. Iowa’s rainy spring and early summer have made the problem at Lake Macbride worse than past years, Puettmann said.

“Without the sunshine to kill off some of the microcystins, it adds to the mix,” he said.

From 2000 to 2002, the Iowa DNR spent $2.5 million to fortify shorelines at Lake Macbride to reduce sediment drifting into the water. The agency put in a silt dam on the north side of the lake, installed fish and aquatic habitat structures and built a dozen rock jetties, Puettmann said.

“The overall goal was to try to improve the water quality,” he said. Specifically, the Iowa DNR wanted to improve the water clarity and that seems to be better, Puettmann said.

But Lake Macbride has continued to have water quality issues. The lake had swim advisories for E. coli 12 of the 15 weeks of summer in 2018. Department officials think this is linked to the feces of Canada geese that congregate on the beach, but they can’t be sure because the Iowa DNR does not monitor water farther out in the lake, Puettmann said.

“I would love to see a volunteer effort to reach out into more parts of the lake, especially with all the user groups that like to come and do open water swimming, paddle sports, kayaking,” he said. “But there’s no way within our resources to make it happen.”

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