August 14, 2015

The Science Of Iowa Lake Scum

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A photo of an algae bloom this summer on Green Valley Lake in Union County.

Connor Nicholas/Iowa Department of Natural Resources

A photo of an algae bloom this summer on Green Valley Lake in Union County.

The Iowa Department of Natural Resources issued two beach advisory warnings during the previous week, the DNR reported on Friday, Aug. 14, warning people to stay out of the water at two state park beaches because of high levels of microcystin. Microcystin is a toxin produced by blue-green algae blooms and can make people sick. The new advisories brought the number of microcystin warnings posted this year to 25, breaking the previous record of 24 warnings in 2013.


Only certain strains of cyanobacteria, commonly called blue-green algae, can produce toxins, although they don’t always do so.

“Scientists generally agree that the cyanobacteria evolved this ability to produce toxin either as a competitive advantage or as some sort of protection,” Mary Skopec, who heads the Iowa Department of Natural Resources beach monitoring program, said.

Mary Skopec, of the Iowa DNR's beach monitoring program, looks at a water sample from Black Hawk Lake in her lab July 30, 2015. The sample tested high, with microcystin concentrations above the advisory level of 20 micrograms per liter.

Lauren Mills/IowaWatch

Mary Skopec, of the Iowa DNR’s beach monitoring program, looks at a water sample from Black Hawk Lake in her lab July 30, 2015. The sample tested high, with microcystin concentrations above the advisory level of 20 micrograms per liter.

“But what spurs them to do that some times and not other times is not well know.”

This means Iowa’s beach monitoring and advisory system is largely “in response mode.”

“We wait until we see a bloom, we test the bloom and then tell people. So we really want to push that envelope forward in terms of prediction. And having good confidence in that prediction,” Skopec said.

Some scientific advances, such as the use of satellite imagery by federal agencies, could help. Skopec said being able to use the data coming out of those agencies and using a model to predict bloom intensity and toxicity could help the program predict and warn people about toxin levels in real time.

Science is advancing in other ways, too, she said, which could lead to new advisory levels for microcystins and some of the other toxins produced by the cyanobacteria that are not tracked at this time.

Currently, microcystins are the only cyanotoxin used in issuing advisories and the only one the beach monitoring program tests. However, other toxins are produced by the cyanobacteria, including cylindrospermopsin, anatoxin and saxiotoxins.

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