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Algae blooms are getting more toxic and spreading north on the Great Plains

A photo shows a scientist from the Kansas Biological Survey holding a sample of blue-green algae.
Javier Morales
/
Kansas Biological Survey
A Kansas Biological Survey scientist holds up a water sample from a blue-green algae bloom at Marion Reservoir in 2021.

States like North Dakota, South Dakota, Wyoming and Montana will have to deal with toxic blue-green algae blooms already common in Kansas. Utility companies will have to act fast to treat drinking water and keep it safe.

The ugly blue-green algae that frequently spoil Kansas lakes for swimming, fishing and supplying drinking water are growing more toxic as the climate changes.

And they’re spreading farther north.

States in the upper Great Plains will have to get used to spending on expensive water treatment — the way utilities in Kansas do — to keep taps flowing.

They’ll need programs to quickly warn people away from popular recreation spots when blooms appear that can turn toxic fast, make them sick and kill their dogs.

“States like North Dakota, South Dakota, Wyoming, Montana … you’re going to get a lot more blooms and have to deal with this,” said Ted Harris, an algae biologist with the University of Kansas.

The growing toxic algae problem doesn’t just add another reason people in the Midwest and Great Plains need to fight climate change — it adds urgency to the task of figuring out how to cut back on the vast amounts of fertilizer and livestock excrement that wash into waterways and intensify the algae toxins.

A team of scientists, including Harris, did a deep-dive into algae conditions on nearly 3,000 U.S. lakes and published their findings this month.

Toxic blue-green algae blooms will happen more frequently in lakes farther and farther north as water gets warmer, they concluded. All the extra nitrogen spilling into U.S. waterways will “supercharge” the problem.

This map from the study published in Nature Water shows how much likelier toxic blooms will become by the end of this century compared to half a century ago. Red areas will see odds go up more than 50% of summertime algae so toxic that the water would be unsafe for kids to drink unless it’s treated first. Yellow and orange areas will see increases, too, but not as high. Areas in shades of blue will see odds go down.
This map from the study published in Nature Water shows how much likelier toxic blooms will become by the end of this century compared to half a century ago. Red areas will see odds go up more than 50% of summertime algae so toxic that the water would be unsafe for kids to drink unless it’s treated first. Yellow and orange areas will see increases, too, but not as high. Areas in shades of blue will see odds go down.

Their work may help broaden the long-standing focus on phosphorus pollution in the battle against worsening blooms. Phosphorus pollution does fuel big blooms, but nitrogen makes them more toxic, so the agriculture industry needs to tackle both.

Toxic blooms are already common in Kansas, and the study suggests they will get worse in parts of the state in the coming decades.

Cattle have died in Kansas from algae toxins in ponds. And in 2011, people got sick and dogs died after contact with toxic algae at Milford Reservoir near Junction City.

Wind blows the algae toward lakeshores, concentrating toxins and making them more dangerous.

“And then where does your dog go and get in? And where do you get into the lake? These launching ramps and coves where all this stuff has blown in,” said Harris, a research professor at the Kansas Biological Survey and Center for Ecological Research at KU.

Toxic blooms also sometimes catch water utilities off-guard, so by the time they begin treating water to remove the toxin, unhealthy levels have already reached customers.

In 2014, for example, nearly half a million Ohio residents near Lake Erie were told not to drink water from their taps because it contained too much toxin from blue-green algae.

A photo shows Ted Harris gathering blue-green algae at Marion Reservoir in 2021.
Javier Morales
/
Kansas Biological Survey
Biologist Ted Harris gathers blue-green algae at Marion Reservoir in 2021.

By the end of this century, lakes in the northern and western U.S. will be much likelier to experience blooms so toxic that the Environmental Protection Agency considers the water unsafe for children to drink. So utilities, and ultimately their customers, will have to pay for the costly treatment more often.

A few watersheds in the Upper Midwest and New England, and many more in the country’s northwest, will see those odds increase by more than 50% compared to the situation half a century ago.

But lakes, it turns out, can also become so warm that blue-green algae produce less toxin, the study found.

In southern states, the climate will get so much warmer by the end of this century that even if the algae become more abundant, they’ll likely be less toxic than half a century ago.

Kansas, meanwhile, is split. Algae blooms will likely become more toxic in some areas and less toxic in others.

Parts of the state might see less toxicity at the height of summer, when lakes will simply be too warm by the end of the century, but could get more toxic blooms in the spring and fall.

Lots of different kinds of algae live in lakes. But global warming makes it easier for blue-green algae to outcompete other species.

Blue-green algae aren’t always toxic, and when they are, the toxin levels vary.

However, these algae are more likely to become so toxic they’ll cause problems for drinking supplies when water temperatures reach 68 to 77 degrees and the water contains plenty of nitrogen, the study found.

A photo shows Blue-green algae blooming next to a playground at Milford Reservoir in 2017.
Ted Harris
/
Kansas Biological Survey
Blue-green algae bloom next to a playground at Milford Reservoir in 2017.

Many lakes today have lots of excess nitrogen from crop fertilizers washing off of farm fields, dung and urine produced by livestock operations, and treated sewage.

State health officials regularly release advisories about toxic blooms. People can report blooms they spot to the Kansas Department of Health and Environment.

In lower doses over long periods of time, scientists say blue-green algae toxins may cause cancer.

The study — published in the scientific journal Nature Water by scientists at KU, the Carnegie Institution for Science, the University of Greenwich and the Chinese Academy of Sciences — used measurements taken at more than 2,800 lakes in the U.S. between 2007 and 2017.

The authors are now pulling together water quality information from other countries to see how toxic blooms might change elsewhere around the world.

Celia Llopis-Jepsen is the environment reporter for the Kansas News Service. You can follow her on Twitter @celia_LJ or email her at celia (at) kcur (dot) org.

The Kansas News Service is a collaboration of KCUR, Kansas Public Radio, KMUW and High Plains Public Radio focused on health, the social determinants of health and their connection to public policy.

Kansas News Service stories and photos may be republished by news media at no cost with proper attribution and a link to ksnewsservice.org.

This story is being distributed through Harvest Public Media, a collaboration of public media newsrooms in the Midwest. It reports on food systems, agriculture and rural issues.

I write about how the world is transforming around us, from topsoil loss and invasive species to climate change. My goal is to explain why these stories matter to Kansas, and to report on the farmers, ranchers, scientists and other engaged people working to make Kansas more resilient. Email me at celia@kcur.org.
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