Editor’s note: This story originally published in November 2022 but the problem being described remains just as relevant now. Eight Kansas lakes were in blue-green algae watch or warning status in early July 2023.

A deadly bacteria could be awaiting Kansas livestock, pets and wildlife in the ponds where they drink. Scientists say it’s one of the deadliest organisms in the world.

“The cyanotoxins that cyanobacteria produce can be more potent to humans or animals than cobra venom,” says Steve Ensley, K-State clinical veterinary toxicologist. “We’re talking parts per billion amounts (can) easily cause death in a 1,200-pound animal.”

The culprit is cyanobacteria, more commonly known as blue-green algae. 

It’s so deadly it’s blamed for killing 330 elephants in Botswana in 2020. Several small groups of cattle have died in Kansas, and hundreds of hogs died from toxic water at a farm in Iowa.

Numerous Kansas dogs and unknown numbers of wildlife have died from ingesting the toxins while drinking or licking their feet clean. Kansans have been sickened by skin contact with cyanobacteria or even just inhaling fumes from blooms. It’s blamed for 60 human deaths at an outbreak in Brazil. 

Kansas pond owners are taking notice. The iconic sights of cattle lazily wading in pasture ponds may become less common. At times, access to many of Kansas’ thousands of ponds built for pleasure could become off limits to pets and people. Few Kansans have avoided being impacted.

Blue-green algae have collectively robbed Kansans of thousands of hours of recreation and drained millions of dollars from lake-based economies when toxic outbreaks closed reservoirs to public access. Keeping the toxin’s bad smells and tastes from drinking water has had several Kansas municipalities scrambling and spending heavily to ensure safe water for residents.

While severity and number of harmful algal blooms seem to vary annually, many state water experts feel the occurrences are trending upward in Kansas, especially on public lakes and reservoirs. 


Don’t assume all algae is toxic. Most types provide a valuable service to the chain of life in lakes and ponds.

Year after year, it seems harmful algal blooms are becoming more severe and more common.

One such authority is Tom Stiles, director of water for the Kansas Department of Health and Environment. Stiles says it’s important that everyone becomes aware of the problem. Simply learning to identify blue-green algae can help keep families, pets and other animals safe. Education could also change some behaviors that are currently encouraging algal blooms. 

Researchers are hoping that increased awareness will lead to more reports of toxic water and animal deaths. That could lead to a better understanding of cyanobacteria. 

Kansans, they say, also need to learn how to coexist with harmful waters. Though not seen as a serious problem until about 10 years ago, all indications are that we may be dealing with cyanobacteria problems indefinitely.

“You can’t let it paralyze you and keep you out of the outdoors,” says Joe Gerken, K-State extension specialist and instructor. “But we also can’t ever let it get totally out of our minds from now on. I never let my guard down, especially when I’m out with my dog and we’re near a pond.”

Meanwhile, some of the brightest minds in the world are striving to find ways to better prevent, predict and someday eradicate the most problematic blooms.

Ensley is one of many scientists from state agencies and universities studying toxic blooms. Federal heavyweights such as NASA, the National Oceanic and Atmospheric Administration and the Environmental Protection Agency are helping.  Most of those studying the problems say they’ve never dealt with anything as mysterious or as frustratingly inconsistent as cyanobacteria.

When problems first arose about a decade ago, scientists theorized the blooms were a product of climate change and increases in farm fertilizers that made their way into large Kansas reservoirs. While such theories still hold sway, other variables appear to be at work. 

“It seems like everything we thought we knew five to ten years ago (about cyanobacteria) has since proven wrong,” says Stiles. “This stuff doesn’t play fair. It keeps changing the rules.”

So far, most attempts to eradicate blooms have failed, though there are currently new areas of research underway at several private and public ponds in eastern Kansas. 

Man standing on lake dock looking at water.
Tom Stiles, director of water for the Kansas Department of Health and Environment, checks Lake Shawnee outside Topeka, where a sewage leak in early summer led to an algal bloom. It was weeks before the threat passed. Credit: Jeff Tuttle

Two billion years old, creator of oxygen

Ted Harris of the Kansas Biological Survey studies cyanobacteria within 100 small ponds at the KU field research station north of Lawrence. Though the bacteria can be as small as 1/25,000 of an inch, they’re easy to find.

Harris says they’re in about every ocean, river, impoundment and puddle around the world. Cyanobacteria are about 2 billion years old and have performed some important services to mankind.

“It was the first organism to master photosynthesis, which creates oxygen. We might not be here without it,” says Harris, an assistant research professor. 

For centuries, scientists think, cyanobacteria produced few problems even as huge blooms died and then released toxins.

Harris referenced a bad algal bloom at Kanopolis Reservoir in 1950. A Cheney Reservoir bloom that added a bad taste and smell to Wichita’s drinking water was one of several minor blooms amid the 1990s and early 2000s.

Then came nightmarish toxic blooms.

“In 2011 (algal blooms) came on and rolled over us like a massive, full-fledged invasion,” says Stiles. “It seems like it’s just kept rolling ever since.”

Milford and Marion were the reservoirs initially hit hardest, with blooms bad enough to sometimes close much of the lakes to human contact. They are still two of Kansas’ most susceptible waters to toxic blooms.

As Stiles notes, cyanobacteria seemingly have been spreading across Kansas ever since. Some weeks it’s been common to see 20 to 30 public waters listed on the KDHE’s harmful algal blooms advisory list. First-time waters are added annually. Once a lake has its first harmful bloom, odds increase for repeat blooms.

Stiles says science has no solid answers for why cyanobacteria problems came out of nowhere in 2011 and continue to spread across the state. Nor do they know why some large blooms release toxins and others don’t. It also remains a mystery why sizable toxic blooms can occur within a few hours from seemingly clear water, then totally disappear in the same amount of time.

Kansas scientists aren’t alone in such frustration.

“This stuff will keep you humble,” says Jennifer Graham, a New York based U.S. Geological Survey research scientist with 23 years of experience with cyanobacteria. “It seems good at reminding us how much we don’t know.”

  • Woman collects water sample from lake shore.
  • Closeup of water sample
  • Woman walking on lake shore beside warning sign.

Climate change more than rising temps

With the first problematic algal blooms came theories that the planet’s gradually warming climate was to blame, especially given mid-summer trends of consecutive hot days.

“We used to say the Fourth of July to Labor Day was our blue-green algae season. That’s when we have the warmest water,” says Stiles. “But that’s not true anymore. We now have blooms in early spring all the way into November. A bad bloom during duck seasons (which peak in November) could get a lot of hunting dogs killed.”

Harris says heat can accelerate algal bloom. But he believes climate change’s largest contribution to the problem has been changes in Kansas wind patterns.

“We’re getting longer stretches of days with heavy winds and longer stretches of no wind,” says Harris. “Those calm stretches can really kick in the cyanobacteria blooms. It’s the wind that saves us by not letting those algal blooms float to the surface and form huge, possibly hazardous blooms.” 


Blue-green algae will normally be on the surface, often in swirls. Many accurately say it resembles “spilled green paint.” 

Wind also stirs up assorted sediments in the water, creating turbidity. Such murkiness prevents bloom-triggering sunlight from reaching the scattered cyanobacteria.

Consider Tuttle Creek Reservoir, 20 miles east of Milford Reservoir. Different soils and a more rugged topography combine to make Tuttle Creek’s water more turbid. Harris believes that’s why Tuttle Creek seldom has algal bloom problems. Meanwhile, Milford, where the water is usually clear, has them frequently.

Feed them and they will grow

Like all organisms, cyanobacteria respond to nutrients. Decades of fertilizer washing in from farm fields means Kansas lakes and ponds can be like a never-ending buffet for algal blooms.

Nathan Nelson, Kansas State University soil fertility and nutrient management professor, says some current farming trends have cyanobacteria better fed than ever.

“We’ve had a big movement towards reduced tillage or no-till farming,” says Nelson. “Not working the soil is great for reducing sediment loss, but an unintended consequence can be more fertilizer getting washed away.”

He’s referring in particular to phosphorus, a productive and popular fertilizer. The advent of growing more corn across Kansas, a crop that responds well to phosphorus applications, means farmers are using more of it as fertilizer.

Nelson says farmers broadcasting phosphorus atop the soil is a common practice. Broadcasting onto non-tilled ground increases the chances that phosphorus gets washed away, ending up in streams and eventually bodies of water.

Machinery that injects the phosphorus into the ground can reduce runoff, but it can be expensive to purchase and operate, Nelson says. Farmers generally don’t notice enough loss financially from broadcasting to explore other options. 

Nutrients such as phosphorus can stay viable in a lake’s sediment for years, according to Harris, and keep feeding algal blooms. 

Stiles says researchers are working with some farmers to reduce crop field runoff, largely by putting strips of lush, native grasses along streamways to absorb the nutrients. Currently only a small fraction of agricultural fields are farmed with that level of conservation in mind. Filter strips, sometimes called buffer strips, can be enrolled in U.S. Department of Agriculture conservation programs, which would pay farmers to keep the land out of production. But financially, that’s not a tradeoff many farmers are interested in making.

Agricultural nutrients can come in other forms too. 

“Any time cattle start going into the water, their waste is adding nutrients to the water,” says Gerken. “Blue-green algae doesn’t care if its nutrients come from fertilizer runoff or the back of a cow. It’s going to use it to grow, either way.” 

Some pond owners report algal problems increase after winters when huge flocks of geese have stayed on their ponds too.

Runoff from heavily used pastures and feedlots can provide manure nutrients to waterways as well.

Towns and cities can contribute to the problem too. Runoff from golf courses and housing developments can wash a variety of fertilizers into streams and impoundments. 

“You can’t have green lawns without having green water,” says Mark Jakubauskas, a past Kansas Biological Survey researcher, as he diagnosed popular lawn fertilizers in silt sediment cores from several Kansas lakes. “I can just about tell you when a subdivision or golf course went in by looking at the nutrients that show up down in the siltation.”

Concerned Kansans can help the cause by limiting the use of fertilizers on lawns or gardens, or working them deep into the soil. Simply picking up all pet waste could save tons of nutrients from reaching nearby streams and rivers in the state’s largest towns.

Harris says those nutrients can stay viable within a reservoir for many years after they arrive.

“I tell people I’m surprised we didn’t start getting (problematic) blooms earlier and don’t know why we don’t have a lot more of them,” says Harris. “There’s always been an abundance of nutrients.”

Cattle ponds, cyanobacteria’s new frontier

Most Kansas ranching families went generations without worrying about their cattle getting poisoned by algae in their ponds. Even when blue-green algae hit the news a decade ago, reports of it focused on large reservoirs that drained croplands.

Those days are gone, says A.J. Tarpoff, a K-State professor and extension specialist. Toxic blooms are now found in many Kansas ponds, some amid prairie with no crops or accompanying fertilizers for miles. 

Cattle have died from drinking toxic water from those placid water holes. Last year Tarpoff got a call from a veterinarian who had just driven up on several mature, dead cows that had succumbed  beside a remote pond.

“There are quite a few stories like that out there,” says Tarpoff. “You hear rumors of entire herds dying. It could so easily happen, but we have no proof it already has. It sure seems like the problem is getting worse.”

Gerken’s main job with the extension service is working with private impoundment owners. He says there’s no shortage of algal blooms in those waters. During warm months he usually checks three or four impoundments per week. He estimates about one-third of those ponds check positive for harmful algal blooms. 


Usually, blue-green algae will coat a stick, like paint.

Reports, both apocryphal and confirmed, seem to be increasing every year. Actual instances could be higher because of the here-one-hour, gone-the-next nature of algal blooms.

“When someone sends in a sample, we’re basically just testing a snapshot in time,” says Scott Fritz, a K-State diagnostic toxicologist, who added that things like wind conditions can change things quickly.

Fritz also says that early in a bloom event there may not be enough toxins to measure, but that toxins can quickly increase to problematic levels. 

Ensley says the exact number of Kansas livestock killed by digesting cyanobacteria is nearly impossible to determine. Kansas has no requirements for reporting suspect livestock deaths, or to send in water or tissue for testing. 

Gathering needed tissue samples isn’t easy. Within a half-day of heat, decomposition can ruin any chance for accurate testing. Finding a large-animal veterinarian to take timely samples can be difficult. Many cattle owners also don’t want to pay hundreds of dollars for testing on a dead animal. 

Looking for non-toxic water

Tarpoff and Gerken encourage cattle producers to be more proactive than reactive. With the right equipment, clean and healthy water can be pumped from ponds with histories of algal blooms.

Gerken says the deepest parts of most ponds can’t support harmful algal blooms because of lack of sunlight down deep. That means deep-set intake pipes can send healthy water to stock tanks below the pond’s dam, which should be the herd’s only access to water. 

While the costs of fencing completely around a pond and adding a pumping system can cost thousands of dollars, Gerken and Tarpoff say the benefits of such preparation can pay for itself if it prevents the loss of even one cow. Tarpoff says cattle prefer drinking from a solid tank rather than a pond. Gerken also referenced research that showed switching cattle from dingy to clear water can increase their growth by up to 19%.

  • Heron standing on lake dock.
  • Algae-cover rock in Kansas lake.
  • Boat containing fisherman on Kansas lake.

Josh Hoy, a Chase County rancher, had cattle seriously sickened several years ago by consuming tainted pond water. That year he had his worst-ever reproduction rates, too, probably from the toxins. He’s currently removing ponds from his ranchland and is using natural grazing and burning programs to improve the quality of natural surface springs.

“Impoundments aren’t natural to this part of the country,” says Hoy. “We know the spring water doesn’t have any (toxic algae) and is a lot better for cattle than pond water. A lot of these ponds never should have been built, and the springs should have been better cared for.”

Research challenges

KDHE and extension service personnel are experimenting with multiple methods to provide animals clean drinking water from ponds. One utilizes bales of barley straw placed in the water, on the theory that a compound released as the straw decomposes will neutralize algal toxins. The other filters bad water through several feet of sand, a method that’s been used in remote regions for decades to give people clean water.

Official findings aren’t out, but there are concerns.

“Treating toxic algae is kind of like treating COVID; sometimes something will work and the next time it won’t. It’s like it gets an attitude, and it doesn’t care what you do,” says Stiles. “The toxins may go through that sand filter even if you stop the algae. Other times they might not.” He also says some ponds with barley straw bales have had multiple blooms while others have not.

Eradicating active blooms on larger Kansas waters hasn’t gone well, either.

Stiles says in 2019, the Kansas Legislature granted KDHE $450,000 annually, over a four-year period, to research ways to deal with algal blooms. Results haven’t been as good as hoped. 

In 2020, a sizable bloom on Milford was treated with peroxide. The treatment worked, but not long enough.

“It knocked (the cyanobacteria) back for about three hours, then it was back. That treatment was $128,000,” says Stiles. “That’s about $43,000 an hour for short-term relief.” 


For the average person, the “jar test” is the most accurate way to identify potentially dangerous waters. It’s as simple as dipping a clean, clear jar into the water on the downwind side of the enclosed body of water. The jar is sealed tightly with a lid and placed in a refrigerator overnight. Buoyant, blue-green algae will usually float to the top and form a visible ring around the top of the jar.

Stiles says dealing with sizable blooms on large waters may not be practical. He added the agency may try to treat localized blooms, such as those on swimming beaches.

KDHE also has been trying to stop toxic blooms on smaller waters before they begin, or at least lessen their severity.

Elizabeth Smith, a KDHE biologist, is overseeing research at ponds below the dams at Milford and Melvern reservoirs. Both ponds have histories of significant blue-green algae blooms. Smith explained the study includes seeing if pre-season peroxide treatments can mitigate blooms by reducing the number of resting cells on the lakebed before they can become problematic.

Both ponds eventually had blooms.

“It’s kind of disappointing,” says Smith. “But we’re still waiting to see how bad it gets. We’re hoping it will greatly lessen the blooms.”

After thousands of collective hours studying 100 ponds, Harris and others are working to replicate about every scenario imaginable for understanding and predicting cyanobacteria.

“We’re working at getting to know every piece of this puzzle,” Harris says. “We need to find some patterns, so someday we’ll be able to say, with confidence, ‘Next week you’ll probably have an algal bloom,’ and they’ll be able to do something about it. That could make a huge difference for people.”

Keith Loftin, a U.S. Geological Survey supervisor and research chemist, works in Lawrence but can view algal blooms from 500 miles up via satellite. Loftin is the leading USGS representative on a project with the EPA, NASA and NOAA. The satellite monitors 2,000 bodies of water in the continental United States. Loftin and others often see algal blooms sooner than people on a lake’s shore.

Field crews can be sent to get samples of particularly bad blooms for further research.

Loftin can send field crews to get samples of particularly bad blooms to further his research.

“We don’t have it all figured out. The satellite can see cyanobacteria blooms, but it can’t see the toxins,” says Loftin, who has studied cyanobacteria for 18 years. “That’s hard enough in labs, so we’re hard-pressed to do it from space, at least not without some techno-improvements. There’s still a lot of tire kicking going on.” 

Loftin has hopes that more knowledge will become available as cyanobacteria gather more attention and are increasingly researched around the globe. Lots of information is being shared. Earlier this year more than 150 scientists from as far as Singapore and Scandinavia gathered in Toledo, Ohio, for the International Conference on Toxic Cyanobacteria.

Human adaptation required

Loftin also said changes that lessen the impact of harmful algal blooms may depend more on modifying human behavior than trying to change an organism that’s been around for 2 billion years. 

“We’ve never been very successful at changing nature, but we can change our actions,” he says. “I tell people we didn’t create cyanobacteria, but we sure may be involved in why it’s getting worse. We’ll have to look at our behaviors and see if there are choices we can make, then see if we can get a consensus to make them.”

Heron landing on water.
Credit: Jeff Tuttle

Many Kansans have already adapted.

Brad Roether has owned lake-based businesses around Milford Reservoir for decades. He’s seen the worst of times when horrendous algal blooms left the lake, and many local businesses, mostly abandoned. For several years, even when blooms were gone, people were still afraid to go in or on the water.

Yet even with 2021’s large, problematic blooms, Roether reported Milford had some of the biggest crowds in the lake’s history. The crowds were a carry-over from 2020, when COVID shut down many workplaces and sent people outdoors for healthy social distancing. Camping, boating and fishing grew in popularity then and have largely continued.

“People have learned to adapt,” says Roether.  “It used to be, everybody panicked. Now they’ve learned to go where the water isn’t green, to the upwind side of the lake where there isn’t algae. Common sense is taking over.”

It’s helped, he says, that KDHE divided Milford into three zones that are rated independently. One may be off-limits while the others are safe enough for at least some activities.

Businesses have made the lake area more accommodating. Acorn Resort added a swimming pool, which at first seems incongruous since it’s on the shores of the state’s largest lake. Milford State Park added a splash pad for kids and has improved already impressive hiking and cycling trails.

Roether likes the crowds but wishes the algal problems were gone.

“You know, the people are back, but that stuff is still out there and it’s still disgusting,” he says. “Honestly, I care more about the good of the lake than my businesses. They’ve got to figure something out.”


Keep in mind that none of the methods mentioned in this article
are 100% accurate, and that algal blooms can come and go in a short
period of time.

The best way to have a private pond tested is to contact the local county extension agent. A list can be found at ksre.k-state.edu/about/statewide-locations.html,or by calling 785-532-5820.

The Kansas Department of Health and Environment has a website dedicated to educating people about harmful algal blooms (HABs) in Kansas. The page includes a history of blooms in the state, possible dangers of coming in contact with toxic water and how to report suspected blooms.

An important part of the webpage is the listing of public waters where harmful algal blooms are possible or present. The list is updated weekly from April 1 to Oct. 31. Harmful blooms have been found before and after those dates. 

While some waters are regularly tested, most waters are only tested if a report has been filed by a natural resource professional or a member of the public. KDHE will often send staff members to take water samples.

KDHE uses the following system to rate the severity of algal blooms on public waters. Note that algal blooms can come and go within a few hours. Also, while one part of an enclosed body of water may be experiencing a toxic bloom, other areas on the water may be clear of the harmful algae.

Fall Journal cover

A version of this article appears in the Fall 2022 issue of The Journal, a publication of the Kansas Leadership Center. To learn more about KLC, visit http://kansasleadershipcenter.org. Order your copy of the magazine at the KLC Store or subscribe to the print edition.

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