In summer, toxic blue-green algae blooms plague freshwater

Tainter Lake in Dunn County, Wis., is notorious for its algae blooms. Officials just passed an ordinance requiring waterfront property to maintain a 35-foot-deep buffer strip along the water’s edge to slow runoff, which feeds the algae.Jessica Marshall / Food & Environment Reporting Network

One summer day two years ago, Danny and Laura Jenkins’ black Labrador retriever, Casey, returned from a swim in Ohio’s Grand Lake St. Marys carpeted in thick green slime and reeking. Danny Jenkins washed the dog off and, at some point, got some of the gunk in his left eye.

A few weeks later, Danny Jenkins found himself in the hospital, unable to feel his left side and with ulcers in his eye, slurred speech, stomach problems and more, according to his wife. At home, Casey began staggering and walking sideways. The dog’s eyes turned yellow. On the day Danny Jenkins came home from the hospital, still ill, Casey died.

The scum that had coated Casey during his swim turned out to be blue-green algae, or cyanobacteria. Later tests of the lake detected liver toxins and neurotoxins produced by various cyanobacteria. Casey was buried before any diagnostic tests could be done, but the doctor who treated Danny Jenkins thought his symptoms came from the algal toxins he was exposed to while washing his dog.

“The conclusion was he had encephalitis from algae bloom toxin,” said Dr. Wilfred Ellis of Lima, Ohio.

Two years later, after months of physical therapy and disability, Danny Jenkins is back working full time, but he’s still paying his medical bills, tires easily and often forgets things. “He’s not himself,” Laura Jenkins said.

Every summer as temperatures rise, blooms of cyanobacteria like the one in Grand Lake St. Marys develop in lakes and rivers across the country, turning waters intense green and coating swaths of their surfaces with putrid-smelling blue-green algae that look like pea soup. The blooms occur in nearly every state, peaking in August and September. And although no national agency tracks the blooms, experts say they are getting worse, driven by fertilizer and manure runoff into lakes and streams combined with a warming climate.

“Nationally, the problem is definitely growing,” said Jeffrey Reutter, director of the Stone Laboratory at The Ohio State University. Reutter has seen the blooms increase on Lake Erie since the mid-1990s, reversing decades of improving water quality. Last summer’s record-shattering blooms covered 3,000 square miles of the lake – almost a third of its surface – and severely cut into its more than $1 billion fishing industry.

Blooms have closed lake beaches or led to swimming advisories from Vermont’s Lake Champlain to Dorena Reservoir in Oregon and from Florida’s Caloosahatchee River to Wisconsin’s Lake Menomin. In addition to the health risks, the blooms take an economic toll. An estimate by Walter Dodds of Kansas State University conservatively puts the annual cost of freshwater algal blooms at more than $1 billion from lost recreation and depressed property values.

Cyanobacteria occur naturally in lakes, typically at low concentrations that are not harmful and not visible. But when levels of key nutrients – particularly phosphorus – in a water body soar and combine with high temperatures and stagnant water, the organisms thrive. Under these conditions, they outpace growth of other types of algae and streak or coat the water with bright, sometimes iridescent, blooms of green or blue-green cells.

Looking for the source of the problem, experts point to agriculture: Phosphorus-laden fertilizer and manure can wash directly into waterways, and eroding sediment from farmlands carries the substance, too. In addition, flows from sewage treatment plants and urban storm drains, runoff from lakeside lawns, and discharges from industries such as pulp and paper mills also can contribute phosphorus to streams and lakes.

But why are the blooms getting worse? Reutter points primarily to changes in agricultural practices. Many farmers now apply fertilizer and manure to their fields when the ground is frozen in winter, he said, because it’s easier to drive equipment over the hard surface. As a result, the fertilizer stays on top of the soil, where spring rains readily wash it into nearby waterways. In addition, researchers recently have found that drainage tile systems beneath fields – an increasingly popular method for improving crop growth that keeps fields from becoming soggy after rains – may contribute as much as half the dissolved phosphorus that comes off a given field.

Climate change is also part of the picture, said Richard Stumpf of the National Oceanic and Atmospheric Administration in Silver Spring, Md. “The longer the warm period you have in the summer, the more likely you are to have (blooms),” he said, especially if hot, dry conditions follow intense spring storms. Those extreme storms may become more frequent with global warming.

“We can’t answer one way or another what a drought will do,” Stumpf said, addressing this year’s dry conditions. In some areas, this summer’s heat led to earlier seasonal blooms. But in Lake Erie, drought this spring meant that little phosphorus washed into the lake, leading Stumpf and Reutter to predict that this year’s blooms will be just one-tenth the size of those in 2011.

An October 2011 satellite image of Lake Erie shows bright-green cyanobacteria blooms covering large areas of the lake.NASA MODIS data processed by R. Stumpf, NOAA

This chance reprieve has given the Lake Erie area time to try to control phosphorus runoff. “We’ve really bought, in many ways, an extra year to make improvements to sewage treatment plants and agricultural practices,” Reutter said. “But if we have a wet spring in 2013, we expect to see the bloom back again.”

Many people near the blooms complain of the smell – produced by ammonia and hydrogen sulfide as the cyanobacteria rot – using words like “putrid” and “gag.”

But worse, under conditions that scientists don’t completely understand, cyanobacteria can produce toxins that cause asthmalike symptoms, severe vomiting or diarrhea, or irritated skin or eyes. As in the Jenkins case, some of the toxins also act on the liver; this might also lead to cancer, if people are exposed over long periods of time. People and animals encounter the toxins when they swallow or swim in contaminated water or inhale water droplets suspended in air, according to the Ohio Department of Health.

Danny Jenkins’ experience is among the most serious to have been reported, though experts agree that many cases go unreported or are misidentified. The same year Jenkins fell ill, a YMCA camp on another Ohio lake closed its beach after 19 campers and staff became sick with stomach problems. Last summer, U.S. Sen. James Inhofe, R-Okla., reported stomach illness after swimming in Grand Lake, Okla., during a bloom. In Wisconsin alone, 98 people have reported illness from blue-green algae exposure over the past three years.

Dog deaths are all too common. Five dogs died after exposure to blue-green algae in a Kansas lake last year, and five died in Ohio in 2010. Dogs are particularly susceptible because they gulp water and often lick algae off their fur after a swim. Earlier this summer in Marion County, Kan., a rancher lost 22 cattle: They drank from a farm pond laden with a type of cyanobacteria that produces neurotoxins, according to a veterinarian involved in the case.

The blooms also repel tourists, harming summer vacation businesses around affected lakes. On Lake Petenwell, a large manmade lake in central Wisconsin, Tom Koren, owner of a marina, restaurant and bar called The Lure Bar & Grill, has seen the number of boat slips he rents fall by half.

“Typically, a bay like the marina will be caked from one shore to the other, solid green with iridescent blue, up to 6 inches thick,” said Koren, who co-founded a group called the Petenwell and Castle Rock Stewards, which aims to improve water quality on local lakes. “You’ll see squirrels walking on it.”

“People will come in and request their money back and take their boat elsewhere,” he added.

When cyanobacteria bloom in reservoirs that supply drinking water, they can clog pipes or poison the water. Utilities might have to truck in water or add extra treatment. When Lake Erie experienced its record-setting blooms last year, the city of Toledo was forced to spend an extra $3,000 to $4,000 a day treating the drinking water it drew from the lake. Even when large blooms aren’t present, nontoxic “taste and odor” compounds produced by the algae can give water a dirty taste. Wichita, Kan., spent several million dollars to add ozone treatment for the water it uses from Cheney Reservoir, where elevated levels of cyanobacteria are a regular occurrence.

Studies show that mixing fertilizer into the soil can reduce runoff by 50 percent and that no-till farming, in which plowing is minimized, can reduce sediment runoff by a third, Reutter said. Drainage from tiled fields also must be managed so that it doesn’t pollute waterways, he said.

“There isn’t any one particular strategy that is going to solve this problem for every farm,” said Tom Quinn, executive director of the Wisconsin Farmers Union. “But each farm has a set of things that they should be doing to protect the water around them and to protect their own soil.”

Meanwhile, Wisconsin’s Dunn County, which includes Lake Menomin and Tainter Lake, both notorious for their blooms, just passed a controversial ordinance requiring all waterfront property, including agricultural lands, to maintain an unmowed 35-foot-deep buffer strip along the water’s edge – a key strategy, experts agree, to soak up the runoff before it reaches the water. In addition, Wisconsin recently passed legislation to control phosphorus.

“We know what it takes to fix this stuff,” said Patrick “Buzz” Sorge of the Wisconsin Department of Natural Resources. “We just have to find the social and political will to get this done.”

This article was produced in collaboration with the Food & Environment Reporting Network, an independent, nonprofit news organization, focusing on food, agriculture and environmental health.

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Jessica Marshall