Blue-Green Algae: Iridescent but Deadly

With another summer of increasingly ubiquitous cyanobacteria in lakes and rivers, the health and economic costs come into focus.


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 washed the dog off and, at some point, got some of the gunk in his left eye.

A few weeks later, Danny found himself in the hospital unable to feel his left side, with ulcers on his eye, slurred speech, stomach problems, and more, according to his wife Laura. At home, Casey began staggering and walking sideways. 

The dog's eyes turned yellow. On the day Danny 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 thought that his own symptoms came from the algal toxins he was exposed to while washing his dog. "The conclusion was he had encephalitis from algae bloom toxin," Dr. Wilfred Ellis of Lima, Ohio, said.

Cyanobacteria can produce toxins that cause asthma-like symptoms, severe vomiting, diarrhea, or irritated skin or eyes.

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

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 looks like pea soup. The blooms occur in nearly every state, peaking in August and September. Though no national agency tracks the blooms, experts say they are getting worse, driven by fertilizer and manure run-off into lakes and streams combined with a warming climate.

"Nationally, the problem is definitely growing," says 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 Caloosahatchie 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 well over a billion dollars from lost recreation and depressed property values.

IMG_1208.jpeg(Jessica Marshall)

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 hot 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 can also dump phosphorus into 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 says, 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 have recently 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 of a given field.

Climate change is also part of the picture, says Richard Stumpf, of the National Oceanic and Atmospheric Administration in Silver Spring, Maryland. "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.

'The marina will be caked from one shore to the other, solid green with iridescent blue, up to six inches thick... You'll see squirrels walking on it.'

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."

Presented by

Jessica Marshall, a contributor to the Food & Environment Reporting Network, is a science, environment, and health journalist based in St. Paul, Minnesota.. She has written for Discovery NewsNew Scientist, and Nature.

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