Quantcast

Toxic Algal Blooms Connected to Climate Change and Industrial Agriculture

Climate

Nutrient enrichment and climate change are posing yet another concern of growing importance—an apparent increase in the toxicity of some algal blooms in freshwater lakes and estuaries around the world, which threatens aquatic organisms, ecosystem health and human drinking water safety.

As this nutrient enrichment, or “eutrophication” increases, so will the proportion of toxin-producing strains of cyanobacteria in harmful algal blooms, scientists said.

Toxic microcystin bacteria float, along with this dead fish, on the surface of freshwater lakes. Photo credit: Oregon State University

Researchers from Oregon State University and the University of North Carolina at Chapel Hill will outline recent findings in an analysis Friday in the journal Science.

Cyanobacteria are some of the oldest microorganisms on Earth, dating back about 3.5 billion years to a time when the planet was void of oxygen and barren of most life. These bacteria are believed to have produced the oxygen that paved the way for terrestrial life to evolve. They are highly adaptive and persistent, researchers say, and today are once again adapting to new conditions in a way that threatens some of the life they originally made possible.

A particular concern is Microcystis sp., a near-ubiquitous cyanobacterium that thrives in warm, nutrient-rich and stagnant waters around the world. Like many cyanobacteria, it can regulate its position in the water column, and often forms green, paint-like scums near the surface.

In a high-light, oxidizing environment, microcystin-producing cyanobacteria have a survival advantage over other forms of cyanobacteria that are not toxic. Over time, they can displace the nontoxic strains, resulting in blooms that are increasingly toxic.

“Cyanobacteria are basically the cockroaches of the aquatic world,” said Timothy Otten, a postdoctoral scholar in the OSU College of Science and College of Agricultural Sciences, whose work has been supported by the National Science Foundation. “They're the uninvited guest that just won't leave.”

A thick mat of toxic microcystins cyanobacteria on Lake Taihu in China gets stirred up in the wake of a boat. Photo credit: Hans Paerl/ University of North Carolina

“When one considers their evolutionary history and the fact that they've persisted even through ice ages and asteroid strikes, it's not surprising they're extremely difficult to remove once they’ve taken hold in a lake,” Otten said. “For the most part, the best we can do is to try to minimize the conditions that favor their proliferation.”

Researchers lack an extensive historical record of bloom events and their associated toxicities to put current observations into a long-term context.  However, Otten said, “If you go looking for toxin-producing cyanobacteria, chances are you won't have to look very long until you find some.”

There are more than 123,000 lakes greater than 10 acres in size spread across the U.S., and based on the last U.S. Environmental Protection Agency's National Lakes Assessment, at least one-third may contain toxin-producing cyanobacteria. Dams, rising temperatures and carbon dioxide concentrations, droughts, and increased runoff of nutrients from urban and agricultural lands are all compounding the problem.

Many large, eutrophic lakes such as Lake Erie are plagued each year by algal blooms so massive that they are visible from outer space. Dogs have died from drinking contaminated water.

Researchers studying cyanobacterial toxins say it’s improbable that their true function was to be toxic, since they actually predate any predators. New research suggests that the potent liver toxin and possible carcinogen, microcystin, has a protective role in cyanobacteria and helps them respond to oxidative stress. This is probably one of the reasons the genes involved in its biosynthesis are so widespread across cyanobacteria and have been retained over millions of years.

Because of their buoyancy and the location of toxins primarily within the cell, exposure risks are greatest near the water's surface, which raises concerns for swimming, boating and other recreational uses.

Researchers take samples from Lake Taihu in China, when it was heavily contaminated with toxic algal blooms that turned the surface water green. Photo credit: Oregon State University

Also, since cyanobacteria blooms become entrenched and usually occur every summer in impacted systems, chronic exposure to drinking water containing these compounds is an important concern that needs more attention, Otten said.

“Water quality managers have a toolbox of options to mitigate cyanobacteria toxicity issues, assuming they are aware of the problem and compelled to act,” Otten said. “But there are no formal regulations in place on how to respond to bloom events.

“We need to increase public awareness of these issues,” Otten concluded. “With a warming climate, rising carbon dioxide levels, dams on many rivers and overloading of nutrients into our waterways, the magnitude and duration of toxic cyanobacterial blooms is only going to get worse.”

Show Comments ()

EcoWatch Daily Newsletter

"Take the pledge today." Screenshot / StopFoodWasteDay.com

Did you know that more than a third of food is wasted or thrown away every year? And that only 25 percent of it would be enough to feed the 795 million undernourished people in the world? That's why today is Stop Food Waste Day, a chance to reflect on what you can do to waste less of the food you buy.

Stop Food Waste Day is an initiative of food service company Compass Group. It was launched first in the U.S, in 2017 and went global the year after, making today it's second worldwide celebration.

Read More Show Less
Pexels

By Franziska Spritzler, RD, CDE

Berries are among the healthiest foods you can eat.

Read More Show Less
Sponsored
Flames and smoke are seen billowing from the roof at Notre-Dame Cathedral on April 15 in Paris, France. Veronique de Viguerie / Getty Images

When Paris's Notre Dame caught fire on April 15, the flames threatened more than eight centuries of culture and history. The fire evoked shock, horror and grief worldwide. While the cathedral burned, French President Emmanuel Macron expressed determination to rebuild what the French regard as a sacred site.

Read More Show Less
An artist's impression of NASA's InSight lander on Mars. NASA / JPL-CALTECH

Scientists have likely detected a so-called marsquake — an earthquake on Mars — for the first time, The National Aeronautics and Space Administration (NASA) announced on Tuesday.

Read More Show Less
Hero Images / Getty Images

Across the political aisle, a majority of American parents support teaching climate change in schools even though most teachers currently do not.

Read More Show Less
Sponsored
Priit Siimon / flickr / cc

By Andrea Germanos

Lawyer and visionary thinker Polly Higgins, who campaigned for ecocide to be internationally recognized as a crime on par with genocide and war crimes, died Sunday at the age of 50.

She had been diagnosed with an aggressive cancer last month and given just weeks to live.

Read More Show Less
Pixabay

An E. coli outbreak linked to ground beef has spread to 10 states and infected at least 156 people, CNN reported Wednesday.

Read More Show Less
The Anopheles stephensi mosquito, which carries malaria. CDC / Jim Gathany

The world's first malaria vaccine was launched in Malawi on Tuesday, NPR reported. It's an important day in health history. Not only is it the first malaria vaccine, it's the first vaccine to target any human parasite.

Read More Show Less