Increasing toxicity of algal blooms tied to nutrient enrichment and climate change

Oct 24, 2013
Like pea soup, a thick mat of toxic microcystins cyanobacteria on Lake Taihu in China gets stirred up in the wake of a boat. Credit: Hans Paerl, University of North Carolina

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 , or "eutrophication" increases, so will the proportion of toxin-producing strains of in , scientists said.

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researchers say, and today are once again adapting to new conditions in a way that threatens some of the life they originally made possible.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.

Toxic microcystin bacteria float, along with a dead fish, on the surface of this lake. Credit: Oregon State University

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

"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," he 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 United States, and based on the last EPA National Lakes Assessment, at least one-third may contain toxin-producing cyanobacteria. Dams; rising temperatures and 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 so massive that they are visible from outer space.

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.

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

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.

Also, since cyanobacteria blooms become entrenched and usually occur every summer in impacted systems, chronic exposure to 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," he said. "With a warming climate, rising carbon dioxide levels, dams on more rivers than not, and overloading of nutrients into our waterways, the magnitude and duration of toxic cyanobacterial blooms is only going to get worse."

Explore further: Far more displaced by disasters than conflict

More information: "Blooms Bite the Hand that Feeds Them," by H.W. Paerl et al. Science, 2013.

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User comments : 6

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rocket77777
2.8 / 5 (9) Oct 24, 2013
They should filter and capture them. Perhaps some fuel could be made or at least it would be carbon capture.
Sanescience
2.3 / 5 (9) Oct 24, 2013
Depends on energy density and how easily the toxins can be dealt with when concentrated I suppose.
NikFromNYC
1.5 / 5 (15) Oct 24, 2013
Bullshit on steroids: "Cyanobacteria are basically the cockroaches of the aquatic world, they're the uninvited guest that just won't leave."

The common term for them is "blue-green algae."

Any biology textbook points out that they are *not* a rare and toxic invasive species but one of the main pillars of the whole biosphere!
http://bioweb.uwl...Life.png

Tying fertilizer runoff to Global Warming promotion is brazenly dishonest when in fact it's the added carbon dioxide fertilization effect that is most greening the planet.

They have tainted the technical term "cyanobacteria" by association with "toxins" such as cyanide.

Outside of city apartments, cockroaches themselves are a grand part of the food cycle of our planet, as many a bird or lizard will agree.

This article is pure activism, fully divorced from real biology and thus also alien to real environmentalism for it insinuates that taxing air will solve old school ocean problems.
VendicarE
4.2 / 5 (5) Oct 27, 2013
NikkieTard... Does your biology text also tell you that Anoxic conditions often result from such algal growth?

It was clearly explained in the high school biology texts I used 30 years ago.

What is your excuse? Drugs? Alcoholic? No Girlfriend? She was begging for it?

The Alchemist
1 / 5 (12) Oct 27, 2013
@Nik-If CO2 is increasing, and I am not buying blindly into the Algoreithm, it is because of the "Dead Zones."
The ocean USED to have much more capacity to sink CO2 than man could ever produce. In 20 years this changed, and we blame production?

What is this flaw in human nature where we can't say fire is hot, or water is wet. We have to create these tangential lies?

It's bolluxing.
aroc91
5 / 5 (6) Oct 27, 2013
Leave the biology to the biologists, Nik.

Any biology textbook points out that they are *not* a rare and toxic invasive species but one of the main pillars of the whole biosphere!


Cyanobacteria are an integral and balanced part of the ecosystem when their growth isn't being rapidly spurred by fertilizer runoff. Where was the implication they're rare?

They have tainted the technical term "cyanobacteria" by association with "toxins" such as cyanide.


At normal levels, the toxicity is not an issue, but when they proliferate and overwhelm an ecosystem, it certainly is.

Outside of city apartments, cockroaches themselves are a grand part of the food cycle of our planet, as many a bird or lizard will agree.


I don't think anybody would disagree, but this doesn't concern ecologically sound conditions.