Scientists solve riddle of toxic algae blooms

Spiel · July 23, 2008

Scientists solve riddle of toxic algae blooms

Tuesday, July 22, 2008

EDMONTON - This is the time of year every cottage owner both loves and loathes.

On the one hand, there's the lovely lakeside cabin, offering refuge from the hustle and noise of city life.

On the other, there's the annual scourge of blue-green algae blooms spoiling the swimming, killing the fish and occasionally poisoning local drinking water.

After a remarkable 37-year experiment, University of Alberta scientist David Schindler and his colleagues have finally nailed down the chemical triggers for a problem that plagues thousands of freshwater and coastal ecosystems around the world.

By pumping various pollutants into Lake 227, a small pristine lake in the Experimental Lakes region of northern Ontario, they were able to pin down which chemical nutrients were key to triggering the blooms.

"Phosphorous really is the key," says Schindler, whose study is highlighted in the U.S.-based Proceedings of the National Academy of Sciences this week.

"Here in Alberta, it is especially important because the phosphorous content in the soil is naturally high, so you don't have to add a lot to create a serious problem."

It's a global problem. In a commentary in this week's Proceedings of the National Academy of Sciences, American scientist Stephen Carpenter said global expansion of aquatic "dead zones" caused by algae blooms is rising rapidly.

There are now 146 coastal regions in the world in which fish and bottom-feeding life forms have been entirely eliminated because of a lack of oxygen. One dead zone in the Gulf of Mexico is about the size of the city of New Jersey and growing.

Fifty years ago, no one knew what exactly caused algae blooms to appear on lakes and rivers. There was some evidence to suggest that carbon, nitrogen and phosphorous, which are associated with agricultural runoff and waste water, were responsible. But small-scale experiments weren't able to show which were more important.

Schindler seemed to solve the problem when he and his colleagues conducted a number of groundbreaking experiments in northern Ontario in the 1960s and early 1970s. In a famous 1974 aerial photograph published by the journal Science, two portions of their experimental Lake 226 were highlighted. One side was treated with carbon, nitrogen and phosphorous. The other was treated with just carbon and nitrogen.

The side receiving phosphorous rapidly developed a huge bloom of blue-green algae. The side not receiving phosphorous remained in near-pristine condition.

The photo and the study that accompanied it were pivotal in convincing governments in North America and Europe to ban phosphates from detergents and to ramp up or build thousands of new treatment plants that removed phosphorous from waste water.

That might have been the end of the debate. But over the years, the idea that nitrogen removal is needed to control the chemical buildup that causes algae blooms know as "eutrophication" has persisted.

Schindler's latest series of long-term experiments shows that nitrogen removal completely fails to control blue-green algae blooms. He proved this by manipulating nitrogen and phosphorus levels on Lake 227 for 37 years. Nitrogen control, he found, only encouraged algae blooms.

In a commentary published simultaneously in this week's issue of Proceedings of the National Academy of Sciences, Carpenter predicts that a single-minded focus on nitrogen control would have disastrous consequences for aquatic resources around the world.

Schindler warns that western Canada's struggle to control blue green algae is only going to get worse because industrial, agricultural and municipal growth is pumping more nutrients into water supplies that are decreasing in size and volume.

Not only does the government have to pull out all stops to control phosphorous, he says, it needs to protect wetlands that remove these nutrients from runoff before they reach lakes and streams. It also needs to set up rules that create natural buffer zones that protect lakes and rivers from agricultural, municipal and cottage developments.

johnnyb · July 24, 2008

experimental lakes? I had no idea they existed....any idea where this region is? Not that I want to go there....it would just be cool to know. Great article too, Spiel...thanks for digging this one up!

Dabluz · July 25, 2008

experimental lakes? I had no idea they existed....any idea where this region is? Not that I want to go there....it would just be cool to know. Great article too, Spiel...thanks for digging this one up!

Go here if you want an answer to your question. http://www.dfo-mpo.gc.ca/regions/central/p...rle/index_e.htm