At last the mystery is solved to what causes toxic blue-green blooms in freshwater that yearly kill thousands of aquatic organisms and make people sick.
In a previous post of mine, entitled “Runaway Toxic Microorganisms”, I introduced you to algal blooms and one of algae's infamous celebrities, Fireweed, a particularly nasty and prolific blue-green alga that pesters the Australian coastline and causes a nasty sickness to humans who come into contact with it.
Thanks to Sean Yeoman’s Consulting who brought my attention to a recent article in the Victoria Times Colonist by Ed Struzik (July 22, 2008), entitled “Scientists solve riddle of toxic algae blooms”, I came across the work of a limnologist-colleague of mine, David Schindler of the University of Alberta. According to the article, after 37-years of experimentation on Lake 227, a small pristine lake in the Experimental Lakes region of northern Ontario, Schindler’s team was able to pin down which chemical nutrients were key to triggering blue-green algal blooms.
"Phosphorous really is the key," said Schindler, whose study appears in the U.S.-based Proceedings of the National Academy of Sciences. "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." In a commentary in the Proceedings, American scientist Stephen Carpenter added that global expansion of aquatic "dead zones" caused by algae blooms is rising rapidly.
Currently 146 coastal regions in the world have been affected by elimination through lack of oxygen of fish and bottom-feeding life forms. One dead zone in the Gulf of Mexico is about the size of the city of New Jersey. And growing. Reminiscent of Fireweed. Off the coast of Sweden each summer, blooms of blue green algae turn the Baltic Sea “into a stinking yellow-brown slush that locals call rhubarb soup,” says Kenneth Weiss of the L.A. Times. “Dead fish bob in the surf. If people get too close, their eyes burn and they have trouble breathing.” Weiss goes on to describe cases of nuisance and toxic growths all over the world: jellyfish off the Spanish coast; toxic red tides off Florida; smelly green-brown algae off the coast of Maui. “North of Venice, Italy, a sticky mixture of algae and bacteria collects on the Adriatic Sea in the spring and summer. This white mucus washes ashore, fouling beaches, or congeals into submerged blogs, some bigger than a person.”
Algal blooms form part of the natural cycles of nature. They occur as a result of several factors that conspire to produce just the right conditions for algae to flourish. These include increased light, temperature and nutrients (which is why many blooms occur in the spring and summer). Blooms are usually associated with an aging system, where nutrients tend to concentrate from the years of natural filling in of materials.
During a “bloom” phytoplankton (floating algae) grow to hundreds to thousands or even millions of cells per milliliter. Fish kills usually happen from loss of oxygen as cells die and decompose. Toxic blooms occur when an algal species (mostly blue-greens) produces neurotoxins, usually under stress or as the cells are dying off; these blooms are typically called Harmful Algal Blooms, or HABs.
Fifty years ago, no one knew the exact cause of algae blooms in lakes and rivers. Evidence suggested that carbon, nitrogen and phosphorous, associated with agricultural runoff and waste water, were mostly responsible. But small-scale experiments weren't able to show which were more important. Then came Schindler’s groundbreaking experiments in northern Ontario in the 1960s and 1970s. I can still remember when I first saw the remarkable 1974 aerial photograph published by the journal Science, that showed two parts of Schindler’s experimental Lake 226. One side was treated with carbon, nitrogen and phosphorous. The other was treated with just carbon and nitrogen. The side that received phosphorous had rapidly developed a huge bloom of blue-green algae. The side without phosphorous addition remained in near-pristine condition.
The photo and the study that accompanied it became 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 to remove phosphorous from waste water. But that wasn’t the end of the issue. Researchers were still convinced that nitrogen played an important role in blue-green proliferation. The idea that nitrogen removal was needed to control the chemical buildup that causes algae blooms known as advanced "eutrophication" persisted.
Schindler's latest series of long-term experiments shows that nitrogen removal completely fails to control blue-green algae blooms in fresh water ecosystems. He proved this by manipulating nitrogen and phosphorus levels on Lake 227 for 37 years. Schindler found that nitrogen control only encouraged algae blooms. Stephen Carpenter predicted that a single-minded focus on nitrogen control would have disastrous consequences for aquatic resources around the world.
Schindler warns that the 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. Schindler recommended that governments pull out all stops to control phosphorous to protect wetlands that remove these nutrients from runoff before they reach lakes and streams. He also suggested that natural buffer zones be created to protect lakes and rivers from agricultural, municipal and cottage developments.
Nina Munteanu is an ecologist and internationally published author of novels, short stories and essays. She coaches writers and teaches writing at George Brown College and the University of Toronto. For more about Nina’s coaching & workshops visit www.ninamunteanu.me. Visit www.ninamunteanu.ca for more about her writing.