24 January 2011

Tales of woe coming from Lake Attitash (Amesbury, Massacheusetts, USA) – where invasive aquatic weeds and cyanobacteria are causing problems – mainly the plants at the moment.  Regrettably those involved see the two problems as separate issues, whereas in truth they are intrinsically-linked.  Managing them separately will simply make the problems worse!

There is lots of debate about how to attenuate nutrients and which to focus on – Lake Winnipeg is a prime example.  This is worrying as now is not the time to debate what causes eutrophication – but of course the costs of removing nutrients and fixing lakes are causing the authorities to duck and dive, to the eventual cost of the environment and society!  This particular debate is about whether nitrogen or phosphorus should be removed – which is odd for Canada since the findings of the Lake 227 debacle!

“After completing one of the longest running experiments ever done on a lake, researchers from the University of Alberta, University of Minnesota andthe Freshwater Institute, contend that nitrogen control, in which the European Union and many other jurisdictions around the world are investing millions of dollars, is not effective and in fact, may actually increase the problem of cultural eutrophication.

The dramatic rise in cultural eutrophication—the addition of nutrients to a body of water due to human activity that often causes huge algal blooms, fish kills and other problems in lakes throughout the world—has resulted from increased deposits of nutrients to lakes, largely from human sewage and agricultural wastes.

For 37 years researchers looked at Lake 227, a small lake in the Canadian Shield at the Experimental Lakes Area (ELA) in Ontario, Canada, and examined the best ways to control the cultural eutrophication process of lakes by varying the levels of phosphorous and nitrogen added to the lake.

“What we found goes against the practices of the European Union and many scientists around the world,” said David Schindler, professor of ecology at the University of Alberta and one of the leading water researchers in the world. “Controlling nitrogen does not correct the polluted lakes, and in fact, may actually aggravate the problem and make it worse.”

A previous study, entitled, A Survey of the State of the World’s Lakes, found that the cultural eutrophication of lakes has had a global effect. The continent percentage of lakes with cultural eutrophication were shown as:

Asia: 54 per cent Europe: 53 per cent North America: 48 per cent South America: 41 per cent Africa: 28 per cent (South Africa 42%)!

“The damage to these lakes is a major concern for virtually every continent,” said Schindler.The impact on human society is immense he says, as cultural eutrophication severely reduces water quality, which not only kills and contaminates fish, shellfish and other animals, but also can become a health-related problem in humans once it begins to interfere with drinking water treatment.

From India the state of the Kukkarhalli Tank (= lake) has been deplored, “The festering sewage flow emanating obnoxious smell is a perennial nuisance which has never been stopped for years while the citizens are assured of action. The water surface is dirty green with thick layer of rotting algae.”

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