Lake waters turning venomous

Lake waters turning venomous

Sewage discharge into water bodies is producing cyanotoxins

Senthalir S. Bangalore



The 90-odd surviving lakes of Bangalore are turning into reservoirs of cobra venom-like toxins.
Studies conducted by Department of Environmental Science, Bangalore University have revealed that the unbridled discharge of sewage in the city's lakes has resulted in their eutrophication — a natural process whose end products are cyanotoxins which are equivalent to cobra venom in toxicity.
The eutrophication in these lakes is the natural consequence of organic pollutants flooding them. The proliferation of nutrients in the lakes has stimulated the rapid growth of plants and algae, clogging waterways and sometimes creating blooms of toxic blue-green algae.
"Eutrophication of lakes has led to the growth of cyanobacterial blooms, which produce some of the most potent toxins known as cyanotoxins that are equivalent to cobra venom in toxicity," said RK Somashekar, chairman, Department of Environmental Science.
Somashekar added that these cyanotoxins are potent enough to damage the liver and neurological system.
According to a World Health Organisation (WHO) report on eutrophication of water bodies, presence of 5,000 cyanobacterial cells per millilitre bio volume of water, poses a grave threat to human health and an alert needs to be sounded. The alert means immediate measures have to be taken to clear eutrophication. The cyanobacterial cell count going beyond the WHO alert levels, only means cyanotoxins are being produced.
"The rapid growth of plants and algae also shrinks the quantum of water spread drastically," he said and added that a monitoring system is important to prevent eutrophication and the subsequent pollution of lakes.
Unfortunately the city has no instruments like turbidity and haemocyto meters to measure the volume of cyanobacterial cells in water. "We will soon send a proposal to the central government to look into this issue," Somashekar said.
Detailing the measures to be taken to prevent eutrophication, Somashekar said that first a monitoring system has to be put in place. The first alert has to be sounded when there are 2,000 cyanobacteria cells per ml bio volume. External sources have to be identified and use of chemicals of nitrogen and phosphorous has to be reduced.