CHENNAI: While a study by the Department of Marine Science in Bharatidasan University revealed the presence of the dangerous alga in the waters of the Muttukadu Lake, another report by the Department of Zoology, Sir Theagaraya College warned of high concentration of inorganic nutrients in the green waters. Highlighting the dangers posed by the presence of these nutrients, the study said that nitrate, while being an important nutrient, is toxic in high concentration and can disturb the aquatic environment.
While the acceptable limit is 0.5 mg per litre, the study published in the International Journal of Environmental Biology last year revealed that the nitrate value in Muttukadu estuary was 8.07 mg per litre and 5.11 mg per litre in the coastal water. “The excess concentration of nitrate and nitrite lead to excessive aquatic plant production which may negatively impact estuary water environment leading to depletion of dissolved oxygen and production of toxic alga. Oxygen depletion will lead to death of marine organisms,” the study warned.
Both studies also detected the presence of ammonia in the water. While the first report blamed it on sewage presence, the second study cited the algal bloom as a possible reason. Also, the hydrogen ion (pH) concentration - which controls the relative proportion of different chemicals - was found to be high. The first report measured it at 7.85 parts per million while the second one recorded it at 8.7 ppm. A level exceeding 10 ppm would be fatal for aquatic life.
“Pollution abatement facilities like sewage and domestic waste treatment at Muttukadu area are inefficient resulting in indiscriminate discharge of waste into the backwaters. Present investigation highlights the need of regular monitoring of harmful algal bloom and physico-chemical characteristics of the Muttukadu backwaters,” concluded the first study.
Officials, meanwhile, admitted that they had no clear data on the level of pollution in the lake. An official said untreated sewage waste gets dumped in the water body at midnight. He added that culprits included even some educational institutions in the neighbourhood.
“There has been no survey conducted by the Pollution Control Board. Even Directorate of Town and Country Planning turns a blind eye to the mushrooming of illegal constructions. Many of them do not have Coastal Regulation Zone clearance,” said an official from the Public Works Department, the custodians of the backwater. “We clean it up during the three months of monsoon so the mouth of the lake opens and joins the sea. The colour of backwaters will then change to bright blue. But it would last only for 15 days,” he added.
According to the official, the PWD lacks the funds to clean up the lake. He suggested that the tourism department and even the Salt Corporation that earn revenue from the lake pitch in to help clean up the water body. “If the lake has to be brought to its former glory, then all government institutions must work together with the support of the local public,” he added.