While the foam spilling onto the city’s coastline near Besant Nagar has caused some curiosity and raised some concern, marine biologists say it has nothing to do with pollution.
“This happens the world over. Intermittently, when the currents change or when the sea chemistry changes with the season, it can lead to this sort of formation,” said marine biologist Deepak Apte, deputy director, Bombay Natural History Society.
“In places like Australia, foam 10 feet tall has been recorded. This is one of those natural phenomena, the cause for which we do not have a proper answer as yet. Foam also occurs in areas where there is no pollution or run-off. Wind may be one factor causing it,” said Mr. Apte.
Another marine biologist with a Central University, who did not want to be named, said this kind of foam is called silk.
“It is a phenomenon that occurs when there is a change in the pH level of the water. You can this see in Pitchavaram near the mangroves, only the foam is brownish here, as the biological load is higher. Organic waste may have been pushed up by the sea during the northeast monsoon, and this could have caused it. The foam will not cause any kind of irritation on the skin. It will just fade and move away with the water,” he explained.
Fishermen, who have lived for generations in the area, too say the formation of foam is not a big deal.
“This year we have had very little foam in comparison with the past. There have been times when we have walked through stacks of foam that were taller than us,” said Karunakaran, a fisherman of Ururkuppam.
On Thursday, during high tide, the sea pushed some foam into the Adyar river, which, until about 5 p.m. had been placid.
According to fishermen, almost every December the foam arrives soon after the monsoon.
“We believe that the wind from the sea presses on to the waves, causing the sea to froth. There is nothing else to it. There is no harm done to the fish and the catch is normal. The sea is rough during this month. Sometimes, from afar, the foam looks like cotton bales,” said Joseph, a fisherman from Nettukuppam in north Chennai.
Meanwhile, the Tamil Nadu Pollution Control Board also collected water samples from both the Adyar river and the sea.
“We checked Chennai Metrowater’s sewage treatment plants and the discharge conforms to standards. Also due to the rains, the river has already been flushed out and whatever biological load was there in it has been diluted,” said an official of the Board.