The city has been under attack from buzzing swarms of mosquitoes. And, a misunderstanding is probably the cause of it all.

Student Sea Turtle Conservationist Network (SSTCN) activists and the Public Works Department (PWD) have been working at cross purposes, it turns out.

While PWD claims complaints from the conservation lobby hampered desilting work along the Adyar river mouth, activists insist the complaint was against just the removal of sand from the shore.

Between the two, however, Chennai has been trapped in an annoying, incessant buzz that could prove dangerous.

Stagnation of water, especially untreated effluents, let out into the sea will increase larval and mosquito density, especially at the mouth of the river, according to experts at the Directorate of Public Health.

Polluted water allows for rampant breeding of culex mosquito, known to cause filariasis or elephantiasis. Flushing the river with salt water (from the sea) will help in curbing the breeding of mosquitoes to an extent, said S. Elango, former director of public health.

It was sheer torture by mosquitoes that drove some Adyar residents, including T.V. Antony, former chief secretary, to investigate the issue. They marched up the river bed on Monday only to encounter two obstacles — construction debris dumped under the old Adyar bridge, and a huge sand bar at the mouth of the river.

The residents contacted officials of the Chennai Corporation and PWD. On Wednesday, an earthmover was engaged to remove the sand bar. The PWD has been traditionally involved in desilting the mouths of the Adyar and Cooum for years, an official said.

“As the river mouth has not been cleaned for a while now, owing to protests from environmentalists, there are heavy sediments along the waterway and the stagnant flow has led to breeding of mosquitoes,” he said.

On Wednesday, the river mouth was opened up to 20 metres to 25 metres, and to a width of two metres.

According to Akila Balu of SSTCN, “We only opposed the removal of sand from the seashore near Foreshore Estate, not dredging of the sand bar at the mouth of the river. Mosquitoes are a menace to everyone, why would we oppose measures to prevent their breeding?”

PWD now proposes to take up dredging work in Adyar river every 15 days, as is the practice along the Cooum, to prevent mosquito breeding.