Toxic load building up at Muthukadu lagoon near Chennai could harm humans

Choking of the bar mouth and discharge of untreated effluents has resulted in toxic algal bloom. 
Algal bloom due to illegal discharge of untreated effluents and choking of bar mouth. (Photo| Shiba Prasad Sahu, EPS)
Algal bloom due to illegal discharge of untreated effluents and choking of bar mouth. (Photo| Shiba Prasad Sahu, EPS)

CHENNAI: In a major heath scare, Muthukadu lagoon on East Coast Road has become a ticking bomb loaded with harmful toxins that can prove fatal for humans as well as aquatic life. The entire water body, which is an important fishing ground, has turned green due to algal bloom.

This algae that causes discolouration is not an ordinary species. Marine biologists identify it as Cyanobacteria (Microcystis aeruginosa), a photosynthesizing bacteria commonly called blue-green algae that are capable of producing toxins (cyanotoxins) that affect the humans, fishes and shellfishes.

It has adverse effect on skin, liver or nervous system. Illegal discharge of untreated effluents and choking of bar mouth are causing the algal bloom, experts say.

They can also cause water quality deterioration associated with excessive biomass production (such as depleted dissolved oxygen levels, decline in fish population, and detrimental changes in water
quality).

Local fishermen are already reporting fish kill. A week ago, thousands of fish have washed dead near Karikattukuppam fishing village indicating the deterioration of the lagoon's health.

The water body is also used for recreation activities. Tamil Nadu Tourism Development Corporation (TTDC) operates a boathouse at Muthukadu. Sekhar, a fisherman in Kovalam said the fish catch has
drastically reduced in the lagoon and he blamed it on industrial and domestic waste discharge.

Central Institute of Brackishwater Aquaculture (CIBA), which runs an experimental station using the lagoon, has abandoned activities due to toxic algal bloom.

A team of five researchers led by S Vasudevan from Centre of Advanced Study in Marine Biology in Annamalai University in 2015 conducted an extensive study and published a research article in leading
international science journal 'Science Inventions Today' on how Muthukadu estuary is continuously reporting bloom of toxic algae year after year.

They recommended for regular monitoring to conserve the fishery resources and to protect human health.

Root cause for crisis

Joe K Kizhakudan, officer-in-charge, Kovalam Field Laboratory of Central Marine Fisheries Research Institute (CMFRI), told Express that the root cause for the crisis was choking of the Muthukadu bar mouth.

For last three months, the mouth is closed due to formation of sand bar. "For survival of any estuary, there should be constant exchange of seawater.

"When this stops, eutrophication happens. What is happening in Muthukadu is really worrisome. Due to the anthropogenic activities, high level of nutrients is carried into the estuary resulting in the bloom. The nutrients nitrogen and phosphorus along with solar radiation will enhance the algal growth," Kizhakudan said.

Eutrophication is a condition where the estuary is enriched with minerals and nutrients which induce excessive growth of algae and this process may result in oxygen depletion in the water body.

When contacted, GS Sameeran, Director of Fisheries, told Express that immediate steps will be taken to dredge the bar mouth. "I will also take up the issue to illegal discharge of untreated industrial and
domestic effluent into the estuary with the Tamil Nadu Pollution Control Board."

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