Pollution

Why there is an algal bloom in Gulf of Mannar and how it affects livelihood

A recent algal bloom in the Gulf of Mannar, caused allegedly due to pollution from Sri Lanka, highlights how fragile our coral reefs are

 
By V Sundararaju
Last Updated: Monday 28 October 2019
An algal bloom near the sea coast. Photo: Getty Images

Tamil Nadu is blessed with the second-longest coastline in India — 1,076 kilometres stretching from Pazhaverkadu in Thiruvallur district to Ezhudesam in Kanyakumari district.

Sixty per cent of the state’s population live within 100 kilometres of the coast. The rivers which originate from the Western and Eastern Ghats, join the sea in the state.

About 26 towns and 2,390 villages are located along the coast. About a million fishers in Tamil Nadu, who live in 608 fishing villages, depend on fisheries for their livelihood. The livelihood of the fishers is threatened due to depletion of natural resources owing to habitat destruction, pollution, and other factors.

In September 2019, the fishing community in Ramanathapuram, Tamil Nadu, was shocked as the sea water turned green and fish died in the thousands.

Scientists from the Central Marine Fisheries Research Institute in Kochi visited the spot, carried out a study and came to the conclusion that the incidents had taken place due to the sudden blooming of Noctiluca, a type of marine microalgae.

The cause of the fish deaths was assessed to be oxygen depletion caused by the sudden blooming of the microalgae. The fishers were advised not to worry as the algae would dissipate when there was a downpour and strong currents in the sea.

Scientists from the National Centre for Coastal Research (NCCR), Mandapam, have said that the Noctiluca scintillans algae bloomed suddenly due to the discharge of ballast water, subsequently causing the fish to die-off and the sea water turning green.

Blooming of the algae took place between the Gulf of Mannar and Mannar areas off the Sri Lankan coast. It could be possible that the discharge of the ballast water was from the Lankan coast.

According to forest department sources, it has been confirmed that while coral reefs were found dead at Shingle island near Rameswaram after blooming of the algae, no such activity was noticed in Krusadai Island, south of Pamban.

The Reef Research Team of the Suganthi Devadasan Marine Research Institute (SDMRI) has reaffirmed that algal blooming had killed about 180 coral reef colonies in Shingle Island.

Of corals and algae

The Ramanthapuram incident is just one example of how anthropogenic activity can cause great damage to the fragile marine ecosystem.

Algal bloom caused by nutrient pollution (nitrogen and phosphorus) can cause great harm to aquatic life due to the toxic content which they possess. While some algae can make animals sick, other creatures can die off in large quantities and deplete oxygen during the process of decomposition. Climate change also plays a major role in algal blooming.

When the algal bloom blocks the sunlight from reaching the algae within the coral, they cannot photosynthesise and create food for the corals. Besides, the depletion of oxygen due to algal decay also can have adverse impact on the coral.

As the coral reefs are damaged, they are not able to provide food and shelter to fish and other aquatic life. As a result, the livelihood of millions of people who depend upon the marine resources is jeopardised.

The harmful effects of algal blooming on coral reefs may be devastating and emergent attention should be paid to minimise our contributions to climate change and nutrient pollution in order to give the coral reefs a new lease of life.

The anthropogenic factors which are responsible for destruction of the marine environment are sewage, the plastic menace, sedimentation, industrial pollution, thermal pollution, salt pans, oil pollution, destructive fishing practices such as over-fishing, dynamite fishing, poison killing, trap fishing, bottom trawling, coral mining, etc.

The following environmental laws have been implemented for conserving the marine environment: The Indian Fisheries Act (1897), The Wild Life Protection Act (1972), The Water (Prevention and Control of Pollution) Act (1974), The Environment (Protection) Act (1986), The Coast Guard Act (1950) and Coastal Regulation Zone (CRZ) Notification (1991).

The Government of India has signed and ratified several international conventions relating to oceans and related activities namely the United Nations Convention on the Law of the Sea (UNCLOS) in 1982, International Convention for the Prevention of Pollution from Ships (MARPOL), 1973-1978, the London Dumping Convention in 1972, the Convention on Civil Liability for Oil Pollution Damage in 1969 and the Convention on Biological Diversity in1992.

MARPOL strives to protect the marine environment through elimination of discharges of oil and other harmful substances. MARPOL has recognised GoM as a ‘Special Area’ where discharges are especially restricted.

The issue of algal blooming due to release of ballast water from the ships off the coast of Sri Lanka is to be taken up with the government of Sri Lanka to prevent further damage to the marine environment on the Tamil Nadu side.

The pollution control board, the forest department and other connected agencies are to be geared up to monitor, regulate and control the harmful algal blooming caused by the release of pollutants from the salt manufacturing industries, aquaculture firms, chemical industries, etc, by implementing the related laws effectively.

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