Tamil Nadu coral reefs in chokehold of exotic seaweed

Centre scheme promotes cultivation of ‘invasive species’ in State’s coastal villages

Published: 03rd October 2022 04:31 AM  |   Last Updated: 03rd October 2022 04:32 AM   |  A+A-

Seaweed cultivation

Seaweed cultivation

Express News Service

CHENNAI: The rich coral reefs of Gulf of Mannar Marine National Park and the seagrass beds in Palk Bay, where India’s first Dugong Conservation Reserve came up recently, have come under increasing threat from exotic seaweed Kappaphycus alvarezii. 

The latest joint field inspection carried out by members of the Research Advisory Committee of Gulf of Mannar Biosphere Reserve Trust, comprising wildlife officers and scientists from Central Salt and Marine Chemical Research Institute at Mandapam in Ramanathapuram district, found bio-invasion of Kappaphycus on coral reefs of at least two islands.

The inspection was conducted in August last year and TNIE has exclusive access to its confidential report, where it was stated that the coral reefs of Valai Island in the Keelakarai group and Krusadai Island of Mandapam group were dying due to stress from Kappaphycus invasion. Underwater images captured by divers recorded the invasion of Kappaphycus on Acropora branching corals. 

A vast contiguous stretch of branching coral area with a number of coral colonies of Valai island and affected due to Kappaphycus invasion was observed in the shallow sub-tidal regions in the representative sampling sites of the island.

“The Kappaphycus made a strong invasion and formed a thick gelatinous unbreakable mat within the coral branches which is intertwined and entangled and the observed coral colony also started dying from the bottom showing severe stress.”

The report also says the stretch of Kappaphycus continues to extend. The report says that even though it was manually removed from Krusadai island regularly, it regrew on live coral colonies.

Picture taken during field inspection
in Mannar shows bio-invasion
of Kappaphycus seaweed in corals

Details of the report gained prominence since the State fisheries department has identified 136 coastal villages in Palk Bay and the Gulf of Mannar for launching large-scale commercial farming of seaweed under the Multi-purpose Seaweed Park project announced by the Centre.

Environmentalists claim there is a huge industry lobby aggressively pushing for the cultivation of Kappaphycus, despite being aware of its ecological consequences.

Commissioner of Fisheries KS Palanisamy said a detailed project report was prepared and submitted to the Centre for approval. At the seaweed India-2022 conference held last week, Palanisamy said TN was planning to increase the production of seaweed from the current 15,000 tonnes to 2 lakh tonnes per annum, for which genetically improved Kappaphycus seed will have to be imported.

This is highly problematic given the fact that the global invasive species database maintained by the International Union for Conservation of Nature (IUCN) placed Kappaphycus on the ‘red list’. The Invasive Species Specialist Group of IUCN has described the Kappaphycus as “destructive invasive species and poses a serious danger to the coral reefs”.

The commercial significance of Kappaphycus lies in its role in the production of an industrially lucrative polymer called Carrageenan. Supriya Sahu, Additional Chief Secretary to the government in the Environment, Forests and Climate Change Department, told TNIE: “This is a complex issue. We cannot promote commercial cultivation of an invasive alien species inside or close to ecologically sensitive areas. Kappaphycus is an IUCN red-listed species, so we have to tread cautiously. A long-term impact assessment needs to be conducted. Scientists should identify and suggest the cultivation of native seaweed species, which will be beneficial for the fishermen as well as protect our ecosystem. Already, some of the islands in the Gulf of Mannar have been invaded by Kappaphycus.”

Sahu also said commercial cultivation of Kappaphycus in Palk Bay may also derail the State government’s efforts to conserve the dugong population since seagrass beds, which are their prime foraging grounds, are likely to be impacted. There are only about 240 dugongs present in the country and the majority of them are found in the Palk Bay region, as per data from the Wildlife Institute of India.

V Deepak Samuel, scientist, National Centre for Sustainable Coastal Management, said the bio-invasive potential of Kappaphycus was unquestionable but claimed that no spread of the exotic species was found in Palk Bay, where culture was underway for many years and the invasion on Krusadai Island could not be attributed to culture in Palk Bay. 

He said no seaweed cultivation should be allowed in reef areas.

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