Coral breach in Gulf of Mannar

Why in news ? The dead coral reefs were observed near Kurusadai (Tamil Nadu), one of the 21 uninhabited islands forming the Gulf of Mannar Marine National Park.

Background:

• The massive and branching coral colonies in the Gulf of Mannar region are dying due to cultivation of an exotic invasive seaweed species identified asKappaphycus alvarezii ( algae)
• Shingle, Krusadai and Poomarichan islands, observed the bio-invasion of the seaweed, which has spread over one square km in the region.

Impact of sea weed

• Cultivation of the sea alien seaweed reduced penetration of sunlight into the coral colonies, which was very essential for their health and growth.
• The algae was firmly attached to the coral colonies and started forming mat over them, eventually smother and kill corals.
• It led to stunted growth of reefs with less shoot density, turbid environment and less fish catch.
• Macrofaunal and fish density decreased when Kappaphycus cover increased.

Seaweed utility

• Kappaphycushas the potential to improve livelihoods, profits to  the native farmers and used in food, cosmetics, and medicines.
• It’s cultivation reduce India’s import of kappa-carrageenan, a polysaccharide extracted from the alga that finds use in industrial gums and as a smoothening agent in ice cream, toothpaste, jellies, medicines and paint.
• In the meat industry, it is used to ensure that meat retains its tenderness while transporting or exporting.
• It is source of nutrition, containing anti-inflammatory and anti-microbial agents.
• Acting as a bioindicator by absorbing excess nutrients and balancing out ecosystems.
• Mitigates climate change by sequestering carbon dioxide termed as ocean afforestation.
• If livestock is fed with seaweed, methane emission from cattle may be reduced substantially.
• Used as fertilizers to increase fish production.
• Buried in beach dunes to combat beach erosion.

Threats:

• IUCN has described the Kappaphycus as “destructive invasive species.
• Cannot promote its commercial cultivation in ecologically sensitive areas.
• Threat to Dugong population, since seagrass beds, which are their prime foraging grounds, are likely to be impacted.

Kappaphycus Production in India

• In 2021, India cultivated around 34,000 tonnes of seaweed, and the Centre earmarked Rs 600 crore to increase seaweed production to 11.85 million tonnes by 2025.
• Currently, about 750 farmers are engaged in seaweed farming, primarily Kappaphycus, in 18 villages of Ramanathapuram, Tamil Nadu and it is also likely to be cultivated in Tamil Nadu’s proposed seaweed park.

Measures undertaken

• Order was issued restricting the cultivation of the exotic species only to the seawaters north of the Palk Bay and south of Thoothukudi coast.
• Forest department carrying out manual removal of the seaweed to protect the coral reefs.