Coral breach: A silent, catastrophic invasion has happened in the Gulf of Mannar; here is how

Subject: Environment

Section: Biodiversity

Context:

An investigation of three coral colonies adjoining Kurusadai island of the Gulf of Mannar Marine National Park along the Tamil Nadu coastline, shows them to be grey and eerie, an indication of coral bleaching.

Kurusadai island:

It is one of the 21 uninhabited islands that form the Gulf of Mannar Marine National Park along the Tamil Nadu coastline.
The 21 islands came under the control of the forest department in 1986, which established the national park — a 10,500 sq km reserve that is a habitat for the rare seacow, dolphin and dozens of coral species — the same year.
Tourism was not allowed till 2022, after that it is being opened for tourism. The other 20 islands are still closed for tourists.

Coral bleaching due to Kappaphycus seaweed:

The corals provide shelter to myriad marine life, protect against storms and support livelihoods through fisheries and tourism.
Prime threats: Kappaphycusalvarezii, a seaweed (alga) species deliberately introduced in Ramanathapuram for commercial cultivation.
The International Union for Conservation of Nature lists it as one of the world’s 100 most invasive species.
As of 2021, Kappaphycus has invaded six of the 21 islands of the Gulf of Mannar.
The seaweed grows fast, doubling its size in 15-30 days, and thrives on live corals — unlike native seaweeds, which typically grow on dead corals.

Continued cultivation of kappaphycus:

Currently, about 750 farmers are engaged in seaweed farming, primarily Kappaphycus, in 18 villages of Ramanathapuram.
- Pudukottai, Thanjavur, Thoothukudi and Kanyakumari are the other four districts of the state where the alga is cultivated.
Kappaphycus is also likely to be cultivated in Tamil Nadu’s proposed seaweed park, proposed by the center in Union Budget for 2021-22.
- The park is likely to function as two hubs: a seaweed bank in Valamavoor village in Ramanathapuram and a processing hub for factories for seaweed products in Pudukottai.
In 2021, India cultivated around 34,000 tonnes of seaweed. The Centre earmarked Rs 600 crore to increase seaweed production to 85 million tonnes by 2025.
Industrial use of kappaphycus:
- National research institutes and companies are for increased cultivation of Kappaphycus to improve livelihoods, profits and to 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.
- India produces 100-132 tonnes of carrageenan a year and imports 1,800-2,000 tonnes.

Sequence of events:

In the 1960s commercial cultivation of kappaphycus began in its native land of the Philippines.
In the 1970s it was introduced in Hawaii, and spread to 6km from the area where it was introduced. It caused considerable damage to Coconut Island in Hawaii, Cubagua Island in Venezuela, Zanzibar in Tanzania, and Almirante and Cristobal in Panama and Costa Rica.
In 1984Kappaphycusalvarezii of Philippine origin from Japan was introduced in Okha, Gujrat and Mandapam town, Ramanathapuram of Tamilnadu by the CSMCRI.
In 2000, it was introduced in the Gulf of Mannar Marine National Park by PepsiCo. without a proper EIA.
The seaweed provided an annual income of ₹50000 to cultivators.
In 2005, the Goa-based National Institute of Oceanography noted signs of bio-invasion.
- The Tamilnadu government on 12 december 2005, prohibited cultivation of the species in sea waters between the north of Palk Bay and south of Tuticorin district.
In January 2014, the invasive species was discovered on a new base, Mulli island, located about 40 km south of Kurusadai.
By 2019, the exotic species had extended its range to Valai and Thalaiyari islands.
In 2021, a multi-departmental survey found bio-invasion of Kappaphycus in both Valai island and the southern part of Kurusadai island.

Livelihood at stake:

Repeated cultivation of the same fragment brought from Japan has reduced the quality and thus price of the seaweed.
Cost of seaweed farming is also high.