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

The government plans a seaweed park in Tamil Nadu, ignoring the threat that Kappaphycus, a widely grown invasive seaweed, poses to corals in the Gulf of Mannar Marine National Park running along the state's coastline 

By Rohini Krishnamurthy
Published: Thursday 16 March 2023
Kappaphycus cultivation rafts on the coast of Mandapam town in Ramanathapuram, Tamil Nadu (Photographs: Manivasagan N)

Up close, a dead coral colony looks ghostly. Corals usually come in shades of green, brown, pink, yellow, red or blue. But a snorkelling investigation of three coral colonies adjoining Kurusadai, one of the 21 uninhabited islands that form the Gulf of Mannar Marine National Park along the Tamil Nadu coastline, shows them to be grey and eerie.

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.

Being a protected area, tourism was not allowed in the national park until March 2022, when Kurusadai opened its doors to tourists (the other 20 islands are still closed for visitors).

The corals, which provide shelter to myriad marine life, protect against storms and support livelihoods through fisheries and tourism, could have been the star attraction.

“But they are dead,” says S Mahendran, forest range officer at the Mandapam Forest Range in Tamil Nadu’s Ramanathapuram district, where the national park is located.

One of the prime threats that killed the corals near Kurusadai is Kappaphycus alvarezii, a seaweed (alga) species deliberately introduced in Ramanathapuram for commercial cultivation some two decades ago. The International Union for Conservation of Nature lists it as one of the world’s 100 most invasive species.

Down To Earth (DTE) visited the national park in October 2022 and accompanied the forest official on a routine undersea check of the corals near Kurusadai. Though there was no Kappaphycus in the three colonies, native seaweeds could be seen growing atop the lifeless corals.

This is not unexpected, the officials later explained. Corals and seaweeds are constantly locked in a battle. This dynamic can be compared with trees and weeds growing in a forest.

Marine algae seek corals since they provide support for growth. But live corals use their defence mechanisms to prevent a hostile takeover. Though corals can protect themselves from native seaweed, they lose to Kappaphycus.

“This exotic species has been accused of outgrowing and outcompeting live corals,” says Naveen Namboothri, founder-trustee of Dakshin Foundation, a non-profit based in Bengaluru.

The seaweed is dangerous because it grows fast, doubling its size in 15-30 days, and seeks out live corals to thrive on — unlike native seaweeds, which typically grow on dead corals.

Currently, about 750 farmers are engaged in seaweed farming, primarily Kappaphycus, in 18 villages of Ramanathapuram, says Abdul Kadhir, assistant director, fisheries.

Pudukottai, Thanjavur, Thoothukudi and Kanyakumari are the other four districts of the state where the alga is cultivated. As of 2021, Kappaphycus has invaded six of the 21 islands of the Gulf of Mannar, says Bakan Jagdish, Wildlife Warden and District/ Divisional Forest Officer, Ramanathapuram.

Kappaphycus is also likely to be cultivated in Tamil Nadu’s proposed seaweed park, says V Veeragurunathan, scientist at the Central Salt and Marine Chemicals Research Institute (CSMCRI). The Centre proposed this park in its 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, according to an official who wishes to remain anonymous. More seaweed parks may be set up in other states, says Veeragurunathan.

In 2021, India cultivated around 34,000 tonnes of seaweed, as per the Indian Council of Agricultural Research-Central Marine Fisheries Research Institute.

That same year, the Centre earmarked Rs 600 crore to increase seaweed production to 11.85 million tonnes by 2025, notes Veeragurunathan. He says researchers have initiated surveys to identify suitable locations and seaweed species, including Kappaphycus and indigenous species, for cultivation in nine maritime states.

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, says a paper published in Aquaculture International in May 2022.

The forest department, on the other hand, has been fighting to keep Kappaphycus from areas adjoining the protected coral areas. Officials say ocean currents have been transporting fragments of the alga into the Gulf of Mannar islands and would damage corals and their services, potentially robbing the fishing communities of fish catch — their main source of income. Sequence of events

Commercial production of Kappaphycus began in the 1960s in the Philippines, the native land of the species. It has since been introduced in over 20 nations.

Perhaps India should have been warned of the species’ invasive nature when it was introduced in Hawaii in the 1970s. Surveys showed that the seaweed spread from Hawaii Institute of Marine Biology — the initial introduction site — to reefs as far as 6 km.

The invasive species has also caused considerable damage to Coconut Island in Hawaii, Cubagua Island in Venezuela, Zanzibar in Tanzania, and Almirante and Cristobal in Panama and Costa Rica.

India’s tryst with the controversial species began in 1984, when CSMCRI acquired a small part of Kappaphycus alvarezii of Philippine origin from Japan. The institute introduced the new species in Okha, Gujarat, and later in Mandapam town, Ramanathapuram, under confined conditions to prevent it from escaping.

“For two years, it was in quarantine. It did not grow successfully in Okha; therefore, some fragments were transferred to Mandapam, where it grew,” says Veeragurunathan. Kappaphycus was successfully cultivated at Mandapam in 1997.

In 2000, the institute transferred the technology of cultivating Kappaphycus to PepsiCo. The company introduced it to the northern part of the Gulf of Mannar Marine National Park without a proper environmental impact assessment (EIA), as per a 2015 paper published in The News Journal of the International Society for Reef Studies.

In the following years, Kappaphycus began to be widely grown in coastal Tamil Nadu. Between 2001 and 2013, production of dry Kappaphycus jumped from 21 tonnes to 1,490 tonnes, as per a 2018 technical report by CSMCRI.

“Before Kappaphycus, we could eat only once a day. But the seaweed provided an annual income of Rs 50,000,” says Anadamma from Pamban Chinnapalam, a village in Mandapam.

In 2005, the adverse impacts of the exotic species began to appear. Scientists from the Goa-based National Institute of Oceanography noted signs of bio-invasion, similar to what played out in Hawaii.

They published their concerns the same year in Current Science. The Tamil Nadu government acted promptly and, in an order dated December 12, 2005, prohibited cultivation of the species in sea waters between the north of Palk Bay and south of Tuticorin district. The entire coast of Ramanathapuram falls in this stretch.

Until 2008, there were no field studies of the bio-invasion. That changed when researchers from Thiagarajar College, Madurai, published a paper in Current Science.

S Chandrasekaran and his team surveyed two sites in Kurusadai island and found that Kappaphycus had successfully established itself on corals. The alga forms a thick green mat, cutting off the coral’s ability to make food. It was smothering the corals, they wrote. The same year, PepsiCo made its exit, transferring its business to Aquagri Processing Pvt Ltd.

In 2008, scientists at the Tuticorin-based Suganthi Devadason Marine Research Institute (SDMRI) found the invasive alga in Shingle and Poomarichan Islands.

The following month, the forest department roped in Namboothri, who was then with the Indian Institute of Science (IISc), Bengaluru, and Kartik Shankar, IISc, to independently assess the situation.

“All coral polyps below the algal mat were dead. If left unchecked, and if no immediate remedial action is taken, the alga could spread to other parts of the marine protected area,” the duo warned in Current Conservation in 2010.

In 2011, the forest department swung into action by manually removing the alga within a 500 sq m area of Kurusadai. These operations, conducted yearly, are funded by both state and Central governments, says Jagdish.

Cleanup operations are not foolproof, though. Once Kappaphycus establishes itself firmly, it is impossible to separate the alga without damaging the coral colony. There is also possibility of algal fragments drifting off into the sea during removal, says a 2014 study in Current Science.

Meanwhile, Kappaphycus cultivation in India reached a peak. In 2012-13, Ramanathapuram had its highest yield of 1,500 tonnes dry weight. However, production hit a snag after 2013. In 2014, the yield dropped to 50 tonnes dry weight.

High sea surface temperature and bacterial infection were responsible, says Veeragurunathan. Still, the seaweed continued to pose a threat. In January 2014, the invasive species was discovered on a new base, Mulli island, located about 40 km south of Kurusadai, as per a 2015 study in Reef Encounter.

A Kappaphycus cultivation raft in the waters of Munnaikadu village in Ramanatha-puram; (right)  Kappaphycus- infested corals near Mulli island in the Gulf of Mannar Studied denial

Though the seaweed proponents acknowledge that Kappaphycus is harmful to corals, they maintain that cultivation in adjoining areas was not responsible for the damage to corals.

For example, a 2013 long-term assessment by the National Centre for Sustainable Coastal Management, CSMCRI, and Fisheries College and Research Institute, Tuticorin, did not directly attribute the spread to cultivation sites in Palk Bay.

But another long-term study by SDMRI, initiated in the same year, recommended halting the alga’s cultivation around Gulf of Mannar Marine National Park and Marine Biosphere Reserve areas.

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.

Veeragurunathan, who was also involved in the 2021 field survey, brushes aside the concerns. “Coral-seaweed interaction is a natural phenomenon. We found trace amounts of Kappaphycus. It is possible for the drifted material from Palk Bay (cultivation site) to move to the Gulf of Mannar,” he says, referring to the 2013-15 survey. He also counterquestions why corals in Palk Bay (cultivation areas) were unaffected from the seaweed.

The 2021 survey suggests that the Tamil Nadu government take appropriate policy decisions by not permitting cultivation of invasive exotic seaweed in and around coral reefs. Instead, it recommends cultivation of native seaweed.

“But native varieties provide a yield of only 60 kg per raft compared to Kappahycus’ 200 kg,” laments Mohammad Nooju, a seaweed farmer in Munaikadu

Besides, industries prefer Kappaphycus. The exotic species fetches Rs 51-70 per kg while the indigenous varieties get only Rs 45 per kg, says Veeragurunathan.

Livelihoods at stake

Some farmers have given up seaweed farming due to declining quality of Kappaphycus resulting from repeated cultivation of the same fragment brought from Japan.

Nooju says that the yield has nearly halved in the past decade. Anadamma pulled the plug seven years ago. “The seaweed has lost its vigour and certain fish also eat it,” she says.

CMSCRI has taken some steps, by distributing laboratory-created elite seaweed to farmers, which Veeragurunathan says show two times higher yield and growth.

“Only 20-25 kg have been given to farmers. That is not enough for 700 people. The laboratory seaweed fares only slightly better than conventional one. It is also likely that fresh Kappaphycus fragments could be reintroduced to India,” Khadir says.

But reintroducing new Kappaphycus could be dangerous, says a coral expert, speaking on condition of anonymity. “Once Kappaphycus damages the entire coral secosystem and the fishing habitat, what will the other fishers do?”

Cost of seaweed farming is another concern. The Pradhan Mantri Matsya Sampada Yojana scheme has announced a 60 per cent subsidy on bamboo rafts used to cultivate seaweed. The subsidy, which will be given in three instalments, brings down the effective cost of the Rs 1,500 raft to Rs 600 for farmers.

Panchammal, a resident of Mangadu village, says it has been six months since the first instalment. Without enough support from the government, companies appear to exploit seaweed farmers.

Aquagri pays farmers of Sambai and Mangadu villages roughly Rs 50 per kg even as the market price is around Rs 70. Farmers tell DTE they do not mind the low price as the company gives them raw materials for free. Khadir acknowledges the problem, saying most farmers live below the poverty line and it is better to provide them the full amount in one instalment.

This was first published in the 16-28 February, 2023 print edition of Down To Earth

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