Kappaphycus alvarezi, an exotic seaweed, has invaded the northeast parts of the Mulli islet in Kilakarai coast in the Gulf of Mannar region where coral genus ‘Montipora’ used to be dominant, according to Suganthi Devadason Marine Research Institute (SDMRI).

The disturbing trend was noticed by the institute which studied the impact of the exotic seaweed in the Gulf of Mannar region, its Director J.K. Patterson Edward has said.

After finding that the seaweed had invaded over two sq.km. of coral reef areas in the Krusadai island in Mandapam coast of Gulf of Mannar, the State Forest Department removed them every year with funding support from Ministry of Environment, Forests and Climate Change and thereby checked the growth and proliferation of the seaweed on corals in the island.

“Though the impact to corals in Krusadai island is under control, the SDMRI researchers have noticed invasion of this exotic seaweed on the north-east direction of the Mulli island, about 40 km from Pamban, where coral genus Montipora was dominant,” Mr. Edward told The Hindu .

Fortunately there was no invasion of the seaweed in the five islands of Pullivasal, Poomarichan, Manoliputti, Manoli and Hare, located between Krusadai and Mulli islands, with rich coral cover, he said.

Corals in over 0.4 sq km area — mainly Montipora divericata and M. digitata — had died due to invasion of the exotic weed in Mulli Island, Mr. Edward said. The mortality had been severe because Montipora was very fragile, he said. The invaded area was very shallow and “presently the dead coral area in Mulli Island is dominated by both Kappaphycus alvarezii and other native algae,” he added.

“The good news is that that the other sides of Mulli island has coral genera such as Acropora, Echinopora, Pocillpora, Porites, Favia, Favites and Goniastrea and so far no invasion of the seaweed is found on them,” he said. The SDMRI researchers with Forest Department staff were regularly monitoring to save the corals from further depletion owing to invasion this exotic seaweed, he said.

Meanwhile, the environment ministry has, for the first time, sanctioned a three-year project on an outlay of Rs. 24.13 lakh to SDMRI to study the impact of exotic seaweed on corals and associated resources and to suggest management measures. The project, in association with the Forest Department, will begin in September.