Gulf of Mannar coral colonies dying due to exotic invasive seaweed

P. Oppili The Hindu 18 Nov 10;

The massive and branching coral colonies in the Gulf of Mannar region are dying due to cultivation of an exotic invasive seaweed species identified as Kappaphycus alvarezii.

J.K. Patterson, Director, Suganthi Devadason Marine Research Institute, Tuticorin, said their organisation was involved in regular monitoring of the coral reef colonies in the region since October 2008.

In October this year, when researchers from the institute visited the Shingle, Krusadai and Poomarichan islands, they observed the bio-invasion of the seaweed, which has spread over one square km in the region.

Mr. Patterson said more than 500 colonies of both the colonies were very badly affected.

With the cultivation of the seaweed, small coral reef colonies measuring 20 cm and larger colonies measuring up to 80 cm had been very badly affected, says Mr Patterson.

Cultivation of the sea alien seaweed on the luxuriant sea grass beds in the Palk Bay reduced penetration of sunlight into the coral colonies, which was very essential for their health and growth.

This led to stunted growth of reefs with less shoot density, turbid environment and less fish catch, he said.

The remedial measures the State Forest Department had taken to control the spread of the alien invasive species are not adequate, says Mr. Patterson. In his opinion every six months the seaweed needed to be removed. The Forest Department should allocate funds annually.

A government order issued in December 2005 clearly specifies that seaweed cultivation should be taken up in the north of Palk Bay, which is beyond Nagapattinam and South of Tuticorin coast.

The order also clearly mentions that in the event of any adverse impact during environment impact assessment study, permission to use the Coastal Regulation Zone area would be withdrawn, Mr. Patterson added.