Study taken up in area between Pamban and Adhirampattinam in two phases from 2008
The 130-km-long stretch between Pamban and Athiramapattinam in the Palk Bay coast has a treasure of luxuriant seagrass beds, according to Suganthi Devadason Marine Research Institute (SDMRI).
The Tuticorin-based research institute which had taken up a comprehensive underwater survey and assessment of seagrass beds in the Palk Bay in 2008, has completed its study in February this year, and found that the coastline has 254 square km of seagrass cover.
Giving details of the findings, SDMRI director J.K. Patterson Edward said the study was taken up in the area between Pamban and Thondi in the first phase and up to Athiramapattinam with the support of Mangroves for the Future Programme of International Union for Conservation of Nature and Natural Resources (IUCN) in the second phase.
“The coastline has all the 14 species of seagrass found all over the world and Thalassia hemprichii, Syringodium isoetifolium and Cymodocea serrulata are the dominant species,” he told The Hindu.
The luxuriant growth was seen in Puthupattinam, Mullumunai and Thondi zones, he said.
He said the 130-km-long coastline was divided into 23 zones for detailed data collection like seagrass percentage composition, species diversity, shoot density, biomass, epiphytes, macro faunal assemblage, fish population, distribution pattern and abundance.
The distribution from shore towards marine zone ranged between 3.5 km and 8.56 km. While the zones of Vethalai, Iranianvalasai, R.Puthur, Kottaipattinam and Athiramapattinam had seagrass cover from a distance of 7 km from shore, the minimal cover in other zones was up to 3.5 km from shore, he said. The shoot density ranged between 91 and 526 square metres, he added.
He said fishermen in more than 50 coastal villages in the stretch depend on seagrass-associated fisheries for their livelihood.
A recent questionnaire survey among the fishermen revealed the presence of dugong population along the stretch and the estimated occurrence was 34 and 105 numbers which, he said, was highest among all Indian waters.
“The treasure of the Palk Bay, however, faces threat from human beings and nature,” Mr.Edward said, adding that over 20 per cent of healthy seagrass beds were already degraded in the stretch. “Use of bottom trawling, shore seine and push nets by the fishermen is leading to their degradation,” he noted.
The indirect land-based threats included increase in sediment loads, high levels of increased nutrients from sewage disposal and cultivation of exotic seaweed on seagrass beds.
Sometimes cyclones and strong winds may even uproot and erode wide shallow water areas, he said.
“The fishery production, sediment binding and carbon sink services that seagrass beds provide can only be sustained by preserving their health and extent,” he pointed out.
He said the SDMRI had collected the baseline data in the Palk Bay, but focused conservation and research plan with sufficient funding was the need of the hour to conserve these underwater treasures for the benefit of the dependent coastal community and the protection of biodiversity.