Role of corals reefs mangroves and seagrasses in enhancing productivity of the Gulf of Mannar coastal ecosystem in the Southeastern India and conservation measures

Abstract

The inter-relations between the coral, seagrass and mangrove ecosystems in newlinePoomarichan, Manoli and Hare Islands of Mandapam group of the Gulf of Mannar, newlineSoutheastern India was studied. Differences and similarities in the benthic community newlinestructure, fish population, planktons and physico-chemical parameters of these three newlinedynamic ecosystems were analysed. Exploitation of these ecosystems by the fishermen newlinecommunity was assessed by direct interview. newlineLive coral cover in all the three studied islands increased gradually from January newline2007 to December 2008. The increase of live coral cover in all three islands corresponds newlineto the increase of coral recruits through the study period from January 2007 to December newline2008. In total, 8 species of seagrasses were observed in all three islands; they are newlineThalassia hemprichii, Halophila ovalis, Halophila decipiens, Cymodocea serrulata, newlineHalodule pinifolia, Halodule uninervis, Syringodium isoetifolium and Enhalus acoroides. newlineAll the three islands are provided with mangroves and Manoli Island is having a high newlinemangrove cover. Physico-chemical parameters of the water samples from all three islands newlinewere conducive for both the reef and seagrasss ecosystems. If any of these parameters are newlinedisturbed in any of these ecosystems, it would affect all the ecosystems and eventually newlinethe fishery production and ultimately the economy of the fishermen. Plankton density newlinewas slightly higher in the seagrass area than in the reef area and the inter-connection and newlineexchange of plankton between coral and seagrass ecosystems provides good food supply newlineto the adjacent coral reefs. Fish abundance was fair in all three examined islands. It is newlineclear that these three ecosystems, coral reef, seagrass and mangrove are inter-connected newlinethrough the migration of fishes. In Gulf of Mannar, though mangroves in the islands do newlinenot play major role, seagrasses play key role in the fish abundance. The commercially newlineimportant reef fishes spend a lot of time in seagrass beds for various reasons. Moreover newlineseagrass beds act as nurse