Bioinvasive Seaweed Genus, Turbinaria in Coral Reefs of Gulf of Mannar

Coral reefs are the important marine biodiversity hotspots, providing livelihood for coastal population around the world. In recent times, coral reef ecosystems are facing natural and anthropogenic threats. Coral reefs in the Gulf of Mannar Marine Biosphere Reserve, southeast coast of Tamil Nadu, India are one of the peculiar ecosystems less studied. Thus, to unveil the potential threats in the coral reefs of Gulf of Mannar region, the present study has made several coral reef monitoring by Line Intercept Transect method in the Gulf of Mannar group of Islands. Surveys revealed the canopy-forming indigenous and invasive macroalgal species, Turbinaria ornata, T. decurrens and T. conoides overgrowing dead reef areas. Although these macroalgae are not an alien species in these islands, but have become increasingly abundant and competing against coral colonies for space. Underwater visual censuses have indicated Turbinaria species as opportunistic invaders. These species are taking the advantage of dead corals for substrata and thereby restricting the settlement of coral polyps. Dense growths of these species have formed patches with several 100s of thalli per m-2 and as continuous canopies in some dead reef areas. Further studies on spatial and temporal distribution of these invasive species are yet to be undertaken for developing better management strategies.