Climate change induced coral bleaching and algal phase shift in reefs of the gulf of Mannar, India

Abstract

Algal phase shift established in bleaching suffered coral reef ecosystem of Gulf of Mannar Biosphere Reserve, South India has been evident in this study during summer 2010. Occurrence of coral bleaching in this region is due to increase in the sea surface temperature (SST), an indicator of climate change in the ocean as organisms respond physiologically to temperature. Bleaching was effective in massive corals when compared to branching coral colonies. Existence of unusual increase in SST for nearly 50 days has been inferred as the cause for bleaching. Mean SST in Gulf of Mannar is rising at the rate of 0.02°C per decade along with 0.1°C increase per decade in minimum SST. It was observed that massive coral forms have fast recovery from bleaching than the branching forms of corals. Non-recovered bleached branching coral forms were witnessed with high algal assemblage cover accompanied by native as well as exotic species. It is concluded that there is possibility of phase shift due to transformation of coral dominated system into algae dominated system in reef ecosystem of Gulf of Mannar, if the SST continuous to increase in future. Such shift will definitely affect the ecosystem services rendered by the coral reefs biodiversity available in the Gulf of Mannar reserve.