Introduction of non-indigenous alien species is being reported nowadays as
one of the most serious and potential sources of stress to the marine systems. They cause disruptions of native communities and detrimental economic impacts on fisheries in many temperate marine
areas.

Increasing sea surface temperature (SST) and its consequences on marine ecosystems are widely discussed. Andaman Sea witnessed a few bleaching events during 1998, 2002 and 2005. The present study was taken up to assess the extent of bleaching during 2010 in selected reef sites in the Andaman through line intercept transect survey.

Ocean acidification (OA) refers to the ongoing decline in oceanic pH resulting from the uptake of atmospheric CO2. Mounting experimental evidence suggests that OA will have negative consequences for a variety of marine organisms. Whereas the effect of OA on the calcification of adult reef corals is increasingly well documented, effects on early life history stages are largely unknown.

The rising temperature of the world's oceans has become a major threat to coral reefs globally as the severity and frequency of mass coral bleaching and mortality events increase. In 2005, high ocean temperatures in the tropical Atlantic and Caribbean resulted in the most severe bleaching event ever recorded in the basin.

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