There is a field research station in the Gulf of Mannar region, by the National Centre for Coastal Research, an institute under the Ministry of Earth Sciences, India. Dr Shanmugaraj who is leading the researchers has found an alarming pattern of bleaching in the reefs in Mandapam, Keezhakkarai and Palk Bay.
It has been found by them that there was no bleaching seen at sea surface temperature ranging from 28.7°C to 31°C in the August 2018-February 2019 period. But researchers observed a pattern of bleaching in corals when the temperatures rose to between 32°C and 36°C between March 2019 and May 2019 and that was different at different layers within the sea.
As coral bleaches, it will not die but comes pretty close to it. Some may survive the experience and recover once the sea surface temperature returns to normal levels. Around 12% of coral species found at depths between 0m and 2m like Porites solida, Poritis lutea, Montipora digitate, Acropora hyacinthus were completely bleached.
Around 5% of species found at depths between 2m and 4m were partially bleached such as Acropora formosa, Acropora hyacinthus, Montipora digitata, Montipora foliosa, Pocillopora damicornis, Goniastrea retiformis, Platygyra sinensis, Dipsastrea favus, Dipsastrea speciosa. At depths from zero to 4 metres, Porites species observed in Palk Bay region were completely bleached. At depths over 5m corals did not face bleaching.
The important hotspots of biodiversity in the ocean are Coral reefs.