To find out the thermal threshold for coral bleaching, sea surface temperature (SST) data prior to, during and after the 1998 coral bleaching events in the Andaman Sea, Nicobar Sea, Lakshadweep Sea, Gulf of Mannar and Gulf of Kachchh obtained from NOAA/NASA satellite were plotted. From these plots, the Degree Heating Month (DHM) accumulations of the SST hotspot anomalies were estimated. The warming during the years 1985-2005 was correlated with Multivariate El Nino/Southern Oscillation Index (MEI). The results show increase in SST and MEI in all the five regions during the years of strong El Nino events. Coral bleaching occurred when the summer SST maxima exceeded 31oC and remained high for more than 30 days. The indices on thermal thresholds and DHMs estimated in this analysis can lead into projections on coral vulnerability to thermal stress in future in the Indian seas.

Coral bleaching; thermal threshold; Degree Heating Months