Vulnerability of corals to warming of the Indian seas: a projection for the 21st century

Indian seas experienced severe warming in 1998 and 2002 that resulted in large-scale bleaching and mortality of corals. Anticipating increased warming in future,we made an attempt to project coral vulnerability in the Andaman, Nicobar, Lakshadweep, the Gulf of Man-nar and the Gulf of Kachchh regions for the 21st cen-tury. To project the number of bleaching events, the thermal threshold for bleaching, degree heating month (DHM) accumulations of the sea surface tem-perature (SST) hotspot anomalies, and the predicted increase in SST during this century were considered.The decadal DHM values are expected to gradually increase in all the five regions in the early decades of this century, but abruptly increase after the year 2050. The results indicate that if there is no increase in thermal tolerance capacity, bleaching would become an annual or biannual event for almost all reef regions along the Indian coast in the next 30–50 years. Reef building corals may lose dominance between 2030 and 2040 in the Lakshadweep region and between 2050 and 2070 in the other four regions