New Delhi, Dec 24 : Coral reefs, the most diverse marine habitat that support half-a-million species, may start losing dominance from Indian seas starting 2030 following increase in sea temperature, says a new study.

Scientists from the Central Marine Fisheries Research Institute, Cochin studied the coral vulnerability due to warming of Indian seas reef regions of the Andaman & Nicobar, Lakshadweep, the Gulf of Mannar and the Gulf of Kutch.

According to scientists, corals are among the most sensitive ecosystems to temperature changes, exhibiting bleaching - a process of whitening of corals when stressed by higher than normal sea temperature.

Indian coral reefs have experienced 29 widespread bleaching events since 1989 and 2002. Bleaching events and the ambient temperature at the time of bleaching provide scope for making projections, on the vulnerability of coral reefs with future warming of seas. The study was based on future projection of rise in sea temperature from 2000 to 2099.

"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 coasts in next 30-50 years," said scientist E. Vivekanandan, who led the study.

Corals are small animals that live in colonies and form reefs. The coral reefs are important marine ecosystem that act as life support system for million of coastal inhabitants in terms of coastal protection, nutrient cycling, recreation, tourism and fisheries.

"We studied the sea surface temperature date prior to, during and after 1998 coral bleaching events in the five regions and found that coral bleaching occurred when the maximum summer sea surface temperature exceeded 31 degrees Celsius and remained high for more than 30 days," said Vivekanandan.

The study found that the reef building corals may lose dominance between 2030 and 2040 in the Lakshadweep region and between 2050 and 2070 in the other four regions.

The results show that monthly sea surface temperature is predicted to increase to 34 degrees in all the regions of the Indian seas during 2000-99.

"The annual average sea surface temperature may increase by 3 degrees to 3.5 degrees in the Indian seas by the turn of this century. With rise in temperature, coral bleaching in all the five regions may exceed frequently until the middle of this century and almost every year after 2050," he said.

Scientists warn that catastrophic exposure is the most likely outcome of the bleaching by 2050.

"Given that recovery time of such a event is at least 10 years and 50 years for full recovery, this scenario would mean a non-coral dominated reef structure," he added. (IANS)