Climate change caused bleaching of coral reefs in the Gulf of Mannar owing to rising water temperature. In the Gulf of Mannar, annual summer bleaching normally starts by mid-April and intensifies in May, but this year it started by late March and the bleaching is already severe.
J.K. Patterson Edward, Director, Suganthi Devadason Marine Research Institute (SDMRI), Thoothukudi, said that if the present condition prevailed, the intensity would be very high in the coming months.
About 9.7 per cent of live corals on Vaan Island, 12.1 per cent on Koswari Island and 10.4 per cent on Kariyachalli Island had already bleached. Bleaching was presently taking place at a depth of 0.5 – 3.5 metres with water temperature hovering around 32.4 to 32.6ºC. Almost all varieties of corals – Porites lutea, P. solida, Favia favus, F. pallida, Favites abditta, Goniastrea pectinata – had started bleaching and most of them looked totally white on three islands in Thoothukudi Group, he told The Hindu here on Thursday.
He recalled that National Oceanic and Atmospheric Administration (NOAA ) of the USA in October 2015 declared the occurrence of third global coral bleaching. The report said that “record ocean temperatures cause widespread coral bleaching across Hawaii and the Caribbean Islands. The next concern is the further impact of the strong El Niño, which climate models indicate the occurrence of bleaching on Indian and Southeastern Pacific Oceans this year”. The first global bleaching happened in 1998, during a strong El Niño, and the second in 2010, during which 10 per cent of live corals in the Gulf of Mannar died due to bleaching when elevated temperatures (32.2 to 33.20 C) persisted for four months from April.
During December 2015, the west coast of India, witnessed severe coral bleaching (70-80 per cent) in Malvan, Dr. Edward said.
There was no major bleaching in the Gulf of Mannar between 2011 and 2015. But from the last week of this March, bleaching was observed sporadically in Thoothukudi group of Islands by SDMRI Reef Research Team.
The ecosystem services of coral reefs support millions of people worldwide, especially those in fisheries and tourism sector. While corals would be able to recover from mild bleaching, severe or long-term bleaching was often lethal, he said.