Global coral bleaching hit three spots along India’s coast
Surveys revealed that a rise of 2-3 degrees Celsius in sea-surface temperatures killed 16% of corals in GoM between March and October 2016.Updated: Jan 27, 2018 16:16 IST
Rising sea temperatures caused by climate change, which killed corals in different parts of the world during the third and longest global coral bleaching event between 2014 and 2017, also destroyed coral reefs in the Gulf of Mannar (GoM) and Konkan coast, new findings revealed.
The results of underwater surveys by the Suganthi Devadason Marine Research Institute (SDMRI), Tuticorn, revealed that a rise of 2-3 degrees Celsius in sea-surface temperatures killed 16% of corals in GoM between March and October 2016. An increase of one degree Celsius killed 8% corals around the Sindhudurg island fort in the Malvan Marine Sanctuary (MMS), in December 2015.
The extent of bleaching was more in MMS, with 70% corals affected in December 2015 — only 29% were found intact.
At GoM, about 23.92% corals bleached in April-June 2016. Another study earlier this month says in Lakshadweep, more than 30% corals were severely bleached between 1998 and 2016.
“The severe heat stress seen in 2014-17 caused widespread bleaching and mortality whether the reefs were locally stressed or highly protected. Reducing local stressers such as over fishing, destructive fishing, from pollutants such as fertilisers, sediments, and plastics, and from habitat destruction, increases the resilience of corals, increasing the odds they can recover from bleaching events,” said Mark Eakin, coordinator, US-based National Oceanic and Atmopheric Administration Coral Reef Watch.
Studies have shown that global temperatures in 2015, 2016 and 2017 were the warmest since instrumental record-keeping began in the 19th century.
Corals are particularly sensitive to temperature fluctuations. Their primary source of food is an algae living in their tissues, which converts sunlight into food, and also gives them their colour.
When sea-water temperatures rise by one or two degrees Celsius, corals expel these algae and as a result get bleached (or turn white) with a chance of recovery since they can survive for three months without food. However, if the temperature stress continues, corals die of starvation. The third global coral bleaching event was driven by climate change and El Nino, which was declared as the longest by US National Oceanic and Atmospheric Administration because of its occurrence across the Indian, Pacific and Atlantic oceans. Global coral bleaching was also recorded in 1998 and 2010.
Although they occupy less than 1% of the ocean floor, reefs — they are referred to as the rainforests of the oceans — are home for a million species, which includes one-fourth of the world’s fish. Additionally, they protect coastlines from erosion during storms and act as barriers against sea-level rise.
Globally, around 500 million people benefit from coral reefs, through fishing, recreation and tourism. Because of their importance, the International Coral Reef Initiative has declared 2018 as the third International Year of the Reef.
“In addition to maintaining biodiversity, the mortality of corals directly affects fishing as they serve as breeding grounds and shelter for fishes. Their death will also affect tourism as tourists go scuba diving or snorkeling to see corals,” said JK Patterson Edward, director, SDMRI. The Malvan study was in collaboration with the United Nations Development Programme (UNDP) and Bombay Natural History Society.