CHENNAI: The US-based National Oceanic and Atmospheric Administration (NOAA) Coral Reef Watch, which is a global early-warning system for environmental changes in coral reef ecosystems, has issued a red colour-coded alert for the Gulf of Mannar in Tamil Nadu as "above normal" sea surface temperature (SST) is likely to trigger mass bleaching and coral mortality in the region.
This is a worrying sign as a hot summer is on the cards and a similar mass bleaching event in 2016 killed 16% of corals in the Gulf of Mannar Marine National Park. The park is home to 132 species of corals and one of the richest biodiversity hotspots in the world.
Tamil Nadu is already under the grip of a dry spell and the regional meteorological centre has issued a temperature warning on Tuesday saying, "due to humid air and high temperatures, hot and uncomfortable weather is very likely to prevail over Tamil Nadu. Maximum temperature is likely to be 2-3 degree Celsius above normal at isolated pockets of the state." IMD (Indian Meteorological Department) chief Mrutyunjay Mohapatra also recently said the prevailing El Nino conditions --- the periodic warming of waters in the central Pacific Ocean --- will continue through the summer increasing the number of heatwave days.
The global weather models are also indicating that 2024 is likely to be the warmest year and oceanologists are almost certain that SST will breach the threshold of 30 degrees Celsius and may even clock 33 degrees or above this year. If such harsh conditions prevail for an extended period of time, it may sound the death knell for most of the coral species.
Thoothukudi-based Suganthi Devadason Marine Research Institute (SDMRI), which closely monitors coral reefs in Gulf of Mannar with the support of the state forest department, confirmed that NOAA has issued ‘level 2’ coral bleaching alert, which means there is 60% probability of reef-wide bleaching with mortality of heat-sensitive corals.
IMD (Indian Meteorological Department) chief Mrutyunjay Mohapatra also recently said the prevailing El Nino conditions — the periodic warming of waters in the central Pacific Ocean — will continue through the summer increasing the number of heatwave days. Thoothukudi-based Suganthi Devadason Marine Research Institute (SDMRI), which closely monitors coral reefs in Gulf of Mannar with the support of the state forest department, confirmed that NOAA has issued ‘level 2’ coral bleaching alert, which means there is 60% probability of reef-wide bleaching with mortality of heat-sensitive corals.
"Currently, among the Indian reefs, ‘Alert Level 2’ has been predicted for the Lakshadweep Islands and the Gulf of Mannar reef areas between last week of May and June second week. Some parts of Andaman and Nicobar Islands have been predicted to experience Alert Level 1. These predictions, however, may undergo deviations (increase or decrease) depending on the variations in local climatic conditions such as wind, rainfall, cyclonic depressions, etc," K Diraviya Raj, associate professor, SDMRI, told TNIE.
During the recently concluded TN Climate Summit 2.0, a SDMRI study report titled "Coral Reefs of the Gulf of Mannar: Decadal Changes in Status and Management Paradigms" was released. The report said the live coral cover in Gulf of Mannar dropped from 37% in 2005 to 27.3% in 2021 because of mortality suffered during the previous mass bleaching events in 2010 and 2016.
SDMRI director JK Patterson Edward told TNIE, "There was gradual recovery after the bleaching events, which shows the Gulf of Mannar corals are resilient. However, the recovery rate is slow, considering the mass mortalities in 2010 and 2016. Our data shows the reef area cover has reduced from 11,060 hectares in 2005 to 6,628 hectares in 2021. Many regions that were used to be reef areas are now completely occupied by macroalgae. Out of the available 6,628 hectares, 2,631 hectares are currently in a degraded state." If another coral bleaching event strikes the Gulf of Mannar as predicted, the live coral cover will take a severe beating. "We will undertake rapid surveys with the help of the forest department to assess the situation," Patterson said.
Jagdish S Bakan, director, Gulf of Mannar Biosphere Reserve, told TNIE, "The department is keeping a watch and will undertake comprehensive monitoring. We have set up around 150 monitoring stations to check the health of corals and seagrass beds in Gulf of Mannar and Palk Bay."