Marine heat causes record-high coral bleaching in Lakshadweep Sea

Extreme heat on the Indian coast and a marine heatwave have caused record high bleaching events affecting the coral reefs in the Lakshadweep Sea. A survey of various Lakshadweep Islands revealed that a significant percentage of hard coral species have undergone severe bleaching due to prolonged marine heatwaves affecting the region since late October 2023. The survey was conducted by researchers from the ICAR-Central Marine Fisheries Research Institute (CMFRI).

In Lakshadweep, the Degree Heating Week (DHW) indicator, which measures accumulated heat stress, has surged above 4 °C-weeks. According to the National Oceanic and Atmospheric Administration (NOAA), this level of DHW poses a significant risk of coral bleaching, threatening the region's diverse marine ecosystems.

“Such heat stress levels signify a severe threat to coral health, leading to extensive bleaching where corals lose the symbiotic algae (zooxanthellae), compromising their survival by depriving them of essential nutrients. If the DHW continues to rise beyond 12 °C-weeks, it could precipitate an unprecedented biodiversity crisis due to multispecies mortality,” said Dr K R Sreenath, senior scientist at CMFRI.

He further added that the ongoing heatwaves also threaten other critical marine habitats, including seagrass meadows. “Like corals, seagrass meadows are experiencing detrimental impacts due to the heatwaves, such as impaired photosynthesis, reduced growth, and hindered reproductive functions. The degradation of these ecosystems can lead to the collapse of local marine food webs, affecting a wide range of marine species, from fish communities to marine mammals like dugongs and dolphins,” he said.