Kachchh (Gujarat): Sighting of coral bleaching along the Gujarat coast has prompted investigations to understand its nature, causes and effects.

Bleaching is whitening of corals as a result of death or expulsion of algal microorganisms called zooxanthellae that live in a crucial symbiotic relationship with corals.

“The coral reef ecosystems found in tropical seas are calcium carbonate exoskeleton of massive colonies of individual coral polyps which measure about a few millimetres in diameter. The polyps are dependent on photosynthetic unicellular algae – the zooxanthellae, for nutrition, which also give the corals their colour. Under stress (changes in water temperature, radiation levels, salinity, sedimentation etc) the polyps may expel these organisms, resulting in bleaching,” explained RD Kamboj, Director, Gulf of Kachchh Marine National Park.

Coral bleaching was reported from Mithapur Reef and Gulf of Kachchh Marine National Park, earlier this year. The sightings of bleaching as well as the ensuing investigations are a part of the WTI’s Coral Reef Securement Project which assists the Gujarat Forest Department in conservation of corals. The project is supported by Tata Chemicals Limited and World Land Trust.

“Bleaching of corals up to a certain extent is fairly common, reversible natural phenomenon and not necessarily alarming. The problem is when the degree is higher than the critical reversible limit which can result in large scale death of colonies,” said Dr Rahul Kaul, Chief Ecologist, WTI. “We are now monitoring the bleaching and recording the recovery rate. Preliminary signs are positive, as we have seen some signs of recovery in Mithapur. Also, new recruits have been observed which means that the corals are propagating.”

“As long as bleaching is seen, it is a sign that corals are not dead. However, bleaching can end either way… recovery or death, and monitoring it will help provide more insight on the situation,” said Alasdair Edwards, Emeritus Professor of Coral Reef Ecology, University of Newcastle, United Kingdom.