Corals in Gulf of Mannar feel the heat

Hariprasad A R THOOTHUKUDI The Hindu 21 Apr 19;

Around 2.5% bleaching witnessed during underwater study

Coral reefs in the Gulf of Mannar region, which were recovering well since the last mass coral bleaching witnessed in 2016, have once again started bleaching due to rising temperatures this summer.

During an underwater study by the Suganthi Devadason Marine Research Institute (SDMRI), the extent of bleaching was estimated to be 2.5%, of which 2% was partially bleached while 0.5% has suffered full bleaching.

Water temperatures of about 32°C have been recorded during the studies conducted at Pattinamaruthoor patch reef and along Kariyachelli island. “There was no major bleaching event in 2017 and 2018 after the third global coral bleaching event in 2016. The reefs had shown remarkable resilience since and as a result, there has been slow but steady coral recovery from 2017,” said J.K. Patterson Edward, Director of the SDMRI. “However, if the temperatures remain high for a prolonged period this year, the corals may die.”

Coral bleaching is a condition when coral polyps expel symbiotic algae, zooxanthellae, which provide them with food for growth and their normal healthy colour. If the stress continues, the corals may not recover leading to mortality.

Massive corals especially Porites sp. were the first to be affected, while other corals including Porites solida, P. lutea and Goniastrea sp. were among those fully bleached, while Acropora formosa, A. cytherea, Goniastrea sp., A. intermedia, A. nobilis, Montipora divaricata, M. foliosa, and Symphyllia sp. were among those partially bleached at the two sites.

The bleaching has been reported to the Ministry of Environment, Forests and Climate Change and the Government of Tamil Nadu.

Dr. Patterson said that anthropogenic pressures on stressed reefs from fishing and other activities should be minimised to aid recovery of the reefs.

Rapid surveys would be continued in other reef sites such as Mandapam and Kilakarai coasts and other areas throughout summer and pre-monsoon months to record and update the developments.