High Sea Surface Temperature induces Local Coral Bleaching in Gulf of Mannar and Palk Bay regions, South East Coast of India – A Status Report

*¹Koushik Sadhukhan, ¹Ramesh C.H., ¹Shanmugaraj T., and ²Ramana Murthy M.V.

¹National Centre for Coastal Research, Ministry of Earth Sciences, NCCR Field Research Centre, Mandapam Camp, Tamil Nadu – 623519, India.

²National Centre for Coastal Research, Ministry of Earth Sciences, Pallikaranai, Chennai - 600 100, Tamil Nadu, India.

*Corresponding E-mail Address ✉: sadhukhan.1985@gmail.com

ORCID ID: Koushik Sadhukhan - 0000-0003-2361-3929, Ramesh Chatragadda - 0000-0002-8838-0583,T Shanmugaraj - 0000-0002-4860-7317, M.V. Ramana Murthy 0000-0002-6219-2728

Accepted August 25, 2020

Coral bleaching in Gulf of Mannar and Palk Bay was encountered while intensive reef health monitoring surveys conducted during the month of April to May, 2019. Surveys were carried out at 12 different locations of Gulf of Mannar and 2 locations of Palk Bay region. Reef building coral genera Porites sp., Acropora sp., Montipora sp., Favites sp., and Dipsastraea sp. were found to be affected by this bleaching event. The level of bleaching was 15.9% in Mandapam group, 31.0% in Keezhakarai group, 27.3% in Vembar group, 25.6% in Tuticorin group and 85.0% in Palk Bay group. High Sea surface temperature (32.5°C - 35.6°C) recorded during the month of April and May was about 4°C - 5°C, which is more than the average temperature range (26°C - 30°C) recorded in Gulf of Mannar and Palk Bay. Among the different live coral forms, massive corals (36.0 %) were more vulnerable than other branching coral forms. In Palk Bay, bleaching was observed only in massive corals upto a depth of 5m. Soft corals Sinularia sp, Sarcophyton sp. were also partially bleached in Gulf of Mannar. No bleaching was observed at more than 5m depth. A total of 23 species were assessed to estimate the degree of bleaching under the category of complete bleached, partially bleached and non-bleached. The study highlighted that bleaching is species specific and depth specific. Branching corals showed high adaptive resilience than massive corals in Gulf of Mannar and Palk Bay in comparison to previous bleaching event which could be a good sign of quick recovery of reef areas.

Key words: Branching corals, Coral Bleaching, Gulf of Mannar, Massive corals, Palk Bay, Sea Surface temperature, Symbiodinium spp.

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