Bleaching of coral in Nha Trang, Ninh Thuan, Con Dao and Phu Quoc islands in June–July 2019

Abstract

The studies on coral bleaching were conducted at 21 sites of 4 reef areas in Southern Vietnam, using point transect technique in June–July 2019. Cover of hard corals in the selected sites was quite high with the average values of 65.6 ± 18% % in Con Dao islands, 58.7 ± 26.2% in Ninh Thuan coastal waters, 55.9 ± 17.8% in Phu Quoc island but lower in Nha Trang bay (22.8 ± 15.9%). Soft corals were not abundant with the highest cover in Nha Trang bay (4.73 ± 5.5%) and the lowest in Ninh Thuan (0.16 ± 0.3%). Hard corals were most impacted in Nha Trang bay with 39.5 ± 8.1% bleached, followed by Ninh Thuan reefs (32.9 ± 13.3%), Con Dao Islands (25.0 ± 11.1%) and least affected in Phu Quoc island (7.3 ± 9.05%). For soft corals, ratios of bleached corals were 79.4%, 65.8% and 23.8% in Con Dao islands, Nha Trang bay and Ninh Thuan reefs respectively. No bleached soft coral was recorded in Phu Quoc. At the genus level, Acropora corals were severely affected in Nha Trang bay, Ninh Thuan reefs and Phu Quoc island but not impacted in Con Dao islands. The Porites, Montipora, Millepora genera were quite vulnerable in all sites but no bleaching was observed for Galaxea and Diploastrea genera.