Genus-specific bleaching at Con Dao Islands, Southern Vietnam, June 2019

Abstract

± 26.1%), Montipora (10.1 ± 5.7%; Fig. 1A). Two genera Galaxea and Diploastrea did not suffer bleaching. Acropora with most branch and tabulate colonies were less impacted both in deep and shalow waters (0.9 ± 1.3% bleached; Fig. 1D - F). Hard corals in deeper waters exhibited a higher susceptibility to bleaching than their shallow counterparts (48% bleached in deeper transects compared with 15% in shallow transects). The findings were consistent with the higher abundance of the five most susceptible genera mentioned above in deeper (total mean cover ＝ 17.5%) than in shallow (2.2%) transects. An earlier bleaching event at Con Dao islands in October 1998 resulted in 37.8% of hard coral colonies bleached (Vo 2000). The 2019 event had both similarities and differences in impacts. Soft corals were the most susceptible in both events (100% bleached) and Galaxea remained consistently unbleached. In 2019, Pachyseris and Fungia had much higher levels of bleaching than in 1998, when these genera were little affected (7.7% and 8.3% bleached). In contrast, Diploastrea had no bleaching compared with 14% bleached in 1998. Porites was severely impacted at both events with 57% bleached and many dead massive corals covered by filamentous algae were recorded in October 1998. Acropora were among the susceptible genera with 19% bleached colonies together with many dead colonies observed in October 1998 (Vo 2000).