Status and community structure of coral reefs in the Southern Vietnam

Abstract

Coral reefs are increasingly affected by climate change and local anthropogenic stressors (e.g., coastal development, sedimentation, and fishing pressure), and this necessitates post-disturbance assessments of reef condition and community structure. This study presents a large-scale evaluation of coral reefs in the southern waters of Vietnam following the 2016 and 2019 mass bleaching events, based on standardized benthic surveys conducted during 2022–2023 at 55 sites across six reef areas. A total of 51 coral genera were recorded, with pronounced spatial variation in generic richness, ranging from 18 genera at Ly Son to 41 genera at Con Dao. Mean hard coral cover ranged from 3.38–53.12%, with a regional average of approximately 24%. Offshore reef areas, particularly Con Dao and Phu Quoc islands, exhibited higher coral cover and more structured coral assemblages. Con Dao islands were characterized by a strong contribution of branching frameworkbuilding corals, whereas Phu Quoc was dominated by stress-tolerant massive taxa. In contrast, coastal areas along the central region consistently showed low coral cover and simplified community structure, with increased dominance of macroalgae and octocorals. Multivariate analyses revealed clear spatial differentiation in coral community composition among reef areas. These findings provide an updated baseline for assessing reef condition and developing informed conservation and monitoring strategies for coral reef ecosystems in southern Vietnam under ongoing environmental change.