Impacts of a super typhoon on coral diversity, substrates and reef fish assemblages on nearshore reefs in Wenchang, northern South China Sea

Typhoons are among the most intense natural disturbances shaping tropical and subtropical coral reefs. Wenchang, on the eastern coast of Hainan Island, lies within a high landfall-frequency zone of the western North Pacific. On 6 September 2024, Super Typhoon Yagi (ID: 2411) made landfall near Wengtian, causing severe impacts on nearby reef habitats. We conducted paired surveys of representative nearshore reefs in August 2024 (pre-event) and September 2024 (post-event) to assess effects on coral cover, reef fish assemblages and benthic substrates. Following the typhoon, live coral cover declined markedly and variability among sites increased. Encrusting and foliose corals contracted sharply, whereas massive corals remained dominant but also decreased slightly. Benthic substrates shifted from being largely covered by macroalgae, sponges and soft corals to rubble–sand dominated states, indicating physical removal of biotic cover and associated habitat damage. Coral species richness decreased from 24.6 to 18.0, and Shannon diversity and evenness declined from 2.45 to 2.13 and from 0.771 to 0.765, respectively, indicating a reduction in α -diversity and fewer co-occurring species rather than an outright collapse of overall diversity structure. Reef fishes showed parallel but distinct responses: total abundance declined substantially (482→289), species richness decreased slightly (13.2→12.0), and dominance structure shifted, with higher Shannon diversity and evenness ( H’ : 1.55→1.92; J’ : 0.651→0.809) and a steeper rank–abundance curve. Dominant corals and fishes both turned over and shifted toward disturbance-tolerant taxa, revealing a multidimensional response characterized by reduced live cover, substrate damage and restructured dominance, but only moderate changes in conventional diversity indices. Together, these results highlight the need for long-term monitoring and targeted restoration to track post-typhoon trajectories and sustain the resilience of nearshore reef ecosystems under a future of potentially more frequent and intense storms.