Abstract: Coral reefs constitute ecosystems with exceptional biodiversity, annually contributing substantial economic value to society. The escalation of sea surface temperatures (SST) has led to a marked increase in the frequency and severity of coral bleaching events, posing a grave threat to the survival of reef-building corals. To assess the ramifications of thermal discharge from power plants on coral communities, an ecological survey was conducted in the Honghai Bay area during autumn 2024. This study integrated numerical simulations of thermal discharge from the Taipingling Nuclear Power Plant and Haifeng Thermal power plant with degree heating week (DHW) analysis. The survey revealed that approximately six islands, situated at a considerable distance from the thermal discharge outlets, harbored a diverse range of coral species, including 13 species of stony corals (belonging to 5 families and 9 genera) and 7 species of soft corals (spanning 5 families and 7 genera). Coral coverage varied considerably across different sites, ranging from 0.30% to 36.38%. The bleaching risk prediction indicated that the 1°C seawater warming induced by thermal discharge in summer extended into the coral distribution area of Mangyu Island but did not impact other coral habitats. Conversely, in winter, the 2°C warming had no effect on any coral distribution zones. Under typical climatic conditions, the impact of thermal discharge on corals near Jixin Island remained within their normal tolerance thresholds. However, even in years with average water temperatures, thermal discharge elevated the DHW in Mangyu Island’s waters to over 4°C, thereby augmenting the risk of coral bleaching. Nonetheless, as SST gradually diminishes in autumn, coral bleaching may exhibit recovery. In summary, the influence of power plant thermal discharge on coral communities around the islands in Honghai Bay is limited and generally does not exert significant adverse effects under normal circumstances

Key words: Honghai Bay, coral bleaching, thermal effluent, degree heating week, power plant