Warm‐Water Regimes Influence Microbial Diversity and Ecological Functions in Subtropical Gulf

The marine ecosystem is a key biogeochemical engine driven by complex hydrodynamic processes and harbors significant microbial abundance and diversity. However, the influence of warm‐water dynamics on marine microbial community composition and ecological function remains unclear. In this study, we used high‐throughput sequencing to investigate the impact of water temperature on the composition and ecological processes of marine microbial communities in the Beibu Gulf. We found that temperature variation strongly influenced microbial community composition and ecological function in seawater. Proteobacteria were enriched in warm zones, whereas Cyanobacteria abundance decreased as the temperature increased. The transition zone exhibited the highest alpha diversity in summer and winter, suggesting favorable ecological niches under intermediate conditions. Functional analysis indicated that metabolic pathways dominated, particularly in the transition and warm zones in summer and winter. Random Forest analysis revealed Synechococcus sp. RCC307 had the highest relative abundance in the warm water zone in spring. Fulvimarina pelagi HTCC2506 was a summer warm‐water specialist, and Acinetobacter sp. PmeaMuc16 and Agrobacterium radiobacter were warm‐water indicator species in winter. Overall, these findings emphasize the critical role of thermal regimes in shaping bacterial communities in subtropical marine ecosystems and provide new insights into predicting microbial responses under ocean warming scenarios.