Ocean currents and environmental gradients shape prokaryotic community structure and function in the South China Sea

Microorganisms, especially prokaryotes, are fundamental in sustaining marine ecosystems through nutrient cycling and organic matter decomposition. However, understanding what shapes their diversity and distribution remains challenging. Our study highlights the significant role ocean currents and environmental conditions play in influencing prokaryotic communities in the South China Sea-a critical marine environment due to its dynamic currents and ecological complexity. We found that currents facilitate microbial dispersal, shaping community composition over vast areas, while temperature gradients act as key selective pressures, determining which species thrive. Additionally, we reveal that both predictable environmental selection and random ecological drift significantly contribute to community structuring. By identifying keystone microbes and biomarkers sensitive to environmental change, our work offers essential insights into marine microbial ecology. These findings are crucial for predicting how microbial communities, and thus ocean health and productivity, respond to ongoing environmental changes.