Roles of physical disturbance and biome properties in shaping microbial communities within Indian Ocean eddies.

Oceanic eddies create localized upwelling and downwelling systems and are thought to alter microbial communities through environmental selection and dispersal. Though how these eddy-driven mechanisms contribute to microbial outcomes within a broader environmental context is unknown. We proposed that (1) eddies are a large disturbance that exert a significant influence on bacterial community and functional diversity as well as taxonomic and functional composition and (2) that the combined processes of environmental selection and dispersal determine bacterial outcomes within eddies. To address these hypotheses, we integrated bacterial genomics and environmental conditions from 26 eddies across the Indian Ocean. We observed that the biome had a strong, primary influence in shaping all aspects of bacterial communities with eddies playing a weak, secondary role. Additionally, there was minimal evidence of an effect of environmental selection or dispersal in shaping bacterial community diversity. Our observations highlight the variability in bacterial responses within and between eddy types and emphasize the importance of understanding eddy characteristics and broader biome attributes in interpreting bacterial responses.