In aquatic ecosystems, free-living (FL) bacteria are typically DOM-decomposers and particle-attached (PA) bacteria are POM-decomposers. Taxonomical and functional diversity of these bacteria within marine carbon cycle has been examined using DNA-based approaches, which, however, overlooked physiological states (active, dormant, and dead) of the source cells, leading to potential uncertainty of their activities, persistence, and driving factors of their community assembly processes across time and space. In this study, we investigated the physiology-informed diversity of FL and PA bacteria in coastal waters of northern and southern China using the triple-metabarcoding approach. We found that dormant bacteria accounted for 9.4% of total ASVs and 6.4% of sequences in the PA rDNA pool, proportions notably higher than those in the FL pool (5.9% and 3.7%, respectively). Although sequences derived from dead cells (relic DNA) accounted for an average of only 13.8% of the rDNA pool across size fractions, they disproportionately comprised over 50% of the total ASV richness. Futhermore, in northern coastal waters, the richness of both dormant copiotrophs and oligotrophs was consistently higher within particulate microenvironments compared to the ambient seawater. Finally, environmental filtering strongly influenced active bacterial assemblages, with temperature, salinity, and spatial variables explaining 42.45% of the variation in PA assemblages and up to 73.42% in FL assemblages when combined with water depth and chl-a. In contrast, environmental factors explained less than 20% of the variation in dormant and dead bacterial assemblages. These findings demonstrate that resolving microbial physiological states is essential for accurately deciphering their ecological roles and community assembly mechanisms in the coastal marine ecosystems.
 

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