Microbes Under Climate Refugia: Equable Subcommunity Rank Dynamics in Large-River Deltaic Estuaries.

Microorganisms, similar to macroorganisms, can be sheltered by climate refugia-a property overlooked due to their speciose nature. Using the latent Dirichlet allocation model to categorize microbial communities into ecologically distinct subcommunities, we conducted a 2-year survey of large-river deltaic estuaries (LDEs), recognized as refugial hotspots, and established rank hierarchies with the continuous time dynamic model to monitor temporal changes. We found that, consistent with macroecology, LDEs harbor distinct microbial community structures, with the abundance distribution of subcommunities exhibiting resilience against environmental perturbations, persisting on an annual cycle. Specifically, subcommunity rank abundance curves show frequent evenness fluctuations, whereas rank-order shifts-though less dynamic-exert stronger carryover effects on subsequent rank dynamics when occurring. Our results suggest that the microbial subcommunity rank structure in LDEs is persistent, aligning with classic patterns of species abundance distributions. This study emphasizes that, despite differences in their roles, the stable functioning of microbial rank systems is also fundamental to the refugial capacity of ecosystems and should be given equal importance.