Cross-domain microbial differences across freshwater and marine habitats in a tropical delta
摘要
Microbial communities are central to aquatic ecosystem functioning, yet integrated cross-domain comparisons of prokaryotic and microeukaryotic microbiomes remain underexplored in tropical regions, particularly in Bangladesh. Here, we investigated habitat-associated differences in microbial community structure across freshwater and marine ecosystems of the Bangladesh tropical delta using 16S and 18S rRNA gene amplicon sequencing and assessed inferred functional potential for prokaryotic communities. Six freshwater and ten seawater samples were analyzed, comprising eight newly generated datasets (six freshwater and two seawater) and eight previously published seawater datasets. Prokaryotic communities exhibited significantly higher alpha diversity in freshwater, whereas microeukaryotic diversity showed no significant habitat-associated differences after correction, despite a weak freshwater enrichment trend. Beta diversity revealed clear compositional separation between habitats for both domains, with prokaryotes exhibiting centroid shifts and microeukaryotes showing greater within-group dispersion. Taxonomic profiles showed seawater dominance by Gammaproteobacteria and Alphaproteobacteria, whereas freshwater communities were more evenly distributed across Bacteroidota, Actinomycetota, and Verrucomicrobiota. Microeukaryotic assemblages also displayed pronounced habitat-associated restructuring. Functional inference of prokaryotic communities indicated conservation of core pathways across habitats despite taxonomic turnover. Exploratory cross-domain correlation analysis identified mixed positive and negative associations, although none remained significant after multiple-testing correction. Collectively, these findings reveal consistent habitat-associated microbial differentiation across tropical freshwater and marine ecosystems and provide a comparative baseline for understanding cross-domain microbial biogeography in climate-sensitive aquatic environments.