Stronger Adaptability of Eukaryotic Communities than Prokaryotes in Seawater across an Extensive Salinity Gradient

Researching microbial ecology in extreme environments is crucial for advancing the basic ecological theory and exploring their potential applications in biotechnology. The salt drying system provides an accessible but harsh environment that covers a maximum salinity gradient. In this study, we conducted a comparative analysis of the salinity adaptation and assembly mechanisms of prokaryotic and eukaryotic communities in several salt drying tanks using high-throughput amplicon sequencing and multiple ecological analyses. The beta diversity analysis, based on the unweighted and weighted Unifrac distances, revealed significant variations in microbial community compositions along the salinity gradient, with stronger influences on prokaryotes. Species turnover was the primary mechanism driving the beta diversity patterns, which was regulated by the local species pool. Further comparisons of multiple niche and adaptation indices indicated that seawater eukaryotic communities exhibited stronger salinity adaptability than prokaryotes. In addition, the beta deviation index suggested that heterogeneous processes shaped the microbial communities. Moreover, the neutral community model showed higher dispersal ability of eukaryotes than prokaryotes. Also, they were stochastic and deterministic dominant communities along the salinity gradient, respectively. Overall, our findings contributed significantly to understanding the microbial ecology in relation to salinity gradients.