In situ filtration reveals salinity-driven dynamics of prokaryotic and eukaryotic communities in the Yinggehai solar saltern.

Hypersaline environments harbor unique microbial communities adapted to extreme conditions. Here, we investigated microbial communities across a salinity gradient in the Yinggehai Saltern, southern China’s largest saltern, using 24 in situ filtration samples. The results revealed clear taxonomic shifts with increasing salinity. Bacterial diversity peaked in the primary evaporation ponds (PE), reflecting coexistence of marine and halotolerant taxa at moderate salinity, whereas eukaryotic diversity steadily decreased. Alphaproteobacteria declined along the gradient, while several halotolerant taxa (Puniceicoccus, Thiohalocapsa, Wenzhouxiangella) and potentially novel extremophiles became abundant in high-salinity environments. Chlorellales X exhibited remarkable halotolerance, while Cryptophyta and Dinoflagellata decreased with salinity. Network analysis revealed that salinity constrains ecological interactions: PE exhibited predominantly positive co-occurrence associations (69.55% positive), while higher salinity environments showed increased negative co-occurrence patterns (> 43% negative associations). Random Forest modeling confirmed salinity as the primary driver of the community composition. Our comprehensive analysis of prokaryotic-eukaryotic communities and their interactions provides novel insights into microbial adaptation and ecological dynamics in extreme environments.