Salinity filtering and hydrological stage transitions drive the community reassembly of eukaryotes and particle-attached bacteria in Yuncheng Salt Lake

Extreme salt lakes represent natural model systems for investigating microbial community assembly under strong environmental filtering. However, cross-kingdom associations between eukaryotes and particle-attached bacteria, as well as the combined effects of salinity and hydrological phase transitions on community structure, remain poorly unresolved. We conducted a field survey in Yuncheng Salt Lake, comparing eukaryotic and particle-attached bacterial communities across high-salinity and low-salinity habitats during crystallization and stabilization phases. Salinity served as the dominant environmental filter and exerted stronger filtering effects on eukaryotes than on particle-attached bacteria, whereas phase effects were more pronounced under low-salinity, particularly for eukaryotes. Within deterministic processes, the relative contribution of variable selection for eukaryotes increased from 13.33% to 24.44%, while particle-attached bacteria became increasingly dominated by stochastic processes from crystallization to stabilization. The high-salinity network exhibited greater connectivity than the low-salinity network and was characterized by bacterial connectors as topologically central nodes. Functional potential of particle-attached bacteria was phase-dependent: crystallization was associated with carbon and energy metabolism pathways, whereas stabilization shifted toward heterotrophic carbon utilization and motility. In the high-salinity network, connector taxa were additionally associated with predicted functional potential related to attachment, nutrient acquisition, stress tolerance, and sulfur/methane metabolism. These findings elucidate the assembly and adaptive strategies of microbial communities in salt lakes, underscoring the critical roles of both salinity and hydrological phase in driving cross-kingdom community reorganization. This study provides novel insights into the ecology of extreme saline environments and the dynamics of aquatic microbial communities under environmental stress.