Salinity and seasonality shaping free-living and particle-associated bacterioplankton community assembly in lakeshores of the northeastern Qinghai-Tibet Plateau

Microorganisms in lakeshore zones are essential for pollution interception and biodiversity maintenance. However, the biogeographic patterns of bacterioplankton communities in lakeshore zones and the mechanisms that driving them are poorly understood. We analyzed the 16 S rRNA gene sequences of particle-associated (PA) and free-living (FL) bacterioplankton communities in the lakeshore zones of 14 alpine lakes in two seasons on Qinghai-Tibet Plateau to investigate the bacterial diversity, composition and assembly processes. Our results revealed that PA and FL bacterioplankton communities were driven by both seasonality and salinity in the lakeshores on Qinghai-Tibet Plateau. Compared to FL bacterioplankton, PA bacterioplankton communities were more susceptible to seasonality than spatial salinity. FL bacterioplankton communities were more salinity constrained than the PA counterpart. Besides, the Stegen null model analyses have validated a quantitative bias on stochastic processes at different spatial scales. At a regional scale, stochasticity was the predominant assembly process in both PA and FL bacterioplankton. While at a subregional scale, dispersal limitation was the main contributor of stochastic processes for PA bacterioplankton in summer and heterogeneous selection was the dominant deterministic processes in winter, whereas the community assembly of FL bacterioplankton was more stochastic processes (i.e., dispersal limitation) dominated in the freshwater type but deterministic process (i.e., heterogeneous selection) increased with increasing salinity. Our study provides new insights into both significant spatiotemporal patterns and distinct assembly processes of PA and FL bacterioplankton in alpine lakeshores on the northeastern Qinghai-Tibet Plateau.