Stochastic process shapes the spatiotemporal patterns of main eukaryotic communities in a subtropical estuary

A fundamental question in ecology is what processes determine the spatiotemporal distribution of species. However, our current understanding of the eukaryotic biodiversity patterns and their underlying mechanisms in the estuaries is limited. This study used eDNA metabarcoding data and multivariate ecological and statistical analysis to compare the spatiotemporal patterns, co-occurrence patterns and assembly processes of eukaryotic communities in the Pearl River Estuary during the wet and dry seasons. The results indicate a significant seasonal difference in the composition, diversity distribution pattern and biological interaction, possibly being attributed to ecological drift induced by strong hydrodynamic exchange with the Pearl River runoff and the species traits. Temperature and salinity were the major factors mediating the balance of assembly processes, and their gradient change are insufficient to transform community structure into a deterministic process. Species asynchrony may stabilize community fluctuations driven by seasonal turnover, while niche differentiation maintains the stability of community structure itself. This study highlights our understanding of the spatiotemporal dynamics of different eukaryotic taxa under varying hydrological conditions, thereby contributing to a better understanding of the spatiotemporal patterns, assembly processes, and stability mechanisms in estuarine eukaryotic communities.