Evidences of the sources of suspended sediments and ecological processes in the Yellow River Basin

Terrestrial originated suspended sediments from the Yellow River are crucial to understand the sources of the suspended sediment and ecological processes in estuary. This study integrated physicochemical indices, stable isotopes and microbial communities to trace the origin of the suspended sediment, and investigated the importance of ecological processes in community assembly via the null model and neutral community model. Global data revealed that the dissolved and particle ratios of carbon and nitrogen obviously decreased from the headstream to the estuary. A significant positive correlation was detected between δ¹⁵N and δ¹³C from Henan Province to offshore. Notable differences in bacterial community composition were found between Henan Province and offshore in dry season, whereas nearly no remarkable changes were detected throughout the entire YR basin in wet season. Multiple lines of evidence from physicochemical analysis, stable isotopic and genetic tracing revealed the possibility that the terrestrially- derived suspended sediments in the lower reaches contributed the most carbon and nitrogen to the suspended sediment in the estuary. Dispersal limitations for stochastic processes had the greatest relative importance in the community assembly of the two seasons. A greater degree of homogeneous selection for deterministic processes was exhibited in dry but not wet season. Proteobacteria had a remarkable correlation with salinity and conductivity in both dry and wet seasons, while Elusimicrobiota was more strongly related to NO₃-N in dry than that in wet season. Therefore, this study elucidates the source of suspended sediment in estuaries and highlights the ecological processes involved in altering the microbial community composition in Yellow River basin.