Succession and environmental response of sediment bacterial communities in the Liao River Estuary at the centenary scale.

Microbial community succession in turbulent estuarine environments is key to the understanding of microbial community development in estuaries. Centennial-scale sediment core samples collected from the Liao River Estuary (LRE) channel bar and side beaches were studied for geochemistry and 16S rRNA gene-based bacterial analyses. The results showed that bacterial community composition significantly differed between the sediments of the two sides of the channel bar, with Campilobacterota and Bacteroidota being dominant bacterial phyla in the tributary (T1, T2) and mainstream (MS1, MS2) sediment, respectively. Co-occurrence network of the bacterial community at the genus level showed more centralized and compacted topological features in tributary with weaker hydrodynamic, and the keystone taxas were Halioglobus, Luteolibacter, and Lutibacter in the bacterial community. The bacterial network structure had more edges and larger average degree in LRE sediments from the stage of the year 2016-2009 and the stage before 1939, which was possibly related to hydrodynamic conditions and nutrients. Stochastic processes (dispersal limitation) were the key factors driving bacterial community assembly in the LRE sediments. In addition, total organic carbon (TOC), total sulfur (TS), and grain size were the main deterministic factors affecting the change of bacterial community structure. Relative microbial abundance has the potential to indicate geologically historical environmental changes. This study provided a new perspective to reveal the succession and response of bacterial communities under frequent fluctuation environments.