Fig. 3

Vertical organization of sediment microbial community. A Overview on sediment layering structure, including alpha diversity shifts along sediment depth and clustering analysis. Orange line stands for the richness of Chao1 (\(S\in <span class='reftype'><span class='reftype'><span class='reftype'>[1745, 2180]</span></span></span>\)) and blue line for Pielou’s evenness (\(E\in [0.76, 0.86]\)). UPGMA divided eleven spatial samples into two main clusters (R = 0.974, P = 0.002): the upper four layers and the lower seven layers, coinciding with the historical damming event. B Composition of dominant classes (the top 20) in different depth layers. C Principal coordinates analysis (PCoA) based on Bray–Curtis dissimilarities of OTUs illustrating continuous changes among bacterial communities grouped by depth. The size of 95% confidence circles shows within-group dissimilarities that represent seasonal fluctuation. D Identification of damming-sensitive phyla (DSP) and classes (DSC) in sediment based on random forest classification. The mean decrease in Gini value identifies the most reliable and relevant predictors (phyla/classes) to perform classifications. E Emergent stratification via bipartite network analysis with eleven seasonally merged samples. The node color shifting from yellow toward dark purple indicates a higher OTU-sample connection degree counting from 1 to 11. The grayscale of lines is indicative of the OTU richness in one sample