Fig. 7
A Hypothesized mechanism of microbial community stratification. The damming in 1963 accelerated lake eutrophication and sedimentation rate, altering sediment nutrient composition and increasing energy input. This changed the metabolic type, order, intensity, and chemotaxis of sediment microorganisms, shortening the natural sediment profile transition process. On the other hand, accelerated sedimentation rate, enhanced sediment biodegradation rate, and gaseous metabolites jointly imposed the interstitial space, which further affected the negative dispersal of sediment microbes. As a result, the relative proportion of dispersal and selection shifted and resulted in community stratification. OM organic matters. B Partial least squares path modeling (PLS-PM) quantitatively depicting the cause-effect mechanisms underlying the emergent stochasticity at the sharp transition zone revealed by the time-merged data. Red and blue arrows represent significant (* P < 0.05 and ** P < 0.01) positive and negative paths, respectively; paths with no significance (ns, P > 0.05) are labeled in gray. The arrow width reflects the path coefficient value (the number near the path). The goodness-of-fit (GoF) shows a good prediction power of the model that is of 71%. Specific assessment indexes of both measurements (Cronbach’s alpha, loadings, etc.) and structural models (R2, redundancy, etc.) are listed in Table S13