Fig. 6

Partial least squares path modeling (PLS-PM) showing path coefficients (direct effects) of factor categories on spatial variability in assembly mechanisms of total bacterial community and seven taxonomic groups (expressed by the ratio of the relative abundance of non-neutrally ZOTUs to that of neutrally distributed ones). The overall prediction performance of the models was assessed using goodness of fit (GoF) statistic. Blue and red lines present significant positive and negative effects, respectively (only significant effects were shown, P < 0.01), and the thickness of lines indicated direct effect strength (as data on the lines). Basic: basic abiotic constraints including pH, and DO; Inorganic: inorganic resources including salinity, DIN (sum of NO₃, NO₂, and NH₄), and PO₄; Organic: organic resources including SP, COD, and oil; Chl-a: chlorophyll-a; Diversity: alpha diversity indices including phylogenetic diversity, ZOTU richness, and Shannon–Wiener index; Niche: niche breadth of bacteria at the community level; Interaction: potential bacterial interactions inferred by the features of microbial associations including cohesion ratio (|negative cohesion/positive cohesion|), modularity, and average degree