Distinct co-succession of dissolved organic matter and bacterial generalists and specialists in inflow rivers of Baiyangdian Lake

Abstract

Dissolved organic matter (DOM) significantly affects the stability of river microorganisms, but the seasonal regulatory mechanisms of generalists and specialists remain unclear. Through spectral measurement and high-throughput sequencing techniques, the structural, network, and evolutionary characteristics of generalists and specialists in Baiyangdian lake inflow rivers from 2021 to 2023 were analyzed, and the influences of environmental factors and DOM on their dynamics were quantified. Parallel factor analysis (PARAFAC) identified two protein-like components (C1+C2) and one humus-like component (C3). Among them, the protein-like components were significantly higher in urban reclaimed water (URW) than in non-urban reclaimed water (NRW), while the humus-like component was higher in summer than in winter (P < 0.001). The relative concentration of DOM was higher in summer, showing overall low humification and strong autochthonous characteristics (FI > 1.8, HIX <4). Actinobacteriota and Proteobacteria were the main components of generalists and specialists. Species replacement had a much greater impact on β-diversity than richness differences. The network structure of winter and NRW exhibited more complex topological properties, and the stability of generalist networks was lower than that of specialists. Stochastic processes dominated the community assembly process (63.73 %–93.94 %), with generalists in summer being more influenced by stochastic processes, while the opposite was true in winter. The BiSSE model indicated that specialists exhibited higher diversification potential than generalists. Path analysis showed that in summer URW, diversity and protein-like components had the greatest impact on the network stability of generalists and specialists, respectively. In NRW, humus-like component had the greatest impact on the network stability of specialists. This study clarified the mechanism by which the seasonal characteristics of DOM drive the ecological strategy differentiation of generalists and specialists in rivers, providing a theoretical basis for watershed ecological management.