organic carbon, predator, resistance and resilience, community stability, urban river, aquatic microbial community

With global rapid urbanization, anthropogenic activities alter aquatic ecosystems in urban rivers through inputs of dissolved organic carbon (DOC) and nutrients. Microorganisms play crucial roles in global biogeochemical element cycles, providing functions to sustain microbial ecology stability. Consequently , DOC (bottom-up control) and microbial predation (top-down control) may synergistically drive the competition and evolution of aquatic microbial communities, and their resistance and resilience, awaiting experimental evidences. In this study, laboratory sediment-water column experiments were employed to mimic the organic carbon-driven water blackening and odorization process in urban rivers and to elucidate impacts of DOC on the microbial ecology stability. Results showed that low DOC (25-75 mg/L TOC) and high DOC (100-150 mg/L TOC) contamination changed the aquatic microbial community assemblies in different patterns: (1) the low DOC enriched K-selection microorganisms (e.g., bacteria and predators) with low biomass and low resilience, as well as low resilience against microbial ecology stability; (2) the high DOC was associated with r-selection microorganisms with high biomass and improved resilience, together with low resistance detrimental to microbial ecology stability. Overall, this study provided new insights into impacts of DOC on aquatic microbial ecology stability, which may guide sustainable urban river management.