From conservative to opportunistic: Adaptive shifts in urban aquatic microbial communities driven by...

Accurate environmental assessment and monitoring of urban aquatic ecosystems requires a deep understanding of microbial functional responses to environmental heterogeneity and their role in maintaining ecosystem resilience. To evaluate the influence of environmental gradients on microbial communities, paired water-sediment samples from urban waters in Zhuhai were analyzed (covering 80 prokaryotic communities and 40 sediment bacterial communities). Environmental filtering dominated the microbial community assembly, with significant compositional differences between the planktonic and sediment bacterial communities (p < 0.01). Phosphorus acquisition strategies (alkaline phosphatase-driven) and primary productivity (chlorophyll a-defined) were key factors shaping microbial responses. Notably, microbial carbon metabolism (indicated by total organic carbon, TOC) was tightly coupled with primary productivity (Chl-a, r = 0.65), suggesting a synergistic shift in carbon fixation and phosphorus scavenging strategies along the trophic gradient. Metabolic partitioning within the water column was identified as a core mechanism of environmental adaptation. Trophic gradients guide a strategic trade-off between carbon assimilation and phosphorus acquisition and shape microbial resource allocation plasticity and functional adaptability, in which cyanobacteria play a key role in maintaining community stability. In particular, the microbial communities exhibited a significant functional shift from energy conservation under oligo-mesotrophic conditions to opportunistic resource exploitation in eutrophic/hypereutrophic states. These findings refine our understanding of microbial feedback mechanisms in vulnerable urban aquatic ecosystems.