Historical exposure to wastewater disposal reinforces the stability of sediment bacterial community in response to future disturbance

Given that long-term treated wastewater discharge may alter the microbial community of the recipient coast, it is important to evaluate whether and how the community's stability is impacted. We constructed microcosms using coastal sediments with (near-coast) and without (far-coast) a wastewater disposal history and compared the communities’ responses to p-chloroaniline (PCAN, a typical organic pollutant) in low (10 mg/L) and high (100 mg/L) concentrations. Compared to the far-coast community, the near-coast community drove faster PCAN attenuation and nitrate generation. More significant negative correlations were observed between the alpha-diversity indices and PCAN concentrations in the far-coast communities than the near-coast ones. The community turnover rate, represented by the slopes of the time–decay curves, was slower for the near-coast community (−0.187) than that for the far-coast community (−0.233), but only when the PCAN was added in low concentration. Our study revealed that the long-term wastewater disposal may cause the sediment bacterial community to be less sensitive and more stable in response to a future disturbance, demonstrating a significant historical effect of environmental context on the coastal microbial community's stability.