963 / 2024-09-19 22:21:40

Effects of different types of wastewater discharge on microbial communities in coastal sediments

coastal microbial community,wastewater discharge,assembly mechanisms,biogeochemical functions,microcosm experiment

Wastewater treatment plants (WWTPs) impact the coastal environment by introducing pollutants. Despite regulations, these pollutants disturb water bodies. The ecological impacts and risks of various discharges need further study, particularly on their types and intensities. Microbial communities in coastal sediments are crucial for ecosystem stability and biogeochemical cycles. WWTP effluent alters microbial structure and function, leading to lower network complexity, reduced diversity, and more pollution-tolerant species. Microorganisms' environmental sensitivity makes them pollution indicators, though past research focused on single factors or species with in-situ monitoring. In this study, we conducted shock-culture experiments to understand the extent of damage to the coastal ecosystem caused by pollutants, and samples of sediment from the pollution-receiving area (SY) and the offshore area (HB) of Hangzhou Bay were collected for a wastewater discharge impact microcosm experiment. The diversity and abundance of microbial communities in the HB region were lower than those in the SY region, and significant structural differences existed between the two regions. The microbial community in the HB area responded more strongly to high pollution concentrations, whereas the SY region exhibited greater adaptability to pollution stress. Comparatively, the species composition in the SY region remained more stable. There were minor differences in the functional composition of sediment microbes between HB and SY, with domestic wastewater impacts suppressing microbial function in the HB region. Denitrification was the dominant process, and the relative abundance of nitrification functional genes was significantly higher in all SY samples than all HB samples, indicating that effluent discharge significantly inhibits the nitrogen-fixing ability of microbial communities. Sulfate reduction was the primary process, and wastewater discharge significantly inhibited the sulfate reduction process in microbial communities in both HB and SY sediments while promoting the sulfite reduction process in HB sediments. Rising wastewater concentration increased stochastic processes in HB's microbial community assembly but decreased them in SY. Wastewater discharge also reduced microbial network complexity and stability in HB and changed keystone taxa in both regions. More frequent future human activities will expedite microbial responses to pollution and weaken coastal ecosystem functions. Hence, monitoring coastal microbial communities is essential.