Construction of an electro-assisted microalgal-bacterial consortium system under gradient salinity acclimation: dynamic effects of microalgae on microbial communities

To achieve efficient nitrogen removal from mariculture wastewater, this study developed a microalgal-bacterial consortium (MBC) system augmented through salinity acclimation and weak electric field stimulation. Compared to the electro-assisted activated sludge (AS) system, the electro-assisted MBC system exhibited higher average removal efficiencies for TN by 11.83%, respectively. Characterization of sludge-biofilm hybrid phases indicated that microalgal integration enhanced the structural complexity and stability of both components. High-throughput sequencing revealed significantly greater microbial diversity in the MBC system compared to the AS system, with a 13.7% increase in cooperative interactions and a 5.76% rise in the proportion of specialist taxa. The introduction of electro-assistance reduced deterministic processes in the AS system but increased them in the MBC system, indicating that microalgae enhanced deterministic selection to stabilize the core microbial community. Furthermore, microalgae enriched keystone taxa, improving system-wide stability and resource utilization capacity. These results advance our understanding of bacterial ecological dynamics under microalgal influence and establish a foundation for targeted community management strategies in MBC systems.