Dynamics of fungi and the connection with bacteria in removing nutrients from mariculture wastewater in the integrated bioremediation systems

The bacterial community has received major attention in the research on the treatment of mariculture wastewater, while the fungal community has rarely been mentioned. To fill gap, an integrated bioremediation system (IBS) was built and the fungal community was identified by high-throughput sequencing in this study. Dimension reduction analysis, network analysis, community construction analysis were used to reveal the dynamic changes, interactions, and construction process of fungal communities in each treatment unit. The results showed that after a whole set of systematic and continuous treatments, the nutrient content in mariculture wastewater reached the lowest level. The fungal community was closely related to total nitrogen (TN), total phosphorus (TP), NO₃⁻-N, and NH₄⁺-N. In biofilm and shellfish units, Ascomycota was dominant, while in macroalgae units, Chytridiomycota was dominant. The community β-diversity of brush, ceramsite, and shellfish units showed similar trends in three time periods. In addition, some fungi showed a significant positive correlation with denitrifying bacteria, and this symbiotic relationship needs to be further studied. Finally, in the process of community construction, IBS was dominated by the stochastic process. This study aimed to more comprehensively interpret the dynamic changes of the microbial community in the mariculture wastewater treatment system and provided the theoretical reference for better understanding its potential mechanism and optimizing its process in the future.