Exploring the mechanism of a novel recirculating aquaculture system based on water qualities and bacterial communities

A novel recirculating aquaculture system (RAS) with ecological ponds is introduced to alleviate the environmental problems causing by aquaculture wastewater. However, its mechanism is still unclear about how the ecological ponds decompose the inorganic matters. Therefore, we designed a 7-week in-site experiment to explore the dynamic of water quality and the shift of bacterial communities during the initial stage of the pond ecosystem. The results showed: (1) The system was able to maintain the DO concentration at 7 ~ 9 mg/L, but the inorganic nitrogen and phosphorus concentration (except for ammonia nitrogen) in the aquaculture water increased dramatically with increased EC values, indicating that the decomposition capacity of the ponds is insufficient; (2) A higher abundance and diversity of the bacterial community in the sediment were observed than that in water samples, and the dominant phyla in the aquaculture water were Proteobacteria (41.14%), Bacteroidetes (37.04%), Cyanobacteria (10.26%), Verrucomicrobia (5.32%) and Actinobacteria (4.03%), while Proteobacteria (43.43%), Bacteroidetes (16.13%), Chloroflexi (10.01%), Actinobacteria (5.70%) and Cyanobacteria (4.70%) were predominant in the sediment; (3) The influencing physicochemical parameters on bacterial communities in the aquaculture water were DO and ammonia nitrogen concentration on week 1 ~ 3, which on week 4 ~ 6 and week 7 were water temperature, pH and TOC, respectively. Our studies assessed the RAS with ecological ponds for the first time based on water quality and bacterial community, which summarized its advantages and disadvantages on effluent treatment and provided valuable suggestions on the improvement of RAS with ecological ponds.