Bacterial community plays a vital role in the open-oceanic aquaculture ecosystem, and its stability is crucial for maintaining the health of mariculture fish. However, there are no reported studies on microbial communities in the culture environment of marine fish cages. In this study, bacterial community composition and diversity of seawater and sediment habitats from 5 large yellow croaker cage farms were first investigated by 16S rRNA-based high-throughput sequencing. The composition of bacterial communities was visualized at the phylum and genus levels. Meanwhile, biological and ecological functions were also predicted. The bacterial diversity observed at 3 inshore sampling sites was higher in seawater groups than that in sediment groups. The alpha diversity indices were influenced by the geographic location, especially the inshore site Yueqing (YQ), showing higher values than other sampling sites. The pathogenic bacteria were prevalent in the aquaculture environments, and probiotics showed a relatively low proportion by comparing the potential pathogens. Our study provides baseline data on bacterial communities and diversity in the open-oceanic environments of cage-culture large yellow croaker.

A novel strain capable of fully utilizing p-nitrophenol (PNP) as the sole carbon source under high-salinity conditions was isolated from the sediments of wastewater discharged from an aquaculture company. The identification of the strain as Bordetella sp. was confirmed by analyzing its morphological, physiological, and biochemical traits in conjunction with its 16S rDNA sequence. Furthermore, pantothenic acid, serving as a carbon source for co-metabolites, could significantly enhance the biodegradation process of the tricarboxylic acid (TCA) cycle. Under the optimal growth conditions at a temperature of 30 °C, pH of 8.0, aeration of 0.32 m³·(m³·min)⁻¹ and salinity of 3% (NaCl, w/v), the degradation rate of 350 mg·L⁻¹ PNP increased from 60.8% to 85.9% within 72 h after adding 30 mg·L⁻¹ of pantothenic acid to a 12-liter bioreactor. The intermediate products from the degradation process, analyzed via GC/MS, were determined to be hydroquinone, which suggests that the degradation pathway of the bacterium for PNP involves the breakdown of hydroquinone. Benefits have been derived from the microorganism’s tolerance to high salinity and high PNP concentrations, coupled with its superior PNP degradation performance, offering new insights and a research basis for the efficient biological treatment of high-salinity PNP wastewater.