In the rapid development of marine aquaculture, the water quality of aquatic environments is regarded as a main limiting factor. Therefore, it is necessary to assess the water quality and environmental conditions in marine aquaculture areas and find out the main influencing factors regarding damage to the water quality environment. In the present research, pond aquaculture and cage aquaculture areas were sampled in May, August and November in 2018. Nine water quality indicators were detected, including pH, temperature, salinity, dissolved oxygen, molybdate-reactive phosphorus, chemical oxygen demand, chlorophyll a, inorganic nitrogen and antibiotic resistance genes (ARGs). Principal component analysis (PCA) was used to analyze the water quality conditions, spatial–temporal changes, and the driving factors in pond and cage aquaculture areas. The results showed that three main components were extracted from the pond aquaculture area, which explained 66.82% of the results, the most relevant factors are salinity, dissolved oxygen and ARGs. For the cage aquaculture area, three main components were extracted which can account for 72.99% of the results, the most relevant factors are chlorophyll a, salinity and dissolved oxygen. The comprehensive scores of the principal components indicated that the heaviest polluted months in pond and aquaculture areas were August and November, respectively. The water quality of the pond aquaculture area is mainly limited by the volume of the pond, while aquaculture activities and seasonality are the main factors for cage aquaculture. ARGs in cage culture areas showed more variety and frequency compared with pond culture areas, which indicated that terrestrial input might be one of the sources for ARGs occurrence. The results would be helpful for the relevant authorities to select water quality monitoring parameters in marine aquaculture areas.

Ultraviolet disinfection is an important method for controlling the large-scale outbreaks of diseases in aquaculture. As a novel and promising light source, ultraviolet light-emitting diode (UV-LED) has the advantages of safety, high efficiency and no environmental pollution risks. However, it remains unclear whether UV-LEDs can replace traditional UV light sources for aquaculture water treatment processes. Present study aimed to investigate the efficacy of UVC-LEDs (265 nm) on pathogenic bacteria, specifically Aeromonas salmonicida and Escherichia coli. The effects of UVC-LED dose, light conditions, and temperature on bacterial reactivation were also investigated. The results showed that exposure to UVC-LED effectively inactivated both types of bacteria. To achieve 4.5-log inactivation of A. salmonicida and E. coli, 24 mJ/cm² and 28 mJ/cm² UVC-LED irradiation were required, and the inactivation rate increased with increasing UVC-LED fluence. Both A. salmonicida and E. coli were revived after UVC-LED disinfection, and photoreactivation was significantly higher than dark reactivation. Bacterial reactivation rate due to high-dose UVC-LED treatment was significantly lower than that of low-dose. After 72 h of reactivation, photoreactivation and dark reactivation rates were 1 ± 0.4% and 2.2 ± 0.2%for A. salmonicida, and 0.02% and 0% for E. coli, respectively. Besides, the photoreactivation rates for the two bacteria exhibited different correlations with temperature. The highest photoreactivation rate for A. salmonicida was 68.7 ± 4% at 20°C, while the highest photoreactivation rate for E. coli was 53.98 ± 2.9% at 15°C for 48 h. This study reveals the rapid and efficient inactivation of bacteria by UVC-LED, and elucidates the mechanism and influencing factors for inactivation and reactivation by UVC-LED. The study also highlights that adequate UVC-LED irradiation and avoidance of visible light after UVC-LED disinfection can effectively inhibit bacterial reactivation. Our findings form a reference for the design and operation of UV disinfection in aquaculture.

As an invasive species, Pomacea canaliculata exerts significant adverse effects on aquatic ecosystems. It can infect native freshwater snails, such as Cipangopaludina chinensis, by secreting pathogens, leading to increased stress and mortality. Gut microbiota play a crucial role in the survival and adaptation of gastropods, significantly influencing their health and resistance to environmental stressors. By comparing the gut microbiota composition and metabolic profiles between resistant (RE) and sensitive (SE) populations of C. chinensis, this study aims to elucidate the role of the gut microbiota in enhancing the survival of C. chinensis under the invasion pressure from P. canaliculata. And the mechanisms were further explored through gut microbiota transplantation, horizontal and vertical transmission experiments, and field studies. Our findings reveal that RE individuals exhibit greater gut microbiota diversity and a higher abundance of core microbiota, including Psychrobacter, Comamonas, and Pseudomonas, which are correlated with enhanced host survival in the presence of pathogen infections. Analysis of metabolite composition demonstrate that antibiotics and immunological enhancers are the main metabolites, which significantly enhance the host’s resistance to pathogen infections. Notably, these core gut microbiota can be transmitted both horizontally and vertically, allowing C. chinensis populations to acquire resistance to the invasion of P. canaliculata. The SE group is enriched in pathogens, such as Mycoplasma. Following the transplantation of RE gut microbiota, SE individuals exhibited improved survival rates and core microbiota abundance. The vital role of core microbiota in maintaining the survival rate of C. chinensis was further confirmed in the field studies. This study highlights the crucial interactions between the gut microbiota and the host's adaptability, offering valuable insights for native species in response of invasive species pressure.