To investigate the removal efficiency of inorganic nitrogen and phosphorus from mariculture wastewater by the deep-sea fish-derived strain Alloalcanivorax xenomutans AXMZ1 under different culture conditions, we perfomed batch experiments at salinities of 5‰, 10‰, 25‰, and 40‰, pH levels of 4, 6, 8, and 10, and temperatures of 10, 20, 30, and 40 °C, and periodically measured pllutant concentrations. The results showed that strain AXMZ1 grew well across all tested ranges (Salinity 5‰–40‰, pH 4–10, temperature 10–40 °C), demonstrating broad environmental adaptability. The strain exhibited remarkable removal efficiencies for phosphate, nitrite nitrogen, and nitrate nitrogen. At 20°C, phosphate removal remained stable at 93.5%–96.5%, nitrite nitrogen removal exceeded 99.6%, nitrate nitrogen removal ranged from 95.8% to 97.3%, and total inorganic nitrogen removal reached 77.0%–87.4%. At salinity 40‰, nitrite and nitrate nitrogen removal rates reached 99.7% and 97.9%, respectively. At pH 10, the maximum total inorganic nitrogen removal of 98.1% was achieved. Although ammonia nitrogen removal was relatively lower (Maximum 69.0%), the strain's capacity for nitrite and nitrate nitrogen removal substantially surpassed that of most previously reported marine denitrifying bacteria. In conclusion, strain AXMZ1 combines high-efficiency nitrogen and phosphorus removal capabilities with excellent environmental adaptability, showing particular advantages under moderate-to-high salinity (25‰–40‰), slightly alkaline (pH 8–10), and low-temperature (20 °C), indicating promising potential for the bioremediation of mariculture wastewater and the restoration of marine nitrogen and phosphorus pollution.

To investigate the effects of exogenous functional microorganisms on microbial community structure, carbon metabolism characteristics, and organic carbon content in aquaculture water, we designed a blank control group, a feed control group, and three bacterial supplementation groups treated with Bacillus licheniformis, Lactobacillus plantarum, and Rhodopseudomonas palustris, respectively. We measured the total organic carbon (TOC), dissolved organic carbon (DOC), total bacterial count, microbial community structure, and carbon metabolism function to analyze their dynamic changes. The results showed that the addition of three beneficial bacteria significantly enhanced microbial metabolic activity and community diversity. On Day 7, the Shannon index in the bacterial supplementation groups reached 3.17–3.18, which was significantly higher than that in the control groups (p<0.05). The exogenous probiotics exerted limited influence on overall bacterial abundance and community succession. In the later stages, Pseudomonadaceae and Rhodobacteraceae became the dominant families. The degradation rates of TOC and DOC in the bacterial supplementation groups reached 59.0%–59.5% and 57.1%–57.7%, respectively, which were significantly higher than those in the blank control group (p<0.05). Among the three strains, R. palustris exhibited the strongest carbon source utilization capacity, B. licheniformis showed a clear advantage in degrading complex organic carbon, and L. plantarum exerted a mild and stable effect. This study indicates that the addition of Bacillus, photosynthetic bacteria, and lactic acid bacteria to aquaculture water can improve microbial community diversity and metabolic activity and accelerate organic carbon degradation.