Enhancement of total ammonia and nitrite removal, growth, and vibrio tolerance in whiteleg shrimp (Penaeus vannamei) by Paracoccus marcusii ND07 administration in rearing water

Abstract

Managing nitrogenous pollutants is a critical issue in the field of aquaculture production. A heterotrophic bacterial strain, Paracoccus marcusii ND07, possessing the capability to remove both total ammonia nitrogen (TAN) and nitrite, was isolated from shrimp culture water. The bacterial isolate was found to be non-toxic and susceptible to a broad spectrum of antibiotics. The impact of ND07 bacterial suspensions on the aquaculture of Penaeus vannamei was investigated. Over an eight-week period, shrimp rearing water was treated with three different concentrations of ND07: 10⁴ (T1), 10⁵ (T2), and 10⁶ (T3) CFU/mL, along with a control group devoid of ND07. The introduction of ND07 in all treatment groups resulted in a significant decrease in the concentrations of TAN and nitrite, along with a reduction in the counts of Vibrio spp. in the culture water. When compared to the control, the treated groups exhibited significantly enhanced growth performances, as evidenced by the final weight, weight gain, and specific growth rate. Notably, the feed conversion ratio was substantially improved in T2 and T3 groups. While the application of ND07 did not significantly affect survival rates, it exhibited pronounced improvements in immune and antioxidant parameters. This was evidenced by elevated activities of Phenoloxidase, Lysozyme, and Catalase in the shrimp plasma. Subsequent to the treatment trial, a challenge experiment with Vibrio vulnificus revealed a statistically significant increase in survival rates among the infected shrimp that received ND07 treatments, in comparison to the untreated control group. In addition, shrimp in the treatment groups showed significantly decreased histological changes of the hepatopancreas organ caused by vibrio infection. These results suggest that the administration of ND07 in shrimp rearing water confers beneficial effects for shrimp aquaculture. The application of ND07 at densities of 10⁵ and 10⁶ CFU/mL not only facilitated a reduction in TAN and nitrite concentrations, but also promoted growth performance in shrimp. Furthermore, a concentration of 10⁶ CFU/mL of ND07 was particularly effective in enhancing immune and antioxidant enzymatic activities, as well as boosting resistance to diseases caused by pathogenic Vibrios.