Application of a nitrifying bacterium Pseudomonas sp. HIB_D to reduce nitrogen waste in the Litopenaeus vannamei cultivation environment

Pseudomonas sp. HIB_D has been observed to have nitrification activity that can oxidize ammonia/ammonium to nitrite and nitrate. This bacterium was isolated from the aquaculture environment with Ancol Indonesian marine water sources. Pseudomonas sp. HIB_D was applied in the rearing water of Litopenaeus vannamei to decrease nitrogen pollution levels and support a sustainable cultivation environment. This present study was set up using a completely randomized design with four treatments and three replications, i.e., control (without bacterial application) and bacterial application with a cell density of 107, 108, and 109 CFU mL−1 in a volume of 100 mL for 90 L seawater treatment. Thirty-six individuals of 15-day-old postlarvae L. vannamei (PL 15) (a density of 120 PL m-2) were used in this study for an 8-week rearing period. Based on the water quality analysis, the ammonia level under the bacterial applications was lower than in the control after 8-week cultivation. Nitrate levels increased at week 6 and decreased at week 8, specifically in 109 CFU mL−1 treatment. L. vannamei with 109 CFU mL−1 bacterial application had the best production performance with a survival rate of 94.33 ± 2.78%, an absolute length gain of 10.59 ± 0.22 cm, an absolute weight gain of 8.16 ± 0.33 g, a specific growth rate of 14.12% ± 0.01% day−1, and a feed conversion ratio of 1.26 ± 0.03. The blood glucose level and total hemocyte count of shrimp under the bacterial application with a density of 109 CFU mL−1 showed the highest level (30.71 ± 13.9 mg dL−1) and the lowest level (15 × 106 cells mL−1), respectively. The results showed that all treatments performed better than the control, in which the 109 CFU mL−1 bacterial application was the best treatment.