Intensive cultivation of whiteleg shrimp (Litopenaeus vannamei) under biofloc condition in land-based ponds

Land-based pond systems, as an emerging intensive aquaculture model, have encountered developmental constraints due to toxic nitrogen levels. This study aimed to develop and evaluate a biofloc-mediated aquaculture system in land-based ponds, focusing on water quality, bacterial composition of bioflocs, shrimp growth performance, and nonspecific immunity. Juveniles of Litopenaeus vannamei were stocked in three identical land-based barrel tanks at a density of 600 individuals·m −2 for a 90-day cultivation period, with no water exchange. The results indicated that total ammonia nitrogen (TAN) concentrations were maintained between 0 and 4 mg·L −1 , and nitrite (NO 2 - -N) levels were kept between 0 and 1.0 mg·L −1 . Bacterial community analysis revealed that the richness and Shannon index of bioflocs at 90 days were significantly higher, yet the dominant bacteria throughout the trial remained consistent, comprising Proteobacteria , Actinobacteria , Planctomycetes , Bacteroidetes , and Chloroflexi . Redundancy Analysis (RDA) demonstrated that Bacteroidetes were significantly positively correlated with TAN and NO 2 - -N at 30 and 60 days, while Chloroflexi showed a positive correlation with nitrate (NO 3 - -N) and phosphate (PO 4 3- ) at 90 days. Growth performance metrics indicated a survival rate (SR) of L. vannamei at (78.36 ± 1.81)%, yield of (8.63 ± 0.33) kg·m −3 , specific growth rate (SGR) of (2.05 ± 0.04)%·d −1 , feed conversion rate (FCR) of 1.53 ± 0.25, and water usage of (192.29 ± 9.01) L·kg −1 (shrimp). The relative expression levels of immune-related genes, including SOD , CAT , LZM , proPO , TLR2 , and VEGF1L , exhibited an increasing trend over the course of the aquaculture process. Collectively, the findings suggest that bioflocs effectively regulated water quality and enhanced shrimp growth, production, and immune status. • A zero-water-exchange, biofloc-based L. vannamei aquaculture system in land-based tanks has been established. • Bioflocs regulated water effectively, keeping TAN and NO 2 - -N at low levels. • Biofloc bacteria were closely linked to water quality factors, including TAN, NO 2 - -N, NO 3 - -N, and COD. • Bioflocs positively impact shrimp growth and immune status.