Abstract:Ammonia nitrogen and nitrite nitrogen accumulation often occur in industrial whiteleg shrimp (Penaeus vannamei) farming and has a negative impact. To explore the role of microorganisms in ammonia nitrogen and nitrite nitrogen accumulation, water samples from industrial farming systems of P. vannamei were randomly collected and divided into four groups. The four groups were as follows: DG group, ammonia nitrogen<1.33 mg/L and nitrite nitrogen<0.77 mg/L; DB group, ammonia nitrogen>2.53 mg/L and nitrite nitrogen<0.77 mg/L; DY group, ammonia nitrogen<1.33 mg/L and nitrite nitrogen>2.55 mg/L; DR group, ammonia nitrogen>2.53 mg/L and nitrite nitrogen>2.55 mg/L. 16S rRNA sequencing technology was used to analyze the microbial structure of each group, real-time quantitative PCR was used to determine the absolute abundance of nitrogen cycling genes, and Person correlation analysis was conducted for microbial abundance, environmental factors, and nitrogen cycling gene abundance. The relative abundances of Rhodobacteraceae in the DY and DR groups were higher than those in the DG and DB groups, while that of Stappiaceae was lower than that in the DG and DB groups. The relative abundance of norank_o__PeM15 was significantly higher in DG group than that in the other three groups (P<0.05). Among bacteriaceae, Cyanobiaceae, Saprospiraceae, and Cryomorphaceae were significantly positively correlated with ammonia nitrogen, whereas Microbacteriaceae was significantly positively correlated with nitrite nitrogen (P<0.05). The absolute abundances of nitrogen cycling functional genes in DR Group were the highest, and the absolute abundances of narG, nirS, nirK, amoA, and ureC were significantly different from those in other groups (P<0.05). Among functional genes, the abundance of amoA was positively correlated with ammonia nitrogen and nitrite nitrogen, whereas nirS was positively correlated with nitrite nitrogen (P<0.05). These results suggest that the variation of the abundances of Saprospiraceae, Cryomorphaceae, and Microbacteriaceae may affect ammonia nitrogen and nitrite nitrogen concentrations in water. The absolute abundance of nitrogen cycling genes in water with high ammonia nitrogen and nitrite nitrogen concentrations was high. Our study reveals the relationship between water microorganisms, nitrogen cycling genes, and nitrogen-containing compounds, and provides theoretical support for addressing harmful nitrogen accumulation in shrimp industrial farming via microorganism regulation.
