Effects of sucrose addition on water quality and bacterioplankton community in the Pacific White Shrimp (Litopenaeus vannamei) culture system

Sucrose has been reported as an effective carbon source for improving water quality in the biofloc culture system. However, the microbiological mechanisms of adding sucrose on water quality improvement remain to be fully clarified. This study was conducted to evaluate the effects of three C/N ratio levels (CK, CN10, and CN15) on shrimp growth, water quality and bacterioplankton community in shrimp (Litopenaeus vannamei) culture system. The results showed that the growth performances were significantly improved in CN10 and CN15 groups, compared with those in CK group. The contents of nitrite-nitrogen (NO2--N), ammonium-nitrogen (NH4+-N), nitrate-nitrogen (NO3--N) and phosphate-phosphorus (PO43--P) in the CN10 and CN15 groups were significantly reduced, compared with those in CK group. High input of C/N ratio enhanced the relative abundances of Rhodobacteraceae, Flavobacteriaceae Demequinaceae and Saprospiaceae, and decreased the relative abundances of Vibrionaceae and Mycoplasmataceae. The discriminatory OTUs induced by adding sucrose showed significant correlations with water quality parameters. Additionally, by predicting functional annotation of bacterioplankton community, we found that the addition of sucrose enhanced the function of denitrification and nitrite-respiration, and reduced the accumulation of pathogens-related expression. In conclusion, sucrose addition may provide a healthy water environment for shrimp growth by regulating the changes of bacterioplankton community.