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 (-N), ammonium-nitrogen (-N), nitrate-nitrogen (-N) and phosphate-phosphorus (-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.

中文翻译：

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添加蔗糖对南美白对虾养殖系统水质及浮游细菌群落的影响

据报道，蔗糖是一种有效的碳源，可以改善生物絮团培养系统中的水质。然而，添加蔗糖改善水质的微生物机制仍有待充分阐明。本研究旨在评估三种 C/N 比水平（CK、CN10 和 CN15）对南美白对虾养殖系统中对虾生长、水质和浮游细菌群落的影响。结果表明，与CK组相比，CN10和CN15组的生长性能显着提高。亚硝酸-氮（-N）、铵-氮（-N）、硝酸-氮（-N）和磷-磷（-P)在CN10和CN15组中明显低于CK组。高碳氮比输入提高了红杆菌科、黄杆菌科和腐霉科的相对丰度，降低了弧菌科和支原体科的相对丰度。通过添加蔗糖诱导的歧视性 OTU 显示出与水质参数的显着相关性。此外，通过预测浮游细菌群落的功能注释，我们发现蔗糖的添加增强了反硝化作用和亚硝酸盐呼吸作用，减少了病原体相关表达的积累。综上所述，蔗糖的添加可能通过调节浮游细菌群落的变化，为虾的生长提供一个健康的水环境。