In Situ Recirculating Aquaculture System Improves the Growth Performance of Shrimp (Penaeus vannamei) via Shaping...

The in situ recirculating aquaculture system (IS-RAS) is regarded as an effective measure to reduce shrimp disease risks by minimizing exogenous water input and improving water quality. However, little is known about the effects of this system on bacterial communities in shrimp gut and rearing water. Here, the growth performance of shrimp and bacterial community characteristics in this culture system were assayed. The results show that the IS-RAS significantly improved rearing water quality, with a 2.2-fold reduction in turbidity, a 68.2% decrease in nitrite concentration, and enhanced hepatopancreatic digestive enzyme activities (e.g., amylase and lipase) and antioxidant capacities (e.g., superoxide dismutase and total antioxidant capacity). These improved physiological and biochemical indexes in the IS-RAS significantly increased the yield and survival rate, with increments of 23.5% and 25.9%, respectively, compared to that in CK. The IS-RAS significantly increased the bacterial diversity and enriched certain keystone taxa belonging to Roseobacteraceae, Paracoccaceae, Flavobacteriaceae, Nitrosomonadaceae, and Nitrospiraceae in both water and shrimp gut. These taxa play critical roles in maintaining bacterial network stability, and some of them were identified as potential taxa for promoting shrimp growth. Furthermore, the IS-RAS significantly upregulated functional genes associated with nitrogen metabolism (e.g., nirS, nirA, norB, napA, napB, and pmoA-amoA), thereby enhancing the nitrogen cycling potential of the bacterial community. These findings elucidate the biological mechanisms underlying IS-RAS-mediated improvements in shrimp farming productivity.