In–situ aquaculture treatment: Co–addition of autotrophic and heterotrophic bacteria with biodegradable polymers (PHBV) to Penaeus vannamei culture systems

Abstract

As a novel trend, biodegradable polymers, specifically poly(3–hydroxybutyrate–co–3–hydroxyvalerate) (PHBV), are being utilized as carbon source and biofilm carrier in the in–situ aquaculture systems to remove nitrogen from wastewater. This study investigated the differential responses to various aquaculture systems with the addition of autotrophic bacteria and PHBV (PNB group), heterotrophic bacteria and PHBV (PBS group), autotrophic and heterotrophic bacteria, along with PHBV (PBN group), single autotrophic bacteria (NB group), as well as clear water system (the control, CN group), on the growth, immune enzyme activity, water quality, and microbiota in rearing water, shrimp intestine, carbon source in Penaeus vannamei culture systems. Results showed that these culture systems were more effective in improving water quality than clear water system, with PBN group exhibited the best performance. The growth and immune enzyme activity of shrimp in these culture systems were significantly enhanced than those in clear water system. Although microbial diversity in rearing water, shrimp intestine, and carbon source was not significantly altered, differences in microbial community richness were observed in rearing water and carbon source. Significant differences in microbial community structure were noted in rearing water, but no such differences were observed in shrimp intestine or carbon source. Total ammonia nitrogen, total nitrogen, and nitrite nitrogen were identified as primary drivers of microbial community changes in rearing water, shrimp intestine, and carbon source, respectively. Furthermore, these culture systems significantly altered keystone nodes in microbial networks, with PBS group improving the stability of microbial networks in both rearing water and shrimp intestine. The addition of autotrophic and heterotrophic bacteria, along with PHBV in system increased the proportion of nitrogen cycling functions within microbial communities in rearing water and carbon source. Additionally, the abundance of potential pathogens in shrimp intestinal microbial communities decreased to varying degrees in these culture systems, particularly in NB group. The PBN, PBS and PNB groups significantly altered microbial community composition of the habitats in rearing water, shrimp intestine, and carbon source compared to clear water system. Notably, shrimp intestinal microbial communities were more similar to carbon source than to those in rearing water. This study evaluated the feasibility and advantages of using PHBV as carbon source and biofilm carrier in various aquaculture systems, thereby expanding the application prospects of biodegradable polymers in aquaculture practices.