Aquaponics model can provide better productivity: Microorganisms affect the growth and health of tilapia

Aquaponics is a novel ecological agricultural strategy that combines aquaculture and hydroponic cultivation. The relationships between fish immunological and digestive functions, water quality, and bacterial populations were not well understood. This study aims to investigate the effects of aquaponics on aquaculture water quality, fish growth performance, and fish health, as well as exploring the roles of microbial taxa in these processes. In the present study, three aquaponics systems were established, and three same sized recirculating aquaculture systems (RAS) were constructed to act as controls. To evaluate bacterial community diversity and compositions across different microhabitats in the two systems, we used amplicon-based high-throughput sequencing technique targeting the 16S rRNA gene. In aquaponics, fish had a much greater nitrogen utilization rate, weight gain rate (WGR), feed conversion ratio (FCR), and specific growth rate (SGR) than in controls. The activities of alkaline phosphatase (AKP), acid phosphatase (ACP), lysozyme (LYS), lipase (LPS), and trypsin (TRP) in tissues, all of which are indicators of fish health, were significantly greater in aquaponics than in controls. Aquaponics effectively lowered chlorophyll-a levels while having little effect on other water quality metrics, indicating their potential for better algae control. Water quality measures such as dissolved organic carbon, chlorophyll-a, dissolved oxygen, and ammonia nitrogen had a substantial impact on the fish's immunological and digestive capabilities. In terms of microbial influence, particular gut bacteria—such as the bacterial orders Pseudomonadales, Caulobacterales, Defluviicoccales, Exiguobacterales, and Gemmatales—have been identified as influencing various functions in fish. Among these bacterial orders, we found that Pseudomonadales and Exiguobacterales were more abundant in aquaponics than control systems. This study demonstrated that aquaponics can increase fish health and productivity through the management of water quality and certain microorganisms, particularly gut microbiota. • Compared to recirculating aquaculture systems, the growth performance and health status of fish produced in aquaponics systems are better. • Significant interactions exist among the digestive and immune functions of fish, water quality, and microbial communities. • The digestive and immune functions of fish are influenced by 18 types of gut bacteria.