Microbiome and Metabolome Analyses in Different Closed-Circulation Aquarium Systems and Their Network Visualization

[Image: see text] Understanding the causes of microbiome formation and its relationship to environmental conditions is important to properly maintain recirculating aquaculture systems (RASs). Although RAS has been applied to numerous fish types and environmental conditions (e.g., loading intensity), the effects of these environmental conditions (i.e., fish type and loading intensity) on microbiome composition are limitedly known. Therefore, we established three experimental aquarium tanks to explore the effects of fish type, loading intensity, filter pore size, and rearing day on microbiome compositions: (1) a tank for Acanthogobius flavimanus, (2) for Girella punctata, and (3) for G. punctata with higher loading intensity. Multivariate analysis showed that the microbial community composition differed among the tanks, indicating that the fish type and loading intensity significantly affected microbiome formation in rearing water. Some microbes, such as Sediminicola and Glaciecola, were detected at a higher loading intensity, indicating that these microbes might be an indicator of eutrophic conditions in the aquacultural systems. In addition, a partial correlation network revealed a connection between microbes and metabolites in the aquarium tanks. Such a microbe–metabolite network might be a clue to control the microbiome by adjusting the molecule abundance in the aquacultural environment.