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In aquatic animals, the gut microbiota has a significant function in host health and is impacted by the environmental microbiota. To conveniently monitor, assess and predict aquatic animals’ health, a general and effective microbiota health index (microHI) would be helpful, and the correlation between the aquatic environmental microHI and wildlife gut microHI could be expected. Here, we proposed a general microHI based on the microbial phenotypes of mobile element content, potential pathogenicity and oxidative stress tolerance, and then tested the reliability of the fish gut microHI and its correlation with the environmental microHI in the middle Yangtze River. The results showed that there were positive correlations among the abundance ratios of microbes with the microbial phenotypes of mobile element content, potential pathogenicity and oxidative stress tolerance, suggesting that defining the microHI using the average abundance ratios of microbes without these microbial phenotypes is suitable. Fish gut samples with a lower microHI were more likely to have been obtained from specimens with a disordered microbiota (always means unhealthy host), indicating that the gut microHI has the potential to be used to evaluate the health status of aquatic animals. In the middle Yangtze River, the aquatic environmental microHI had hundred-kilometers-scale high spatial heterogeneity but month-scale low temporal heterogeneity from June to September 2020, and in the section with a low aquatic environmental microHI, the fish gut samples were more likely to have relatively low gut microHIs, indicating that the environmental microHI has the potential to be used to predict the health status of aquatic animals at the community level. The current work initially showed the possibility of using environmental microHI to predict aquatic animals’ health although it was not very exact and precise. We encourage more researches to assess the quantitative relationship between the aquatic environmental microHI and aquatic animal gut microHI.

[Display omitted] • Aimed to create a non-invasive method to monitor aquatic animals' health. • Proposed a microHI (microbiota health index) based on three microbial phenotypes. • Tested the viability of using gut microHI to predict host health in 11 fishes. • Verified the positive correlation between environmental microHI & fish gut microHI. • Showed the possibility of using environmental microHI to predict animals' health. In aquatic animals, the gut microbiota has a significant function in host health and is impacted by the environmental microbiota. To conveniently monitor, assess and predict aquatic animals' health, a general and effective microbiota health index (microHI) would be helpful, and the correlation between the aquatic environmental microHI and wildlife gut microHI could be expected. Here, we proposed a general microHI based on the microbial phenotypes of mobile element content, potential pathogenicity and oxidative stress tolerance, and then tested the reliability of the fish gut microHI and its correlation with the environmental microHI in the middle Yangtze River. The results showed that there were positive correlations among the abundance ratios of microbes with the microbial phenotypes of mobile element content, potential pathogenicity and oxidative stress tolerance, suggesting that defining the microHI using the average abundance ratios of microbes without these microbial phenotypes is suitable. Fish gut samples with a lower microHI were more likely to have been obtained from specimens with a disordered microbiota (always means unhealthy host), indicating that the gut microHI has the potential to be used to evaluate the health status of aquatic animals. In the middle Yangtze River, the aquatic environmental microHI had hundred-kilometers-scale high spatial heterogeneity but month-scale low temporal heterogeneity from June to September 2020, and in the section with a low aquatic environmental microHI, the fish gut samples were more likely to have relatively low gut microHIs, indicating that the environmental microHI has the potential to be used to predict the health status of aquatic animals at the community level. The current work initially showed the possibility of using environmental microHI to predict aquatic animals' health although it was not very exact and precise. We encourage more researches to assess the quantitative relationship between the aquatic environmental microHI and aquatic animal gut microHI. [ABSTRACT FROM AUTHOR]