CrAssphage distribution analysis in an Amazonian river based on metagenomic sequencing data and georeferencing

The Amazon biome is one of the most diverse ecosystems in the world and contains the most vast river network; however, the continuous advance of urban centers toward aquatic bodies exacerbates the discharge of pollutants into these water bodies. Fecal contamination contributes significantly to water pollution, and the application of an improved fecal indicator is essential for evaluating water quality. In this study, we evaluated the presence, diversity, and abundance of crAssphages in an Amazonian river and performed correlation analysis on the basis of physicochemical and georeferencing data to test whether crAssphages are viable fecal pollution markers. Our analysis revealed both the presence of crAssphages and their correlation with physicochemical data and showed significant correlations between the relative abundance of crAssphages and human density. These results suggest the potential use of these viruses as markers for water quality assessment in Amazonian rivers.