Exploratory analysis of the relationship between the water quality and the microbiome in Santa Catarina reservoir, Querétaro, Mexico

Abstract

The Santa Catarina Dam (Querétaro, Mexico) is a freshwater reservoir supporting agriculture and aquaculture, but anthropogenic pressure has intensified nutrient enrichment and contamination. Water samples were collected from two points for physicochemical characterization and shotgun metagenomic profiling. DNA sequences were quality filtered, assembled, and classified to quantify taxonomic composition and functional gene abundance. Processed data were statistically analyzed in Python 3.0 to compare physicochemical parameters, taxa, and gene abundance. Results showed that chemical oxygen demand (COD) and hydrogen potential (pH) exceeded recommended limits. Fecal coliform counts (FCC) were high at both points, while biochemical oxygen demand (BOD5) and total nitrogen (TN) approached critical thresholds. Significant differences in water temperature (WT), dissolved oxygen (DO), and total phosphorus (TP) were observed between sites. The microbial communities presented high diversity and a moderate dissimilarity among points. Besides, three cyanobacterial species were identified within the top 10 most abundant taxa. Functional annotation of the combined dataset revealed high gene abundance associated with energy production (35.40%), stress resistance (18.00%), and unknown functions (14.54%). These results indicate an eutrophic state of the water body and potential health risks. Differential statistical analysis revealed site-specific taxa and genes, several of which may have biotechnological applications.