The degradation of the water quality in the Tijuana River Watershed poses a serious health risk to the communities of San Diego and Tijuana. The older sewage infrastructure has not been able to keep up with the growth of the surrounding cities, causing an overflow from treatment plants, especially during times of heavy rain. The increasing level of contamination in the Tijuana River detrimentally affects the surrounding socioeconomically disadvantaged cities of San Ysidro and Imperial Beach and may be a cause of the increased incidence of chronic disease in the area. We performed untargeted metagenomic sequencing to better understand the potential role that sewage contamination in the Tijuana River plays on the health of those living in its proximity. Water samples were collected from six different sites along the river. After filtration, the DNA was extracted and sequenced for metagenomic analysis. The sequences were quality controlled and run through a taxonomic classification program. A pathogen profile of the most abundant disease-causing microbes and viruses present in each of the samples was constructed, and specific markers of fecal contamination were identified and linked to each site. Results from diversity analysis between the sites showed clear distinction as well as instances of grouping. This and future metagenomic analyses of contaminated water samples will help bring awareness and a more targeted solution to this growing problem.
