Satellite-empowered public health: Mapping coastal fecal contamination risks through Sentinel-2 imagery

Coastal waters serve as essential ecological habitats, key drivers of the blue economy, and vital resources for public health. However, increasing anthropogenic pressures, coupled with climate-driven perturbations, present significant challenges to microbial water quality. While remote sensing has been widely adopted for assessing physicochemical water quality parameters, its application to microbial indicators remains limited. To evaluate the feasibility of integrating satellite observations into microbial water quality assessments, this study investigated the hypothesis that satellite derived suspended matter concentrations predict levels of fecal indicator bacteria, Escherichia coli (E. coli), which are linked to human health through epidemiological studies. A moderate correlation was observed with the Sentinel-2 derived total suspended matter (SPM) and in situ E. coli concentrations (r = 0.73, p < 0.001), and the positive correlation was also validated using a historical dataset obtained from the California Water Board. The results indicate that using satellite data for estimating E. coli concentrations in coastal waters is feasible. This approach can enhance the performance and expand the scope of pollution event warning systems, demonstrating the valuable role of satellite data in environmental monitoring and public health protection.