Human fecal pollution source tracking in Coronel Bay (Chile) and adjacent wetlands

Abstract

Human fecal pollution in the coastal ocean and fresh water is a global concern, not only regarding the risk to human health, but also due to its effects on the ecosystem. In the present work, human fecal contamination was traced during the 2019 austral summer season in Bahía de Coronel and in two of the adjacent freshwater bodies that drain into the Gulf of Arauco. Total and fecal coliforms, human mitochondrial DNA (HmtDNA), live microbial biomass (ATP), the multiresistance antibiotic index (MARi) and the physical-chemical parameters of the water were determined. In the study area, fecal contamination was observed between one to two orders of magnitude above the Chilean Norm (NCh.) 1333 and a positive and strongly significant correlation (p << 0,05), between fecal coliforms and live microbial biomass was determined. In Bahía Coronel a significant Log-log correlation (p < 0,05) was observed between fecal coliforms and HmtDNA, which indicates that at least 43% of the fecal contamination in the bay was from human origin. In the upper part of the adjacent freshwater bodies, fecal contamination is also observed, but from a different origin than human. However, the significant correlation (p < 0,05) between fecal coliforms and the MARi index observed for freshwater also suggests an anthropogenic effect in that area. Finally, at the sampling date the results indicate that the study area was risky for human health by microbiological pollution, which could eventually limit its use as recreational ocean waters or strategic reserves of fresh water in the future.