Escherichia coli (E. coli) distribution in the Lake Malawi nearshore zone

Residents along the shoreline of lake Malawi depend on nearshore water for drinking, cooking, and bathing. Despite the importance of clean nearshore waters to public health, we are aware of no published studies of shoreline water quality in the lake. To address this gap, we explore seasonal and temporal trends of the fecal indicator bacteria Escherichia coli (E. coli) in nearshore water and sand. E. coli concentrations in sand ranged from 0 to 17,600 colony forming units (CFU)/100 ml, and in water concentrations ranged from 0 to 21,200 CFU/100 ml. Fifty-three percent of water samples exceeded the U.S. Environmental Protection Agency Recreational Water Quality Criteria of 126 CFU/100 ml, and 90% exceeded the World Health Organization drinking water standard of 0 CFU/100 ml. Distance from shore was the variable most predictive of E. coli concentration, with the level of beach use also playing a significant role. At 15 m from the shore, E. coli concentrations dropped to between 0.3% and 17% of shoreline values. Results suggest that the collection of water at distances >15 m from the beach could substantially decrease exposure to fecal bacteria. Further studies are needed to identify sources of fecal pollution and to determine the utility of E. coli as a predictor of the potential for waterborne disease. (C) 2018 International Association for Great lakes Research. Published by Elsevier B.V. All rights reserved.