Fecal bacteria in coastal lakes: An anthropogenic contamination or natural element of microbial diversity?

Abstract

The effects of multiple stressors (salinity, temperature, nutrient and light availability or human activities) on the abundance of FIB (Escherichia coli and Enterobacteriaceae) were studied in nine lakes on the southern Baltic coast. Monitoring also included physicochemical factors and land use in the catchment. The results showed that FIB is a natural component of microbial community in coastal lakes, with its abundance varying temporally and spatially. The key factors predicting the abundance of E. coli and Enterobacteriaceae are the availability of ammonia nitrogen and water temperature. Regardless of the degree of connection with the sea, the sanitary condition of coastal lakes deteriorates during the summer months. Although agricultural use and residential development do not significantly affect fecal bacteria counts (PLS-R model), human pressure on the sanitary condition of lakes increases seasonally and is limited to the vicinity of tourist sites. The degree of contact with seawater regulates the size of the microbial community, but is not a factor that directly affects the presence of E. coli in the microbial community in coastal lakes. Monitoring the sanitary conditions of these ecosystems using sensitive, rapid survey methods based on hydrochemical and microbiological inventories, supported by GIS, is important for public health.