TRANSPORT OF MICROORGANISMS IN THE KARST CATCHMENT OF GALLUSQUELLE SPRING (SWABIAN ALB, GERMANY, EUROPE)

Karst springs are important for drinking water supply but are vulnerable to contamination. Many karst springs exhibit a decline in microbial water quality shortly after rainfall, posing a health risk to consumers who rely on these water resources. In this study, the occurrence of microorganisms (faecal indicator bacteria) and antibiotic resistance genes in the karst springwater of the Gallusquelle (Swabian Alb, Germany) was trialed in order to evaluate which methods can be used to monitor rainfall-induced rapid changes in microbial water quality at karst springs, and to determine whether such changes can be linked to sources of human effluent. To accomplish these objectives, we investigated the feasibility of organic micropollutants as a source specific indicator set, discharge at the spring and information on land use in the karst catchment to derive information on the origin of contamination.

The results reveal marked responses to rainfall events for selected organic micropollutants and all microbial parameters measured. The correlations of the microbiological parameters, the concentrations of selected micropollutants and general hydrochemical data show that the overflow of an undersized rainwater and sewage water retention basin is likely to be the source of this contamination. The basin is located approximately 9 km away from the spring and it takes around 100 hours to reach Gallusquelle spring, demonstrating that microorganisms in karst systems may travel significant distances.