Escherichia coli and enterococci are sensitive and reliable indicators for human, livestock and wildlife faecal pollution in alpine mountainous water resources

Abstract

Aims: This study evaluated the applicability of standard faecal indicator bacteria (SFIB) for alpine mountainous water resources monitoring.

Methods and results: Escherichia coli, enterococci (ENTC) and Clostridium perfringens were investigated by standard or frequently applied phenotypic and genotypic methods in a broad range of animal and human faecal sources in a large alpine mountainous area. Clostridium perfringens occurred only in human, livestock and carnivorous source groups in relevant average concentrations (log 4·7-7·0CFU g(-1) ) but not in herbivorous wildlife sources. Escherichia coli proved to be distributed in all faecal source groups with remarkably balanced average concentrations (log 7·0-8·4CFU g(-1) ). Except for single faecal samples from the cattle source group, prevalence rates for ENTC source groups were generally >87% with average concentrations of log 5·3-7·7 CFUg(-1) . To test the faecal indication capacity in the environment, faecal prevalence data were comparatively analysed with results from the concurrently performed multi-parametric microbial source tracking effort on karst spring water quality from the investigated alpine mountainous catchment (Reischer et al. 2008; Environ Microbiol 10:2598-2608).

Conclusion: Escherichia coli and enterococci are reliable faecal indicators for alpine mountainous water resources monitoring, although E. coli is the more sensitive one. Clostridium perfringens did not prove to be an indicator of general faecal pollution but is suggested a conservative microbial source tracking marker for anthropogenic faecal influence.

Significance and impact of the study: Applicability of SFIB is currently hotly debated. This is the first study providing comprehensive information on the applicability of SFIB at alpine mountainous habitats.

Fig. 1

Correlation analysis of log E.coli versus log enterococci (ENTC) concentrations (a), log E.coli versus log Clostridium perfringens concentrations (b), and log enterococci versus log Clostridium perfringens concentrations (c) as found in wildlife, livestock and human pollution sources in the investigated catchment. Spearman correlation coefficients (ρ) were calculated. The diagonal shows the 1:1 ratio of the respective couples of indicators.

Fig. 2

Correlation plot of log E.coli versus log enterococci (ENTC) concentrations as found in animal and human faecal pollution sources and in the respective spring water of the LKAS2. The diagonal shows the 1:1 ratio. Indicator concentrations from spring water are given in log CFU per 10 m³ of spring water.