Abstract
Karst subterraneous aquifers are highly diverse in structure and very important in the formation of
ground water, which is the main source of freshwater supply for a significant proportion of the world’s
population. Microorganisms can play an important role in karstification, carbon cycle and element
mobility, but so far little is known about the bacteria of aquatic karst ecosystems. In this study, karst
pools with differing hydrology in the Bärenschacht cave of the Bernese Oberland, Switzerland were
investigated for a period of six months. Two crystalline pools were supplied by dripping water whereas
one epiphreatic pool was renewed only by the rising groundwater table at intervals of several days
to months. Chemical parameters such as conductivity, pH, ion concentration, as well as bacterial
abundance and diversity were determined at several time points. The investigated pools showed
remarkably different physicochemical parameters as well as bacterial properties. Although the dominant
bacterial group in all three systems was β-Proteobacteria, no population overlap inside this group was
found between the crystalline pools and the epiphreatic system. Actinobacteria were present mainly
in the systems with dripping water supply, whereas bacteria from the Flavobacteriaceae family were
identified in both types of systems. Some microorganisms affiliated with Bacteroidetes could also be
isolated and investigated in more detail. Generally, most of the identified microorganisms were not
closely related to typical freshwater bacteria. Therefore, karst habitats might represent an environment
for very specialized microorganisms.
Shabarova, T