Investigation of bacterioplankton communities in aquatic karst pools in Bärenschacht cave of Bernese Oberland

T. Shabarova
J. Pernthaler

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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.