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Aquatic Microbial Ecology


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AME 86:99-114 (2021)  -  DOI: https://doi.org/10.3354/ame01956

Key drivers of microbial abundance, activity, and diversity in karst spring waters across an altitudinal gradient in Slovenia

Maja Opalički Slabe1,2,*, Tjaša Danevčič3, Katrin Hug4, Lucas Fillinger5, Ines Mandić-Mulec3, Christian Griebler4,5, Anton Brancelj1,2

1National Institute of Biology, Department of Organisms and Ecosystems Research, 1000 Ljubljana, Slovenia
2University of Nova Gorica, Graduate School, Environmental Sciences, 5000 Nova Gorica, Slovenia
3University of Ljubljana, Biotechnical Faculty, Department of Food Science and Technology, Chair of Microbiology, 1000 Ljubljana, Slovenia
4Helmholtz Zentrum München, German Research Centre for Environmental Health, Institute of Groundwater Ecology, 85764 Neuherberg, Germany
5University of Vienna, Department of Functional and Evolutionary Ecology, 1090 Vienna, Austria
*Corresponding author:

ABSTRACT: In aquatic ecosystems, the biomass, activity and composition of microorganisms are determined to a large extent by local and regional environmental conditions. While karst aquifers are an important source for drinking water, the ecology of microbial communities in karst waters has hardly been studied. This study examined the regional variations and seasonal dynamics of microbial communities in pristine karst spring waters of Slovenia (Central Europe). Fifteen springs distributed across 5 eco-regions exhibiting a strong altitudinal gradient were sampled 4 times a year. Evaluation of the microbial communities included quantification of prokaryotic biomass via total cell counts and microbial activity estimated via measurements of electron transport system activity. The taxonomic structure of the bacterial communities was analysed by terminal restriction fragment length polymorphism fingerprinting. Biological measures were complemented by a set of physico-chemical parameters, including dissolved organic carbon, nutrients, major ions, temperature, electrical conductivity, pH, and dissolved oxygen. Bacterial community structure differed significantly with seasons and eco-regions, with the latter causing greater variation. While the overall power of the environmental variable tested was a moderate factor (15%) in explaining the variability in microbial community structure, catchment altitude was a key determinant. Prokaryotic cell density and microbial activity in spring water decreased with an increase in catchment altitude and were significantly positively correlated. For a better understanding of karst ecosystems and the ecosystem service of water purification, future investigation should address karst microbial communities at a higher phylogenetic and functional resolution.


KEY WORDS: Karst springs · Microbial diversity · Total cell counts · TCC · Electron transport system activity · ETSA · Terminal restriction fragment length polymorphism · T-RFLP


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Cite this article as: Opalički Slabe M, Danevčič T, Hug K, Fillinger L, Mandić-Mulec I, Griebler C, Brancelj A (2021) Key drivers of microbial abundance, activity, and diversity in karst spring waters across an altitudinal gradient in Slovenia. Aquat Microb Ecol 86:99-114. https://doi.org/10.3354/ame01956

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