Microbial Activity in Alpin Karst Spring Water

In mountainous areas like Austria, groundwater resources from alpine karst aquifers play a fundamental role for high quality public water supply. Consequently, alpine karst research has to provide the basic scientific understanding which enables to take all necessary steps for long term maintaining the ecological integrity of the respective alpine catchment areas. Recently conducted studies by our research group demonstrated for the first time the occurrence of a diverse microbial community including prokaryotic and eukaryotic microorganisms as well as viral particles in spring water of alpine karst aquifers. Furthermore, our research indicate that at least a significant fraction of the observed microbes are indigenous to the karstic aquifer environment itself. The so called "autochthonous microbial endokarst communities" in the spring water are likely to originate from sloughed cells attached to the rock surfaces and deposited sediments in the aquifer or occur simply suspended in low - flow interstitial areas. The question arises about the consequences of these microbial communities? Are they simply a passive collection of living organic matter or do they constitute a giant active bioreactor in the karst aquifer with all ecological consequences? The proposed study will set the first crucial steps in evaluating the relevance of microbial metabolism in alpine karstic spring water and respective biofilm compartments. Results are of high interest for a better understanding of basic alpine karstic groundwater ecology (e.g. organic matter cycling, deep phreatic karstification) as well as for public water provision issues (e.g. self purification capacity of karstic aquifers, biological stability and quality of abstracted spring water). The proposal focus on the investigation on prokaryotic activity as it is considered the catalytic thriving force of dark - heterotrophic processes. As outlined in the proposal, the applying research group already successfully adapted sensitive state of the art techniques for the determination of prokaryotic activity and community structure in spring water during a one years EU funded collaboration in 2003 to 2004 with the NIOZ. For the first time it will become possible to link prokaryotic community composition, active cell compartments and total community production in spring water and respective biofilm compartments by means of catalysed reporter deposition fluorescence in situ hybridisation (CARD-FISH), microautoradiography and in situ prokaryotic production measurements ( 3 H-Leu incorporation). Furthermore by using "on-line" hydrological and chemographical information of the respective spring catchment itself, evaluation of the significance of prokaryotic activity for karst aquifer ecology and biogeochemical processes can be undertaken. Because alpine karstic aquifers, especially the saturated zones, are not directly accessible the investigation will be based at spring locations investigating spring water as well as corresponding re suspended sediments and their attached biofilms by permanently installed sediment traps. Thus, an evaluation of the significance of attached vs. suspended prokaryotes will become possible. A seasonal variation analysis covering two summer and one winter season and additionally two flood investigations will be undertaken. The selected "model" alpine catchment areas of the DKAS1 and LKAS2 spring have already proved an excellent setup in previous studies. It should be mentioned that this research involves the close cooperation of microbial ecologists, hydrologists and public water works.

In mountainous areas like Austria, groundwater resources from alpine karst aquifers play a fundamental role for high quality public water supply. Consequently, alpine karst research has to provide the basic scientific understanding which enables to take all necessary steps for long term maintaining the ecological integrity of the respective alpine catchment areas. Recently conducted studies by our research group demonstrated for the first time the occurrence of a diverse microbial community including prokaryotic and eukaryotic microorganisms as well as viral particles in spring water of alpine karst aquifers. Furthermore, our research indicates that at least a significant fraction of the observed microbes are indigenous to the karstic aquifer environment itself. The so called "autochthonous microbial endokarst communities" in the spring water are likely to originate from sloughed cells attached to the rock surfaces and deposited sediments in the aquifer or occur simply suspended in low - flow interstitial areas. The question arises about the consequences of these microbial communities? Are they simply a passive collection of living organic matter or do they constitute a giant active bioreactor in the karst aquifer with all its ecological consequences? The proposed study will set the first crucial steps in evaluating the relevance of microbial metabolism in alpine karstic spring water and respective biofilm compartments. Results are of high interest for a better understanding of basic alpine karstic groundwater ecology (e.g. organic matter cycling, deep phreatic karstification) as well as for public water provision issues (e.g. self purification capacity of karstic aquifers, biological stability and quality of abstracted spring water). The proposal focus on the investigation on prokaryotic activity as it is considered the catalytic driving force of dark - heterotrophic processes. As outlined in the proposal, the applying research group already successfully adapted sensitive state of the art techniques for the determination of prokaryotic activity and community structure in spring water during a one years EU funded collaboration in 2003 to 2004 with the Netherlands Institute for Sea Research. For the first time it will become possible to link prokaryotic community composition, active cell compartments and total community production in spring water and respective biofilm compartments by means of catalysed reporter deposition fluorescence in situ hybridisation (CARD-FISH), microautoradiography (MAR) and in situ prokaryotic production measurements (3H- Leu incorporation). Furthermore by using "on-line" hydrological and chemographical information of the respective spring catchment itself, evaluation of the significance of prokaryotic activity for karst aquifer ecology and biogeochemical processes can be undertaken. Because alpine karstic aquifers, especially the saturated zones, are not directly accessible the investigation will be based at spring locations investigating spring water as well as corresponding re suspended sediments and their attached biofilms by permanently installed sediment traps. Thus, an evaluation of the significance of attached vs. suspended prokaryotes will become possible. A seasonal variation analysis covering three summer and two winter seasons and additionally two flood investigations will be undertaken. The selected "model" alpine catchment areas of the DKAS1 and LKAS2 spring have already proved an excellent setup in previous studies. It should be mentioned that this research involves the close cooperation of microbial ecologists, hydrologists and public water works.