About faunal life in Austrian aquifers - historical background and current developments

In Austria all general types of aquifers (porous, karstic and fractured) are present and are subject of hydraulic and hydrochemical in- vestigations. However, in hydrogeological research it is a still widely neglected fact that groundwater flow is not only a flux of water, chemicals and heat within lithological units but that groundwater bodies may also act as habitats with very particular conditions for their inhabitants. In general groundwater inhabitants require three things: a place to live, oxygen and energy or food, respectively. Thus, the living conditions of groundwater animals are directly connected to hydrological and geomorphological conditions on a regional scale, and on a local scale, lithological and structural properties that control hydrogeological parameters such as porosity and hydraulic conductivity, recharge mechanisms and flow dynamics. In this paper we view Austrian hydrogeology from the perspective of groundwater fauna in order to elucidate the connection between the hydrogeological conditions and biological patterns. A brief review of groundwater biology research in general and spe- cifically in Austria, revealed that crustaceans are basically in the focus of groundwater research while other common groundwater dwellers, such as free-living nematodes, are less studied similarly. Porous aquifers are comparably well investigated by groundwater biologists, while fractured aquifers have rarely been considered as habitats to date. Due to the complex hydrogeological situation in Austria, with a greater portion of fractured and karstic aquifers, a systematic biological survey considering hydrogeological aspects may lead to a pronounced progress for the both disciplines, hydrogeology and groundwater biology. For hydrogeological purposes, the studies may provide the basis for using groundwater species (similar to the established method of using stable isotopes) as natural tracers in future studies. From the biological perspective, progress in the understanding of complex habitat-biota relations is expected to result from the investigation of hitherto unknown habitats. In addition, such a survey would not only be an important contribution to biodiversity and biogeography in Austria, it would also pro- mote groundwater research in a broader context, such as the need to protect groundwater as a valuable service providing system (e.g. water quality). Preliminary results from six test sites distributed to four different geological settings (Quaternary basin fill, Flysch-Zone, Northern Calcareous Alps and the Central Crystalline Zone within the Alps) show evidence for a link between the hydrogeological conditions and the present biological assemblages. However, a systematic survey is still required to understand which environmental factors mainly govern live in Austrian aquifers.