Distribution patterns of groundwater communities across aquifer types in south‐western Germany

Abstract

SUMMARY1. Classification of groundwater habitats and communities at different spatial scales is emphasised as a basic requirement for the implementation of groundwater ecology into legislation. Such a classification would also facilitate prediction of groundwater biodiversity, abundance and community structure, but is not currently available. 2. To identify the factors influencing the distribution of stygofauna at the landscape scale, the groundwater fauna of Baden-Wü rttemberg in South-western Germany was sampled from November 2001 to December 2002. A total of 304 boreholes were sampled twice with a phreatic net. Boreholes were originally selected to represent the full range of geographic, geological and hydrographic variation within the sampling area. However, bores in porous aquifers were overrepresented because the monitoring networks that could be used in this study were originally designed for hydrogeological purposes. 3. In total, 105 taxa (including 60 stygobionts) were found. Most of the stygobionts were rare, with 52% of them occurring in less than 1% of the boreholes. Stygobiotic taxonomic richness in a region or so-called geological unit was directly correlated with the number of bores sampled. Species richness accumulation curves indicated that the real taxonomic richness of Baden-Wü rttemberg is considerably higher than the recorded number of 60 stygobiotic taxa. This finding is in accordance with studies from other regions and suggests that groundwater biodiversity generally is strongly underestimated, probably resulting mainly from huge heterogeneity of groundwater systems and reliance on broad-scale hydrological monitoring networks. 4. To identify regional distribution patterns, the sampling area was separated into regional geological units, each comprising all aquifers of identical geology in a particular region (size: hundred to several thousand square kilometres). Distribution patterns of the aquatic subterranean fauna (including non-stygobionts) were found to be influenced to some degree by the geographical position of the bores, and to a large extent by hydrogeological aquifer type rather than by affiliation of aquifers to a given geological unit. Four types of aquifers could be distinguished: Compact aquifers (aquitards) with reduced pore spaces, and porous, fractured and karstic aquifers. 5. Communities of porous and karstic aquifers were found to be more similar to each other than the communities of compact and fractured aquifers. Therefore, for the purpose of recording groundwater biodiversity and defining undisturbed groundwater habitats, we suggest focusing more strongly than in the past on aquifer hydraulic conductivity and, in particular, on compact and fractured aquifers.

Differences between groundwater fauna in shallow and in deep intergranular aquifers as an indication of different characteristics of habitats and hydraulic connections

“…Few groundwater studies on invertebrates have sampled numerous sites or samplings on the same place have been frequent (Karanovic, 2006;Hahn and Fuchs, 2009;Galassi et al, 2009b). When one sampling event on several sites in a given area has been done, it usually resulted in low α-diversity at the local spatial scale (i.e., the single well) but high γ-diversity on a regional scale has been observed (Gibert, 2001;Stoch and Galassi, 2010).…”

“…Air-lift pumps can be utilised in deep boreholes (Malard et al, 1994) but, for effective collection, a high-capacity, compact air-compressor is required. In consequence, sampling of fauna in intergranular aquifers has rarely been carried out at depths exceeding 20 to 30 m (Datry et al, 2005;Bork et al, 2008;Hahn and Fuchs, 2009).…”

“…However, fauna from deeper boreholes and piezometers can be collected from open boreholes (i.e. boreholes without installed pumps) using the Cvetkov net or modified plankton nets/phreatic nets (Malard et al, 2002;Karanovic, 2006;Schmidt et al, 2007;Eberhard et al, 2009;Hahn and Fuchs, 2009). Air-lift pumps can be utilised in deep boreholes (Malard et al, 1994) but, for effective collection, a high-capacity, compact air-compressor is required.…”

“…Although these numbers appear large, most records are based on a single sampling at single locations and sporadic sampling over long time intervals. This situation has changed over the last three decades, as groundwater ecology research has intensified Schmidt et al, 2007;Gibert and Culver, 2009;Hahn and Fuchs, 2009;Larned, 2012). Ecological studies of groundwater ecosystems, in intergranular aquifers in particular, developed rapidly during the 1990's (Gibert et al, 1990;Danielopol et al, 2001;Gibert, 2001;Gibert and Deharveng, 2002;Hancock et al, 2005;Danielopol and Griebler, 2008).…”

Differences in aquatic microcrustacean assemblages between temporary and perennial springs of an alpine karstic aquifer

“…Fauna of the epikarst and vadose zone is mostly investigated directly by entering the caves and less often by applying boreholes or monitoring wells (Malard et al, 1996;Hahn and Fuchs, 2009), filtering water at karstic outlets (i.e. collecting invertebrate drift) (Leruth, 1939;Rouch, 1968;Rouch et al, 1968;Gibert, 1986;Vervier and Gibert, 1991) or sampling the benthos in the karstic springs .…”