Biodiversity of Belgian groundwater fauna in relation to environmental conditions

Abstract

SUMMARY1. The Pleistocene glaciations during the Quaternary appear to have resulted in an impoverished groundwater fauna in northern Europe. Re-colonisation may have occurred either through long-distance dispersal from unglaciated southern areas or from local refugia. 2. The Belgian groundwater fauna was sampled at multiple sites, and its habitats characterised, to assess whether the composition of present-day stygobiotic assemblages can be attributed to either of these mechanisms. 3. A total of 202 sampling sites were selected in four hydrogeographic units of the Meuse River catchment. Sites were equally divided among the saturated and unsaturated zones of fractured aquifers (karst) and within the hyporheic and phreatic zones of porous aquifers. Seventeen environmental parameters were determined in parallel. 4. More than 140 species were recorded, including representatives of the Amphipoda, Cladocera, Copepoda, Hydrachnidia, Isopoda, Oligochaeta, Ostracoda, Mollusca, Syncarida and Nematoda. Thirty stygobiont species were identified, of which 10 species were new to the Belgian fauna, raising the total number of stygobiotic species in Belgium to 41. 5. The frequency of occurrences of stygobiotic species was always low, with 37% of the sampled sites lacking stygobionts. A few species were exclusive to one hydrological zone, although no statistically significant differences were detected in species richness at any of the four hierarchial levels considered (Meuse catchment = region, hydrogeographic units, aquifer type and hydrological zone). 6. Overall, results suggest that the stygobiotic fauna of Belgium is species-poor and mostly comprises widely distributed species with broad ecological tolerances. This supports the view that eurytopic species re-colonised the area by long-distance dispersal from refugia in southern Europe. The virtual absence of endemic species further suggests that the scenario of an ancient fauna that survived in local refugia is of minor importance.

La ecología de invertebrados del acuífero Chalk en Inglaterra (UK)

“…Given that individual boreholes are just point samples in a potentially extensive habitat, and that previous studies (in other geologies) have suggested that multiple sampling occasions are often required to detect species in boreholes (Allford et al 2008;Eberhard et al 2009;Hancock and Boulton 2009), it is remarkable that 67 % of our borehole samples detected stygobitic invertebrates on just a single sampling occasion. It is clear that the Chalk represents an important and widespread habitat for groundwater adapted invertebrates in England, and is likely to do so throughout Europe, where similar hydrogeological conditions exist (Downing et al 2005), and fauna have been previously recorded Martin et al 2009;Michel et al 2009). …”

“…However, in general, groundwater ecosystems are not considered in water management programs. Nevertheless the Chalk aquifer has been identified as a habitat for invertebrate groundwater fauna in England (Proudlove et al 2003;Robertson et al 2009;Sorensen et al 2013;Johns et al 2015), and fauna are recorded from Chalk areas in continental Europe Martin et al 2009;Michel et al 2009); however, it is unclear in some of these studies which samples came from the Chalk, and questions remain about where in the aquifer invertebrates occur, and how commonly they occur. The prevalence of species in the Chalk and the importance of the Chalk as an ecological habitat have not been properly assessed.…”

Stygobiotic crustacean species richness: a question of numbers, a matter of scale

“…Gibert & Deharveng, 2002;Castellarini et al, 2005;Galassi et al, 2009b;Martin et al, 2009) give rise to groundwater biodiversity patterns, how they interact is far from being known. Until now, spatial patterns of groundwater biodiversity have been basically interpreted under an ecological perspective.…”

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

“…The few taxa found with higher abundances such as Acanthocylops robustus, A. sensitivus Diacyclops languidoides (table 5 -supplementary data) but also the more rarely found isopod [Proasellus coxalis Proasselus cavaticus) and amphipod [Crangonyx subterraneus] taxa are basically widespread and commonly found throughout Austria but also Europe (e.g. Gaviria 1998;Danielopol and Pospisil, 2001;Fuchs et al, 2006;Kaiser, 2005;Hahn and Fuchs, 2009;Martin et al, 2009). Comprehensive aquifer studies including other nematode data than their total numbers or relative portions are to our present knowledge not existent, but abundances of total nematode fauna can be relatively high in both alluvial and fissured aquifer types compared to other faunal elements (Fuchs et al, 2006).…”