Hard rock aquifers and free‐living nematodes – an interdisciplinary approach based on two widely neglected components in groundwater research

Abstract

The subterranean part of the water cycle takes place in three different types of groundwater bodies: (1) unconsolidated sediments, (2) karstic aquifers and (3) fractured hard rock aquifers. Basically, different aquifer types require different investigation methods. However, the physico‐chemical properties of groundwater can aid in the understanding of flow history and aquifer dynamics of each aquifer type. Although groundwater biology is sensitive to hydrochemistry, water temperature and flow velocity, the possible benefits of groundwater animals as ‘hydrogeological agents’ is still rarely considered by hydrogeologists. The main research focus of hydrogeologists and groundwater biologists is shallow groundwater bodies in unconsolidated sediments and karst aquifers. Fractured hard rock aquifers are still poorly considered by both disciplines. This commentary has three purposes: (1) to show the special characteristics of fractured hard rock aquifers in comparison to porous and karst groundwater bodies, and to describe the resulting methological gap hydrogeologists face when investigating such aquifer types; (2) to give an overview of current groundwater biological research with its focuses and shortcomings, including an introduction of rarely known but common groundwater inhabitants, namely free‐living nematodes; and (3) to suggest a combination of methods, supported by a hypothetical example, and the possible benefits this combined knowledge from hydrogeologists and groundwater biologists can bring to both disciplines. Copyright © 2014 John Wiley & Sons, Ltd.

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

“…Furthermore, groundwater biology focuses on karstic and porous aquifer types and show a lack of attention towards organisms living in fractured aquifers as pointed out recently (Eisendle-Flöckner and Hilberg, 2014). This is also an imbalance concerning the investigated biogeographic regions.…”

“…As a heterogeneous geology and climate stands for highly variable subsurface living conditions, life in Austria's subsurface must also be of a high variability. Thus, from the hydro geological point of view groundwater animals, as an important component of underground life, may be ideal natural tracers for distinct hydrogeological situations (Eisendle-Flöckner and Hilberg, 2014). Consequently, a systematic survey of Austria´s groundwater inhabitants is considered to provide a basis for integrating ecohydrology into the research of complex hydrogeological settings.…”

Preface to the special section “Biohydrology ‐ Water for life”

“…Especially land‐water interactions and the role of biological populations in cross‐system relationships are emerging areas for interdisciplinary research (Eisendle‐Flöckner and Hilberg, ; Nowicki et al , ; Richardson and Sato, ). The contribution of Richardson and Sato () reviews the role of resource subsidies in terms of aquatic insect biomass for terrestrial populations and presents open research questions.…”

“…The topic of land‐water interactions also includes the impact of land use on groundwater biology. In this emerging field, Eisendle‐Flöckner and Hilberg () suggest an innovative combination of methods and point to the lack of knowledge on the groundwater fauna of fractured hard rocks as well as the relevance of nematodes as potential biological indicators in such environments.…”

Towards an integrated understanding of how micro scale processes shape groundwater ecosystem functions

“…This is not to deny the importance of crystalline aquifers (compare e.g. Johns et al, 2014) or karst (Goldscheider et al, 2006;Humphreys, 2006), but knowledge is still too patchy (Eisendle-Flöckner and Hilberg, 2015) on such aquifers to make generalized assumptions. General knowledge on unconsolidated sediments aquifers, in contrast, has been reviewed in Boulton et al (1998); Boulton and Hancock (2006); Gibert et al (1994); Griebler and Avramov (2015); Jones and Mulholland (2000); Schmidt and Hahn (2012); Wilkens et al (2000), and, the most comprehensive compilation to-date, by Griebler and Mösslacher (2003a) as well as the focused recent volume by Brendelberger et al (2015), the latter two in German though.…”