| Abstract: | Among terrestrial biomes the groundwater domain is generally considered to be a species poor environment. This view results, mainly, from the large geographic scale faunistic surveys (tens and hundreds of kilometres) and the traditionally coarse spatial scale (i.e. macroscale level) of ecological analysis. This view has been challenged by Margalef (1993) who suggests that high diversities are to be expected in the subterranean environment comparable to those found in the deep sea because of environmental similarities, e.g. low energetic resources. During the last twenty years long-term ecological research on much smaller scales, i.e. metres to hundred metres for interstitial media, a mesoscale approach, or kilometre size for karst systems was carried on. Long-term projects on limnic subsurface systems have shown that the species richness (SR) of the microcrustacea (Harpacticoida, Cyclopopoida, Ostracoda) is much higher than previously considered. Details on Harpacticoida of the alluvial bedsediments of a Pyreneean brook, the Lachein, and on Ostracoda of the alluvial sediments of the Danube plain (the phreatic zone), near Vienna, are presented. The SR values of the interstitial microcrustacea obtained through investigations at a mesoscale level are comparable to those of karstic and/or surface freshwater benthic water systems; they are lower than those of the deep-sea data sets for equivalent crustacean groups at a similar scale of investigation. From the data presented we infer the following points: (a) The subterranean waters are much more rich in species than earlier accepted, at least for some organismic groups like the microcrustacean copepods and ostracods. (b) Hence, to describe the still unknown fauna it is appropriate to sample the subsurface waters at an ecological scale. (c) Only studies during long-term ecological projects and with intensive, quantitative, sampling programmes allow a correct evaluation of the subterranean faunal diversity. (d) The species richness of a given subsurface site is strongly dependent on the structure of the habitats and the functioning of the underlying ecosystems. (e) Finally we consider the rationale for the protection of the subterranean faunal diversity. |
