Biodiversity is the object of a large international programme of the IUBS-SCOPE-UNESCO and is important for many scientific, economic and ethic reasons (Solbrig, 1992). In groundwater, the study of biodiversity can be considered as a promising research field (Marmonier et al, 1993). Five major topics were discussed:

1. the importance of groundwater/surface water ecotone fauna in the estimation of global diversity;

2. the local and regional biodiversity;

3. factors promoting biodiversity;

4. biodiversity in gradients and impact of disturbances;

5. how to preserve biodiversity.

IMPORTANCE OF GROUNDWATER/SURFACE WATER ECOTONE FAUNA IN THE ESTIMATION OF GLOBAL DIVERSITY

Groundwater fauna is largely ignored in the calculation of global biodiversity. The number of species of tropical rain forests is estimated to be 10 or 20 times higher than those known to science (Cairns, 1988). Groundwater diversity is less well known than the diversity of surficial species in tropical forests globally: the total biodiversity of groundwater fauna is certainly higher than current estimations (in the Stygofauna Mundi, for example – Botosaneanu, 1986) and these organisms may represent an important part of the global biodiversity.

This is greatly important if groundwater fauna play an active role in groundwater system functioning (Fig. 1). It is especially true for microbes (microfauna, bacteria, fungi) which are still more or less unknown and may play an important role in the bank filtration of large rivers (the River Rhine for example is rather well studied from this point of view).