a b s t r a c tSampling efficiency is directly linked to (faunistic) stability issues of any sampled site. It is more probable to sample a high proportion of the species occurring at a certain site, if communities remain constant in species composition with time. For this study 64 groundwater monitoring wells in Southwestern Germany were sampled six times to determine sampling efficiency. False-Negative (FN) rates and SIMPER values, two independent models expressing Faunistic values of the sampled bores, were calculated and three groups of faunistic stability could be identified based on calculated SIMPER-values. FN-rates as well as SIMPER values proved to be a valuable approach for the estimation of faunistic stability/instability, as these methods showed a highly negative correlation with each other. To collect 95% of species a number of 1.7-16.4 samples was calculated to be necessary depending on faunistic stability of the sampled habitat. On the six sampling occasions the sites harbouring a stable groundwater meiofauna resulted in 98.2% of occurring species, whereas the percentage decreased over intermediate sites (94.9%) and stressed sites (79.5%).A consequence of the data presented may be to view surveys using only two samples as campaign with orienting character, with further studies of stability issues of groundwater communities which would provide efficient and effective sampling for various kinds of sites.

Distribution of groundwater invertebrate communities in porous aquifers (and their habitats) varies on spatial scales and many attempts have been made to classify these on various scales. The new data-based approach, presented here, classifies the complex distribution of groundwater habitats on a local scale (i.e. along transects of < 100 m) and merges the latest classification approaches at this scale. Data from a regional (i.e. approximately 100 km 2) biogeographic groundwater survey was analysed in terms of stability of: community structure, different intensities of surface water influence, and occurrence, together with the distribution of stygobites within those groundwater ecosystems. On the investigated local scale, the faunistic communities' composition is mainly depending on surface water influence, coupled with immi-sion of dissolved oxygen and organic matter. Derived from this finding, five types of faunistic habitats are proposed: (I) Stressed groundwater habitats, (II) Stable groundwater habitats, (III) Rain fed groundwater habitats , (IV) Surface water fed groundwater habitats, and (V) Hyporheic habitats.

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