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.

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Unbaited phreatic traps are a promising new method for sampling subterranean limnofauna. The aim of this study is to evaluate whether such trap systems are suitable to gather representative samples of the physico-chemical parameters and the invertebrate fauna of the aquifer. Fifteen traps, installed in five groundwater bores, and four traps located in the hyporheic zone, were sampled twice monthly over a 1 year period (June 2003-June 2004). Water samples were removed in three separated fractions (hose, trap and aquifer water), analysed for physico-chemical and faunal characteristics and compared with one another. The study was carried out in the Nakdong River floodplain, Korea. Physico-chemical characteristics of trap and aquifer were similar, but differed greatly from the hose samples. Abundances of fauna inside the traps were higher than in the aquifer, whereas there were no differences in taxonomic composition of the trap and aquifer samples. Biases of abundances suspected due to the use of traps were negligible in the groundwater, though it is recommended that comparisons between groundwater and hyporheic abundances ascertained by traps be handled cautiously.

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