1. Relating processes occurring at a local scale to the natural variability of ecosystems at a larger scale requires the design of predictive models both to orientate stream management and to predict the effects of larger scale disturbances such as climate changes. Our study contributes to this effort by providing detailed models of the hydraulic preferences of 151 invertebrate taxa, mostly identified at the species level. We used an extensive data set comprising 580 invertebrate samples collected using a Surber net from nine sites of second and third order streams during one, two or three surveys at each site. We used nested nonlinear mixed models to relate taxon local densities to bed shear stresses estimated from FliesswasserStammTisch hemisphere numbers.2. An average model by taxon, i.e. independent from surveys, globally explained 25% of the density variations of taxa within surveys. A quadratic relationship existed between the average preferences and the niche breadth of taxa, indicating that taxa preferring extreme hemisphere numbers had a reduced hydraulic niche breadth. A more complete model, where taxa preferences vary across surveys, globally explained 38% of the variation of taxa densities within surveys. Variations in preferences across surveys were weak for taxa preferring extreme hemisphere numbers. 3. There was a significant taxonomic effect on preferences computed from the complete model. By contrast, season, site, average hemisphere number within a survey and average density of taxa within a survey used as covariates did not consistently explain shifts in taxon hydraulic preferences across surveys. 4. The average hydraulic preferences of taxa obtained from the extensive data set were well correlated to those obtained from two additional independent data sets collected in other regions. The consistency of taxon preferences across regions supports the use of regional preference curves for estimating the impact of river management on invertebrate communities. By contrast, the hydraulic niche breadths of taxa computed from the different data sets were not related.

Measuring and especially modeling the spatial and temporal variability of local bottom shear stress in streams are major issues in concepts of hydraulic engineering and lotic ecology and becomes very complicated with increasing channel complexity and/or decreasing channel size. Using Fliesswasserstammtisch (FST) hemispheres, an unconventional method for near-bottom flow measurements, we determined the parameters of shear stress frequency distributions of German mountainous streams by a maximum likelihood procedure. The resulting model is robust and generates information on the spatial and temporal variability of local shear stress in stream segments from easily obtained input variables (discharge, mean stream width and depth).

Despite increasing knowledge of the ability of keystone animal species (“ecosystem engineers”) to change their physical environment, there is little and inconsistent evidence that benthic invertebrates affect the erosion of bottom material in streams. Therefore we designed field stream experiments and observations to investigate the effect of mobile predaceous stonefly (Dinocras cephalotes) larvae on sand erosion. When short of prey, the stoneflies erode sand from stream riffles thereby deepening the interstices between cobbles. On the basis of reasonable assumptions, we speculate that Dinocras has an erosion potential of about 200–400 kg sand m−2 yr−1 at natural population densities under favorable flow conditions. We consider the possible implications of the bioturbation potential of stream invertebrates for ecology (habitat quality and disturbance) and hydrology (sand transport and stability of coarse stream bottoms), which call for joint research on this novel role invertebrates play in the functioning of stream ecosystems.

German politicians have promised that the River Rhine will be sufficiently restored within twelve years to permit salmon to live there again. Obviously the large rivers in Central Europe are more isolated from each other than smaller streams, and communities donating potential colonizers (if they exist at all) are further apart for possibly restored large rivers than for smaller streams. Thus, recovery can be expected to be faster in small streams than in big rivers after restoration (or reduction of detrimental human influence). Therefore, two restoration projects in German lowland streams, which differ in their degree of isolation, can serve as an indicator to the time periods which could at least be expected for the recovery of Central European rivers.Under optimal conditions (almost completely intact communities upstream and downstream of a 400 m restored reach) in North Germany, sufficient recovery of benthic macroinvertebrate fauna could be achieved in relatively short periods. However, in a rather isolated stream reach in the Upper Rhine valley (closest intact lotic ecosystems of a comparable type were found 20-25 km away) a sufficient recovery of benthic macroinvertebrate fauna was not achieved within five years after restoration, although there was high diversity of physical habitats and the water quality was acceptable (except for two oil accidents in the fourth and the fifth year).Hence, we conclude that recovery of a large Central European river ecosystem like the Rhine, which has lost a large number of its former species and is more isolated than small streams, will require more than twelve years to reach a state significantly different from the present one.

Macrozoobenthos (especially gastropods) abundance data have been used to ordinate sampling stations on two floodplains of the Upper Rhine with different hydraulic regimes: 30 species of gastropods were recorded in the area actively inundated by the Rhine, while backwaters that have not been flooded for over 50 years housed only 19 species.Potamopyrgus antipodarum is a characteristic species of the permanent aquatic biotopes fed by groundwater and connected with other floodplain waters. Small, isolated, and drying-up former lateral channels and pools, slowly inundated during a flood, are characterized by Planorbis planorbis with Bathyomphalus contortus. Gyralus albus and Vuluata cristata are characteristic of small, partly isolated, and partly drying-up water bodies of the active floodplain, which are inundated rapidly and very turbulently during the flood. Due to restricted hydrological dynamics the waterbodies of the former floodplain were mainly inhabited by ubiquitous species.