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Abstract: The species-specific mobility of six species of lowland stream Trichoptera was studied in flume experiments with different habitats and current flows. The test species were selected according to their occurrence along the environmental gradient from more natural towards highly disturbed sandy, lowland streams of the North-West European plain. Two groups of species were distinguished, three species occurring more frequently towards the natural end versus three occurring more frequently towards the disturbed end of the stream disturbance gradient. Experiments were conducted in a temperature and light controlled environment in indoor, re-circulating, man-made stream channels with four replicate gutters each. The bottom of each gutter held ten trays filled with five selected habitat materials (two trays each), which provided refugia and food. Three flow treatments with constant current velocities of 10, 30, or 50cm/s were applied. Movements were scored based on visual observations of the position of each individual at fixed time points. The first day after release, individuals moved around very actively; this ‘release effect’ was removed from further analyses. The trichopteran species occurring near the more natural end of the disturbance gradient exhibited significantly less mobility (on average 10–15% of individuals actively moved around) than the species from the more disturbed end of the gradient (on average 30–40% of individuals actively moved around). The first group of trichopteran species also spent significantly longer times in the leaves habitat compared to the other three species, which moved more or less independent of habitat. With increasing current velocity, all test species moved more frequently, particularly the species from the more disturbed end of the gradient. This could indicate behavior to avoid dislodgement. The mobility of all species exceeded the mobility needed to use habitat resources of food and shelter, both present in excess. Therefore, short-term movement could also be (partly) a random behavior. Overall, the more tolerant species from the disturbed end of the gradient showed more mobility and flexibility than the species occurring under more or less natural stream conditions. This was consistent with the hypothesis that mobility is an adaptation of tolerant, ubiquitous species. Mobility is an adaptation of r-strategists. [Copyright &y& Elsevier]

Abstract: Freshwater diatoms are considered to be reliable indicators of the trophic status of rivers and lakes. In the past 30 years, a number of indicator indices have been developed and used for the assessment of trophic conditions all over Europe. It is however still not clear whether the ecologic signature of diatoms differs between these indicator indices. The present study assessed a large number of published European indices on the response of freshwater diatoms to trophic conditions by evaluating the consistency in the use of taxa and their trophic score from seven European indicator indices. The STAR (Standardisations of River Classifications) diatom database, a large set of samples from European running waters, was used to test the application of trophic classifications in water quality assessment. The analysis of taxa in common within the trophic indices showed that there are considerable differences between the indices, for example in the score of trophic values. There was more agreement in classification of taxa within the oligotrophic and the hypertrophic preferences than within the mesotrophic range. Based on these results, a list of diatom taxa, that are consistently used in different trophic indices, was composed. It included 159 ‘reliable’ taxa that are not sensitive to regional setting, water type and taxonomic uncertainty. The list was further accompanied by a description of the taxa''s trophic preferences. The large deviation in trophic scores for a number of diatom taxa could most probably be explained by taxonomic uncertainties. Application of these taxa for trophic assessment was questionable. The test set of the 359 STAR samples showed that differences between the trophic indices also lead to a significant variation in the water quality assessment results. Although trophic indices provide an excellent biomonitoring tool, they should be applied with caution, considering the recommendations provided in this paper. [Copyright &y& Elsevier]