The special hydrological situation of temporary streams has a great influence on the abiotic processes and other habitat conditions for organisms. To monitor possible impacts of stream drying on the composition of lotic communities, streamflow measurements and collections of the macrozoobenthos were conducted in a temporary and an adjacent upstream permanent section of the karst stream Sauer (East Westphalia, Germany) in 1996. The Sauer has a summer-dry temporary flow regime. The seasonal dry phase can last from spring to early autumn, so the duration of the dry phase varies from one to several months, increasing with distance downstream from the upstream permanent section. The number of invertebrate taxa and individuals decreases with increasing duration of the dry phase. The permanent section is characterized by taxa typical of montane and submontane streams, whereas the fauna of the temporary section is quite different, composed of representatives of various zonal areas. Limnephilid caddisflies are particularly characteristic of this section. Life cycle strategies and specific adaptations with respect to habitat drying are discussed for several species. It can be concluded that the temporary discharge regime of the karst stream Sauer has a clear effect on the invertebrate communities. They mainly consist of species which can be seen as characteristic faunal elements of temporary streams.

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We found the alien amphipod, Echinogammarus berilloni (Catta, 1878) in a temporary karstic stream system (Westphalia, Germany). We investigated the effect of the seasonal low flow and desiccation on the distribution and the relative abundance of E. berilloni and on the native amphipods, Gammarus fossarum Koch, 1835 and G. pulex (Linnaeus, 1758). E. berilloni does not colonize the headwaters of the study area. Due to the seasonal low flow situation or even stream drying, this longitudinal limit of distribution can already occur in a further downstream section. After total drying the recolonization of E. berilloni in the temporary stream section mainly happens by drift from the permanent upstream sections, if a population has been established there. The relative abundance of E. berilloni and of the native amphipods, G. pulex and G. fossarum within the temporary stream sections is highly correlated with the temporary discharge regime. While in the permanent downstream sections E. berilloni successfully competes with the native gammarids and almost completely replaces them, Gammarus spp. dominate in the temporary reaches. ZUSAMMENFASSUNGDer Neozoe Echinogammarus berilloni (Catta, 1878) konnte in einem verkarsteten temporären Fließgewässer-System (Westfalen, Deutschland) nachgewiesen werden. Wir untersuchten den Einfluss von Austrocknung und Niedrigwasser auf die Verbreitung und relative Abundanz von E. berilloni und der heimischen Amphipoden, Gammarus fossarum Koch, 1835 und G. pulex (Linnaeus, 1758). E. berilloni besiedelt nicht die Oberläufe des Untersuchungsgebietes. Diese längszonale Verbreitungsgrenze kann durch die saisonale Austrocknung oder Niedrigwassersituation bereits in einem unteren Gewässerabschnitt auftreten. Nach einer totalen Austrocknung erfolgt die Wiederbesiedlung der temporären Gewässerabschnitte durch E. berilloni hauptsächlich per Drift aus den permanenten Abschnitten im Oberlauf der Karstgewässer, wenn dort eine Population vorhanden ist. Die relative Abundanz von E. berilloni und der heimischen Amphipoden, G. pulex und G. fossarum korreliert stark mit dem temporären Abflussregime. Während in den permanenten Gewässerabschnitten 1 )

We studied the effect of carbonate depositions covering stone surfaces on the growth of larvae and the biomass of subsequent adults of the grazing limnephilid caddisfly Melampophylax mucoreus (HAGEN, 1861) in a laboratory rearing experiment. M. mucoreus is mainly distributed in karst streams characterized by calcium carbonate precipitations (tufa). We reared larvae of M. mucoreus on stones covered by calcareous tufa crusts as well as on stones from which these crusts were experimentally removed to assess the influence on larval growth and the subsequent adult biomass. The rough surface of the covered stones provided a higher complexity of micro-habitats and supported algal growth compared to the smooth surface of stones without crusts. Larvae of M. mucoreus profited from the enhanced algal biofilm growth on the calcium carbonate precipitation indicated by faster larval growth and higher subsequent adult biomass. Biomass increase of larvae reared on stones covered by tufa crusts exhibited a faster biomass development (0.09 ± 0.015 mg/d) compared to the larvae reared on stones without crusts (0.06 ± 0.002 mg/d). Adult males (5.13 ± 0.25 mg) and females (7.64 ± 0.63 mg) were significantly heavier in the treatment with stones covered by tufa than their conspecifics from the treatment with uncovered stones (males: 4.26 ± 0.25 mg, p = 0.047; females: 4.96 ± 0.47 mg, p = 0.001). Additionally, males from the treatment with crust covered stones emerged significantly earlier (p = 0.003) than the males from the other treatment, whereas no significant difference was found for females. IntroductionCalcareous deposition on surfaces of submerged substrates is a typical phenomenon in spring-fed and groundwater dominated karst streams (DRYSDALE, 2001). The precipitation of calcium carbonate can build up considerable tufa crusts of several centimetres covering all present substrates, sometimes even leaves, caddisflies cases and mussel shells. Carbonate tufa streams, particularly small spring brooks are a characteristic type of karstic stream systems, often characterised by a temporary discharge regime (MEYER et al., 2003). The precipitation of calcium carbonate can be increased in carbonate-rich streams during periods of low flow (SZRAMEK and WALTER, 2004).Few effects of tufa crusts on the benthos in streams have been described, such as reduction of gammarid mortality caused by fish predators due to protective tufa deposits on the gammarid body surface (RUFF and MAIER, 2000) or increasing ciliate species diversity and higher periphyton biomass associated to increasing rate of tufa precipitation (PRIMC-HABDI- JA et al., 2001). On the other hand, animal activities can also promote tufa development in Internat. Rev. Hydrobiol.

Abstract.  The behaviour of larvae of Melampophylax mucoreus (Limnephilidae; Trichoptera) is studied to test their capacity for food detection over long distances by olfaction. In aquaria experiments with stagnant water, the larvae rapidly accumulate on a biofilm‐covered stone (offered food patch) but not on control stones without biofilm‐cover. Larvae in an artificial flow channel (flume), with uni‐directional flow between an arrangement of stones covered with biofilm and stones without biofilm, can find food patches upstream from their location more rapidly than downstream. Stimuli transported towards the larvae by the water current might assist food location. However, no significant differences could be found in the movement of larvae with intact antennae compared with larvae without antennae. The results lead to the conclusion that the larvae of M. mucoreus find food patches mainly by random movement, which is assisted by their high mobility. Long‐distance olfactory orientation towards food patches, mediated by antennae, can be precluded. Gustatory stimuli appear to play an important role in contact‐chemoreception to identify biofilm patches on stone surfaces. Scanning electron microscopy studies of the larval head reveal that the antennae of M. mucoreus are small pegs (50 µm in length) with an apical plate (15 µm in diameter). The mouthparts of the larvae, especially the maxillary palps, show a variety of different sensilla types that are possibly used for contact‐chemoreception. These sensilla also could be responsible for the orientation towards a food resource upstream of the larvae.