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Detailed information on species temperature preferences are needed to measure the effects of global warming on species and communities in European rivers. However, information currently available in the literature on taxon-specific temperature preferences or temperature tolerances is very heterogeneous and therefore not well suited for forecasting purposes. To close this gap, we derived so-called 'central temperature tendencies' (CTT t values) for benthic invertebrate species. For this end, 547 species and temperature data from regional monitoring programmes in Germany collected at 4249 sites were analysed. Due to the vulnerability of species to high temperatures, CTT t values were calculated for mean summer temperatures, following a robust approach of calculating a weighted average based on temperature classes. Derived CTT t values correspond well to species temperature preferences as reported in literature as long as the latter were homogeneous in terms of how they were derived and which temperature reference was at focus. Based on taxon-specific CTT t values, a community value, CTT Com , was calculated for each benthic invertebrate sample. CTT Com values were validated by correlation with mean summer water temperatures. As the slope a of the linear regression model between CTT Com values and measured summer temperatures was comparatively low (a = 0.49), a correction function was derived in order to optimise the relation between both. This was crucial, because it is assumed that although CTT t was derived solely from taxa abundances within summer temperature classes, CTT Com not only reflects the effect of (summer) water temperature itself, but also corresponds to a temperature equivalent value, which describes the overall quality of all respiration-relevant aquatic summer habitat conditions that determine the metabolism of respective benthic invertebrates. By comparing this equivalent value with water temperatures measured in the year previous of sampling, statements can be made about the influence of flow conditions and other factors determining oxygen availability. Thus, CTT Com reflects the mean aerobic scope of the overall benthic invertebrate fauna: the better the respiration conditions for rheophilic species with high oxygen demand, the larger the aerobic scope and the lower CTT Com. The approach taken in our study is promising and provides a tool to track and even project past, present, and future impacts of global warming on benthic invertebrates in rivers based on measured values of respiratory relevant environmental variables. We encourage all stakeholders in the field of freshwater ecology to test this tool, which is already in use in river management practice in Germany and is known under the long or short terms KLIWA-Index MZB or KI MZB. • Temperature preferences of many aquatic benthic invertebrates are poorly known. • We calculated 'central tendency temperatures' (CTT) of 547 aquatic invertebrate taxa. • Community 'central tendency temperatures' inversely reflected the mean aerobic scope. • 'Central tendency temperatures' can be used to trace effects of global warming. [ABSTRACT FROM AUTHOR]

Aim Highly complex interactions between the hydrosphere and biosphere, as well as multifactorial relationships, characterize the interconnecting role of streams and rivers between different elements of a landscape. Applying species distribution models ( SDMs) in these ecosystems requires special attention because rivers are linear systems and their abiotic and biotic conditions are structured in a linear fashion with significant influences from upstream/downstream or lateral influences from adjacent areas. Our aim was to develop a modelling framework for benthic invertebrates in riverine ecosystems and to test our approach in a data-rich study catchment. Location We present a case study of a 9-km section of the lowland Kielstau River located in northern Germany. Methods We linked hydrological, hydraulic and species distribution models to predict the habitat suitability for the bivalve Sphaerium corneum in a riverine system. The results generated by the hydrological model served as inputs into the hydraulic model, which was used to simulate the resulting water levels, velocities and sediment discharge within the stream channel. Results The ensemble model obtained good evaluation scores (area under the receiver operating characteristic curve 0.96; kappa 0.86; true skill statistic 0.95; sensitivity 86.14; specificity 85.75). Mean values for variables at the sampling sites were not significantly different from the values at the predicted distribution ( Mann- Whitney U-test P > 0.05). High occurrence probabilities were predicted in the downstream half of the 9-km section of the Kielstau. The most important variable for the model was sediment discharge (contributing 40%), followed by water depth (30%), flow velocity (19%) and stream power (11%). Main conclusions The hydrological and hydraulic models are able to produce predictors, acting at different spatial scales, which are known to influence riverine organisms; which, in turn, are used by the SDMs as input. Our case study yielded good results, which corresponded well with ecological knowledge about our study organism. Although this method is feasible for making projections of habitat suitability on a local scale (here: a reach in a small catchment), we discuss remaining challenges for future modelling approaches and large-scale applications. [ABSTRACT FROM AUTHOR]

The Federal State of Saxony (Germany) transposed the EU Water Framework Directive into state law, identifying 617 surface water bodies (rivers and streams) for implementation of the water framework directive (WFD). Their ecological status was classified by biological quality elements (macrophytes and phytobenthos, benthic invertebrates and fish, and in large rivers, phytoplankton) and specific synthetic and non-synthetic pollutants. Hydromorphological and physico-chemical quality elements were used to identify significant anthropogenic pressures, which surface water bodies are susceptible to, and to assess the effect of these pressures on the status of surface water bodies. In 2009, the data for classification of the ecological status and the main pressures and impacts on water bodies were published in the river basin management plans (RBMP) of the Elbe and Oder rivers. To that date, only 23 (4%) streams achieved an ecological status of "good", while the rest failed to achieve the environmental objective. The two main reasons for the failure were significant alterations to the stream morphology (81% of all streams) and nutrient enrichment (62%) caused by point (industrial and municipal waste water treatment plants) and non-point (surface run-off from arable fields, discharges from urban drainages and decentralized waste water treatment plants) sources. It was anticipated that a further 55 streams would achieve the environmental objective by 2015, but the remaining 539 need extended deadlines. [ABSTRACT FROM AUTHOR]

1. We investigated the effects of local disturbance history and habitat parameters (abiotic and biotic) on the microdistribution of benthic invertebrates during several floods in two streams, the Schmiedlaine in Germany (four events) and the Kye Burn in New Zealand (two events). 2. Bed movement patterns were quantified using metal-link scour chains. Before and after each flood, quantitative invertebrate samples were taken from replicate bed patches that had experienced sediment scour, fill or remained stable. 3. Patterns of invertebrate density in the different bed stability types (i.e. scour, fill, stable) varied between floods, sampling dates and streams, but invertebrate density was highest in stable patches in >50% of all the patch type effects detected and lowest in fill patches in 75% of all detected effects. Stable bed patches acted as a refugium for Liponeura spp. and Leuctra spp. in the Schmiedlaine and for Hydracarina and Deleatidium spp. in the Kye Burn. 4. Averaged across both streams, only near-bed current velocity was correlated with invertebrate distribution on the streambed more often than disturbance history. In the Kye Burn, disturbance history and water depth were the most influential habitat parameters. 5. Our results suggest that a thorough understanding of the microdistribution of benthic invertebrates requires knowledge of disturbance history, as well as more readily measured habitat parameters such as current velocity or water depth. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this paper is twofold: 1) to validate the German stream typology for Schleswig-Holstein, and 2) to develop an assessment system for lake outlets. The German stream typology, based on a top-down analysis of geomorphological variables, was validated using biotic data of streams in Schleswig-Holstein, northern Germany. A null model analysis was conducted to test for differences between seven stream types (sand streams and rivers, gravel streams and rivers, partly-mineralic streams, limnic marsh streams, and lake outlets). The dataset compiled for the statistical analysis comprised 28 streams, 65 different sampling sites, 428 samples, and 296 taxa. The analysis confirmed all stream type except partly-mineralic streams, which showed faunal overlap with all types except gravel streams. Gravel streams were the most distinctive stream type. Lake outlets were shown to be a unique type, having a distinct macroinvertebrate fauna. Furthermore it was shown, that the species composition differed between lentic and lotic outlets. Canonical correspondence analysis of 19 investigated lake outlets revealed that characteristics of the lakes had only a minor effect on macroinvertebrate community structure. The developed assessment system of lake outlets was based on the habitat association of 132 macroinvertebrate taxa. Taxa were allotted to five categories of lake outlet preferences depending on the results from ordinations, frequency tables and abundance distributions. A qualitative and a quantitative lake outlet index (LTI) were tested with independent data sets. The quantitative LTIquan proved to be more robust and only slightly affected by seasonal changes in the macroinvertebrate community composition. Assessments of lake outlets based on macroinvertebrates should be conducted in spring and autumn to reduce the risk of misclassifications, in particular, for boundary cases rated between good and moderate quality classes. [Copyright &y& Elsevier]

The temporal distribution of the nematode fauna in the upper 5 cm sediment of the streambed of a small submountain carbonate stream (Krähenbach, Germany) was investigated over a 1-year period. The total nematode density was low during autumn and winter and reached a maximum value of 84 individuals/10 cm2 in summer. The fresh biomass of nematodes ranged from 3.6 to 44.2 μg/10 cm2. Deposit-feeders (65% of total fauna) and chewers (21%) were the two dominant feeding types. Of the 1027 nematodes examined, 9% were gravid females, 35% females, 2% males and 54% juveniles. At least 71 nematode species were identified. The relative low value of the Shannon Wiener index of diversity (2.61) is not the consequence of a low number of species, but of the presence of three species with a much higher frequency (57% of total fauna) than the others. The dominant species are Eumonhystera filiformis (Bastian, 1865)/ vulgaris (de Man, 1880), Tobrilus cf. pellucidus (Bastian, 1865) and E. simplex (de Man, 1880). The seasonal pattern of E. filiformis/vulgaris showed a minimum density in summer and a maximum density in spring and is similar to the abundance variation of all deposit-feeders. The seasonal pattern of T. cf. pellucidus showed a minimum density in winter and a maximum density in summer and is similar to the abundance variation of all chewers. Throughout the year, nematodes were found in both layers (analysed depths: 0-2 cm, 2-5 cm), but higher mean annual densities occurred in the upper layer (68% of all nematodes). The preference for the upper cm of sediment was independent of feeding-type, age structure or species. The calculation of the Maturity Index and of the ratio of Secernentea/Adenophorea indicate a 'high status' of water quality at the analysed sampling site. [ABSTRACT FROM AUTHOR]

Abstract: Blackfly communities from five German stream types out of two ecoregions (small and mid-sized siliceous gravel-bed mountain streams of the Central mountains, ecoregion 9, and organic type brooks, small and mid-sized sand-bottomed Central lowland streams of ecoregion 14) are compared. Ecoregional, as well as stream type-specific biocoenotic differences are discussed. The presence of Prosimulium sp. was restricted to mountain streams, whereas Simulium lineatum seemed to prefer mid-sized sand-bottomed Central lowland streams, and S. vernum showed a clear preference for Central lowland streams. An Index of Morphological Stress (IMS), derived from 22 geo-hydromorphological parameters recorded during sampling in the field, is presented. According to the IMS values, sites are divided into morphologically ‘unstressed’ sites (high or good morphological quality) and ‘stressed’ sites (moderate, poor or bad morphological quality), and biocoenotic differences of the two categories are discussed. Two stream types and the entire data set showed significantly higher numbers of taxa at ‘unstressed’ sites. Linear Multiple Regression (LMR) was used to identify geo-hydromorphological parameters that significantly explain the variance of the three most constant taxa, Prosimulium sp., P. hirtipes and Simulium sp. in the LMR model. [Copyright &y& Elsevier]

Increased fine sediment deposition is recognised as one of the major causes of biological impairment of rivers and streams influencing all components of aquatic communities. Notably, stream macroinvertebrates are affected showing changes in abundance and community composition. This makes macroinvertebrates an attractive choice for biomonitoring fine sediment stress. However, there are substantial knowledge gaps regarding the quantification of deposited fine sediment and the identification of taxa sensitive to fine sediment deposition, which could serve as indicators. In this study, we developed a stream type-specific index based on the taxon-specific response of macroinvertebrates to deposited fine sediment in small, coarse substrate-dominated mountain streams. We sampled fine sediment at 73 sampling sites in Western Germany (Europe) in spring 2014 and 2015 using a sediment remobilization technique. Macroinvertebrate taxalists originating from WFD monitoring surveys were available for all sites. We applied Threshold Indicator Taxa ANalysis (TITAN) on the fine sediment mass of the sampling sites and the corresponding macroinvertebrate taxalists to identify indicator taxa, which were then used for index development. In total, TITAN identified 95 reliable indicator taxa, of which some taxa tolerated large amounts of fine sediment (e.g., Gammarus roeselii and Tubificidae Gen. sp.), while others were found to be highly sensitive to increased fine sediment mass (e.g., Elodes sp. and Limnius perrisi). The newly developed index was tested on an independent data set and performed well in detecting fine sediment stress (Spearman's r = 0.63). Furthermore, the index was better related to the deposited fine sediment mass as compared to other fine sediment indices and standard metrics used for monitoring purposes under the Water Framework Directive (WFD). The diagnostic index can be a cost-effective biomonitoring tool for stream managers and can be used as a proxy for the impact of deposited fine sediment on the reach scale., (Copyright © 2018 Elsevier B.V. All rights reserved.)