Vergleich der Hydromorphologie und Makrozoobenthos-Gemeinschaft an verzweigten und unverzweigten Abschnitten deutscher Mittelgebirgsflüsse

This thesis investigates restored and naturally developed multiple-channel sections in German mountainous areas. Without human interference most streams in these areas would show this hydromorphological pattern. Unfortunately only short multiple-channels sections can be found or have been built in restoration projects. The quantity of hydromorphological differences compared to anthropogenically straightened single-channel sections and effects on macroinvertebrate communities are largely unknown. In a paired site study seven multiple- and seven single-channel sections were investigated and compared. The hypothesis was tested that multiple-channel sections have a larger area and higher habitat diversity, which also influences the biota. A standardised transect-point-protocol was applied in the summer of 2004 and 2005. Width of channel features (main and secondary channels, sidearms, standing water bodies, bars, banks, floodplains and embankments) and their habitat characteristics (aquatic, terrestrial or transient) were recorded along 20 equidistant transects across the bankfull width. Along these transects, aquatic habitats (substrate type, depth, current velocity) were recorded at 400 points per stream section. Section-wise analyses of both years built the elaborate basis against which macroinvertebrate data were tested. Altogether 199 substrate-specific macroinvertebrate samples were taken and processed separately. Finally, the relationships between hydromorphological characteristics and each section’s community were evaluated. Twelve hydromorphological metrics were calculated from the transect and point data. Metrics at three scales differentiated well between single- and multiple-channel sections: the macro-scale metrics mean channel width and shore length increased by factors of 2.1 and 2.4, respectively; the meso-scale metric mean number of channel features increased from two to ten per section; several micro-scale metrics, such as current velocity and depth variance, were significantly different between single-channel sections and most multiple-channel sections. Furthermore, substrate composition was more diverse in the multiple-channel sections. Correlation analyses of hydromorphological parameters suggest that metrics of different scales should be combined in order to evaluate hydromorphological diversity. The sites were revisited in 2005 and transect-point recordings were repeated to quantify annual changes within the sections. The amount of changes between two years differed between single- and multiple-channel sections. Water depths, aquatic widths and cross-section, riparian areas, and the waterside margins of the embankments have been modified by the streams in the course of the year. Multiple-channel sections showed more annual changes than the single-channel sections. Within the multiple-channel sections, natural and restored sites showed different extents of change with the latter showing higher and more varied changes in the multiple-channel sections. 199 substrate-specific macroinvertebrate samples were analysed for alpha- and beta-diversity and nestedness patterns. Taxa number, abundance, and evenness of communities found on multiple-channel substrates did not significantly differ from their single-channel section counterparts. Nestedness was neither different from a section's perspective, i.e. single- and multiple-channel sections were equally nested, nor from a substrate's perspective, i.e. substrates from either section were equally nested. The findings imply that substrates at single- and multiple-channel sections have similar macroinvertebrate communities, thus alpha-diversity is not changed. Different substrates host different communities, so beta-diversity might be influenced. Hence, stream restoration projects aiming at a re-development of macroinvertebrate diversity should focus on the generation and availability of high quality habitats, such as large wood. These results are further supported by occurrence of ten Coleoptera and seven Trichoptera taxa present exclusively on multiple-channel substrates, with the highest differences found for the fine mineral substrates such as loam or sand and for organic substrates such as living parts of terrestrial plants (LPTP), coarse particulate organic matter (CPOM) and large wood. Macroinvertebrate data from 140 substrate specific samples were then combined to representative communities for each section. Community data were subject to similarity and cluster analyses. 35 metrics were calculated with the taxalists, including taxa number, abundance, feeding type, habitat and current preferences. Biological metrics were correlated to hydromorphological parameters. Micro-scale morphological metrics, such as certain substrates areas and substrate spatial diversity, showed consistent correlations with biological metrics, as did several meso- and macro-scale metrics like aquatic width and shore length. The biological metrics percentage of shredders, number of taxa, percentage of littoral preference and the percentage of current preference (rheo- to limnophil and rheobiont) showed the most consistent correlations with hydromorphological parameters. Bray-Curtis similarity was very high (69−77%) between communities of single- and multiple-channel sections. The hydromorphological diversity of the multiple-channel sections is improved towards the reference condition. Habitat diversity is increased and a higher sediment dynamic becomes manifest in cross-section changes. However, effects on the macroinvertebrate community of substrates or the overall stream sections are not detectable and at best display a general tendency towards improvement. This lack of diversification of the macroinvertebrate community is attributed to several causes and a mixture of abiotic and biotic constraints likely apply. Reasons for high similarity of macroinvertebrate communities from single- or multiple-channel sections are discussed, including influence of large scale catchment pressures, length of restored sections and lack of potential re-colonisers

Disentangling the effect of climatic and hydrological predictor variables on benthic macroinvertebrate distributions from predictive models

Lotic freshwater macroinvertebrate species distribution models (SDMs) have been shown to improve when hydrological variables are included. However, most studies to date only include data describing climate or stream flow-related surrogates. We assessed the relative influence of climatic and hydrological predictor variables on the modelled distribution of macroinvertebrates, expecting model performance to improve when hydrological variables are included. We calibrated five SDMs using combinations of bioclimatic (bC), hydrological (H) and hydroclimatic (hC) predictor datasets and compared model performance as well as variance partition of all combinations. We investigated the difference in trait composition of communities that responded better to either bC or H configurations. The dataset bC had the most influence in terms of proportional variance, however model performance was increased with the addition of hC or H. Trait composition demonstrated distinct patterns between associated model configurations, where species that prefer intermediate to slow-flowing current conditions in regions further downstream performed better with bC–H. Including hydrological variables in SDMs contributes to improved performance, it is however, species-specific and future studies would benefit from hydrology-related variables to link environmental conditions and diverse communities. Consequently, SDMs that include climatic and hydrological variables could more accurately guide sustainable river ecosystem management.Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB) im Forschungsverbund Berlin e.V. (3473)Peer Reviewe

When is a hydrological model sufficiently calibrated to depict flow preferences of riverine species?

Riverine species have adapted to their environment, particularly to the hydrological regime. Hydrological models and the knowledge of species preferences are used to predict the impact of hydrological changes on species. Inevitably, hydrological model performance impacts how species are simulated. From the example of macroinvertebrates in a lowland and a mountainous catchment, we investigate the impact of hydrological model performance and the choice of the objective function based on a set of 36 performance metrics for predicting species occurrences. Besides species abundance, we use the simulated community structure for an ecological assessment as applied for the Water Framework Directive. We investigate when a hydrological model is sufficiently calibrated to depict species abundance. For this, we postulate that performance is not sufficient when ecological assessments based on the simulated hydrology are significantly different (analysis of variance, p < .05) from the ecological assessments based on observations. The investigated range of hydrological model performance leads to considerable variability in species abundance in the two catchments. In the mountainous catchment, links between objective functions and the ecological assessment reveal a stronger dependency of the species on the discharge regime. In the lowland catchment, multiple stressors seem to mask the dependence of the species on discharge. The most suitable objective functions to calibrate the model for species assessments are the ones that incorporate hydrological indicators used for the species prediction

The Freshwater Information Platform: a global online network providing data, tools and resources for science and policy support

Freshwaters are among the most complex, dynamic, and diverse ecosystems globally. Despite their small share of the earth’s surface (less than 1%) they are home to over 10% of all known animal species. Biodiversity decrease in general and freshwater biodiversity decline in particular have recently received increasing attention, and various policy instruments are now targeting the conservation, protection and enhancement of biodiversity and associated ecosystem services. Surveillance programs as well as a variety of research projects have been producing a tremendous amount of freshwater-related information. Though there have been various attempts to build infrastructures for online collection of such data, tools and reports, they often provide only limited access to resources that can readily be extracted for conducting large scale analyses. Here, we present the Freshwater Information Platform, an open system of relevant freshwater biodiversity-related information. We provide a comprehensive overview of the platform’s core components, highlight their values, present options for their use, and discuss future developments. This is complemented by information on the platform’s current management structure, options for contributing data and research results and an outlook for the future

More exposure opportunities for promoting freshwater conservation

Freshwater ecosystems have a higher percentage of threatened and extinct species than terrestrial or marine realms, but remain under‐represented in conservation research and actions arguably as a consequence of less popularity and promotion. Cover images of conservation journals were used as a proxy of exposure and potential promotion opportunities provided for different ecosystems and species. To examine whether articles related to cover images received more attention, citations and Altmetric scores of cover‐featured articles were compared with non‐featured ones within the same host journal issue. Freshwater ecosystems (10.4%) were featured less often than marine (15.2%) or terrestrial (74.4%) ecosystems on covers of 18 conservation journals from 1997 to 2016. All 15 most featured species are from terrestrial or marine ecosystems. In addition, cover‐featured studies showed higher citations and Altmetric scores than non‐featured ones within the same host journal issue, indicating that cover‐featured articles received more attention. Further investigations are needed to examine the relationship (i.e. whether there is a true causality) between being featured on the cover, and citations and Altmetric scores received by articles, as well as potentially resulting in greater conservation efforts. Nevertheless, we believe that providing exposure opportunities is likely to better inform the public about the continuing degradation of freshwater ecosystems and its impacts on human well‐being, including economic loss and danger to public health. Journal editors can contribute by balancing their selection of featured ecosystems and species when opportunities arise. Increasing exposure opportunities for freshwater ecosystems through various channels seems a promising approach to raise public awareness and appreciation of freshwater biodiversity. Scientists can play an active role and form an alliance with journal editors, conservation organizations, and media, to increase momentum in society for fresh waters to be experienced as essential ecosystems and prevent further degradation of freshwater habitats and biodiversity loss.Education, Audiovisual and Culture Executive Agency of the European Union: Erasmus Mundus Joint Doctorate SMART http://dx.doi.org/10.13039/501100000785Leibniz Association: Freshwater Megafauna Futures http://dx.doi.org/10.13039/501100001664Spanish Government’s María de Maeztu excellence accreditation 2018‐2022German Federal Ministry of Education and Research (BMBF)Peer Reviewe

A Global Agenda for Advancing Freshwater Biodiversity Research

Global freshwater biodiversity is declining dramatically, and meeting the challenges of this crisis requires bold goals and the mobilisation of substantial resources. While the reasons are varied, investments in both research and conservation of freshwater biodiversity lag far behind those in the terrestrial and marine realms. Inspired by a global consultation, we identify 15 pressing priority needs, grouped into five research areas, in an effort to support informed stewardship of freshwater biodiversity. The proposed agenda aims to advance freshwater biodiversity research globally as a critical step in improving coordinated actions towards its sustainable management and conservation

More exposure opportunities for promoting freshwater conservation

1. Freshwater ecosystems have a higher percentage of threatened and extinct species than terrestrial or marine realms, but remain under-represented in conservation research and actions arguably as a consequence of less popularity and promotion. 2. Cover images of conservation journals were used as a proxy of exposure and potential promotion opportunities provided for different ecosystems and species. To examine whether articles related to cover images received more attention, citations and Altmetric scores of cover-featured articles were compared with non-featured ones within the same host journal issue. 3. Freshwater ecosystems (10.4%) were featured less often than marine (15.2%) or terrestrial (74.4%) ecosystems on covers of 18 conservation journals from 1997 to 2016. All 15 most featured species are from terrestrial or marine ecosystems. 4. In addition, cover-featured studies showed higher citations and Altmetric scores than non-featured ones within the same host journal issue, indicating that cover-featured articles received more attention. Further investigations are needed to examine the relationship (i.e. whether there is a true causality) between being featured on the cover, and citations and Altmetric scores received by articles, as well as potentially resulting in greater conservation efforts. Nevertheless, we believe that providing exposure opportunities is likely to better inform the public about the continuing degradation of freshwater ecosystems and its impacts on human well-being, including economic loss and danger to public health. Journal editors can contribute by balancing their selection of featured ecosystems and species when opportunities arise. 5. Increasing exposure opportunities for freshwater ecosystems through various channels seems a promising approach to raise public awareness and appreciation of freshwater biodiversity. Scientists can play an active role and form an alliance with journal editors, conservation organizations, and media, to increase momentum in society for fresh waters to be experienced as essential ecosystems and prevent further degradation of freshwater habitats and biodiversity loss

Do alien species affect native freshwater megafauna?

1. Freshwater megafauna species (i.e., animals that can reach a body mass ≥30 kg, including fish, reptiles, mammals, and amphibians) play important roles in freshwater systems (e.g., by influencing habitat structure, trophic dynamics, or the dispersal of smaller species). As they tend to be large and charismatic, they may also function as flagship umbrella species in future freshwater conservation initiatives. Despite this, as a group they are highly threatened, and our knowledge of the nature of these threats is limited. In this study, we aim to improve our understanding of the impacts of alien species on native freshwater megafauna. 2. We undertook the first global assessment of the impacts of alien species on native freshwater megafauna using the Environmental Impact Classification for Alien Taxa (EICAT) framework. We conducted a literature review to identify published and grey literature on impacts, which we quantified and categorised by their severity and type, following the EICAT guidelines. 3. Negative impacts on native freshwater megafauna were caused by 61 alien species from a diverse range of taxonomic groups, including both freshwater and terrestrial alien species, and both vertebrates and invertebrates. They adversely affected 44 of 216 native freshwater megafauna species, including amphibians, fish, mammals, and reptiles. The Great Lakes Basin had the highest number of affected megafauna species (six of the 14 freshwater megafauna species it supports, mainly fish). Impacts occurred through a broad range of mechanisms (10 of the 12 identified mechanisms under EICAT); predation and competition were the most frequently reported mechanisms. Some impacts were relatively minor, adversely affecting the performance of individuals of native freshwater megafauna species. However, some reported impacts did cause declining populations of native freshwater megafauna species, and one impact contributed to the local extinction of the ship sturgeon (Acipenser nudiventris) in the Aral Sea. The vulnerability of native freshwater megafauna species to different types of impact varies during different life-cycle stages (egg, juvenile, and adult). 4. Our understanding of impacts posed by alien species on native freshwater megafauna is limited because data are unavailable for many regions, particularly the Global South, including hotspots for freshwater megafauna diversity such as the Amazon, Congo, Mekong, and Ganges-Brahmaputra basins. Freshwater megafauna species are often subject to multiple threats, which makes it difficult to determine the significance of alien species impacts relative to other threats such as habitat degradation and overexploitation. In addition, short-term studies are likely to be masking the severity of the impacts identified. We call for more long-term studies that attempt to identify population-level impacts, and for studies that identify impacts in data-deficient regions. 5. The EICAT assessments undertaken for this study will be reviewed by the EICAT Authority and subsequently incorporated into the IUCN EICAT database. They may be used to guide future research and conservation actions.China Scholarship Council (CSC)German Academic Exchange Service (DAAD; PRIME programme) http://dx.doi.org/10.13039/501100001655Bundesministerium für Bildung und Forschung (BMBF; 033W034A)Leibniz Association (Freshwater Megafauna Futures) http://dx.doi.org/10.13039/501100001664Peer Reviewe

Climate model variability leads to uncertain predictions of the future abundance of stream macroinvertebrates

Climate change has the potential to alter the flow regimes of rivers and consequently affect the taxonomic and functional diversity of freshwater organisms. We modeled future flow regimes for the 2050 and 2090 time horizons and tested how flow regimes impact the abundance of 150 macroinvertebrate species and their functional trait compositions in one lowland river catchment (Treene) and one mountainous river catchment (Kinzig) in Europe. We used all 16 global circulation models (GCMs) and regional climate models (RCMs) of the CORDEX dataset under the RCP 8.5 scenario to calculate future river flows. The high variability in relative change of flow among the 16 climate models cascaded into the ecological models and resulted in substantially different predicted abundance values for single species. This variability also cascades into any subsequent analysis of taxonomic or functional freshwater biodiversity. Our results showed that flow alteration effects are different depending on the catchment and the underlying species pool. Documenting such uncertainties provides a basis for the further assessment of potential climate-change impacts on freshwater taxa distributions

A high-resolution streamflow and hydrological metrics dataset for ecological modeling using a regression model

Hydrological variables are among the most influential when analyzing or modeling stream ecosystems. However, available hydrological data are often limited in their spatiotemporal scale and resolution for use in ecological applications such as predictive modeling of species distributions. To overcome this limitation, a regression model was applied to a 1 km gridded stream network of Germany to obtain estimated daily stream flow data (m3 s−1) spanning 64 years (1950–2013). The data are used as input to calculate hydrological indices characterizing stream flow regimes. Both temporal and spatial validations were performed. In addition, GLMs using both the calculated and observed hydrological indices were compared, suggesting that the predicted flow data are adequate for use in predictive ecological models. Accordingly, we provide estimated stream flow as well as a set of 53 hydrological metrics at 1 km grid for the stream network of Germany. In addition, we provide an R script where the presented methodology is implemented, that uses globally available data and can be directly applied to any other geographical region