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  • 1
    Online Resource
    Online Resource
    Wake flow patterns and turbulence around naturally deposited and installed trees in a gravel bed river
    Wiley ; 2022
    In:  International Review of Hydrobiology Vol. 107, No. 1-2 ( 2022-03), p. 22-33
    Details
    In: International Review of Hydrobiology, Wiley, Vol. 107, No. 1-2 ( 2022-03), p. 22-33
    Abstract: Large wood structures, such as wood fragments, debris jams, or entire trees, create flow and habitat diversity in rivers. A key flow feature associated with such structures is the wake, characterised by a core zone of reduced velocity and shear layers at its margins. Wakes are largely controlled by geometric and structural properties of the wood. In the present study, the flow patterns and turbulence created by different wood structures were compared at two study sites: naturally eroded and fragmented oaks (Site A) and artificial poplar installations (Site B). Flow and turbulence were quantified using pointwise velocity measurements with acoustic Doppler velocimeters (ADVs) and surface particle tracking velocimetry (SPTV). The measured flow patterns exhibited similarities with shallow porous wakes that feature fluid advection through the structure into the wake core downstream. Two additional features of wood structures were identified in the present study: (i) the growth of the shear layers was hindered by bed friction like for shallow mixing layers and (ii) the presence of a tree stem and sediment deposit in the wake centre delayed or even suppressed the interaction of the shear layers and vortex street formation similar to a wake‐splitter plate. Methodologically, the combined ADV/SPTV measurement approach and the use of analytical models for shallow mixing layers proved to be highly valuable to decipher the complex flow patterns around wood structures in the field.
    Type of Medium: Online Resource
    ISSN: 1434-2944 , 1522-2632
    URL: Issue
    URL: Article
    DOI: 10.1002/iroh.v107.1-2
    DOI: 10.1002/iroh.202102096
    Language: English
    Publisher: Wiley
    Publication Date: 2022
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    detail.hit.zdb_id: 1420232-3
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  • 2
    Online Resource
    Online Resource
    Hydraulic and biological controls of biofilm nitrogen uptake in gravel‐bed streams
    Wiley ; 2021
    In:  Limnology and Oceanography Vol. 66, No. 11 ( 2021-11), p. 3887-3900
    Details
    In: Limnology and Oceanography, Wiley, Vol. 66, No. 11 ( 2021-11), p. 3887-3900
    Abstract: Epibenthic biofilms are important in regulating nitrogen (N) fluxes in stream ecosystems. The efficiency of the regulation is controlled by hydraulic and biological processes and their interactions. However, knowledge on the underlying physical and biological processes, their controlling parameters, and interactions in stream ecosystems is still limited. To analyze the relative importance of hydraulic and biological controls on biofilm N uptake, we measured turbulence, biofilm N uptake using a stable isotope tracer, and biofilm biomass in two gravel‐bed streams with contrasting nutrient concentrations for two seasons. We found high within‐stream variability in biofilm areal N uptake and uptake velocity, which exceeded variability between streams and seasons by 60% and 30%, respectively. Sixty‐four percent of the within‐stream variability in uptake velocity was explained by hydraulic mass transfer and biofilm characteristics, which were described in terms of the turbulent dissipation rate and the biofilm biomass, respectively. We show that surface renewal theory based on scales of the smallest turbulent eddies can be used to estimate transfer velocities at the sediment–water interface and can be extrapolated to larger scales by spatial averaging. Our results improved the mechanistic understanding of the processes regulating biofilm N uptake at small scale which contributes to the understanding of ecosystem functioning in low‐order streams and supports upscaling to larger spatiotemporal scales along stream networks.
    Type of Medium: Online Resource
    ISSN: 0024-3590 , 1939-5590
    URL: Issue
    URL: Article
    DOI: 10.1002/lno.v66.11
    DOI: 10.1002/lno.11927
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 2033191-5
    detail.hit.zdb_id: 412737-7
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  • 3
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    Online Resource
    Benthic metabolism and nutrient uptake vary with geomorphology and season in a lowland river
    University of Chicago Press ; 2023
    In:  Freshwater Science Vol. 42, No. 1 ( 2023-03-01), p. 58-69
    Details
    In: Freshwater Science, University of Chicago Press, Vol. 42, No. 1 ( 2023-03-01), p. 58-69
    Type of Medium: Online Resource
    ISSN: 2161-9549 , 2161-9565
    URL: Article
    DOI: 10.1086/723895
    Language: English
    Publisher: University of Chicago Press
    Publication Date: 2023
    detail.hit.zdb_id: 2651496-5
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  • 4
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    Online Resource
    Hydromorphologic Sorting of In-Stream Nitrogen Uptake Across Spatial Scales
    Springer Science and Business Media LLC ; 2021
    In:  Ecosystems Vol. 24, No. 5 ( 2021-08), p. 1184-1202
    Details
    In: Ecosystems, Springer Science and Business Media LLC, Vol. 24, No. 5 ( 2021-08), p. 1184-1202
    Abstract: Nitrogen (N) uptake is a key process in stream ecosystems that is mediated mainly by benthic microorganisms (biofilms on different substrata) and has implications for the biogeochemical fluxes at catchment scale and beyond. Here, we focused on the drivers of assimilatory N uptake, especially the effects of hydromorphology and other environmental constraints, across three spatial scales: micro, meso and reach. In two seasons (summer and spring), we performed whole-reach 15 N-labelled ammonium injection experiments in two montane, gravel-bed stream reaches with riffle–pool sequences. N uptake was highest in epilithic biofilms, thallophytes and roots (min–max range 0.2–545.2 mg N m −2 day −1 ) and lowest in leaves, wood and fine benthic organic matter (0.05–209.2 mg N m −2 day −1 ). At the microscale, N uptake of all primary uptake compartments except wood was higher in riffles than in pools. At the mesoscale, hydromorphology determined the distribution of primary uptake compartments, with fast-flowing riffles being dominated by biologically more active compartments and pools being dominated by biologically less active compartments. Despite a lower biomass of primary uptake compartments, mesoscale N uptake was 1.7–3.0 times higher in riffles than in pools. At reach scale, N uptake ranged from 79.6 to 334.1 mg N m −2 day −1 . Highest reach-scale N uptake was caused by a bloom of thallopyhtes, mainly filamentous autotrophs, during stable low discharge and high light conditions. Our results reveal the important role of hydromorphologic sorting of primary uptake compartments at mesoscale as a controlling factor for reach-scale N uptake in streams.
    Type of Medium: Online Resource
    ISSN: 1432-9840 , 1435-0629
    URL: Article
    DOI: 10.1007/s10021-020-00576-7
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2021
    detail.hit.zdb_id: 1478731-3
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  • 5
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    Online Resource
    Effective restoration measures in river‐floodplain ecosystems: Lessons learned from the ‘Wilde Mulde’ project
    Wiley ; 2022
    In:  International Review of Hydrobiology Vol. 107, No. 1-2 ( 2022-03), p. 9-21
    Details
    In: International Review of Hydrobiology, Wiley, Vol. 107, No. 1-2 ( 2022-03), p. 9-21
    Abstract: Over the last 40 years, a growing number of restoration projects have been implemented to improve the ecological conditions of highly degraded rivers and their floodplains. Despite considerable investment in these projects, information is still limited about the effectiveness and the success of such river restoration measures, mainly due to a lack of standardised and interdisciplinary assessment approaches. During the project ‘Wilde Mulde—Restoration of a dynamic riverine landscape in Central Germany’, we implemented hydromorphological restoration measures (installation of large wood, removal of rip‐rap, reconnection of a former river side‐arm) along a lowland river in Central Germany. We carried out intensive scientific monitoring of biodiversity, hydromorphology, ecosystem functions and services, as well as socio‐economic aspects. A Before/After‐Control/Impact (BACI) design was used to identify the spatial and temporal effects of the restoration measures and to distinguish them from changes caused by background variation. For this, we used a comprehensive set of indicators, including abiotic (flow velocity, diversity of riverbed topography, and flow resistance), biological (ecosystem respiration, macroinvertebrates, fish, carabids, vegetation, and birds) and socio‐economic (acceptance and public awareness) indicators as well as the ecosystem service indicator aesthetic quality of the landscape. To meet the inherent challenges of such a large‐scale field experiment, like unpredictable environmental conditions, we used an experimental approach that allowed us to demonstrate a measurable success of the implemented restoration measures. The majority of the abiotic and some of the biological and socio‐economic indicators at the restored sites approached values of a natural reference site while already deviating from values of a nonnatural reference site two years after restoration. In addition to the applied interdisciplinary approach, multiple scales of field investigations and data analyses are essential as key components for evaluating successful river and floodplain restoration projects.
    Type of Medium: Online Resource
    ISSN: 1434-2944 , 1522-2632
    URL: Issue
    URL: Article
    DOI: 10.1002/iroh.v107.1-2
    DOI: 10.1002/iroh.202102086
    Language: English
    Publisher: Wiley
    Publication Date: 2022
    detail.hit.zdb_id: 2006634-X
    detail.hit.zdb_id: 1420232-3
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  • 6
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    Online Resource
    Near streambed flow shapes microbial guilds within and across trophic levels in fluvial biofilms
    Wiley ; 2020
    In:  Limnology and Oceanography Vol. 65, No. 10 ( 2020-10), p. 2261-2277
    Details
    In: Limnology and Oceanography, Wiley, Vol. 65, No. 10 ( 2020-10), p. 2261-2277
    Abstract: Flow is an important physical driver of biofilm communities. Here, we tested the effects of the near bed flows in two mountainous stream reaches on the structure of biofilm microbial guilds (autotrophs, heterotrophic bacteria, and heterotrophic protists) within and across trophic levels. Near bed flow velocity and turbulent kinetic energy were important physical drivers for structuring the communities within and across guilds of the multitrophic fluvial biofilms. The effects of flow were nested in a seasonal and spatial (across‐streams) context. Changes in physicochemical factors (temperature, light, dissolved carbon, and nutrients) along the reaches were alike in both streams suggesting that environmental boundary conditions at larger temporal scales were responsible for the seasonal differences of biofilm communities, whereas locally microbial diversity was shaped by near bed flow. Typically, the abundance of autotrophs increased with flow, indicating that biofilms shifted toward increasing autotrophy with increasing shear forces. Filamentous autotrophs seemed to provide protected habitats from the shear forces for smaller sized bacteria. Heterotrophic protist abundance decreased with flow leading to decreasing grazer to prey ratio. Bacteria thus benefitted from a reduction in grazing pressure at faster flowing, more turbulent sites. Our results suggest that near bed flow can impact the magnitude and direction of matter fluxes through the microbial food web and possibly affect ecosystem functioning of fluvial biofilms.
    Type of Medium: Online Resource
    ISSN: 0024-3590 , 1939-5590
    URL: Issue
    URL: Article
    DOI: 10.1002/lno.v65.10
    DOI: 10.1002/lno.11451
    Language: English
    Publisher: Wiley
    Publication Date: 2020
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    detail.hit.zdb_id: 412737-7
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  • 7
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    Online Resource
    Secondary production and richness of native and non-native macroinvertebrates are driven by human-altered shoreline morphology in a large river
    Springer Science and Business Media LLC ; 2016
    In:  Hydrobiologia Vol. 776, No. 1 ( 2016-8), p. 51-65
    Details
    In: Hydrobiologia, Springer Science and Business Media LLC, Vol. 776, No. 1 ( 2016-8), p. 51-65
    Type of Medium: Online Resource
    ISSN: 0018-8158 , 1573-5117
    URL: Article
    DOI: 10.1007/s10750-016-2734-6
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2016
    detail.hit.zdb_id: 1478162-1
    detail.hit.zdb_id: 214428-1
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  • 8
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    Streamside mobile mesocosms (MOBICOS): A new modular research infrastructure for hydro‐ecological process studies across catchment‐scale gradients
    Wiley ; 2020
    In:  International Review of Hydrobiology Vol. 105, No. 3-4 ( 2020-06), p. 63-73
    Details
    In: International Review of Hydrobiology, Wiley, Vol. 105, No. 3-4 ( 2020-06), p. 63-73
    Abstract: A key research aim for lotic ecosystems is the identification of natural and anthropogenic pressures that impact ecosystem status and functions. As a consequence of these perturbations, many lotic ecosystems are exposed to complex combinations of nonchemical and chemical stressors. These stressors comprise temperature fluctuations, flow alterations, elevated solute loads or xenobiotics, and all these factors can pose stress upon aquatic ecosystems on different temporal, spatial and biological scales. Factorial experiments are essential to reveal causal relationships especially between combined stressors and their effects in the environment. However, experimental tools that account for the complexity of running waters across different ecosystem compartments, levels of biological organisation, natural or anthropogenic environmental gradients, and replicability are rare. Here we present a new research infrastructure consisting of streamside mobile mesocosms (MOBICOS) that allows analysing the effects of stressors and stressor combinations through multifactorial experiments in near‐natural settings and across anthropogenic pressure gradients. Consisting of eight container‐based running water laboratories operated as bypasses to running surface waters, MOBICOS combines in situ real‐time monitoring of physicochemical and biological parameters with manipulative experiments across ranges of environmental conditions. Different flume types can be set up within MOBICOS to separate and combine different ecosystem compartments (pelagic, epibenthic and hyporheic zones) in a flexible and modular way. Due to its compact design, the MOBICOS units can be shifted easily to particular sites of interest. Furthermore, simultaneous operation of multiple MOBICOS units at different sites allows the integration of natural gradients in multifactorial experiments. We highlight the versatility of the MOBICOS experimental infrastructure with two case studies addressing (a) hydraulic control of lotic biofilms and (b) pollution‐induced community tolerance of biofilms along an environmental gradient. The modular and mobile MOBICOS units have the potential to significantly advance our understanding of causal relationships between natural environmental oscillations, anthropogenic stressors and their combined ecological impacts on lotic aquatic ecosystems beyond existing stream mesocosm approaches.
    Type of Medium: Online Resource
    ISSN: 1434-2944 , 1522-2632
    URL: Issue
    URL: Article
    DOI: 10.1002/iroh.v105.3-4
    DOI: 10.1002/iroh.201902009
    Language: English
    Publisher: Wiley
    Publication Date: 2020
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    detail.hit.zdb_id: 1420232-3
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  • 9
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    Online Resource
    Large wood in river restoration: A case study on the effects on hydromorphology, biodiversity, and ecosystem functioning
    Wiley ; 2022
    In:  International Review of Hydrobiology Vol. 107, No. 1-2 ( 2022-03), p. 34-45
    Details
    In: International Review of Hydrobiology, Wiley, Vol. 107, No. 1-2 ( 2022-03), p. 34-45
    Abstract: Large wood (LW) is an integral part of natural river ecosystems and determines their ecological integrity by modulating hydromorphology and providing habitats. Hence, LW installations are a common restoration measure in large rivers, even if effects on biodiversity are ambiguous or unknown for ecosystem functioning. Here we quantified the hydromorphological, biological, and functional effects of LW 8 months after installation in a large gravel‐bed river. Both morphological and flow diversity increased strongly by 821% and 127%, respectively. Similarly, fish abundance increased nearly 10‐fold, and macroinvertebrate diversity increased by 35%. Ecosystem functions benefited from LW installation and increased significantly (e.g., by up to 390% for bacterial production) at sites influenced by LW compared to those without LW. Our results highlight the role of the bark habitat of LW that increased the direct effects of LW via the provision of new habitat and stimulated ecosystem‐wide processes. Our integrative approach evaluating the success of LW installations in a large river revealed cascading effects from the provisioning of new habitats, the increase of species diversity to higher ecosystem functioning. It also demonstrated that hydromorphological parameters or community composition alone are insufficient to quantify the complex effects of LW installation, which underlines the necessity to evaluate restoration success with different measures.
    Type of Medium: Online Resource
    ISSN: 1434-2944 , 1522-2632
    URL: Issue
    URL: Article
    DOI: 10.1002/iroh.v107.1-2
    DOI: 10.1002/iroh.202102089
    Language: English
    Publisher: Wiley
    Publication Date: 2022
    detail.hit.zdb_id: 2006634-X
    detail.hit.zdb_id: 1420232-3
    SSG: 12
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