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  • Brauns, M  (32)
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  • 1
    Language: English
    In: Journal of Applied Ecology, 1 August 2011, Vol.48(4), pp.916-925
    Description: 1. Shoreline development and the associated loss of littoral habitats represent a pervasive alteration of the ecological integrity of lakes and have been identified as major drivers for the loss of littoral biodiversity world-wide. Little is known about the effects of shoreline development on the structure of, and energy transfer in, littoral food webs, even though this information is urgently needed for management and mitigation measures. 2. We measured macroinvertebrate biomass and analysed potential food resources using stable isotopes (δ¹³C, δ¹⁵N) and mixing models to compare the complexity and the trophic base of littoral food webs between undeveloped and developed shorelines in three North German lowland lakes. 3. The lower diversity of littoral habitats found at developed shorelines was associated with lower diversity of food resources and consumers. Consequently, the number of trophic links in food webs at developed shorelines was up to one order of magnitude lower as compared with undeveloped shorelines. 4. Mixing model analysis showed that consumer biomass at undeveloped shorelines was mainly derived from the particulate organic matter (FPOM) and coarse particulate organic matter of terrestrial origin (CPOM). The contribution of CPOM to consumer biomass was twofold lower at developed shorelines, and consumer biomass was mainly derived from FPOM and suspended particulate organic matter. 5. Synthesis and application. Shoreline development impacts the flow of organic matter within littoral food webs primarily through the reduction in littoral habitat diversity. These effects are exacerbated by clearcutting of the riparian vegetation, which disrupts cross-boundary couplings between the riparian and the littoral zone. Lakeshore conservation should focus on preserving the structural integrity of the littoral zone, while restoration of coarse woody debris, reed and root habitats can be a cost-efficient measure to improve degraded lakeshores. The local effects of shoreline development demonstrated in this study might lead to whole-lake effects, but future studies are needed to derive thresholds at which shoreline development has consequences for the structure and functioning of the entire ecosystem.
    Keywords: Vegetation and Community ecology
    ISSN: 00218901
    E-ISSN: 13652664
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  • 2
    In: Canadian Journal of Fisheries and Aquatic Sciences (Journal canadien des sciences halieutiques et aquatiques), 2011, Vol.68(1), pp.74-88
    Description: We compared the invertebrate production and stable isotope signatures of key ecosystem compartments of urban sites subjected to the input of tertiary-treated wastewater with those of upstream sites in an agricultural lowland stream. We detected a significant shift in the trophic basis of invertebrate production from upstream, natural and agricultural resources, to urban resources, i.e., wastewater-derived organic matter as well as autochthonous primary production based on wastewater-derived nutrients. Invertebrate production was higher at urban sites than at agricultural sites. However, the median contribution of the most important secondary producer, the shredder Gammarus roeseli , to total invertebrate production was lower at urban sites (9%) than at agricultural sites (61%). The low production of G. roeseli at urban sites was associated with the absence of allochthonous coarse particulate organic matter (CPOM) habitats, rather than the loss of CPOM as a food resource. Our results suggest that contemporary urban stressors in developed countries affect secondary producers less severely than historically recorded, but still profoundly change the matter fluxes and ecosystem functioning of running waters. Restoration of the native riparian vegetation, channel naturalization, and adequate dilution of tertiary-treated wastewater may partially mitigate adverse effects on invertebrate communities and their secondary production.
    Description: Nous comparons la production d'invertbrs et les signatures d'isotopes stables de compartiments cls de l'cosystme dans des sites urbains soumis l'apport d'eaux uses de traitement tertiaire par comparaison des sites d'amont dans un cours d'eau agricole de plaine. Nous dtectons un changement significatif dans la base trophique de la production d'invertbrs, partir des ressources naturelles et agricoles en amont vers des ressources urbaines, c'est--dire de la matire organique drive des eaux uses, ainsi qu'une production primaire autochtone base sur des nutriments provenant des eaux uses. La production d'invertbrs est plus leve dans les sites urbains que dans les sites agricoles. Cependant, la contribution mdiane du producteur secondaire le plus important, le dchiqueteur Gammarus roeseli , la production totale des invertbrs est plus basse aux sites urbains (9 %) qu'aux sites agricoles (61 %). La faible production de G. roeseli aux sites urbains est associe l'absence d'habitats matire organique particulaire grossire (CPOM) allochtone, plutt qu' la perte de CPOM comme ressource alimentaire. Nos rsultats laissent croire que les facteurs urbains actuels de stress dans les pays dvelopps affectent les producteurs secondaires moins svrement que signal dans le pass, mais qu'ils modifient nanmoins profondment les flux de matire et le fonctionnement de l'cosystme dans les eaux courantes. La restauration de la vgtation riveraine indigne, la naturalisation du chenal et la dilution adquate des eaux uses aprs un traitement tertiaire peuvent en partie rduire les effets ngatifs sur les communauts d'invertbrs et leur production secondaire.
    Keywords: Rivers ; Isotopes ; Ecosystems ; Environmental Impact ; Pollution Effects ; Trophic Structure ; Particulate Organic Matter ; Freshwater Organisms ; Secondary Production ; Waste Water ; Agricultural Runoff ; Chemical Analysis ; Pollution ; Gammarus Roeseli ; Germany, Erpe R. ; Freshwater ; Mechanical and Natural Changes ; Productivity;
    ISSN: 0706-652X
    E-ISSN: 1205-7533
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  • 3
    Language: English
    In: Hydrobiologia, 2016, Vol.768(1), pp.37-50
    Description: Length–mass relationships are widely used to estimate body mass from body dimensions for freshwater macroinvertebrates. The relationships are influenced by environmental conditions and should be applied within ecosystems and geographic regions similar to those for which they were estimated. However, very few relationships exist for littoral macroinvertebrates, and thus we provide length–mass relationships for macroinvertebrates from lakes of the Central European lowlands. We compared log-linear and nonlinear methods for fitting length–mass relationships and tested the smearing factor for removing bias in mass predictions from log-linear models. We also estimated conversion factors to correct for mass changes during ethanol preservation and assessed the transferability of our results to different geographical regions. We showed that the log-linear approach gave better results in fitting length–mass relationships, while residuals showed that nonlinear models over-predict the mass of small individuals. The smearing correction factor successfully removed bias introduced by log transformation, and relationships transferred well between lakes in the same and different geographical regions. In total, 52 bias-corrected length–mass relationships are provided for littoral macroinvertebrates that are applicable also to lakes in geographic regions with similar environmental conditions, such as the Central European lowlands or the temperate lowland zone of America.
    Keywords: Preservation conversion factor ; Smearing factor ; Length–mass relationships ; Macroinvertebrates ; Additive vs. multiplicative errors ; Log-linear vs. nonlinear regression
    ISSN: 0018-8158
    E-ISSN: 1573-5117
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  • 4
    Language: English
    In: Hydrobiologia, 2017, Vol.799(1), pp.37-48
    Description: Ephemeral ponds are often dominated by species with both terrestrial and aquatic life phases. Such species have the potential to strongly alter the food web structure of ponds, particularly if they are predators. Here we experimentally tested the effects of salamander larvae ( Salamandra salamandra ) on invertebrate communities in ephemeral forest ponds. We repeatedly split two ponds into salamander enclosure- and exclosure-segments, and compared the diversity and biomass of potential prey organisms. We used stable isotopes of carbon (δ 13 C) and nitrogen (δ 15 N) of resources and consumers to characterise the food web structure. The presence of salamander larvae did not affect abundances of culicid larvae, their preferred prey. The population dynamics of most insect larvae was independent of the presence of salamander larvae, and was instead driven by the timing of hatching and emergence. However, a significant reduction resulting from salamander predation could be detected in the less abundant chironomid larvae. There was no substantial alteration of the food web structure as indicated by stable isotopes. However, the stable isotope results suggest a strong trophic subsidisation from the terrestrial system, which is probably the reason for the weak top-down effects of the salamander larvae on the invertebrate food web.
    Keywords: Biodiversity ; Salamandra salamandra ; Top-down ; Trophic cascades ; Aquatic-terrestrial linkage
    ISSN: 0018-8158
    E-ISSN: 1573-5117
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  • 5
    Language: English
    In: Hydrobiologia, 2016, Vol.776(1), pp.51-65
    Description: This study addressed the influence of common shoreline engineering structures (off-bankline revetment, rip rap and wing dike) on richness, biomass and secondary production of native and non-native macroinvertebrates in the navigation channel and near-shore habitats in the Elbe River (Germany). Within the navigation channel, only marginal differences among engineering structures were observed, and non-native species were absent from all samples. At the shoreline, secondary production of non-native species was significantly greater at the rip rap and represented 59% of total secondary production in near-shore habitats. Conversely, secondary production of native species at the shoreline was 9-fold lower at the rip rap and more than twice the rates at the wing dike. Differences in secondary production among engineering structures were attributed to differential distribution of substrate types. Boulder substrates, the dominant substrate type in the rip rap, promoted contributions of non-native species while macrophytes and silt were associated with high contributions of native species at the off-bankline revetment. Our results reveal that the morphological configuration of engineering structures in large rivers not only controls the rate of secondary production for macroinvertebrates but also the contribution of non-native species to total community functioning.
    Keywords: Ecosystem functioning ; Elbe River ; Dikerogammarus villosus ; Neozoa ; Non-native species ; River engineering
    ISSN: 0018-8158
    E-ISSN: 1573-5117
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  • 6
    Language: English
    In: Hydrobiologia, 2013, Vol.717(1), pp.147-159
    Description: Reduction of flow constitutes one of the most severe human alterations to rivers, as it affects the key abiotic feature of these ecosystems. While there has been considerable progress in understanding the effects of reduced flow on benthic macroinvertebrates, cascading effects of flow reduction on dissolved oxygen concentrations (DO) have not yet received much attention. We compared the macroinvertebrate composition between reference conditions and a situation after several years of discharge reduction in the Spree River (Brandenburg, Germany). Community composition shifted from rheophilic species to species indifferent to flow conditions. Filter feeders were partially replaced by collector/gatherers, which likely reduces the retention of organic matter, and thus the self-purification capacity of the river section. These shifts were associated with low discharge during summer, cascading into daily DO concentration minima of less than 5 mg l −1 which prevailed 74% of the days in summer. This depletion of DO after flow reduction presumably caused the observed species turnover. Hence, flow reduction in lowland rivers may not only directly impair the ecological functions provided by benthic macroinvertebrates but may also act indirectly by depleting DO concentrations.
    Keywords: Low flow ; Dissolved oxygen ; Discharge ; Functional feeding groups ; Flow preferences ; Spree River
    ISSN: 0018-8158
    E-ISSN: 1573-5117
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  • 7
    Language: English
    In: Hydrobiologia, 2010, Vol.649(1), pp.365-373
    Description: Littoral macroinvertebrates are increasingly used for assessing the ecological status of lakes according to the EU Water Framework Directive. This requires harmonised sampling methods, but information on the appropriate spatial scale of the sampling as well as on the adequate sample sizes are mostly lacking. In this study, we compared the spatial variability of littoral (〈1.2 m water depth) macroinvertebrate community composition within habitats and within sites to test whether habitat-specific sampling can reduce their spatial variability. Furthermore, we determined the sample size necessary to obtain maximum species richness for a given habitat type. Spatial variability of macroinvertebrate community composition was significantly lower within habitats than within sampling sites, except for communities of coarse woody debris. Species–area curves revealed that a sample size of 1 m 2 per habitat was not sufficient to obtain the maximum species richness due to the dominance of rare species, which suggests that compilation of taxon inventories may require more exhaustive sampling with sampling sizes substantially larger than 1 m 2 . Separate analysis for species assigned to incidence classes showed that a mean area of 0.63 m 2 per habitat is sufficient to record all species with frequent and medium incidences, and 76% of the rare species. We conclude that habitat-specific sampling is an effective way to reduce the inherent spatial variability of littoral macroinvertebrate communities and that a sample size of 0.63 m 2 per habitat is sufficient to represent their dominant and subdominant elements. The application of this adequate sample size to other lake types than large oligotrophic lakes has to be exercised with caution, in particular if community composition and richness patterns differ. However, our results are based on data from lakes that represent the typical lake type found throughout the Central Baltic ecoregion ensuring its wider applicability in this ecoregion.
    Keywords: Coarse woody debris ; Spatial variability ; Species richness ; Species–area curves ; Water Framework Directive
    ISSN: 0018-8158
    E-ISSN: 1573-5117
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  • 8
    Language: English
    In: BioScience, 1 November 2015, Vol.65(11), pp.1057-1065
    Description: The rationale of most restoration strategies is that with reconstruction of natural habitats comes biodiversity, and ecosystem functioning and services will follow suit. Uncertainty and frequent failure in restoration outcomes, however, are recurrent and likely related to the complexity...
    Keywords: Biology;
    ISSN: 00063568
    E-ISSN: 15253244
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  • 9
    Language: English
    In: PLoS ONE, 2016, Vol. 11(5)
    Description: Hydrogen stable isotopes (δ2H) have recently been used to complement δ13C and δ15N in food web studies due to their potentially greater power to separate sources of organic matter in aquatic food webs. However, uncertainties remain regarding the use of δ2H, since little is known about the potential variation in the amount of exchangeable hydrogen (Hex) among common sample materials or the patterns of δ2H when entire food webs are considered. We assessed differences in Hex among the typical sample materials in freshwater studies and used δ2H, δ13C and δ15N to compare their effectiveness in tracing allochthonous matter in food webs of two small temperate lakes. Our results showed higher average amounts of Hex in animal tissues (27% in fish and macroinvertebrates, 19% in zooplankton) compared to most plant material (15% in terrestrial plants and 8% in seston/periphyton), with the exception of aquatic vascular plants (23%, referred to as macrophytes). The amount of Hex correlated strongly with sample lipid content (inferred from C:N ratios) in fish and zooplankton samples. Overall, the three isotopes provided good separation of sources (seston, periphyton, macrophytes and allochthonous organic matter), particularly the δ2H followed by δ13C. Aquatic macrophytes revealed unexpectedly high δ2H values, having more elevated δ2H values than terrestrial organic matter with direct implications for estimating consumer allochthony. Organic matter from macrophytes significantly contributed to the food webs in both lakes highlighting the need to include macrophytes as a potential source when using stable isotopes to estimate trophic structures and contributions from allochthonous sources.
    Keywords: Natural Sciences ; Earth And Related Environmental Sciences ; Oceanography, Hydrology And Water Resources ; Naturvetenskap ; Geovetenskap Och Miljövetenskap ; Oceanografi, Hydrologi Och Vattenresurser
    ISSN: 1932-6203
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  • 10
    Language: English
    In: Hydrobiologia, 2016, Vol.767(1), pp.207-220
    Description: Lake shores are characterised by a high natural variability, which is increasingly threatened by a multitude of anthropogenic disturbances including morphological alterations to the littoral zone. The European Water Framework Directive (EU WFD) calls for the assessment of lake ecological status by monitoring biological quality elements including benthic macroinvertebrates. To identify cost- and time-efficient sampling strategies for routine lake monitoring, we sampled littoral invertebrates in 32 lakes located in different geographical regions in Europe. We compared the efficiency of two sampling methodologies, defined as habitat-specific and pooled composite sampling protocols. Benthic samples were collected from unmodified and morphologically altered shorelines. Variability within macroinvertebrate communities did not differ significantly between sampling protocols across alteration types, lake types and geographical regions. Community composition showed no significant differences between field composite samples and artificially generated composite samples, and correlation coefficients between macroinvertebrate metrics calculated with both methods and a predefined morphological stressor index were similar. We conclude that proportional composite sampling represents a time- and cost-efficient method for routine lake monitoring as requested under the EU WFD, and may be applied across various European geographical regions.
    Keywords: Morphological alteration ; Macroinvertebrates ; Lake monitoring ; Method comparison ; Littoral zone ; EU Water Framework Directive
    ISSN: 0018-8158
    E-ISSN: 1573-5117
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