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  • 1
    Language: English
    In: Oecologia, 2011, Vol.165(1), pp.101-109
    Description: Little is known about the effects of waves on predator–prey interactions in the littoral zones of freshwaters. We conducted a set of mesocosm experiments to study the differential effects of ship- and wind-induced waves on the foraging success of littoral fish on benthic invertebrates. Experiments were conducted in a wave tank with amphipods ( Gammarus roeseli ) as prey, and age-0 bream ( Abramis brama , B0), age-0 and age-1 dace ( Leuciscus leuciscus , D0 and D1) as predators. The number of gammarids suspended in the water column was higher in the wave treatments compared to a no-wave control treatment, especially during pulse waves mimicking ship-induced waves in comparison to continuous waves mimicking wind-induced waves. The resulting higher prey accessibility in the water column was differently exploited by the three types of predatory fish. D0 and D1 showed significantly higher foraging success in the pulse wave treatment than in the continuous and control treatments. The foraging success of D0 appears to be achieved more easily, since significantly higher swimming activity and more foraging attempts were recorded only for D1 under the wave treatments. In contrast, B0 consumed significantly fewer gammarids in both wave treatments than in the control. Hence, waves influenced predator–prey interactions differently depending on wave type and fish type. It is expected that regular exposure to ship-induced waves can alter littoral invertebrate and fish assemblages by increasing the predation risk for benthic invertebrates that are suspended in the water column, and by shifting fish community compositions towards species that benefit from waves.
    Keywords: Ship- and wind-induced waves ; Hydrodynamic disturbance ; Invertebrate detachment ; Foraging success
    ISSN: 0029-8549
    E-ISSN: 1432-1939
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  • 2
    Language: English
    In: The Science of the Total Environment, Nov 1, 2012, Vol.438, p.435(12)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.scitotenv.2012.08.087 Byline: Daniel Graeber, Jorg Gelbrecht, Martin T. Pusch, Christine Anlanger, Daniel von Schiller Keywords: Fluorescence; Parallel Factor Analysis; Seasonality; Redox state; Forest; Wetland Abstract: Dissolved organic matter (DOM) is an important part of the global carbon cycle and significantly influences aquatic ecosystem functions. Recent studies suggest that its amount and composition in freshwaters may be altered by agricultural land use, whereby the influence of preceding in-stream production and processing is not clear. To assess the land use effect on DOM amount and composition for the export from terrestrial to freshwater systems at the land-water interface, we sampled headwater streams draining agricultural and near-pristine catchments (forested and wetland) in the North German plains. To account for spatial and seasonal variation, we conducted a screening of DOM amount (53 sites) and composition (42 sites), and conducted bi-weekly samplings to investigate seasonal variation at eight sites over one year. Concentrations of dissolved organic carbon (DOC) were significantly higher for agricultural and wetland catchments than for forested catchments. Moreover, DOC loads exhibited higher seasonal variation for agricultural and wetland catchments than for forested catchments, which was due to higher variation in discharge. Parallel Factor Analysis revealed that the composition of DOM in agricultural catchments was significantly different from the other studied catchment types, and was characterized by low redox state and high structural complexity. Moreover, a gradient from protein- to humic-like fluorescence significantly separated forested from agricultural and wetland catchments. The contribution of humic-like DOM was strongly and positively related to DOC concentration, suggesting a mechanistic coupling of both. The effects of land use on patterns of DOC concentration and DOM composition were consistent across seasons, implying that land use strongly regulates DOM export. Overall, this study clearly shows the seasonally independent importance of agricultural land use for the amount and composition of DOM fluxes from the terrestrial zone to surface waters. These altered fluxes may affect ecosystem metabolism and health of agricultural headwaters and downstream situated aquatic ecosystems. Article History: Received 19 April 2012; Revised 20 July 2012; Accepted 28 August 2012
    Keywords: Agricultural Industry -- Analysis ; Land Use Planning -- Analysis ; Fluorescence -- Analysis ; Agricultural Land -- Analysis ; Aquatic Ecosystems -- Analysis ; Wetlands -- Analysis ; Carbon Cycle -- Analysis
    ISSN: 0048-9697
    Source: Cengage Learning, Inc.
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  • 3
    Language: English
    In: Water science and technology : a journal of the International Association on Water Pollution Research, 2012, Vol.66(9), pp.2033-9
    Description: Recreational boating represents a major human use of inland waters in many regions. However, boating tourism may affect the ecological integrity of surface waters in multiple ways. In particular, surface waves produced by boating may disturb freshwater invertebrates, such as interrupting the filtration activity of benthic mussels. As mussels may significantly contribute to self-purification, disturbance may have crucial impacts on water quality, and thus on water tourism. In this paper we calculate the carrying capacity of a river section for sustainable boating tourism based on the preservation of water quality. This approach is complemented by spatial and social approaches for carrying capacity estimates. The ecological carrying capacity significantly decreases with lower water levels during summer. Hence, the analysis of variables that influence the river's carrying capacity allows the formation of recommendations for management measures that integrate social, touristic and ecological aspects.
    Keywords: Recreation ; Rivers ; Environmental Monitoring -- Methods
    ISSN: 0273-1223
    E-ISSN: 19969732
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  • 4
    In: Freshwater Biology, November 2014, Vol.59(11), pp.2400-2412
    Description: Coarse woody debris (CWD) in the littoral zone of lakes constitutes a preferred habitat for macroinvertebrates and fish. CWD differs in the surface complexity depending on its decay status. Therefore, CWD may provide distinct types of shelters and thus modify the structure of the macroinvertebrate community as well as its susceptibility to fish predation. We ran an enclosure experiment in a lake littoral zone to test the effect of surface complexity of CWD on the interactions between the predator, Eurasian perch (Perca fluviatilis) and its potential macroinvertebrate prey. We deployed 10 enclosures containing fresh wood with a smooth surface and 10 enclosures containing decayed wood with a more complex, rough surface and allowed colonisation by macroinvertebrates. Five enclosures of each type were then stocked by perch and exposed to fish predation. The abundance and biomass of macroinvertebrates were significantly higher on decayed wood with greater surface complexity than on fresh wood; however, the type of CWD did not strongly influence the taxonomic composition and diversity of invertebrates. The direct effect of perch predation on the macroinvertebrate community was weak. Perch reduced only the abundance of adult Dikerogammarus villosus, while other potential prey, such as chironomids, was more abundant in the presence of the fish. The impact of perch consumption of these larvae was probably obscured by interspecific interactions among chironomids and D. villosus, which were impaired in the fish enclosures. We found no clear evidence that the influence of perch on macroinvertebrates was mediated by the complexity of the wood surface. However, fish diet analysis showed that on decayed wood, perch preferentially consumed chironomids, and consumption of D. villosus was much lower, while on fresh wood, the preferential consumption of chironomids decreased with increasing consumption of gammarids. This suggests that such differences in fish diet could be an effect of complex interactions between wood microstructure, prey density and its ability to find refuge in CWD. The effect of CWD microstructure on predator–prey interactions was visible with respect to interspecific relationships between chironomids and gammarids, which on more complex decayed wood were moderated in the absence of perch.
    Keywords: Dikerogammarus Villosus ; Urasian Perch ; Habitat Complexity ; Littoral Zone ; Predator–Prey Interactions
    ISSN: 0046-5070
    E-ISSN: 1365-2427
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  • 5
    In: Journal of Applied Ecology, August 2013, Vol.50(4), pp.1010-1018
    Description: Beta diversity is the compositional heterogeneity of biotic assemblages among sites, and biotic homogenization is the decrease in beta diversity, facilitated by an increase in similarity of biotic communities over time. Environmental harshness decreases the importance of stochastic processes in structuring assemblages, resulting in a homogenization of the biota. We investigated if increasing nutrient enrichment, land‐use pressure, and within‐lake habitat alteration would decrease the beta diversity of macroinvertebrates in 46 lakes across Europe. Beta diversity was calculated using global multivariate dispersion. We utilized a structural equation modelling approach to account for hierarchical interdependence between potential impacts, that is the direct effects and correlations among the different impacts. We found clear indications that European macroinvertebrate communities are being homogenized by ongoing lake shore development. Increasing land‐use pressure in the form of residential and commercial development had a direct negative effect on beta diversity (standardized coefficient = −0·40), as did roadways, albeit indirectly through an increase in engineering structures (standardized coefficient = −0·31). Increasing within‐lake silt levels also homogenized macroinvertebrate communities (standardized coefficient = −0·18), independent of near shore land use. Our results indicate the negative effect of both the near shore land‐use pressure and the within‐lake habitat alteration on macroinvertebrate beta diversity, with significant interactions between these pressures. Habitat protection should take a more holistic approach to assessing lake development pressure, over a range of scales, as a solely site specific approach is not always biologically meaningful. Thus, future management plans should carefully control and mitigate ongoing development pressure if lake ecosystem health and resilience is to be maintained. Synthesis and applications. This study is the first of its kind to demonstrate European‐wide homogenization of littoral macroinvertebrate lake communities with increasing habitat alteration and land‐use pressure. Significant interactions occur between different habitat scales, with no one scale entirely accounting for the homogenization effect. To avoid further biotic homogenization, development pressure must be carefully managed at multiple scales, and where possible, minimized. This presents a challenge, as globally there is an increasing expansion of the human population and a consequent increase in anthropogenic pressure across all habitats. This study is the first of its kind to demonstrate European‐wide homogenization of littoral macroinvertebrate lake communities with increasing habitat alteration and land‐use pressure. Significant interactions occur between different habitat scales, with no one scale entirely accounting for the homogenization effect. To avoid further biotic homogenization, development pressure must be carefully managed at multiple scales, and where possible, minimized. This presents a challenge, as globally there is an increasing expansion of the human population and a consequent increase in anthropogenic pressure across all habitats.
    Keywords: Benthic Macroinvertebrates ; Beta Diversity ; Biotic Homogenization ; Habitat Modification ; Hydromorphology ; Lake ; Multivariate Dispersion ; Structural Equation Modelling
    ISSN: 0021-8901
    E-ISSN: 1365-2664
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  • 6
    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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  • 7
    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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  • 8
    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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  • 9
    In: Freshwater Biology, December 2014, Vol.59(12), pp.2571-2583
    Description: To evaluate the effects of large wood (LW) on benthic habitats and macroinvertebrates in sand‐bed lowland rivers, we compared invertebrate communities recorded on four pieces of LW (12 samples in total) and around them (60 samples) with those in four control sites in the same river (four samples). Mean flow velocity was 32% lower in the channel areas surrounding the LW than in control sites, while median sediment grain size was 50% higher, and the organic matter content of the riverbed sediments was 287% higher. At the same time, habitat conditions showed threefold to 1000‐fold increases in variance for five key abiotic habitat descriptors in the surrounding channel extending at least 60 cm upstream and 160 cm downstream of the LW. Three habitat patches typically occurred around the LW pieces: scouring pools, sand bars and accumulations of organic matter. These patches were colonised by distinctive invertebrate communities (e.g. accumulations of organic matter and gravel hosted 15 and 2 indicator taxa, respectively) that overall harboured 110% more taxa and exhibited a 168% higher diversity than control sites. The LW itself contributed only a small fraction to these increases, exhibiting a 15% increase in taxa richness and a 21% increase in species diversity compared to the control sites. The diversification of benthic invertebrate communities colonising streambed sediments around LW could be directly linked to the much more heterogeneous habitat conditions recorded there. Thus, local additions of large wood within river restoration programmes have the potential to promote the establishment of diverse invertebrate communities in extended areas of a river channel.
    Keywords: Diversity ; Hydromorphology ; Lowland River ; Mesohabitat ; Sediment
    ISSN: 0046-5070
    E-ISSN: 1365-2427
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  • 10
    Language: English
    In: Science of the Total Environment, 01 November 2012, Vol.438, pp.435-446
    Description: Dissolved organic matter (DOM) is an important part of the global carbon cycle and significantly influences aquatic ecosystem functions. Recent studies suggest that its amount and composition in freshwaters may be altered by agricultural land use, whereby the influence of preceding in-stream production and processing is not clear. To assess the land use effect on DOM amount and composition for the export from terrestrial to freshwater systems at the land–water interface, we sampled headwater streams draining agricultural and near-pristine catchments (forested and wetland) in the North German plains. To account for spatial and seasonal variation, we conducted a screening of DOM amount (53 sites) and composition (42 sites), and conducted bi-weekly samplings to investigate seasonal variation at eight sites over one year. Concentrations of dissolved organic carbon (DOC) were significantly higher for agricultural and wetland catchments than for forested catchments. Moreover, DOC loads exhibited higher seasonal variation for agricultural and wetland catchments than for forested catchments, which was due to higher variation in discharge. Parallel Factor Analysis revealed that the composition of DOM in agricultural catchments was significantly different from the other studied catchment types, and was characterized by low redox state and high structural complexity. Moreover, a gradient from protein- to humic-like fluorescence significantly separated forested from agricultural and wetland catchments. The contribution of humic-like DOM was strongly and positively related to DOC concentration, suggesting a mechanistic coupling of both. The effects of land use on patterns of DOC concentration and DOM composition were consistent across seasons, implying that land use strongly regulates DOM export. Overall, this study clearly shows the seasonally independent importance of agricultural land use for the amount and composition of DOM fluxes from the terrestrial zone to surface waters. These altered fluxes may affect ecosystem metabolism and health of agricultural headwaters and downstream situated aquatic ecosystems. ► Agriculture can be an important source of dissolved organic matter (DOM) to headwaters. ► Export of DOM from agriculture is structurally complex and exhibits a low redox state. ► Land-use related patterns of DOM amount and composition are consistent across seasons. ► In headwaters, the degree humification of DOM is strongly related to DOC concentration. ► Export of DOM from agriculture may affect metabolism and health of aquatic ecosystems.
    Keywords: Fluorescence ; Parallel Factor Analysis ; Seasonality ; Redox State ; Forest ; Wetland ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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