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  • Walz, Norbert  (6)
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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
    In: Freshwater Biology, June 2007, Vol.52(6), pp.1022-1032
    Description: 1. Nutrient inputs from urban and agricultural land use often result in shifts in species composition of pelagic and profundal invertebrate communities. Here, we test if nutrient enrichment affects the composition of eulittoral macroinvertebrate communities, and, if so, if macroinvertebrate communities of five different habitat types reflect differences in trophic state. 2. Macroinvertebrate community composition of 36 lakes was significantly correlated with total phosphorus (TP) concentration, the proportion of coarse woody debris (CWD) and root habitats and the proportion of grassland. 3. However, macroinvertebrate communities of five major habitat types from eight lakes were more dissimilar among habitats than among trophic states. Community composition of reed and stone habitats was significantly correlated with wind exposure but not TP concentration, while macroinvertebrate composition of sand habitats was related to TP concentration and coarse sediments. In CWD and root habitats, both TP concentration and a predominance of invasive species covaried, which made it difficult to relate the observed compositional differences to either trophic state or to the effects of competition between native and invasive species. 4. Trophic state influenced the composition of eulittoral macroinvertebrate communities but to a lesser extent than has been previously reported for profundal habitats. Moreover, the effects of trophic state were nested within habitat type and were partially superseded by biotic interactions and small‐scaled habitat complexity. Although eulittoral macroinvertebrate communities were not strong indicators of the trophic state of lowland lakes, they may be used to assess other anthropogenic impacts on lakeshores.
    Keywords: Eutrophication ; Habitat ; Invasive Species ; Lakeshore ; Land Use
    ISSN: 0046-5070
    E-ISSN: 1365-2427
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  • 4
    In: Journal of Applied Ecology, December 2007, Vol.44(6), pp.1138-1144
    Description: 1 The shores of many lakes have been substantially altered by human developments such as erosion control structures or recreational beaches. Such alterations are likely to increase in the future, yet almost nothing is known about their impacts on the littoral macroinvertebrate community. 2 Macroinvertebrates were studied in seven German lowland lakes exhibiting natural shorelines (reference), retaining walls, ripraps and recreational beaches to examine impacts on the eulittoral (0–0·2 m water depth) and infralittoral (0·2–1·2 m water depth) communities associated with the three types of shoreline development. 3 Among sites, eulittoral species richness and abundance of Coleoptera, Gastropoda, Trichoptera, shredders and xylophagous species were lowest on beaches and retaining walls but ripraps did not differ significantly from natural shorelines. Retaining walls and ripraps had no significant impact on the infralittoral macroinvertebrate community. Conversely, beaches had significantly lower infralittoral species richness and abundance of Ephemeroptera, Trichoptera and shredders than natural shorelines. Furthermore, species richness was correlated positively with habitat heterogeneity expressed as number of habitat types. 4 Among lakes, whole‐lake littoral macroinvertebrate density increased with increasing proportion of developed shorelines due to increasing abundances of Chironomidae. The remaining macroinvertebrate major groups decreased with increasing proportion of shoreline development. 5 Synthesis and applications. The biological impacts of shoreline development in lowland lakes depend upon the extent to which structural complexity and heterogeneity of littoral habitats are reduced. Hence, we recommend that management programmes focus upon the conservation of littoral habitat complexity and habitat heterogeneity. The biological effects of shoreline development may be assessed efficiently by combining an assessment of the morphological status of lakeshores and information on macroinvertebrate indicator species with a defined response to the loss of their preferred habitats.
    Keywords: Biodiversity ; Coarse Woody Debris ; Habitat Complexity ; Lake Management ; Macrophytes ; Recreational Beaches ; Retaining Walls ; Riparian Clearcutting ; Ripraps
    ISSN: 0021-8901
    E-ISSN: 1365-2664
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  • 5
    Language: German
    In: Umweltwissenschaften und Schadstoff-Forschung, 2004, Vol.16(2), pp.113-114
    Description: Die Beitragsserie ‘Seeufer, ein vergessenes Ökoton’, wird ergänzt durch einen persönlichen Bericht von der ersten Seeuferkonferenz, veranstaltet in Konstanz (Beitrag 4). Von den fünf während der Konferenz behandelten Themenblöcken werden die drei ersten ausführlicher behandelt, da diese sich weitestgehend mit der Modellierung und mathematisch-theoretischen Bearbeitung des Seeufers befassen. Im ersten Themenblock wurden vornehmlich die hydrophysikalischen Prozesse behandelt, im zweiten stand die phänomenologische Erfassung von Seeuferbeeinträchtigungen, im dritten die Bewertung des ökologischen Zustands im Vordergrund. Gegenstand von Themenblock 4 waren Möglichkeiten der Uferrenaturierung bzw. des Uferschutzes. Themenblock 5 beschäftigte sich mit der nachhaltigen Entwicklung der Seeufer und zeigte neue Möglichkeiten der Nutzung und Bewertung auf. This report of an international conference about the problems around lakeshores, their evaluation and the possibilities to improve the situation for lake shores, continues the series ‘Lake shores, a forgotten ecotone’ as article 4. Five main topics were discussed: (1) applied ecology of lakeshores, (2) human impact, (3) ecological assessment, (4) protection and restoration, (5) sustainable development and use of lake shores.
    Keywords: Assessment ; hydrophysical processes ; lake shores ; sustainability
    ISSN: 0934-3504
    E-ISSN: 1865-5084
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  • 6
    Language: German
    In: Umweltwissenschaften und Schadstoff-Forschung, 2004, Vol.16(1), pp.48-56
    Description: Die EU-Wasserrahmenrichtlinie (EU-WRRL) fordert eine holistische Herangehensweise in Maßnahmen zur Gewässergüteverbesserung Mit der Forderung nach ’mehr Ökologie’ ist die Anwendung von Biodiversitätsindices naheliegend. Will man Biodiversitätsindices verwenden, um Vergleiche durchzuführen, so stellt sich die Frage, ob ein Ranking anhand eines ’Biodiversitätindex unabhängig von der speziellen Wahl des Index ist. Leider ist dies nicht der Fall. Konzepte zur Auflösung des Dilemmas werden aufgezeigt und eine graphische Technik eingesetzt, die bisher nur in der Quantenmechanik, statistischen Mechanik und in der Theoretischen Chemie angewender wurde: Die Technik der YOUNG-Diagramme. Within the context of the EU Water Framework Directive (EUWFD), there is a demand for a holistic quality improvement of aquatic systems. Therefore, it is obvious that biodiversity is one of the quality components and hence has to be considered in detail. The ranking of habitats, based on biodiversity indices, depends on the specific measurement selected. It is postulated that a ranking of habitats by means of a biodiversity index may be ambiguous. Concepts to resolve this dilemma are demonstrated, and a graphical formalism is introduced which up to now has only been used in quantum mechanics, statistical mechanics, and theoretical chemistry: The YOUNG-diagram technique.
    Keywords: Areas of protection ; biodiversity ; ecotones ; EU Water Frame work Directive (EU-WFD) ; Lake Constance ; lake shores ; order theory ; YOUNG-Diagrams
    ISSN: 0934-3504
    E-ISSN: 1865-5084
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