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  • 1.
    Hansen, Joan H.
    et al.
    Technical University of Denmark.
    Skov, Christian
    Technical University of Denmark.
    Baktoft, Henrik
    Technical University of Denmark.
    Brönmark, Christer
    Lund University.
    Chapman, Ben B.
    University of Manchester.
    Hulthén, Kaj
    Lund University.
    Hansson, Lars-Anders
    Lund University.
    Nilsson, Per Anders
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013). Lund University.
    Brodersen, Jakob
    EAWAG Swiss Federal Institute of Aquatic Science and Technology, University of Bern.
    Ecological consequences of animal migration: Prey partial migration affects predator ecology and prey communities2019In: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, p. 1-15Article in journal (Refereed)
    Abstract [en]

    Patterns of animal migration and the ecological forces that shape them have been studied for centuries. Yet ecological impacts caused by the migration, such as altered predator–prey interactions and effects on community structure, remain poorly understood. This is to a large extent due to the scarcity of naturally replicated migration systems with negative controls, that is, ecosystems without migration. In this study, we tested whether partial migration of certain species within the overall prey community affects foraging ecology of top predators and thereby alters energy pathways in food webs. We carried out the study in independent replicated freshwater lake systems, four with and four without opportunity for prey migration. Specifically, we compared predator foraging mode in lakes where cyprinid prey fish perform seasonal partial migrations into connected streams with lakes lacking migratory opportunities for prey fish. We found clear seasonal bottom-up effects of prey migration on predators, including changes in size structure and total biomass of ingested prey, size-specific changes in littoral versus pelagic origin of diet, and a higher degree of feast-and-famine for predators in systems with migratory prey. Our analyses further showed that partially migratory prey species constitute a larger part of the prey community in systems that allow migration. Hence, prey migrations have important implications for predator foraging ecology and may cause seasonal shifts in the importance of their supporting energy pathways. We suggest that such bottom-up effects of partial migration may be a widespread phenomenon both in aquatic and in terrestrial ecosystems. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.

  • 2.
    Nilsson, Christer
    et al.
    Umeå University, Umeå, Sweden.
    Jansson, Roland
    Umeå University, Umeå, Sweden.
    Kuglerova, Lenka
    Umeå University, Umeå, Sweden.
    Lind, Lovisa
    Umeå University, Umeå, Sweden.
    Ström, Lotta
    Umeå University, Umeå, Sweden.
    Boreal riparian vegetation under climate change2013In: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 16, no 3, p. 401-410Article in journal (Refereed)
    Abstract [en]

    Riparian zones in boreal areas such as humid landscapes on minerogenic soils are characterized by diverse, productive, and dynamic vegetation which will rapidly react to climate change. Climate-change models predict that in most parts of the boreal region these zones will be affected by various combinations of increased temperature, less seasonal variation in runoff, increased average discharge, changes in groundwater supply, and a more dynamic ice regime. Increasing temperatures will favor invasion of exotic species whereas species losses are likely to be minor. The hydrologic changes will cause a narrowing of the riparian zone and, therefore, locally reduce species richness whereas effects on primary production are more difficult to predict. More shifts between freezing and thawing during winter will lead to increased dynamics of ice formation and ice disturbance, potentially fostering a more dynamic and species-rich riparian vegetation. Restoration measures that increase water retention and shade, and that reduce habitats for exotic plant species adjacent to rivers can be applied especially in streams and rivers that have been channelized or deprived of their riparian forest to reduce the effects of climate change on riparian ecosystems.

  • 3.
    Nilsson, Christer
    et al.
    Umeå University, Umeå, Sweden.
    Sarneel, Judith M.
    Umeå University, Umeå, Sweden; Utrecht UniversityUtrechtThe Netherlands.
    Palm, Daniel
    Umeå University, Umeå, Sweden.
    Gardeström, Johanna
    Umeå University, Umeå, Sweden.
    Pilotto, Francesca
    Umeå University, Umeå, Sweden.
    Polvi, Lina E.
    Umeå University, Umeå, Sweden.
    Lind, Lovisa
    Umeå University, Umeå, Sweden.
    Holmqvist, Daniel
    Utrecht University, Utrecht, The Netherlands.
    Lundqvist, Hans
    Ume/Vindel River Fishery Advisory BoardLyckseleSweden.
    How do biota respond to additional physical restoration of restored streams?2017In: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 20, no 1, p. 144-162Article in journal (Refereed)
    Abstract [en]

    Restoration of channelized streams by returning coarse sediment from stream edges to the wetted channel has become a common practice in Sweden. Yet, restoration activities do not always result in the return of desired biota. This study evaluated a restoration project in the Vindel River in northern Sweden in which practitioners further increased channel complexity of previously restored stream reaches by placing very large boulders (> 1 m), trees (> 8 m), and salmonid spawning gravel from adjacent upland areas into the channels. One reach restored with basic methods and another with enhanced methods were selected in each of ten different tributaries to the main channel. Geomorphic and hydraulic complexity was enhanced but the chemical composition of riparian soils and the communities of riparian plants and fish did not exhibit any clear responses to the enhanced restoration measures during the first 5 years compared to reaches restored with basic restoration methods. The variation in the collected data was among streams instead of between types of restored reaches. We conclude that restoration is a disturbance in itself, that immigration potential varies across landscapes, and that biotic recovery processes in boreal river systems are slow. We suggest that enhanced restoration has to apply a catchment-scale approach accounting for connectivity and availability of source populations, and that low-intensity monitoring has to be performed over several decades to evaluate restoration outcomes.

  • 4.
    Thorp, James H.
    et al.
    Kansas Biological Survey and Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, USA.
    Bowes, Rachel E.
    Kansas Biological Survey and Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, USA.
    Carbon Sources in Riverine Food Webs: New Evidence from Amino Acid Isotope Techniques2017In: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Ecosystems, Vol. 20, no 5, p. 1029-1041Article in journal (Refereed)
    Abstract [en]

    A nearly 40-year debate on the origins of carbon supporting animal production in lotic systems has spawned numerous conceptual theories emphasizing the importance of autochthonous carbon, terrestrial carbon, or both (depending on river stage height). Testing theories has been hampered by lack of adequate analytical methods to distinguish in consumer tissue between ultimate autochthonous and allochthonous carbon. Investigators initially relied on assimilation efficiencies of gut contents and later on bulk tissue stable isotope analysis or fatty acid methods. The newest technique in amino acid, compound specific, stable isotope analysis (AA-CSIA), however, enables investigators to link consumers to food sources by tracing essential amino acids from producers to consumers. We used AA-CSIA to evaluate nutrient sources for 5 invertivorous and 6 piscivorous species in 2 hydrogeomorphically contrasting large rivers: the anastomosing Upper Mississippi River (UMR) and the mostly constricted lower Ohio River (LOR). Museum specimens we analyzed isotopically had been collected by other investigators over many decades (UMR: 1900–1969; LOR: 1931–1970). Our results demonstrate that on average algae contributed 58.5% (LOR) to 75.6% (UMR) of fish diets. The next highest estimated contributions of food sources were from C3 terrestrial plants (21.1 and 11.5% for the LOR and UMR, respectively). Moreover, results from 11 individually examined species consistently demonstrated the importance of algae for most fish species in these trophic guilds. Differences among rivers in relative food source availability resulting from contrasting hydrogeomorphic complexity may account for relative proportions of amino acids derived from algae.

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