Browsing by Subject "FISH ASSEMBLAGES"

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  • Poikane, Sandra; Birk, Sebastian; Boehmer, Juergen; Carvalho, Laurence; de Hoyos, Caridad; Gassner, Hubert; Hellsten, Seppo; Kelly, Martyn; Solheim, Anne Lyche; Olin, Mikko; Pall, Karin; Phillips, Geoff; Portielje, Rob; Ritterbusch, David; Sandin, Leonard; Schartau, Ann-Kristin; Solimini, Angelo G.; van den Berg, Marcel; Wolfram, Georg; van de Bund, Wouter (2015)
    The Water Framework Directive is the first international legislation to require European countries to establish comparable ecological assessment schemes for their freshwaters. A key element in harmonising quality classification within and between Europe's river basins is an "Intercalibration" exercise, stipulated by the WFD, to ensure that the good status boundaries in all of the biological assessment methods correspond to similar levels of anthropogenic pressure. In this article, we provide a comprehensive overview of this international comparison, focusing on the assessment schemes developed for freshwater lakes. Out of 82 lake ecological assessment methods reported for the comparison, 62 were successfully intercalibrated and included in the EC Decision on intercalibration, with a high proportion of phytoplankton (18), macrophyte (17) and benthic fauna (13) assessment methods. All the lake assessment methods are reviewed in this article, including the results of intercalibration. Furthermore, the current gaps and way forward to reach consistent management objectives for European lakes are discussed. (C) 2015 The Authors. Published by Elsevier Ltd.
  • Nummi, Petri; Liao, Wenfei; van der Schoor, Juliette; Loehr, John (2021)
    Beavers (Castor spp.) are ecosystem engineers that induce local disturbance and ecological succession, which turns terrestrial into aquatic ecosystems and creates habitat heterogeneity in a landscape. Beavers have been proposed as a tool for biodiversity conservation and ecosystem restoration. So far, most research has compared biodiversity in beaver wetlands and non-beaver wetlands, but few studies have explored how beaver-created succession affects specific taxa. In this study, we investigated how water beetles responded to different successional stages of wetlands in a beaver-disturbed landscape at Evo in southern Finland. We sampled water beetles with 1-L activity traps in 20 ponds, including: 5 new beaver ponds, 5 old beaver ponds, 5 former beaver ponds, and 5 never engineered ponds. We found that beaver wetlands had higher species richness and abundance than non-beaver wetlands, and that new beaver wetlands could support higher species richness (321%) and abundance (671%) of water beetles compared to old beaver wetlands. We think that higher water beetle diversity in new beaver ponds has resulted from habitat amelioration (available lentic water, shallow shores, aquatic vegetation, and low fish abundance) and food source enhancement (an increase of both dead and live prey) created by beaver dams and floods. We conclude that using beavers as a tool, or imitating their way of flooding, can be beneficial in wetland restoration if beaver population densities are monitored to ensure the availability of newly colonizable sites.
  • Kivinen, Sonja; Nummi, Petri; Kumpula, Timo (2020)
    Beavers (Castorsp.) are ecosystem engineers that cause significant changes to their physical environment and alter the availability of resources to other species. We studied flood dynamics created by American beaver (C. canadensisK.) in a southern boreal landscape in Finland in 1970-2018. We present for the first time, to our knowledge, a temporally continuous long-term study of beaver-induced flood disturbances starting from the appearance of beaver in the area. During the 49 years, the emergence of new sites flooded by beaver and repeated floods (61% of the sites) formed a dynamic mosaic characterized by clustered patterns of beaver sites. As beaver dispersal proceeded, connectivity of beaver sites increased significantly. The mean flood duration was approximately three years, which highlights the importance of datasets with high-temporal resolution in detecting beaver-induced disturbances. An individual site was often part of the active flood mosaic over several decades, although the duration and the number of repeated floods at different sites varied considerably. Variation of flood-inundated and post-flood phases at individual sites resulted in a cumulative number of unique patches that contribute to environmental heterogeneity in space and time. A disturbance mosaic consisting of patches differing by successional age and flood history is likely to support species richness and abundance of different taxa and facilitate whole species communities. Beavers are thus a suitable means to be used in restoration of riparian habitat due to their strong and dynamic influence on abiotic environment and its biotic consequences.