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  • 1.
    Bastviken, D. T. E.
    et al.
    Uppsala University.
    Caraco, N. F.
    Uppsala University.
    Cole, J. J.
    of Ecosystem Studies, Millbrook.
    Experimental measurements of zebra mussel (Dreissena polymorpha) impacts on phytoplankton community composition1998Ingår i: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 39, nr 2, s. 375-386Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    1. To investigate direct effects of zebra mussel (Dreissena polymorpha) feeding activities on phytoplankton community composition, short-term microcosm experiments were performed in natural water with complex phytoplankton communities. Both gross effects (without resuspension of mussel excretions) and net effects (with resuspension) were studied. 2. Gross clearance rates were not selective; essentially all taxa were removed at similar rates ranging from 24 to 63 mt mussel(-1) h(-1). Net clearance rates were highly selective; different plankton taxa were removed at very different rates, ranging from 12 to 83% of the gross rates, leading to consistent changes in the phytoplankton community composition. Thus, although zebra mussels can cause most phytoplankton to decline, there is considerable variation among taxa in either pre-digestive selection or post-digestive survival. 3. The direct, short-term effects of zebra mussels on phytoplankton community composition are consistent with some of the major changes observed in the Hudson River since establishment of zebra mussels. 4. We show, with simple calculations, how zebra mussel filtration rate, its selective efficiency on various taxa, and phytoplankton growth rates interact to produce changes in the phytoplankton composition.

  • 2.
    Fischer, Helmut
    et al.
    Limnology/Department of Ecology and Evolution, Uppsala University, Sweden.
    Bergfur, Jenny
    Department of Aquatic Sciences, Swedish Agricultural University, Sweden.
    Goedkoop, Willem
    Department of Aquatic Sciences, Swedish Agricultural University, Sweden.
    Tranvik, Lars
    Limnology/Department of Ecology and Evolution, Uppsala University, Sweden.
    Microbial leaf degraders in boreal streams: bringing together stochastic and deterministic regulators ofcommunity composition2009Ingår i: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 54, s. 2276-2289Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    1. Leaves that fall into the water represent a new habitat for microorganisms to colonise in streams, providing an opportunity to study colonisation and the subsequent regulation of community structure. We explored community composition of bacteria and fungi on decomposing alder leaves in nine streams in central Sweden, and describe their relationship with environmental variables. Succession of the microbial community was studied in one of the streams for 118 days. Microbial community composition was examined by denaturing gradient gel electrophoresis on replicate samples of leaves from each stream.

    2. During succession in one stream, maximum taxon richness was reached after 34 days for bacteria and 20 days for fungi respectively. Replicate samples within this stream differed between each other earlier in colonisation, while subsequently such variation among replicate communities was low and remained stable for several weeks. Replicate samples taken from all the nine streams after 34 days of succession showed striking similarities in microbial communities within-streams, although communities differed more strongly between streams.

    3. Canonical analysis of microbial communities and environmental variables revealed that water chemistry had a significant influence on community composition. This influence was superimposed on a statistical relationship between the properties of stream catchments and microbial community composition.

    4. The catchment regulates microbial communities in two different ways. It harbours the species pool from which the in-stream microbial community is drawn and it governs stream chemistry and the composition of organic substrates that further shape the communities. We suggest that there is a random element to colonisation early in succession, whereas other factors such as species interactions, stream chemistry and organic substrate properties, result in a more deterministic regulation of communities during later stages.

  • 3.
    Setzer, Malin
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Norrgård, Johnny R,
    Management and Ecology of River Resources, Department of Biology, Karlstad University, Karlstad, Sweden.
    Jonsson, Tomas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska högskolan.
    An invasive crayfish affects egg survival and the potential recovery of an endangered population of Arctic charr2011Ingår i: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 56, nr 12, s. 2543-2553Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    1.Many fish stocks have declined, because of overharvesting, habitat destruction and introduced species. Despite efforts to rehabilitate some of these stocks, not all are responding or are recovering only slowly.

    2.In freshwater systems, introduced crayfish are often problematic, and it has been suggested that their egg predation could reduce recruitment in depleted stocks of native fish.

    3.Here, we report the results of a field experiment, using experimental cages, on the extent of predation on eggs of great Arctic charr (Salvelinus umbla) in Lake Vättern, Europe's fifth largest lake. Here, the great Arctic charr has declined dramatically and is listed as critically endangered.

    4.We were able to partition the total loss rate of eggs into background mortality, predation by introduced signal crayfish (Pacifastacus leniusculus) and predation by native fish. The mortality rate of charr eggs because of crayfish was estimated at more than five times that because of native fish. Of the total loss of eggs, 80% is believed to be caused by crayfish and 14% by fish, with 6% being natural background mortality.

    5.In a worst case scenario, our data infer that only 25% of the original number of eggs would survive, compared with 75% in the absence of crayfish. This could impair recovery of the stock of the endangered great Arctic charr in Lake Vättern. 6.Contrary to earlier claims that crayfish predation on eggs of great Arctic charr is insignificant, our results indicate that crayfish predation may exceed fish predation and suggest that the abundance of signal crayfish on the spawning sites of great Arctic charr should be managed.

  • 4.
    van Hardenbroek, M
    et al.
    University of Bern.
    Lotter, A F
    University of Utrecht.
    Bastviken, David
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Duc, N T
    Stockholm University.
    Heiri, O
    University of Bern.
    Relationship between d13C of chironomid remains and methane flux in Swedish lakes2012Ingår i: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 57, nr 1, s. 166-177Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    1. Methanogenic carbon can be incorporated by methane-oxidising bacteria, leading to a 13C-depleted stable carbon isotopic composition (d13C) of chironomids that feed on these microorganisms. This has been shown for the chironomid tribe Chironomini, but very little information is available about the d13C of other abundant chironomid groups and the relationship between chironomid d13C and methane production in lakes.

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