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Mitchell, Edward

Nom
Mitchell, Edward
Affiliation principale
Site web
Fonction
Professeur ordinaire
Email
edward.mitchell@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/357
_
0000-0003-0358-506X

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  • Publication
    Accès libre
    Effect of lead pollution on testate amoebae communities living in Sphagnum fallax: An experimental study
    (2008)
    Nguyen Viet, Hung
    ;
    Bernard, Nadine
    ;
    Mitchell, Edward 
    ;
    Badot, Pierre-Marie
    ;
    Gilbert, Daniel
    We studied the effects of lead pollution on testate amoebae communities living on Sphagnum fallax by growing this moss under controlled conditions. A progressive series of lead (Pb) concentration was used in the growing solution of the mosses: 0 (control), 625 and 2500 μg L−1. The mosses were sampled and analysed for accumulated Pb and testate amoeba communities after 0, 6, 12, and 20 weeks. Species richness, total density and total biomass of testate amoebae declined in response to the Pb treatment and changed over time. The Pb×Time cross-effect was significant for species richness, and total density but not for the total biomass and Shannon diversity. Furthermore, the testate amoebae species richness and the total density were negatively correlated to the Pb concentrations actually accumulated in the moss at the end of the experiment. Species-specific responses of testate amoebae to Pb pollution were identified. Our results thus confirm the sensitivity of testate amoebae to lead pollution.
  • Publication
    Accès libre
    Taxonomic and functional traits responses of Sphagnum peatland testate amoebae to experimentally manipulated water table
    Koenig, Isabelle 
    ;
    Mulot, Matthieu, Laboratory of Soil Diversity, University of Neuchâtel, Switzerland
    ;
    Mitchell, Edward 
    Biomonitoring tools are useful to assess the impact of environmental changes on the functioning of ecosystems. Existing tools mostly require species identification, thus allowing to estimating changes in biodiversity, and possibly inferring ecosystem functioning, using functional diversity and traits based approaches.
    Testate amoebae are good indicators of surface moisture conditions in Sphagnum peatlands and are routinely used in palaeoecology. Their shells (tests), on which identification is based, can also be used to define functional traits and thus to infer changes in ecosystem functioning.
    We investigated the response of testate amoeba communities to manipulated water table depth (wet: −4 cm, intermediate: −15 cm, and dry: −25 cm) over time (seven time points, 19 months) using mesocosms by comparing two approaches: community structure and functional traits responses, using a combination of morphological (biovolume, length, aperture size and position) and physiological (mixotrophy/heterotrophy, shell material) traits.
    This is the first study investigating the effect of water table depth on testate amoeba assemblages over time using a mesocosm approach. Taxonomical and functional approaches showed similar response patterns, confirming that water level acted as a strong environmental filter. After one year Hyalosphenia papilio decreased in the dry treatment, and the community structure shifted towards a dominance of dry indicators (Nebela tincta complex, Corythion dubium, Euglypha compressa) and the selected functional traits (smaller, heterotrophic, compressed species, with a ventral aperture) corresponded to drought adaptations.
    In line with recent observational and transfer function studies exploring the use of testate amoebae functional traits, our experimental results illustrate how well-selected traits could be used to monitor the impact of present and past climatic changes on Sphagnum peatlands.