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2M - Monitoring of function and structure (WEP/143) Effects of pollutants on soil communities and organic matter decomposition: the use of terrestrial mesocosms. Pernin, Celine1, Cortet, Jérôme1, Krogh, Paul Henning2, Elmholt , Susanne3, Joffre, Richard4, 1 Institut Méditerannéen d'Ecologie et de Paléoécologie, Marseille, France2 National Environmental Research Institute, Silkeborg, Denmark3 Danish Institute of Agricultural Sciences, Tjele, Denmark4 Centre d'Ecologie Fonctionnelle et Evolutive, Montpellier, France ABSTRACT- In terrestrial ecotoxicology, it is usually suggested that a test battery, composed by several bioassays of different organisms from different trophic levels would reduce uncertainty (Bierkens et al, 1998). But interactions between species that occur in natural soils should be taken into account, as well as effects on functional parameters. Here, we present two laboratory studies which try to assess effects of contaminants at the community level. The first study concerns the effects of copper-enriched sludge on both soil mesofauna and decomposition of oak leaves in mesocosms. Two doses of sludge enriched with three doses of copper were studied over 3 months. The mesofauna community added on each mesocosm was composed by 6 species of Collembola, 2 species of Oribatida, 1 species of Gamasida and 1 species of Enchytraeida. Cork oak litter decomposition parameters (Litter Mass Remaining, nitrogen, fibres and phenol content) were monitored using the Near Infra-red Reflectance Spectroscopy method. Tripling the dose of sludge had a significant effect on the community and leaf nitrogen, fibres and phenol content but not on the Litter Mass Remaining. The second study concerns the effects of phenanthrene on various mesofauna compositions and wheat straw decomposition, over a period of 4 months. Five combinations of species within three trophic level were carried out and compared. Results show that effects of phenanthrene on some species, such as F. fimetaria, vary with the initial species composition of the mesocosms. However, even though phenanthrene stimulated decomposition, no interaction between initial mesofauna composition and phenanthrene on this decomposition was observed. The interest of multispecies mesocosms is discussed in the light of these studies. Key words: ecotoxicology, mesocosm, soil communities, organic matter decomposition |
