Predator–prey mass ratio drives microbial activity under dry conditions in Sphagnum peatlands |
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| Authors: | Monika K Reczuga Mariusz Lamentowicz Matthieu Mulot Edward A D Mitchell Alexandre Buttler Bogdan Chojnicki Micha? S?owiński Philippe Binet Geneviève Chiapusio Daniel Gilbert Sandra S?owińska Vincent E J Jassey |
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| Institution: | 1. Laboratory of Wetland Ecology and Monitoring, Faculty of Geographical and Geological Sciences, Adam Mickiewicz University, Poznań, Poland;2. Department of Biogeography and Palaeoecology, Faculty of Geographical and Geological Sciences, Adam Mickiewicz University, Poznań, Poland;3. Faculty of Biology, Adam Mickiewicz University, Poznań, Poland;4. Laboratory of Soil Biodiversity, University of Neuchatel, Neuchatel, Switzerland;5. Jardin Botanique de Neuchatel, Neuchatel, Switzerland;6. Swiss Federal Research Institute, WSL Site Lausanne, Lausanne, Switzerland;7. Laboratoire des Systèmes écologiques, School of Architecture, Civil and Environmental Engineering, école Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland;8. Laboratoire de Chrono‐Environnement, UMR CNRS 6249, UFR des Sciences et Techniques, Université de Franche‐Comté, Besan?on, France;9. Department of Meteorology, Faculty of Environmental Engineering and Spatial Management, Poznan University of Life Sciences, 60‐649 Poznań, Poland;10. Department of Environmental Resources and Geohazard, Polish Academy of Sciences, Institute of Geography and Spatial Organization, Warszawa, Poland;11. UMR CARRTEL INRA 042 University of Savoie Mont‐Blanc, FR‐ 73376 Le Bourget du lac, France;12. Department of Geoecology and Climatology, Polish Academy of Sciences, Institute of Geography and Spatial Organization, Warsaw, Poland;13. Laboratoire d'Ecologie Fonctionnelle et Environnement (Ecolab), INPT, UPS, CNRS, Université de Toulouse, Toulouse Cedex, France |
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| Abstract: | Mid‐ to high‐latitude peatlands are a major terrestrial carbon stock but become carbon sources during droughts, which are increasingly frequent as a result of climate warming. A critical question within this context is the sensitivity to drought of peatland microbial food webs. Microbiota drive key ecological and biogeochemical processes, but their response to drought is likely to impact these processes. Peatland food webs have, however, been little studied, especially the response of microbial predators. We studied the response of microbial predators (testate amoebae, ciliates, rotifers, and nematodes) living in Sphagnum moss carpet to droughts, and their influence on lower trophic levels and on related microbial enzyme activity. We assessed the impact of reduced water availability on microbial predators in two peatlands using experimental (Linje mire, Poland) and natural (Forbonnet mire, France) water level gradients, reflecting a sudden change in moisture regime (Linje), and a typically drier environment (Forbonnet). The sensitivity of different microbial groups to drought was size dependent; large sized microbiota such as testate amoebae declined most under dry conditions (?41% in Forbonnet and ?80% in Linje). These shifts caused a decrease in the predator–prey mass ratio (PPMR). We related microbial enzymatic activity to PPMR; we found that a decrease in PPMR can have divergent effects on microbial enzymatic activity. In a community adapted to drier conditions, decreasing PPMR stimulated microbial enzyme activity, while in extreme drought experiment, it reduced microbial activity. These results suggest that microbial enzymatic activity resulting from food web structure is optimal only within a certain range of PPMR, and that different trophic mechanisms are involved in the response of peatlands to droughts. Our findings confirm the importance of large microbial consumers living at the surface of peatlands on the functioning of peatlands, and illustrate their value as early warning indicators of change. |
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| Keywords: | body size drought food web phenoloxidase poor fen protists soil moisture water table manipulation Wetlands |
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