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Communication Dans Un Congrès Année : 2011

Influence of temperature on food webs in temperate streams: a stable isotope study

Influence de la température sur les réseaux trophiques de cours d'eau tempérés : étude par l'analyse des isotopes stables

Résumé

Trophic interactions are essential to address functional biodiversity. Concerning stream ecosystems, three major non-exclusive hypotheses are put forward to explain variations of food web organisation and complexity; i.e. ecosystem size, energy supply and environmental stability. Recent studies have confirmed that environmental stability plays a key role in determining food web structure, addressing this issue in terms of discharge variation or river bed stability. Here, we report on how thermal conditions and stability influence food webs of temperate streams, a question poorly dealt with until now. Using nitrogen and carbon stable isotope analyses we studied food webs across a hydro-geological gradient (from spring-fed to runoffdominated systems) in five sites located in five different streams of one small watershed (Bez River Basin, France, 275 km²). This ensured that the studied sites were quite homogenous concerning most environmental conditions (climate, land use, river morphology, composition of invertebrates and fish communities) while exhibiting large discrepancies in terms of thermal patterns (annual temperature range varied from 6 to 20 °C between sites). Our results suggested that despite these significant thermal differences the general structure of the food webs was very similar between sites. On the other hand, the food chain length (FCL) increased significantly from 3.4 (at a runoff-dominated site with high temperature variability) to 3.8 (at a springfed site with narrow temperature range). In addition to previous studies, which focus on discharge variations, this result provides a thermal evidence for the positive influence of environmental stability on FCL. Further work is still needed to understand the underlying mechanisms that explain the link between temperature stability and FCL increase. However, these results provide a first insight into the potential impact of global warming on ecosystem functioning, as climate change is likely to increase the temperature variability of numerous temperate streams.

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Dates et versions

hal-02598302 , version 1 (15-05-2020)

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Nicolas Hette-Tronquart, Bernard Dumont, Didier Pont, Jean-Marc Roussel, Thierry Oberdorff, et al.. Influence of temperature on food webs in temperate streams: a stable isotope study. 7th Symposium for European Freshwater Sciences, Jun 2011, Girona, Spain. pp.32. ⟨hal-02598302⟩
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