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Influence de la structure des réseaux trophiques lacustres et des apports de matière organique sur la composition biochimique des compartiments biotiques et sur la biodégradabilité de la matière organique sédimentée

Abstract : Within lakes, carbon and nutrient cycles are partly controlled by sedimentation, allochthonous inputs, food-web structure and interactions between these compartments and/or processes. As sources of organic matter and nutrients for aquatic ecosystems, sediments and terrestrial materials can exert a bottom-up forcing on pelagic communities. Top-predators control carbon and nutrient transfers within aquatic food webs, which changes the sedimentation process and nutrient cycles. This study showed that the indirect control exerted by predators on primary producers changed the stoichiometry and the biochemical composition (polyunsaturated fatty acids, sterols, chlorophyll degradation products, proteins and sugars), and the biodegradability of recently sedimented organic matter through a trophic cascade. These modifications of sediment biodegradability led to a bottom-up forcing on seston, zooplankton and fish biomass. Autochthonous and allochthonous organic matters used in this study had contrasted effects on the stoichiometry of seston, zooplankton and recently deposited sediment but weak effects on their composition of lipid biomarkers. Finally, bottom-up effects induced by organic matter inputs, as sediment or soil, on pelagic compartments seemed minor compared to the top-down effects induced by the trophic cascade.
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https://tel.archives-ouvertes.fr/tel-00831080
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Submitted on : Thursday, June 6, 2013 - 2:12:26 PM
Last modification on : Friday, August 5, 2022 - 2:38:10 PM
Long-term archiving on: : Saturday, September 7, 2013 - 4:10:48 AM

Identifiers

  • HAL Id : tel-00831080, version 1
  • PRODINRA : 315778

Citation

Loïc Harrault. Influence de la structure des réseaux trophiques lacustres et des apports de matière organique sur la composition biochimique des compartiments biotiques et sur la biodégradabilité de la matière organique sédimentée. Géochimie. Université Pierre et Marie Curie - Paris VI, 2012. Français. ⟨NNT : 2012PA066206⟩. ⟨tel-00831080⟩

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