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Theses

Trajectoire de restauration des marais intertidaux : réponse du necton à la dépoldérisation dans l’estuaire de la Gironde

Abstract : European intertidal marshes have greatly declined during the past centuries because of land claim andhave recently been threatened by the effects of climate change. In recent years, an increasing number of tidal resto-ration projects have been implemented, following a global trend termed de-embankment. This thesis describes therestoration trajectory of tidally restored marshes from the response of nekton (i.e., fish and decapod crustaceans)based on two storm-breached study sites in the Gironde estuary : the Mortagne marsh and the Nouvelle island.Nekton assemblage composition of tidally restored marshes was described through a whole-estuary approach en-compassing natural, restored and dyked habitats. Nekton assemblages of tidally restored marshes showed highcompositional similarity with natural intertidal habitats and greatly departed from dyked marshes. Dyked marsheswere characterized by high occurrence of freshwater exotic taxa. Tidally restored marshes seemed particularly at-tractive for the thin-lipped grey mullet, Liza ramada. The functional traits’ distribution within fish communities revealeda change in functional structure in the course of restoration using the naturalness state of habitats as a proxy forrestoration time. Most notably, functional specialization, dispersion and richness increased with restoration time.No clear pattern of change was observed in community assembly over time ; trends chiefly varied with respect totraits. Temporal trends in one of the restored sites revealed three phases in the first four years of tide restoration.The abundance of several species and the community functional structure changed more steeply in the midst ofthe second phase, less than two years following tide restoration. Community turnover was probably delayed dueto incomplete drainage of the site in the early stages of restoration. The results of this thesis lead to a better un-derstanding of the restoration trajectory of tidal marshes without human intervention and highlight the strengths andweaknesses of some theoretical models used in restoration ecology.
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  • HAL Id : tel-01717327, version 1
  • IRSTEA : PUB00056381

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Alain Lechêne. Trajectoire de restauration des marais intertidaux : réponse du necton à la dépoldérisation dans l’estuaire de la Gironde. Ecologie, Environnement. Université de Bordeaux, 2017. Français. ⟨NNT : 2017BORD0883⟩. ⟨tel-01717327⟩

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