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| Trut, Gilles; Auby, Isabelle; Rigouin, Loic; Oger-jeanneret, Helene; Ganthy, Florian; Cognat, Mathis; Noel, Claire; Marchetti, Simon; Bauer, Eric. |
| Ce document présente les résultats du suivi surfacique des herbiers infralittoraux de zostères marines du bassin d’Arcachon opéré en juin 2016. Comme en 2008 (Dalloyau et al., 2009), la méthode utilisée, dite DIVA (Détection & Inspection Verticale Acoustique), permet de générer une information de présence/absence, par superposition de signaux issus d’un sonar latéral GEOSWATH et d’un sondeur acoustique mono-faisceau de grande précision. Ces données sont couplées à des observations de terrain obtenues à l’aide de caméras vidéo sous-marines GoPro, reliées à un système de positionnement sub-métrique. Les opérations de terrain ont été réalisées en juin 2016. En outre, ce rapport traite de l'évolution temporelle de la surface occupée par les herbiers de... |
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| Ano: 2018 |
URL: http://archimer.ifremer.fr/doc/00444/55526/57114.pdf |
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| Cognat, Mathis; Ganthy, Florian; Auby, Isabelle; Barraquand, Frederic; Rigouin, Loic; Sottolichio, Aldo. |
| The relative impact of light, depth, hydrology, hydrodynamics, sediment and nutrients on growth of the seagrass Zostera noltei was investigated in Arcachon Bay, where the extent of seagrass beds has been decreasing for 20 years. A comprehensive multi-parameter survey of 9 sites was conducted monthly over one year. A three-parameter logistic growth model was fitted to biomass data to unravel the relative contributions of environmental factors on seagrass growth. The present study highlights the fact that, in addition to the dominant positive effect of light on plant growth, the hydrological and hydrodynamic parameters were important drivers for Z. noltei growth at the scale of the whole Bay. At the scale of individual sites, other factors such as macroalgal... |
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Palavras-chave: Physical parameters; Light; Hydrodynamics; Adaptation; Statistical growth model. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00451/56229/57789.pdf |
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| Ganthy, Florian; Cognat, Mathis; Lanson, Meline; Rigouin, Loic. |
| Within the semi-enclosed mesotidal lagoon of Arcachon, most of intertidal mudflats are colonized by seagrass meadows of Zostera noltei. However, a drastic spatial regression of this species has occurred over the last 20 years. In the meantime, important modifications of hydrodynamics and sediment dynamics were observed: significant changes in tidal asymmetry, increase of suspended sediment concentration, massive accumulation of mud over eastern sandy beaches, increase in dredging requirements in uspstream shallow channels. This study investigates the dynamics of newly deposited decimetric mud layer over a sheltered sandy beach, in order to assess the origin and the future of these muddy deposits. To achieve these objectives, a four-month high frequency... |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00443/55457/56969.pdf |
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| Cognat, Mathis; Auby, Isabelle; Rigouin, Loic; Sottolichio, Aldo; Ganthy, Florian. |
| The extent of Zostera spp. meadows in Arcachon Bay has drastically decreased in the last 20 years and a significant increase of suspended sediment concentration was observed in the meantime. Zostera spp. are well known ecosystem engineers able to reduce near-bed currents and promote sediment accretion; it is then suggested that such decline may lead to the observed increase of sediment re-suspension. Main consequences are an increase of net erosion trends on tidal flats, and a decrease of light penetration in the water column. In this context, this study focuses on spatio-temporal analysis of seagrass decline in relation with morphological and hydrodynamical changes in the Bay. Historical bathymetric charts and maps of Zostera beds extent were co-analysed.... |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00443/55447/56967.pdf |
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| Auby, Isabelle; Rigouin, Loic; Trut, Gilles; Oger-jeanneret, Helene; Ganthy, Florian; Cognat, Mathis; Gouriou, Laure; Bujan, Stéphane; Devaux, Ludovic; Dalloyau, Sébastien; Feigne, Claude; Pere, Caroline. |
| Tipo: Text |
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| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00392/50384/51089.pdf |
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| Auby, Isabelle; Oger-jeanneret, Helene; Rigouin, Loic; Trut, Gilles; Cognat, Mathis; Ganthy, Florian; Gouriou, Laure; Bujan, Stéphane; Gouillieux, Benoit; Dalloyau, Sébastien; Feigne, Claude; Pere, Caroline; Aubert, Fabien. |
| Ce rapport rend compte des résultats obtenus dans les herbiers de la masse d’eau « Arcachon amont » sur l’ensemble de la période d’étude et indique le classement de la masse d’eau « Arcachon amont » vis à vis de l’indicateur de qualité biologique « angiospermes » en 2017. |
| Tipo: Text |
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| Ano: 2018 |
URL: http://archimer.ifremer.fr/doc/00451/56239/57798.pdf |
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