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| Registros recuperados: 42 | |
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| Ehrhold, Axel; Auffret, Jean-paul. |
| Grain size trends in relation to net sediment transport pathways are examined, using sorne cornmonly-used grain size pararneters. The results of the model are compared with the net sediment transport pathways established on the basis of the bedfonn asymmetry. The 3 types of trends are calculated using an increasing characteristic distance and differents grids of seabed sediment samples. lt is shown that : (1) the characteristic distance defined by Gao et Collins (maximum spatial sampling interval) changes with these two factors to a maximal value; (2) in an heterogeneous sedimentary environment, the correlations between calculated vectors and observed transport pathways are better by using sand size distributions and (3) the residual pattern rises to sixty... |
| Tipo: Text |
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| Ano: 1996 |
URL: http://archimer.ifremer.fr/doc/00285/39620/38111.pdf |
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| Mazurie, Joseph; Stanisiere, Jean-yves; Bouget, Jean-francois; Langlade, Aime; Leclerc, Emilie; Quinsat, Kevin; Herve, Gilles; Augustin, Jean-marie; Ehrhold, Axel; Sinquin, Jean-marc; Meidi-deviarni, Ika; Goubert, Evelyne; Cochet, Helene; Dreano, Alain. |
| This study (“Risco”), implicating both industry, socio-economic experts and biologists, was funded by the Regional Council of Brittany, for 3 years (2010-2012), to investigate about the causes of oysters (Crassostrea gigas) mortalities in the bay of Quiberon (South Brittany, France). The protocol including both a sonar and video visualization of the bottom, and a monthly survey of 15 experimental oyster structures, allowed to assess the risk due to predation. A clear spatial distribution of the predatory effect was evidenced, with starfish (Asterias rubens and Marthasterias glacialis) predominating in the North-East sector, and boring snails (Ocenebra erinacea and Pterophora inornata) in the South-Center area.. The main mortalities from these predators... |
| Tipo: Text |
Palavras-chave: Baie de Quiberon; Huître; Crassostrea gigas; Risque; Mortalité; Prédation; Étoiles de mer; Bigorneaux perceurs; Risco; Bay of Quiberon; Oyster; Crassostrea gigas; Risk; Mortality; Predation; Starfish; Oyster drills; Risco. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00180/29130/27534.pdf |
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| Durand, M.; Mojtahid, M.; Maillet, G. M.; Proust, J. -n.; Lehay, D.; Ehrhold, Axel; Barre, A.; Howa, H.. |
| We used sedimentological and foraminiferal characteristics of four sedimentary cores, supported by paleogeographical and historical data, to reconstruct the depositional history of the inner Loire estuary (Near Saint-Nazaire, France) and the response of benthic foraminifera to the mid- to late-Holocene marine flooding of the incised valley. These were further used to evaluate the consequent changes in estuarine morphological and hydro-sedimentary patterns during this time period. Our results described significant changes in hydro-sedimentary dynamics over the past ~ 6 kyrs BP. At our location, these changes expressed the combined influence of marine (e.g., tide, storm waves) and fluvial dynamics (e.g., floods), which are linked, on a broader scale, to... |
| Tipo: Text |
Palavras-chave: Macrotidal estuary; Mid-latitude estuary; Holocene paleoenvironment; Estuarine facies; Benthic foraminifera; Sea-level change. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00347/45849/45511.pdf |
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| Hamon, Dominique; Ehrhold, Axel; Houlgatte, Eric; Kerdoncuff, Julien; Gaffet, Jean-dominique; Caisey, Xavier; Alix, Anne-sophie; Oger-jeanneret, Helene. |
| Poster présenté aux Journées REBENT Brest les 13 et 14/10/2011 (2ème atelier de restitution Rebent Bretagne. Dans le cadre du programme de surveillance DCE, et en lien avec le projet REBENT, il a été entrepris en 2008-2009 de cartographier et de caractériser les principaux bancs de maërl distribués dans 9 masses d'eaux autour de la Bretagne, et faisant l'objet pour la plupart d'un suivi annuel de leur biodiversité, assuré par l'IUEM (LEMAR). |
| Tipo: Text |
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| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00042/15275/12631.pdf |
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| Ehrhold, Axel. |
| La baie de Morlaix, fermée par l’île de Batz à l’ouest, les falaises de Primel-Trégastel à l’est, et l’archipel de la Méloine au nord, est un des joyaux de la côte bretonne appréciée pour sa diversité biologique mais beaucoup moins connue par ses particularités géologiques. Sa morphologie sous-marine est une sorte de labyrinthe, composé de nombreux îlots et hauts-fonds, à l’origine d’une mosaïque de provinces sédimentaires où se confrontent à chaque marée, courants et sédiments. Cette synthèse (au format papier et numérique) regroupe les travaux menés depuis une dizaine d’années par l’Ifremer sur les fonds de cette région. Elle répond ainsi à la préoccupation d’une large communauté curieuse de son environnement : la morphologie du littoral, la dynamique et... |
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| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00285/39603/38097.pdf |
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| Dupré, Stephanie; Loubrieu, Benoit; Pierre, C.; Scalabrin, Carla; Guerin, Charline; Ehrhold, Axel; Ogor, Andre; Gautier, Emeric; Ruffine, Livio; Biville, Romain; Saout, Johan; Breton, C; Floodpage, J.; Lescanne, M.. |
| A few thousand (2612) seeps are releasing microbial methane bubbles from the seafloor at the Aquitaine Shelf edge (Bay of Biscay) at shallow water depths (140‐220 m). This methane contributes to the formation of meter‐scale subcircular carbonate structures, which are (sub‐)outcropping over 375 km2. Based on in situ flow rate measurements and acoustic data, and assuming steady and continuous fluxes over time, the methane entering the water column is estimated to 144 Mg/yr. Microbial methane circulation has been on‐going for at least a few thousand years. This discovery highlights the importance of microbial methane generation, disconnected from deep thermogenic sources and gas hydrates, at continental shelves. The shelf edge may be viewed as a focus area... |
| Tipo: Text |
Palavras-chave: Microbial methane; Continental shelf; Fluid emissions; High‐resolution acoustics; Aquitaine Margin; Methane‐derived authigenic carbonates. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00618/72982/72057.pdf |
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| Lambert, Clement; Penaud, Aurelie; Vidal, Muriel; Klouch, Khadidja; Gregoire, Gwendoline; Ehrhold, Axel; Eynaud, Frederique; Schmidt, Sabine; Ragueneau, Olivier; Siano, Raffaele. |
| For the first time a very high resolution palynological study (mean resolution of 1 to 5 years) was carried out over the last 150 years in a French estuarine environment (Bay of Brest; NW France), allowing direct comparison between the evolution of landscapes, surface water, and human practices on Bay of Brest watersheds, through continental (especially pollen grains) and marine (phytoplanktonic microalgae: cysts of dinoflagellates or dinocysts) microfossils. Thanks to the small size of the watersheds and the close proximity of the depositional environment to the mainland, the Bay of Brest represents an ideal case study for palynological investigations. Palynological data were then compared to published palaeo-genetic analyses conducted on the same core... |
| Tipo: Text |
Palavras-chave: Pollen grains; Dinoflagellate cysts; Estuarine dynamics; River runoff; Climate variability. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00410/52110/52813.pdf |
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| Baltzer, Agnes; Reynaud, Marine; Ehrhold, Axel; Fournier, Jerome; Cordier, Celine; Clouet, Helene. |
| About a decade ago, a large field of pockmarks, covering an overall area of 36 km(2) was discovered in water depths of < 30m in the central part of the Bay of Concarneau (Southern Brittany, France). This field, composed of features from 5 m to 35 m in diameter and < 1 m in depth, is characterized by unusual high densities of pockmarks, up to 5840 per square kilometre. Geophysical data correlated with sedimentary samples acquired in 2005 and 2009 show that pockmarks and their immediate surroundings are associated with dense tubes benches cover, built by a filter-feeding amphipod: Haploops nirae, forming original benthic communities. Two complementary surveys were carried out in April 2011 (Pock and Ploops) and April 2014 (Pock and Tide), on the... |
| Tipo: Text |
Palavras-chave: Géophysique; Marée; Failles; Gaz; Geophysics; Pockmarks; Tide; Turbidity; Gas; Chimneys pipes; Concarneau. |
| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00410/52107/52938.pdf |
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| Gregoire, Gwendoline; Le Roy, Pascal; Ehrhold, Axel; Jouet, Gwenael; Garlan, Thierry. |
| This study details the sedimentary infilling of an original tidal-dominated estuary system during the final stage of the last marine transgression. The Bay of Brest is confined and connects the rivers Elorn and Aulne, to the sea of Iroise by a narrow strait encasing a well preserved paleo-channel. The compilation of high- and very-high-resolution bathymetric and seismic data, constrained by sediments datations, allows us to classify the paleo-morphology of the bay into three stepped domains: the paleo-valley floor surrounded by fluvial terraces, the central plateau, and the shallow embayments. Taking into account the main factors controlling the infilling, including sea-level rise, substratum morphology, and hydrodynamics, the stratigraphic scheme of the... |
| Tipo: Text |
Palavras-chave: Tide-dominated estuary; Incised-valley; Holocene infill; Seismic stratigraphy; Estuarine processes; Bay of Brest. |
| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00358/46968/46883.pdf |
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| Ehrhold, Axel; Chevalier, Claire; Alix, Anne-sophie; Autret, Elodie; Caisey, Xavier; Drussel, Benjamin; Gaffet, Jean-dominique; Hamon, Dominique; Houlgatte, Eric; Pluquet, Fabrice; Biscara, Laurie; Choisnet, Justine; Bajjouk, Touria. |
| In 2000 Ifremer launched and coordinated the development of a monitoring strategy for the REBENT network (REseau BENThique) in order to assess the aftermath of the “Erika” oil spill which took place in December 1999. Its aim is to provide consistent baseline knowledge on coastal benthic habitats, as well as to develop a monitoring tool that detects changes at various spatial and temporal scales. Sector-based seabed habitat mapping in shallow water (< 50 m deep), is currently being conducted throughout Brittany's coastal waters using a combination of geoacoustic marine systems together with ground-truthing using biological grab sampling and seabed observations. Due to the extended area, the overlap of soft and rocky bottoms, and contrasting hydrological... |
| Tipo: Text |
Palavras-chave: Rebent; Trégor-Goëlo; Bréhat; Cartographie d’habitats; Sonar latéral; Macrofaune benthique; Peuplements; Crépidule; Maërl; Sédiments; Morphologie; Dynamique sédimentaire; Rebent; Trégor-Goëlo; Bréhat archipelago; Marine habitat mapping; Sidescan sonar; Benthic macrofauna; Communities; Crepidula bed; Maerl; Sediment; Morphology; Bedload transpor. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00280/39161/37724.pdf |
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| Stanisiere, Jean-yves; Mazurie, Joseph; Bouget, Jean-francois; Langlade, Aime; Gabellec, Raoul; Retho, Michael; Quinsat, Kevin; Leclerc, Emilie; Cugier, Philippe; Dussauze, Morgan; Menesguen, Alain; Dumas, Franck; Gohin, Francis; Augustin, Jean-marie; Ehrhold, Axel; Sinquin, Jean-marc; Goubert, Evelyne; Dreano, Alain. |
| The project “Risco”, supported by the “Pôle Mer” and funded by the Regional Council of Brittany, deals with specific risks of mortality of oysters, Crassostrea gigas, cultivated on the bottom, in a subtidal bay of South Brittany : the bay of Quiberon (56, France). Massive mortalities of oysters were reported in summer 2006 in this bay, exclusively located in the deep muddy area with a positive gradient eastward. A validated biogeochemical model was applied in order to simulate the dissolved oxygen over 2000-2006 : it revealed several episodes of hypoxia, more or less intense according to years, but with the same spatial distribution. This approach proved 2006 to be the most hypoxic year since 2000. The hypoxia was due to a rare conjunction of 3 factors :... |
| Tipo: Text |
Palavras-chave: Baie Quiberon; Crassostrea gigas; Huître; Mortalité; Croissance; Hypoxie; Oxygène; Modèle; Upwelling; Loire; Vilaine; Quiberon; Crassostrea gigas; Oyster; Mortality; Growth; Hypoxia; Oxygen; Model; DEB; Upwelling; Loire; Vilaine. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00180/29131/27535.pdf |
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| Registros recuperados: 42 | |
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