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| Raimonet, Melanie; Ragueneau, Olivier; Andrieux-loyer, Francoise; Khalil, Karima; Kerouel, Roger; Philippon, Xavier; Soetaert,, Karline; Rabouille, Christophe; Memery, Laurent. |
| Tipo: Text |
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| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00058/16909/14382.pdf |
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| Labry, Claire; Delmas, Daniel; Youenou, Agnes; Quere, Julien; Leynaert, Aude; Fraisse, Stephane; Raimonet, Melanie; Ragueneau, Olivier. |
| The occurrence of alkaline phosphatase activity (APA) that hydrolyses organic phosphorus into phosphate (PO4) is commonly related to PO4 deficiency of oceanic, coastal and fresh waters. APA is almost never investigated in PO4-rich estuaries, since very low activities are expected to occur. As a consequence, microbial mineralization of organic phosphorus into PO4 has often been ignored in estuaries. In this study, we examined the importance of potential APA and the associated microbial dynamics in two estuaries, the Aulne and the Elorn (Northwestern France), presenting two different levels of PO4 concentrations. Unexpected high potential APA was observed in both estuaries. Values ranged from 50 to 506 nmol L−1 h−1, which range is usually found in very... |
| Tipo: Text |
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| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00337/44840/44428.pdf |
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| Raimonet, Melanie; Guillou, Gael; Mornet, Francoise; Richard, Pierre. |
| Although nitrogen stable isotope ratio (delta N-15) in macroalgae is widely used as a bioindicator of anthropogenic nitrogen inputs to the coastal zone, recent studies suggest the possible role of macroalgae metabolism in delta N-15 variability. Simultaneous determinations of delta N-15 of dissolved inorganic nitrogen (DIN) along the land sea continuum, inter-species variability of delta N-15 and its sensitivity to environmental factors are necessary to confirm the efficiency of macroalgae delta N-15 in monitoring nitrogen origin in mixed-use watersheds. In this study, delta N-15 of annual and perennial macroalgae (Ulva sp., Enterommpha sp., Fucus vesiculosus and Fucus serratus) are compared to delta N-15-DIN along the Charente Estuary, after... |
| Tipo: Text |
Palavras-chave: Nitrogen isotopes; Nitrate; Ammonium; Primary producers; Indicators; Land-sea continuum. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00134/24558/23645.pdf |
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| Raimonet, Melanie; Ragueneau, Olivier; Jacques, Vincent; Corvaisier, Rudolph; Moriceau, Brivaela; Khripounoff, Alexis; Pozzato, Lara; Rabouille, Christophe. |
| Mechanisms controlling the transfer and retention of silicon (Si) along continental margins are poorly understood, but play a major role in the functioning of coastal ecosystems and the oceanic biological pump of carbon. Deep-sea fans are well recognized as carbon sink spots, but we lack knowledge about the importance of the fans in the global Si cycle. Here, we provide a first estimate of the role played by the Congo deep-sea fan, one of the biggest in the world, in the Si cycle. Sediment cores sampled in the deep-sea fan were analyzed to build a Si mass balance. An exceptionally high accumulation rate of amorphous silica aSiO(2) (2.29 +/- 0.58 mol Si m(-2) y(-1)) was found, due to a high sedimentation rate and the presence of aluminum in the sediments.... |
| Tipo: Text |
Palavras-chave: Continental margin; Land-sea export; Silica cycle; Congo canyon; Deep-sea fan. |
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00251/36242/35797.pdf |
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| Khalil, Karima; Raimonet, Melanie; Laverman, Anniet M.; Yan, Chen; Andrieux-loyer, Françoise; Viollier, Eric; Deflandre, Bruno; Ragueneau, Olivier; Rabouille, Christophe. |
| This paper deals with the spatial and seasonal recycling of organic matter in sediments of two temperate small estuaries (Elorn and Aulne, France). The spatio-temporal distribution of oxygen, nutrient and metal concentrations as well as the organic carbon and nitrogen contents in surficial sediments were determined and diffusive oxygen fluxes were calculated. In order to assess the source of organic carbon (OC) in the two estuaries, the isotopic composition of carbon (δ 13C) was also measured. The temporal variation of organic matter recycling was studied during four seasons in order to understand the driving forces of sediment mineralization and storage in these temperate estuaries. Low spatial variability of vertical profiles of oxygen, nutrient, and... |
| Tipo: Text |
Palavras-chave: Spatial and temporal variability; Estuarine sediment; Oxygen; Organic carbon and isotopic composition; Microelectrode; Organic matter recycling. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00164/27533/25691.pdf |
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| Raimonet, Melanie; Ragueneau, Olivier; Andrieux Loyer, Francoise; Philippon, Xavier; Kerouel, Roger; Le Goff, Manon; Memery, Laurent. |
| The high heterogeneity of silica cycling in coastal margins and the lack of silica data (compared to nitrogen and phosphorus) prevent the estimation of global silica retention in estuaries. In this study, the spatial and temporal variability of porewater silicic acid (Si(OH)4) profiles e that integrate benthic transport and reaction processes e was investigated at different spatial (metre, longitudinal and crosssection, intra-estuary) and temporal (tidal, seasonal) scales in two macrotidal estuaries, very close geographically but essentially differing in their shape. Studying the spatial and temporal variability of Si(OH)4 concentrations in porewaters provided evidence for the importance of transport processes, e.g. bio-irrigation, tidal pumping,... |
| Tipo: Text |
Palavras-chave: Heterogeneity; Season; Silicate; Sediment; Land-sea interface; Upscaling. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00124/23529/22370.pdf |
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| Ragueneau, Olivier; Raimonet, Melanie; Maze, Camille; Coston-guarini, Jennifer; Chauvaud, Laurent; Danto, Anatole; Grall, Jacques; Jean, Frederic; Paulet, Yves-marie; Thouzeau, Gerard. |
| In this contribution, the study of the Bay of Brest ecosystem changes over the past 50 years is used to explore the construction of interdisciplinary knowledge and raise key questions that now need to be tackled at the science-policy-communities interface. The Bay of Brest is subject to a combination of several aspects of global change, including excessive nutrient inputs from watersheds and the proliferation of invasive species. These perturbations strongly interact, affecting positively or negatively the ecosystem functioning, with important impacts on human activities. We first relate a cascade of events over these five decades, linking farming activities, nitrogen, and silicon biogeochemical cycles, hydrodynamics of the Bay, the proliferation of an... |
| Tipo: Text |
Palavras-chave: Sustainability; Land-ocean continuum; Bay of Brest; Interdisciplinarity; Science-policy-community interface. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00616/72792/72272.pdf |
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