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| Barras, C.; Duplessy, J. -c.; Geslin, E.; Michel, Elisabeth; Jorissen, F. J.. |
| The geochemical composition of deep-sea benthic foraminiferal calcite is widely used to reconstruct sea floor paleoenvironments. The calibration of the applied proxy methods has until now been based on field observations in complex natural ecosystems where multiple factors are interfering. However, laboratory experiments with stable physico-chemical conditions appear to be the ideal way to evaluate the influence of a single parameter. In this paper, we present the oxygen isotopic composition of deep-sea benthic foraminiferal shells entirely calcified under controlled experimental conditions over a large temperature range (4 to 19 degrees C). The new laboratory protocols developed for this study allowed us to produce large quantities of shells in stable... |
| Tipo: Text |
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| Ano: 2010 |
URL: https://archimer.ifremer.fr/doc/00241/35177/33738.pdf |
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| Thibault De Chanvalon, A.; Mouret, A.; Knoery, Joel; Geslin, E.; Peron, O.; Metzger, E.. |
| The sampling of surface sediment from two sites of a mudflat of the Loire Estuary during four contrasting seasons has led to new information about geochemical cycling under transient diagenesis fuelled by flood deposition. Based on stocks of reactive iron-oxides and manganese-oxides (ascorbate-extracted) and pore water concentrations, the progressive evolution of flood deposits is described. Three major steps are observed: at first, there is no manganese, iron and phosphorus release into pore water within the flood-deposited layer. Then, during a period of approximately 1 month, Mn oxides are consumed while the dissolved Mn concentration increases. Simultaneously, the Fe oxide-rich layer from flood deposition prevents (or at least limits) phosphorus... |
| Tipo: Text |
Palavras-chave: Flood deposition; Ascorbat extraction; Transient diagenesis; Savitzky Golay filter; RiOMars. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00354/46525/46291.pdf |
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| Thibault De Chanvalon, A.; Metzger, E.; Mouret, A.; Knoery, Joel; Geslin, E.; Meysman, F. J. R.. |
| Coastal and shelf sediments are considered as an important source of dissolved iron to the ocean. Here, we present a new numerical approach to estimate geochemical fluxes and production rates in an estuarine sediment at sub-millimetre resolution. This approach is based on application of Savitsky–Golay filter (SGF) procedure to two-dimensional concentration distributions of dissolved iron. We verified the procedure by applying it to artificial data of known production rates, and analysed the resulting uncertainty on production rates and fluxes across the water–sediment interface. This SGF procedure was applied to data from an intertidal mudflat that is densely inhabited by macrofauna (e.g. 630 ind m− 2 of Hediste diversicolor, I. Métais, pers.com.). Our... |
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| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00332/44365/43970.pdf |
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| De Chanvalon, A. Thibault; Metzger, E.; Mouret, A.; Cesbron, F.; Knoery, Joel; Rozuel, Emmanuelle; Launeau, P.; Nardelli, M. P.; Jorissen, F. J.; Geslin, E.. |
| We present a new rapid and accurate protocol to simultaneously sample benthic living foraminifera in two dimensions in a centimeter scale vertical grid and dissolved iron in high resolution (200 μm). Such an approach appears crucial to study foraminiferal ecology in heterogeneous environments. The foraminiferal faunas of the main intertidal mudflat of the Loire estuary are dominated by Ammonia tepida, which accounts for 92 % of the living assemblage (CTG-labeled). Its vertical distribution shows a first density maximum at the surface, a sharp decrease in the next two centimeter followed by a well defined second maximum between 3 and 8 cm depth. The heterogeneity of A. tepida in this 3–8 cm depth layer was calculated by the Moran's Index and reveals lateral... |
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| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00277/38786/37335.pdf |
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