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| Registros recuperados: 13 | |
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| Goeyens, L.; Kindermans, N.; Yusuf, M.A.; Elskens, M.. |
| Several earlier studies underpin the important role of dissolved organic matter and more particularly urea in phytoplanktonic nitrogen uptake fluxes. Generally, the determination of urea concentrations relies on the formation of an imidazolone-thiosemicarbizide complex, a complexation which requires very accurate temperature control when carried out at high temperature. It is also possible, however, to obtain reliable results with a room temperature procedure. The measured abundances for both complexation at high temperature (85 degree C, 20 min) and at ambient temperature (22 degree C, 72 h) are closely comparable. Lower values are observed for temperatures <10 degree C though. Moreover, a comparison of both techniques reveals similar precision... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Dissolved organic carbon; Sea water; Temperature; Urea; Water analysis. |
| Ano: 1998 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=7858 |
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| Baeyens, W.F.J.; Elskens, M.; Gillain, G.; Goeyens, L.. |
| Cu, Zn, Cd and Pb have been analysed in suspended matter and water samples from the Scheldt estuary, collected during five cruises between May 1982 and May 1983. In order to evaluate the overall metal behaviour in the estuary, continuous longitudinal profiles of the total, the particulate and the dissolved metal concentrations are discussed in relation to various specific physico-chemical parameters. By means of correlation and multi-regression techniques, several estuarine processes could be identified which dominate and/or control the behaviour of the individual trace metals in three distinct areas of the Scheldt estuary. The behaviour of the four selected metals was found to show some common features, but is besides this also characterised by many... |
| Tipo: Info:eu-repo/semantics/article |
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| Ano: 1998 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=7043 |
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| Cavagna, A. J.; Fripiat, F.; Elskens, M.; Dehairs, F.; Mangion, P.; Chirurgien, L.; Closset, I.; Lasbleiz, M.; Flores–leiva, L.; Cardinal, D.; Leblanc, K.; Fernandez, C.; Lefèvre, D.; Oriol, L.; Blain, S.; Quéguiner, B.. |
| Although the Southern Ocean is considered a High Nutrient Low Chlorophyll area (HNLC), massive and recurrent blooms are observed over and downstream the Kerguelen Plateau. This mosaic of blooms is triggered by a higher iron supply resulting from the interaction between the Antarctic Circumpolar Current and the local bathymetry. Net primary production, N-uptake (NO3− and NH4+), and nitrification rates were measured at 8 stations in austral spring 2011 (October–November) during the KEOPS2 cruise in the Kerguelen area. Iron fertilization stimulates primary production, with integrated net primary production and growth rates much higher in the fertilized areas (up to 315 mmol C m−2 d−1 and up to 0.31 d−1, respectively) compared to the HNLC reference site (12... |
| Tipo: Text |
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| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00294/40558/39445.pdf |
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| Dauby, P.; Baeyens, W.F.J.; Biondo, R.; Bouquegneau, J.-M.; Chou, L.; Collette, O.; Dehairs, F.A.; Elskens, M.; Frankignoulle, M.; Loijens, M.; Paucot, H.; Wollast, R.. |
| From 1989 to 1992, five cruises were conducted in an area covering the English Channel, the Celtic Sea and the Gulf of Biscay. During these campaigns, suspended matter was collected by different techniques in order to analyze the spatial and vertical distribution of several particulate trace elements in relation to the global biogeochemical cycle of carbon. It appears that horizontal distribution varies strongly from one element to another and is mainly influenced either by anthropogenic and terrigenous inputs or by scavenging processes. On the other hand, the vertical distribution seems mainly linked to the primary production. In parallel to these trace element measurements, experiments were carried out to estimate the transfer rates of these elements... |
| Tipo: Info:eu-repo/semantics/article |
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| Ano: 1993 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=2680 |
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| Elskens, M.; Goeyens, L.; Dehairs, F.A.; Rees, A.; Joint, I.; Baeyens, J.. |
| Statistical properties in non-linear regression models of <i>f</i>-ratio versus nitrate relationships were investigated using a case study conducted at the European continental margin (Project OMEX). Although the OMEX data fit within the family of empirical models introduced by Platt and Harrison (1985) Nature 318, 55–58), it is shown that the discrepancy between experimental and fitted values is larger than expected, assuming that the data are accurate. Since the ambient ammonium concentration plays a leading role in regulating new production, the present analysis was extended to include explicitly the effect of ammonium on <i>f</i>-ratio versus nitrate plots. Experimental results based on controlled ammonium additions... |
| Tipo: Info:eu-repo/semantics/article |
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| Ano: 1999 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=10269 |
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| Riou, V.; Halary, S.; Duperron, S.; Bouillon, S.; Elskens, M.; Bettencourt, R.; Santos, R. S.; Dehairs, F.; Colaco, A.. |
| High densities of mussels of the genus Bathymodiolus are present at hydrothermal vents of the Mid-Atlantic Ridge. It was previously proposed that the chemistry at vent sites would affect their sulphide- and methane-oxidizing endosymbionts' abundance. In this study, we confirmed the latter assumption using fluorescence in situ hybridization on Bathymodiolus azoricus specimens maintained in a controlled laboratory environment at atmospheric pressure with one, both or none of the chemical substrates. A high level of symbiosis plasticity was observed, methane-oxidizers occupying between 4 and 39% of total bacterial area and both symbionts developing according to the presence or absence of their substrates. Using (HCO3-)-C-13 in the presence of sulphide, or... |
| Tipo: Text |
Palavras-chave: Mid-atlantic ridge; Hydrocarbon-seep mussel; Deep-sea mussels; Hydrothermal-vent; Puteoserpentis bivalvia; Mytilidae; Methane; Endosymbionts; Bacteria; Metabolism. |
| Ano: 2008 |
URL: https://archimer.ifremer.fr/doc/00207/31865/30271.pdf |
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| Dehairs, F.; Fripiat, F.; Cavagna, A. -j.; Trull, T.w.; Fernandez, C.; Davies, D.; Roukaerts, A.; Fonseca Batista, D.; Planchon, F.; Elskens, M.. |
| This paper presents whole water column data for nitrate N, O isotopic composition for the Kerguelen Plateau area and the basin extending east of Heard Island, aiming at understanding the N-cycling in this naturally iron fertilized area that is characterized by large re-current phytoplankton blooms. The KEOPS 2 expedition (October-November 2011) took place in spring season and complements knowledge gathered during an earlier summer expedition to the same area (KEOPS 1, February-March 2005). As noted by others a remarkable condition of the system is the moderate consumption of nitrate over the season (nitrate remains >20 mu M) while silicic acid becomes depleted, suggesting significant recycling of nitrogen. Nitrate isotopic signatures in the upper water... |
| Tipo: Text |
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| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00260/37085/35584.pdf |
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| Semeneh, M.; Dehairs, F.A.; Elskens, M.; Baumann, M.E.M.; Kopczynska, E.E.; Lancelot, C.; Goeyens, L.. |
| Phytoplankton nitrogen uptake is studied in relation to the biomass and structure of phytoplankton community in the Atlantic and Indian sectors of the Southern Ocean. Two scenarios of seasonal evolution of uptake regime and phytoplankton community structure are described. The first scenario includes the Marginal Ice Zone areas of the Weddell Sea and adjacent areas where a predominantly nitrate based, diatom dominated assemblage, thriving in a stable water column at the beginning of the season was transformed into a mainly ammonium based, flagellate dominated assemblage, towards the end of the season. The change in phytoplankton community structure was caused by selective grazing by large grazers and reduced stability of the water column and the shift in... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Biogeochemical cycle Biomass Community composition Continental shelves Ice edge Nitrogen Pelagic environment Phytoplankton Size distribution Uptake PS; Southern Ocean PSE; Antarctic Ocean. |
| Ano: 1998 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=10255 |
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| Mengesha, S.; Dehairs, F.A.; Elskens, M.; Goeyens, L.. |
| The nitrogen nutrition of the phytoplankton community in the neritic and oceanic waters of the western Indian Ocean was investigated during the south-east monsoon (June-July) and intermonsoon periods (November-December). The region is very oligotrophic, characterized by very low nutrient concentrations (surface NO sub(3)<0.5 µM), low phytoplankton biomass (PON similar to 0.85 µmoll super(- 1)) and predominance of regenerated production (maximum f -ratio <0.47). Ammonium was the major nitrogen substrate during the two seasons, supplying 53-99% of the phytoplankton's nitrogen requirement. Nevertheless, both the uptake of nitrate and its relative contribution to total nitrogen removal (f -ratio) were significantly higher during the intermonsoon period... |
| Tipo: Info:eu-repo/semantics/article |
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| Ano: 1999 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=1951 |
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| Elskens, M.; Chou, L.; Dauby, P.; Frankignoulle, M.; Goeyens, L.; Loijens, M.; Wollast, R.. |
| Since the role of continental shelves and coastal areas in the global biochemical carbon are nowadays a leading concern in oceanographic research programmes, this study aims to define the specific effect of nutrients on the onset and development of the phytoplankton bloom at the ocean margins. Comparison experiments of the carbon, nitrogen and phosphorus assimilation rates were carried out from 1989 to 1991 in the English Channel and the Gulf of Biscay. New production were obtained from the traditional approach using <i>f</i>-ratio values, i.e. the ratios of directly measured nitrate to carbon uptakes and/or the ratios of nitrate to nitrate plus ammonium uptakes. Values of <i>f</i> agree well on the shelf, slope and deep basin... |
| Tipo: Info:eu-repo/semantics/article |
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| Ano: 1993 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=2690 |
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| Cavagna, A. J.; Fripiat, F.; Elskens, M.; Mangion, P.; Chirurgien, L.; Closset, I.; Lasbleiz, M.; Florez-leiva, L.; Cardinal, D.; Leblanc, K.; Fernandez, C.; Lefevre, D.; Oriol, L.; Blain, S.; Queguiner, B.; Dehairs, F.. |
| Although the Southern Ocean is considered a high-nutrient, low-chlorophyll (HNLC) area, massive and recurrent blooms are observed over and downstream of the Kerguelen Plateau. This mosaic of blooms is triggered by a higher iron supply resulting from the interaction between the Antarctic Circumpolar Current and the local bathymetry. Net primary production, N uptake (NO3− and NH4+), and nitrification rates were measured at eight stations in austral spring 2011 (October–November) during the KEOPS 2 cruise in the Kerguelen Plateau area. Natural iron fertilization stimulated primary production, with mixed layer integrated net primary production and growth rates much higher in the fertilized areas (up to 315 mmol C m−2 d−1 and up to 0.31 d−1 respectively)... |
| Tipo: Text |
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| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00294/40561/39448.pdf |
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| Closset, I.; Lasbleiz, M.; Leblanc, K.; Queguiner, B.; Cavagna, A. -j.; Elskens, M.; Navez, J.; Cardinal, D.. |
| A massive diatom bloom is observed each year in the surface waters of the naturally Fe-fertilized Kerguelen Plateau (Southern Ocean). We measured biogenic silica production and dissolution fluxes (rho Si and rho Diss, respectively) in the mixed layer in the vicinity of the Kerguelen Plateau during austral spring 2011 (KEOPS-2 cruise). We compare results from a high-nutrient low-chlorophyll reference station and stations with different degrees of iron enrichment and bloom conditions. Above the plateau biogenic rho Si are among the highest reported so far in the Southern Ocean (up to 47.9 mmol m(-2) d(-1)). Although significant (10.2 mmol m(-2) d(-1) on average), rho Diss were generally much lower than production rates. Uptake ratios (rho Si : rho C and rho... |
| Tipo: Text |
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| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00291/40220/39341.pdf |
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| Fripiat, F.; Elskens, M.; Trull, T. W.; Blain, S.; Cavagna, A. -j.; Fernandez, C.; Fonseca-batista, D.; Planchon, F.; Raimbault, P.; Roukaerts, A.; Dehairs, F.. |
| Nitrification, the microbially mediated oxidation of ammonium into nitrate, is generally expected to be low in the Southern Ocean mixed layer. This paradigm assumes that nitrate is mainly provided through vertical mixing and assimilated during the vegetative season, supporting the concept that nitrate uptake is equivalent to the new primary production (i.e., primary production which is potentially available for export). Here we show that nitrification is significant (~40–80% of the seasonal nitrate uptake) in the naturally iron-fertilized bloom over the southeast Kerguelen Plateau. Hence, a large fraction of the nitrate-based primary production is regenerated, instead of being exported. It appears that nitrate assimilation (light dependent) and... |
| Tipo: Text |
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| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00296/40704/39700.pdf |
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| Registros recuperados: 13 | |
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