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Organic complexation of iron in the Southern Ocean
Boye, Marie van den Berg, Constant M.G. de Jong, Jeroen T.M. Leach, Harry Croot, Peter et. al.The chemical speciation of iron was determined in the Southern Ocean along a transect from 48 to 70°S at 20°E. Dissolved iron concentrations were low at 0.1–0.6nM, with average concentrations of 0.25±0.13nM. Organic iron complexing ligands were found to occur in excess of the dissolved iron concentration at 0.72±0.23nM (equivalent to an excess of 0.5nM), with a complex stability of logKFeL′=22.1±0.5 (on the basis of Fe3+ and L′). Ligand concentrations were higher in the upper water column (top 200m) suggesting in situ production by microorganisms, and less at the surface consistent with photochemical breakdown. Our data are consistent with the presence of stable organic iron-complexing ligands in deep global ocean waters at a background level of 0.7nM. It has been suggested that this might help stabilise iron at levels of 0.7nM in deep ocean waters. However, much lower iron concentrations in the waters of the Southern Ocean suggest that these ligands do not prevent the removal of iron (by scavenging or biological uptake) to well below the concentration of these ligands. Scavenging reactions are probably inhibited by such ligand competition, so it is likely that biological uptake is the chief cause for the further removal of iron to these low levels in waters that suffer from very low iron inputs.
Iron availability and the release of iron-complexing ligands by Emiliania huxleyi
Boye, Marie van den Berg, Constant M.G.
Horizontal gradient of the chemical speciation of iron in surface waters of the northeast Atlantic Ocean
Boye, Marie Aldrich, Annette P. van den Berg, Constant M.G. de Jong, Jeroen T.M. Veldhuis, Marcel et. al.A transect across the eastern North Atlantic from 42°N, 23°W towards the European continental shelf and English Channel shows a gradient of increasing concentrations of dissolved iron (0.7–1.9 nM), iron-binding ligands and iron(II) across the continental rise. Other data, notably aluminium and manganese, indicate that the increases are part of a front in the metal concentrations, which is due to admixture of bottom waters. Metal fronts in shelf waters are well known, but it was not known that this may include iron(II) and organic iron-complexing ligands. The iron gradient covered a narrow salinity band between 35 and 36, and was linearly related to salinity indicating conservative behaviour, possibly caused by organic complexation keeping the iron in solution. The open ocean iron(II) levels were low but a major proportion of the increased iron levels in the shelf and coastal waters was found to occur as iron(II), and the increase in the overall iron concentration was matched by increased ligand concentrations causing the iron to remain organically complexed. A sedimentary origin for the iron(II) in the surface waters would require iron(II) to be more stable than expected, perhaps through complexation–stabilization.
Oceanic mercury concentrations on both sides of the Strait of Gibraltar decreased between 1989 and 2012
Cossa, Daniel Knoery, Joel Boye, Marie Marusczak, Nicolas Thomas, Bastien Courau, Philippe Sprovieri, FrancescaMercury (Hg) is a toxic metal that threatens the health of aquatic ecosystems and fish consumers. Its natural cycle has been deeply perturbed by Anthropogenic Hg emissions have deeply perturbed its natural cycle, especially since the start of the Industrial Revolution circa 1850 CE. Anthropogenic Hg emissions from North America and Europe have decreased by a factor of two in the last decades following the implementation of strict regulations. The response of North Atlantic Ocean and Mediterranean waters to this decrease remains poorly documented by field observations. A comparison of results obtained between 1989 and 2012 shows a significant decrease of Hg concentrations in waters on both sides of the Strait of Gibraltar. West of Gibraltar, the Hg decrease ranges from similar to 35 % in the upper North East Atlantic Deep Water to similar to 50 % in the North East Atlantic Central Water. East of Gibraltar, the observed decrease is similar to 30 % in the Western Mediterranean Deep Water. No decrease is observed in the deep Atlantic Ocean layer that formed before the industrial era. These results strongly substantiate the effectiveness of global anti-pollution policies on Hg contamination in oceanic waters. A consequent decline of Hg bioaccumulation in Northeastern Atlantic and Western Mediterranean pelagic ecosystems still requires verification. (C) 2019 Elsevier Ltd. All rights reserved.
Determination of the copper isotope composition of seawater revisited:A case study from the Mediterranean Sea
Baconnais, Isabelle Rouxel, Olivier Dulaquais, Gabriel Boye, MarieA new technique for the determination of dissolved copper isotope composition (delta Cu-65) of seawater was applied to examine copper sources and internal cycling in the Mediterranean Sea along the GEOTRACES GA04N transect. A succession of chelating resin with nitrilotriacetic acid functional groups and strong base anion exchange resin, together with optimization of the multi-collector inductively coupled plasma mass spectrometry set-up allowed to isolate copper from seawater matrix and to measure the Cu-65/Cu-63 ratios in seawater with an external precision of 0.06% (2 s.d.). This method was first applied for inter-comparison measurements to surface and deep waters sampled at the Bermuda Atlantic Time-Series station (BATS) in the North Atlantic Ocean during the GEOTRACES Intercalibration Cruise 1. Disparities in delta Cu-65 reported here and in the literature over these samples showed a need to investigate whether a new inter-comparison sample should be decided upon, or whether the use of UV-oxidation can also affect the measurement of delta Cu-65. We also measured total dissolved Cu concentration ([dCu](T)) and delta Cu-65 for 12 stations in the Mediterranean Sea. The delta Cu-65 distribution showed significant variations in the euphotic zone, at the Chl a maximum and at bottom depths. Copper isotope ratios ranged from +0.21% to +0.76% (+/- 0.06%, 2 s.d.), yielding an average of + 0.51% (+/- 0.20%, 2 s.d.; n =3D 96) for the Mediterranean Sea. A strong zonation between natural aerosol deposition to the South and anthropogenic aerosol deposition to the North was seen in the sample set (Dulaquais et al. 2017; Gerringa et al. 2017; Rolison et al. 2015). Natural dust deposits seemed to draw delta Cu-65 toward lower values and deeper in the euphotic zone whereas the impact of anthropogenic aerosols seemed restricted to an increase in [dCu](T). At the Chl a maximum, delta Cu-65 showed significant increase which we attributed to scavenging on and/or uptake by phytoplankton. The isotope signature of Cu sources to the Mediterranean Sea was also investigated and we inferred a significant source of isotopically heavy Cu in the Gibraltar area, potentially originating from a release of Cu sulfide leached in the mining area of Southern Spain (i.e. Iberian Pyrite Belt) in rivers and transported to the Mediterranean Sea in surface by seasonal water mass circulation. Conversely, marine sediments appear to be a source of isotopically-light Cu to deep waters. This study provides new hints on the use of copper isotopes to study sources and sinks of Cu in seawater. This article is part of a special issue entitled: "Cycles of trace elements and isotopes in the ocean - GEOTRACES and beyond" - edited by Tim M. Conway, Tristan Horner, Yves Plancherel, and Aridane G. Gonzalez.
Anticyclonic and cyclonic eddies of subtropical origin in the subantarctic zone south of Africa
Arhan, Michel Speich, Sabrina Messager, Christophe Dencausse, Guillaume Fine, Rana Boye, MarieTwo eddies, one anticyclonic and the other cyclonic, intersected in the Subantarctic Zone south of South Africa during a hydrographic transect, are described using a large set of measurements including full depth hydrography, Acoustic Doppler Current Profiler velocities, biogeochemical tracers, air-sea fluxes and altimetric sea surface height. Both eddies have a subtropical origin. The anticyclone is an Agulhas ring with convected core water of similar to 12 degrees C, and swirl velocities of 1 m s(-1). It was 9.5 months old when sampled and had crossed the Agulhas Ridge. Though sampled in summer, it was releasing similar to 200 W m(-2) (sensible plus latent heat flux) to the atmosphere. It was observed adjacent to the Subantarctic Front, illustrating the usual encounters of such structures with this front. The cyclone, marked by pronounced low oxygen and CFC anomalies revealing an origin at the continental slope, was 4.5 months old. It had swirl speeds of 0.3 m s(-1), and was coupled with the anticyclone when observed. From their kinematics and water mass properties both structures were found to transport subtropical water down to similar to 900 m, the water trapped below this depth being either from the northern Subantarctic Zone, or local water. The two structures illustrate the capacity of eddies in the region to transfer subtropical and alongslope water properties into the Subantarctic Zone.
The biogeochemical cycle of dissolved cobalt in the Atlantic and the Southern Ocean south off the coast of South Africa RID D-1233-2011 RID B-8032-2009
Bown, Johann Boye, Marie Baker, Alexander Duvieilbourg, Eric Lacan, Francois Le Moigne, Frederic Planchon, Frederic Speich, Sabrina Nelson, David M.The spatial distribution, biogeochemical cycle and external sources of dissolved cobalt (DCo) were investigated in the southeastern Atlantic and the Southern Ocean between 33 degrees 58'S and 57 degrees 33'S along the Greenwich Meridian during the austral summer 2008 in the framework of the International Polar Year. DCo concentrations were measured by flow-injection analysis and chemiluminescence detection in filtered (0.2 mu m), acidified and UV-digested samples at 12 deep stations in order to resolve the several biogeochemical provinces of the Antarctic Circumpolar Current and to assess the vertical and frontal structures in the Atlantic sector of the Southern Ocean. We measured DCo ranging from 5.73 +/- 1.15 pM to 72.9 +/- 4.51 pM. The distribution of DCo was nutrient-like in surface waters of the subtropical domain with low concentrations in the euphotic layer due to biological uptake. The biological utilization of dissolved cobalt was proportional to that of phosphate in the subtropical domain with a DCo:HPO(4)(2-) depletion ratio of similar to 44 mu M M(-1). In deeper waters the distribution indicated remineralization of DCo and inputs from the margins of South Africa with lateral advection of enriched intermediate and deep waters to the southeastern Atlantic Ocean. In contrast the vertical distribution of DCo changed southward, from a nutrient-like distribution in the subtropical domain to scavenged-type behavior in the domain of the Antarctic Circumpolar Current and conservative distribution in the Weddell Gyre. There the cycle of DCo featured low biological removal by Antarctic diatoms with input to surface waters by snow, removal in oxygenated surface waters, and dissolution and stabilization in the low-oxygenated Upper Circumpolar Deep Waters. DCo distributions and physical hydro-dynamics features also suggest inputs from the Drake Passage and the southwestern Atlantic to the 0 meridian along the eastward flow of the Antarctic Circumpolar Current. Bottom enrichment of DCo in the Antarctic Bottom Waters was also evident, together with increasing water-mass pathway and aging, possibly due to sediment resuspension and/or mixing with North Atlantic Deep waters in the Cape Basin. Overall atmospheric input of soluble Co by dry aerosols to the surface waters was low but higher in the ACC domain than in the northern part of the section. At the highest latitudes, it is possible that snowfall could be a source of DCo to surface waters. Tentative budgets for DCo in the mixed layer of the subtropical and the ACC domain; have been constructed for each biogeochemical region encountered during the cruise. The estimated DCo uptake flux was found to be the dominant cobalt flux along the section. This flux decreases southward, which is consistent with the observations that DCo shows a southward transition from nutrient-like towards conservative distribution in the mixed layer. (C) 2011 Elsevier B.V. All rights reserved.
The GEOTRACES Intermediate Data Product 2017
Schlitzer, Reiner Anderson, Robert F. Dodas, Elena Masferrer Lohan, Maeve Geibere, Walter Tagliabue, Alessandro Bowie, Andrew Jeandel, Catherine Maldonado, Maria T. Landing, William M. Cockwell, Donna Abadie, Cyril Abouchami, Wafa Achterberg, Eric P. Agather, Alison Aguliar-Islas, Ana van Aken, Hendrik M. Andersen, Morten Archer, Corey Auro, Maureen de Baar, Hein J. Baars, Oliver Baker, Alex R. Bakker, Karel Basak, Chandranath Baskaran, Mark Bates, Nicholas R. Bauch, Dorothea van Beek, Pieter Behrens, Melanie K. Black, Erin Bluhm, Katrin Bopp, Laurent Bouman, Heather Bowman, Katlin Bown, Johann Boyd, Philip Boye, Marie Boyle, Edward A. Branellec, Pierre Bridgestock, Luke Brissebrat, Guillaume Browning, Thomas Bruland, Kenneth W. Brumsack, Hans-Juergen Brzezinski, Mark Buck, Clifton S. Buck, Kristen N. Buesseler, Ken Bull, Abby Butler, Edward Cai, Pinghe Camara Mor, Patricia Cardinal, Damien Carlson, Craig Carrasco, Gonzalo Casacuberta, Nuria Casciotti, Karen L. Castrillejo, Maxi Chamizo, Elena Chance, Rosie Charette, Matthew A. Chaves, Joaquin E. Cheng, Hai Chever, Fanny Christl, Marcus Church, Thomas M. Closset, Ivia Colman, Albert Conway, Tim M. Cossa, Daniel Croot, Peter Cullen, Jay T. Cutter, Gregory A. Daniels, Chris Dehairs, Frank Deng, Feifei Dieu, Huong Thi Duggan, Brian Dulaquais, Gabriel Dumousseaud, Cynthia Echegoyen-Sanz, Yolanda Edwards, R. Lawrence Ellwood, Michael Fahrbach, Eberhard Fitzsimmons, Jessica N. Flegal, A. Russell Fleisher, Martin Q. van de Flierdt, Tina Frank, Martin Friedrich, Jana Fripiat, Francois Froellje, Henning Galer, Stephen J. G. Gamo, Toshitaka Ganeshram, Raja S. Garcia-Orellana, Jordi Garcia-Solsona, Ester Gault-Ringold, Melanie George, Ejin Gerringa, Loes J. A. Gilbert, Melissa Godoy, Jose M. Goldstein, Steven L. Gonzalez, Santiago R. Grissom, Karen Hammerschmidt, Chad Hartman, Alison Hassler, Christel S. Hathorne, Ed C. Hatta, Mariko Hawco, Nicholas Hayes, Christopher T. Heimburger, Lars-Eric Helgoe, Josh Heller, Maija Henderson, Gideon M. Henderson, Paul B. van Heuven, Steven Ho, Peng Horner, Tristan J. Hsieh, Yu-Te Huang, Kuo-Fang Humphreys, Matthew P. Isshiki, Kenji Jacquot, Jeremy E. Janssen, David J. Jenkins, William J. John, Seth Jones, Elizabeth M. Jones, Janice L. Kadko, David C. Kayser, Rick Kenna, Timothy C. Khondoker, Roulin Kim, Taejin Kipp, Lauren Klar, Jessica K. Klunder, Maarten Kretschmer, Sven Kumamoto, Yuichiro Laan, Patrick Labatut, Marie Lacan, Francois Lam, Phoebe J. Lambelet, Myriam Lamborg, Carl H. Le Moigne, Frederic A. C. Le Roy, Emilie Lechtenfeld, Oliver J. Lee, Jong-Mi Lherminier, Pascale Little, Susan Lopez-Lora, Mercedes Lu, Yanbin Masque, Pere Mawji, Edward Mcclain, Charles R. Measures, Christopher Mehic, Sanjin Menzel Barraqueta, Jan-Lukas van der Merwe, Pier Middag, Rob Mieruch, Sebastian Milne, Angela Minami, Tomoharu Moffett, James W. Moncoiffe, Gwenaelle Moore, Willard S. Morris, Paul J. Morton, Peter L. Nakaguchi, Yuzuru Nakayama, Noriko Niedermiller, John Nishioka, Jun Nishiuchi, Akira Noble, Abigail Obata, Hajime Ober, Sven Ohnemus, Daniel C. van Ooijen, Jan O'Sullivan, Jeanette Owens, Stephanie Pahnke, Katharina Paul, Maxence Pavia, Frank Pena, Leopoldo D. Petersh, Brian Planchon, Frederic Planquette, Helene Pradoux, Catherine Puigcorbe, Viena Quay, Paul Queroue, Fabien Radic, Amandine Rauschenberg, S. Rehkamper, Mark Rember, Robert Remenyi, Tomas Resing, Joseph A. Rickli, Joerg Rigaud, Sylvain Rijkenberg, Micha J. A. Rintoul, Stephen Robinson, Laura F. Roca-Marti, Montserrat Rodellas, Valenti Roeske, Tobias Rolison, John M. Rosenberg, Mark Roshan, Saeed van der Loaff, Michiel M. Rutgers Ryabenko, Evgenia Saito, Mak A. Salt, Lesley A. Sanial, Virginie Sarthou, Geraldine Schallenberg, Christina Schauer, Ursula Scher, Howie Schlosser, Christian Schnetger, Bernhard Scott, Peter Sedwick, Peter N. Semiletov, Igor Shelley, Rachel Sherrell, Robert M. Shiller, Alan M. Sigman, Daniel M. Singh, Sunil Kumar Slagter, Hans A. Slater, Emma Smethie, William M. Snaith, Helen Sohrin, Yoshiki Sohst, Bettina Sonke, Jeroen E. Speich, Sabrina Steinfeldt, Reiner Stewart, Gillian Stichel, Torben Stirling, Claudine H. Stutsman, Johnny Swarr, Gretchen J. Swift, James H. Thomas, Alexander Thorne, Kay Till, Claire P. Till, Ralph Townsend, Ashley T. Townsend, Emily Tuerena, Robyn Twining, Benjamin S. Vance, Derek Velazquez, Sue Venchiarutti, Celia Villa-Alfageme, Maria Vivancos, Sebastian M. Voelker, Antje H. L. Wake, Bronwyn Warner, Mark J. Watson, Ros van Weerlee, Evaline Weigand, M. Alexandra Weinstein, Yishai Weiss, Dominik Wisotzki, Andreas Woodward, E. Malcolm S. Wu, Jingfeng Wu, Yingzhe Wuttig, Kathrin Wyatt, Neil Xiang, Yang Xie, Ruifang C. Xue, Zichen Yoshikawa, Hisayuki Zhang, Jing Zhang, Pu Zhao, Ye Zheng, Linjie Zheng, Xin-Yuan Zieringer, Moritz Zimmer, Louise A. Ziveri, Patrizia Zunino, Patricia Zurbrick, CherylThe GEOTRACES Intermediate Data Product 2017 (IDP2017) is the second publicly available data product of the international GEOTRACES programme, and contains data measured and quality controlled before the end of 2016. The IDP2017 includes data from the Atlantic, Pacific, Arctic, Southern and Indian oceans, with about twice the data volume of the previous IDP2014. For the first time, the IDP2017 contains data for a large suite of biogeochemical parameters as well as aerosol and rain data characterising atmospheric trace element and isotope (TEI) sources. The TEI data in the IDP2017 are quality controlled by careful assessment of intercalibration results and multi-laboratory data comparisons at crossover stations. The IDP2017 consists of two parts: (1) a compilation of digital data for more than 450 TEIs as well as standard hydrographic parameters, and (2) the eGEOTRACES Electronic Atlas providing an on-line atlas that includes more than 590 section plots and 130 animated 3D scenes. The digital data are provided in several formats, including ASCII, Excel spreadsheet, netCDF, and Ocean Data View collection. Users can download the full data packages or make their own custom selections with a new on-line data extraction service. In addition to the actual data values, the IDP2017 also contains data quality flags and 1-s data error values where available. Quality flags and error values are useful for data filtering and for statistical analysis. Metadata about data originators, analytical methods and original publications related to the data are linked in an easily accessible way. The eGEOTRACES Electronic Atlas is the visual representation of the IDP2017 as section plots and rotating 3D scenes. The basin-wide 3D scenes combine data from many cruises and provide quick overviews of large-scale tracer distributions. These 3D scenes provide geographical and bathymetric context that is crucial for the interpretation and assessment of tracer plumes near ocean margins or along ridges. The IDP2017 is the result of a truly international effort involving 326 researchers from 25 countries. This publication provides the critical reference for unpublished data, as well as for studies that make use of a large cross-section of data from the IDP2017. This article is part of a special issue entitled: Conway GEOTRACES-edited by Tim M. Conway, Tristan Horner, Yves Plancherel, and Aridane G. Gonzalez.
Simulation of an artificial upwelling using immersed in situ phytoplankton microcosms
Giraud, Melanie Boye, Marie Garcon, Veronique Donval, Anne de la Broise, DenisThe inflow of deep seawater in the surface layer by an Ocean Thermal Energy Conversion (OTEC) plant will generate artificial upwelling. In order to study the potential impact on biogeochemical processes that could result, in situ microcosms were designed to simulate seawater plant discharge and these were deployed off the Caribbean coast of Martinique. Seawater was collected in ultra-clean conditions at maximum chlorophyll a concentrations (45 m depth). The water was then mixed with either 2% or 10% deep seawater (1100 m depth) and put in 2.3 L polycarbonate bottles. These microcosms were immersed for 6 days at 45 m depth on a 220 m mooring. Samples from the surrounding environment and from the microcosms were analyzed by pigment quantification, counting of picophytoplankton groups and macronutrient analyses. Similar trends in the evolutions of the phytoplankton populations were observed over time between the control microcosms (without addition of deep seawater) and the surrounding environment, suggesting that these microcosms can be used as a realistic representation of the natural surrounding waters over a 6-day incubation period. Microcosm enrichment with 10% deep seawater induced a shift in the phytoplankton assemblage towards the development of diatoms, haptophytes, and Prochlorococcus, whereas 2% enrichment only led to an increase in the Prochlorococcus population. (C) 2015 Elsevier B.V. All rights reserved.
Potential effects of deep seawater discharge by an Ocean Thermal Energy Conversion plant on the marine microorganisms in oligotrophic waters
Giraud, Melanie Garcon, Veronique de la Broise, Denis L'Helguen, Stephane Sudre, Joel Boye, MarieInstallation of an Ocean Thermal Energy Conversion pilot plant (OTEC) off the Caribbean coast of Martinique is expected to use approximately 100,000 m(3) h(-1) of deep seawater for its functioning. This study examined the potential effects of the cold nutrient-rich deep seawater discharge on the phytoplankton community living in the surface warm oligotrophic waters before the installation of the pilot plant. Numerical simulations of deep seawater upwelled by the OTEC, showed that a 3.0 degrees C temperature change, considered as a critical threshold for temperature impact, was never reached during an annual cycle on the top 150 m of the water column on two considered sections centered on the OTEC. The thermal effect should be limited, <1 km(2) on the area exhibited a temperature difference of 0.3 degrees C (absolute value), producing a negligible thermic impact on the phytoplankton assemblage. The impact on phytoplankton of the resulting mixed deep and surface seawater was evaluated by in situ microcosm experiments. Two scenarios of water mix ratio (2% and 10% of deep water) were tested at two incubation depths (deep chlorophyll-a maximum: DCM and bottom of the euphotic layer: BEL). The larger impact was obtained at DCM for the highest deep seawater addition (10%), with a development of diatoms and haptophytes, whereas 2% addition induced only a limited change of the phytoplankton community (relatively higher Prochlorococcus sp. abundance, but without significant shift of the assemblage). This study suggested that the OTEC plant would significantly modify the phytoplankton assemblage with a shift from pico-phytoplankton toward micro-phytoplankton only in the case of a discharge affecting the DCM and would be restricted to a local scale. Since the lower impact on the phytoplankton assemblage was obtained at BEL, this depth can be recommended for the discharge of the deep seawater to exploit the OTEC plant. (C) 2019 Elsevier B.V. All rights reserved.