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3. Community‐Level Responses to Iron Availability in Open Ocean Plankton Ecosystems

Author

Caputi, Luigi, Carradec, Quentin, Eveillard, Damien, Kirilovsky, Amos, Pelletier, Eric, Pierella Karlusich, Juan J, Rocha Jimenez Vieira, Fabio, Villar, Emilie, Chaffron, Samuel, Malviya, Shruti, Scalco, Eleonora, Acinas, Silvia G, Alberti, Adriana, Aury, Jean‐Marc, Benoiston, Anne‐Sophie, Bertrand, Alexis, Biard, Tristan, Bittner, Lucie, Boccara, Martine, Brum, Jennifer R, Brunet, Christophe, Busseni, Greta, Carratalà, Anna, Claustre, Hervé, Coelho, Luis Pedro, Colin, Sébastien, D'Aniello, Salvatore, Da Silva, Corinne, Del Core, Marianna, Doré, Hugo, Gasparini, Stéphane, Kokoszka, Florian, Jamet, Jean‐Louis, Lejeusne, Christophe, Lepoivre, Cyrille, Lescot, Magali, Lima‐Mendez, Gipsi, Lombard, Fabien, Lukeš, Julius, Maillet, Nicolas, Madoui, Mohammed‐Amin, Martinez, Elodie, Mazzocchi, Maria Grazia, Néou, Mario B, Paz‐Yepes, Javier, Poulain, Julie, Ramondenc, Simon, Romagnan, Jean‐Baptiste, Roux, Simon, Salvagio Manta, Daniela, Sanges, Remo, Speich, Sabrina, Sprovieri, Mario, Sunagawa, Shinichi, Taillandier, Vincent, Tanaka, Atsuko, Tirichine, Leila, Trottier, Camille, Uitz, Julia, Veluchamy, Alaguraj, Veselá, Jana, Vincent, Flora, Yau, Sheree, Kandels‐Lewis, Stefanie, Searson, Sarah, Dimier, Céline, Picheral, Marc, Bork, Peer, Boss, Emmanuel, Vargas, Colomban, Follows, Michael J, Grimsley, Nigel, Guidi, Lionel, Hingamp, Pascal, Karsenti, Eric, Sordino, Paolo, Stemmann, Lars, Sullivan, Matthew B, Tagliabue, Alessandro, Zingone, Adriana, Garczarek, Laurence, d'Ortenzio, Fabrizio, Testor, Pierre, Not, Fabrice, d'Alcalà, Maurizio Ribera, Wincker, Patrick, Bowler, Chris, Iudicone, Daniele, Gorsky, Gabriel, and Jaillon, Olivier

Subjects
Genetics, Life Below Water, Atmospheric Sciences, Geochemistry, Oceanography, Meteorology & Atmospheric Sciences
Abstract

Predicting responses of plankton to variations in essential nutrients is hampered by limited in situ measurements, a poor understanding of community composition, and the lack of reference gene catalogs for key taxa. Iron is a key driver of plankton dynamics and, therefore, of global biogeochemical cycles and climate. To assess the impact of iron availability on plankton communities, we explored the comprehensive bio-oceanographic and bio-omics data sets from Tara Oceans in the context of the iron products from two state-of-the-art global scale biogeochemical models. We obtained novel information about adaptation and acclimation toward iron in a range of phytoplankton, including picocyanobacteria and diatoms, and identified whole subcommunities covarying with iron. Many of the observed global patterns were recapitulated in the Marquesas archipelago, where frequent plankton blooms are believed to be caused by natural iron fertilization, although they are not captured in large-scale biogeochemical models. This work provides a proof of concept that integrative analyses, spanning from genes to ecosystems and viruses to zooplankton, can disentangle the complexity of plankton communities and can lead to more accurate formulations of resource bioavailability in biogeochemical models, thus improving our understanding of plankton resilience in a changing environment.

Published
2019

5. Impact of submarine volcanic versus hydrothermal activity onto the strontium and lithium isotopic signatures of the water column (TONGA).

Author

Chavagnac, Valérie, Destrigneville, Christine, Boulart, Cédric, Taillandier, Vincent, Vigier, Nathalie, Guieu, Cecile, and Bonnet, Sophie

Subjects
LITHIUM isotopes, HYDROTHERMAL vents, STRONTIUM isotopes, ISOTOPIC signatures, WATER sampling
Abstract

During the TONGA cruise (2019), seawater samples were collected to assess the effect of volcanic eruption versus submarine hydrothermal system on the water column. For this purpose, two locations were investigated, the first one located directly under the influence of the New Late'iki island (eruption in October 2019), and the second one showing ongoing submarine hydrothermal activity. At both locations, the total strontium (TSr) and lithium (TLi) concentrations vary between 94.4 and 152.3 µmol/L and 13.2 and 203.5 µmol/L, respectively. When combined, TSr and TLi concentrations of all samples in the water column are higher than those of the oligotrophic water. Both volcanic eruption and submarine hydrothermal activity (e.g. volcanic ashes, particles, gas condensate) can deliver substantial amount of TSr and TLi to the water column. The distribution of TSr versus TLi evidences linear trends either with a negative or positive slope. The negative correlation is observed in the water column at both sites, directly under the influence of the eruption and in the vicinity of the volcano with hydrothermal activity. The positive TSr versus TLi correlation is observed at site under submarine hydrothermal influence and is in line with black smokers related hydrothermal plumes. The 87Sr/86Sr ratios vary between 0.709147 and 0.709210 and δ7Li values vary between +10.1 and +37.6 ‰. While 92% of the measured 87Sr/86Sr ratios are in line with the mean value of oligotrophic waters, once combined with the δ7Li values, only 20% of them remains within this field. The wide range of δ7Li values decreases from sea-surface down to ~140 mbsl, before increasing at greater depth, while defining different linear trend according to the dissolved inorganic carbon concentrations. The variability of δ7Li values reflect hydrothermal contribution, mineral–seawater interaction and potentially biology–environment interaction. In the particular geological setting of the study, where both hydrothermal and volcanic activities were at play, disentangling both contributions on water column implies a combined use of elemental and isotopic signatures of Sr and Li tracers. [ABSTRACT FROM AUTHOR]

Published
2024
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7. Composition of the sinking particle flux in a hot spot of dinitrogen fixation revealed through polyacrylamide gel traps

Author

Abadou, Fatima-ezzahra, Le Moigne, Frédéric A.c., Cornet-barthaux, Véronique, Taillandier, Vincent, Bonnet, Sophie, Abadou, Fatima-ezzahra, Le Moigne, Frédéric A.c., Cornet-barthaux, Véronique, Taillandier, Vincent, and Bonnet, Sophie

Abstract

Diazotrophs regulate marine productivity in the oligotrophic ocean by alleviating nitrogen limitation, contributing to particulate organic carbon (POC) export to the deep ocean. Yet, the characterization of particles composing the sinking POC flux has never been explored in such ecosystems. Moreover, the contribution of the direct gravitational export of diazotrophs to the overall flux is seldom assessed. Here we explore the composition of the sinking POC flux in a hot spot of N2 fixation (the western sub-tropical South Pacific) using polyacrylamide gel-filled traps deployed at two stations (S05M and S10M) and three depths (170 m, 270 m, 1000 m) during the TONGA expedition (November-December 2019). Image analyses of particles collected in the gels was used to classify them into 5 categories (fecal aggregates, phytodetrital aggregates, mixed aggregates, cylindrical fecal pellets, and zooplankton carcasses). Fecal aggregates were the most abundant at both stations and all depths and dominated the flux (average of 56 ± 28% of the POC flux), followed by zooplankton carcasses (24 ± 19%), cylindrical fecal pellets (15 ± 14%) and mixed aggregates (5 ± 4%), whereas phytodetrital aggregates contributed less (<1%). Since N isotope budgets show that export is mainly supported by diazotrophy at these stations, these results suggest that the diazotroph-derived N has been efficiently transferred to the foodweb up to zooplankton and fecal pellets before being exported, pleading for an indirect export of diazotrophy. However, random confocal microscopy examination performed on sinking particles revealed that diazotrophs were present in several categories of exported particles, suggesting that diazotrophs are also directly exported, with a potential contribution to overall POC fluxes increasing with depth. Our results provide the first characterization of particle categories composing the sinking flux and their contribution to the overall flux in a hot spot of N2 fixation.

Published
2024
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11. Phosphomonoesterase and phosphodiesterase activities in the eastern Mediterranean in two contrasting seasonal situations.

Author

Van Wambeke, France, Conan, Pascal, Pujo-Pay, Mireille, Taillandier, Vincent, Crispi, Olivier, Pavlidou, Alexandra, Nunige, Sandra, Didry, Morgane, Salmeron, Christophe, and Pulido-Villena, Elvira

Subjects
MARINE microorganisms, EXTRACELLULAR enzymes, AUTUMN, PHOSPHODIESTERS, PHOSPHORUS
Abstract

Hydrolysis of dissolved organic phosphorus by marine planktonic microorganisms is a key process in the P cycle, particularly in P -depleted, oligotrophic environments. The present study assessed spatiotemporal variations in phosphomonoesterase (PME) and phosphodiesterase (PDE) activities using concentration kinetics in the eastern Mediterranean Sea in two contrasting situations: the end of winter (including a small bloom period) and autumn. The distribution and regulation of the maximum hydrolysis rate (Vm) and half-saturation constant (Km) of both ectoenzymes were assessed in relation to the vertical structure of the epipelagic layers. PME reached its maximum activities (Vm) after the addition of 1 µM MUF-P (4-methylumbelliferyl phosphate), whereas, for PDE, it was necessary to add up to 50 µM bis(4-methylumbelliferyl)phosphate (bis-MUF-P) to reach saturation state. On average, the Km of PDE was 33 ± 25 times higher than that of PME. The Vm of PME and Vm of PDE were linearly correlated. Conversely to the Km values, Vm values were on the same order of magnitude for both ectoenzymes, with their ratio (Vm PME : Vm PDE) ranging between 0.2 and 6.3. Dissolved organic phosphorus (DOP) and the phosphomonoesterase hydrolysable fraction of DOP explained most of the lack of variability in Vm PME and Vm PDE. On the contrary, Vm of both phosphohydrolase enzymes was inversely correlated to the concentration of dissolved inorganic phosphorus. The particular characteristics of concentration kinetics obtained for PDE (saturation at 50 µM , high Km , high turnover times) are discussed with respect to the possible unequal distribution of PDE and PME among the size continuum of organic material and accessibility of phosphodiesters. [ABSTRACT FROM AUTHOR]

Published
2024
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12. Phosphomonoesterase and phosphodiesterase activities in the Eastern Mediterranean Sea during stratified versus mixed conditions

Author

Van Wambeke, France, Conan, Pascal, Pujo-pay, Mireille, Taillandier, Vincent, Crispi, Olivier, Pulido-villena, Elvira, Van Wambeke, France, Conan, Pascal, Pujo-pay, Mireille, Taillandier, Vincent, Crispi, Olivier, and Pulido-villena, Elvira

Abstract

Dissolved organic phosphorus hydrolysis by marine planktonic microorganisms is a key process in the P cycle, particularly in P-depleted, oligotrophic environments. The present study assessed spatio-temporal variations of phosphomonoesterase (PME) and phosphodiesterase (PDE) activities using concentration kinetics in the eastern Mediterranean Sea during 2 contrasted situations: the end of winter (including a small bloom period), and autumn. The distribution and regulation of the maximum hydrolysis rates (Vm) and half-saturation constants (Km) of both ectoenzymes were assessed in relation to the vertical structure of the epipelagic layers. PME reached their maximum activities (Vm) after 1 µM MUF-P addition whereas, for PDE, it was necessary to add up to 50 µM bis-MUF-P to reach saturation state. On average, the Km of PDE was 33 ± 25- times higher than that of the PME. Vm of PME and Vm of PDE were linearly correlated. Conversely to the Km values, Vm were on the same order of magnitude for both ectoenzymes, their ratio (Vm PME:Vm PDE) ranging between 0.2 and 6.3). Dissolved organic phosphorus (DOP) and the phosphomonoesterease hydrolysable fraction of DOP explained mostly no variability of Vm PME nor Vm PDE. On the contrary, Vm of both phosphohydrolase enzymes was inversely correlated to DIP concentration. The particular characteristics of concentration kinetics obtained for PDE (saturation at 50 µM, high Km, high turnovertimes) are discussed with respect to possible inequal distribution of PDE and PME among organic material size continuum, and accessibility to phosphodiesters.

Published
2023
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13. Natural iron fertilization by shallow hydrothermal sources fuels diazotroph blooms in the Ocean

Author

2., B, Guieu, C, Taillandier, V, Boulart, C, Bouruet-Aubertot, P, Gazeau, F, Scalabrin, C, Bressac Matthieu, K, Angela, N, Cuypers, Y, González-Santana, D, Forrer Heather, J, Grisoni, J, Grosso, O, Habasque, J, Jardin-Camps, M, Leblond, N, Le Moigne Frédéric, A, Lebourges-Dhaussy, A, Lory, C, Nunige, S, Pulido-Villena, E, Rizzo, A, Sarthou, G, Tilliette, C, 2. Bonnet Sophie, Guieu Cécile, Taillandier Vincent, Boulart Cédric, Bouruet-Aubertot Pascale, Gazeau Frédéric, Scalabrin Carla, Bressac Matthieu Knapp, Angela N., Cuypers Yannis, González-Santana David, Forrer Heather J., Grisoni Jean-Michel, Grosso Olivier, Habasque Jérémie, Jardin-Camps Mercedes, Leblond Nathalie, Le Moigne Frédéric A. C., Lebourges-Dhaussy Anne, Lory Caroline, Nunige Sandra, Pulido-Villena Elvira, Rizzo A, Sarthou Géraldine, Tilliette Chloé, 2., B, Guieu, C, Taillandier, V, Boulart, C, Bouruet-Aubertot, P, Gazeau, F, Scalabrin, C, Bressac Matthieu, K, Angela, N, Cuypers, Y, González-Santana, D, Forrer Heather, J, Grisoni, J, Grosso, O, Habasque, J, Jardin-Camps, M, Leblond, N, Le Moigne Frédéric, A, Lebourges-Dhaussy, A, Lory, C, Nunige, S, Pulido-Villena, E, Rizzo, A, Sarthou, G, Tilliette, C, 2. Bonnet Sophie, Guieu Cécile, Taillandier Vincent, Boulart Cédric, Bouruet-Aubertot Pascale, Gazeau Frédéric, Scalabrin Carla, Bressac Matthieu Knapp, Angela N., Cuypers Yannis, González-Santana David, Forrer Heather J., Grisoni Jean-Michel, Grosso Olivier, Habasque Jérémie, Jardin-Camps Mercedes, Leblond Nathalie, Le Moigne Frédéric A. C., Lebourges-Dhaussy Anne, Lory Caroline, Nunige Sandra, Pulido-Villena Elvira, Rizzo A, Sarthou Géraldine, and Tilliette Chloé

Abstract

Iron is an essential nutrient that regulates productivity in ~30% of the ocean. Compared with deep (>2000 meter) hydrothermal activity at mid-ocean ridges that provide iron to the ocean’s interior, shallow (<500 meter) hydrothermal fluids are likely to influence the surface’s ecosystem. However, their effect is unknown. In this work, we show that fluids emitted along the Tonga volcanic arc (South Pacific) have a substantial impact on iron concentrations in the photic layer through vertical diffusion. This enrichment stimulates biological activity, resulting in an extensive patch of chlorophyll (360,000 square kilometers). Diazotroph activity is two to eight times higher and carbon export fluxes are two to three times higher in iron-enriched waters than in adjacent unfertilized waters. Such findings reveal a previously undescribed mechanism of natural iron fertilization in the ocean that fuels regional hotspot sinks for atmospheric CO2.

Published
2023

14. Natural iron fertilization by shallow hydrothermal sources fuels diazotroph blooms in the ocean

Author

Bonnet, Sophie, primary, Guieu, Cécile, additional, Taillandier, Vincent, additional, Boulart, Cédric, additional, Bouruet-Aubertot, Pascale, additional, Gazeau, Frédéric, additional, Scalabrin, Carla, additional, Bressac, Matthieu, additional, Knapp, Angela N., additional, Cuypers, Yannis, additional, González-Santana, David, additional, Forrer, Heather J., additional, Grisoni, Jean-Michel, additional, Grosso, Olivier, additional, Habasque, Jérémie, additional, Jardin-Camps, Mercedes, additional, Leblond, Nathalie, additional, Le Moigne, Frédéric A. C., additional, Lebourges-Dhaussy, Anne, additional, Lory, Caroline, additional, Nunige, Sandra, additional, Pulido-Villena, Elvira, additional, Rizzo, Andrea L., additional, Sarthou, Géraldine, additional, and Tilliette, Chloé, additional

Published
2023
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16. Phosphomonoesterase and phosphodiesterase activities in the Eastern Mediterranean Sea during stratified versus mixed conditions.

Author

Wambeke, France Van, Conan, Pascal, Pujo-Pay, Mireille, Taillandier, Vincent, Crispi, Olivier, and Pulido-Villena, Elvira

Subjects
EXTRACELLULAR enzymes, MARINE microorganisms, SPATIO-temporal variation, AUTUMN, PHOSPHODIESTERS, PHOSPHATASES
Abstract

Dissolved organic phosphorus hydrolysis by marine planktonic microorganisms is a key process in the P cycle, particularly in P-depleted, oligotrophic environments. The present study assessed spatio-temporal variations of phosphomonoesterase (PME) and phosphodiesterase (PDE) activities using concentration kinetics in the eastern Mediterranean Sea during 2 contrasted situations: the end of winter (including a small bloom period), and autumn. The distribution and regulation of the maximum hydrolysis rates (Vm) and half-saturation constants (Km) of both ectoenzymes were assessed in relation to the vertical structure of the epipelagic layers. PME reached their maximum activities (Vm) after 1 µM MUF-P addition whereas, for PDE, it was necessary to add up to 50 µM bis-MUF-P to reach saturation state. On average, the Km of PDE was 33 ± 25- times higher than that of the PME. Vm of PME and Vm of PDE were linearly correlated. Conversely to the Km values, Vm were on the same order of magnitude for both ectoenzymes, their ratio (Vm PME:Vm PDE) ranging between 0.2 and 6.3). Dissolved organic phosphorus (DOP) and the phosphomonoesterease hydrolysable fraction of DOP explained mostly no variability of Vm PME nor Vm PDE. On the contrary, Vm of both phosphohydrolase enzymes was inversely correlated to DIP concentration. The particular characteristics of concentration kinetics obtained for PDE (saturation at 50 µM, high Km, high turnovertimes) are discussed with respect to possible inequal distribution of PDE and PME among organic material size continuum, and accessibility to phosphodiesters. [ABSTRACT FROM AUTHOR]

Published
2023
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19. DFe patterns impacted by shallow hydrothermal sources along a transect through the Tonga-Kermadec arc

Author

Tilliette, Chloé, Taillandier, Vincent, Bouruet-aubertot, Pascale, Grima, Nicolas, Maes, Christophe, Montanes, Maryline, Sarthou, Geraldine, Vorrath, Maria-elena, Arnone, Veronica, Bressac, Matthieu, González-santana, David, Gazeau, Frédéric, Guieu, Cécile, Tilliette, Chloé, Taillandier, Vincent, Bouruet-aubertot, Pascale, Grima, Nicolas, Maes, Christophe, Montanes, Maryline, Sarthou, Geraldine, Vorrath, Maria-elena, Arnone, Veronica, Bressac, Matthieu, González-santana, David, Gazeau, Frédéric, and Guieu, Cécile

Abstract

In the Western Tropical South Pacific, a hotspot of N2-fixing organisms has recently been identified. The survival of these species depends on the availability of dissolved iron (dFe). dFe was measured along a transect from 175 °E to 166 °W near 19-21 °S. The distribution of dFe showed high spatial variability: low concentrations (~0.2 nmol kg-1) in the South Pacific gyre and high concentrations (up to 50 nmol kg-1) west of the Tonga arc, indicating that this arc is a clear boundary between iron-poor and iron-rich waters. An optimal multiparameter analysis was used to distinguish the relative importance of physical transport relative to non-conservative processes on the observed dFe distribution. This analysis demonstrated that distant sources of iron play a minor role in its distribution along the transect. The high concentrations observed were therefore attributed to shallow hydrothermal sources massively present along the Tonga-Kermadec arc. Nevertheless, in contrast to what has been observed for deep hydrothermal plumes, our results highlighted the rapid decrease in dFe concentrations near shallow hydrothermal sources. This is likely due to a shorter residence time of surface water masses combined with several biogeochemical processes at play (e.g., precipitation, photoreduction, scavenging, biological uptake). This study clearly highlights the role of shallow hydrothermal sources on the dFe cycle within the Tonga-Kermadec arc where a strong link to biological activity in surface waters can be assessed. It also emphasizes the need to consider the impact of these shallow hydrothermal sources for a better understanding of the global iron cycle.

Published
2022
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20. Biological production in two contrasted regions of the Mediterranean Sea during the oligotrophic period: An estimate based on the diel cycle of optical properties measured by BGC-Argo profiling floats

Author

Barbieux, Marie, Uitz, Julia, Mignot, Alexandre, Roesler, Collin, Claustre, Hervé, Gentili, Bernard, Taillandier, Vincent, D'Ortenzio, Fabrizio, Loisel, Hubert, Poteau, Antoine, Leymarie, Edouard, Penkerc'H, Christophe, Schmechtig, Catherine, Bricaud, Annick, Barbieux, Marie, Uitz, Julia, Mignot, Alexandre, Roesler, Collin, Claustre, Hervé, Gentili, Bernard, Taillandier, Vincent, D'Ortenzio, Fabrizio, Loisel, Hubert, Poteau, Antoine, Leymarie, Edouard, Penkerc'H, Christophe, Schmechtig, Catherine, and Bricaud, Annick

Abstract

This study assesses marine biological production of organic carbon based on the diel variability of bio-optical properties monitored by two BioGeoChemical-Argo (BGC-Argo) floats. Experiments were conducted in two distinct Mediterranean systems, the Northwestern Ligurian Sea and the Central Ionian Sea during summer months. We derived particulate organic carbon (POC) stock and gross community production integrated within the surface, euphotic and subsurface chlorophyll maximum (SCM) layers, using an existing approach applied to diel cycle measurements of the particulate beam attenuation (cp) and backscattering (bbp) coefficients. The diel cycle of cp provided a robust proxy for quantifying biological production in both systems; that of bbp was comparatively less robust. Derived primary production estimates vary by a factor of 2 depending upon the choice of the bio-optical relationship that converts the measured optical coefficient to POC, which is thus a critical step to constrain. Our results indicate a substantial, yet variable, contribution to the water column production of the SCM layer (16–42%). In the Ligurian Sea, the SCM is a seasonal feature that behaves as a subsurface biomass maximum (SBM) with the ability to respond to episodic abiotic forcing by increasing production. In contrast, in the Ionian Sea, the SCM is permanent, induced by phytoplankton photoacclimation and contributes moderately to water column production. These results emphasize the strong potential for transmissometers deployed on BGC-Argo profiling floats to quantify non-intrusively in situ biological production of organic carbon in the water column of stratified oligotrophic systems with recurring or permanent SCMs, which are widespread features in the global ocean.

Published
2022
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21. N2 fixation in the Mediterranean Sea related to the composition of the diazotrophic community, and impact of dust under present and future environmental conditions

Author

Ridame, Céline, Dinasquet, Julie, Hallstrøm, Søren, Bigeard, Estelle, Riemann, Lasse, Van Wambeke, France, Bressac, Matthieu, Pulido-villena, Elvira, Taillandier, Vincent, Gazeau, Frederic, Tover-sanchez, Antonio, Baudoux, Anne-claire, Guieu, Cécile, Ridame, Céline, Dinasquet, Julie, Hallstrøm, Søren, Bigeard, Estelle, Riemann, Lasse, Van Wambeke, France, Bressac, Matthieu, Pulido-villena, Elvira, Taillandier, Vincent, Gazeau, Frederic, Tover-sanchez, Antonio, Baudoux, Anne-claire, and Guieu, Cécile

Published
2022
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22. N2 fixation in the Mediterranean Sea related to the composition of the diazotrophic community and impact of dust under present and future environmental conditions

Author

Centre National de la Recherche Scientifique (France), European Commission, Danish Council for Independent Research, Ridame, Céline, Dinasquet, Julie, Hallstrøm, Søren, Bigeard, Estelle, Riemann, Lasse, Wambeke, France van, Bressac, Matthieu, Pulido-Villena, Elvira, Taillandier, Vincent, Gazeau, Frédéric, Tovar-Sánchez, Antonio, Baudoux, Anne Claire, Guieu, Cécile, Centre National de la Recherche Scientifique (France), European Commission, Danish Council for Independent Research, Ridame, Céline, Dinasquet, Julie, Hallstrøm, Søren, Bigeard, Estelle, Riemann, Lasse, Wambeke, France van, Bressac, Matthieu, Pulido-Villena, Elvira, Taillandier, Vincent, Gazeau, Frédéric, Tovar-Sánchez, Antonio, Baudoux, Anne Claire, and Guieu, Cécile

Abstract

N2 fixation rates were measured in the 0-1000ĝ€¯m layer at 13 stations located in the open western and central Mediterranean Sea (MS) during the PEACETIME cruise (late spring 2017). While the spatial variability in N2 fixation was not related to Fe, P nor N stocks, the surface composition of the diazotrophic community indicated a strong longitudinal gradient increasing eastward for the relative abundance of non-cyanobacterial diazotrophs (NCDs) (mainly 3-Proteobacteria) and conversely decreasing eastward for photo-heterotrophic group A (UCYN-A) (mainly UCYN-A1 and UCYN-A3), as did N2 fixation rates. UCYN-A4 and UCYN-A3 were identified for the first time in the MS. The westernmost station influenced by Atlantic waters and characterized by highest stocks of N and P displayed a patchy distribution of diazotrophic activity with an exceptionally high rate in the euphotic layer of 72.1ĝ€¯nmolNL-1d-1, which could support up to 19ĝ€¯% of primary production. At this station at 1ĝ€¯%PAR (photosynthetically available radiation) depth, UCYN-A4 represented up to 94ĝ€¯% of the diazotrophic community. These in situ observations of greater relative abundance of UCYN-A at stations with higher nutrient concentrations and dominance of NCDs at more oligotrophic stations suggest that nutrient conditions-even in the nanomolar range-may determine the composition of diazotrophic communities and in turn N2 fixation rates. The impact of Saharan dust deposition on N2 fixation and diazotrophic communities was also investigated, under present and future projected conditions of temperature and pH during short-Term (3-4ĝ€¯d) experiments at three stations. New nutrients from simulated dust deposition triggered a significant stimulation of N2 fixation (from 41ĝ€¯% to 565ĝ€¯%). The strongest increase in N2 fixation was observed at the stations dominated by NCDs and did not lead on this short timescale to changes in the diazotrophic community composition. Under projected future conditions, N2 fixatio

Published
2022

23. Dissolved iron pattern impacted by shallow hydrothermal sources along a transect through the Tonga-Kermadec arc

Author

Tilliette, Chloé, Taillandier, Vincent, Bouruet-Aubertot, Pascale, Grima, Nicolas, Maes, Christophe, Montanes, Maryline, Sarthou, Géraldine, Vorrath, Maria-Elena, Arnone, Verónica, Bressac, Matthieu, González-Santana, David, Gazeau, Frédéric, Guieu, Cécile, Laboratoire d'océanographie de Villefranche (LOV), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut de la Mer de Villefranche (IMEV), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Processus et interactions de fine échelle océanique (PROTEO), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Laboratoire d'Océanographie Physique et Spatiale (LOPS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Instituto de Oceanografía y Cambio Global (IOCAG), and Université de Las Palmas de Gran Canaria [Espagne] (ULPGC)

Subjects
Changement climatique, [SDE]Environmental Sciences, Climate change
Published
2022

24. Sugar bowl

Author

Taillandier, Vincent, Sèvres Porcelain Manufactory, and Museum of Fine Arts, Boston

Subjects
European, French, France
Published
1753

25. Tray

Author

Sèvres Porcelain Manufactory, Taillandier, Vincent, and Museum of Fine Arts, Boston

Subjects
European, French, France
Published
1756

26. Cup and saucer

Author

Sèvres Porcelain Manufactory, Taillandier, Vincent, and Museum of Fine Arts, Boston

Subjects
European, French, France
Published
1756

27. Cream jug

Author

Sèvres Porcelain Manufactory, Taillandier, Vincent, and Museum of Fine Arts, Boston

Subjects
European, French, France
Published
1756

28. Pair of covered vases

Author

Sèvres Porcelain Manufactory, Taillandier, Vincent, and The Minneapolis Institute of Arts

Subjects
European, French
Published
1790

29. Using machine learning and Biogeochemical-Argo (BGC-Argo) floats to assess biogeochemical models and optimize observing system design.

Author

Mignot, Alexandre, Claustre, Hervé, Cossarini, Gianpiero, D'Ortenzio, Fabrizio, Gutknecht, Elodie, Lamouroux, Julien, Lazzari, Paolo, Perruche, Coralie, Salon, Stefano, Sauzède, Raphaëlle, Taillandier, Vincent, and Teruzzi, Anna

Subjects
SYSTEMS design, MACHINE learning, MARINE resources, MIXING height (Atmospheric chemistry), MARINE ecosystem health, MARINE service, BIOGEOCHEMISTRY
Abstract

Numerical models of ocean biogeochemistry are becoming the major tools used to detect and predict the impact of climate change on marine resources and to monitor ocean health. However, with the continuous improvement of model structure and spatial resolution, incorporation of these additional degrees of freedom into fidelity assessment has become increasingly challenging. Here, we propose a new method to provide information on the model predictive skill in a concise way. The method is based on the conjoint use of a k -means clustering technique, assessment metrics, and Biogeochemical-Argo (BGC-Argo) observations. The k -means algorithm and the assessment metrics reduce the number of model data points to be evaluated. The metrics evaluate either the model state accuracy or the skill of the model with respect to capturing emergent properties, such as the deep chlorophyll maximums and oxygen minimum zones. The use of BGC-Argo observations as the sole evaluation data set ensures the accuracy of the data, as it is a homogenous data set with strict sampling methodologies and data quality control procedures. The method is applied to the Global Ocean Biogeochemistry Analysis and Forecast system of the Copernicus Marine Service. The model performance is evaluated using the model efficiency statistical score, which compares the model–observation misfit with the variability in the observations and, thus, objectively quantifies whether the model outperforms the BGC-Argo climatology. We show that, overall, the model surpasses the BGC-Argo climatology in predicting pH, dissolved inorganic carbon, alkalinity, oxygen, nitrate, and phosphate in the mesopelagic and the mixed layers as well as silicate in the mesopelagic layer. However, there are still areas for improvement with respect to reducing the model–data misfit for certain variables such as silicate, pH, and the partial pressure of CO 2 in the mixed layer as well as chlorophyll- a -related, oxygen-minimum-zone-related, and particulate-organic-carbon-related metrics. The method proposed here can also aid in refining the design of the BGC-Argo network, in particular regarding the regions in which BGC-Argo observations should be enhanced to improve the model accuracy via the assimilation of BGC-Argo data or process-oriented assessment studies. We strongly recommend increasing the number of observations in the Arctic region while maintaining the existing high-density of observations in the Southern Oceans. The model error in these regions is only slightly less than the variability observed in BGC-Argo measurements. Our study illustrates how the synergic use of modeling and BGC-Argo data can both provide information about the performance of models and improve the design of observing systems. [ABSTRACT FROM AUTHOR]

Published
2023
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30. Biological production in two contrasted regions of the Mediterranean Sea during the oligotrophic period: an estimate based on the diel cycle of optical properties measured by BioGeoChemical-Argo profiling floats

Author

Barbieux, Marie, primary, Uitz, Julia, additional, Mignot, Alexandre, additional, Roesler, Collin, additional, Claustre, Hervé, additional, Gentili, Bernard, additional, Taillandier, Vincent, additional, D'Ortenzio, Fabrizio, additional, Loisel, Hubert, additional, Poteau, Antoine, additional, Leymarie, Edouard, additional, Penkerc'h, Christophe, additional, Schmechtig, Catherine, additional, and Bricaud, Annick, additional

Published
2022
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31. DFe patterns impacted by shallow hydrothermal sources along a transect through the Tonga-Kermadec arc

Author

Tilliette, Chloé, primary, Taillandier, Vincent, additional, Bouruet-Aubertot, Pascale, additional, Grima, Nicolas, additional, Maes, Christophe, additional, Montanes, Maryline, additional, Sarthou, Geraldine, additional, Vorrath, Maria-Elena, additional, Arnone, Veronica, additional, Bressac, Matthieu, additional, González-Santana, David, additional, GAZEAU, Frédéric, additional, and Guieu, Cécile, additional

Published
2022
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32. N&lt;sub&gt;2&lt;/sub&gt; fixation in the Mediterranean Sea related to the composition of the diazotrophic community and impact of dust under present and future environmental conditions

Author

Ridame, Céline, primary, Dinasquet, Julie, additional, Hallstrøm, Søren, additional, Bigeard, Estelle, additional, Riemann, Lasse, additional, Van Wambeke, France, additional, Bressac, Matthieu, additional, Pulido-Villena, Elvira, additional, Taillandier, Vincent, additional, Gazeau, Fréderic, additional, Tovar-Sanchez, Antonio, additional, Baudoux, Anne-Claire, additional, and Guieu, Cécile, additional

Published
2022
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33. Subsurface iron accumulation and rapid aluminum removal in the Mediterranean following African dust deposition

Author

Bressac, Matthieu, primary, Wagener, Thibaut, additional, Leblond, Nathalie, additional, Tovar-Sánchez, Antonio, additional, Ridame, Céline, additional, Taillandier, Vincent, additional, Albani, Samuel, additional, Guasco, Sophie, additional, Dufour, Aurélie, additional, Jacquet, Stéphanie H. M., additional, Dulac, François, additional, Desboeufs, Karine, additional, and Guieu, Cécile, additional

Published
2021
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35. N2 fixation in the Mediterranean Sea related to the composition of the diazotrophic community, and impact of dust under present and future environmental conditions

Author

Ridame, Céline, Dinasquet, Julie, Hallstrøm, Søren, Bigeard, Estelle, Riemann, Lasse, van Wambeke, France, Bressac, Matthieu, Pulido-Villena, Elvira, Taillandier, Vincent, Gazeau, Frédéric, Tovar-Sánchez, Antonio, Baudoux, Anne-Claire, Guieu, Cécile, Cycles biogéochimiques marins : processus et perturbations (CYBIOM), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Scripps Institution of Oceanography (SIO - UC San Diego), University of California [San Diego] (UC San Diego), University of California (UC)-University of California (UC), Laboratoire d'Océanographie Microbienne (LOMIC), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Observatoire océanologique de Banyuls (OOB), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), University of Copenhagen = Københavns Universitet (UCPH), Adaptation et diversité en milieu marin (ADMM), Institut national des sciences de l'Univers (INSU - CNRS)-Station biologique de Roscoff (SBR), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut méditerranéen d'océanologie (MIO), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'océanographie de Villefranche (LOV), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut de la Mer de Villefranche (IMEV), Institute of Marine Sciences of Andalusia (ICMAN), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Sorbonne Université (SU), Centre National de la Recherche Scientifique (CNRS), Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU), Scripps Institution of Oceanography (SIO), University of California-University of California, Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire océanologique de Banyuls (OOB), University of Copenhagen = Københavns Universitet (KU), Adaptation et diversité en milieu marin (AD2M), Station biologique de Roscoff (SBR), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), PEACETIME project (http://peacetime-project.org), GEOTRACES, Centre National de la Recherche Scientifique (France), European Commission, Danish Council for Independent Research, and Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU]Sciences of the Universe [physics], [SDE]Environmental Sciences, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography
Abstract

N2 fixation rates were measured in the 0-1000ĝ€¯m layer at 13 stations located in the open western and central Mediterranean Sea (MS) during the PEACETIME cruise (late spring 2017). While the spatial variability in N2 fixation was not related to Fe, P nor N stocks, the surface composition of the diazotrophic community indicated a strong longitudinal gradient increasing eastward for the relative abundance of non-cyanobacterial diazotrophs (NCDs) (mainly 3-Proteobacteria) and conversely decreasing eastward for photo-heterotrophic group A (UCYN-A) (mainly UCYN-A1 and UCYN-A3), as did N2 fixation rates. UCYN-A4 and UCYN-A3 were identified for the first time in the MS. The westernmost station influenced by Atlantic waters and characterized by highest stocks of N and P displayed a patchy distribution of diazotrophic activity with an exceptionally high rate in the euphotic layer of 72.1ĝ€¯nmolNL-1d-1, which could support up to 19ĝ€¯% of primary production. At this station at 1ĝ€¯%PAR (photosynthetically available radiation) depth, UCYN-A4 represented up to 94ĝ€¯% of the diazotrophic community. These in situ observations of greater relative abundance of UCYN-A at stations with higher nutrient concentrations and dominance of NCDs at more oligotrophic stations suggest that nutrient conditions-even in the nanomolar range-may determine the composition of diazotrophic communities and in turn N2 fixation rates. The impact of Saharan dust deposition on N2 fixation and diazotrophic communities was also investigated, under present and future projected conditions of temperature and pH during short-Term (3-4ĝ€¯d) experiments at three stations. New nutrients from simulated dust deposition triggered a significant stimulation of N2 fixation (from 41ĝ€¯% to 565ĝ€¯%). The strongest increase in N2 fixation was observed at the stations dominated by NCDs and did not lead on this short timescale to changes in the diazotrophic community composition. Under projected future conditions, N2 fixation was either increased or unchanged; in that later case this was probably due to a too-low nutrient bioavailability or an increased grazing pressure. The future warming and acidification likely benefited NCDs (Pseudomonas) and UCYN-A2, while disadvantaged UCYN-A3 without knowing which effect (alone or in combination) is the driver, especially since we do not know the temperature optima of these species not yet cultivated as well as the effect of acidification., This study is a contribution to the PEACETIME project (http://peacetime-project.org, last access: 17 January 2022), a joint initiative of the MERMEX and ChArMEx components supported by the CNRS-INSU, IFREMER, CEA and Météo-France as part of the program MISTRALS coordinated by the INSU. PEACETIME was endorsed as a process study by GEOTRACES. Julie Dinasquet was funded by a Marie Curie Actions International Outgoing Fellowship (PIOF-GA-2013-629378). Søren Hallstrøm and Lasse Riemann were funded by grant 6108-00013 from the Danish Council for Independent Research.

Published
2021
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36. Phosphorus cycling in the upper waters of the Mediterranean Sea (PEACETIME cruise): relative contribution of external and internal sources

Author

Pulido-Villena, Elvira, primary, Desboeufs, Karine, additional, Djaoudi, Kahina, additional, Van Wambeke, France, additional, Barrillon, Stéphanie, additional, Doglioli, Andrea, additional, Petrenko, Anne, additional, Taillandier, Vincent, additional, Fu, Franck, additional, Gaillard, Tiphanie, additional, Guasco, Sophie, additional, Nunige, Sandra, additional, Triquet, Sylvain, additional, and Guieu, Cécile, additional

Published
2021
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39. Spatial patterns of ectoenzymatic kinetics in relation to biogeochemical properties in the Mediterranean Sea and the concentration of the fluorogenic substrate used

Author

Van Wambeke, France, Pulido, Elvira, Catala, Philippe, Dinasquet, Julie, Djaoudi, Kahina, Engel, Anja, Garel, Marc, Guasco, Sophie, Marie, Barbara, Nunige, Sandra, Taillandier, Vincent, Zäncker, Birthe, Tamburini, Christian, Institut méditerranéen d'océanologie (MIO), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Toulon (UTLN), Laboratoire d'Océanographie Microbienne (LOMIC), Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire océanologique de Banyuls (OOB), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093, Helmholtz Centre for Ocean Research [Kiel] (GEOMAR), Laboratoire d'océanographie de Villefranche (LOV), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut de la Mer de Villefranche (IMEV), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), The Laboratory (Marine Biological Association of the United Kingdom), Marine Biological Association of the United Kingdom (MBA), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Observatoire océanologique de Banyuls (OOB), Scripps Institution of Oceanography (SIO - UC San Diego), University of California [San Diego] (UC San Diego), and University of California (UC)-University of California (UC)

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, ComputingMilieux_MISCELLANEOUS
Abstract

Ectoenzymatic activity, prokaryotic heterotrophic abundances and production were determined in the Mediterranean Sea. Sampling was carried out in the sub-surface, the deep chlorophyll maximum layer (DCM), the core of the Levantine intermediate waters and in the deeper part of the mesopelagic layers. Michaelis–Menten kinetics were assessed using a large range of concentrations of fluorogenic substrates (0.025 to 50 µM). As a consequence, Km (Michaelis–Menten half-saturation constant) and Vm (maximum hydrolysis velocity) parameters were determined for both low- and high-affinity enzymes for alkaline phosphatase, aminopeptidase (LAP) and β-glucosidase (βGLU). Based on the constant derived from the high-LAP-affinity enzyme (0.025–1 µM substrate concentration range), in situ hydrolysis of N proteins contributed 48 % ± 30 % to the heterotrophic bacterial nitrogen demand within the epipelagic layers and 180 % ± 154 % in the Levantine intermediate waters and the upper part of the mesopelagic layers. The LAP hydrolysis rate was higher than bacterial N demand only within the deeper layer and only when considering the high-affinity enzyme. Based on a 10 % bacterial growth efficiency, the cumulative hydrolysis rates of C proteins and C polysaccharides contributed on average 2.5 % ± 1.3 % to the heterotrophic bacterial carbon demand in the epipelagic layers sampled (sub-surface and DCM). This study clearly reveals potential biases in current and past interpretations of the kinetic parameters for the three enzymes tested based on the fluorogenic-substrate concentration used. In particular, the LAP / βGLU enzymatic ratios and some of the depth-related trends differed between the use of high and low concentrations of fluorogenic substrates.

Published
2021
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40. Océanographie physique de la mer Ligure

Author

Prieur, Louis, D'Ortenzio, Fabrizio, Taillandier, Vincent, Testor, Pierre, Laboratoire d'océanographie de Villefranche (LOV), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut de la Mer de Villefranche (IMEV), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Variabilité de l'Océan et de la Glace de mer (VOG), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU), Chistophe Migon, Antoine Sciandra, Paul Nival, Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)

Subjects
[SDE]Environmental Sciences, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2021

41. Supplementary material to "N2 fixation in the Mediterranean Sea related to the composition of the diazotrophic community, and impact of dust under present and future environmental conditions"

Author

Ridame, Céline, primary, Dinasquet, Julie, additional, Hallstrøm, Søren, additional, Bigeard, Estelle, additional, Riemann, Lasse, additional, Van Wambeke, France, additional, Bressac, Matthieu, additional, Pulido-Villena, Elvira, additional, Taillandier, Vincent, additional, Gazeau, Frederic, additional, Tover-Sanchez, Antonio, additional, Baudoux, Anne-Claire, additional, and Guieu, Cécile, additional

Published
2021
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42. N2 fixation in the Mediterranean Sea related to the composition of the diazotrophic community, and impact of dust under present and future environmental conditions

Author

Ridame, Céline, primary, Dinasquet, Julie, additional, Hallstrøm, Søren, additional, Bigeard, Estelle, additional, Riemann, Lasse, additional, Van Wambeke, France, additional, Bressac, Matthieu, additional, Pulido-Villena, Elvira, additional, Taillandier, Vincent, additional, Gazeau, Frederic, additional, Tover-Sanchez, Antonio, additional, Baudoux, Anne-Claire, additional, and Guieu, Cécile, additional

Published
2021
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43. Preparing the New Phase of Argo: Scientific Achievements of the NAOS Project

Author

Le Traon, Pierre-yves, D'Ortenzio, Fabrizio, Babin, Marcel, Leymarie, Edouard, Marec, Claudie, Pouliquen, Sylvie, Thierry, Virginie, Cabanes, Cecile, Claustre, Hervé, Desbruyeres, Damien, Lacour, Leo, Lagunas, Jose-luis, Maze, Guillaume, Mercier, Herle, Penkerc'H, Christophe, Poffa, Noe, Poteau, Antoine, Prieur, Louis, Racape, Virginie, Randelhoff, Achim, Rehm, Eric, Schmechtig, Catherine Marie, Taillandier, Vincent, Wagener, Thibaut, Xing, Xiaogang, Mercator Océan, Société Civile CNRS Ifremer IRD Météo-France SHOM, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Laboratoire d'océanographie de Villefranche (LOV), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut de la Mer de Villefranche (IMEV), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Takuvik Joint International Laboratory ULAVAL-CNRS, Université Laval [Québec] (ULaval)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Laboratoire d'Océanographie Physique et Spatiale (LOPS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Observatoire des sciences de l'univers Ecce Terra [Paris] (OSU ECCE TERRA), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut méditerranéen d'océanologie (MIO), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS), State Key Laboratory of Satellite Ocean Environment Dynamics (SOED), State Oceanic Administration (SOA), Institut national des sciences de l'Univers (INSU - CNRS), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Toulon (UTLN), Université Laval [Québec] (ULaval)-Centre National de la Recherche Scientifique (CNRS), Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Observatoire des sciences de l'univers Ecce Terra (ECCE TERRA), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), and Observatoire des sciences de l'univers Ecce Terra [Paris] (ECCE TERRA)

Subjects
deep ocean, Arctic, Argo, biogeochemistry, profiling floats, [SDE]Environmental Sciences, Mediterranean Sea, Atlantic, ComputingMilieux_MISCELLANEOUS, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography
Abstract

International audience; Argo, the international array of profiling floats, is a major component of the global ocean and climate observing system. In 2010, the NAOS (Novel Argo Observing System) project was selected as part of the French "Investissements d'Avenir" Equipex program. The objectives of NAOS were to consolidate the French contribution to Argo's core mission (global temperature and salinity measurements down to 2000 m), and also to develop the future generation of French Argo profiling floats and prepare the next phase of the Argo program with an extension to the deep ocean (Deep Argo), biogeochemistry (BGC-Argo) and polar seas. This paper summarizes how NAOS has met its objectives. The project significantly boosted France's contribution to Argo's core mission by deploying more than 100 NAOS standard Argo profiling floats. In addition, NAOS deployed new-generation floats as part of three scientific experiments: biogeochemical floats in the Mediterranean Sea, biogeochemical floats in the Arctic Ocean, and deep floats with oxygen sensors in the North Atlantic. The experiment in the Mediterranean Sea, launched in 2012, implemented and maintained a network of BGC-Argo floats at basin scale for the first time. The 32 BGC-Argo floats deployed and about 4000 BGC profiles collected have vastly improved characterization of the biogeochemical and ecosystem dynamics of the Mediterranean. Meanwhile, experiments in the Arctic and in the North Atlantic, starting in 2015 and deploying 20 Arctic BGC floats and 23 deep floats, have provided unique observations on biogeochemical cycles in the Arctic and deep-water masses, as well as ocean circulation variability in the North Atlantic. NAOS has therefore paved the way to the new operational phase of the Argo program in France that includes BGC and Deep Argo extensions. The objectives and characteristics of this new phase of Argo-France are discussed in the conclusion.

Published
2020
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44. Deep maxima of phytoplankton biomass, primary production and bacterial production in the Mediterranean Sea

Author

Maranon, Emilio, Van Vambeke, France, Uitz, Julia, Boss, Emmanuel S, Dimier, Céline, Dinasquet, Julie, Engel, Anja, Haentjens, Nils, Perez-lorenzo, Maria, Taillandier, Vincent, Zancker, Birthe, Maranon, Emilio, Van Vambeke, France, Uitz, Julia, Boss, Emmanuel S, Dimier, Céline, Dinasquet, Julie, Engel, Anja, Haentjens, Nils, Perez-lorenzo, Maria, Taillandier, Vincent, and Zancker, Birthe

Abstract

The deep chlorophyll maximum (DCM) is a ubiquitous feature of phytoplankton vertical distribution in stratified waters that is relevant to our understanding of the mechanisms that underpin the variability in photoautotroph ecophysiology across environmental gradients and has implications for remote sensing of aquatic productivity. During the PEACETIME (Process studies at the air-sea interface after dust deposition in the Mediterranean Sea) cruise, carried out from 10 May to 11 June 2017, we obtained 23 concurrent vertical profiles of phytoplankton chlorophyll a, carbon biomass and primary production, as well as heterotrophic prokaryotic production, in the western and central Mediterranean basins. Our main aims were to quantify the relative role of photoacclimation and enhanced growth as underlying mechanisms of the DCM and to assess the trophic coupling between phytoplankton and heterotrophic prokaryotic production. We found that the DCM coincided with a maximum in both the biomass and primary production but not in the growth rate of phytoplankton, which averaged 0.3 d−1 and was relatively constant across the euphotic layer. Photoacclimation explained most of the increased chlorophyll a at the DCM, as the ratio of carbon to chlorophyll a (C:Chl a) decreased from ca. 90–100 (g:g) at the surface to 20–30 at the base of the euphotic layer, while phytoplankton carbon biomass increased from ca. 6 mg C m−3 at the surface to 10–15 mg C m−3 at the DCM. As a result of photoacclimation, there was an uncoupling between chlorophyll a-specific and carbon-specific productivity across the euphotic layer. The ratio of fucoxanthin to total chlorophyll a increased markedly with depth, suggesting an increased contribution of diatoms at the DCM. The increased biomass and carbon fixation at the base of the euphotic zone was associated with enhanced rates of heterotrophic prokaryotic activity, which also showed a surface peak linked with warmer temperatures. Considering the phytoplankton

Published
2021
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45. Seasonal and Interannual Variability of the CO2 System in the Eastern Mediterranean Sea: A Case Study in the North Western Levantine Basin

Author

Wimart-rousseau, Cathy, Wagener, Thibaut, Álvarez, Marta, Moutin, Thierry, Fourrier, Marine, Coppola, Laurent, Niclas-chirurgien, Laure, Raimbault, Patrick, D’ortenzio, Fabrizio, Durrieu De Madron, Xavier, Taillandier, Vincent, Dumas, Franck, Conan, Pascal, Pujo-pay, Mireille, Lefèvre, Dominique, Wimart-rousseau, Cathy, Wagener, Thibaut, Álvarez, Marta, Moutin, Thierry, Fourrier, Marine, Coppola, Laurent, Niclas-chirurgien, Laure, Raimbault, Patrick, D’ortenzio, Fabrizio, Durrieu De Madron, Xavier, Taillandier, Vincent, Dumas, Franck, Conan, Pascal, Pujo-pay, Mireille, and Lefèvre, Dominique

Abstract

The seasonal variability of the carbonate system in the eastern Mediterranean Sea (EMed) was investigated based on discrete total alkalinity (AT), total dissolved inorganic carbon (CT), and pH measurements collected during three cruises around Crete between June 2018 and March 2019. This study presents a detailed description of this new carbonate chemistry dataset in the eastern Mediterranean Sea. We show that the North Western Levantine Basin (NWLB) is unique in terms of range of AT variation vs. CT variation in the upper water column over an annual cycle. The reasons for this singularity of the NWLB can be explained by the interplay between strong evaporation and the concomitant consumption of CT by autotrophic processes. The high range of AT variations, combined to temperature changes, has a strong impact on the variability of the seawater pCO2 (pCO2SW). Based on Argo float data, an entire annual cycle for pCO2SW in the NWLB has been reconstructed in order to estimate the temporal sequence of the potential “source” and “sink” of atmospheric CO2. By combining this dataset with previous observations in the NWLB, this study shows a significant ocean acidification and a decrease in the oceanic surface pHT25 of −0.0024 ± 0.0004 pHT25 units.a–1. The changes in the carbonate system are driven by the increase of atmospheric CO2 but also by unexplained temporal changes in the surface AT content. If we consider that the EMed will, in the future, encounter longer, more intense and warmer summer seasons, this study proposes some perspectives on the carbonate system functioning of the “future” EMed.

Published
2021
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46. Subsurface iron accumulation and rapid aluminum removal in the Mediterranean following African dust deposition

Author

Bressac, M, Wagener, T, Leblond, N, Tovar-Sánchez, A, Ridame, C, Taillandier, V, Albani, S, Guasco, S, Dufour, A, Jacquet, S, Dulac, F, Desboeufs, K, Guieu, C, Bressac, Matthieu, Wagener, Thibaut, Leblond, Nathalie, Tovar-Sánchez, Antonio, Ridame, Céline, Taillandier, Vincent, Albani, Samuel, Guasco, Sophie, Dufour, Aurélie, Jacquet, Stéphanie H. M., Dulac, François, Desboeufs, Karine, Guieu, Cécile, Bressac, M, Wagener, T, Leblond, N, Tovar-Sánchez, A, Ridame, C, Taillandier, V, Albani, S, Guasco, S, Dufour, A, Jacquet, S, Dulac, F, Desboeufs, K, Guieu, C, Bressac, Matthieu, Wagener, Thibaut, Leblond, Nathalie, Tovar-Sánchez, Antonio, Ridame, Céline, Taillandier, Vincent, Albani, Samuel, Guasco, Sophie, Dufour, Aurélie, Jacquet, Stéphanie H. M., Dulac, François, Desboeufs, Karine, and Guieu, Cécile

Abstract

Mineral dust deposition is an important supply mechanism for trace elements in the low-latitude ocean. Our understanding of the controls of such inputs has been mostly built on laboratory and surface ocean studies. The lack of direct observations and the tendency to focus on near-surface waters prevent a comprehensive evaluation of the role of dust in oceanic biogeochemical cycles. In the frame of the PEACETIME project (ProcEss studies at the Air-sEa Interface after dust deposition in the MEditerranean sea), the responses of the aluminum (Al) and iron (Fe) cycles to two dust wet deposition events over the central and western Mediterranean Sea were investigated at a timescale of hours to days using a comprehensive dataset gathering dissolved and suspended particulate concentrations, along with sinking fluxes. Dissolved Al (dAl) removal was dominant over dAl released from dust. The Fe/Al ratio of suspended and sinking particles revealed that biogenic particles, and in particular diatoms, were key in accumulating and exporting Al relative to Fe. By combining these observations with published Al/Si ratios of diatoms, we show that adsorption onto biogenic particles, rather than active uptake, represents the main sink for dAl in Mediterranean waters. In contrast, systematic dissolved Fe (dFe) accumulation occurred in subsurface waters (∼ 100-1000m), while dFe input from dust was only transient in the surface mixed layer. The rapid transfer of dust to depth, the Fe-binding ligand pool in excess to dFe in subsurface (while nearly saturated in surface), and low scavenging rates in this particle-poor depth horizon are all important drivers of this subsurface dFe enrichment. At the annual scale, this previously overlooked mechanism may represent an additional pathway of dFe supply for the surface ocean through diapycnal diffusion and vertical mixing. However, low subsurface dFe concentrations observed at the basin scale (<0.5nmolkg-1) cause us to question the residence time

Published
2021

47. Wind-Forced Submesoscale Symmetric Instability around Deep Convection in the Northwestern Mediterranean Sea

Author

Bosse, Anthony, Testor, Pierre, Damien, Pierre, Estournel, Claude, Marsaleix, Patrick, Mortier, Laurent, Prieur, Louis, Taillandier, Vincent, Bosse, Anthony, Testor, Pierre, Damien, Pierre, Estournel, Claude, Marsaleix, Patrick, Mortier, Laurent, Prieur, Louis, and Taillandier, Vincent

Abstract

During the winter from 2009 to 2013, the mixed layer reached the seafloor at about 2500 m in the northwestern Mediterranean Sea. Intense fronts around the deep convection area were repeatedly sampled by autonomous gliders. Subduction down to 200–300 m, sometimes deeper, below the mixed layer was regularly observed testifying of important frontal vertical movements. Potential Vorticity dynamics was diagnosed using glider observations and a high resolution realistic model at 1-km resolution. During down-front wind events in winter, remarkable layers of negative PV were observed in the upper 100 m on the dense side of fronts surrounding the deep convection area and successfully reproduced by the numerical model. Under such conditions, symmetric instability can grow and overturn water along isopycnals within typically 1–5 km cross-frontal slanted cells. Two important hotpspots for the destruction of PV along the topographically-steered Northern Current undergoing frequent down-front winds have been identified in the western part of Gulf of Lion and Ligurian Sea. Fronts were there symmetrically unstable for up to 30 days per winter in the model, whereas localized instability events were found in the open sea, mostly influenced by mesoscale variability. The associated vertical circulations also had an important signature on oxygen and fluorescence, highlighting their under important role for the ventilation of intermediate layers, phytoplankton growth and carbon export.

Published
2021
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48. Influence of atmospheric deposition on biogeochemical cycles in an oligotrophic ocean system

Author

Van Wambeke, France, Taillandier, Vincent, Deboeufs, Karine, Pullido-villena, Elvira, Dinasquet, Julie, Engel, Anja, Maranon, Emilio, Ridame, Céline, Guieu, Cécile, Van Wambeke, France, Taillandier, Vincent, Deboeufs, Karine, Pullido-villena, Elvira, Dinasquet, Julie, Engel, Anja, Maranon, Emilio, Ridame, Céline, and Guieu, Cécile

Abstract

The surface mixed layer (ML) in the Mediterranean Sea is a well stratified domain characterized by low macro-nutrient and low chlorophyll content, during almost 6 months of the year. Nutrient dynamics in the ML depend on allochthonous inputs, through atmospheric deposition and on biological recycling. Here we characterize the biogeochemical cycling of N in the ML by combining simultaneous in situ measurements of atmospheric deposition, nutrients, hydrological conditions, primary production, heterotrophic prokaryotic production, N2 fixation and leucine aminopeptidase activity. The measurements were conducted along a 4300 km transect across the central and western open Mediterranean Sea in spring 2017. Dry deposition was measured on a continuous basis while two wet deposition events were sampled, one in the Ionian Sea and one in the Algerian basin. Along the transect, N budgets were computed to compare sources and sinks of N in the mixed layer. On average, phytoplankton N demand was 2.9 fold higher (range 1.5–8.1) than heterotrophic prokaryotic N demand. In situ leucine aminopeptidase activity contributed from 14 to 66 % of heterotrophic prokaryotic N demand, and N2 fixation rate represented 1 to 4.5 % of the phytoplankton N demand. Dry atmospheric deposition of inorganic nitrogen, estimated from dry deposition of (nitrate + ammonium) in aerosols, was higher than N2 fixation rates in the ML (on average 4.8 fold). The dry atmospheric input of inorganic N represented a highly variable proportion of biological N demand in the ML, 10–82 % for heterotrophic prokaryotes and 1–30 % for phytoplankton. Stations visited for several days allowed following the evolution of biogeochemical properties in the ML and within the nutrient depleted layers. At the site in the Algerian Basin and on a basis of high frequency sampling of CTD casts before and after a wet dust deposition event, different scenarios were considered to explain a delayed appearance of peaks in dissolved inorganic

Published
2021
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49. Subsurface iron accumulation and rapid aluminum removal in the Mediterranean following African dust deposition

Author

European Commission, Centre National de la Recherche Scientifique (France), Institut national des sciences de l'Univers (France), Institut Français de Recherche pour l'Exploitation de la Mer, Commissariat à l'Ènergie Atomique et aux Ènergies Alternatives (France), Météo-France, Bressac, Matthieu, Wagener, Thibaut, Leblond, Nathalie, Tovar-Sánchez, Antonio, Ridame, Céline, Taillandier, Vincent, Albani, Samuel, Guasco, Sophie, Dufour, Aurélie, Jacquet, Stéphanie H. M., Dulac, François, Desboeufs, Karine, Guieu, Cécile, European Commission, Centre National de la Recherche Scientifique (France), Institut national des sciences de l'Univers (France), Institut Français de Recherche pour l'Exploitation de la Mer, Commissariat à l'Ènergie Atomique et aux Ènergies Alternatives (France), Météo-France, Bressac, Matthieu, Wagener, Thibaut, Leblond, Nathalie, Tovar-Sánchez, Antonio, Ridame, Céline, Taillandier, Vincent, Albani, Samuel, Guasco, Sophie, Dufour, Aurélie, Jacquet, Stéphanie H. M., Dulac, François, Desboeufs, Karine, and Guieu, Cécile

Abstract

Mineral dust deposition is an important supply mechanism for trace elements in the low-latitude ocean. Our understanding of the controls of such inputs has been mostly built on laboratory and surface ocean studies. The lack of direct observations and the tendency to focus on near-surface waters prevent a comprehensive evaluation of the role of dust in oceanic biogeochemical cycles. In the frame of the PEACETIME project (ProcEss studies at the Air-sEa Interface after dust deposition in the MEditerranean sea), the responses of the aluminum (Al) and iron (Fe) cycles to two dust wet deposition events over the central and western Mediterranean Sea were investigated at a timescale of hours to days using a comprehensive dataset gathering dissolved and suspended particulate concentrations, along with sinking fluxes. Dissolved Al (dAl) removal was dominant over dAl released from dust. The Fe/Al ratio of suspended and sinking particles revealed that biogenic particles, and in particular diatoms, were key in accumulating and exporting Al relative to Fe. By combining these observations with published Al/Si ratios of diatoms, we show that adsorption onto biogenic particles, rather than active uptake, represents the main sink for dAl in Mediterranean waters. In contrast, systematic dissolved Fe (dFe) accumulation occurred in subsurface waters (∼ 100-1000m), while dFe input from dust was only transient in the surface mixed layer. The rapid transfer of dust to depth, the Fe-binding ligand pool in excess to dFe in subsurface (while nearly saturated in surface), and low scavenging rates in this particle-poor depth horizon are all important drivers of this subsurface dFe enrichment. At the annual scale, this previously overlooked mechanism may represent an additional pathway of dFe supply for the surface ocean through diapycnal diffusion and vertical mixing. However, low subsurface dFe concentrations observed at the basin scale (<0.5nmolkg-1) cause us to question the residence time fo

Published
2021

50. Biological production in two contrasted regions of the Mediterranean Sea during the oligotrophic period: An estimate based on the diel cycle of optical properties measured by BGC-Argo profiling floats

Author

Barbieux, Marie, primary, Uitz, Julia, additional, Mignot, Alexandre, additional, Roesler, Collin, additional, Claustre, Hervé, additional, Gentili, Bernard, additional, Taillandier, Vincent, additional, D'Ortenzio, Fabrizio, additional, Loisel, Hubert, additional, Poteau, Antoine, additional, Leymarie, Edouard, additional, Penkerc'h, Christophe, additional, Schmechtig, Catherine, additional, and Bricaud, Annick, additional

Published
2021
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