Matthieu Bressac

CNRS · Laboratoire d'Océanographie de Villefranche

In the Subantarctic sector of the Southern Ocean, vertical entrainment of iron (Fe) triggers the seasonal productivity cycle but diminishing physical supply during the spring to summer transition forces microbial assemblages to rapidly acclimate. Here, we tested how phytoplankton and bacteria within an isolated eddy respond to different dissolved F...

In the Western Tropical South Pacific, a hotspot of dinitrogen-fixing organisms has been identified. The survival of these species depends on the availability of dissolved iron (DFe); however, the source of this DFe is still unclear. DFe was measured along a transect from 175°E to 166°W near 19-21°S. The distribution of DFe showed high spatial vari...

This study reports the only recent characterization of two contrasted wet deposition events collected during the PEACETIME (ProcEss studies at the Air–sEa Interface after dust deposition in the MEditerranean Sea) cruise in the open Mediterranean Sea (Med Sea) and their impact on trace metal (TM) marine stocks. Rain samples were analysed for Al, 12...

N2 fixation rates were measured in the 0–1000 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...

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...

The Subantarctic Southern Ocean is far away from terrestrial iron inputs. Low dissolved iron (DFe) supply strongly limits the growth of phytoplankton in subpolar surface waters. However, phytoplankton benefit from vertical Fe supply from a subsurface reservoir (termed new Fe) which triggers the beginning of the phytoplankton growth season. However,...

This study reports the only recent characterisation of two contrasted wet deposition events collected during the PEACETIME cruise in the Mediterranean open seawater, and their impact on trace metals (TMS) marine stocks. Rain samples were analysed for Al, 12 trace metals (TMs hereafter, including Co, Cd, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Ti, V and Zn) and...

N2 fixation rates were measured in the 0–1000 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 of N2 fixation was not related to Fe, P nor N stocks, the surface composition of the diazotrophic community indicated a strong eastward incr...

Distribution of bioactive, particulate trace metals (pTMs) from shallow hydrothermal vents (SHVs) are still poorly investigated. Exchange processes with the dissolved phase and the subsequent impact on TM marine biogeochemical cycling remain unclear. Here, we document the abundance and distribution of pTMs around SHVs investigated during the TONGA...

Lithogenic elements such as aluminum (Al), iron (Fe), rare earth elements (REEs), thorium (232Th and 230Th, given as Th) and protactinium (Pa) are often assumed to be insoluble. In this study, their dissolution from Saharan dust reaching Mediterranean seawater was studied through tank experiments over 3 to 4 d under controlled conditions including...

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 onto 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 du...

The release of lithogenic elements (which are often assumed to be insoluble) such as Aluminum (Al), Iron (Fe), Rare Earth Elements (REE), Thorium (Th) and Protactinium (Pa) by Saharan dust reaching Mediterranean seawater was studied through tank experiments over 3 to 4 days under controlled conditions including control without dust addition and dus...

The Sea Surface Microlayer (SML) is known to be enriched by trace metals relative to the underlying water and harbor diverse microbial communities (i.e., neuston). However, the processes linking metals and biota in the SML are not yet fully understood. The metal (Cd, Co, Cu, Fe, Ni, Mo, V, Zn and Pb) concentrations in aerosol samples in the SML (di...

Plain Language Summary Microscopic plants and animals in seawater require nutrients to survive. One of these key nutrients is iron, dissolved in seawater at very low concentrations. The growth of around half of the microscopic life in the upper ocean is dependent on the availability of this dissolved iron. These organisms form the bottom of the foo...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Iron (Fe) is a paradox in the modern ocean – it is central to many life-critical enzymes but is scarce across most surface waters. The high cellular demand and low bioavailability of Fe likely puts selective pressure on marine microorganisms. Previous observations suggest that heterotrophic bacteria are outcompeted by small diatoms for Fe supply in...

The dissolved iron supply controls half of the oceans’ primary productivity. Resupply by the remineralization of sinking particles, and subsequent vertical mixing, largely sustains this productivity. However, our understanding of the drivers of dissolved iron resupply, and their influence on its vertical distribution across the oceans, is still lim...

It is well recognized that the atmospheric deposition of iron (Fe) affects ocean productivity, atmospheric CO2 uptake, ecosystem diversity, and overall climate. Despite significant advances in measurement techniques and modeling efforts, discrepancies persist between observations and models that hinder accurate predictions of processes and their gl...

The Sea Surface Microlayer (SML) is known to be enriched in trace metals relative to the underlaying water and to harbor diverse microbial communities (i.e. neuston). However, the processes linking metals and biota in the SML are not yet fully understood. In this study, we analyzed the metal (Cd, Co, Cu, Fe, Ni, Mo, V, Zn and Pb) concentrations in...

The oceans’ biological pump (BP) exports large amounts of particulate organic carbon (POC) to the mesopelagic zone (base of the euphotic zone – 1000 m depth). The efficiency at which POC is transferred through the mesopelagic zone determines the size of the deep ocean carbon store. Few observational BP studies focus on the mesopelagic, often leadin...

The bioavailability of iron (Fe) may limit primary production in half of the global ocean. However, most research has focused on sources of new Fe, and little attention has been directed toward controls on the release of dissolved iron (DFe) during particle remineralization at depth. Within the mesopelagic zone, heterotrophic bacterial activity res...

The evolution of 137Cs, 237Np and 239+240Pu at the DYFAMED station (NW Mediterranean) is discussed in relation to physical processes, downward fluxes of particles, and changes in the main input sources. The data set presented in this study represents the first complete 237Np vertical profiles (0.12–0.27 μBq L−1), and constitutes a baseline measurem...

[ Phil. Trans. R. Soc. A 374 , 20150299 (28 November 2016; Published online 17 October 2016) ([doi:10.1098/rsta.2015.0299][2])][2] In the above article, there were some minor errors in figure 5 and the associated caption. The correct figure and caption are as follows. ![Figure 5.][2]

The evolution of Cs-137, Np-237 and Pu239+240 at the DYFAMED station (NW Mediterranean) is discussed in relation to physical processes, downward fluxes of particles, and changes in the main input sources. The data set presented in this study represents the first complete Np-237 vertical profiles (0.12-0.27 mu Bq L-1), and constitutes a baseline mea...

Geoengineering to mitigate climate change has long been proposed, but remains nebulous. Exploration of the feasibility of geoengineering first requires the development of research governance to move beyond the conceptual towards scientifically designed pilot studies. Fortuitously, 12 mesoscale (approx. 1000 km ² ) iron enrichments, funded to invest...

In this work, we present first 236U results in the northwestern Mediterranean. 236U is studied in a seawater column sampled at DYFAMED (Dynamics of Atmospheric Fluxes in the Mediterranean Sea) station (Ligurian Sea, 43°25′N, 07°52′E). The obtained 236U/238U atom ratios in the dissolved phase, ranging from about 2 × 10− 9 at 100 m depth to about 1.5...

The dynamics of dissolved inorganic nitrogen and phosphorus in seawater after a dust event were followed to better understand the impact of dust deposition in low nutrient waters of the Mediterranean Sea. Three independent abiotic experiments were performed over three seasons (winter, spring, end of summer) characterized by contrasted biogeochemica...

By bringing new nutrients and particles to the surface ocean, atmospheric deposition impacts biogeochemical cycles. The extent to which those changes are modifying the carbon balance in oligotrophic environments such as the Mediterranean Sea that receives important Saharan dust fluxes is unknown. The DUNE (DUst experiment in a low Nutrient, low chl...

By bringing new nutrients and particles to the surface ocean, atmospheric deposition impacts biogeochemical cycles. The extent to which those changes are modifying the carbon balance in oligotrophic environments such as the Mediterranean Sea that receives important Saharan dust fluxes is unknown. DUNE project provides the first attempt to evaluate...

Abstract. Lithogenic particles, such as desert dust, have been postulated to influence particulate organic carbon (POC) export to the deep ocean by acting as mineral ballasts. However, an accurate understanding and quantification of the POC–dust association that occurs within the upper ocean is required in order to refine the “ballast hypothesis”....

[1] Abiotic iron removal processes such as scavenging can significantly and rapidly modify iron distribution in the dissolved-colloidal-particulate continuum. Therefore, these processes could be considered, in addition to ligand complexation, as a major control on atmospheric iron dissolution in seawater. In this work, we investigated the seasonal...

Lithogenic particles, such as desert dust, have been postulated to influence particulate organic carbon (POC) export to the deep ocean by acting as mineral ballasts. However, an accurate understanding and quantification of the POC-dust association that occurs within the upper ocean is required in order to affine the "ballast hypothesis". In the fra...

Biological N2 fixation rates were quantified in the Eastern Tropical South Pacific (ETSP) during both El Niño (February 2010) and La Niña (March–April 2011) conditions, and from Low-Nutrient, Low-Chlorophyll (20°S) to High-Nutrient, Low-Chlorophyll (HNLC) (10°S) conditions. N2 fixation was detected at all stations with rates ranging from 0.01 to 0....

Biological N-2 fixation rates were quantified in the Eastern Tropical South Pacific (ETSP) during both El Nino (February 2010) and La Nina (March-April 2011) conditions, and from Low-Nutrient, Low-Chlorophyll (20 degrees S) to High-Nutrient, Low-Chlorophyll (HNLC) (10 degrees S) conditions. N-2 fixation was detected at all stations with rates rangi...

The deposition of atmospheric dust is the primary process supplying trace elements abundant in crustal rocks (e.g. Al, Mn and Fe) to the surface ocean. Upon deposition, the residence time in surface waters for each of these elements differs according to their chemical speciation and biological utilization. Presently however their behavior after atm...

The deposition of atmospheric dust is the primary process supplying trace elements abundant in crustal rocks (e.g. Al, Mn and Fe) to the surface ocean. Upon deposition, the residence time in surface waters for each of these elements differs according to their chemical speciation and biological utilization. Presently however their behavior after atm...

It has recently been postulated that lithogenic particles such as Saharan dust strongly influence particulate organic carbon export to the deep ocean by acting as mineral ballast. However, our understanding of the processes involved remains scant. In the present study, optical measurements were performed to monitor variations in the concentration,...

The behavior and stability of dissolved reduced glutathione (GSH), an environmental antioxidant and metal transporter, is poorly known in natural waters. Glutathione oxidation rates were determined in both fresh- and brackish waters artificially submitted to different radiation wavebands. Photo-oxidation of GSH followed pseudo-first order kinetics,...