Publications récentes

Phosphorus limitation affects the molecular composition of Thalassiosira weissflogii leading to increased biogenic silica dissolution and high degradation rates of cellular carbohydrates

Auteurs : Christos Panagiotopoulos (MIO), Madeleine Goutx (MIO), Maxime Suroy (MIO), Brivaëla Moriceau 

Organic Geochemistry, Elsevier, 2020, 148, pp.104068. ⟨10.1016/j.orggeochem.2020.104068⟩. ⟨hal-02937026⟩

Abstract : Diatoms in general, and Thalassiosira weissflogii (T. weissflogii) in particular, are among the most ubiquitous phytoplanktonic species, while phosphorus (P) is an essential nutrient that limits productivity in many oceanic regimes. To investigate how T. weissflogii cultures grown under different P regimes are chemically altered before and during their prokaryotic degradation, T. weissflogii cells were cultivated under two contrasting P conditions; “P-stress” and “P-replete”. Biodegradation experiments were conducted in natural seawater comprising a natural prokaryotic community. The particulate fraction was monitored for 3 weeks for organic carbon (POC), nitrogen (PON), biogenic silica (bSiO2), total carbohydrates (PCHO) and individual monosaccharides, including prokaryotic counting. Results indicated that P-stress induced changes in the chemical composition of the T. weissflogii cells, causing a decrease in the Si/N (1.1–0.46) and Si/C (0.17–0.08) ratios. The “P-stress T. weissflogii” cells were characterized by high amounts of galactose (23% of PCHO), xylose (21%) and glucose (19%), compared to the “P-replete T. weissflogii” cells. The latter were dominated by ribose (20% of PCHO), further indicating the exhaustion of ribose-rich molecules (e.g., ATP) in T. weissflogii under “P-stress” conditions. The degradation experiments showed that bSiO2 produced under “P-stress” conditions dissolved more rapidly than bSiO2 formed under “P-replete” conditions, whereas POC and PON exhibited higher degradation rate constants in the “P-replete T. weissflogii” than in the “P-stress T. weissflogii” experiment. Overall, these observations show that submission of T. weissflogii to P-limitation results in changes in its initial biochemical composition, increased frustule dissolution rates, and decreases the degradation of T. weissflogii-organic matter by marine prokaryotes.

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Approaches to evaluate spatial and temporal variability of deep marine sediment characteristics under the impact of dense water formation events

Auteurs : DURRIEU de MADRON, X., STABHOLZ, M., HEIMBÜRGER-BOAVIDA, L. (MIO), AUBERT, D., KERHERVÉ, P., & LUDWIG, W. (2020).

Mediterranean Marine Science, 21(3), 527-544. doi:https://doi.org/10.12681/mms.22581

Résumé  : Dense shelf water cascading and open-ocean convection frequently occur in the Gulf of Lions, Northwestern Mediterranean
Sea. These intense dense water formation events are capable of supplying large amounts of particulate matter as well as remobilizing
and dispersing local sediments and are therefore thought to leave an imprint on superficial deposits. Here, we compare the
spatial variability of the superficial sediment composition (grain size, organic parameters, and metals) at different scales (from
decimetric to kilometric) on the continental slope and rise with the temporal variability linked to the occurrence of intense dense
water formation events. The spatial and temporal variability of the geochemical composition of deep sediments was assessed
using multivariate and geostatistical analyses. The results indicate that in the outer reaches of Cap de Creus Canyon, where both
processes interact, no clear relation was found between the temporal variability of the superficial sediment and the deep-water
formation events, and that the small-scale spatial variability of the sediment masks the temporal variability. Measurements across
the southern slope indicate the presence of a somewhat distinct geochemical signature that likely results from the influence of
recurrent intense, dense water formation events as well as unabating bottom trawling activity.

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Refugia area for the ctenophore Mnemiopsis leidyi A. Agassiz 1865 in the Berre Lagoon (southeast France): The key to its persistence

Auteurs : Guillaume Marchessaux (MIO), Vincent Faure, Cristèle Chevalier (MIO) , DelphineThibault (MIO)

Regional Studies in Marine Science - Volume 39, September 2020, 101409

Résumé : The invasive ctenophore, Mnemiopsis leidyi has been proliferating in lagoons and coastal areas around Europe for almost 20 years but the role and the impact of its presence in sink ecosystems is still not completely understood. In France, Mnemiopsis leidyi is present in Mediterranean lagoons and estuaries along La Manche Sea. Mnemiopsis was first recorded in the Berre Lagoon in early 2000. This lagoon has been highly perturbated for years, with a large volume of freshwater inflow through natural rivers and a succession of large hydroelectric power plants, inducing important eutrophication. Legislation has been implemented to improve the health status of the lagoon since 1994. A long-term study was undertaken in 2010 to measure Mnemiopsis population dynamics, and to identify the main drivers of its persistence in this highly anthropogenic lagoon. In 2011 and 2012, during extreme winter conditions, populations of this ctenophore were not observed for months. Its re-appearance later in year could be linked to either a new introduction from the Mediterranean Sea or the existence of retention areas where individuals sought refugia. Following measurement of biochemical conditions (i.e. chlorophyll a), plankton biomass and Mnemiopsis populations structure (eggs, cydippid larvae/transitional phase and adult) in different areas of the lagoon, as well as the lagrangian modelling of “particles” distribution (i.e. Ichthyop), we highlighted the seasonal patterns in the population structure, the level of available carbon always above the minimal for the survival of Mnemiopsis (24 gC L−1) and the potential refugia area role the Vaine sub-basin could play. Populations from the Vaine sub-basin probably serve as source populations for the rest of the lagoon by advective transport in spring.

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Use of organic exudates from two polar diatoms by bacterial isolates from the Arctic Ocean.

Auteurs :  Lucas Tisserand, Laëtitia Dadaglio, Laurent Intertaglia , Philippe Catala, Christos Panagiotopoulos (MIO), Ingrid Obernosterer
and Fabien Joux

Philosophical transactions A. 378: 20190356 -
Published: 31 August 2020https://doi.org/10.1098/rsta.2019.0356

Résumé : Global warming affects primary producers in the Arctic, with potential consequences for the bacterial community composition through the consumption of microalgae-derived dissolved organic matter (DOM). To determine the degree of specificity in the use of an exudate by bacterial taxa, we used simple microalgae–bacteria model systems. We isolated 92 bacterial strains from the sea ice bottom and the water column in spring–summer in the Baffin Bay (Arctic Ocean). The isolates were grouped into 42 species belonging to Proteobacteria, Bacteroidetes, Actinobacteria and Firmicutes. Forty strains were tested for their capacity to grow on the exudate from two Arctic diatoms. Most of the strains tested (78%) were able to grow on the exudate from the pelagic diatom Chaetoceros neogracilis, and 33% were able to use the exudate from the sea ice diatom Fragilariopsis cylindrus. 17.5% of the strains were not able to grow with any exudate, while 27.5% of the strains were able to use both types of exudates. All strains belonging to Flavobacteriia (n = 10) were able to use the DOM provided by C. neogracilis, and this exudate sustained a growth capacity of up to 100 times higher than diluted Marine Broth medium, of two Pseudomonas sp. strains and one Sulfitobacter strain. The variable bioavailability of exudates to bacterial strains highlights the potential role of microalgae in shaping the bacterial community composition.

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Bridging the spatiotemporal gap in diazotroph activity and diversity with high-resolution measurements

Auteurs : Mar Benavides (MIO), Julie Robidart

Front. Mar. Sci. | doi: 10.3389/fmars.2020.568876

Résumé : The biological fixation of dinitrogen (N2) by marine microbes called ‘diazotrophs’ sustains ~50% of primary production in the ocean, boosting CO2 absorption by photoautotrophs and thus contributing to the mitigation of climate change. At present, the paucity and biased geographical coverage of N2 fixation and diazotroph diversity measurements impedes constraining nitrogen inputs to the ocean. Most studies have been conducted at very distant spatiotemporal scales, including: i) discrete and short duration measurements in small seawater volumes isolated from the environment, and ii) spatial extrapolations and global models of diazotrophy projected over decades to centuries. This knowledge gap lies at the fine scales: dynamic seawater structures <200 km wide and <2 months lifetime. However, the spatiotemporal resolution of conventional oceanographic cruises, with stations separated by tens to hundreds of kilometers, is too poor to resolve fine scale processes. Bridging this gap requires implementing high spatiotemporal resolution measurements. Here we present and discuss the advantages and disadvantages of contemporary methods and equipment able to provide high-resolution measurements at sea. We also provide insights into high-resolution sampling approaches to be developed in the near future. Increasing the spatiotemporal resolution of diazotroph activity and diversity will provide more realistic quantifications of nitrogen fluxes in the dynamic ocean.

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Characterization of the submarine disposal of a Bayer effluent (Gardanne alumina plant, southern France) : I. Size distribution, chemical composition and settling rate of particles forming at the outfall

 

Auteurs : Stéphanie Jacquet (MIO), Christophe Monnin, Olivier Herlory, Deborah Mille, Aurélie Dufour (MIO), Benjamin Oursel (MIO), Lars-Eric Heimbürger-Boavida (MIO), Sébastien D’onofrio (MIO), Nicolas Layglon (MIO), Cédric Garnier (MIO)

Chemosphere
Volume 263, January 2021, 127695

Résumé : The submarine discharge of the high pH clarified Bayer effluent of the Gardanne alumina plant (Marseille region, France) leads to the formation of concretions at the outfall 324 m underwater and to a plume of white particles. The bulk chemical composition of the concretions has been determined by SF-ICP-MS. Mg and Al are the major elements measured with concentrations of a few hundred mg g−1. Ca and S are also found at concentrations in the range of mg g−1. Among the measured trace elements there is a specific interest in As and V because of environmental concerns pointed out by regulation authorities. Their concentrations are of tens to thousands μg g−1, respectively. Concentrations of the other elements are in the range of a few ng g−1 to few hundreds μg g−1. In order to constrain the dispersion of particles in the environment and to understand how chemical elements can be scavenged from or released to seawater, the size distribution of particles composing the concretions has been measured by settling rate experiments and, for each size class of particles, their chemical composition has been determined. For example, As and V are mainly associated to particles with mean diameters between 15.6 and 63 μm and settling rates around 96 m d−1. Overall, all the main elements (Mg, Al, Ca, S) composing concretions are associated to this size class of particles which represents 53–60% of the total concretion mass.

Mots clés : Bayer effluent, Hydrotalcite, Trace metals, Settling rate, Size distribution, Gardanne alumina plant, Mediterranean sea

 

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Refugia area for the ctenophore Mnemiopsis leidyi A. Agassiz 1865 in the Berre Lagoon (southeast France) : The key to its persistence

 

Auteurs : Guillaume Marchessaux (MIO), Vincent Faure, Cristèle Chevalier (MIO), DelphineThibault (MIO)

Regional Studies in Marine Science
Volume 39, September 2020, 101409

Résumé : The invasive ctenophore, Mnemiopsis leidyi has been proliferating in lagoons and coastal areas around Europe for almost 20 years but the role and the impact of its presence in sink ecosystems is still not completely understood. In France, Mnemiopsis leidyi is present in Mediterranean lagoons and estuaries along La Manche Sea. Mnemiopsis was first recorded in the Berre Lagoon in early 2000. This lagoon has been highly perturbated for years, with a large volume of freshwater inflow through natural rivers and a succession of large hydroelectric power plants, inducing important eutrophication. Legislation has been implemented to improve the health status of the lagoon since 1994. A long-term study was undertaken in 2010 to measure Mnemiopsis population dynamics, and to identify the main drivers of its persistence in this highly anthropogenic lagoon. In 2011 and 2012, during extreme winter conditions, populations of this ctenophore were not observed for months. Its re-appearance later in year could be linked to either a new introduction from the Mediterranean Sea or the existence of retention areas where individuals sought refugia. Following measurement of biochemical conditions (i.e. chlorophyll a), plankton biomass and Mnemiopsis populations structure (eggs, cydippid larvae/transitional phase and adult) in different areas of the lagoon, as well as the lagrangian modelling of “particles” distribution (i.e. Ichthyop), we highlighted the seasonal patterns in the population structure, the level of available carbon always above the minimal for the survival of Mnemiopsis (24 gC L−1) and the potential refugia area role the Vaine sub-basin could play. Populations from the Vaine sub-basin probably serve as source populations for the rest of the lagoon by advective transport in spring.

 

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The Management of Mediterranean Coastal Habitats: A Plea for a Socio-ecosystem-Based Approach

Auteurs : Charles François Boudouresque (MIO),  Patrick Astruch, Daniela Bănaru (MIO),  Jean Blanchot (MIO), Aurélie Blanfuné (MIO), François Carlotti(MIO),  Thomas Changeux( MIO) , Daniel Faget, Adrien Goujard, Mireille Harmelin-Vivien (MIO), Laurence Le Diréach, Marc Pagano (MIO) , Michèle Perret-Boudouresque, Vanina Pasqualini, Elodie Rouanet, Sandrine Ruitton (MIO) , Richard Sempéré (MIO) , Delphine Thibault(MIO) , Thierry Thibaut  (MIO)

Evolution of Marine Coastal Ecosystems under the Pressure of Global Changes. Springer, Cham

Résumé : Biodiversity is often defined erroneously as the number of species. The higher the number of species, the better the status or the health of a habitat is considered to be. Managers, stakeholders and environmentalists worldwide often prioritize the ‘species approach’. The protection of an iconic and endearing species is obviously easier than that of tiny zooplankton species, although the latter may play a far more important role than the former in the functioning of healthy ecosystems. The species approach has been widely favoured compared to the ecosystem approach. However, ‘species-by-species’ management is unrealistic. The problem is that the management of natural habitats is often driven by environmentalist lobbies on the basis of taxonomy (e.g. mammals, turtles, birds, iconic fish, flowering plants, etc.) and disciplinary lobbies (biology, benthos, pelagos, contaminants, currents, etc.). Ecosystems are units of biological and spatial organization that include all the organisms, their interactions, the functional compartments they belong to, along with the components of the abiotic environment. The concept of the socio-ecosystem is useful insofar as it emphasizes the fact that man is part of ecosystems. Here, the authors make use of four case studies, in the Mediterranean Sea, in an attempt to demonstrate the interest of a comprehensive, socio-ecosystem-based approach in the field of environmental management. They also highlight the importance of tackling the coupling between benthic and pelagic ecosystems and between terrestrial and marine ecosystems.

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High N2 fixation in and near the Gulf Stream consistent with a circulation control on diazotrophy

Auteurs : Jaime B. Palter, Elana Ames, Mar Benavides (MIO), Afonso Goncalves Neto, Julie Granger, Pia H. Moisander, Katie S. Watkins‐Brandt,
Angelicque E. White

Geophysical Research Letter -
First published: 19 July 2020
https://doi.org/10.1029/2020GL089103

Résumé :  The stoichiometry of physical nutrient supply may provide a constraint on the spatial distribution and rate of marine nitrogen (N2) fixation. Yet agreement between the N2 fixation rates inferred from nutrient supply and those directly measured has been lacking. The relative transport of phosphate and nitrate across the Gulf Stream suggests that 3‐6 Tg N year‐1 must be fixed to maintain steady nutrient stoichiometry in the North Atlantic subtropical gyre. Here, we show direct measurements of N2 fixation consistent with these estimates, suggesting elevated N2 fixation in and near the Gulf Stream. At some locations across the Gulf Stream, we measured diazotroph abundances and N2 fixation rates that are 1‐3 orders of magnitude greater than previously measured in the central North Atlantic subtropical gyre. In combination, rate measurements and gene abundances suggest that biogeochemical budgets can be a robust predictive tool for N2 fixation hot spots in the global ocean.

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Mercury species export from the Arctic to the Atlantic Ocean

Auteurs : Petrova, M. V;(MIO) ; Krisch, S.; Lodeiro, P.; Valk, O.; Dufour, A. (MIO) ; Rijkenberg, M. J. A.; Achterberg, E. P.; Rabe, B.; Van der Loeff, M. R.; Hamelin, B.; Sonke, J.E., Garnier, C. (MIO); Heimbürger-Boavida, L.E. (MIO)

Marine Chemistry - Available online 18 July 2020, 103855

Résumé : The Fram Strait is the only deep connection between the Arctic and Atlantic Oceans. The main water and mercury (Hg) fluxes between these oceans occur via the Fram Strait and Barents Sea Opening. Several Hg mass balance studies indicated a net Hg export from the Arctic to the Atlantic Ocean. However, in the absence of Hg measurements in the Fram Strait and Barents Sea Opening, these estimates were based on North Atlantic and central Arctic Ocean data alone. Here, we refine the Arctic total Hg (tHg) and methylated Hg (MeHg) mass budgets using new data acquired during the 2015 GEOTRACES (section GN04) TransArcII cruise in the Barents Sea Opening and the 2016 GEOTRACES (section GN05) GRIFF cruise, which covered the Fram Strait and Northeast Greenland Shelf. Total Hg increased westward along the Fram Strait transect, reaching the highest concentrations on the Northeast Greenland Shelf. Concentrations of tHg averaged 1.29 ± 0.43 pM in the East Greenland Current, while core waters of the West Spitsbergen Current had average values of 0.80 ± 0.26 pM. Using our new data, we estimate that 43 ± 9 Mg y−1 of tHg is transported to the Arctic Ocean in the core of the West Spitsbergen Current, while 54 ± 13 Mg y−1 of tHg is exported from the Arctic Ocean in the East Greenland Current and Recirculated Atlantic Water. This results in a net tHg export of 11 ± 8 Mg y−1 via the Fram Strait. We find a shallow MeHg maximum (at 150 m depth) in the East Greenland Current, in agreement to what was reported for the central Arctic Ocean and Canadian Arctic Archipelago. The West Spitsbergen Current is characterized by lower MeHg concentrations and a deeper MeHg maximum, that is located at approximately 1000 m depth. We estimate a net MeHg export of 6 ± 2 Mg y−1 from the Arctic Ocean via the Fram Strait, which is nearly half of the exported tHg. Most of the exported MeHg is in the form of DMHg (2:1 ratio of dimethylmercury to monomethylmercury). Previous studies reported lower MeHg proportions. Our observations show that the Arctic Ocean is producing and exporting MeHg to the Atlantic Ocean. In total, the Arctic Ocean exports about 18 Mg y−1 of tHg to the Nordic Seas and North Atlantic via the Fram Strait and Davis Strait, of which 7.5 Mg y−1 is in the MeHg form.

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Mercury Export Flux in the Arctic Ocean Estimated from 234Th/238U Disequilibria

Auteurs : Javier A. Tesán Onrubia (MIO), Mariia V. Petrova (MIO), Viena Puigcorbé, Erin E. Black, Ole Valk, Aurélie Dufour (MIO), Bruno Hamelin, Ken O. Buesseler, Pere Masqué, Frédéric A. C. Le Moigne (MIO), Jeroen E. Sonke, Michiel Rutgers van der Loeff, Lars-Eric Heimbürger-Boavida (MIO)

ACS Earth Space Chem. 2020,
Publication Date:April 23, 2020
https://doi.org/10.1021/acsearthspacechem.0c00055

Abstract

[Abstract Image]
High mercury (Hg) levels have been observed for arctic biota, despite limited local sources of anthropogenic Hg in the Arctic. Scavenging of Hg exerts an important control on the residence time of Hg in surface waters. The downward Hg export flux and Hg burial rates in bottom sediments are not well-constrained as a result of the lack of particulate Hg (Hgp) observations in the Arctic Ocean. Here, we estimated downward Hg export flux based on Hg concentrations in suspended particulate matter (SPM) and using the radionuclide pair 234Th/238U, coupled to Hgp/234Th ratios in particles. Using new observations made during the German GEOTRACES TransArcII (GN04) and the U.S. Arctic GEOTRACES (GN01) cruises in August–October 2015, we estimated the Hgp export flux in the central Arctic Ocean and the outer shelf. We find that 81 ± 58 Mg year–1 Hgp is exported from the upper 100 m, of which 16 ± 10 Mg year–1 is ultimately buried in marine sediments. An extrapolation to the entire Arctic Ocean, including the inner shelf, results in 156 Mg year–1Hgp export from the surface ocean and 28 Mg year–1 Hg burial rate. Our study shows that the Hgp export flux could be higher than previously thought, and this should be taken into consideration for future arctic Hg budget estimations

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Implementation and assessment of a carbonate system model (Eco3M-CarbOxv1.1) in a highly-dynamic Mediterranean coastal site (Bay of Marseille, France)

Auteurs :  Katixa Lajaunie-Salla (MIO), Frédéric Diaz (MIO), Cathy Wimart-Rousseau (MIO), Thibaut Wagener (MIO)  , Dominique Lefèvre (MIO) , Christophe Yohia, Irène Remy-Xueref, Brian Nathan, Alexandre Armengaud , Christel Pinazo (MIO)

Geoscientific Model Description Discussions Received: 16 Feb 2020 – Accepted for review: 11 May 2020 – Discussion started: 18 May 2020

Résumé : The Bay of Marseille (BoM, France) is impacted by the urbanized and industrialized Aix-Marseille Metropolis, which is subject to significant increases in anthropogenic emissions of CO2. A carbonate chemistry balance module has been implemented into a biogeochemical model of the planktonic food web. The resulting model, named Eco3M-CarbOx includes 22 states variables that are dispatched into 5 compartments: phytoplankton, heterotrophic bacteria, detritus, dissolved organic and inorganic matter. The model suggests that the variability of the dissolved inorganic carbon system is mainly driven by the seawater temperature dynamics. A seasonal trend is identified by the model and it shows that, during the mixed water column period, the BoM is a sink for atmospheric CO2 and a net autotroph ecosystem, while during stratified water column period, the BoM is a source of CO2 to the atmosphere and a net heterotroph ecosystem. External forcings have an important impact on the carbonate equilibrium. Wind events change seawater temperature quickly, as during upwelling, for which the BoM waters change within a few days from a source of CO2 to the atmosphere to a sink into the ocean. Moreover, the higher the wind speed is, the higher the air-sea CO2 gas exchange fluxes are. The river intrusions with nitrate and alkalinity supplies lead to a decrease in the pCO2 value, favoring the conditions of a sink of atmospheric CO2 into the BoM. The nearby highly urbanized environment of the Aix-Marseille metropolis produces strong atmospheric values of CO2, also favoring the conditions of a sink of atmospheric CO2 into the waters of the BoM.

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Temporal variability of the carbonate system and air-sea CO2 exchanges in a Mediterranean human-impacted coastal site

Auteurs : Cathy Wimart-Rousseau (MIO) , Katixa Lajaunie-Salla (MIO), Pierre Marrec , Thibaut Wagener,
Patrick Raimbault (MIO), Veronique Lagadec (MIO), Michel Lafont  (MIO), Nicole Garcia (MIO), Frederic Diaz (MIO), Christel Pinazo (MIO), Christophe Yohia, Fabrice Garcia (MIO)  , Irene Xueref-Remy , Pierre-Eric BlancAlexandre Armengaud, Dominique Lefevre (MIO)

Estuarine, Coastal and Shelf Science - volume 236, 5 May 2020, 106641

Résumé : The temporal evolution of the carbonate system and air-sea CO2 fluxes are investigated for the first time in the Bay of Marseille (BoM – North Western Mediterranean Sea), a coastal system affected by anthropogenic forcing from the Marseille metropolis. This study presents a two-year time-series (between 2016 and 2018) of fortnightly measurements of AT, CT, pH and derived seawater carbonate parameters at the SOLEMIO station. On this land-ocean boundary area, no linear relationship between AT and salinity in surface water is observed due to sporadic intrusions of freshwater coming from the Rhone River. On an annual scale, the BoM acts as a sink of atmospheric CO2. This result is consistent with previous studies in the Mediterranean Sea. Mean daily air-sea CO2 fluxes range between −0.8 mmolC.m−2.d−1 and -2.2 mmolC.m−2.d−1 during the study period, depending on the atmospheric CO2 sampling site used for the estimates. This study shows that the pCO2 in the surface water is predominantly driven by temperature changes, even if partially counterbalanced by biological activity. Therefore, temperature is the main contributor to the air-sea CO2 exchange variability. Mean daily Net Ecosystem Production (NEP) estimates from CT budget shows an ecosystem in which autotrophic processes are associated with a sink of CO2. Despite some negative NEP values, the observed air-sea CO2 fluxes in the BoM are negative, suggesting that thermodynamic processes are the predominant drivers for these fluxes.

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Optical proxy for particulate organic nitrogen from BGC-Argo floats

Auteurs : Alain Fumenia (MIO), Anne Petrenko (MIO) , Hubert Loisel, Kahina Djaoudi, Alain deVerneil, and Thierry Moutin (MIO)

Opt. Express 28, 21391-21406 (2020)

Résumé : Using biogeochemical-Argo float measurements, we propose, for the first time, an optical proxy for particulate organic nitrogen concentration (PON) in the Western Tropical South Pacific, an area influenced by dinitrogen (N2) fixation. Our results show a significant relationship between the backscattering coefficient at 700 nm (bbp) and PON, especially when the latter is measured using the wet oxidation method (R2=0.87). bbp may be used to estimate PON concentrations (PONopt) between 0.02 and 0.95 µM, allowing for unprecedented monitoring using autonomous profiling floats. The bbp vs PON relationship can be used to study phytoplanktonic biomass dynamics at relevant seasonal temporal scales, with clear evidence of PONopt as a proxy of phytoplanktonic biomass, at least for this specific area. Temporal analyses of PONopt show significant increases (from 0.16 to 0.80 µM) likely related to new production associated to N2 fixation events measured during stratification periods in the Melanesian Archipelago.

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Temporal variability of dissolved trace metals at the DYFAMED time-series station, Northwestern Mediterranean

Auteurs : Christophe Migon, Lars-Eric Heimbürger-Boavida (MIO), Aurélie Dufour (MIO), Jean-François Chiffoleau, Daniel Cossa

Marine Chemistry, Volume 225, 10 September 2020, 103846

Résumé : We present here results of an 18-month survey (July 2007–March 2009) of a suite of selected trace metals (TM: Co, Ni, Cu, Pb) in a 2350 m-deep offshore water column in the Ligurian Sea (Northwestern Mediterranean Sea). This low-nutrient low-chlorophyll region is characterised by a long stratification period (May–November) during which surface waters are depleted of macronutrients. Trace metals exhibit a range of biogeochemical behaviours from surface-enriched (scavenged-type) to surface-depleted (nutrient-like) with Co and Ni as representative cases. Cobalt (28–172 pM) distributions are governed by external inputs of aeolian dust deposition and removal by adsorption onto particles in surface, intermediate and deep waters as well. Nickel (3.57–5.52 nM) distributions are governed by internal biogeochemical cycles, together with physical mixing and circulation patterns. Nickel is primarily removed from surface waters with biogenic particles and then remineralised at depth. Copper (1.39–2.89 nM) distributions illustrate a mixture of the two typical behaviours mentioned above. Distributions of typically anthropogenic and particle-reactive Pb (82–235 pM) are in agreement with a Mediterranean flow source of Pb for the adjacent North Atlantic Ocean. The mechanisms controlling the biogeochemical cycling of TMs, such as atmospheric inputs, physical forcing, and interactions with primary production, are discussed according to the TM physico-chemical properties and biological importance.

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Impacts of Marine and Lagoon Aquaculture on Macrophytes in Mediterranean Benthic Ecosystems

Auteurs : Boudouresque Charles-François (MIO), Blanfuné Aurélie(MIO) , Pergent Gérard, Pergent-Martini Christine, Perret-Boudouresque Michéle
(MIO), Thibaut Thierry (MIO)

Frontiers in Marine Science, 17 April 2020 | https://doi.org/10.3389/fmars.2020.00218

Résumé : The direct and indirect impact of fish farms, shellfish aquaculture, and extensive forms of aquaculture such as seeding of juvenile sea urchins, on macrophytes (seaweeds and seagrasses), is reviewed in Mediterranean benthic ecosystems. Fish farms constitute a source of organic matter and nutrients (food and fecal pellets) that causes the extirpation of Posidonia oceanica seagrass meadows beneath and near to farm facilities. In addition to direct effects, the nitrogen enrichment of macrophytes tissues increases the grazing pressure by herbivorous fishes and sea urchins. In some cases, the impact can continue to increase several years after the cessation of farming activities. Natural restoration of extirpated seagrass meadows is generally unlikely at the human time scale. Shellfish aquaculture is the cause of the main flow of introduced macrophytes in the Mediterranean; the main vector is the importation of oyster spat from Japan and Korea. North-eastern Pacific seaweeds are now the dominant biotic component of some Mediterranean lagoons (e.g., Thau, Mar Piccolo, and Venice lagoons). In addition to direct effects, mussel aquaculture can constitute a source of larvae that flow with currents, the adults of which can overwhelm seaweed forests (e.g., Carpodesmia mediterranea). Shellfish aquaculture is also a source of fecal pellets, resulting in changes in bottom macrophytes, and a vector of diseases of metazoans, the extirpation of which may change the functioning of recipient macrophyte ecosystems. The edible sea urchin Paracentrotus lividus is sometimes erroneously considered as in decline due to over-harvesting. However, its abundance in the second half of the 20th century was probably a consequence of human impact (overfishing of its predatory fish, organic pollution. This man-induced proliferation resulted in the extirpation of seaweed forests (e.g., Carpodesmia spp., Treptacantha spp. – formerly Cystoseira spp. – Sargassum spp.; many species are endemic), which play a key role in Mediterranean coastal ecosystems. Therefore, the attempts to restore sea urchin abundance, via seeding of juveniles from hatcheries, has further artificialized the habitats rather than contributing to the restoration of natural ecosystems. Good practices guidelines are proposed aimed at minimizing the impact of aquaculture on macrophytes.

 

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. Human mercury exposure levels and fish consumption at the French Riviera

Auteurs : Tous MIO - Petrova, M. V., Ourgaud, M., Boavida, J. R. H., Dufour, A., Tesán Onrubia, J. A., Lozingot, A. & Heimbürger-Boavida, L.E.

 Chemosphere 127232 (2020). doi:10.1016/j.chemosphere.2020.127232 https://www.sciencedirect.com/science/article/pii/S0045653520314259

Résumé : Humans are exposed to methylmercury (MeHg), a bioaccumulative neurotoxin, mainly through the consumption of marine fish. Several studies showed that high MeHg exposure can lead to neurological damage. This is particularly relevant for pregnant women, because MeHg exposure negatively impacts foetal development. Populations living near the sea are generally at increased exposure risk due to higher consumption of fish and seafood. Here, we present the first study of MeHg exposure levels of the population living at the French Riviera, using mercury (Hg) concentrations in hair as a proxy for MeHg exposure. We found that older people that consume more fish presented the highest hair Hg concentrations. Compared to other Mediterranean bordering countries and other European countries, the southern France population is among those with high MeHg exposure (median for women of childbearing age is 0.56 μg g−1). A global implementation of the Minamata Convention is necessary to lower MeHg exposure of the population.

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Primary production and depth drive different trophic structure and functioning of fish assemblages in French marine ecosystems

Auteurs : PierreCresson , TiphaineChouvelon, Paco Bustamante, Daniela Bănaru (MIO), Jérome Baudrier, François Le Loc'h, Aourell Mauffret, Benoit Mialet, Jérome Spitz, Nathalie Wessel, Marine J.Briand, Margaux Denamiel, Matthieu Doray, Gaël Guillou, Angélique Jadaud, Coline Lazard, Solène Prieur, Manuel Rouquette…Claire Saraux, Sandrine Serre, Charles-André Timmerman, Yves VerinMireille Harmelin-Vivien (MIO)

Progress in Oceanography

Volume 186, July 2020, 102343

Résumé : Investigating the drivers of fish assemblage trophic structure is a critical question, in order to better understand ecosystem functioning, predict the effects of perturbations and implement integrated management of exploited marine ecosystems. Ecosystemic surveys enabled the determination of the trophic structure of the fish assemblages in three French marine ecosystems, namely the Eastern English Channel, the Bay of Biscay and the Gulf of Lions, through the simultaneous collection of qualitative (stable isotopes and energy content) and quantitative (biomass) data. In the Bay of Biscay and in the Gulf of Lions, pelagic primary production supported at least 80% of the fish biomass production, and explained the dominance of pelagic species, but with differences resulting from the different productivity. The lower productivity in the oligotrophic Gulf of Lions led to a lower total biomass, energy density as well as the predominance of zooplankton-feeders. In contrast, fluxes in the Bay of Biscay were sufficient to support a higher biomass of pelagic piscivores, and of species with higher energy content. In the shallow Eastern English Channel, the respective contributions of pelagic and benthic sources were similar. Bentho-demersal species of higher trophic level dominated this assemblage, because of their ability to exploit both pathways. Results of the present study confirmed that fisheries-focused surveys can be used as efficient platforms to address questions about ecosystem functioning. Here, it confirmed the expected differences between ecosystems and the importance of primary production and environment as drivers of fish assemblage structure and functioning. Future studies should nevertheless develop new methods to better assess the paramount role of low trophic level consumers.

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Effects of upwelling duration and phytoplankton growth regime on dissolved-oxygen levels in an idealized Iberian Peninsula upwelling system

Auteurs : Bettencourt, J. H., Rossi, V. (MIO), Renault, L., Haynes, P., Morel, Y., and Garçon, V.

Nonlin. Processes Geophys., 27, 277–294, https://doi.org/10.5194/npg-27-277-2020

Résumé : We apply a coupled modelling system composed of a state-of-the-art hydrodynamical model and a low-complexity biogeochemical model to an idealized Iberian Peninsula upwelling system to identify the main drivers of dissolved-oxygen variability and to study its response to changes in the duration of the upwelling season and in the phytoplankton growth regime. We find that the export of oxygenated waters by upwelling front turbulence is a major sink for nearshore dissolved oxygen. In our simulations of summer upwelling, when the phytoplankton population is generally dominated by diatoms whose growth is boosted by nutrient input, net primary production and air–sea exchange compensate dissolved-oxygen depletion by offshore export over the shelf. A shorter upwelling duration causes a relaxation of upwelling winds and a decrease in offshore export, resulting in a slight increase of net dissolved-oxygen enrichment in the coastal region as compared to longer upwelling durations. When phytoplankton is dominated by groups less sensitive to nutrient inputs, growth rates decrease, and the coastal region becomes net heterotrophic. Together with the physical sink, this lowers the net oxygenation rate of coastal waters, which remains positive only because of air–sea exchange. These findings help in disentangling the physical and biogeochemical controls of dissolved oxygen in upwelling systems and, together with projections of increased duration of upwelling seasons and phytoplankton community changes, suggest that the Iberian coastal upwelling region may become more vulnerable to hypoxia and deoxygenation.

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Impact of cigarette butts on microbial diversity and dissolved trace metals in coastal marine sediment.

Auteurs : Quéméneur, M. (MIO), Chifflet, S. (MIO), Akrout, F., Bellaaj-Zouari, A., Belhassen, M.

Estuarine, Coastal and Shelf Science, 240: 106785. doi: 10.1016/j.ecss.2020.106785

Résumé :

Abstract

Cigarette butts are the most common plastic form of litter found in the marine coast, threatening the quality of the seawater and marine life. However, the impact of cigarette butts known to contain toxic chemicals has been investigated to date in very few marine species. This study aimed to evaluate the effects of cigarette filters (smoked or unsmoked) on the microbial diversity inhabiting coastal sediments by high-throughput sequencing of the 16S rRNA genes. Both bacterial structure and metals distribution were impacted by cigarette filter addition in laboratory sediment experiments, compared to control sediment incubations without filter. Both smoked and unsmoked cigarette filters decreased pH and dissolved Cd, Mo and V concentrations in marine sediment incubations, while they increased dissolved Fe, Mn, Zn levels in the surrounding environment. Smoked filters dramatically decreased the relative abundance of the phyla Bacteroidetes and Cyanobacteria, while the members of the phyla Gammaproteobacteria, Firmicutes and Thermotogae were enriched by smoked filters in marine sediments. Bacterial taxa associated with deep marine environments or hydrothermal seep fields were selected by smoked cigarette filters. This study demonstrated for the first time the microbial community changes and impacts from toxic cigarette filters in coastal marine sediments.

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Why do mesophotic coral ecosystems have to be protected?

Auteurs : Marcelo de Oliveira Soares, Jorge Thé de Araújo, Sarah Maria Cavalcante Ferreira, Bráulio Almeida Santos, Joana Ruela Heimbürger Boavida (MIO) , Federica Costantini, Sergio Rossi

Science of The Total Environment - Volume 726, 15 July 2020, 138456

Abstract

Mesophotic coral ecosystems (MCEs; ~30–150 m depth) are among the most biologically diverse and least protected ecosystems in the world's oceans. However, discussions regarding the conservation of these unique ecosystems are scarce. To address this issue, we identified the features of MCEs that demonstrate they should be considered as a global conservation priority. Some MCEs are characterized by their well-preserved and unique seascapes; their narrow environmental tolerance and high vulnerability to anthropogenic effects; and their slow recovery and reduced reproductive performance. The unique biodiversity of MCEs includes depth-adapted specialist species and new species, most of which are threatened or important fishery resources. MCEs also provide refuge against human stressors, valuable ecosystem services, and ecological connectivity. MCEs generally meet the criteria to be classified as Ecologically and Biologically Significant Marine Areas under the Convention on Biological Diversity. However, we highlight that many MCEs worldwide are threatened and not yet adequately protected by fishery regulations, marine protected areas, or considered in marine spatial planning. Establishing MCEs as a global conservation priority requires the designation of national, international, transnational, public, and private policies.

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Genetic insights into recolonization processes of Mediterranean octocorals

Auteurs : D. Aurelle (MIO) , J. Tariel, F. Zuberer, A. Haguenauer, C. Ribout, M. Masmoudi, H. Kara, L. Chaoui, J. Garrabou, J.-B. Ledoux & M. C. Gambi

Marine Biology volume 167, Article number: 73 (2020)

Abstract

Marine ecosystems are strongly impacted by the consequences of human activities, such as habitat destruction or artificialization and climate change. In the Mediterranean Sea, sessile benthic species, and particularly octocorals, have been affected by mass mortality events linked with positive thermal anomalies. The future survival of octocoral populations impacted by global change will depend on their recolonization abilities facing local extirpation or important modification of their habitat. We studied these processes in Mediterranean octocorals in two situations: the colonization of artificial substrates (wrecks) by the red gorgonian Paramuricea clavata, and the recolonization following mortality events in the yellow gorgonian Eunicella cavolini. With microsatellite markers (seven for P. clavata, five for E. cavolini), we analyzed the genetic diversity of populations on artificial substrates and their differentiation from other neighboring populations. For P. clavata the populations on artificial substrates were not or lowly differentiated from the closest populations (1.3–1.6 km) on natural substrates, and showed similar levels of genetic diversity. Artificial substrates can then be considered as an interesting substitute for natural substrates for this species. For E. cavolini we did not detect any variation in diversity or relatedness following recuperation after mortality events. In both cases, our results suggest the input from different populations in the recolonization process, which helps in maintaining the genetic diversity. These results are useful for the management of these species and of associated ecosystems.

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Sighting of Saccorhiza polyschides (Lightfoot) Batters (Phaeophyceae, Stramenopiles) in Algeria (Mediterranean Sea): an insight into range expansion route

 

Auteurs : Boudouresque C.-F. (MIO), Semroud R., Blanfuné A.  (MIO) & Perret-Boudouresque M. (MIO).

Cryptogamie, Algologie 41 (5): 31-36. https://doi.org/10.5252/cryptogamie-algologie2020v41a5. http://cryp-togamie.com/algologie/41/5

Résumé : Observation de Saccorhiza polyschides (Lightfoot) Batters (Phaeophycées, Straménopiles) en Algérie (mer Méditerranée) : une illustration des voies d’expansion de l’aire de distribution.En Méditerranée, la macroalgue du nord-est de l’Atlantique Saccorhiza polyschides(Lightfoot) Batters n’est pas commune. Les seules populations permanentes sont celles de la mer d’Alboran, près du détroit de Gibraltar et du détroit de Messine (Italie). Depuis le début du xixe siècle, plusieurs observations, sur des coques de bateaux ou dans des ports, traduisent la dispersion de propagules en Méditerranée ; l’espèce n’y a pas dépassé le stade d’adventice. L’observation de Saccorhiza polyschides près du port de Jijel (Algérie), la première nouvelle observation en Méditerranée depuis plus d’un siècle, montre que la dispersion de propagules en Méditerranée se poursuit de nos jours. De plus, grâce à sa taille et à la facilité de son observation, elle contribue à illustrer les voies d’expansion d’une espèce à la limite de son aire actuelle de distribution.

 

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Impacts of Marine and Lagoon Aquaculture on Macrophytes in Mediterranean Benthic Ecosystems

 

Auteurs :  Charles-François Boudouresque (MIO), Aurélie Blanfuné (MIO), Gérard Pergent, Christine Pergent-Martini, Michèle Perret-Boudouresque (MIO) and Thierry Thibaut(MIO)

Front. Mar. Sci., 17 April 2020 | https://doi.org/10.3389/fmars.2020.00218

Résumé : The direct and indirect impact of fish farms, shellfish aquaculture, and extensive forms of aquaculture such as seeding of juvenile sea urchins, on macrophytes (seaweeds and seagrasses), is reviewed in Mediterranean benthic ecosystems. Fish farms constitute a source of organic matter and nutrients (food and fecal pellets) that causes the extirpation of Posidonia oceanica seagrass meadows beneath and near to farm facilities. In addition to direct effects, the nitrogen enrichment of macrophytes tissues increases the grazing pressure by herbivorous fishes and sea urchins. In some cases, the impact can continue to increase several years after the cessation of farming activities. Natural restoration of extirpated seagrass meadows is generally unlikely at the human time scale. Shellfish aquaculture is the cause of the main flow of introduced macrophytes in the Mediterranean; the main vector is the importation of oyster spat from Japan and Korea. North-eastern Pacific seaweeds are now the dominant biotic component of some Mediterranean lagoons (e.g., Thau, Mar Piccolo, and Venice lagoons). In addition to direct effects, mussel aquaculture can constitute a source of larvae that flow with currents, the adults of which can overwhelm seaweed forests (e.g., Carpodesmia mediterranea). Shellfish aquaculture is also a source of fecal pellets, resulting in changes in bottom macrophytes, and a vector of diseases of metazoans, the extirpation of which may change the functioning of recipient macrophyte ecosystems. The edible sea urchin Paracentrotus lividus is sometimes erroneously considered as in decline due to over-harvesting. However, its abundance in the second half of the 20th century was probably a consequence of human impact (overfishing of its predatory fish, organic pollution. This man-induced proliferation resulted in the extirpation of seaweed forests (e.g., Carpodesmia spp., Treptacantha spp. – formerly Cystoseira spp. – Sargassum spp.; many species are endemic), which play a key role in Mediterranean coastal ecosystems. Therefore, the attempts to restore sea urchin abundance, via seeding of juveniles from hatcheries, has further artificialized the habitats rather than contributing to the restoration of natural ecosystems. Good practices guidelines are proposed aimed at minimizing the impact of aquaculture on macrophytes.

 

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Reviews and syntheses: Bacterial bioluminescence – ecology and impact in the biological carbon pump

Auteurs  : Tous MIO -  Tanet, L., Martini, S., Casalot, L., and Tamburini, C.

Biogeosciences Discuss., https://doi.org/10.5194/bg-2020-64, in review, 2020.

Résumé : Around thirty species of marine bacteria can emit light, a critical characteristic in the oceanic environment where the major part is deprived of sunlight. In this article, we first review current knowledge on bioluminescent bacteria symbiosis in light organs. Then, focusing on gut-associated bacteria, we highlight that recent works, based on omics methods, confirm previous claims about the prominence of bioluminescent bacterial species in fish guts. Such host-symbiont relationships are relatively well established and represent important knowledge in the bioluminescence field. However, the consequences of bioluminescent bacteria continuously released from light organ and through the digestive tracts to the seawater have been barely taken into account at the ecological and biogeochemical level. For too long neglected, we propose to consider the role of bioluminescent bacteria, and to reconsider the biological carbon pump taking into account the bioluminescence effect (bioluminescence shunt hypothesis). Indeed, it has been shown that marine snow and fecal pellets are often luminous due to microbial colonization, which makes them a visual target. These luminous particles seem preferentially consumed by organisms of higher trophic levels in comparison to non-luminous ones. As a consequence, the sinking rate of consumed particles could be either increased (due to repackaging) or reduced (due to sloppy feeding or coprophagy/coprorhexy) which can imply a major impact on global biological carbon fluxes. Finally, we propose a strategy, at a worldwide scale, relying on recently developed instrumentation and methodological tools to quantify the impact of bioluminescent bacteria in the biological carbon pump.

 

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The Transpolar Drift as a Source of Riverine and Shelf‐Derived Trace Elements to the Central Arctic Ocean

Auteurs :
Matthew A. Charette
Lauren E. Kipp
Laramie T. Jensen
Jessica S. Dabrowski
Laura M. Whitmore
Jessica N. Fitzsimmons
Tatiana Williford
Adam Ulfsbo
Elizabeth Jones
Randelle M. Bundy
Sebastian M. Vivancos
Katharina Pahnke
Seth G. John
Yang Xiang
Mariko Hatta
Mariia V. Petrova (MIO)
Lars‐Eric Heimbürger‐Boavida (MIO)
Dorothea Bauch
Robert Newton
Angelica Pasqualini
Alison M. Agather
Rainer M.W. Amon
Robert F. Anderson
Per S. Andersson
Ronald Benner
Katlin L. Bowman
R. Lawrence Edwards
Sandra Gdaniec
Loes J.A. Gerringa
Aridane G. González
Mats Granskog
Brian Haley
Chad R. Hammerschmidt
Dennis A. Hansell
Paul B. Henderson
David C. Kadko
Karl Kaiser
Patrick Laan
Phoebe J. Lam
Carl H. Lamborg
Martin Levier
Xianglei Li
Andrew R. Margolin
Chris Measures
Rob Middag
Frank J. Millero
Willard S. Moore
Ronja Paffrath
Hélène Planquette
Benjamin Rabe
Heather Reader
Robert Rember
Micha J.A. Rijkenberg
Matthieu Roy‐Barman
Michiel Rutgers van der Loeff
Mak Saito
Ursula Schauer
Peter Schlosser
Robert M. Sherrell
Alan M. Shiller
Hans Slagter
Jeroen E. Sonke
Colin Stedmon
Ryan J. Woosley
Ole Valk
Jan van Ooijen
Ruifeng Zhang
… See fewer authors
First published: 08 April 2020
https://doi.org/10.1029/2019JC015920

 

Résumé : A major surface circulation feature of the Arctic Ocean is the Transpolar Drift (TPD), a current that transports river‐influenced shelf water from the Laptev and East Siberian Seas toward the center of the basin and Fram Strait. In 2015, the international GEOTRACES program included a high‐resolution pan‐Arctic survey of carbon, nutrients, and a suite of trace elements and isotopes (TEIs). The cruises bisected the TPD at two locations in the central basin, which were defined by maxima in meteoric water and dissolved organic carbon concentrations that spanned 600 km horizontally and ~25‐50 m vertically. Dissolved TEIs such as Fe, Co, Ni, Cu, Hg, Nd, and Th, which are generally particle‐reactive but can be complexed by organic matter, were observed at concentrations much higher than expected for the open ocean setting. Other trace element concentrations such as Al, V, Ga, and Pb were lower than expected due to scavenging over the productive East Siberian and Laptev shelf seas. Using a combination of radionuclide tracers and ice drift modeling, the transport rate for the core of the TPD was estimated at 0.9 ± 0.4 Sv (106 m3 s‐1). This rate was used to derive the mass flux for TEIs that were enriched in the TPD, revealing the importance of lateral transport in supplying materials beneath the ice to the central Arctic Ocean and potentially to the North Atlantic Ocean via Fram Strait. Continued intensification of the Arctic hydrologic cycle and permafrost degradation will likely lead to an increase in the flux of TEIs into the Arctic Ocean.

 

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Diversity and evolution of bacterial bioluminescence genes in the global ocean

 

Auteurs : Tous MIO -Thomas Vannier, Pascal Hingamp, Floriane Turrel, Lisa Tanet, Magali Lescot, Youri Timsit
NAR Genomics and Bioinformatics, Volume 2, Issue 2, June 2020, lqaa018, https://doi.org/10.1093/nargab/lqaa018
Published: 14 March 2020

Résumé : Although bioluminescent bacteria are the most abundant and widely distributed of all light-emitting organisms, the biological role and evolutionary history of bacterial luminescence are still shrouded in mystery. Bioluminescence has so far been observed in the genomes of three families of Gammaproteobacteria in the form of canonical lux operons that adopt the CDAB(F)E(G) gene order. LuxA and luxB encode the two subunits of bacterial luciferase responsible for light-emission. Our deep exploration of public marine environmental databases considerably expands this view by providing a catalog of new lux homolog sequences, including 401 previously unknown luciferase-related genes. It also reveals a broader diversity of the lux operon organization, which we observed in previously undescribed configurations such as CEDA, CAED and AxxCE. This expanded operon diversity provides clues for deciphering lux operon evolution and propagation within the bacterial domain. Leveraging quantitative tracking of marine bacterial genes afforded by planetary scale metagenomic sampling, our study also reveals that the novel lux genes and operons described herein are more abundant in the global ocean than the canonical CDAB(F)E(G) operon.

 

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Impacts of copper and lead exposure on prokaryotic communities from contaminated contrasted coastal seawaters: the influence of previous metal exposure

 

Auteurs : Clément Coclet (MIO), Cédric Garnier (MIO ǂ), Gaël Durrieu  (MIO), Sébastien D’onofrio ( MIO)  , Nicolas Layglon (MIO) , Jean-François Briand, Benjamin Misson (MIO)

FEMS Microbiology Ecology, fiaa048, https://doi.org/10.1093/femsec/fiaa048
Published: 19 March 2020

Résumé : Our understanding of environmental factors controlling prokaryotic community is largely hampered by the large environmental variability across spatial scales (e.g. trace metal contamination, nutrient enrichment, physico-chemical variations) and the broad diversity of bacterial pre-exposure to environmental factors. In this article, we investigated the specific influence of copper (Cu) and lead (Pb) on prokaryotic communities from the uncontaminated site, using mesocosm experiments. In addition, we studied how pre-exposure (i.e. life history) affects communities, with reference to previous metal exposure on the response of three prokaryotic communities to similar Cu exposition. This study showed a stronger influence of Cu contamination than Pb contamination on prokaryotic diversity and structure. We identified 12, and 34 bacterial families and genera, respectively, contributing to the significant differences observed in community structure between control and spiked conditions. Taken altogether, our results point towards a combination of direct negative responses to Cu contamination and indirect responses mediated by interaction with phytoplankton. These identified responses were largely conditioned by the previous exposure of community to contaminants.

 

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A multi-omics analysis suggests links between the differentiated surface metabolome and epiphytic microbiota along the thallus of a Mediterranean seaweed holobiont

 

Auteurs : Benoît Paix, Nathan Carriot, Raphaëlle Barry-Martinet, Stéphane Greff, Benjamin Misson (MIO), Jean-François Briand and Gérald Culioli

Front. Microbiol. | doi: 10.3389/fmicb.2020.00494

Résumé : Marine macroalgae constitute an important living resource in marine ecosystems and complex ecological interactions occur at their surfaces with microbial communities. In this context, the present study aimed to investigate how the surface metabolome of the algal holobiont Taonia atomaria could drive epiphytic microbiota variations at the thallus scale. First, a clear discrimination was observed between algal surface, planktonic and rocky prokaryotic communities. These data strengthened the hypothesis of an active role of the algal host in the selection of epiphytic communities. Moreover, significant higher epibacterial density and α-diversity were found at the basal algal parts compared to the apical ones, suggesting a maturation gradient of the community along the thallus. In parallel, a multiplatform mass spectrometry-based metabolomics study, using molecular networking to annotate relevant metabolites, highlighted a clear chemical differentiation at the algal surface along the thallus with similar clustering as for microbial communities. In that respect, higher amounts of sesquiterpenes, phosphatidylcholines (PCs), and diacylglycerylhydroxymethyl-N,N,N-trimethyl--alanines (DGTAs) were observed at the apical regions while dimethylsulfoniopropionate (DMSP) and carotenoids were predominantly found at the basal parts of the thalli. A weighted UniFrac distance-based redundancy analysis linking the metabolomics and metabarcoding datasets indicated that these surface compounds, presumably of algal origin, may drive the zonal variability of the epibacterial communities. As only few studies were focused on microbiota and metabolome variation along a single algal thallus, these results improved our understanding about seaweed holobionts. Through this multi-omics approach at the thallus scale, we suggested a plausible scenario where the chemical production at the surface of T. atomaria, mainly induced by the algal physiology, could explain the specificity and the variations of the surface microbiota along the thallus.

 

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Impact of Contrasted Weather Conditions on CDOM Absorption/Fluorescence and Biogeochemistry in the Eastern Lagoon of New Caledonia

 

Auteurs : Dupouy Cécile (MIO), Röttgers Rüdiger, Tedetti Marc (MIO), Frouin Robert, Lantoine François, Rodier Martine (EIO puis MIO), Martias Chloe (MIO), Goutx Madeleine (MIO)

Front. Earth Sci., 20 March 2020 | https://doi.org/10.3389/feart.2020.00054

Résumé : New Caledonia (Southwest Pacific), like all tropical Pacific Island countries, is impacted by weather events, climate change, and local anthropogenic forcing. Strong erosion of particles and dissolved organic matter (DOM) from ultramafic rocks, associated with trace metals dissemination (i.e., nickel, manganese and cobalt), potentially affects lagoon waters and coral reefs surrounding the main island. The CALIOPE (CALedonian Inherent Optical PropErties) cruises were performed along the Eastern Lagoon of New Caledonia (ELNC) (400 km, 13 transects from Bay to open ocean, 51 stations) during contrasted meteorological conditions: a dry period (October 2011), a windy situation (March 2014), and a strong rainy event (March 2016). CDOM absorption and fluorescence (FDOM), particulate absorption, backscattering, suspended particulate matter (SPM), total chlorophyll a (TChla), nutrients (NOx), pigment and phytoplankton composition were measured. Among the four CDOM fluorophores, the humic-like component (λEx/λEm: 235/460 nm), assimilated to a photoproduct of terrestrial organic matter, had relatively low fluorescence compared to protein-like fluorophores. As CDOM absorption, particulate absorption, backscattering, SPM, total chlorophyll a (TChla) and nutrient (NOx) concentrations, this humic-like material generally showed the highest values during rainfall events, the latter inducing an increase in riverine terrigeneous inputs and change toward higher phytoplankton size classes. The tyrosine 1-like (λEx/λEm: 220, 275/304 nm) and tryptophan-like fluorophores (λEx/λEm: 230, 300/352 nm) were strongly influenced by wind displaying a 7-fold and 3-fold increase, respectively in windy situation compared to calm conditions. These increases could be related to enhancements of autochthonous biological activities (highest mean concentrations of Synechococcus spp., phycoerythrin, pico- and nano-eukaryotes, heterotrophic bacteria and nanoplankton observed in wind condition) through the inputs of organic and mineral materials issued from the wind-induced sediment resuspension, atmospheric deposition and water mass mixing. By contrast, the tyrosine 2-like fluorophore (λEx/λEm: 245, 275/304 nm) substantially increased during rain events and presented the lowest values in wind conditions. These strong increases may be linked to the stimulation of planktonic activities due to riverine inputs. Therefore, this study emphasizes the significant differential influence of weather conditions (calm/wind/rain) on biogeochemistry and CDOM/FDOM distributions in the ELNC.

 

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Dissolved organic matter stimulates N2 fixation and nifH gene expression in Trichodesmium

 

Auteurs : Mar Benavides (MIO) , Solange Duhamel, France Van Wambeke (MIO), Katyanne M Shoemaker, Pia H Moisander, Ellen Salamon, Lasse Riemann, Sophie Bonnet (MIO)
FEMS Microbiology Letters, fnaa034, https://doi.org/10.1093/femsle/fnaa034
Published:
21 February 2020

Résumé : Mixotrophy, the combination of heterotrophic and autotrophic nutrition modes, is emerging as the rule rather than the exception in marine photosynthetic plankton. Trichodesmium, a prominent diazotroph ubiquitous in the (sub)tropical oceans, is generally considered to obtain energy via autotrophy. While the ability of Trichodesmium to use dissolved organic phosphorus when deprived of inorganic phosphorus sources is well known, the extent to which this important cyanobacterium may benefit from other dissolved organic matter (DOM) sources is unknown. Here we provide evidence of carbon-, nitrogen- and phosphorus-rich DOM molecules enhancing N2 fixation rates and nifH gene expression in natural Trichodesmium colonies collected at two stations in the western tropical South Pacific. Sampling at a third station located in the oligotrophic South Pacific Gyre revealed no Trichodesmium but showed presence of UCYN-B, although no nifH expression was detected. Our results suggest that Trichodesmium may behave mixotrophically in response to certain environmental conditions, providing them with metabolic plasticity and adding up to the view that mixotrophy is widespread among marine microbes.

 

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Sub-oxycline methane oxidation can fully uptake CH4 produced in sediments: case study of a lake in Siberia

 

Auteurs : Frédéric Thalasso, Armando Sepulveda-Jauregui, Laure Gandois, Karla Martinez-Cruz, Oscar Gerardo-Nieto, María S. Astorga-España, Roman Teisserenc, Céline Lavergne , Nikita Tananaev, Maialen Barret, Léa Cabrol (MIO)

Scientific Reports volume 10, Article number: 3423

Résumé : It is commonly assumed that methane (CH4) released by lakes into the atmosphere is mainly produced in anoxic sediment and transported by diffusion or ebullition through the water column to the surface of the lake. In contrast to that prevailing idea, it has been gradually established that the epilimnetic CH4 does not originate exclusively from sediments but is also locally produced or laterally transported from the littoral zone. Therefore, CH4 cycling in the epilimnion and the hypolimnion might not be as closely linked as previously thought. We utilized a high-resolution method used to determine dissolved CH4 concentration to analyze a Siberian lake in which epilimnetic and hypolimnetic CH4 cycles were fully segregated by a section of the water column where CH4 was not detected. This layer, with no detected CH4, was well below the oxycline and the photic zone and thus assumed to be anaerobic. However, on the basis of a diffusion-reaction model, molecular biology, and stable isotope analyses, we determined that this layer takes up all the CH4 produced in the sediments and the deepest section of the hypolimnion. We concluded that there was no CH4 exchange between the hypolimnion (dominated by methanotrophy and methanogenesis) and the epilimnion (dominated by methane lateral transport and/or oxic production), resulting in a vertically segregated lake internal CH4 cycle.

 

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The delayed island mass effect: How islands can remotely trigger blooms in the oligotrophic ocean

 

Auteurs : Messié, M. (MIO puis Monterey Bay Aquarium Research Institute,) , A. Petrenko (MIO) , A.M. Doglioli (MIO), C. Aldebert, E. Martinez, G. Koenig (MIO) , S. Bonnet (MIO) and T. Moutin (MIO)

Geophysical Research Letters, 47(2), e2019GL085282, doi:10.1029/2019GL085282

Résumé : In oligotrophic gyres of the tropical ocean, islands can enhance phytoplankton biomass and create hotspots of productivity and biodiversity. This “Island Mass Effect” (IME) is typically identified by increased chlorophyll concentrations next to an island. Here we use a simple plankton model in a Lagrangian framework to represent an unexplained open ocean bloom, demonstrating how islands could have triggered it remotely. This new type of IME, termed “delayed IME”, occurs when nitrate is limiting, N:P ratios are low, and excess phosphate and iron remain in water masses after an initial bloom associated with a “classical” IME. Nitrogen fixers then slowly utilize leftover phosphate and iron while water masses get advected away, resulting in a bloom decoupled in time (several weeks) and space (hundreds of km) from island-driven nutrient supply. This study suggests that the fertilizing effect of islands on phytoplankton may have been largely underestimated.

 

Accès en ligne

Implementation of an end-to-end model of the Gulf of Lions ecosystem (NW Mediterranean Sea). I. Parameterization, calibration and evaluation

 

Auteurs : Daniela Bănaru (MIO), Frederic Diaz (MIO), Philippe Verley,  Rose Campbell,  Jonathan Navarro (MIO), Christophe Yohia,  Ricardo Oliveros-Ramos, Capucine Mellon-Duval,  Yunne-Jai Shin

Ecological Modelling : Volume 401, 1 June 2019, Pages 1-19
Soumis le : jeudi 30 janvier 2020
Dernière modification le : jeudi 20 février 2020

Résumé : An end-to-end model named OSMOSE-GoL has been built for the Gulf of Lions, the main French Mediterranean fishing area. This spatialized dynamic model links the coupled hydrodynamic and biogeochemical model Eco3M-S/SYMPHONIE (LTL – low trophic level model) to OSMOSE (HTL – high trophic level model). It includes 15 compartments of living organisms, five from the LTL model (i.e. nanophytoplankton, microphytoplankton, nanozooplankton, microzooplankton and mesozooplankton) and ten from the HTL model (northern krill, southern shortfin squid, European pilchard, European anchovy, European sprat, Atlantic horse mackerel, Atlantic mackerel, blue whiting, European hake and Atlantic bluefin tuna). With the exception of northern krill and European sprat, all HTL species are commercially exploited and undergo fisheries mortality pressure. The modeled species represent more than 70% of annual catches in this area. This paper presents the parameterization, calibration and evaluation of this model with satellite data for phytoplankton and with biomass, landings, diet and trophic level data for HTL groups. For most species, the diets in output of OSMOSE-GoL are similar to field and literature data in terms of dominant prey groups and species. However, some differences were observed. Various reasons may explain the mismatch between the modeled diet and field data. Benthic prey sometimes observed in the stomach content of the HTL predators were not modeled in OSMOSE-GoL. Field studies were carried out at specific periods and locations, while our data concern the period 2001–2004 and the entire modeled domain. Inter- and intra-annual variations in spatial distribution and density of prey may also explain these differences. The model estimates trophic level values similar to those cited in the literature for all the HTL compartments. These values are also close to the trophic levels estimated by a previous Ecopath model for the same area and period. Even though some improvements are still possible, this model may already be of use to explore fishery or Marine Protected Areas scenarios for socio-ecosystem management issues.

 

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Green Edge ice camp campaigns: understanding the processes controlling the under-ice Arctic phytoplankton spring bloom

 

Auteurs : Massicotte, P., Amiraux, R., Amyot, M.-P., Archambault, P., Ardyna, M., Arnaud, L., Artigue, L., Aubry, C., Ayotte, P., Bécu, G., Bélanger, S., Benner, R., Bittig, H. C., Bricaud, A., Brossier, É., Bruyant, F., Chauvaud, L., Christiansen-Stowe, D., Claustre, H., Cornet-Barthaux, V. (MIO), Coupel, P., Cox, C., Delaforge, A., Dezutter, T., Dimier, C., Domine, F., Dufour, F., Dufresne, C., Dumont, D., Ehn, J., Else, B., Ferland, J., Forget, M.-H., Fortier, L., Galí, M., Galindo, V., Gallinari, M., Garcia, N.(MIO) , Gérikas Ribeiro, C., Gourdal, M., Gourvil, P., Goyens, C., Grondin, P.-L., Guillot, P., Guilmette, C., Houssais, M.-N., Joux, F., Lacour, L., Lacour, T., Lafond, A.(MIO) , Lagunas, J., Lalande, C., Laliberté, J., Lambert-Girard, S., Larivière, J., Lavaud, J., LeBaron, A., Leblanc, K. (MIO), Le Gall, F., Legras, J.(MIO) , Lemire, M., Levasseur, M., Leymarie, E., Leynaert, A., Lopes dos Santos, A., Lourenço, A., Mah, D., Marec, C., Marie, D., Martin, N., Marty, C., Marty, S., Massé, G., Matsuoka, A., Matthes, L., Moriceau, B., Muller, P.-E., Mundy, C.-J., Neukermans, G., Oziel, L., Panagiotopoulos, C.(MIO) , Pangrazi, J.-J., Picard, G., Picheral, M., Pinczon du Sel, F., Pogorzelec, N., Probert, I., Quéguiner, B.(MIO) , Raimbault, P.(MIO), Ras, J., Rehm, E., Reimer, E., Rontani, J.-F.(MIO), Rysgaard, S., Saint-Béat, B., Sampei, M., Sansoulet, J., Schmechtig, C., Schmidt, S., Sempéré, R.(MIO), Sévigny, C., Shen, Y., Tragin, M., Tremblay, J.-É., Vaulot, D., Verin, G., Vivier, F., Vladoiu, A., Whitehead, J., and Babin, M.

Earth Syst. Sci. Data, 12, 151–176, https://doi.org/10.5194/essd-12-151-2020, 2020.

Résumé : The Green Edge initiative was developed to investigate the processes controlling the primary productivity and fate of organic matter produced during the Arctic phytoplankton spring bloom (PSB) and to determine its role in the ecosystem. Two field campaigns were conducted in 2015 and 2016 at an ice camp located on landfast sea ice southeast of Qikiqtarjuaq Island in Baffin Bay (67.4797∘ N, 63.7895∘ W). During both expeditions, a large suite of physical, chemical and biological variables was measured beneath a consolidated sea-ice cover from the surface to the bottom (at 360 m depth) to better understand the factors driving the PSB. Key variables, such as conservative temperature, absolute salinity, radiance, irradiance, nutrient concentrations, chlorophyll a concentration, bacteria, phytoplankton and zooplankton abundance and taxonomy, and carbon stocks and fluxes were routinely measured at the ice camp. Meteorological and snow-relevant variables were also monitored. Here, we present the results of a joint effort to tidy and standardize the collected datasets, which will facilitate their reuse in other Arctic studies.

 

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Occurrence of organic plastic additives in surface waters of the Rhône River (France)

 

Auteurs : Natascha Schmidt, Javier Castro-Jiménez, Vincent Fauvelle, Mélanie Ourgaud, Richard Sempéré (tous MIO)

Environmental Pollution

Available online 16 November 2019, 113637- https://doi.org/10.1016/j.envpol.2019.113637

Résumé : cxWe present here a comprehensive study (1-year regular sampling) on the occurrence of major families of organic plastic additives in the Rhône River surface waters. Potential sources and contaminant export are also discussed. A total of 22 dissolved phase samples were analyzed for 22 organic additives mainly used in the plastic industry, including organophosphate esters (OPEs), phthalates (PAEs) and bisphenols (BPs). Our results indicate that PAEs were the most abundant class, with concentrations ranging from 97 to 541 ng L−1, followed by OPEs (85–265 ng L−1) and BPs (4–21 ng L−1). Among PAEs, diethylhexyl phthalate (DEHP) was the most abundant compound, whereas TCPP (Tris(1-chloro-2-propyl) phosphate) and TnBP (Tri(n-butyl)phosphate) were the predominant OPEs. Bisphenol S was the only BP detected. 5–54 metric tons year−1 of dissolved organic plastic additives of emerging concern are estimated to be exported to the Gulf of Lion by the Rhône River, which is the main freshwater source of the Mediterranean Sea.

 

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Ecological networks: Pursuing the shortest path, however narrow and crooked

 

Auteurs : Costa, A., Martín González, A.M., Guizien, K., Doglioli, A. (MIO), M., Gómez, J.M., Petrenko A. (MIO), Allesina S.

Scientific Reports volume 9, Article number: 17826 (2019)

Résumé : Representing data as networks cuts across all sub-disciplines in ecology and evolutionary biology. Besides providing a compact representation of the interconnections between agents, network analysis allows the identification of especially important nodes, according to various metrics that often rely on the calculation of the shortest paths connecting any two nodes. While the interpretation of a shortest paths is straightforward in binary, unweighted networks, whenever weights are reported, the calculation could yield unexpected results. We analyzed 129 studies of ecological networks published in the last decade that use shortest paths, and discovered a methodological inaccuracy related to the edge weights used to calculate shortest paths (and related centrality measures), particularly in interaction networks. Specifically, 49% of the studies do not report sufficient information on the calculation to allow their replication, and 61% of the studies on weighted networks may contain errors in how shortest paths are calculated. Using toy models and empirical ecological data, we show how to transform the data prior to calculation and illustrate the pitfalls that need to be avoided. We conclude by proposing a five-point check-list to foster best-practices in the calculation and reporting of centrality measures in ecology and evolution studies.

 

Article en ligne

Late spring bloom development of pelagic diatoms in Baffin Bay

 

Auteurs : Lafond, A. (MIO), Leblanc, K (MIO)., Quéguiner, B.(MIO), Moriceau, B., Leynaert, A., Cornet, V.(MIO), Legras, J., Ras, J., Parenteau, M., Garcia, N.(MIO), Babin, M. and Tremblay, J.-E.

Special Collection: Green Edge . Elem Sci Anth, 7(1), p.44. DOI: http://doi.org/10.1525/elementa.382

Résumé : The Arctic Ocean is particularly affected by climate change, with changes in sea ice cover expected to impact phytoplankton primary production. During the Green Edge expedition, the development of the late spring–early summer diatom bloom was studied in relation with the sea ice retreat by multiple transects across the marginal ice zone. Biogenic silica concentrations and uptake rates were measured. In addition, diatom assemblage structures and their associated carbon biomass were determined, along with taxon-specific contributions to total biogenic silica production using the fluorescent dye PDMPO. Results indicate that a diatom bloom developed in open waters close to the ice edge, following the alleviation of light limitation, and extended 20–30 km underneath the ice pack. This actively growing diatom bloom (up to 0.19 μmol Si L–1 d–1) was associated with high biogenic silica concentrations (up to 2.15 μmol L–1), and was dominated by colonial fast-growing centric (Chaetoceros spp. and Thalassiosira spp.) and ribbon-forming pennate species (Fragilariopsis spp./Fossula arctica). The bloom remained concentrated over the shallow Greenland shelf and slope, in Atlantic-influenced waters, and weakened as it moved westwards toward ice-free Pacific-influenced waters. The development resulted in a near depletion of all nutrients eastwards of the bay, which probably induced the formation of resting spores of Melosira arctica. In contrast, under the ice pack, nutrients had not yet been consumed. Biogenic silica and uptake rates were still low (respectively <0.5 μmol L–1 and <0.05 μmol L–1 d–1), although elevated specific Si uptake rates (up to 0.23 d–1) probably reflected early stages of the bloom. These diatoms were dominated by pennate species (Pseudo-nitzschia spp., Ceratoneis closterium, and Fragilariopsis spp./Fossula arctica). This study can contribute to predictions of the future response of Arctic diatoms in the context of climate change.

 

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Resupply of mesopelagic dissolved iron controlled by particulate iron composition

 

Auteurs : Bressac M., C. Guieu, M.J. Ellwood, A. Tagliabue, T. Wagener (MIO), E.C. Laurenceau-Cornec, H. Whitby, G. Sarthou, P.W. Boyd.

Nature Geoscience, 2019, doi:10.1038/s41561-019-0476-6.

Résumé : 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 limited due to sparse observations. There is a lack of empirical evidence as to what controls the subsurface iron remineralization due to difficulties in studying mesopelagic biogeochemistry. Here we present estimates of particulate transformations to dissolved iron, concurrent oxygen consumption and iron-binding ligand replenishment based on in situ mesopelagic experiments. Dissolved iron regeneration efficiencies (that is, replenishment over oxygen consumption) were 10- to 100-fold higher in low-dust subantarctic waters relative to higher-dust Mediterranean sites. Regeneration efficiencies are heavily influenced by particle composition. Their make-up dictates ligand release, controls scavenging, modulates ballasting and may lead to the differential remineralization of biogenic versus lithogenic iron. At high-dust sites, these processes together increase the iron remineralization length scale. Modelling reveals that in oceanic regions near deserts, enhanced lithogenic fluxes deepen the ferricline, which alter the vertical patterns of dissolved iron replenishment, and set its redistribution at the global scale. Such wide-ranging regeneration efficiencies drive different vertical patterns in dissolved iron replenishment across oceanic provinces.

 

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The global distribution and evolutionary history of the pT26‐2 archaeal plasmid family

 

Auteurs : Catherine Badel, Gaël Erauso (MIO), Annika L. Gomez, Ryan Catchpole, Mathieu Gonnet, Jacques Oberto, Patrick Forterre, Violette Da Cunha

Environmental Microbiology -First published: 10 September 2019 - https://doi.org/10.1111/1462-2920.14800

Résumé : Although plasmids play an important role in biological evolution, the number of plasmid families well‐characterized in terms of geographical distribution and evolution remains limited, especially in archaea. Here, we describe the first systematic study of an archaeal plasmid family, the pT26‐2 plasmid family. The in‐depth analysis of the distribution, biogeography and host–plasmid co‐evolution patterns of 26 integrated and 3 extrachromosomal plasmids of this plasmid family shows that they are widespread in Thermococcales and Methanococcales isolated from around the globe but are restricted to these two orders. All members of the family share seven core genes but employ different integration and replication strategies. Phylogenetic analysis of the core genes and CRISPR spacer distribution suggests that plasmids of the pT26‐2 family evolved with their hosts independently in Thermococcales and Methanococcales, despite these hosts exhibiting similar geographic distribution. Remarkably, core genes are conserved even in integrated plasmids that have lost replication genes and/or replication origins suggesting that they may be beneficial for their hosts. We hypothesize that the core proteins encode for a novel type of DNA/protein transfer mechanism, explaining the widespread oceanic distribution of the pT26‐2 plasmid family.

 

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Pathways of Organic Carbon Downward Transport by the Oceanic Biological Carbon Pump

 

Auteur : Frédéric Le Moigne (MIO)

Front. Mar. Sci., 09 October 2019 | https://doi.org/10.3389/fmars.2019.00634

Résumé : The oceanic biological carbon pump (BCP) regulates the Earth carbon cycle by transporting part of the photosynthetically fixed CO2 into the deep ocean. Suppressing this mechanism would result in an important increase of atmospheric CO2 level. The BCP occurs mainly in the form of (1) organic carbon (OC) particles sinking out the surface ocean, of (2) neutrally buoyant OC (dissolved or particulate) entrained by downward water masses movements and/or mixing, and of (3) active transport of OC by migrating animals such as zooplankton and fishes. These various pools of OC differ in size since their sinking, production and decomposition rates vary spatially and temporally. Moreover, the OC transported to depths via these various export pathways as well as their decomposition pathways all have different ecological origins and therefore may response differently to climate changes. Currently, most ocean biogeochemical models do not resolve these various of OC pathways explicitly; rather, they imply that OC is therein created and destroyed equally. In addition, the organic composition of these various pools is largely unknown, especially at depths below 500 m. Here, known processes of OC export from the surface ocean to the mesopelagic zone (100–1000 m) are briefly reviewed. Three OC export pathways and some of their sub-categories are considered. I refer to published studies of OC fluxes associated with the specific downward exportpathways and identify gaps that need to be addressed to better understand the OC fluxes associated with the BCP.

 

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Metabolomic and proteomic changes induced by growth inhibitory concentrations of copper in the biofilm-forming marine bacterium Pseudoalteromonas lipolytica

 

Auteurs : L. Favre, A.Ortalo-Magné, L. Kerloch, C. Pichereaux, B. Misson (MIO), J. Briand, C. Garnier (MIO) and G. Culioli

Metallomics, 2019, DOI: 10.1039/C9MT00184K

Résumé : Copper is an essential element for living cells but this metal is present in some marine environments at so high concentrations that it can be toxic for numerous organisms. In polluted areas, marine organisms may develop specific adaptive responses to prevent cell damage. To investigate the influence of copper on the metabolism of a single organism, a dual approach combining metabolomics and proteomics was undertaken on the biofilm-forming bacterial strain Pseudoalteromonas lipolytica TC8. In order to highlight differential adaptation according to the phenotype, the response of P. lipolytica TC8 to copper stress was studied in planktonic and biofilm culture modes under growth inhibitory copper concentrations. As expected, copper exposure led to the induction of defense and detoxification mechanisms. Specific metabolite and protein profiles were thus observed in each condition (planktonic vs biofilm and control vs copper-treated cultures). Copper exposure seemed to induce drastic changes of the lipid composition of the bacterial cell membrane and to modulate the abundance of proteins functionally known to be involved in copper cell homeostasis in both planktonic and biofilm culture modes. Much more proteins differentially expressed after copper treatment were observed in biofilms than in planktonic cells which could indicate a more heterogeneous response of biofilm cells to this metallic stress.

 

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A multidisciplinary analytical framework to delineate spawning areas and quantify larval dispersal in coastal fish

 

Auteurs : T. Legrand (MIO), A. Di Franco, E. Ser-Giacomi, A. Caló, V. Rossi (MIO)

Marine Environmental Research, in press, doi:10.1016/j.marenvres.2019.104761

Résumé : Assessing larval dispersal is essential to understand the structure and dynamics of marine populations. However, knowledge about early-life dispersal is sparse, and so is our understanding of the spawning process, perhaps the most obscure component of biphasic life cycles. Indeed, poorly known species-specific spawning modality and species-specific early-life traits, as well as the high spatio-temporal variability of the oceanic circulation experienced during larval drift, hamper our ability to appraise the realized connectivity of coastal fishes. Here, we propose an analytical framework which combines Lagrangian modelling, network theory, otolith analyses and biogeographical information to pinpoint and characterize larval sources which are then grouped into discrete spawning areas. Such well-delineated larval sources allow improving the quantitative evaluations of both dispersal scales and connectivity patterns. To illustrate its added value, our approach is applied to two case-studies focusing on Diplodus sargus and Diplodus vulgaris in the Adriatic sea. We evidence robust correlations between otolith geochemistry and modelled spawning areas to assess their relative importance for the larval replenishment of the Apulian coast. Our results show that, contrary to D. sargus, D. vulgaris larvae originate from both eastern and western Adriatic shorelines. Our findings also suggest that dispersal distances and dispersal surfaces scale differently with the pelagic larval duration. Furthermore, 30.8% of D. sargus larvae and 23.6% of D. vulgaris larvae of the Apulian populations originate from Marine protected area (MPA), exemplifying larval export from MPAs to surrounding unprotected areas. This flexible multidisciplinary framework, which can be adjusted to any coastal fish and oceanic system, exploits the explanatory power of a dispersal model, fine-tuned and backed-up by observations, to provide more reliable scientific basis for the management and conservation of marine ecosystems.

Mots clés : Marine connectivity, Lagrangian flow network, Conservation, Marine protected area, Fish natal origins, Coastal fishes, Mediterranean sea, Ecosystem management, Population dynamics, Models-hydrodynamics

 

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Biogeochemical controls of surface ocean phosphate

 

Auteurs : Adam C. Martiny, Michael W. Lomas, Weiwei Fu, Philip W. Boyd, Yuh-ling L. Chen, Gregory A. Cutter, Michael J. Ellwood, Ken Furuya, Fuminori Hashihama, Jota Kanda, David M. Karl, Taketoshi Kodama, Qian P. Li, Jian Ma, Thierry Moutin (MIO), E. Malcolm S. Woodward, J. Keith Moore

Science Advances  28 Aug 2019:
Vol. 5, no. 8, eaax0341
DOI: 10.1126/sciadv.aax0341

Résumé : Surface ocean phosphate is commonly below the standard analytical detection limits, leading to an incomplete picture of the global variation and biogeochemical role of phosphate. A global compilation of phosphate measured using high-sensitivity methods revealed several previously unrecognized low-phosphate areas and clear regional differences. Both observational climatologies and Earth system models (ESMs) systematically overestimated surface phosphate. Furthermore, ESMs misrepresented the relationships between phosphate, phytoplankton biomass, and primary productivity. Atmospheric iron input and nitrogen fixation are known important controls on surface phosphate, but model simulations showed that differences in the iron-to-macronutrient ratio in the vertical nutrient supply and surface lateral transport are additional drivers of phosphate concentrations. Our study demonstrates the importance of accurately quantifying nutrients for understanding the regulation of ocean ecosystems and biogeochemistry now and under future climate conditions.

 

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Shear Stress as a Major Driver of Marine Biofilm Communities in the NW Mediterranean Sea

 

Auteurs : Elisa C. P. Catão, Thomas Pollet, Benjamin Misson (MIO), Cédric Garnier (MIO),  Jean-Francois Ghiglione, Raphaëlle Barry-Martinet, Marine Maintenay, Christine Bressy and Jean-François Briand

Front. Microbiol., 31 July 2019 | https://doi.org/10.3389/fmicb.2019.01768

Résumé : While marine biofilms depend on environmental conditions and substrate, little is known about the influence of hydrodynamic forces. We tested different immersion modes (dynamic, cyclic and static) in Toulon Bay (north-western Mediterranean Sea; NWMS). The static mode was also compared between Toulon and Banyuls Bays. In addition, different artificial surfaces designed to hamper cell attachment (self-polishing coating: SPC; and fouling-release coating: FRC) were compared to inert plastic. Prokaryotic community composition was affected by immersion mode, surface characteristics and site. Rhodobacteriaceae and Flavobacteriaceae dominated the biofilm community structure, with distinct genera according to surface type or immersion mode. Cell density increased with time, greatly limited by hydrodynamic forces, and supposed to delay biofilm maturation. After 1 year, a significant impact of shear stress on the taxonomic structure of the prokaryotic community developed on each surface type was observed. When surfaces contained no biocides, roughness and wettability shaped prokaryotic community structure, which was not enhanced by shear stress. Conversely, the biocidal effect of SPC surfaces, already major in static immersion mode, was amplified by the 15 knots speed. The biofilm community on SPC was 60% dissimilar to the biofilm on the other surfaces and was distinctly colonized by Sphingomonadaceae ((Alter)Erythrobacter). At Banyuls, prokaryotic community structures were more similar between the four surfaces tested than at Toulon, due possibly to a masking effect of environmental constraints, especially hydrodynamic, which was greater than in Toulon. Finally, predicted functions such as cell adhesion confirmed some of the hypotheses drawn regarding biofilm formation over the artificial surfaces tested here.

 

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Towards Integrating Evolution, Metabolism, and Climate Change Studies of Marine Ecosystems.

 

Auteurs : Baltar F, Bayer B, Bednarsek N, Deppeler S, Escribano R, Gonzalez CE, Hansman RL, Mishra RK, Moran MA, Repeta DJ, Robinson C, Sintes E, Tamburini C (MIO), Valentin LE, Herndl GJ

Trends Ecol Evol.  https://doi.org/10.1016/J.TREE.2019.07.003

Faits marquants : Marine ecosystems are changing and the services they provide are threatened by global environmental changes.

Environmental changes can provoke evolution of species, affecting both the realized and fundamental niches of species.

Environmental change can drive evolution, but evolution can also affect environmental conditions.

There is a need for a unifying framework that combines studies of evolution, metabolism, and climate change.

That framework should be based on ecological theory, on the study of the realized and fundamental niche dynamics, their spatial and temporal dynamics, and their potential response to environmental changes.

Global environmental changes are challenging the structure and functioning of ecosystems. However, a mechanistic understanding of how global environmental changes will affect ecosystems is still lacking. The complex and interacting biological and physical processes spanning vast temporal and spatial scales that constitute an ecosystem make this a formidable problem. A unifying framework based on ecological theory, that considers fundamental and realized niches, combined with metabolic, evolutionary, and climate change studies, is needed to provide the mechanistic understanding required to evaluate and forecast the future of marine communities, ecosystems, and their services.

Mots clés : marine ecosystems, niche, evolution, metabolism, climate change

 

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The Delayed Island Mass Effect: How Islands can Remotely Trigger Blooms in the Oligotrophic Ocean

 

Auteurs : Messié, M. (MIO puis Monterey Bay Aquarium Research Institute, Moss Landing, CA, USA)  , Petrenko, A. (MIO), Doglioli, A. M. (MIO), Aldebert, C. (MIO), Martinez, E., Koenig, G. (MIO), Bonnet S. (MIO), Moutin T. (MIO)

Geophysical Research Letters, 47, e2019GL085282. https://doi.org/ 10.1029/2019GL085282 Received 4 SEP 2019 Accepted 20 DEC 2019 Accepted article online 3 JAN 2020

Abstract : In oligotrophic gyres of the tropical ocean, islands can enhance phytoplankton biomass and create hotspots of productivity and biodiversity. This “island mass effect” (IME) is typically identified by increased chlorophyll concentrations next to an island. Here we use a simple plankton model in a Lagrangian framework to represent an unexplained open ocean bloom, demonstrating how islands could have triggered it remotely. This new type of IME, termed “delayed IME,” occurs when nitrate is limiting, N:P ratios are low, and excess phosphate and iron remain in water masses after an initial bloom associated with a “classical” IME. Nitrogen fixers then slowly utilize leftover phosphate and iron while water masses get advected away, resulting in a bloom decoupled in time (several weeks) and space (hundreds of kilometers) from island‐driven nutrient supply. This study suggests that the fertilizing effect of islands on phytoplankton may have been largely underestimated.

 

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Seasonal variation in biochemical and energy content of size-fractionated zooplankton in the Bay of Marseille (North-Western Mediterranean Sea)

 

Auteurs : Chia-Ting Chen, Daniela Bănaru, François Carlotti, Morgane Faucheux, Mireille Harmelin-Vivien (tous MIO)

Journal of Marine SystemsVolume 199, November 2019, 103223

Received 20 March 2019, Revised 12 July 2019, Accepted 23 July 2019, Available online 24 July 2019.

Résumé : Zooplankton plays a prominent role in marine pelagic food webs, but its contribution to organic matter transfer from phytoplankton to upper level consumers is modulated by size and specific composition. The biochemical composition (protein, carbohydrate and lipid concentrations) and energy content of size- and group-fractionated zooplankton were analyzed in the North-Western Mediterranean Sea (Marseille) over 18 months. Proteins were the most abundant biochemical compounds in all size classes and zooplankton groups, and provided the largest part of the energy content. The medium (200–1000 μm) size classes, mainly composed of copepods, crustacean larvae and eggs, presented a higher protein and energy content than both the smallest (80–200 μm) size class, mainly composed of phytoplankton, and the largest (>1000 μm) size classes, composed of siphonophores, salps and chaetognaths. Strong and similar seasonal variations in zooplankton biochemical composition were observed in all size classes, with higher energy content associated with cold oxygen- and nutrient-rich waters in spring 2017 and winter 2018. Thus, the biochemical composition of plankton size classes and groups differed and varied seasonally along with environmental parameters. This novel approach for North-Western Mediterranean Sea may be further related with studies on the energy and nutrient transfer into pelagic food webs and contribute to understanding of how zooplanktivorous fish feeding preferences may be related to the quality of zooplankton prey.

 

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Copernicus Marine Service Ocean State Report, Issue 3

 

Auteurs : Cécile Dupouy (MIO) a participé à cette publication

Karina von Schuckmann (Editor), Pierre-Yves Le Traon (Editor), Neville Smith (Chair) (Review Editor), Ananda Pascual (Review Editor), Samuel Djavidnia (Review Editor), Jean-Pierre Gattuso (Review Editor), Marilaure Grégoire (Review Editor), Glenn Nolan (Review Editor), Signe Aaboe, Eva Aguiar, Enrique Álvarez Fanjul, Aida Alvera-Azcárate, Lotfi Aouf, Rosa Barciela, Arno Behrens, Maria Belmonte Rivas, Sana Ben Ismail, Abderrahim Bentamy, Mireno Borgini, Vittorio E. Brando, Nathaniel Bensoussan, Anouk Blauw, Philippe Bryère, Bruno Buongiorno Nardelli, Ainhoa Caballero, Veli Çağlar Yumruktepe, Emma Cebrian, Jacopo Chiggiato, Emanuela Clementi, Lorenzo Corgnati, Marta de Alfonso, Álvaro de Pascual Collar, Julie Deshayes, Emanuele Di Lorenzo, Jean-Marie Dominici, Cécile Dupouy, Marie Drévillon, Vincent Echevin, Marieke Eleveld, Lisette Enserink, Marcos García Sotillo, Philippe Garnesson, Joaquim Garrabou, Gilles Garric, Florent Gasparin, Gerhard Gayer, Francis Gohin, Alessandro Grandi, Annalisa Griffa, Jérôme Gourrion, Stefan Hendricks, Céline Heuzé, Elisabeth Holland, Doroteaciro Iovino, Mélanie Juza, Diego Kurt Kersting, Silvija Kipson, Zafer Kizilkaya, Gerasimos Korres, Mariliis Kõuts, Priidik Lagemaa, Thomas Lavergne, Heloise Lavigne, Jean-Baptiste Ledoux, Jean-François Legeais, Patrick Lehodey, Cristina Linares, Ye Liu, Julien Mader, Ilja Maljutenko, Antoine Mangin, Ivan Manso-Narvarte, Carlo Mantovani, Stiig Markager, Evan Mason, Alexandre Mignot, Milena Menna, Maeva Monier, Baptiste Mourre, Malte Müller, Jacob Woge Nielsen, Giulio Notarstefano, Oscar Ocaña, Ananda Pascual, Bernardo Patti, Mark R. Payne [ORCID Icon] , Marion Peirache, Silvia Pardo, Begoña Pérez Gómez, Andrea Pisano, Coralie Perruche, K. Andrew Peterson, Marie-Isabelle Pujol, Urmas Raudsepp, Michalis Ravdas, Roshin P. Raj, Richard Renshaw, Emma Reyes, Robert Ricker, Anna Rubio [ORCID Icon] , Michela Sammartino, Rosalia Santoleri, Shubha Sathyendranath, Katrin Schroeder, Jun She, Stefania Sparnocchia, Joanna Staneva, Ad Stoffelen, Tanguy Szekely, Gavin H. Tilstone, Jonathan Tinker, Joaquín Tintoré [ORCID Icon] , Benoît Tranchant, Rivo Uiboupin, Dimitry Van der Zande, Karina von Schuckmann, Richard Wood, Jacob Woge Nielsen, Mikel Zabala, Anna Zacharioudaki, Frédéric Zuberer & Hao Zuo

Journal of Operational Oceanography
Volume 12, 2019 - Issue sup1: Copernicus Marine Service Ocean State Report, Issue 3

 

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How closely do mercury trends in fish and other aquatic wildlife track those in the atmosphere? – Implications for evaluating the effectiveness of the Minamata Convention

 

Auteurs : F Wang, PM Outridge, X Feng, B Meng,  LE Heimbürger-Boavida (MIO), RP Mason

Science of The Total Environment

Volume 674, 15 July 2019, Pages 58-70

Received 17 February 2019, Revised 7 April 2019, Accepted 8 April 2019, Available online 9 April 2019.

Résumé : The Minamata Convention to reduce anthropogenic mercury (Hg) emissions entered into force in 2017, and attention is now focused on how to best monitor its effectiveness at reducing Hg exposure to humans. A key question is how closely Hg concentrations in the human food chain, especially in fish and other aquatic wildlife, will track the changes in atmospheric Hg that are expected to occur following anthropogenic emission reductions. We investigated this question by evaluating several regional groups of case studies where Hg concentrations in aquatic biota have been monitored continuously or intermittently for several decades. Our analysis shows that in most cases Hg time trends in biota did not agree with concurrent Hg trends in atmospheric deposition or concentrations, and the divergence between the two trends has become more apparent over the past two decades. An over-arching general explanation for these results is that the impact of changing atmospheric inputs on biotic Hg is masked by two factors: 1) The aquatic environment contains a large inventory of legacy emitted Hg that remains available for bio-uptake leading to a substantial lag in biotic response time to a change in external inputs; and 2) Biotic Hg trends reflect the dominant effects of changes in multi-causal, local and regional processes (e.g., aquatic or terrestrial biogeochemical processes, feeding ecology, climate) that control the speciation, bioavailability, and bio-uptake of both present-day and legacy emitted Hg. Globally, climate change has become the most prevalent contributor to the divergence. A wide range of biotic Hg outcomes can thus be expected as anthropogenic atmospheric Hg emissions decline, depending on how these processes operate on specific regions and specific organisms. Therefore, evaluating the effectiveness of the Minamata Convention will require biomonitoring of multiple species that represent different trophic and ecological niches in multiple regions of the world.

 

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Updated Global and Oceanic Mercury Budgets for the United Nations Global Mercury Assessment 2018

 

Auteurs : P Outridge, R Mason, F Wang, S Guerrero, LE Heimbürger-Boavida (MIO)

Environ. Sci. Technol.2018522011466-11477
Publication Date  :September 18, 2018
https://doi.org/10.1021/acs.est.8b01246

Résumé : In support of international efforts to reduce mercury (Hg) exposure in humans and wildlife, this paper reviews the literature concerning global Hg emissions, cycling and fate, and presents revised global and oceanic Hg budgets for the 2018 United Nations Global Mercury Assessment. We assessed two competing scenarios about the impacts of 16th – late 19th century New World silver (Ag) mining, which may be the largest human source of atmospheric Hg in history. Consideration of Ag ore geochemistry, historical documents on Hg use, and comparison of the scenarios against atmospheric Hg patterns in environmental archives, strongly support a “low mining emission” scenario. Building upon this scenario and other published work, the revised global budget estimates human activities including recycled legacy emissions have increased current atmospheric Hg concentrations by about 450% above natural levels (prevailing before 1450 AD). Current anthropogenic emissions to air are 2.5 ± 0.5 kt/y. The increase in atmospheric Hg concentrations has driven a ∼ 300% average increase in deposition, and a 230% increase in surface marine waters. Deeper marine waters show increases of only 12–25%. The overall increase in Hg in surface organic soils
(∼15%) is small due to the large mass of natural Hg already present from rock weathering, but this figure varies regionally. Specific research recommendations are made to reduce uncertainties, particularly through improved understanding of fundamental processes of the Hg cycle, and continued improvements in emissions inventories from large natural and anthropogenic sources.

 

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From In Situ to satellite observations of pelagic Sargassum distribution and aggregation in the Tropical North Atlantic Ocean

 

Auteurs : Anouck Ody (MIO), Thierry Thibaut (MIO) , Leo Berline (MIO), , Thomas Changeux (MIO), Jean-Michel André (MIO) ,Cristèle Chevalier (MIO), Aurelie Blanfuné (MIO), Jean Blanchot (MIO), Sandrine Ruitton (MIO), Valérie Stiger-Pouvreau, , Solène Connan, Jacques Grelet, Didier Aurelle (MIO), Mathilde Guené,Hubert Bataille, Celine Bachelier, Dorian Guillemain, Natascha Schmidt (MIO), , Vincent Fauvelle  (MIO), Sophie Guasco (MIO), Frédéric Ménard (MIO).

IN PLoS ONE https://doi.org/10.1371/journal.pone.0222584

Received: December 11, 2018; Accepted: September 3, 2019 ; Published: September 17, 2019

Résumé : The present study reports on observations carried out in the Tropical North Atlantic in summer and autumn 2017, documenting Sargassum aggregations using both ship-deck observations and satellite sensor observations at three resolutions (MSI-10 m, OLCI-300 m, VIIRS-750 m and MODIS-1 km). Both datasets reported that in summer, Sargassum aggregations were mainly observed off Brazil and near the Caribbean Islands, while they accumulated near the African coast in autumn. Based on in situ observations, we propose a five-class typology allowing standardisation of the description of in situ Sargassum raft shapes and sizes. The most commonly observed Sargassum raft type was windrows, but large rafts composed of a quasi-circular patch hundreds of meters wide were also observed. Satellite imagery showed that these rafts formed larger Sargassum aggregations over a wide range of scales, with smaller aggregations (of tens of m2 area) nested within larger ones (of hundreds of km2). Match-ups between different satellite sensors and in situ observations were limited for this dataset, mainly because of high cloud cover during the periods of observation. Nevertheless, comparisons between the two datasets showed that satellite sensors successfully detected Sargassum abundance and aggregation patterns consistent with in situ observations. MODIS and VIIRS sensors were better suited to describing the Sargassum aggregation distribution and dynamics at Atlantic scale, while the new sensors, OLCI and MSI, proved their ability to detect Sargassum aggregations and to describe their (sub-) mesoscale nested structure. The high variability in raft shape, size, thickness, depth and biomass density observed in situ means that caution is called for when using satellite maps of Sargassum distribution and biomass estimation. Improvements would require additional in situ and airborne observations or very high-resolution satellite imagery.

 

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Dynamics of trace metals in a shallow coastal ecosystem: insights from the Gulf of Gabès (southern Mediterranean Sea)

 

Auteurs : Sandrine Chifflet (MIO, Marc Tedetti (MIO), Hana Zouch, Rania Fourati, Hatem Zaghden, Boubaker Elleuch, Marianne Quéméneur (MIO), Fatma Karray, Sami Sayadi

AIMS Environmental Science, 2019, 6(4): 277-297. doi: 10.3934/environsci.2019.4.277.

Received: 23 May 2019 , Accepted: 26 June 2019 , Published: 04 July 2019

Résumé : Coastal areas are sites of discharge of anthropogenic compounds, such as trace metals. In seawater, trace metals have a strong affinity for particulate organic matter or clay mineral and tend to accumulate in sediments. However, natural events and human activities can cause disturbances in surface sediments involving modification of chemical balances and contamination of surrounding waters. Here, we investigated the dynamics of trace metals in the Sfax coastal area (Gulf of Gabès, southern Mediterranean Sea), a shallow coastal ecosystem impacted by tides and submitted to urban/industrial effluents. We presented the spatial distribution of trace metals concentrations, their potential mobility in sediments and evaluated the potential sources of target elements in surface waters. The highest concentration levels in surficial sediments (3.51 µg/g) and surface waters (0.25 µg/L) were found for Cd. The latter showed a great affinity (50%) for the exchangeable phase while other elements (Cu, Cr and Ni) were found in most residual phases, reducing the environmental risk. Pb and Zn, associated Fe/Mn oxyhydroxides revealed potential inputs from urban and industrial effluents. Multivariate statistical analysis suggested that dissolved trace metals in surface waters were probably derived from effluents/wadis but also from sediment resuspension processes, induced by natural (tides, hydrodynamics) or anthropogenic (dredging) events. Overall, this study highlights the importance of the interactions between sediment and water column for the trace metal dynamics in very shallow coastal environments with an exacerbated pattern for Cd.

Keywords :  trace metals; Gulf of Gabès; Mediterranean sea; sediment resuspension; environmental risk

 

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Lead (Pb) profiles in red coral skeletons as high resolution records of pollution in the Mediterranean Sea

 

Auteurs : Angèle Ricolleau, Nicole Floquet, Jean-Luc Devidal, Robert J.Bodnar, Jonathan Perrin, Joaquim Garrabou, Jean-Georges Harmelin, Federica Costantini, Joana R.Boavida (MIO), Daniel Vielzeu

Chemical Geology, Volume 525, 20 October 2019, Pages 112-124
Received 23 October 2017, Revised 28 June 2019, Accepted 3 July 2019, Available online 11 July 2019

Résumé : Lead (Pb) concentrations in long-lived Corallium species of known age, from the Mediterranean Sea, Atlantic and Pacific Oceans, were determined by laser ablation, inductively coupled plasma mass spectrometry (LA-ICPMS). Lead concentrations in a 2000-year-old sub-fossil Mediterranean C. rubrum are ca 0.09 ± 0.03 μg/g. For the period 1894–1955, lead concentrations in C. rubrum skeletons from the Mediterranean are stable within the range 0.2–0.4 μg/g; concentrations increase to about 1–1.2 μg/g during the period 1960–1978, then decrease progressively to stabilize and reach values in the range 0.2–0.4 μg/g in present-day corals. These variations can be related to the lead gasoline pollution event that (1) started in the early 1950s with the increase of the numbers of cars in the world, and (2) was mitigated by the implementation of new regulations starting in 1975, leading to a return to pre-1950 levels in 2000. In the Pacific, lead concentrations in C. japonicum and C. konojoi are lower than in the Mediterranean C. rubrum, with values close to 0.17 ± 0.03 μg/g. The lowest lead concentrations in present-day samples (0.11 μg/g) are found in C. johnsoni and C. niobe from the Azores islands in the Atlantic, and in a Mediterranean C. rubrum from Montecristo Island, one of the least accessible and most protected areas in the Mediterranean Sea. Using lead concentrations in C. rubrum and in the Mediterranean seawaters, a partition coefficient Kd = [Pb/Ca]calcite / [Pb/Ca]seawater of 13 ±3 is estimated; it allows calculating past and present lead contents in seawater in which corals grew. Application to Corallium species indicates that values endangering human health or threatening the preservation of aquatic ecosystem on long terms were nearly reached or exceeded in Mediterranean seawaters at the maximum of the lead gasoline pollution event in the 1980s. Measurements in C. rubrum from different places in the Mediterranean indicate that present-day seawater concentrations vary between 40 and 200 pmol/kg. As expected, the lowest concentrations come from protected areas insulated from human activities, while the highest come from places close to lead mining or processing sites.

 

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The Amazon River: A Major Source of Organic Plastic Additives to the Tropical North Atlantic ?

 

Auteurs : Natascha Schmidt (MIO), Vincent Fauvelle(MIO) , Anouck Ody (MIO), Javier Castro-Jiménez (MIO), Julien Jouanno, Thomas Changeux (MIO), Thierry Thibaut (MIO) and Richard Sempéré (MIO)

Environmental Science & Technology 2019 53 (13), 7513-7521
DOI: 10.1021/acs.est.9b01585

Résumé : The release of emerging organic contaminants is identified among the most critical hazards to the marine environment, and plastic additives have received growing attention due to their worldwide distribution and potential deleterious effects. Here, we report dissolved surface water concentrations of two important families of plastic additives (organophosphate esters (OPEs) and bisphenols) and other related organic compounds (perfluorinated chemicals) measured in the North Atlantic from Cape Verde to the West Indies. We found that OPEs were the most abundant contaminants, reaching remarkably high concentrations in open ocean waters (1200 km offshore of the American Coast, at the location of the Amazon river plume during the sampling period), with up to 1.3 μg L–1 (Σ9OPEs). A Lagrangian analysis confirmed that these high concentrations of contaminants originated from the Amazon River plume and were transported more than 3000 km by the North Brazil Current and its retroflection. We thus consider the Amazon River as a major source of organic contaminants of emerging concern to the tropical North Atlantic Ocean and suggest that medium-/long-range contaminant transport occurs, most certainly facilitated by the highly stratified conditions offered by the river plume.

 

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Identifying the Stoichiometry of Metal/Ligand Complex by Coupling Spectroscopy and Modelling: a Comprehensive Study on Two Fluorescent Molecules Specific to Lead

 

Auteurs : W René, M Arab, K Laatikainen, S Mounier (MIO), C Branger, V. Lenoble (MIO)

J Fluoresc (2019). https://doi.org/10.1007/s10895-019-02405-0 -Received : 10 May 2019 - Accepted 24 June 2019 - First Online : 13 July 2019

Résumé : Two new chemosensors for lead (II) were synthesized based on 5-((anthracen-9-ylmethylene) amino)quinolin-10-ol (ANQ). ANQ was modified in the para position of the imine group via a methoxy link either with methylmethacrylate (ANQ-MMA) or styrene (ANQ-ST). Complexation of those molecules with Pb2+ was studied at room temperature using UV-Visible absorption and fluorescence spectroscopies. Thanks to the UV-visible absorption spectroscopy, it appeared that ANQ-MMA formed 1:1 and 1:2 complexes with lead (II) and ANQ-ST only 1:1 complex. For both molecules, the fluorescence excitation-emission matrices (EEM) signal intensity increased from 0 to 100 μmol.L−1 of lead (II) followed by a saturation for higher concentrations. The decomposition of the obtained EEMs gave a set of empiric fluorescent components that have been directly linked to the distribution of lead complexes obtained with the UV-visible absorption spectroscopy study. This correlation allowed to evidence metal/ligand complex stoichiometry and emerge as a new method to identify empiric components. Moreover, the two ligands showed a promising selectivity for Pb2+, turning them interesting probes for this hazardous metal.

Keywords : Metal/ligand complex Spectroscopy Modelling Fluorescent molecules Lead

 

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Evaluation of the roles of metals and humic fractions in the podzolization of soils from the Amazon region using two analytical spectroscopy techniques

 

Auteurs : Amanda Tadini, Gustavo Nicolodelli, Bruno Marangoni, Stéphane Mounier (MIO),Celia Montes, Débora M.B.P. Milori

Microchemical Journal, Elsevier, 2019, 144,pp.454-460.

Résumé : Soil organic matter (SOM) plays an important role in environmental sustainability, since it is involved in carbon and nutrient cycling. Consequently, it is a key factor to consider in studies concerning global climate change and agronomy. Among the main components of SOM are humic substances (HS), which are divided, according to their solubility, into humic acid (HA), fulvic acid (FA), and humin (HU) fractions. Study of the chemical properties of this organic matter is important for understanding the biogeochemical processes occurring in the soil. The aim of this work was to determine the metals iron (Fe) and aluminum (Al), using flame atomic absorption spectrometry (FAAS) and laser-induced breakdown spectroscopy (LIBS), in order to elucidate the role of organic matter in the transport of these metals in Amazonian soils. The results showed that FA was important for Al, while the HA fraction was more selective towards Fe. The translocations of these metals to deeper profiles in two different soils involved either young and less humified organic matter, or older organic matter with a low degree of humification. Therefore, these two humic fractions were involved in the process of soil podzolization, with FA having a predominant role in the transport of Al, while HA was mainly responsible for the transport of Fe.

Keywords : LIBS, FAAS, Organic matter, Amazon

 

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Effects of catchment area and nutrient deposition regime on phytoplankton functionality in alpine lakes

 

Auteurs : Coralie Jacquemin, Céline Bertrand, Evelyne Franquet, Stéphane Mounier (MIO), Benjamin Misson (MIO), Benjamin Oursel (MIO), Laurent Cavalli

Science of The Total Environment - Volume 674, 15 July 2019, Pages 114-127

Résumé : High mountain lakes are a network of sentinels, sensitive to any events occurring within their waterbodies, their surrounding catchment and their airshed. In this paper, we investigate how catchments impact the taxonomic and functional composition of phytoplankton communities in high mountain lakes, and how this impact varies according to the atmospheric nutrient deposition regime. For two years, we sampled the post snow-melt and the late summer phytoplankton, with a set of biotic and abiotic parameters, in six French alpine lakes with differing catchments (size and vegetation cover) and contrasting nitrogen (N) and phosphorus (P) deposition regimes. Whatever the nutrient deposition regime, we found that the lakes with the smallest rocky catchments showed the lowest functional richness of phytoplankton communities. The lakes with larger vegetated catchments were characterized by the coexistence of phytoplankton taxa with more diverse strategies in the acquisition and utilization of nutrient resources. The nutrient deposition regime appeared to interact with catchment characteristics in determining which functional groups ultimately developed in lakes. Photoautotroph taxa dominated the phytoplankton assemblages under high NP deposition regime while mixotroph taxa were even more favored in lakes with large vegetated catchments under low NP deposition regime. Phytoplankton functional changes were likely related to the leaching of terrestrial organic matter from catchments evidenced by analyses of carbon (δ13C) and nitrogen (δ15N) stable isotope ratios in seston and zooplankton. Plankton δ15N values indicated greater water–soil interaction in lakes with larger vegetated catchments, while δ13C values indicated the effective mineralization of the organic matter in lakes. The role played by catchments should be considered when seeking to determine the vulnerability of high altitude lakes to future changes, as catchments' own properties will vary under changes related to climate and airborne contaminants.

 

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Hydrostatic Pressure Helps to Cultivate an Original Anaerobic Bacterium From the Atlantis Massif Subseafloor (IODP Expedition 357): Petrocella atlantisensis gen. nov. sp. nov.

 

Auteurs : Marianne Quéméneur (MIO), Gaël Erauso (MIO) , Eléonore Frouin (MIO) , Emna Zeghal (MIO),Céline Vandecasteele, Bernard Ollivier (MIO) , Christian Tamburini (MIO), Marc Garel (MIO),Bénédicte Ménez and Anne Postec (MIO)

Front. Microbiol., 16 July 2019 | https://doi.org/10.3389/fmicb.2019.01497

Résumé : Rock-hosted subseafloor habitats are very challenging for life, and current knowledge about microorganisms inhabiting such lithic environments is still limited. This study explored the cultivable microbial diversity in anaerobic enrichment cultures from cores recovered during the International Ocean Discovery Program (IODP) Expedition 357 from the Atlantis Massif (Mid-Atlantic Ridge, 30°N). 16S rRNA gene survey of enrichment cultures grown at 10–25°C and pH 8.5 showed that Firmicutes and Proteobacteria were generally dominant. However, cultivable microbial diversity significantly differed depending on incubation at atmospheric pressure (0.1 MPa), or hydrostatic pressures (HP) mimicking the in situ pressure conditions (8.2 or 14.0 MPa). An original, strictly anaerobic bacterium designated 70B-AT was isolated from core M0070C-3R1 (1150 meter below sea level; 3.5 m below seafloor) only from cultures performed at 14.0 MPa. This strain named Petrocella atlantisensis is a novel species of a new genus within the newly described family Vallitaleaceae (order Clostridiales, phylum Firmicutes). It is a mesophilic, moderately halotolerant and piezophilic chemoorganotroph, able to grow by fermentation of carbohydrates and proteinaceous compounds. Its 3.5 Mb genome contains numerous genes for ABC transporters of sugars and amino acids, and pathways for fermentation of mono- and di-saccharides and amino acids were identified. Genes encoding multimeric [FeFe] hydrogenases and a Rnf complex form the basis to explain hydrogen and energy production in strain 70B-AT. This study outlines the importance of using hydrostatic pressure in culture experiments for isolation and characterization of autochthonous piezophilic microorganisms from subseafloor rocks.

 

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Air‐Sea Turbulent Fluxes From a Wave‐Following Platform During Six Experiments at Sea

 

Auteurs : Denis Bourras (MIO), Rémi Cambra, Louis Marié, Marie‐Noëlle Bouin, Lucio Baggio, Hubert Branger, Houda Beghoura, Gilles Reverdin, Boris Dewitte, Aurélien Paulmier, Christophe Maes, Fabrice Ardhuin, Ivane Pairaud, Philippe Fraunié (MIO) , Christopher Luneau, Danièle Hauser

JGR Oceans - First published: 18 June 2019
https://doi.org/10.1029/2018JC014803

Résumé : Turbulent fluxes at the air‐sea interface are estimated with data collected in 2011 to 2017 with a low‐profile platform during six experiments in four regions. The observations were carried out with moderate winds (2–10 m/s) and averaged wave heights of 1.5 m. Most of the time, there was a swell, with an averaged wave age (the ratio between wave phase speed and wind speed) being equal to 2.8 ± 1.6. Three flux calculation methods are used, namely, the eddy covariance (EC), the inertial dissipation (ID), and the bulk methods. For the EC method, a spectral technique is proposed to correct wind data from platform motion. A mean bias affecting the friction velocity (u*) is then evaluated. The comparison between EC u* and ID u* estimates suggests that a constant imbalance term (ϕimb) equal to 0.4 is required in the ID method, possibly due to wave influence on our data. Overall, the confidence in the calculated u* estimates is found to be on the order of 10%. The values of the drag coefficient (CD) are in good agreement with the parameterizations of Smith (1988, https://doi.org/10.1029/JC093iC12p15467) in medium‐range winds and of Edson et al. (2013, https://doi.org/10.1175/JPO‐D‐12‐0173.1) in light winds. According to our data, the inverse wave age varies linearly with wind speed, as in Edson et al. (2013, https://doi.org/10.1175/JPO‐D‐12‐0173.1), but our estimates of the Charnock coefficient do not increase with wind speed, which is possibly related to sampling swell‐dominated seas. We find that the Stanton number is independent from wind speed.

 

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Christelle Desnues (MIO), co-auteur de "Global phylogeography and ancient evolution of the widespread human gut virus crAssphage"

 

Auteurs : Robert A. Edwards, Alejandro A. Vega, Holly M. Norman, Maria Ohaeri, Kyle Levi, Elizabeth A. Dinsdale, Ondrej Cinek, Ramy K. Aziz, Katelyn McNair, Jeremy J. Barr, Kyle Bibby, Stan J. J. Brouns, Adrian Cazares, Patrick A. de Jonge, Christelle Desnues (MIO), Samuel L. Díaz Muñoz, Peter C. Fineran, Alexander Kurilshikov, Rob Lavigne, Karla Mazankova, David T. McCarthy, Franklin L. Nobrega, Alejandro Reyes Muñoz, German Tapia, Nicole Trefault, Alexander V. Tyakht, Pablo Vinuesa, Jeroen Wagemans, Alexandra Zhernakova, Frank M. Aarestrup, Gunduz Ahmadov, Abeer Alassaf, Josefa Anton, Abigail Asangba, Emma K. Billings, Vito Adrian Cantu, Jane M. Carlton, Daniel Cazares, Gyu-Sung Cho, Tess Condeff, Pilar Cortés, Mike Cranfield, Daniel A. Cuevas, Rodrigo De la Iglesia, Przemyslaw Decewicz, Michael P. Doane, Nathaniel J. Dominy, Lukasz Dziewit, Bashir Mukhtar Elwasila, A. Murat Eren, Charles Franz, Jingyuan Fu, Cristina Garcia-Aljaro, Elodie Ghedin, Kristen M. Gulino, John M. Haggerty, Steven R. Head, Rene S. Hendriksen, Colin Hill, Heikki Hyöty, Elena N. Ilina, Mitchell T. Irwin, Thomas C. Jeffries, Juan Jofre, Randall E. Junge, Scott T. Kelley, Mohammadali Khan Mirzaei, Martin Kowalewski, Deepak Kumaresan, Steven R. Leigh, David Lipson, Eugenia S. Lisitsyna, Montserrat Llagostera, Julia M. Maritz, Linsey C. Marr, Angela McCann, Shahar Molshanski-Mor, Silvia Monteiro, Benjamin Moreira-Grez, Megan Morris, Lawrence Mugisha, Maite Muniesa, Horst Neve, Nam-phuong Nguyen, Olivia D. Nigro, Anders S. Nilsson, Taylor O’Connell, Rasha Odeh, Andrew Oliver, Mariana Piuri, Aaron J. Prussin II, Udi Qimron, Zhe-Xue Quan, Petra Rainetova, Adán Ramírez-Rojas, Raul Raya, Kim Reasor, Gillian A. O. Rice, Alessandro Rossi, Ricardo Santos, John Shimashita, Elyse N. Stachler, Lars C. Stene, Ronan Strain, Rebecca Stumpf, Pedro J. Torres, Alan Twaddle, MaryAnn Ugochi Ibekwe, Nicolás Villagra, Stephen Wandro, Bryan White, Andy Whiteley, Katrine L. Whiteson, Cisca Wijmenga, Maria M. Zambrano, Henrike Zschac

Nature Microbiology (2019)

Résumé : Microbiomes are vast communities of microorganisms and viruses that populate all natural ecosystems. Viruses have been considered to be the most variable component of microbiomes, as supported by virome surveys and examples of high genomic mosaicism. However, recent evidence suggests that the human gut virome is remarkably stable compared with that of other environments. Here, we investigate the origin, evolution and epidemiology of crAssphage, a widespread human gut virus. Through a global collaboration, we obtained DNA sequences of crAssphage from more than one-third of the world’s countries and showed that the phylogeography of crAssphage is locally clustered within countries, cities and individuals. We also found fully colinear crAssphage-like genomes in both Old-World and New-World primates, suggesting that the association of crAssphage with primates may be millions of years old. Finally, by exploiting a large cohort of more than 1,000 individuals, we tested whether crAssphage is associated with bacterial taxonomic groups of the gut microbiome, diverse human health parameters and a wide range of dietary factors. We identified strong correlations with different clades of bacteria that are related to Bacteroidetes and weak associations with several diet categories, but no significant association with health or disease. We conclude that crAssphage is a benign cosmopolitan virus that may have coevolved with the human lineage and is an integral part of the normal human gut virome.

 

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New Insights of the Sicily Channel and Southern Tyrrhenian Sea Variability

 

Auteurs : Menna, M.; Poulain, P.; Ciani, D.; Doglioli, A. (MIO); Notarstefano, G.; Gerin, R.; Rio, M.; Santoleri, R.; Gauci, A.; Drago, A.

Water 2019, 11(7), 1355; https://doi.org/10.3390/w11071355
Received: 31 May 2019 / Revised: 24 June 2019 / Accepted: 27 June 2019 / Published: 29 June 2019

Abstract : The dynamics of the Sicily Channel and the southern Tyrrhenian Sea are highly influenced by the seasonal variability of the Mediterranean basin-wide circulation, by the interannual variability of the numerous mesoscale structures present in the Channel, and by the decadal variability of the adjacent Ionian Sea. In the present study, all these aspects are investigated using in-situ (Lagrangian drifter trajectories and Argo float profiles) and satellite data (Absolute Dynamic Topography, Sea Level Anomaly, Sea Surface Temperature, wind products) over the period from 1993 to 2018. The availability of long time series of data and high-resolution multi-sensor surface currents allow us to add new details on the circulation features and on their driving mechanisms and to detect new permanent eddies not yet described in literature. The structures prevailing in winter are mainly driven by wind, whereas those prevailing in summer are regulated by topographical forcing on surface currents. The strength of the surface structures located at the western entrance of the Ionian Sea and of the mesoscale activity along the northern Sicily coast is modulated by the large-scale internal variability. The vertical hydrological characteristics of these mesoscale eddies are delineated using the Argo float profiles inside these structures.

 

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Accounting for ocean connectivity and hydroclimate in fish recruitment fluctuations within transboundary metapopulations

 

Auteurs : Manuel Hidalgo, Vincent Rossi (MIO), Pedro Monroy, Enrico Ser‐Giacomi, Emilio Hernández‐García, Beatriz Guijarro, Enric Massutí, Francisco Alemany, Angelique Jadaud, José Luis Perez, Patricia Reglero

ESA
First published: 30 May 2019
https://doi.org/10.1002/eap.1913

Résumé : Marine resources stewardships are progressively becoming more receptive to an effective incorporation of both ecosystem and environmental complexities into the analytical frameworks of fisheries assessment. Understanding and predicting marine fish production for spatially and demographically complex populations in changing environmental conditions is however still a difficult task. Indeed, fisheries assessment is mostly based on deterministic models that lack realistic parameterizations of the intricate biological and physical processes shaping recruitment, a cornerstone in population dynamics. We use here a large metapopulation of a harvested fish, the European hake (Merluccius merluccius), managed across transnational boundaries in the northwestern Mediterranean, to model fish recruitment dynamics in terms of physics‐dependent drivers related to dispersal and survival. The connectivity among nearby subpopulations is evaluated by simulating multi‐annual Lagrangian indices of larval retention, imports, and self‐recruitment. Along with a proxy of the regional hydroclimate influencing early life stages survival, we then statistically determine the relative contribution of dispersal and hydroclimate for recruitment across contiguous management units. We show that inter‐annual variability of recruitment is well reproduced by hydroclimatic influences and synthetic connectivity estimates. Self‐recruitment (i.e., the ratio of retained locally produced larvae to the total number of incoming larvae) is the most powerful metric as it integrates the roles of retained local recruits and immigrants from surrounding subpopulations and is able to capture circulation patterns affecting recruitment at the scale of management units. We also reveal that the climatic impact on recruitment is spatially structured at regional scale due to contrasting biophysical processes not related to dispersal. Self‐recruitment calculated for each management unit explains between 19% and 32.9% of the variance of recruitment variability, that is much larger than the one explained by spawning stock biomass alone, supporting an increase of consideration of connectivity processes into stocks assessment. By acknowledging the structural and ecological complexity of marine populations, this study provides the scientific basis to link spatial management and temporal assessment within large marine metapopulations. Our results suggest that fisheries management could be improved by combining information of physical oceanography (from observing systems and operational models), opening new opportunities such as the development of short‐term projections and dynamic spatial management.

 

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Implementation of an end-to-end model of the Gulf of Lions ecosystem (NW Mediterranean Sea). II. Investigating the effects of high trophic levels on nutrients and plankton dynamics and associated feedbacks

 

Auteurs : Frédéric Diaz (MIO), Daniela Bănaru (MIO ), Philippe Verley , Yunne JaiShin

Ecological Modelling - Volume 405, 1 August 2019, Pages 51-68
https://doi.org/10.1016/j.ecolmodel.2019.05.004

Résumé : The end-to-end OSMOSE-GoL model parameterized, calibrated and evaluated for the Gulf of Lions ecosystem (Northwestern Mediterranean Sea) has been used to investigate the effects of introducing two-ways coupling between the dynamics of Low and High Trophic Level groups.

The use of a fully dynamic two-ways coupling between the models of Low and High Trophic Levels organisms provided some insights in the functioning of the food web in the Gulf of Lions. On the whole microphytoplankton and mesozooplankton were found to be preyed upon by High Trophic Levels planktivorous groups at rates lower than 20% and 30% of their respective natural mortality rates, but these relatively low rates involved some important alterations in the infra-seasonal and annual cycles of both High and Low Trophic Levels groups. They induced significant changes in biomass, fisheries landings and food web interactions by cascading effects. Spatial differential impacts of High Trophic Levels predation on plankton are less clear except in areas in which primary productivity is high. Higher predation rates on plankton groups were encountered within the area of the Rhone river’s influence and in areas associated to the presence of mesoscale eddies in the Northwestern part of the Gulf of Lions, especially. Generally, the pressure of the High Trophic Levels predation was the highest in areas of highest biomass whatever the plankton group considered.

The two-ways coupling between Low and High Trophic Levels models revealed both bottom-up and top-down controls in the ecosystem with effects on planktivorous species similar to those observed in the field. The use of the end-to-end model enabled to propose a set of potential mechanisms that may explain the observed decrease in small pelagic catches by the French Mediterranean artisanal fisheries over the last decade.

 

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Macro-litter in surface waters from the Rhone River: Plastic pollution and loading to the NW Mediterranean Sea

 

Auteurs : Javier Castro-Jiménez (MIO), Daniel González,Fernández, Michel Fornier (MIO), Natascha Schmidt (MIO ), Richard Sempéré (MIO)

Marine Pollution Bulletin

Volume 146, September 2019, Pages 60-66
https://doi.org/10.1016/j.marpolbul.2019.05.067

Résumé : We present here the first estimates of floating macro-litter in surface waters from the Rhone River, based on monthly visual observations during 1-year period (2016–2017). Plastic represented 77% of the identified items, confirming its predominance in riverine floating litter. Fragments (2.5–50 cm) and Single Use Plastics (i.e. bags, bottles and cover/packaging) were among the most abundant items. Frequent non-plastic floating litter were paper items such as packaging material and newspapers, and metal items (mostly cans), representing 14% and 5% of total litter, respectively. A lower-end estimate resulted in ∼223,000 plastic items (∼0.7 t of plastic) transported annually by the Rhone surface waters to the Gulf of Lion (NW Mediterranean Sea). Floating macro-plastics are only a fraction of the total plastic export by the Rhone. Our study highlights the current discrepancy between field observations and theoretical estimations. Improvements are needed to harmonize data collection methodologies for field studies and model validation.

Graphical abstract

 

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Production of Current by Syntrophy Between Exoelectrogenic and Fermentative Hyperthermophilic Microorganisms in Heterotrophic Biofilm from a Deep-Sea Hydrothermal Chimney

 

Auteurs : Guillaume Pillot (MIO) , Sylvain Davidson (MIO) ,Richard Auria (MIO), Yannick Combet-Blanc (MIO); Anne Godfroy, Pierre-Pol Liebgott (MIO)

Environmental Microbiology
First Online: 11 May 2019

Résumé : To study the role of exoelectrogens within the trophic network of deep-sea hydrothermal vents, we performed successive subcultures of a hyperthermophilic community from a hydrothermal chimney sample on a mix of electron donors in a microbial fuel cell system. Electrode (the electron acceptor) was swapped every week to enable fresh development from spent media as inoculum. The MFC at 80 °C yielded maximum current production increasing from 159 to 247 mA m−2 over the subcultures. The experiments demonstrated direct production of electric current from acetate, pyruvate, and H2 and indirect production from yeast extract and peptone through the production of H2 and acetate from fermentation. The microorganisms found in on-electrode communities were mainly affiliated to exoelectrogenic Archaeoglobales and Thermococcales species, whereas in liquid media, the communities were mainly affiliated to fermentative Bacillales and Thermococcales species. The work shows interactions between fermentative microorganisms degrading complex organic matter into fermentation products that are then used by exoelectrogenic microorganisms oxidizing these reduced compounds while respiring on a conductive support. The results confirmed that with carbon cycling, the syntrophic relations between fermentative microorganisms and exoelectrogens could enable some microbes to survive as biofilm in extremely unstable conditions.

 


Graphical Abstract

Schematic representation of cross-feeding between fermentative and exoelectrogenic microbes on the surface of the conductive support. B, Bacillus/Geobacillus spp.; Tc, Thermococcales; Gg, Geoglobus spp.; Py, pyruvate; Ac, acetate.

 

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Amino acids promote black carbon aggregation and microbial colonization in coastal waters off Vietnam

 

Auteurs : Mar Benavides (MIO) Thuoc Chu Van, Xavier Mari (MIO)

Science of The Total Environment - Volume 685, 1 October 2019, Pages 527-532
https://doi.org/10.1016/j.scitotenv.2019.05.141

Résumé : The combustion of fossil fuels and biomass produces pyrogenic organic matter usually known as ‘black carbon’ (BC), which are transported across the atmosphere as particulate aerosol, eventually deposited on land and oceans. Soil studies have investigated the potential microbial colonization and remineralization of BC particles, but this process has been seldom studied in marine waters. BC provides a significant input of organic carbon to the oceans, yet its fate and role in biogeochemical cycling remains unknown. Here we explored the microbial colonization of BC particles in coastal seawater samples collected in Halong Bay (northern Vietnam). Using high-resolution mass spectrometry and microscopy methods, we observed an increasing colonization of BC particles by marine microbes in the presence of amino acids. Our results suggest that natural organic matter (NOM) present in seawater may promote the microbial colonization and eventual remineralization of BC particles. Future experiments should explore the potential microbial remineralization of BC particles to unveil the role of this massive source of carbon to marine ecosystems.

 

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Impact of sterilization methods on dissolved trace metals concentrations in complex natural samples: Optimization of UV irradiation

 

Auteurs : Sandrine Chifflet (MIO), Marianne Quéméneur (MIO), Aude Barani (MIO), Bernard Angeletti, Morgane Didry  (MIO) Gérald Grégori (MO) NathaliePradel (MIO)

MethodsX Volume 6, 2019, Pages 1133-1146
Received 12 March 2019, Accepted 18 April 2019, Available online 22 April 2019.

Résumé : Sterilization is essential for discriminating biotic responses from abiotic reactions in laboratory experiments investigating biogeochemical processes of complex natural samples. However, the conventional methods used to effectively sterilize materials or culture media do not allow sterilizing complex natural samples while maintaining biogeochemical balances. The aim of this study was to develop a low-cost and easy-to-use method to obtain geochemically unmodified and sterilized samples from complex lacustrine or coastal marine ecosystems. In preliminary assays, the impact of several sterilization methods (autoclaving, chemical poisoning, microwave, UV irradiation) on the trace metals balances was studied using borosilicate glass (BG), fluorinated ethylene-propylene (FEP) or polyethylene terephthalate (PET) bottles. Unlike other methods, UV sterilization had minor effects on the distribution of dissolved trace metals. Additional tests using complex lacustrine and coastal marine samples under 10 g/L sediments were performed using a homemade UV sterilization chamber designed to simultaneously irradiate a large number samples. Results showed:

• very reproducible UV tests in BG and FEP bottles
• faster sterilization using FEP bottles than using BG bottles
• low variations of dissolved trace metals concentrations, except for Al, Cu, Fe and Zn

 

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Vertical Motions and Their Effects on a Biogeochemical Tracer in a Cyclonic Structure Finely Observed in the Ligurian Sea

 

Auteurs : Rousselet L. (MIO), Doglioli AM (MIO)., de Verneil, A., Pietri, A., Della Penna, A., Berline, L.(MIO). , Marrec, P., Gregori, G (MIO), Thyssen, M.(MIO), Carlotti, F.(MIO), Barillon, S.(MIO), Simon-Bot, F.(MIO), Bonal, M., d'Ovidio, F. and Petrenko, A.A. (MIO), (2019)

JGR Oceans : First published: 23 April 2019
https://doi.org/10.1029/2018JC014392

Résumé : Vertical velocities can be estimated indirectly from in situ observations by theoretical frameworks like the ω‐equation. Direct measures of vertical exchanges are challenging due to their typically ephemeral spatiotemporal scales. In this study we address this problem with an adaptive sampling strategy coupling various biophysical instruments. We analyze the 3‐D organization of a cyclonic mesoscale structure finely sampled during the Observing Submesoscale Coupling At High Resolution cruise in the Ligurian Sea during fall 2015. The observations, acquired with a moving vessel profiler, highlight a subsurface low‐salinity layer (≃50 m), as well as rising isopycnals, generated by geostrophic cyclonic circulation, in the structure's center. Reconstructed 3‐D fields of density and horizontal velocities are used to estimate the vertical velocity field down to 250 m by applying the adiabatic QG ω‐equation, for the first time in this region. The vertical motions are characterized by multipolar patterns of downward and upward velocities on the edges of the structure and significantly smaller vertical velocities in its center. Both the 3‐D distribution of particles (size ≥100 μm), measured with a laser optical plankton counter, and the Synechococcus and Prochlorococcus abundances (cell per cubic meter) measured by flow cytometry are consistent with the 3‐D velocity field. In particular, a secondary vertical recirculation is identified that upwells particles (from 250 to 100 m) along isohalines to the structure's center. Besides demonstrating the effect of vertical patterns on biogeochemical distributions, this case study suggests to use particle matter as a tracer to assess physical dynamics.

 

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Frontiers in Fine-Scale in situ Studies: Opportunities During the SWOT Fast Sampling Phase

 

Auteurs : D’Ovidio F, Pascual A, Wang J, Doglioli AM (MIO), Jing Z, Moreau S, Grégori G (MIO), Swart S, Speich S, Cyr F, Legresy B, Chao Y, Fu L and Morrow RA (2019)

Front. Mar. Sci., 30 April 2019 | https://doi.org/10.3389/fmars.2019.00168

Résumé : Conceived as a major new tool for climate studies, the Surface Water and Ocean Topography (SWOT) satellite mission will launch in late 2021 and will retrieve the dynamics of the oceans upper layer at an unprecedented resolution of a few kilometers. During the calibration and validation (CalVal) phase in 2022, the satellite will be in a 1-day-repeat fast sampling orbit with enhanced temporal resolution, sacrificing the spatial coverage. This is an ideal opportunity – unique for many years to come – to coordinate in situ experiments during the same period for a focused study of fine scale dynamics and their broader roles in the Earth system. Key questions to be addressed include the role of fine scales on the ocean energy budget, the connection between their surface and internal dynamics, their impact on plankton diversity, and their biophysical dynamics at the ice margin.

 

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Liquid chromatographic isolation of individual carbohydrates from environmental matrices for stable carbon analysis and radiocarbon dating

 

Auteurs : Amel Nouara (MIO), Christos Panagiotopoulos (MIO), Jérôme Balesdent, Kalliopi Violaki (MIO), Edouard Bard, Yoann Fagault, Daniel James Repeta, Richard Sempéré (MIO)

Analytica Chimica Acta - Volume 1067, 27 August 2019, Pages 137-146

Résumé : Carbohydrates are among the most abundant organic molecules in both aquatic and terrestrial ecosystems; however, very few studies have addressed their isotopic signature using compound-specific isotope analysis, which provides additional information on their origin (δ13C) and fate (Δ14C). In this study, semi-preparative liquid chromatography with refractive index detection (HPLC-RI) was employed to produce pure carbohydrate targets for subsequent offline δ13C and Δ14C isotopic analysis. δ13C analysis was performed by elemental analyzer-isotope ratio mass spectrometer (EA-IRMS) whereas Δ14C analysis was performed by an innovative measurement procedure based on the direct combustion of the isolated fractions using an elemental analyzer coupled to the gas source of a mini carbon dating system (AixMICADAS). In general, four successive purifications with Na+, Ca2+, Pb2+, and Ca2+ cation-exchange columns were sufficient to produce pure carbohydrates. These carbohydrates were subsequently identified using mass spectrometry by comparing their mass spectra with those of authentic standards.

The applicability of the proposed method was tested on two different environmental samples comprising marine particulate organic matter (POM) and total suspended atmospheric particles (TSP). The obtained results revealed that for the marine POM sample, the δ13C values of the individual carbohydrates ranged from −18.5 to −16.8‰, except for levoglucosan and mannosan, which presented values of −27.2 and −26.2‰, respectively. For the TSP sample, the δ13C values ranged from −26.4 to −25.0‰. The galactose and glucose Δ14C values were 19 and 43‰, respectively, for the POM sample. On the other hand, the levoglucosan radiocarbon value was 33‰ for the TSP sample. These results suggest that these carbohydrates exhibit a modern age in both of these samples. Radiocarbon HPLC collection window blanks, measured after the addition of phthalic acid (14C free blank), ranged from −988 to −986‰ for the abovementioned compounds, indicating a very small background isotopic influence from the whole purification procedure. Overall, the proposed method does not require derivatization steps, produces extremely low blanks, and may be applied to different types of environmental samples.

 

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Out of the Mediterranean? Post‐glacial colonization pathways varied among cold‐water coral species

 

Auteurs : Joana Boavida (MIO), Ronan Becheler, Marvin Choquet, Norbert Frank, Marco Taviani, Jean‐François Bourillet, Anne‐Leila Meistertzheim, Anthony Grehan, Alessandra Savini, Sophie Arnaud‐Haond

Journal of Biogeography. 2019;1–17 - https://doi.org/10.1111/jbi.13570

Résumé :

Aim: To infer cold‐water corals’ (CWC) post‐glacial phylogeography and assess the role of Mediterranean Sea glacial refugia as origins for the recolonization of the northeastern Atlantic Ocean.

Location: Northeastern Atlantic Ocean and Mediterranean Sea.

Taxon: Lophelia pertusa, Madrepora oculata.

Methods: We sampled CWC using remotely operated vehicles and one sediment core for coral and sediment dating. We characterized spatial genetic patterns (microsatellites and a nuclear gene fragment) using networks, clustering and measures of genetic differentiation.

Results: Inferences from microsatellite and sequence data were congruent, and showed a contrast between the two CWC species. Populations of L. pertusa present a dominant pioneer haplotype, local haplotype radiations and a majority of endemic variation in lower latitudes. Madrepora oculata populations are differentiated across the northeastern Atlantic and genetic lineages are poorly admixed even among neighbouring sites.

Conclusions: Our study shows contrasting post‐glacial colonization pathways for two key habitat‐forming species in the deep sea. The CWC L. pertusa has likely undertaken a long‐range (post‐glacial) recolonization of the northeastern Atlantic directly from refugia located along southern Europe (Mediterranean Sea or Gulf of Cadiz). In contrast, the stronger genetic differentiation of M. oculata populations mirrors the effects of long‐term isolation in multiple refugia. We suggest that the distinct and genetically divergent, refugial populations initiated the post‐glacial recolonization of the northeastern Atlantic margins, leading to a secondary contact in the northern range and reaching higher latitudes much later, in the late Holocene. This study highlights the need to disentangle the influences of present‐day dispersal and evolutionary processes on the distribution of genetic polymorphisms, to unravel the influence of past and future environmental changes on the connectivity of cosmopolitan deep‐sea ecosystems associated with CWC.

 

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Pressure-Retaining Sampler and High-Pressure Systems to Study Deep-Sea Microbes Under in situ Conditions

 

Auteurs : Marc Garel (MIO), Patricia Bonin (MIO), Séverine Martini, Sophie Guasco (MIO), Marie Roumagnac (MIO), Nagib Bhairy (MIO), Fabrice Armougom (MIO) and Christian Tamburini (MIO)

Front. Microbiol., 09 April 2019 | https://doi.org/10.3389/fmicb.2019.00453

Résumé : The pelagic realm of the dark ocean is characterized by high hydrostatic pressure, low temperature, high-inorganic nutrients, and low organic carbon concentrations. Measurements of metabolic activities of bathypelagic bacteria are often underestimated due to the technological limitations in recovering samples and maintaining them under in situ environmental conditions. Moreover, most of the pressure-retaining samplers, developed by a number of different labs, able to maintain seawater samples at in situ pressure during recovery have remained at the prototype stage, and therefore not available to the scientific community. In this paper, we will describe a ready-to-use pressure-retaining sampler, which can be adapted to use on a CTD-carousel sampler. As well as being able to recover samples under in situ high pressure (up to 60 MPa) we propose a sample processing in equi-pressure mode. Using a piloted pressure generator, we present how to perform sub-sampling and transfer of samples in equi-pressure mode to obtain replicates and perform hyperbaric experiments safely and efficiently (with <2% pressure variability). As proof of concept, we describe a field application (prokaryotic activity measurements and incubation experiment) with samples collected at 3,000m-depth in the Mediterranean Sea. Sampling, sub-sampling, transfer, and incubations were performed under in situ high pressure conditions and compared to those performed following decompression and incubation at atmospheric pressure. Three successive incubations were made for each condition using direct dissolved-oxygen concentration measurements to determine the incubation times. Subsamples were collected at the end of each incubation to monitor the prokaryotic diversity, using 16S-rDNA/rRNA high-throughput sequencing. Our results demonstrated that oxygen consumption by prokaryotes is always higher under in situ conditions than after decompression and incubation at atmospheric pressure. In addition, over time, the variations in the prokaryotic community composition and structure are seen to be driven by the different experimental conditions. Finally, within samples maintained under in situ high pressure conditions, the active (16S rRNA) prokaryotic community was dominated by sequences affiliated with rare families containing piezophilic isolates, such as Oceanospirillaceae or Colwelliaceae. These results demonstrate the biological importance of maintaining in situ conditions during and after sampling in deep-sea environments.

 

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Biogeochemical Impacts of a Black Carbon Wet Deposition Event in Halong Bay, Vietnam

 

Auteurs : Xavier Mari (MIO), Benjamin Guinot, Chu Van Thuoc, Justine Brune, Jean-Pierre Lefebvre, Pradeep Ram Angia Sriram, Patrick Raimbault (MIO), Thorsten Dittmar and Jutta Niggemann

Front. Mar. Sci. (2019) DOI: 10.3389/fmars.2019.00185

Résumé : Black carbon (BC) is emitted to the atmosphere during biomass, biofuel, and fossil fuel combustion, and leaves the atmosphere via dry or wet deposition on land and on the ocean. On a global scale, wet deposition accounts for about 80% of the total atmospheric BC inputs to the ocean. The input of BC particles to the ocean can enrich surface waters with carbon and associated elements, and owing to high porosity and surface-active properties, BC can alter biogeochemical cycles by sorbing dissolved compounds and promoting aggregation. The rain-mediated input of BC to the ocean and its consequences on nutrient concentrations and particle dynamics were studied in Halong Bay, Vietnam, during a 24-h cycle impacted by short and heavy rainfall events. This study suggests that once introduced in the surface ocean via wet deposition, BC sorbs dissolved organic matter (DOM) and stimulates aggregation processes. The observed wet deposition events were characterized by sudden and pulsed inputs of BC particles that created a thin layer of sinking surface-active aggregates, acting as a net-like scavenger for DOM, nutrients (especially phosphate), and small particles. In addition, the wet deposition events coincided with an enrichment of nutrients in the surface microlayer, with an excess input of nitrogen relative to phosphorus leading to an increase of the molar N:P ratio from 24:1 to 37:1. In the underlying water, the molar N:P ratio also increased (i.e., from 39:1 to 64:1), and this can be attributed to the preferential scavenging of dissolved P-compounds on sinking BC-aggregates.

 

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A Novel Highly Efficient Device for Growing Micro-Aerophilic Microorganisms

Auteurs : Maxime Fuduche (MIO), Sylvain Davidson (MIO), Céline Boileau (MIO), Long-Fei Wu and Yannick Combet-Blanc (MIO)

Front. Microbiol., 19 March 2019 | https://doi.org/10.3389/fmicb.2019.00534

Résumé : This work describes a novel, simple and cost-effective culture system, named the Micro-Oxygenated Culture Device (MOCD), designed to grow microorganisms under particularly challenging oxygenation conditions. Two microaerophilic magnetotactic bacteria, a freshwater Magnetospirillum gryphiswaldense strain MSR-1 and a marine Magnetospira sp. strain QH-2, were used as biological models to prove the efficiency of the MOCD and to evaluate its specifications. Using the MOCD, growth rates of MSR-1 and QH-2 increased by four and twofold, respectively, when compared to traditional growing techniques using simple bottles. Oxystat-bioreactors have been typically used and specifically designed to control low dissolved oxygen concentrations, however, the MOCD, which is far less sophisticated was proven to be as efficient for both MSR-1 and QH-2 cultures with regard to growth rate, and even better for MSR-1 when looking at cell yield (70% increase). The MOCD enables a wide range of oxygenation conditions to be studied, including different O2-gradients. This makes it an innovative and ingenious culture device that opens up new parameters for growing microaerobic microorganisms.

 

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Implementation of an end-to-end model of the Gulf of Lions ecosystem (NW Mediterranean Sea). I. Parameterization, calibration and evaluation

 

Auteurs : Daniela Bănaru (MIO), Fréderic Diaz (MIO), Philippe Verley, Rose Campbell, Jonathan Navarro (MIO), ChristopheYohia (MIO), Ricardo Oliveros-Ramos, Capucine Mellon-Duval, Yunne-Jai Shin

Ecological Modelling : Volume 401, 1 June 2019, Pages 1-19

Résumé : An end-to-end model named OSMOSE-GoL has been built for the Gulf of Lions, the main French Mediterranean fishing area. This spatialized dynamic model links the coupled hydrodynamic and biogeochemical model Eco3M-S/SYMPHONIE (LTL – low trophic level model) to OSMOSE (HTL – high trophic level model). It includes 15 compartments of living organisms, five from the LTL model (i.e. nanophytoplankton, microphytoplankton, nanozooplankton, microzooplankton and mesozooplankton) and ten from the HTL model (northern krill, southern shortfin squid, European pilchard, European anchovy, European sprat, Atlantic horse mackerel, Atlantic mackerel, blue whiting, European hake and Atlantic bluefin tuna). With the exception of northern krill and European sprat, all HTL species are commercially exploited and undergo fisheries mortality pressure. The modeled species represent more than 70% of annual catches in this area. This paper presents the parameterization, calibration and evaluation of this model with satellite data for phytoplankton and with biomass, landings, diet and trophic level data for HTL groups. For most species, the diets in output of OSMOSE-GoL are similar to field and literature data in terms of dominant prey groups and species. However, some differences were observed. Various reasons may explain the mismatch between the modeled diet and field data. Benthic prey sometimes observed in the stomach content of the HTL predators were not modeled in OSMOSE-GoL. Field studies were carried out at specific periods and locations, while our data concern the period 2001–2004 and the entire modeled domain. Inter- and intra-annual variations in spatial distribution and density of prey may also explain these differences. The model estimates trophic level values similar to those cited in the literature for all the HTL compartments. These values are also close to the trophic levels estimated by a previous Ecopath model for the same area and period. Even though some improvements are still possible, this model may already be of use to explore fishery or Marine Protected Areas scenarios for socio-ecosystem management issues.

 

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The ups and downs of a canopyforming seaweed over a span of more than one century

 

Auteurs : Aurélie Blanfuné, Charles François Boudouresque, Marc Verlaque & Thierry Thibaut (tous du MIO)

Scientific Reportsvolume 9, Article number: 5250 (2019)

Résumé : Canopy-forming seaweeds constitute marine forests that deliver ecosystem services. The worldwide range shift, sharp decline or loss of many of these forests, caused by the cumulative impact of increasing human pressure and climate change, have been widely documented. Contrasting examples, reflecting higher than expected resilience, have been more rarely reported. Here, we took the opportunity of having at our disposal a two-century suite of documents (herbarium vouchers, articles) and a ~120-year observation period, dealing with a long-lived brown seaweed, Cystoseira mediterranea, along a well-explored Mediterranean coastline in the Gulf of Lions, to depict the fate of its populations. In addition, we provided baselines for future surveys, with a high degree of accuracy. The northernmost population, scattered on rare suitable substrates, gradually declined and has been extinct since the 1980s. The length of shore occupied by the southern population showed a long-term decline trend, with two sharp minima followed by partial recovery. The causes of the decline differ between sites and periods: coastal development, pollution, competition with mussels, heatwaves and exceptional storms. Overall, the Gulf of Lions populations reflects long-lasting resilience, higher than expected, and a health status that is better than that reported for many other canopy-forming seaweeds.

 

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A Glider-Compatible Optical Sensor for the Detection of Polycyclic Aromatic Hydrocarbons in the Marine Environment

 

Auteurs : Frédéric Cyr, Marc Tedetti (MIO), Florent Besson, Nagib Bhairy (MIO) and Madeleine Goutx (MIO)

Front. Mar. Sci., 18 March 2019 | https://doi.org/10.3389/fmars.2019.00110

Résumé : Cette étude présente le MiniFluo-UV, un capteur de fluorescence compatible avec les planeurs océaniques, qui cible la détection des hydrocarbures aromatiques polycycliques (HAP) dans le milieu marin. Deux MiniFluos peuvent être installés sur un planeur, chacun équipé de deux canaux optiques (un HAP est mesuré par canal). Cette configuration permet de mesurer jusqu'à 4 HAP fluorescents différents : le naphtalène, le phénanthrène, le fluorène et le pyrène. Des tests en laboratoire sur les produits pétroliers (pétrole brut et diesel Maya) ainsi que sur des échantillons marins situés à proximité de zones industrielles (ports urbains et installations offshore) ont révélé que la concentration des quatre HAP ciblés représentait entre 62% et 97% de la concentration totale d'HAP détectée en échantillons (HAP P16 déterminés par des protocoles internationaux standard). Les tests de laboratoire ont également révélé que, pour les applications marines, l’étalonnage de la fraction de pétrole brut adaptée à l’eau (WAF) est plus approprié que celui des étalons purs (STD). En effet, la fluorescence des HAP est constituée en grande partie de composés alkylés qui ne sont pas pris en compte avec l’étalonnage STD. Les résultats de trois déploiements de planeurs dans des niveaux de complexité croissants (un essai en laboratoire, une admission sur le terrain en mode non autonome et une mission totalement autonome) sont également présentés. Au cours des déploiements sur le terrain, l’ensemble MiniFluo-planeur « SeaExplorer » a pu détecter des gradients de concentration des eaux marines au large d’un port méditerranéen (<80ngL−1) ainsi que des zones d’hydrocarbures dans les eaux de surface d’un champ d’exploitation pétrolière en Mer du Nord (<200ngL−1, principalement du naphtalène).

 

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Biochemical composition and energy content of size-fractionated zooplankton east of the Kerguelen Islands

 

Auteurs : Mireille Harmelin-Vivien (MIO), Daniela Bӑnaru (MIO) , Charlotte Dromard, Melanie Ourgaud (MIO), François Carlotti (MIO)

Polar Biology, Springer Verlag, 2019, 42 (3), pp.603-617. 10.1007/s00300-019-02458-8

Résumé : Food quality is recognized as a key parameter of food web functioning in which zooplankton plays a crucial role not only in linking lower to upper trophic levels but also in transforming the quality of the organic matter available to predators. The influence of size and taxonomic group composition of zooplankton in these processes was assessed in eastern Kerguelen waters (Southern Ocean) at the onset of the spring bloom in 2011. Biochemical (lipids, proteins and carbohydrates) and elemental (carbon and nitrogen) composition were measured in five size—fractions of bulk zooplankton ranging from 80 µm to > 2000 µm and in large copepods, euphausiids, annelids and salps, and energy content was derived from biochemical contents. Proteins were the dominant component of zooplankton dry weight (21.5% dw), followed by lipids (8.9% dw), soluble carbohydrates (2.2% dw) and insoluble carbohydrates (1.0% dw). A concentration increase with zooplankton size for all biochemical components was observed, particularly stronger for proteins and lipids. Copepods and salps provided, respectively, the highest and the lowest amount of lipids and energy.  A four-fold increase in energy content was observed from the smallest to the largest fraction inducing a significant ncrease (> 10 kJ g dw) in the quality of zooplankton matter. This may explain why large zooplankton represent a major food resource for numerous fish, seabirds and marine mammals in the Southern Ocean. Such unique results are required to better quantify energy dynamics in polar food webs.

 

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Evidence of high N2 fixation rates in the temperate northeast Atlantic

 

Auteurs : Debany Fonseca-Batista, Xuefeng Li, Virginie Riou (MIO), Valérie Michotey(MIO), Florian Deman1, François Fripiat5, Sophie Guasco (MIO), Natacha Brion, Nolwenn Lemaitre, Manon Tonnard, Morgane Gallinari6, Hélène Planquette, Frédéric Planchon, Géraldine Sarthou, Marc Elskens, Julie LaRoche, Lei Chou, Frank Dehairs

Biogeosciences, 16, 999–1017, 2019 - https://doi.org/10.5194/bg-16-999-2019

Résumé : Diazotrophic activity and primary production (PP) were investigated along two transects (Belgica BG2014/14 and GEOVIDE cruises) off the western Iberian Margin and the Bay of Biscay in May 2014. We report substantial N2fixation activitiesat 8 of the 10 stations sampled, ranging overallbetween 81 and 384 μmol N m-2d-1(0.7 to 8.2 nmol N L-1d-1),withtwo sites close to the Iberian Margin between 38.8° N and 40.7° N yieldingrates 25reachingup to 1355 and 1533 μmol N m-2d-1(65 and 45 nmol N L-1d-1at surface level, respectively).Although diazotrophic activity was not detected at two northern stations in the central Bay of Biscay, when converted to carbon uptake using Redfield stoichiometry, N2fixation at the eight other sites generally contributed to 1–3% of euphotic layer daily PP, and up to 25% and 23%, respectively at the two most active sites. In the Atlantic Ocean, N2fixation rates exceeding 1000 μmol N m-2d-1have previously only been reported in the temperate and tropical western North 30Atlantic waters having coastal, shelf or mesohaline characteristics, as opposed to the mostly open ocean conditions studied here.At the two sites where N2fixation activity wasthe highest; nifHsequences assigned to theprymnesiophyte-symbiont CandidatusAtelocyanobacterium thalassa (UCYN-A)dominated the nifH sequence pool recovered from DNA samples, whilethe remaining sequences, as for all the ones recovered from the other sites,belonged exclusively to non-cyanobacterialphylotypes. Previous studies in the Iberian Basin have systematically 35reported lower N2fixation rates (from < 0.1 to 140 μmol N m-2d-1), as compared to those found in the presentstudy, and this regardless of whether the bubble-addition method or the dissolution method were applied. Earlier studiesin the Iberian region wereconductedlargely outside the bloom period,unlike the present work which was carried out in spring, yet in all cases the assessment of nifHgene diversity, suggests a predominance of UCYN-A and non-cyanobacterial diazotrophs. We support that the unexpectedly high N2fixation activitiesrecorded at the time of our 40study werepromoted by the availability of phytoplankton-derived organic matter produced during the spring bloom, as evidencedby the significant surface particulate organic carbon concentrations,andby the presence of excess phosphorus signature in surface waters, particularly atthe sites with extreme activities. Our findings stress the need2for a more detailed monitoring of oceanic N2fixation in productive waters of the temperate North Atlantic to better constrain the basin-scale nitrogen input to the ocean inventory.

 

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Bacterial Bioluminescence: Light Emission in Photobacterium phosphoreum Is Not Under Quorum-Sensing Control

 

Auteurs : Lisa Tanet, Christian Tamburini, Chloé Baumas, Marc Garel, Gwénola Simon and Laurie Casalot (all MIO)

Frontiers in Microbiology March 2019, Volume 10, Article 365
Doi: 10.3389/fmicb.2019.00365

Abstract : Bacterial-bioluminescence regulation is often associated with quorum sensing. Indeed, many studies have been made on this subject and indicate that the expression of the light-emission-involved genes is density dependent. However, most of these studies have concerned two model species, Aliivibrio fischeri and Vibrio campbellii. Very few works have been done on bioluminescence regulation for the other bacterial genera. Yet, according to the large variety of habitats of luminous marine bacteria, it would not be surprising to find different light-regulation systems. In this study, we used Photobacterium phosphoreum ANT-2200, a piezophilic bioluminescent strain isolated from Mediterranean deep-sea waters (2200-m depth). To answer the question of whether or not the bioluminescence of P. phosphoreum ANT-2200 is under quorum-sensing control, we focused on the correlation between growth and light emission through physiological, genomic and, transcriptomic approaches. Unlike A. fischeri and V. campbellii, the light of P. phosphoreum ANT-2200 immediately increases from its initial level. Interestingly, the emitted light increases at much higher rate at the low cell density than it does for higher cell-density values. The expression level of the light-emission-involved genes stays constant all along the exponential growth phase. We also showed that, even when more light is produced, when the strain is cultivated at high hydrostatic pressure, no change in the transcription level of these genes can be detected. Through different experiments and approaches, our results clearly indicate that, under the tested conditions, the genes, directly involved in the bioluminescence in P. phosphoreum ANT-2200, are not controlled at a transcriptomic level. Quite obviously, these results demonstrate that the light emission of the strain is not density dependent, which means not under quorum-sensing control. Through this study, we point out that bacterial-bioluminescence regulation should not, from now on, be always linked with the quorum-sensing control.

 

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Synthesis review of the Gulf of Gabes (eastern Mediterranean Sea, Tunisia): Morphological, climatic, physical oceanographic, biogeochemical and fisheries features

 

Auteurs : Béjaoui Béchir , Sana Ben Ismail, Achref Othmani, Olfa Ben Abdallah-Ben Hadj Hamida, Cristèle Chevalier (MIO), Wafa Feki-Sahnoun, Ali Harzallah, Nader Ben Hadj Hamida, Riadh Bouaziz, Salem Dahech, Frédéric Diaz (MIO), Khouthir Tounsi, Cherif Sammari, Marc Pagano (MIO), Malika Bel Hassen

Estuarine, Coastal and Shelf Science, 219, 395-408
DOI : 10.1016/j.ecss.2019.01.006

Faits marquants

•The coastal morphology of the Gulf of Gabes is characterized by beaches, cliffs and wetlands.
•The climate of the Gulf of Gabes is characterized by temperate and hot subtropical Saharan climate.
•The water circulation and water level are closely associated with tides.
•The Gulf of Gabes is considered as the most productive area in the Mediterranean.

 

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Changes in Bacterioplankton Communities Resulting From Direct and Indirect Interactions With Trace Metal Gradients in an Urbanized Marine Coastal Area

 

Auteurs : Clément Coclet (MIO), Cédric Garnier (MIO), Gaël Durrieu (MIO), Dario Omanović, Sébastien D’Onofrio (MIO), Christophe Le Poupon (MIO), Jean-Ulrich Mullot, Jean-François Briand and Benjamin Misson (MIO)

Front. Microbiol., 22 February 2019  - https://doi.org/10.3389/fmicb.2019.00257

Résumé : Unraveling the relative importance of both environmental conditions and ecologicalprocesses regulating bacterioplankton communities is a central goal in microbialecology. Marine coastal environments are among the most urbanized areas and as aconsequence experience environmental pressures. The highly anthropized Toulon Bay(France) was considered as a model system to investigate shifts in bacterioplanktoncommunities along natural and anthropogenic physicochemical gradients during a1-month survey. In depth geochemical characterization mainly revealed strong andprogressive Cd, Zn, Cu, and Pb contamination gradients between the entrance ofthe Bay and the north-western anthropized area. On the other hand, low-amplitudenatural gradients were observed for other environmental variables. Using 16S rRNAgene sequencing, we observed strong spatial patterns in bacterioplankton taxonomicand predicted function structure along the chemical contamination gradient. Variationpartitioning analysis demonstrated that multiple metallic contamination explained thelargest part of the spatial biological variations observed, but DOC and salinity werealso significant contributors. Network analysis revealed that biotic interactions were farmore numerous than direct interactions between microbial groups and environmentalvariables. This suggests indirect effects of the environment, and especially trace metals,on the community through a few taxonomic groups. These spatial patterns werealso partially found for predicted bacterioplankton functions, thus indicating a limitedfunctional redundancy. All these results highlight both potential direct influences of tracemetals contamination on coastal bacterioplankton and indirect forcing through bioticinteractions and cascading.

Mots clés : coastal ecosystem, metal contamination gradients, bacterioplankton community structure, functional prediction, co-occurrence network

 

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Toward science-oriented validations of coastal altimetry: Application to the Ligurian Sea

 

Auteurs : M.Meloni, J.Bouffard, A.M.Dogliolic (MIO), A.Petrenko (MIO), G.Valladeaud

Remote Sensing of Environment
Volume 224, April 2019, Pages 275-288 - https://doi.org/10.1016/j.rse.2019.01.028

Résumé : This study is a preliminary contribution to the European Space Agency's efforts aimed at establishing reference in situ networks specifically targeted to validate coastal altimetry. For this purpose, we processed and cross-compared conjointly improved altimetry data and in situ measurements acquired over the Ligurian Sea – a coastal region of the Mediterranean characterised by complex, fine-scale and rapidly evolving oceanic features. We made use of several kinds of multi-sensor in situ observations located along SARAL and Jason-2 tracks. The main objectives of the study were to assess improved coastal oriented validation strategies, including the usage of a new in situ platform (Moving Vessel Profiler), while better understanding potential differences owing to physical content inconsistency and instrumental or data processing limitations. The results show remarkable agreements over spatial scales of few tens of kilometres, paving the way for the deployment of future in situ networks and the definition of science-oriented diagnostics targeted to assess the capability of present and future high-resolution altimetric missions in resolving small-scale physical features.

Mots clés : Coastal altimetry Mesoscale Validation and verification Northern current

 

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Pascal Hingamp (MIO) co-auteur de Minimum Information about an Uncultivated Virus Genome (MIUViG)

 

In Nature Biotechnology volume 37, pages 29–37 (2019)

Auteurs : Roux S, Adriaenssens EM, Dutilh BE, Koonin EV, Kropinski AM, Krupovic M, Kuhn JH, Lavigne R, Brister JR, Varsani A, Amid C, Aziz RK, Bordenstein SR, Bork P, Breitbart M, Cochrane GR, Daly RA, Desnues C, Duhaime MB, Emerson JB, Enault F, Fuhrman JA, Hingamp P (MIO), Hugenholtz P, Hurwitz BL, Ivanova NN, Labonté JM, Lee KB, Malmstrom RR, Martinez-Garcia M, Mizrachi IK, Ogata H, Páez-Espino D, Petit MA, Putonti C, Rattei T, Reyes A, Rodriguez-Valera F, Rosario K, Schriml L, Schulz F, Steward GF, Sullivan MB, Sunagawa S, Suttle CA, Temperton B, Tringe SG, Thurber RV, Webster NS, Whiteson KL, Wilhelm SW, Wommack KE, Woyke T, Wrighton KC, Yilmaz P, Yoshida T, Young MJ, Yutin N, Allen LZ, Kyrpides NC, Eloe-Fadrosh EA.

Résumé : We present an extension of the Minimum Information about any (x) Sequence (MIxS) standard for reporting sequences of uncultivated virus genomes. Minimum Information about an Uncultivated Virus Genome (MIUViG) standards were developed within the Genomic Standards Consortium framework and include virus origin, genome quality, genome annotation, taxonomic classification, biogeographic distribution and in silico host prediction. Community-wide adoption of MIUViG standards, which complement the Minimum Information about a Single Amplified Genome (MISAG) and Metagenome-Assembled Genome (MIMAG) standards for uncultivated bacteria and archaea, will improve the reporting of uncultivated virus genomes in public databases. In turn, this should enable more robust comparative studies and a systematic exploration of the global virosphere.

 

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A Mild-Slope System for Bragg Scattering of Water Waves by Sinusoidal Bathymetry in the Presence of Vertically Sheared Currents

 

Auteurs : Kostas Belibassakis, Julien Touboul (MIO), Elodie Laffitte (MIO), Vincent Rey (MIO).

Received : 12 October 2018 / Accepted : 29 December 2018 / Published : 7 January 2019
J. Mar. Sci. Eng. 2019, 7(1), 9 ; doi:10.3390/jmse7010009

Résumé : Extended mild-slope models (MMSs) are examined for predicting the characteristics of normally incident waves propagating over sinusoidal bottom topography in the presence of opposing shearing currents. It is shown that MMSs are able to provide quite good predictions in the case of Bragg scattering of waves over rippled bathymetry without a current, but fail to provide good predictions concerning the resonant frequency in the additional presence of a current. In order to resolve the above mismatch, a two-equation mild-slope system (CMS2) is derived from a variational principle based on the representation of the wave potential expressed as a superposition of the forward and backward components. The latter system is compared against experimentally measured data collected in a wave flume and is shown to provide more accurate predictions concerning both the resonant frequency and the amplitude of the reflection coefficient. Future work will be devoted to the examination of the derived model for a more general wave system over realistic seabed topography. View Full-Text

Mots clés : wave-current interaction ; sinusoidal bathymetry ; resonant reflection ; mild-slope equation ; coupled-mode system

 

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Damage-related protein turnover explains inter-specific patterns of maintenance rate and suggests modifications of the DEB theory

 

Auteurs : Olivier Maury, Jean-Christophe Poggiale (MIO), Olivier Aumont

Journal of Sea Research, Elsevier, 2019, 143, pp.35-47

Résumé : Maintenance is the energy that living organisms are bound to use to maintain their structure in a viable state. It includes all the metabolic and physiological costs that are not directly associated to the production of biomass (growth and reproduction) or to development (maturation). In the framework of the DEB theory, somatic maintenance rate can either be proportional to organism structural volume V or, more marginally, to structural surface V 2/3. Being mostly associated to similar metabolic processes, volume specific maintenance costs are not expected to vary substantially at both intra-and interspecific levels. In the DEB theory, the volume-specific maintenance rate is therefore supposed to keep constant from birth to death and to remain approximately constant between species. However, a recent meta-analysis of DEB parameters estimated using the Add-my-Pet collection (Kooijman, 2014) reveals troubling patterns apparently violating this inter-specific scaling rule and challenging the DEB theory. It is indeed shown in this study that empirically-derived volume-specific maintenance rates scale approximately with, and display a very high variability around this trend. Overall, estimated maintenance rates in Add-my-Pet span over three to four orders of magnitude, thus invalidating the assumption of constant maintenance rate between species, which underpins the covariation rules for parameter values of the DEB theory. In an attempt to address this major problem for the DEB theory, we propose a simple physiological mechanism that would simultaneously explain the apparent decrease of volume-specific maintenance rate with ultimate size and its apparent variability for a given range of maximum size. Our proposition consists in making protein (and more generally structure) turnover explicit in maintenance and linking protein damage rate to aerobic metabolism and the production of ROS, which are decreasing with both structural volume and maximum structural volume. We show that this implies that the actual volume specific maintenance rate varies both at the intra- and inter-specific levels in a range very similar to what is observed in the Add-my Pet data estimations. If true, this implies that the apparent decrease of volume-specific maintenance rate with ultimate size is an artefact and it requires modifications of the standard DEB theory in order to capture empirical inter-specific scaling patterns of DEB parameters while keeping the consistency of the theory at both intra- and inter-specific levels.

 

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Spatio-temporal variability in benthic exchanges at the sediment-water interface of a shallow tropical coastal lagoon (south coast of Gulf of Mexico)

 

Auteurs : Christian Grenz (MIO), Montserrat Moreno (MIO), Karline Soetaert, Lionel Denis, Pascal Douillet (MIO), Renaud Fichez (MIO)

Estuarine, Coastal and Shelf Science
Volume 218, 5 March 2019, Pages 368-380

Résumé : The sediment in Laguna de Términos, the largest and shallowest system in the Southwest portion of the Gulf of Mexico features a broad range of ecological and hydrobiological characteristics driven by annual weather cycles (dry and wet seasons), causing large salinity gradients during the wet season due to large river discharges. Four sampling campaigns were carried out during the wet and the dry seasons in 2009 and 2010 on a selection of 13 out of 35 stations. Measurements of Sediment Oxygen Demand (SOD) and nutrient fluxes at the sediment-water interface were performed using lab incubations with 15 cm diameter sediment cores. SOD fluctuated between 1327 ± 161 and 2248 ± 359 μmol m −2 h −1 for dry and wet seasons respectively. Silicate effluxes were also significantly higher during the wet seasons (89.4 ± 15.9 μmol m −2 h −1) than during the dry season (46.5 ± 11.4 μmol m −2 h −1). PO 4 fluxes were low all over the study period without seasonal trend. No significant difference was measured for DIN fluxes but there was a tendency for DIN uptake during the wet season (−2.9 ± 18.8 μmol m −2 h −1) and conversely an efflux during the dry season (24.3 ± 7.3 μmol m −2 h −1). SOD correlated to organic matter and chloropigment content of the sediments while silicate fluxes responded to enhanced chloropigments in the sediments. During both seasons, total benthic nutrient fluxes overwhelmed largely riverine inputs and benthic carbon mineralization rates approximated a significant proportion of the pelagic organic carbon production. We conclude that benthic processes in Laguna de Términos are largely driven by weather variability and that they contribute substantially to carbon and nutrient budgets in this shallow subtropical system.

 

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