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27 páginas, 11 tablas, 9 figuras.-- Are Olsen . et al.-- This work is distributed under the Creative Commons Attribution 3.0 License.-- Proyecto Carbochange ; Version 2 of the Global Ocean Data Analysis Project (GLODAPv2) data product is composed of data from 724 scientific cruises covering the global ocean. It includes data assembled during the previous efforts GLODAPv1.1 (Global Ocean Data Analysis Project version 1.1) in 2004, CARINA (CARbon IN the Atlantic) in 2009/2010, and PACIFICA (PACIFic ocean Interior CArbon) in 2013, as well as data from an additional 168 cruises. Data for 12 core variables (salinity, oxygen, nitrate, silicate, phosphate, dissolved inorganic carbon, total alkalinity, pH, CFC-11, CFC-12, CFC-113, and CCl4) have been subjected to extensive quality control, including systematic evaluation of bias. The data are available in two formats: (i) as submitted but updated to WOCE exchange format and (ii) as a merged and internally consistent data product. In the latter, adjustments have been applied to remove significant biases, respecting occurrences of any known or likely time trends or variations. Adjustments applied by previous efforts were re-evaluated. Hence, GLODAPv2 is not a simple merging of previous products with some new data added but a unique, internally consistent data product. This compiled and adjusted data product is believed to be consistent to better than 0.005 in salinity, 1 % in oxygen, 2 % in nitrate, 2 % in silicate, 2 % in phosphate, 4 µmol kg−1 in dissolved inorganic carbon, 6 µmol kg−1 in total alkalinity, 0.005 in pH, and 5 % for the halogenated transient tracers ; The GLODAPv2 project itself received support from a number of agencies and projects. Importantly, the EU-IP CARBOCHANGE (FP7 264878) provided funding for A. Olsen, M. Hoppema, S. van Heuven, and T. Tanhua as well as travel support for R. Key and the project framework that instigated GLODAPv2. A. Olsen further acknowledges generous support from the FRAM – High North Research Centre for Climate and the Environment, the Centre for Climate Dynamics at the Bjerknes Centre for Climate Research, the EU AtlantOS (grant agreement no. 633211) project, and the Norwegian Research Council project SNACS (229752). R. Key was supported by KeyCrafts grant 2012-001, CICS grants NA08OAR4320752 and NA14OAR4320106, NASA grant NNX12AQ22G, NSF grants OCE-0825163 (with a supplement via WHOI P.O. C119245) and PLR-1425989, and Battelle contract #4000133565 to CDIAC. A. Kozyr was supported by DOE contract DE-AC05-00OR2272 to UT-Battelle, operators of CDIAC under ORNL. S. K. Lauvset and E. Jeansson appreciate support from the Norwegian Research Council (projects DECApH, 214513 and VENTILATE, 229791). The International Ocean Carbon Coordination Project (IOCCP) also supported this activity through the U.S. National Science Foundation grant (OCE- 1243377) to the Scientific Committee on Oceanic Research. A. Velo and F. F. Pérez acknowledge the support provided by BOCATS project (CTM2013-41048-P) co-funded by the Spanish Government and the Fondo Europeo de Desarrollo Regional (FEDER), and the AtlantOS project (grant agreement no. 633211) funded by EU H2020 research and innovation programme. ; Peer reviewed

9 pages, 5 figures, 2 tables.-- Under a Creative Commons license ; The chemical conditions of the Argentine Basin (western South Atlantic Ocean) water masses are evaluated with measurements from eleven hydrographic cruises to detect and quantify anthropogenic and natural stressors in the ocean carbon system. The database covers almost half-century (1972–2019), a time-span where the mean annual atmospheric carbon dioxide concentration (CO2atm) increased from 325 to 408 ppm of volume (ppm). This increase of atmospheric CO2 (83 ppm, the 64% of the total anthropogenic signal in the atmosphere) leads to an increase in anthropogenic carbon (Cant) across all the water column and the consequent ocean acidification: a decrease in excess carbonate that is unequivocal in the upper (South Atlantic Central Water, SACW) and intermediate water masses (Sub Antarctic Mode Water, SAMW and Antarctic Intermediate Water, AAIW). For each additional ppm in CO2atm the water masses SACW, SAMW and AAIW lose excess carbonate at a rate of 0.39 ± 0.04, 0.47 ± 0.05 and 0.23 ± 0.03 μmol·kg−1·ppm−1 respectively. Modal and intermediate water masses in the Argentine Basin are very sensitive to carbon increases due low buffering capacity. The large rate of AAIW acidification is the synergic effect of carbon uptake combined with deoxygenation and increased remineralization of organic matter. If CO2 emissions follows the path of business-as-usual emissions (SSP 5.85), SACW would become undersaturated with respect to aragonite at the end of the century. The undersaturation in AAIW is virtually unavoidable ; For this work M. Fontela was funded by Portuguese national funds from FCT - Foundation for Science and Technology through project UIDB/Multi/04326/2020 and CEECINST/00114/2018. A. Velo and F. F. Pérez were supported by the BOCATS2 Project (PID2019-104279GB-C21) co-funded by the Spanish Government and the Fondo Europeo de Desarrollo Regional (FEDER). A. Velo, M.Gilcoto and F. F. Pérez were supported by the European Union's Horizon 2020 research and innovation program under grant agreement No 820989 (project COMFORT ; Peer reviewed

10 pages, 5 figures.-- This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) ; In the North Atlantic, there are two main western boundary currents related to the Atlantic Meridional Overturning Circulation (AMOC): the Gulf Stream flowing northward and the Deep Western Boundary Current (DWBC) flowing southward. Here we analyze data from the OVIDE section (GO-SHIP A25 Portugal-Greenland 40–60°N) that crosses the DWBC and the northward extension of the Gulf Stream, the North Atlantic Current. We show that North Atlantic western boundary currents play a key role in the transport of dissolved organic matter, specifically dissolved organic carbon (DOC). Revisited transports and budgets of DOC with new available data identify the eastern Subpolar North Atlantic (eSPNA) as an important source of locally produced organic matter for the North Atlantic and a key region in the supply of bioavailable DOC to the deep ocean. The East Greenland Current, and its upstream source the East Reykjanes Ridge Current on the eastern flank of the mid-Atlantic ridge, are export pathways of bioavailable DOC toward subtropical latitudes. The fast overturning and subsequent remineralization of DOC produced in the autotrophic eSPNA explains up to 38% of the total oxygen consumption in the deep North Atlantic between the OVIDE section and 24°N. Carbon budgets that do not take into account this organic remineralization process overestimates the natural uptake of carbon dioxide (CO2) from the atmosphere by one third. The inclusion of DOC transports in regional carbon budgets reconciles the estimates of CO2 uptake in the North Atlantic between model and observations ; For this work MF was funded by the Spanish Ministry of Economy and Competitiveness (BES-2014-070449) supported by the Spanish Government and co-funded by the Fondo Europeo de Desarrollo Regional 2007–2012 (FEDER) and by Portuguese national funds from FCT – Foundation for Science and Technology through project UID/Multi/04326/2019 and CEECINST/00114/2018. FP was supported by the BOCATS2 Project (PID2019-104279GB-C21) and ARIOS project (CTM2016-76146-C3-1-R) both co-funded by the Spanish Government and the Fondo Europeo de Desarrollo Regional (FEDER). This project has received funding from the European Union's Horizon 2020 Research and Innovation Program under grant agreement no. 820989 (project COMFORT, Our common future ocean in the Earth system–quantifying coupled cycles of carbon, oxygen, and nutrients for determining and achieving safe operating spaces with respect to tipping points). HM was supported by the French Centre National de la Recherche Scientifique ; Peer reviewed

16 páginas, 14 figuras, 3 tablas.-- Siv K. Lauvset . et al.-- This work is distributed under the Creative Commons Attribution 3.0 License.-- Proyecto Carbochange ; We present a mapped climatology (GLODAPv2.2016b) of ocean biogeochemical variables based on the new GLODAP version 2 data product (Olsen et al., 2016; Key et al., 2015), which covers all ocean basins over the years 1972 to 2013. The quality-controlled and internally consistent GLODAPv2 was used to create global 1° × 1° mapped climatologies of salinity, temperature, oxygen, nitrate, phosphate, silicate, total dissolved inorganic carbon (TCO2), total alkalinity (TAlk), pH, and CaCO3 saturation states using the Data-Interpolating Variational Analysis (DIVA) mapping method. Improving on maps based on an earlier but similar dataset, GLODAPv1.1, this climatology also covers the Arctic Ocean. Climatologies were created for 33 standard depth surfaces. The conceivably confounding temporal trends in TCO2 and pH due to anthropogenic influence were removed prior to mapping by normalizing these data to the year 2002 using first-order calculations of anthropogenic carbon accumulation rates. We additionally provide maps of accumulated anthropogenic carbon in the year 2002 and of preindustrial TCO2. For all parameters, all data from the full 1972–2013 period were used, including data that did not receive full secondary quality control. The GLODAPv2.2016b global 1° × 1° mapped climatologies, including error fields and ancillary information, are available at the GLODAPv2 web page at the Carbon Dioxide Information Analysis Center (CDIAC; doi:10.3334/CDIAC/OTG.NDP093_GLODAPv2) ; The work of S. K. Lauvset was funded by the Norwegian Research Council through the projects DECApH (214513/F20). The EU-IP CARBOCHANGE (FP7 264878) project provided funding for A. Olsen, S. van Heuven, T. Tanhua, R. Steinfeldt, and M. Hoppema and is the project framework that instigated GLODAPv2. A. Olsen additionally acknowledges generous support from the FRAM – High North Research Centre for Climate and the Environment, the Centre for Climate Dynamics at the Bjerknes Centre for Climate Research, the EU AtlantOS (grant agreement no. 633211) project, and the Norwegian Research Council project SNACS (229752). Emil Jeansson appreciates support from the Norwegian Research Council project VENTILATE (229791). R. Key was supported by KeyCrafts grant 2012-001, CICS grants NA08OAR4320752 and NA14OAR4320106, NASA grant NNX12AQ22G, NSF grants OCE-0825163 (with a supplement via WHOI P.O. C119245) and PLR-1425989, and Battelle contract #4000133565 to CDIAC. A. Kozyr acknowledges funding from the US Department of Energy. M. Ishii acknowledges the project MEXT 24121003. A. Velo and F. F. Pérez were supported by the BOCATS (CTM20134410484P) project cofounded by the Spanish government and the Fondo Europeo de Desarrollo Regional (FEDER). The International Ocean Carbon Coordination Project (IOCCP) partially supported this activity through the U.S. National Science Foundation grant (OCE- 1243377) to the Scientific Committee on Oceanic Research. The research leading to the last developments of DIVA has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 283607, SeaDataNet 2, and from the project EMODNET (MARE/2012/10 – Lot 4 Chemistry – SI2.656742) from the Directorate-General for Maritime Affairs and Fisheries ; Peer reviewed

20 páginas, 5 tablas, 6 figuras, 1 apéndice.-- Proyecto Carbochange ; The Mediterranean Outflow Water (MOW) spills from the Mediterranean Sea (east North Atlantic basin) west off the Strait ofGibraltar.AsMOWoutflows, it entrains eastern NorthAtlantic CentralWaters (ENACW) and IntermediateWaters to formthe neutrally buoyantMediterraneanWater (MW) that can be traced over the entire NorthAtlantic basin. Its high salinity content influences the thermohaline properties of the intermediate– deepwater column in theNorthAtlantic and its dynamics.Here, the composition ofMWin its source region (the Gulf of Cádiz, west off Strait of Gibraltar) is investigated on the basis of an optimum multiparameter analysis. The results obtained indicate that mixing of MOW (34.1% 6 0.3%) occurs mainly with overlying ENACW (57.1% 6 0.8%) in a process broadly known as central water entrainment. A diluted form (80% of dilution) of the Antarctic Intermediate Water (AAIW) reaches the region and also takes part in MW formation (8.3% 6 0.5%). Finally, the underlying Labrador Sea Water (LSW) also contributes (0.4%6 0.1%) to the characteristics ofMW. Fromthese results and considering 0.74 Sverdrups (Sv; 1 Sv[ 106m3 s21) as themean outflow ofMOW, the MW exportation rate was inferred (2.2 Sv), which, decomposing MW, means that the MOW outflow is accompanied by 1.24 Sv of entrained ENACW, 0.18 Sv of AAIW, and ,0.01 Sv of LSW. ; The research was supported through the Seventh Framework Program (EU FP7 Project CARBOCHANGE, ''Changes in carbon uptake and emissions by oceans in a changing climate,'' C_ENVIR/0869). All the authors were funded by the Spanish Research Council (CSIC). The first author was also partly financed by the Regional Government of Galicia through a specific program for short stays abroad, cofounded by the European Social Fund (FSE) 2011–15 and now is being funded by the University of Vigo, through the Galician I2C Plan for postdoctoral research ; Peer reviewed

7 páginas, 1 tabla, 4 figuras ; This study constituted the first attempt to measure dissolved calcium ([Ca2 +]meas) in the subtropical North Atlantic, during a zonal transoceanic cruise along 24.5°N (WOCE A05 section), in summer 1992. [Ca2 +]meas was obtained in 20 full-depth equidistant stations along the section, showing that their gradients are rather sensitive to horizontal and vertical water mass distribution. Deep waters along 24.5°N systematically show a positive calcium excess of 20 ± 14 μmol·kg− 1, i.e., more [Ca2 +] than expected by CaCO3 dissolution and organic matter oxidation (estimated by total alkalinity and nitrate). CaCO3 settling and benthic dissolution accounts for 70% and the North Atlantic plus Arctic riverine inputs of HCO3− for the remaining 30%. Combining [Ca2 +]meas and CO2 data sets, carbonate mineral saturation states distributions for aragonite and calcite can be obtained. The two solubility ratios resulted, on average, 0.5% smaller than if conservative behavior for Ca2 + was assumed (an approach widely followed when [Ca2 +]meas is unknown). As a result, shallower saturation horizon depths for both carbonate states (19 dbar for aragonite and 10 dbar for calcite) are yielded if [Ca2 +]meas is taken into account instead than estimated from salinity ; This work has been performed under the project BOCATS (CTM2013-41048-P) supported by the Spanish Government and co-founded by the European Regional Development Fund (FEDER) ; Peer reviewed

18 páginas, 10 figuras, 5 tablas ; A three-sided box, MedBox, comprising the Strait of Gibraltar, 24 –41 N east of 22 W, was constructed using hydrographic and chemical data from three World Ocean Circulation Experiment cruises in 1997–1998. An extended optimum multiparameter (OMP) analysis resolves the water mass structure in the MedBox. The mass transport is estimated from data and models warranting mass conservation and no deep water formation within the region. Combining the mass transport, the OMP analysis, and the spatial distribution of anthropogenic carbon (CANT), some relevant questions about the Mediterranean Water (MW) formation, transport, and role in the global CO2 cycle are resolved. MWis produced at a rate of 2.7 ± 0.2 Sv in the eastern North Atlantic. It entrains 2.3 Sv of central waters during its formation, including also remnants of Antarctic Intermediate Water. The main advection route of MW is northward, close to the Iberian margin (2.2 Sv), while about 0.5 Sv are exported into the subtropical eastern North Atlantic. The eastern North Atlantic within the MedBox is a strong region of air-sea CANT uptake, 0.7 ± 0.7 mmol m 2 d 1, where CANT is accumulated at a rate of 66 ± 21 kmol s 1 (0.025 GtC yr 1), 17% are taken up through the air-sea interface, and the rest is advected into the area by the circulation. The entrainment of central waters to form MW drives a drawdown of 151 ± 14 kmol s 1 (0.06 GtC yr 1) from the surface to intermediate levels, and 88 ± 8 kmol s 1 (0.03 GtC yr 1) are exported with MW into the North Atlantic, mainly by the horizontal/eddy circulation. ; M.Á. was funded by the European Union under a Global Change I3P postdoctoral contract. F.F.P. was funded by the CICYT VACLAN project REN2003-08193-C03-02MAR. ; Peer reviewed

16 pages, 2 tables, 5 figures.-- This article is licensed under a Creative Commons Attribution 4.0 International License ; The processes of warming, anthropogenic CO2 (Canth) accumulation, decreasing pHT (increasing [H+]T; concentration in total scale) and calcium carbonate saturation in the subarctic zone of the North Atlantic are unequivocal in the time-series measurements of the Iceland (IS-TS, 1985–2003) and Irminger Sea (IRM-TS, 1983–2013) stations. Both stations show high rates of Canth accumulation with different rates of warming, salinification and stratification linked to regional circulation and dynamics. At the IS-TS, advected and stratified waters of Arctic origin drive a strong increase in [H+]T, in the surface layer, which is nearly halved in the deep layer (44.7 ± 3.6 and 25.5 ± 1.0 pmol kg−1 yr−1, respectively). In contrast, the weak stratification at the IRM-TS allows warming, salinification and Canth uptake to reach the deep layer. The acidification trends are even stronger in the deep layer than in the surface layer (44.2 ± 1.0 pmol kg−1 yr−1 and 32.6 ± 3.4 pmol kg−1 yr−1 of [H+]T, respectively). The driver analysis detects that warming contributes up to 50% to the increase in [H+]T at the IRM-TS but has a small positive effect on calcium carbonate saturation. The Canth increase is the main driver of the observed acidification, but it is partially dampened by the northward advection of water with a relatively low natural CO2 content ; FFP was founded by the Ministerio Ciencia, Innovación y Universidades (Grant No. PRX18/00312) for visiting Dr. Taro Takahashi in LDEO in 2019. FFP were also supported by the BOCATS2 Project (PID2019-104279GB-C21) co-funded by the Spanish Government and the Fondo Europeo de Desarrollo Regional (FEDER). FFP and SRO were supported by the European Union's Horizon 2020 research and innovation program under Grant Agreement No. 820989 (project COMFORT, Our common future ocean in the Earth system-quantifying coupled cycles of carbon, oxygen and nutrients for determining and achieving safe operating spaces with respect to tipping points ; Peer reviewed

Sabine, C. L. et al. ; As a response to public demand for a well-documented, quality controlled, publically available, global surface ocean carbon dioxide (CO2) data set, the international marine carbon science community developed the Surface Ocean CO2 Atlas (SOCAT). The first SOCAT product is a collection of 6.3 million quality controlled surface CO2 data from the global oceans and coastal seas, spanning four decades (1968–2007). The SOCAT gridded data presented here is the second data product to come from the SOCAT project. Recognizing that some groups may have trouble working with millions of measurements, the SOCAT gridded product was generated to provide a robust, regularly spaced CO2 fugacity (fCO2) product with minimal spatial and temporal interpolation, which should be easier to work with for many applications. Gridded SOCAT is rich with information that has not been fully explored yet (e.g., regional differences in the seasonal cycles), but also contains biases and limitations that the user needs to recognize and address (e.g., local influences on values in some coastal regions). ; SOCAT is promoted by IOCCP, the Sur- face Ocean Lower Atmosphere Study, and the Integrated Marine Biogeochemistry and Ecosystem Research program. Douglas Wallace (Dalhousie University, Canada and former SOLAS chair) has strongly encouraged SOCAT. Support has been received from the University of Bergen (Norway), the Bjerknes Centre for Cli- mate Research (Norway), the National Oceanic and Atmospheric Administration (United States), the University of Washington (United States), Oak Ridge National Laboratory (United States), the University of East Anglia (United Kingdom), PANGAEA – Data Publisher for Earth & Environmental data (Germany), the Alfred Wegener Institute for Polar and Marine Research (Ger- many), the Centre National de la Recherche Scientifique (France), the CarboOcean (Norway, GOCE 511176-1) and CarboChange (Norway, FP7 264879) projects of the European Union, the US National Science Foundation (United States, OCE-1068958), the international Scientific Committee on Oceanic Research (SCOR, United States, OCE-0938349), and the UK Ocean Acidification Research Programme (NE / H017046 / 1; funded by the Natural Environment Research Council, the Department for Energy and Climate Change and the Department for Environment, Food and Rural A ff airs). Support for SOCAT meetings has been received from IOCCP, IMBER, the European Cooperation in Science and Technology (COST) Action 735 (United Kingdom), Geomar (Germany), the National Institute for Environmental Studies (Japan), and the Commonwealth Scientific and Industrial Research Organisation (Australia). ; Peer reviewed

9 páginas, 4 figuras, 1 tabla.-- This work is licensed under a Creative Commons Attribution 4.0 International License ; The quantitative role of the Atlantic Meridional Overturning Circulation (AMOC) in dissolved organic carbon (DOC) export is evaluated by combining DOC measurements with observed water mass transports. In the eastern subpolar North Atlantic, both upper and lower limbs of the AMOC transport high-DOC waters. Deep water formation that connects the two limbs of the AMOC results in a high downward export of non-refractory DOC (197 Tg-C·yr−1). Subsequent remineralization in the lower limb of the AMOC, between subpolar and subtropical latitudes, consumes 72% of the DOC exported by the whole Atlantic Ocean. The contribution of DOC to the carbon sequestration in the North Atlantic Ocean (62 Tg-C·yr−1) is considerable and represents almost a third of the atmospheric CO2 uptake in the region ; For this work M. Fontela was funded by the Spanish Ministry of Economy and Competitiveness (BES-2014-070449) through the BOCATS project (CTM2013-41048-P) supported by the Spanish Government and co-funded by the Fondo Europeo de Desarrollo Regional 2007–2012 (FEDER); and this article is going to be part of her PhD that is attached to the framework of the doctoral program "Marine Science, Technology and Management" (DO*MAR) of the University of Vigo. M.I. García-Ibáñez and F.F. Pérez were supported by the BOCATS project (CTM2013-41048-P) co-funded by the Spanish Government and the Fondo Europeo de Desarrollo Regional (FEDER). D.A. Hansell was supported by US National Science Foundation award OCE-1436748. H. Mercier was supported by the CNRS and the ATLANTOS project (GA 633211) ; Peer reviewed

9 páginas, 1 tabla, 2 figuras.-- Proyecto Carbochange.-- The OVIDE data analyzed in this study are available at the CLIVAR and Carbon Hydrographic Data Office (http://cchdo.ucsd.edu/search?q=Ovide) and at the Carbon Dioxide Information Analysis Center (http://cdiac.ornl.gov/oceans/RepeatSections/clivar_ovide.html). The climatology of Takahashi et al. was downloaded from http://www.ldeo.columbia.edu/res/pi/CO2/carbondioxide/pages/air_sea_flux_2000.html ; The subpolar North Atlantic (SPNA) is important in the global carbon cycle because of the deep water ventilation processes that lead to both high uptake of atmospheric CO2 and large inventories of anthropogenic CO2 (Cant). Thus, it is crucial to understand its response to increasing anthropogenic pressures. In this work, the budgets of dissolved inorganic carbon (DIC), Cant and natural DIC (DICnat) in the eastern SPNA in the 2000s, are jointly analyzed using in situ data. The DICnat budget is found to be in steady state, confirming a long-standing hypothesis from in situ data for the first time. The biological activity is driving the uptake of natural CO2 from the atmosphere. The Cant increase in the ocean is solely responsible of the DIC storage rate which is explained by advection of Cant from the subtropics (65%) and Cant air-sea flux (35%). These results demonstrate that the Cant is accumulating in the SPNA without affecting the natural carbon cycle ; This work is a contribution to the EU FP7 CARBOCHANGE project (264879) and the ANR GEOVIDE project (http://www.agence-nationale-recherche.fr/?Project=ANR-13-BS06-0014). For this work P. Zunino was funded by CARBOCHANGE and GEOVIDE projects as well as by IFREMER. The Tricontinental Atlantic Campus funded a 6 months contract for the first author at the Universidad de Las Palmas de Gran Canaria where part of this paper was written. P. Lherminier was supported by IFREMER, H. Mercier by the CNRS and the ATLANTOS GA 633211 H2020 project, and A. Padin by the Consejo Superior de Investigaciones Científicas (CSIC). A.F. Ríos and F.F. Pérez were supported by BOCATS (CTM2013-41048-P) project cofounded by the Spanish Government and the Fondo Europeo de Desarrollo Regional (FEDER) ; Peer reviewed

16 pages, 4 figures, 2 tables.-- This is an Open Access article distributed under the terms of the Creative Commons Attribution License ; The impact of simulated seawater acidification and warming conditions on specimens of the mussel Mytilus galloprovincialis locally adapted to very distinct, widely separated sites in the Mediterranean Sea (Tunisia) and Atlantic Sea (Galicia, NW Spain) was evaluated in relation to key behavioural and eco-physiological parameters. Over the 2-month exposure to the experimental conditions, mussels were fed optimally to ensure that there are no synergistic interactions between climate change drivers and energetic status of the individuals. In general, regardless of origin (Atlantic or Mediterranean), the mussels were rather resilient to acidification for most of the parameters considered and they were able to grow in strongly acidified seawater through an increased feeding activity. However, shell strength decreased (40%) consistently in both mussel populations held in moderately and highly acidified seawater. The observed reduction in shell strength was not explained by slight alterations in organic matter, shell thickness or aragonite:calcite ratio. The combined effects of high acidification and warming on the key response of byssus strength caused a strong decline in mussel performance, although only in Galician mussels, in which the valve opening time decreased sharply as well as condition index (soft tissue state) and shell growth. By contrast, the observed negative effect of highly acidified scenario on the strength of Tunisian mussel shells was (partly but not totally) counterbalanced by the higher seawater temperature. Eco-physiological and behavioural interactions in mussels in relation to climate change are complex, and future scenarios for the ecology of the species and also the feasibility of cultivating them in Atlantic and Mediterranean zones are discussed ; This work was supported by the Spanish government through the Ministerio de Economía y Competitividad and European FEDER funds (AGL-2013-45945-R, CTM2016-76146-C3-2-R/CTM2016-76146-C3-1-R) and the Spanish National Research Council (CSIC) through the program I-COOP+ 2016 (ICOOPA20147 to J.L.) ; Peer reviewed

The carbon dioxide taken up by the ocean is increasing as levels of atmospheric carbon dioxide increase, thus lowering the ocean pH and altering the carbonate system. In this laboratory study, we evaluated the physiological responses of juvenile mussels Mytilus galloprovincialis from Galician waters (NW Iberian Peninsula) exposed to control (500 µatm) and elevated (800 or 1200 µatm) seawater pCO2 conditions under 2 different feeding regimes (optimal and suboptimal). Shell properties such as compressive strength and composition (organic matter and aragonite:calcite ratio) were negatively affected by high seawater pCO2, regardless of food availability. This result suggests that water chemistry is a main driver for shell development. Under the optimal feeding regime, mussel feeding rates increased in response to elevated pCO2, presumably as a strategy to maintain a high strength of attachment. In contrast, mussels on the suboptimal diet showed weak attachment and narrow valve opening at the highest pCO2 condition. Thus, our results suggest that with optimal food availability, mussels were resilient to water acidification with respect to feeding activity, valve opening and attachment strength. Under a suboptimal diet, however, the ability of mussels to respond to acidification was compromised. These results highlight complex ecophysiological interactions for calcifying organisms subjected to climate change ; This study was funded by the Spanish government through the Ministerio de Economía y Competitividad that included European FEDER funds (projects Ref. AGL-2013-45945-R, CTM2016-76146-C3-2-R/ CTM2016- 76146-C3-1-R). J.L. acknowledges funding from the Spanish National Research Council (CSIC) through the Program ICOOP+ 2016 (Ref. ICOOPA20147) ; Peer reviewed

16 pages, 6 figures, 1 table.-- This work is distributed under the Creative Commons Attribution 4.0 License ; We present the distribution of water masses along the GEOTRACES-GA01 section during the GEOVIDE cruise, which crossed the subpolar North Atlantic Ocean and the Labrador Sea in the summer of 2014. The water mass structure resulting from an extended optimum multiparameter (eOMP) analysis provides the framework for interpreting the observed distributions of trace elements and their isotopes. Central Waters and Subpolar Mode Waters (SPMW) dominated the upper part of the GEOTRACESGA01 section. At intermediate depths, the dominant water mass was Labrador Sea Water, while the deep parts of the section were filled by Iceland–Scotland Overflow Water (ISOW) and North-East Atlantic Deep Water. We also evaluate the water mass volume transports across the 2014 OVIDE line (Portugal to Greenland section) by combining the water mass fractions resulting from the eOMP analysis with the absolute geostrophic velocity field estimated through a box inverse model. This allowed us to assess the relative contribution of each water mass to the transport across the section. Finally, we discuss the changes in the distribution and transport of water masses between the 2014 OVIDE line and the 2002–2010 mean state. At the upper and intermediate water levels, colder end-members of the water masses replaced the warmer ones in 2014 with respect to 2002–2010, in agreement with the long-term cooling of the North Atlantic Subpolar Gyre that started in the mid-2000s. Below 2000 dbar, ISOW increased its contribution in 2014 with respect to 2002–2010, with the increase being consistent with other estimates of ISOWtransports along 58–59 N.We also observed an increase in SPMW in the East Greenland Irminger Current in 2014 with respect to 2002–2010, which supports the recent deep convection events in the Irminger Sea. From the assessment of the relative water mass contribution to the Atlantic Meridional Overturning Circulation (AMOC) across the OVIDE line, we conclude that the larger AMOC intensity in 2014 compared to the 2002–2010 mean was related to both the increase in the northward transport of Central Waters in the AMOC upper limb and to the increase in the southward flow of Irminger Basin SPMW and ISOW in the AMOC lower limb. ; For this work Maribel I. García-Ibáñez and Fiz F. Pérez were supported by the Spanish Ministry of Economy and Competitiveness through the BOCATS (CTM2013-41048-P) project, co-funded by the Fondo Europeo de Desarrollo Regional 2014–2020 (FEDER). Maribel I. García-Ibáñez was also supported by the Centre for Climate Dynamics at the Bjerknes Centre. Pascale Lherminier was supported by IFREMER. Patricia Zunino was supported by CNRS and IFREMER, within the framework of the projects AtlantOS (H2020-633211) and GEOVIDE (ANR-13-BS06-0014-02). Herlé Mercier was supported by CNRS and the AtlantOS H2020 project under grant number 633211. Paul Tréguer was supported by the LABEX-Mer (French Government "Investissement d'Avenir" programme, ANR-10-LABX-19-01) ; Peer reviewed