C Fontanier

D Dissard

L Ruffine

B Mamo

E Ponzevera

E Pelleter

F Baudin

A Roubi

S Chéron

A Boissier

N Gayet

S Bermell-Fleury

M Pitel

V Guyader

F Lesongeur

F Savignac

Living (stained) deep-sea foraminifera from the Sea of Marmara: A preliminary study

In this preliminary study, we investigate living (stained) foraminifera from the Sea of Marmara. We focus on the faunal composition and geochemical signatures (trace elements, carbon and oxygen stable isotopes) in foraminiferal tests at two deep-sea sites (329 and ~1240 m depth respectively). Documented by ROV observations and sampling, both study areas are heterogeneous (including bacterial mats and carbonate concretions), proximal to cold seeps and consist of dysoxic bottom water (O 2 < 20 µmol/L). The prevailing dysoxia at both study areas restricts foraminiferal diversity to very low values (S < 9, H' < 0.97). Stress-tolerant species Bolivina vadescens and Globobulimina affinis dominate living faunas at both sites. The highest foraminiferal standing stock is recorded at the shallowest site underneath a spreading bacterial mat. No benthic foraminifera from either site possess geochemical signatures of methane seepage. Our biogeochemical results show that use of foraminiferal Mn/Ca ratios as a proxy for bottom water oxygenation depends strongly on regional physiography, sedimentary processes and water column structure.

Introduction

Hydrocarbon seeps represent benthic environments of major interest to scientists regarding biogeochemical functioning and fluid generation/migration along continental margins, and deep-sea biodiversity in extreme ecosystems (e.g., [START_REF] Boetius | Seafloor oxygen consumption fuelled by methane from cold seeps[END_REF]. Research into these unique ecosystems is additionally of interest to mining industries seeking to exploit the rich gas reserves of hydrocarbon seeps [START_REF] Sills | The significance of gas for offshore operations[END_REF][START_REF] Fleischer | Distribution of free gas in marine sediments: a global overview[END_REF][START_REF] Prinzhofer | Origins of hydrocarbon gas seeping out from offshore mud volcanoes in the Nile delta[END_REF]. Most seeps are characterized by methane and hydrogen sulfide (e.g., [START_REF] Borowski | Global and local variations of interstitial sulphate gradients in deep-water, continental margin sediments: sensitivity to underlying methane and gas hydrates[END_REF][START_REF] Campbell | Hydrocarbon seep and hydrothermal vent paleoenvironments and paleontology: past developments and future research directions[END_REF] forming a brine which sustains chemosynthetic communities of endemic metazoa (e.g., vesicomyid, mytilid or siboglinid) and mutually endosymbiotic prokaryotes (mainly sulfide-oxidizing bacteria) (e.g., [START_REF] Sibuet | Biogeography, biodiversity and fluid dependence of deep-sea cold-seep communities at active and passive margins[END_REF][START_REF] Boetius | A marine microbial consortium apparently mediating anaerobic oxidation of methane[END_REF][START_REF] Sahling | Community structure at gas hydrate deposits at the Cascadia convergent margin, NE Pacific[END_REF][START_REF] Levin | Community structure and nutrition of deep methaneseep macrobenthos from the North Pacific (Aleutian) Margin and the Gulf of Mexico (Florida Escarpment)[END_REF]. Variation in sulfide and methane fluxes within the uppermost sediments generate a distinct biozonation of chemoautotrophic prokaryotes and a patchy distribution of benthic eukaryotes (e.g., [START_REF] Sibuet | Biogeography, biodiversity and fluid dependence of deep-sea cold-seep communities at active and passive margins[END_REF][START_REF] Sahling | Community structure at gas hydrate deposits at the Cascadia convergent margin, NE Pacific[END_REF][START_REF] Foucher | Structure and drivers of cold seep ecosystems[END_REF].

Living benthic Foraminifera (Eukaryota, Rhizaria) from modern cold seeps have been investigated over the last two decades [START_REF] Akimoto | Recent benthic foraminiferal assemblages from the cold seep communities -a contribution to the methane gas indicator[END_REF][START_REF] Gupta | Benthic foraminifera of bathyal hydrocarbon vents of the Gulf of Mexico: initial report on communities and stable isotopes[END_REF][START_REF] Kitazato | Benthic foraminifera associated with cold seepages: discussion of their faunal characteristics and adaptations[END_REF][START_REF] Gupta | Foraminiferal colonization of hydrocarbon-seep bacterial mats and underlying sediment, Gulf of Mexico slope[END_REF], 2007;[START_REF] Rathburn | Benthic foraminifera associated with cold methane seeps on the northern California margin: ecology and stable isotopic composition[END_REF][START_REF] Rathburn | Relationships between the distribution and stable isotopic composition of living benthic foraminifera and cold methane seep biogeochemistry in Monterey Bay, California[END_REF][START_REF] Bernhard | Monterey Bay cold-seep biota: assemblages, abundance, and ultrastructure of living foraminifera[END_REF] ⁎ Corresponding author at: Université de Bordeaux, CNRS, Environnements et Paléo-environnements Océaniques et Continentaux,Continentaux, UMR 5805, F-33600 Pessac, France.

E-mail address: c.fontanier@foram.eu.com (C. Fontanier).

T [START_REF] Torres | Is methane venting at the seafloor recorded by δ 13 C of benthic foraminifera shells?[END_REF][START_REF] Hill | Isotopic evidence for the incorporation of methane-derived carbon into foraminifera from modern methane seeps, Hydrate Ridge, Northeast Pacific[END_REF][START_REF] Heinz | Living benthic foraminifera in sediments influenced by gas hydrates at the Cascadia convergent margin, NE Pacific[END_REF][START_REF] Panieri | Foraminiferal response to an active methane seep environment: a case study from the Adriatic Sea[END_REF][START_REF] Mackensen | Low δ 13 C in tests of live epibenthic and endobenthic foraminifera at a site of active methane seepage[END_REF][START_REF] Lobegeier | Foraminifera of hydrocarbon seeps: gulf of Mexico[END_REF]Fontanier et al., 2014a;[START_REF] Herguera | Limits to the sensitivity of living foraminifera to pore water carbon isotope anomalies in methane vent environments[END_REF][START_REF] Wollenburg | Novel high-pressure culture experiments on deep-sea benthic foraminiferaevidence for methane seepage-related δ 13 C of Cibicides wuellerstorfi[END_REF]. Foraminiferal species living in cold seep ecosystems are not endemic/ exotic but are recruited from adjacent non-seep zones (e.g., [START_REF] Gupta | Benthic foraminifera of bathyal hydrocarbon vents of the Gulf of Mexico: initial report on communities and stable isotopes[END_REF][START_REF] Kitazato | Benthic foraminifera associated with cold seepages: discussion of their faunal characteristics and adaptations[END_REF][START_REF] Gupta | Foraminiferal colonization of hydrocarbon-seep bacterial mats and underlying sediment, Gulf of Mexico slope[END_REF][START_REF] Rathburn | Benthic foraminifera associated with cold methane seeps on the northern California margin: ecology and stable isotopic composition[END_REF][START_REF] Rathburn | Relationships between the distribution and stable isotopic composition of living benthic foraminifera and cold methane seep biogeochemistry in Monterey Bay, California[END_REF][START_REF] Lobegeier | Foraminifera of hydrocarbon seeps: gulf of Mexico[END_REF]Fontanier et al., 2014a;[START_REF] Herguera | Limits to the sensitivity of living foraminifera to pore water carbon isotope anomalies in methane vent environments[END_REF]. A wide array of metabolic adaptations (facultative anaerobic metabolism, mutualism with prokaryotes), habitat and food preference (elevated epibiotic habitat, bacteriovore) explain foraminiferal occurrence in methane-and sulfide-enriched sediments (e.g., [START_REF] Bernhard | Monterey Bay cold-seep biota: assemblages, abundance, and ultrastructure of living foraminifera[END_REF][START_REF] Panieri | Foraminiferal response to an active methane seep environment: a case study from the Adriatic Sea[END_REF][START_REF] Mackensen | Low δ 13 C in tests of live epibenthic and endobenthic foraminifera at a site of active methane seepage[END_REF][START_REF] Gupta | Attachment of foraminifera to vestimentiferan tubeworms at cold seeps: refuge from seafloor hypoxia and sulfide toxicity[END_REF][START_REF] Lobegeier | Foraminifera of hydrocarbon seeps: gulf of Mexico[END_REF]. The δ 13 C values in (living) foraminiferal tests record the seepage of methane-enriched fluid, with a clear shift (several per mil units) to lower signatures compared to adjacent non-seep areas (Sen [START_REF] Gupta | Benthic foraminifera of bathyal hydrocarbon vents of the Gulf of Mexico: initial report on communities and stable isotopes[END_REF][START_REF] Rathburn | Benthic foraminifera associated with cold methane seeps on the northern California margin: ecology and stable isotopic composition[END_REF][START_REF] Rathburn | Relationships between the distribution and stable isotopic composition of living benthic foraminifera and cold methane seep biogeochemistry in Monterey Bay, California[END_REF][START_REF] Hill | Isotopic evidence for the incorporation of methane-derived carbon into foraminifera from modern methane seeps, Hydrate Ridge, Northeast Pacific[END_REF][START_REF] Mackensen | Low δ 13 C in tests of live epibenthic and endobenthic foraminifera at a site of active methane seepage[END_REF]Fontanier et al., 2014a;[START_REF] Wollenburg | Novel high-pressure culture experiments on deep-sea benthic foraminiferaevidence for methane seepage-related δ 13 C of Cibicides wuellerstorfi[END_REF]. The lack of major δ 13 C isotopic variability recorded in living foraminiferal tests from methane-rich seep zones vs. hydrate-gas fluids, leads to the assumption that foraminifera mostly calcify during periods of low methane discharge or during intermittent episodes of seawater injection into the sediment [START_REF] Torres | Is methane venting at the seafloor recorded by δ 13 C of benthic foraminifera shells?[END_REF][START_REF] Panieri | Foraminiferal response to an active methane seep environment: a case study from the Adriatic Sea[END_REF]Fontanier et al., 2014a). Furthermore, 13 C-depleted food sources (e.g., methanotroph bacterial biomass) and/or prokaryotic symbionts may contribute to the observed carbon isotope depletion in foraminiferal shells (Sen [START_REF] Gupta | Benthic foraminifera of bathyal hydrocarbon vents of the Gulf of Mexico: initial report on communities and stable isotopes[END_REF][START_REF] Rathburn | Relationships between the distribution and stable isotopic composition of living benthic foraminifera and cold methane seep biogeochemistry in Monterey Bay, California[END_REF][START_REF] Hill | Isotopic evidence for the incorporation of methane-derived carbon into foraminifera from modern methane seeps, Hydrate Ridge, Northeast Pacific[END_REF][START_REF] Panieri | Foraminiferal response to an active methane seep environment: a case study from the Adriatic Sea[END_REF][START_REF] Mackensen | Low δ 13 C in tests of live epibenthic and endobenthic foraminifera at a site of active methane seepage[END_REF]. [START_REF] Panieri | Foraminiferal response to an active methane seep environment: a case study from the Adriatic Sea[END_REF] has documented lighter protoplasmic δ 13 C (-21.4‰) for foraminifera living in hydrocarbon seeps compared to a non-seep adjacent area, suggesting that bacterial mats like Beggiatoa (prokaryotes) (with δ 13 C comprised between to -25.5 and -21.5‰) are a foraminiferal food source. The concentration of trace elements within foraminiferal tests is considered a reliable proxy for a wide array of environmental parameters (e.g., temperature, carbonate chemistry, organic matter flux) (e.g. [START_REF] Nurnberg | Assessing the reliability of magnesium in foraminiferal calcite as a proxy for water mass temperatures[END_REF][START_REF] Lea | Trace elements in foraminiferal calcite[END_REF]Dissard et al., 2010a, b;[START_REF] Munsel | Heavy metal incorporation in foraminiferal calcite: results from multi-element enrichment culture experiments with Ammonia tepida[END_REF]. Therefore trace-metal composition within foraminiferal tests may be considered a relevant proxy for methane seepages and sulfate reduction.

In this study, we investigate living (stained) foraminifera from the Sea of Marmara. We focus on faunal composition and geochemical signatures (trace elements, carbon and oxygen stable isotopes) in foraminiferal tests from two deep-sea sites sampled with the ROV 'Victor 6000' (MARSITE Cruise aboard the RV "Pourquoi Pas?", November 2014) (Fig. 1, Table 1). Both study areas, located in the Central High and the south Çinarcik Basin (at 329 and ~1240 m depth respectively), are entrenched by dysoxic bottom waters (O 2 < 20 µmol/L) (Fig. 2; Table 1). Very high-resolution bathymetry, geophysical, geological and geochemical data have revealed that the Sea of Marmara is characterized by hydrocarbon seeps where methane is overwhelmingly present, but have differing origins (e.g., [START_REF] Çağatay | Pore-water and sediment geochemistry in the Marmara Sea (Turkey): early diagenesis and diffusive fluxes[END_REF][START_REF] Halbach | Migration of the sulphatemethane reaction zone in marine sediments of the Sea of Marmaracan this mechanism be tectonically induced[END_REF][START_REF] Géli | Gas emissions and active tectonics within the submerged section of the North Anatolian Fault zone in the Sea of Marmara[END_REF][START_REF] Zitter | Cold seeps along the main Marmara fault in the Sea of Marmara (Turkey)[END_REF][START_REF] Bourry | Free gas and gas hydrates from the Sea of Marmara, Turkey Chemical and structural characterization[END_REF][START_REF] Chevalier | Authigenic carbonates at cold seeps in the Marmara Sea (Turkey): a lipid biomarker and stable carbon and oxygen isotope investigation[END_REF][START_REF] Crémière | Methane-derived authigenic carbonates along the North Anatolian fault system in the Sea of Marmara (Turkey)[END_REF]. The Central High is characterized by fluid emissions enriched in thermogenic methane whereas the south Çinarcik Basin is preferentially supplied with biogenic (microbial-derived) gas [START_REF] Bourry | Free gas and gas hydrates from the Sea of Marmara, Turkey Chemical and structural characterization[END_REF]. The objectives of our study are: (1) to compare the living benthic communities (Foraminifera, Prokaryota) between both stations and (2), to investigate the putative geochemical imprint of seeps environments in living foraminiferal tests through trace element (i.e., Mn/Ca, Mg/Ca, Sr/Ca, Ba/Ca) and stable isotopes (δ 13 C, δ 18 O) analyses.

Study area

The Sea of Marmara is a highly-faulted sedimentary basin located within Turkish territory between the Mediterranean and Black Seas (Fig. 1). The boundary between the Anatolian plate and the Eurasian plate, the North Anatolian Fault (NAF), crosses the Sea of Marmara in an approximately east-west direction. Composed of different segments, it has generated several major earthquakes during the twentieth century; the most recent one being the Mw = 7.4 Izmit earthquake in August 1999 [START_REF] Karabulut | The seismicity in the Eastern Marmara Sea after the 17 August 1999 Izmit earthquake[END_REF][START_REF] Kuşçu | Seafloor gas seeps and sediment failures triggered by the August 17, 1999 earthquake in the Eastern part of the Gulf of Izmit, Sea of Marmara, NW Turkey[END_REF][START_REF] Carton | Seismic imaging of the three dimensional architecture of the Cınarcık Basin along the North Anatolian Fault[END_REF][START_REF] Gasperini | How far did the surface rupture of the 1999 Izmit earthquake reach in Sea of Marmara? Tectonics[END_REF] (Fig. 1). The Sea of Marmara is characterized by three main basins which from east to west are called the Çinarcik Basin, the Central Basin and the Tekirdağ Basin. These basins are about 1250 m deep and separated from each other by bathymetric highs. The Central and Western Highs (Fig. 1) have been described as transpressional structures resulting from the overall strain of the NAF [START_REF] Okay | An active, deep marine strike-slip basin along the North Anatolian fault in Turkey[END_REF].

Two distinct layers can be observed in the Sea of Marmara water column (e.g., [START_REF] Beşiktepe | The Circulation and Hydrography of the Marmara Sea[END_REF]. The southward Bosphorus jet, flowing from the Black Sea into the Sea of Marmara mainly drives the upper layer (20-30 m thick) with brackish waters [START_REF] Alavi | Late Holocene Deep-Sea Benthic Foraminifera from the Sea of Marmara[END_REF] and seasonal surface temperatures of 3-25 °C. Denser Mediterranean waters enter the Sea of Marmara from the Aegean Sea through the Dardanelles Strait as a turbulent, buoyant plume and form the subhalocline basin waters [START_REF] Beşiktepe | The Circulation and Hydrography of the Marmara Sea[END_REF]. In the Çinarcik Basin, this water mass, characterized by high and relatively homogeneous salinity (= 38.7 psu), constant temperature (~14.4 °C) and low oxygen (< 20 µmol/L), remains relatively stagnant over long periods of time, while the Tekirdağ Basin's waters are frequently renewed [START_REF] Alavi | Late Holocene Deep-Sea Benthic Foraminifera from the Sea of Marmara[END_REF] (Fig. 2). This generates more pronounced minimum salinity and oxygen conditions in the bottom waters of the Çinarcik Basin (Fig. 2) [START_REF] Alavi | Late Holocene Deep-Sea Benthic Foraminifera from the Sea of Marmara[END_REF]. The primary productivity in the Sea of Marmara is about 70 g C/m 2 /yr (Ünlüata and Özsoy, 1986) triggered by Black Sea surface-water nutrients, vertical mixing and local photic zone recycling [START_REF] Bastürk | Oceanography of the Turkish Straits[END_REF].

To our knowledge, there are no publications regarding the living deep-sea foraminifera from the Sea of Marmara. To date, only a few studies have dealt with dead/fossil foraminifera from the deep basins [START_REF] Alavi | Late Holocene Deep-Sea Benthic Foraminifera from the Sea of Marmara[END_REF][START_REF] Çağatay | Late Glacial-Holocene palaeoceanography of the Sea of Marmara: timing of connections with the Mediterranean and the Black Sea[END_REF][START_REF] Kaminski | Late Glacial to Holocene benthic foraminifera in the Marmara Sea: implications for Black Sea-Mediterranean Sea connections following the last deglaciation[END_REF][START_REF] Kirci-Elmas | Palaeoenvironmental Investigation of Sapropelic Sediments from the Marmara Sea: a biostratigraphic approach to palaeoceanographic history during the last Glacial-Holocene[END_REF]. [START_REF] Alavi | Late Holocene Deep-Sea Benthic Foraminifera from the Sea of Marmara[END_REF] examined fossil foraminiferal assemblages in two long sediment cores collected in the Çinarcik Basin at a depth of 1200 m. Both archives were characterized by moderate to high organic carbon content (1.0-1.8% dry weight). Fossil faunas were typical of oxygen-depleted and organic matter-enriched environments. They were dominated by Melonis pompilioides, Chilostomella mediterranensis, Brizalina alata, Brizalina spathulata and Bulimina inflata. Çağatay et al. (2000), reported the timing of Late Glacial-Holocene connections between the Mediterranean and Black Seas where two Holocene Sea of Marmara basin archives (370 and 700 m depths) yielded deep-sea fossil foraminifera. Organic matter-enriched intervals (i.e., sapropelic layers), which documented the establishment of water-column stratification and water column hypoxia (10,600 years BP), were characterized by Buliminids (Bulimina aculeatea, B. inflata), Bolivinids (B. spathulata, B. dilatata, B. alata), Cassidulina crassa and Hyalinea balthica (Çağatay et al., 2000). [START_REF] Kaminski | Late Glacial to Holocene benthic foraminifera in the Marmara Sea: implications for Black Sea-Mediterranean Sea connections following the last deglaciation[END_REF] studied Holocene foraminiferal assemblages in four gravity cores gathered between 64 and 549 m and also focused on marine connections between the Marmara, Aegean and Black Seas. At the deepest station located in the western Sea of Marmara, they recorded the dominance of Fursenkoina with Brizalina and Bulimina at the base of the sapropelic layers [START_REF] Kaminski | Late Glacial to Holocene benthic foraminifera in the Marmara Sea: implications for Black Sea-Mediterranean Sea connections following the last deglaciation[END_REF]. Sapropel layers themselves were barren of foraminifera, or contained few individuals of Chilostomella, Bolivina, Brizalina and Globobulimina. [START_REF] Kirci-Elmas | Palaeoenvironmental Investigation of Sapropelic Sediments from the Marmara Sea: a biostratigraphic approach to palaeoceanographic history during the last Glacial-Holocene[END_REF] 1 and2. Black stars correspond to CTD casts (MNT_CTD3 and MNT_CTD10), taken during the MARNAUT cruise (2007) (data available online at http://www.ifremer.fr/sismer/index_FR.htm).

Table 1

Coordinates and sampling depth of all push cores investigated in this paper. Push cores were gathered with the ROV 'Victor 6000' during the MARSITE cruise (November 2014). Physicochemical parameters including BWT (bottom-water temperature), BWS (bottom-water salinity) and BWO (bottom-water oxygenation) were extrapolated from two CTD casts achieved during the MARNAUT cruise (*) (data available at http://www.ifremer.fr/sismer/index_FR.htm). Bottom-water oxygen (BWO), Oxygen saturation, bottom-water oxygen at saturation (BWO sat ) and apparent oxygen utilization (AOU) were calculated using http://ocean.ices.dk/Tools/Calculator.aspx. The δ 13 C of dissolved inorganic carbon in bottom water (δ 13 C DIC ) was calculated using Kroopnick's equation [START_REF] Kroopnick | The distribution of δ 13 C of ΣCO2 in the world oceans[END_REF]. The δ 18 O of bottom water (δ 18 O BW ) is described in [START_REF] Rank | Oxygen-18, deuterium and tritium in the Black Sea and the Sea of Marmara[END_REF]. The δ 13 C of authigenic carbonate collected at both study sites (δ 13 C-CaCO 3 ) is presented in [START_REF] Chevalier | Authigenic carbonates at cold seeps in the Marmara Sea (Turkey): a lipid biomarker and stable carbon and oxygen isotope investigation[END_REF]. The δ 18 O of equilibrium calcite (δ 18 O e.c. ) was calculated by following equations by [START_REF] O'neil | Oxygen isotope fractionation in divalent metal carbonates[END_REF] and [START_REF] Friedman | Compilation of stable isotope fractionations factors of geochemical interest (Geological Survey Professional Paper 440-KK)[END_REF]. The δ 13 C of methane characterizing active seeps on both study areas is described in [START_REF] Bourry | Free gas and gas hydrates from the Sea of Marmara, Turkey Chemical and structural characterization[END_REF]

Material and methods

Sediment cores

Push cores were collected using the remote operated vehicle (ROV) Victor 6000 during two dives located on the Central High (MRS-DV592-01 at 329 m water depth) and in the Çinarcik Basin (MRS-DV596-05 at ~1240 m water depth) (Fig. 1) (Table 1). Both areas had been previously explored on several occasions (e.g., [START_REF] Géli | Gas emissions and active tectonics within the submerged section of the North Anatolian Fault zone in the Sea of Marmara[END_REF][START_REF] Zitter | Cold seeps along the main Marmara fault in the Sea of Marmara (Turkey)[END_REF]. A 25 cm-long Plexiglas liner of 5.4 cm internal diameter was used within the corer to collect sediment samples (Fig. 3). Cores MRS-DV01-PC-02 and MRS-DV01-PC-04 were recovered on the Central High, and cores MRS-DV05-PC-04 and MRS-DV05-PC-06 in the Çinarcik Basin (Table 1). Color video was recorded on the ROV with the aim of providing a visual description of the sampling environment (Fig. 3). Two long cores, MRS-CS-04 (638 cm long) and MRS-CS-17 (1050 cm long), were also recovered with a Calypso piston corer at the two sites to analyze major and minor elemental content of pore waters (Table 2).

The Calypso cores additionally provided an environmental overview of the Central High and the south Çınarcık Basin in terms of major diagenetic processes. Readers should keep in mind that the MRS-CS-17 calypso core and the MRS-DV05-PC-04 push core are located 4.8 km away from the MRS-DV05-PC-06 push core used for foraminiferal investigations.

Benthic foraminiferal analysis

Each push core dedicated to foraminiferal study (MRS-DV01-PC-04 and MRS-DV05-PC-06) was sampled every 0.5 cm from the sedimentwater interface to 2 cm, and then every centimetre between 2-5 cm. Sediment samples were transferred into 250 cm 3 bottles, which were filled with 95% ethanol containing 2 g/L Rose Bengal stain, commonly used to identify live foraminifera [START_REF] Murray | Mortality, protoplasm decay rate, and reliability of staining techniques to recognize "living" foraminifera: a review[END_REF][START_REF] Walton | Techniques for recognition of living Foraminifera[END_REF]. All samples were gently shaken for several minutes to obtain a homogeneous mixture. One month after the cruise, samples were sieved through 63 and 125 µm sieves and the sieved residues were stored in 95% ethanol. Because Rose Bengal might stain the protoplasm of dead foraminifera preserved under the generally prevailing anoxic sediment conditions [START_REF] Corliss | Distribution of Rose Bengal stained deep-sea benthic foraminifera from the Nova Scotia continental margin and Gulf of Maine[END_REF][START_REF] Bernhard | Distinguishing live from dead foraminifera: methods review and proper applications[END_REF], only fully stained foraminifera (all chambers except the last one stained bright pink) belonging to both size fraction (i.e., 63 µm and > 125 µm) were sorted out from wet samples and stored in Plummer cells. Strict staining criteria were applied and doubtful individuals without perfectly stained tests were not included. Most live foraminifera were identified at species level (see Appendices A-B). At each station, we calculated diversity indices including species richness S (representing the number of taxa), Shannon index H' (log base e), Evenness Index E, Dominance Index D and Berger-Parker Index [START_REF] Hayek | Surveying Natural Populations[END_REF][START_REF] Murray | Ecology and Applications of Benthic Foraminifera[END_REF] (Table 3). We obtained digital photographs of major species using a scanning electron microscope at Ifremer (FEI QUANTA 200 equipped with an Oxford Instrument Energy Dispersive Spectroscopy) (Fig. 4).

Trace elements analysis in foraminiferal tests

Because foraminifera were presumed alive (stained) at collection, the rigorous cleaning procedure required for dead/fossil specimens was not necessary. Instead, the modified cleaning procedure described in [START_REF] Dissard | Effect of the fluorescent indicator calcein on Mg and Sr incorporation into foraminiferal calcite[END_REF]Dissard et al. ( , 2010a,b,b) was adopted. Organic matter was removed by soaking specimens for 30 min in a 3-7% NaOCl solution before analysis [START_REF] Gaffey | Effects of bleaching on organic and mineral phases in biogenic carbonates[END_REF]. A stereomicroscope was used during the cleaning procedure to check optically for contamination and possible damage to the foraminiferal tests. Specimens were removed from the cleaning solution directly after complete bleaching. After cleaning, samples were thoroughly rinsed with deionized water to ensure complete removal of reagents. Individuals belonging to foraminiferal species Globobulimina affinis and Bolivina vadescens were selected for trace element analysis (Appendix C). Only the last chamber (F) was investigated. Single chambers were ablated using an Nd-YAG Laser (NWR-213, New Wave, ESI) inside an ablation chamber flushed with Helium (0.7 L/min). Then the ablated sample with Helium was mixed with an Argon flow (0.6 L/min) and transported to an Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Pulse repetition rate was set at 10 Hz, with an energy density at the sample surface of 30 J/cm 2 . Ablation craters were 50 µm in diameter and ablated material was analyzed with respect to time (and hence depth) using an ICP-MS (7500cx Agilent). Due to chamber size limitations, only one measurement was performed per F chamber for B. vadescens specimens but two ablations were performed on G. affinis F chambers. Average values of these measurements are presented in Appendix C. Analyses were calibrated against NIST SRM 610 glass, using the concentration data of [START_REF] Pearce | A compilation of new and published major and trace elements data for NIST SRM 610 and NIST SRM 612 glass reference materials[END_REF] with 43 Ca as an internal standard. Concentrations of Mg, Sr, Ba and Mn were calculated using 24 Mg, 88 Sr, 138 Ba and 55 Mn. An in-house matrix matched carbonate standard was used to verify potentially different ablation behavior for glass and carbonate. Simultaneously monitoring the Al allowed us to discard contaminated profiles, or part of the profiles, from further elemental concentration calculations.

Isotopic measurements (δ 13 C and δ 18 O) on foraminiferal tests

Globobulimina affinis and Bolivina vadescens were selected for stable isotope measurements (Table 4). Bulk foraminifera samples were reacted with orthophosphoric acid at 70 °C for 180 s in individual vessels with an automated cryogenic distillation system (Kiel IV device), interfaced with a DeltaVAdvantage Isotope Ratio Mass Spectrometry (IRMS). Over the period of analysis, 20 runs of our laboratory's internal carbonate standard (Marbre LM) gave an average δ 13 C value of 2.117‰ ± 0.022‰ (< 0.03‰) (k = 1) (theoretical value normalized to NBS 19 = 2.13‰) and an average δ 18 O value of -1.865‰ ± ± 0.051‰ (< 0.06‰) (k = 1) (theoretical value normalized to NBS 19 = -1.83‰). The analytical precision within each run, calculated from 1 to 20 measurements of the standard Marbre LM, varies from 2.079 to 2.162‰ for δ 13 C and from -1.769 to -1.949‰ for δ 18 O. Fig. 3. A. Video stills of push core sampling at Central High (Dive MSR-DV592-01, depth 329 m). Dedicated to sedimentary organic matter investigation, push core MRS-DV01-PC-02 is indicated by a single red asterisk. Push core MRS-DV01-PC-04 was dedicated to foraminiferal investigation and is indicated by two red asterisks. Note the large, white filamentous microbial mat. B, C. Stereoscopic views of sieve residues (> 125 µm) collected at push core site MRS-DV01-PC-04 (depth 329 m). "M" indicates a carbonate mudclast. D. Video stills of push core sampling at the south Çinarcik Basin (Dive MSR-DV596-05, push core MRS-DV05-PC-06, depth 1247 m). Note the carbonate crust in the background and patchy coloration of surface sediment. E, F. Stereoscopic views of sieve residues (> 125 µm) collected at push core site MRS-DV05-PC-06. "F" indicates dead foraminifera; "P" indicates pyrite; "PF" pyritised foraminifera; "Q" quartz grain and "L" lithoclast.

Pore water analysis

Pore waters were collected immediately after Calypso core retrieval with 5 or 10 cm rhizon samplers consisting of a hydrophilic, porous polymer tube 2.5 mm in diameter (MOM, Rhizospshere) [START_REF] Seeberg-Elverfeldt | Rhizon sampling of pore waters near the sediment/water interface of aquatic systems[END_REF]. Samples were collected every 20-30 cm in 10 mL cleaned syringes then transferred to 15 mL HDPE acid-cleaned vials. Sample splits for various analyses were performed under a laminar air flow bench before acidification with 15 µL concentrated HNO 3 (Ultrex II, JT Baker) onboard. Major dissolved elements ([SO 4

2-],

[Mg 2+ ]) were analyzed by ionic chromatography with a Dionex ICS-5000. The resulting concentrations were obtained within ± 1% accuracy with reference to the IAPSO seawater standard. [Sr 2+ ], [Mn 2+ ], [Ba 2+ ] were measured by High Resolution Inductively Coupled Plasma Mass Spectrometry (HR-ICP-MS) (Element 2, Thermofisher) at Pole Spectrometrie Ocean (PSO, IUEML Brest). Sample volumes of 0.120 mL were diluted 25 times prior to introduction into the ICPMS. Calibrations were done in two ways; for Sr, a standard addition method was done with gravimetric standards at 4, 5.8, 11.8 and 15.5 mg/L. For Mn and Ba, a seawater standard NASS-5 (CNRC) with reported values ([Mn 2+ ] = 0.919 µg/L, NRCC certificate and [Ba 2+ ] = 5.1 µg/L) was employed (Field et al., 2007). Total alkalinity was evaluated using the HCl titration method (Titrino 888, Metrohm). For each measurement series, the pH-meter was calibrated with buffers pH 4 and 7 and the method's accuracy was evaluated using a seawater standard with certified alkalinity (Batch 123, University of San Diego, SCRIPPS). Calibrated aliquots of 0.1 M HCl were added to a sample volume of 1 mL until a pH of 4.3. Measurements of "Batch 123" gave A T = 2232 ± 220 µmol/kg (1sd, n = 10 over 10 days) in coherence with the certified value (A T = 2225.21 ± 0.34 µmol/kg).

Rock-Eval pyrolysis

Five samples from core MRS-DV01-PC-02 and four samples from core MRS-DV05-PC-04 were analyzed via the Rock-Eval thermal analysis technique, using a RE6 Turbo device (Vinci Technologies). Details of the RE6 apparatus are described in [START_REF] Behar | Rock-Eval 6 technology: performances and developments[END_REF]. Analyses were carried out using the basic operating principles for testing recent marine sediments [START_REF] Baudin | Guidelines for Rock-Eval analysis of recent marine sediments[END_REF]. The RE6 technique provided measurements from the sequential pyrolysis and oxidation of about 40 mg of desalted crushed sample. Briefly, this technique provides several fundamental parameters; the first peak (S1) corresponds mainly to free hydrocarbons that are volatilized for 3 min at 180 °C and detected by a Flame Ionization Detector (FID). The second peak (S2) represents hydrocarbons generated from kerogen cracking between 180 °C and 650 °C. The amounts of CO 2 and CO released during pyrolysis are detected by an infra-red (IR) cell and represent the S3 and S3CO peaks respectively. All these parameters are expressed in mg of hydrocarbons or CO 2 /CO per gram of rock. The temperature of maximum hydrocarbon yield by kerogen is called Tmax (in °C). The residual organic and inorganic carbon content (in wt%) is obtained by combustion in air from 300 °C to 850 °C. The CO 2 and CO issuing from this combustion are also detected by an IR cell and correspond to peaks S4 and S5 for CO 2 and peak S4CO for CO. From these basic parameters, the total organic carbon content (TOC, in wt%) is calculated as the sum of pyrolyzed and residual organic carbon. The hydrogen index (HI) corresponds to the quantity of pyrolyzable organic compounds from S2 relative total organic carbon (in mg HC.g -1 TOC) and the oxygen index (OI) to the S3 relative total organic carbon (in mg CO 2 .g -1 TOC). Finally, the mineral carbon (MinC) is also calculated on the basis S3' and S3'CO + S5 peaks. This MinC can be converted to CaCO 3 if we assume that all inorganic carbon is under the form of calcite or aragonite. The precision for the parameters is ± 0.1% for TOC, ± 0.05% for MinC, ± 2 °C for Tmax, ± 10 mg HC.g -1 TOC for HI and ± 5 mg CO 2 .g -1 TOC for OI. All results are reported in Table 5.

Results

Observations by ROV and sieve residues description

At the Central High site, the seafloor was characterized by a large bacterial mat composed of whitish microbial filaments (Fig. 3). Push core MRS-DV01-PC-01 sampled within this mat (Fig. 3A) and accordingly, sieve residues (> 125 µm) revealed Rose Bengal stained microbial filaments, but also abundant meiofauna and bioclasts (e.g., valves, radioles) (Fig. 3B-C). Filaments were abundant only in the first centimetre and concentrated within the first half centimetre. Some millimetric carbonate mudclasts were observed in the 2-3 cm interval. In the south Çinarcik Basin, the seafloor was characterized by protruding carbonate crusts surrounded by white to brown concretions and coarse sediments colored with black patches. Push core MRS-DV05-PC-06 was retrieved proximal to a carbonate crust (Fig. 3D). Sieve residues (> 125 µm) revealed large lithoclasts (related to various crystalline rocks), millimetric minerals (e.g., quartz), pyrite-enriched aggregates and pyritised foraminifera (Fig. 3E-F). The largest lithoclast (2 cm) was recorded between 2 and 4 cm depth.

Sedimentary organic matter in push cores

Total Organic Carbon (TOC) contents range from 1.3 to 2.9 wt% with higher values recorded in the south Çinarcik Basin (Table 7). Tmax values are always low (~418 °C on average). HI values fluctuate from 162 to 303 mg HC.g -1 TOC along the studied cores, whereas OI values range between 128 and 201 mg CO 2 .g -1 TOC.

Pore water geochemistry in Calypso cores

In the Central High, dissolved strontium is relatively constant (90 µM) along the core MRS-CS-04 (Fig. 5). Dissolved magnesium is 60 µM in the uppermost 2 m and decreases slightly to ~40 µM down to 4.7 m. Dissolved manganese shows a slight increase in the uppermost part of the core, with values reaching 16 µM at 30 cm depth. Dissolved barium is lower than 1 µM along the uppermost ~3 m and then increases abruptly to 30 µM at 4.7 m. Sulfate concentration remains relatively constant (~30 mM) along the uppermost meter of the core, and decreases gradually to reach an almost null value at 4.4 m depth. Alkalinity increases downcore from 3,000 μM to a 13000 μM

Table 4

Isotope analyses (δ 13 C and δ 18 O), sediment intervals and samples weights for stained foraminiferal specimens of Globobulimina affinis and Bolivina vadescens tested from both Central High and Çinarcik Basin (MRS-DV01-PC-04 and MRS-DV05-PC-06 cores respectively). The δ 13 C of dissolved inorganic carbon in bottom waters (δ 13 C DIC ) was calculated using Kroopnick's equation [START_REF] Kroopnick | The distribution of δ 13 C of ΣCO2 in the world oceans[END_REF]. The δ 18 O of equilibrium calcite (δ 18 O e.c. ) was calculated following equations by [START_REF] O'neil | Oxygen isotope fractionation in divalent metal carbonates[END_REF] and [START_REF] Friedman | Compilation of stable isotope fractionations factors of geochemical interest (Geological Survey Professional Paper 440-KK)[END_REF] In the south Çinarcik Basin, Sr(II) concentration decreases from 95 to 60 µM downcore along the uppermost 2 m (Fig. 5). Values then stay relatively close to ~60 µM down to 10 m. Mg(II) concentration is relatively constant (values ranging between 60 and 50 µM). Mn(II) content is close to 160 µmol/L at a depth of 10 cm, and decreases abruptly to 5 µM at 190 cm and deeper. Ba(II) is lower than 2 µM in the upper 1.3 m of core MRS-CS-17 but then increases with sediment depth to reach 47 µM at 8.9 m. Sulfate content decreases more abruptly than the shallower Central High site, with lower values recorded below 2.3 m. Alkalinity increases more rapidly from 6000 μM in the topmost sediment layer to 45,000 μM at 4.7 m.

Foraminiferal faunas

Standing stocks and diversity

The foraminiferal standing stocks of the 63 µm size fraction varies from 200 individuals/100 cm 2 at the south Çinarcik Basin site (MRS-DV05-PC-06, 1247 m; Fig. 6 and Table 3) to 5900 individuals/100 cm 2 at the Central High site (MRS-DV01-PC-04, 329 m depth; Fig. 6 and Table 3). In the larger size fraction (> 125 µm), standing stocks are lower with values of 35 individuals/100 cm 2 at the deeper Çinarcik Basin to 800 individuals/100 cm 2 at the Central High site. Species richness (S) is extremely low at both sites and varies from 2 species recorded in the 63 µm fraction at Çinarcik Basin to 9 species in the > 125 µm fraction at Central High (Fig. 7 and Table 3). The Shannon index (H') is generally low (< 1), with lower values recorded for the smaller fraction (0.29 at Central High site and 0.10 at Çinarcik Basin). Accordingly, Berger-Parker index and Dominance index values are higher for the 63 µm fraction than the > 125 µm at both stations (Fig. 6 and Table 3).

Foraminiferal composition and microhabitat

At the Central High station, stained Bolivina vadescens (94.5%) dominates the 63 µm fraction with Virgulinella fragilis the second most abundant species (2.5%). Their abundance peaks in the uppermost centimetre of sediment, common for shallow infaunal taxa (Fig. 7). In the larger size fraction (> 125 µm), Globobulimina affinis is the dominant species (79.9%) and occupies an intermediate to deep infaunal microhabitat. Virgulinella fragilis is again the second most abundant taxon (8.7%) with the same shallow infaunal distribution. Large B. vadescens (3.3%) specimens together with Chilostomella ovoidea (3.3%), another intermediate to deep infaunal species, were recorded (Fig. 7).

At the Çinarcik Basin station, B. vadescens (97.8%) dominates the 63 µm fraction and inhabits the same sediment range as Central High. In the large size fraction, G. affinis (50%) is dominant and inhabits an intermediate infaunal microhabitat. Bolivina vadescens accounts for 37% of the living fauna and occupies a shallow infaunal microhabitat. Chilostomella ovoidea (13%) is the third most abundant taxon (Fig. 7).

Geochemical signatures in foraminiferal tests

Trace elements

For Bolivina vadescens, Mg/Ca ratio ranges between 3.01-7.12 mmol/mol at the Central High station with an average value of 5.60 mmol/mol. Slightly higher values varying from 4.72 to 7.61 mmol/mol (average of 5.89 mmol/mol) are recorded at the Çinarcik Basin station (Fig. 8,Appendix C). Sr/Ca ratios at the Central High station vary from 1.05 to 1.47 mmol/mol with an average value of 1.37 mmol/mol. Sr/Ca ratios range between 1.18-1.62 mmol/mol with an average value of 1.44 mmol/mol at the Çinarcik Basin station. Mn/ Ca ratios show a remarkable difference between both sampling sites with values of 24-1012 μmol/mol at the Central High station (average of 427 μmol/mol), and Mn/Ca ratios of 730-5657 μmol/mol at the Çinarcik Basin (average of 2352 μmol/mol) (Fig. 8, Appendix C). Ba/Ca ratios are slightly higher at the Central High station with 5.99-67.73 μmol/mol with an average value of 34.2 μmol/mol compared to values of 6.01-28.84 μmol/mol at the Çinarcik Basin with an average of 13.57 μmol/mol.

For G. affinis, Mg/Ca and Sr/Ca ratios do not show any major difference between both sites. Mg/Ca ratios range from 14.35 to 16.42 mmol/mol (average of 15.06 mmol/mol) at Central High and from 14.24 to 18.51 mmol/mol (average of 16.31 mmol/mol) at Çinarcik Basin. Sr/Ca ratios vary from 1.12 to 1.25 mmol/mol (average of 1.19 mmol/mol) at Central High, and 1.17-1.26 mmol/mol (average of 1.22 mmol/mol) at Çinarcik Basin (Fig. 8; Appendix C). Mn/Ca ratios are higher in the Çinarcik Basin with 123.50-918.98 μmol/mol (average of 348.99 μmol/mol), compared to Central High with 17.23-59.39 μmol/mol (average of 41.69 μmol/mol) (Fig. 8; Appendix C). Ba/Ca ratios appear higher at Central High with values of 4.49-16.81 μmol/mol (average of 9.97 μmol/mol) compared to Çinarcik Basin with 3.11-7.42 μmol/mol (average 4.35 of μmol/mol).

Stable isotopes

Foraminifera used for elemental concentrations were subsequently prepared to determine stable isotope (C and O) compositions. Due to the small quantity of carbonate available, one single bulk measurement was performed per species (GloboBulimina affinis and Bolivina vadescens) for each station (MRS-DV01-PC-04 and MRS-DV05-PC-06), averaging several foraminiferal tests per data point. Quantities of carbonate (foraminiferal test weight available) used for each of these measurements are reported next to stable isotope data in Table 4. At Central High, B. vadescens living in surface sediments (0-0.5 cm) presents a mean δ 13 C value of -2.34‰ and a mean δ 18 O value of + 1.44‰. In comparison, G. affinis, living deeper within the sediment (here sampled from 0.5 to 1 cm), presents a mean δ 13 C value of -1.55‰ and a mean δ 18 O value of + 2.01‰higher values than B. vadescens. Similarly, at Çinarcik Basin, B. vadescens presents a mean δ 13 C value of -2.11‰ and a mean δ 18 O value of + 1.68‰ whilst G. affinis an enriched mean δ 13 C value of -1.64‰ and δ 18 O value of + 1.90‰.

Discussion

Environmental overview of the Central High and the south Çinarcik Basin

Dysoxic ecosystems investigated in this paper were previously documented in other studies related to the MARNAUT oceanographic cruise (e.g., [START_REF] Géli | Gas emissions and active tectonics within the submerged section of the North Anatolian Fault zone in the Sea of Marmara[END_REF][START_REF] Zitter | Cold seeps along the main Marmara fault in the Sea of Marmara (Turkey)[END_REF][START_REF] Ritt | First insights into the structure and environmental setting of cold-seep communities in the Marmara Sea[END_REF][START_REF] Chevalier | Authigenic carbonates at cold seeps in the Marmara Sea (Turkey): a lipid biomarker and stable carbon and oxygen isotope investigation[END_REF][START_REF] Crémière | Methane-derived authigenic carbonates along the North Anatolian fault system in the Sea of Marmara (Turkey)[END_REF]. Our ROV observations during the MARSITE cruise and newly acquired geochemical data confirm that localized cold seepages occur at both the Central High and south Çinarcik Basin (Figs. 3 and5). Sulfate content profiles in long cores MRS-CS-04 (Central High) and MRS-CS-17 (south Çinarcik Basin) notably show a Sulfate-Methane Transition Zone (SMTZ) at depths of 4.4 m and 2.3 m below the seafloor, respectively. There, upward migrating methane is oxidized by a consortium of Archaea and sulfate reducing bacteria which results in hydrogen sulfide and alkalinity production (e.g., [START_REF] Ritt | First insights into the structure and environmental setting of cold-seep communities in the Marmara Sea[END_REF][START_REF] Chevalier | Authigenic carbonates at cold seeps in the Marmara Sea (Turkey): a lipid biomarker and stable carbon and oxygen isotope investigation[END_REF][START_REF] Crémière | Methane-derived authigenic carbonates along the North Anatolian fault system in the Sea of Marmara (Turkey)[END_REF][START_REF] Ruffine | Pore water geochemistry at two seismogenic areas in the sea of Marmara[END_REF] (Fig. 5). This reaction, known as the anaerobic oxidation of methane (AOM), occurs at a shallower depth at the south Çinarcik Basin (MRS-CS-17, 1237 m) than that at Central High (MRS-CS-04, 326 m), indicating a higher upward methane flux (Fig. 5). Higher sedimentation rates and more abundant biodegradable organic matter within the sediments could explain the enhanced diagenetic reactions and methane oxidation in the deeper Çinarcik Basin (Çağatay et al., 2004). That being said, the large filamentous bacterial mat sampled at Central High suggests localized seepage of sulfide-enriched fluid, which may be generated by methane oxidation within subsurface sediments [START_REF] De Prunelé | Etude de la dynamique géochimique de deux zones à hydrates de gaz de la marge africaine[END_REF]. In restricted places where we collected push cores dedicated to foraminiferal study (MRS-DV01-PC-04, MRS-DV05-PC-06), we did not record any gas bubble emission. This rules out that our push cores were affected by free methane gas flowing through the sediment-water interface.

Dissolved manganese profiles in both long cores MRS-CS-17 (south Çinarcik Basin) and MRS-CS-04 (Central High) are totally different from each other. Whereas Mn(II) shows a remarkable subsurface maximum (160 µM) in the core MRS-CS-17, Mn(II) content in core MRS-CS-04 is an order of magnitude lower (16 µM) (Fig. 5). According to [START_REF] Ergin | Possible sources and pmechanisms of manganese enrichment in the deepsea sediments of the Marmara Trough depressions (NE-Mediterranean, Turkey)[END_REF], high concentrations of dissolved manganese in pore water in the Sea of Marmara's deep basins may reflect putative hydrothermal activities. Our pore water geochemical data does not show any hydrothermal seepage at the sampling sites. Alternatively, high content of dissolved Mn could be related to modern external inputs. Mn(IV) oxyhydroxide, which precipitates in oxygenated shelf environments, could be reworked from shallow-water areas and transported to the deep Çinarcik Basin [START_REF] Anschutz | Interactions between metal oxides and species of nitrogen and iodine in bioturbated marine sediments[END_REF][START_REF] Mouret | Benthic geochemistry of managanese in the Bay of Biscay, and sediment mass accumulation rate[END_REF]. Moreover, the Çinarcik Basin, like all deep Marmara sub-basins, are characterized by turbidite-homogenite layers, which may preferentially focus Mn(IV)bearing particles supplied from shallower, oxygenated areas (Mercier- [START_REF] Mercier-De-Lepinay | the MARMACORE team. Interplay between recent sedimentation and active tectonics in Marmara Sea[END_REF][START_REF] Çağatay | Chronostratigraphy and sedimentology of the Marmara Sea over the last 40 ka[END_REF][START_REF] Çağatay | Pore-water and sediment geochemistry in the Marmara Sea (Turkey): early diagenesis and diffusive fluxes[END_REF][START_REF] Beck | Late Qaternary co-seismic sedimentation in the Sea of Marmara's deep basins[END_REF] (Fig. 9). In this case, Mn(IV) oxyhydroxides would be reduced through organic matter mineralization, resulting in extremely high Mn (II) surface sediment content [START_REF] Spencer | Vertical advection diffusion and redox potentials as controls on the distribution of manganese and other trace metals dissolved m waters of the Black Sea[END_REF][START_REF] Çağatay | Pore-water and sediment geochemistry in the Marmara Sea (Turkey): early diagenesis and diffusive fluxes[END_REF].

As previously documented in numerous studies (e.g., [START_REF] Çağatay | Pore-water and sediment geochemistry in the Marmara Sea (Turkey): early diagenesis and diffusive fluxes[END_REF][START_REF] Géli | Gas emissions and active tectonics within the submerged section of the North Anatolian Fault zone in the Sea of Marmara[END_REF][START_REF] Zitter | Cold seeps along the main Marmara fault in the Sea of Marmara (Turkey)[END_REF][START_REF] Ritt | First insights into the structure and environmental setting of cold-seep communities in the Marmara Sea[END_REF][START_REF] Chevalier | Authigenic carbonates at cold seeps in the Marmara Sea (Turkey): a lipid biomarker and stable carbon and oxygen isotope investigation[END_REF][START_REF] Crémière | Methane-derived authigenic carbonates along the North Anatolian fault system in the Sea of Marmara (Turkey)[END_REF] and in combination with our results, both the Central High and the south Çinarcik Basin can be considered oxygen depleted areas characterized by remarkable spatial heterogeneity. This centimetre to kilometre-scale variability is expressed through (1) contrasted geochemical processes below the sedimentwater interface (e.g., enhanced sulfate reduction and dissolved manganese production in the deep basin), (2) various sedimentary facies (e.g., differences in sedimentation rates and gravity-related sedimentation) and (3) an obvious biozonation of benthic life (e.g. microbial mat).

"Survivalist" foraminiferal faunas adapted to extreme ecosystems

In deep-sea ecosystems, both spatial and temporal dynamics of benthic foraminifera are controlled by various physico-chemical parameters (see reviews by [START_REF] Gooday | Benthic Foraminifera (Protista) as tools in deep-water palaeoceanography: environmental influences on faunal characteristics[END_REF][START_REF] Jorissen | Paleoceanographical proxies based on deep-sea benthic foraminiferal assemblage characteristics[END_REF]. The organic-matter flux, related to either exported marine primary production or lateral advection of continental organic compounds, is a major ecological factor that constitutes a fundamental source of energy sustaining foraminiferal metabolic activity, growth, reproduction and biomineralization. However, the acts as a limiting parameter when it provokes either temporary or long-term hypoxia near the sea floor and/or within the sediment (i.e. Oxygen Minimum Zone, OMZ) (e.g., Sen [START_REF] Gupta | Benthic foraminifera in oxygen-poor habitats[END_REF][START_REF] Jannink | Living (Rose Bengal stained) benthic foraminifera from the Pakistan continental margin (northern Arabian Sea)[END_REF][START_REF] Bernhard | Foraminifera of oxygen-depleted environments[END_REF][START_REF] Gooday | Foraminifera in the Arabian Sea oxygen minimum zone and other oxygen-deficient settings: taxonomic composition, diversity, and relation to metazoan faunas[END_REF][START_REF] Kurbjeweit | Distribution biomass and diversity of benthic foraminifera in relation to sediment geochemistry in the Arabian Sea[END_REF][START_REF] Schumacher | Live (Rose Bengal stained) and dead benthic foraminifera from the oxygen minimum zone of the Pakistan continental margin (Arabian Sea)[END_REF][START_REF] Woulds | Oxygen as a control on seafloor biological communities and their roles in sedimentary carbon cycling[END_REF][START_REF] Mallon | The response of benthic foraminifera to lowoxygen conditions of the Peruvian oxygen minimum zone[END_REF][START_REF] Glock | The role of benthic foraminifera in the benthic nitrogen cycle of the Peruvian oxygen minimum zone[END_REF]Fontanier et al., 2014b;[START_REF] Caulle | Live (Rose Bengal stained) foraminiferal faunas from the northern Arabian Sea: faunal succession within and below the OMZ[END_REF]. Consequently, in oxygen-depleted ecosystems, foraminiferal diversity is extremely low in OMZ, and standing stocks generally high (e.g. [START_REF] Jannink | Living (Rose Bengal stained) benthic foraminifera from the Pakistan continental margin (northern Arabian Sea)[END_REF][START_REF] Gooday | Foraminifera in the Arabian Sea oxygen minimum zone and other oxygen-deficient settings: taxonomic composition, diversity, and relation to metazoan faunas[END_REF][START_REF] Schumacher | Live (Rose Bengal stained) and dead benthic foraminifera from the oxygen minimum zone of the Pakistan continental margin (Arabian Sea)[END_REF]Fontanier et al., 2014b;[START_REF] Caulle | Live (Rose Bengal stained) foraminiferal faunas from the northern Arabian Sea: faunal succession within and below the OMZ[END_REF]. In the Sea of Marmara, prevailing oxygen depletion in waters (i.e., below 25 m depth) is related to both water column stratification and organic matter export through the water column. Stratification is clearly illustrated by a strong halocline located at a depth of 25 m, which corresponds perfectly to an abrupt oxycline. Vertical mixing within the water column is inhibited by brackish surface waters originating from the Black Sea. Our sedimentary organic matter data (S1, S2, S3, TOC, HI and OI) reveals relatively higher and more biodegradable organic compounds in the Çinarcik Basin compared to the Central High. This is especially the case for HI and OI values, which are a typical mixture of Type II and Type III kerogen, related to marine phytoplankton and terrestrial higher-plant debris sources respectively [START_REF] Tissot | Petroleum Formation and Occurrence[END_REF][START_REF] Espitalié | La pyrolyse Rock-Eval et ses applications[END_REF][START_REF] Tolun | Organic Geochemistry and origin of late glacial-holocene sapropelic layers and associated sediments in Marmara Sea[END_REF]. Strongly dysoxic conditions enhanced by gravity within the water column may enhance preservation of organic compounds exported to the seafloor (TOC > 2.8% in the 0-1 cm interval).

Prevailing dysoxia at our study sites (< 20 µmol/L) restricts foraminiferal diversity to very low values (S < 9, H' < 0.97). The only stress-tolerant species Bolivina vadescens, predominates living faunas at both Central High and south Çinarcik Basin. This taxon presented remarkably high standing stocks (> 6500 ind./100 cm 2 ) in the microbial mat from Central High, potentially suggesting a symbiotic or trophic relationship with the prokaryote. It is well known that foraminifera, which present alternative metabolic pathways and ecological adaptation (e.g., denitrification ability, P-ER complexes, mutualism with prokaryotes), can thrive under extreme conditions prevailing in oxygendepleted environments (Sen [START_REF] Gupta | Benthic foraminifera in oxygen-poor habitats[END_REF][START_REF] Bernhard | Foraminifera of oxygen-depleted environments[END_REF][START_REF] Bernhard | Benthic Foraminifera of dysoxic sediments: chloroplast sequestration and functional morphology[END_REF][START_REF] Bernhard | Potential symbionts in bathyal foraminifera[END_REF][START_REF] Risgaard-Petersen | Evidence for complete denitrification in a benthic foraminifer[END_REF][START_REF] Bernhard | Peroxisome proliferation in Foraminifera inhabiting the chemocline: an adaptation to reactive oxygen species exposure?[END_REF][START_REF] Høsglund | Denitrification, nitrate turn over, and aerobic respiration by benthic foraminiferans in the oxygen minimum zone off Chile[END_REF][START_REF] Piña-Ochoa | Survival and life strategy of the foraminiferan Globobulimina turgida through nitrate storage and denitrification[END_REF][START_REF] Koho | Vertical migration, nitrate uptake and denitrification: survival mechanisms of foraminifers (Globobulimina turgida) under low oxygen conditions[END_REF]Bernhard et al., 2012a, b). Foraminifera living in methane-and sulfideenriched sediments from cold seep areas exhibit some of these metabolic adaptations (e.g., mutualism with prokaryotes) (e.g., [START_REF] Bernhard | Monterey Bay cold-seep biota: assemblages, abundance, and ultrastructure of living foraminifera[END_REF][START_REF] Mackensen | Low δ 13 C in tests of live epibenthic and endobenthic foraminifera at a site of active methane seepage[END_REF][START_REF] Gupta | Attachment of foraminifera to vestimentiferan tubeworms at cold seeps: refuge from seafloor hypoxia and sulfide toxicity[END_REF][START_REF] Lobegeier | Foraminifera of hydrocarbon seeps: gulf of Mexico[END_REF] but may also rely on bacterial food [START_REF] Panieri | Foraminiferal response to an active methane seep environment: a case study from the Adriatic Sea[END_REF]. At Central High, B. vadescens is an opportunistic taxon which may benefit from lack of competition for food in dysoxic and sulfidic sediments, proliferating in microbial mats by either feeding on bacterial biomass (and break-up products) or thriving in prokaryote symbiosis. Virgulinella fragilis, which is only found in the bacterial mat, was previously documented as a taxon able to retain multiple endosymbiotic bacteria and kleptoplasts in its cell [START_REF] Bernhard | Potential symbionts in bathyal foraminifera[END_REF][START_REF] Tsuchiya | Cytologic and genetic characteristics of endobiotic bacteria and kleptoplasts of Virgulinella fragilis (Foraminifera)[END_REF]. Endosymbionts may be both sulfide oxidisers and sulfate reducers [START_REF] Bernhard | Potential symbionts in bathyal foraminifera[END_REF][START_REF] Tsuchiya | Cytologic and genetic characteristics of endobiotic bacteria and kleptoplasts of Virgulinella fragilis (Foraminifera)[END_REF]. Globobulimina affinis and Chilostomella ovoidea are both large-sized foraminifera (> 125 µm) which occupy subsurface infaunal microhabitats and constitute substantial portions of living faunas. Their vertical distribution pattern has been documented in many OMZ and ventilated organic-matter-enriched ecosystems (e.g., [START_REF] Jannink | Living (Rose Bengal stained) benthic foraminifera from the Pakistan continental margin (northern Arabian Sea)[END_REF][START_REF] Kitazato | Seasonal phytodetritus deposition and responses of bathyal benthic foraminiferal populations in Sagami Bay, Japan: preliminary results from "Project Sagami 1996-1999[END_REF][START_REF] Fontanier | Live benthic foraminiferal faunas from the Bay of Biscay: faunal density, composition, and microhabitats[END_REF][START_REF] Fontanier | Live foraminiferal faunas from a 2800 m deep lower canyon station from the Bay of Biscay: faunal response to focusing of refractory organic matter[END_REF]Fontanier et al., , 2008a[START_REF] Fontanier | Live (stained) benthic foraminifera off Walvis Bay (Namibia): a deep-sea ecosystem under the influence of benthic nepheloid layer[END_REF]Fontanier et al., , 2014aFontanier et al., , 2014b)). Their abundance and microhabitat indicate enhanced bottom-water dysoxia, shallower oxygen penetration into the sediment and the availability of degraded organic matter below the sediment-water interface.

In the Early Holocene during sapropel formation in the Eastern Mediterranean, G. affinis was able to survive low oxygen conditions prevailing throughout the basin [START_REF] Mullineaux | Quaternary stagnations and recirculation of the eastern Mediterranean: changes in the deep water recorded by fossil benthic foraminifera[END_REF]. Accordingly, low-diversity fossil assemblages dominated by G. affinis (and Chilostomella spp.) were described during the S1 sapropelic event in the Aegean Sea, adjacent to the Sea of Marmara (e.g., [START_REF] Geraga | Evaluation of palaeoenvironmental changes during the last 18,000 years in the Myrtoon basin, SW Aegean Sea. Palaeoceanography[END_REF][START_REF] Kuhnt | Deep-Sea ecosystem variability of the Aegean Sea during the past 22 kyr as revealed by Benthic Foraminifera[END_REF][START_REF] Abu-Zied | Benthic foraminiferal response to changes in bottom water oxygenation and organic carbon flux in the eastern Mediterranean during LGM to recent times[END_REF]. To our knowledge, our data constitutes the first living evidence of this taxon dominating a lowdiversity fauna in an oxygen-depleted (and assumedly sapropel-like) environment. Globobulimina spp. possess alternative metabolic pathways (e.g.., nitrate respiration; P-ER complex), enabling them to live in dysoxic to anoxic conditions [START_REF] Risgaard-Petersen | Evidence for complete denitrification in a benthic foraminifer[END_REF][START_REF] Bernhard | Peroxisome proliferation in Foraminifera inhabiting the chemocline: an adaptation to reactive oxygen species exposure?[END_REF][START_REF] Piña-Ochoa | Survival and life strategy of the foraminiferan Globobulimina turgida through nitrate storage and denitrification[END_REF][START_REF] Koho | Vertical migration, nitrate uptake and denitrification: survival mechanisms of foraminifers (Globobulimina turgida) under low oxygen conditions[END_REF].

Foraminiferal standing stocks and diversity recorded in the coarse sediment fraction of the south Çinarcik Basin are much lower than Central High despite sedimentary organic compounds (as a potential food source) being relatively more abundant below the sediment-water interface. A plausible explanation for this faunal depletion could be the absence of the large microbial mat either providing a food source or a filter capable of oxidizing poisonous hydrogen sulfide. Filamentous bacterial mats may provide refuges/oases for "extremophile" foraminifera in both dysoxic/anoxic and sulfidic ecosystems, and during sapropelic periods.

Foraminiferal biogeochemistry

Mg/Ca and Sr/Ca ratios in living Bolivina and Globobulimina affinis are similar at both study sites, which corresponds to the uniform temperature (~14.5 °C) and salinity (38.7 psu) recorded in the deep waters of the Sea of Marmara (Table 1, Fig. 2). Mg/Ca for living and fossil Globobulimina spp. has already been documented in other studies [START_REF] Tachikawa | Mg/Ca and Sr/Ca in living benthic foraminiferal tests from the northeastern Atlantic[END_REF][START_REF] Skinner | Millennial-scale variability of deepwater temperature and δ 18 O dw indicating deep-water source variations in the Northeast Atlantic, 0-34 cal. ka[END_REF][START_REF] Groenveld | Mg/Ca and Mn/Ca ratios in benthic foraminifera: the potential to reconstruct past variations in temperature and hypoxia in shelf regions[END_REF][START_REF] Weldeab | Mg/Ca-ΔCO 2-3 pore watertemperature calibration for Globobulimina spp.: a sensitive paleothermometer for deep-sea temperature reconstruction[END_REF]. The Mg/Ca ratio in living individuals of G. affinis from the Bay of Biscay (NE Atlantic) clearly exhibit correlation with deep-water temperature variation [START_REF] Tachikawa | Mg/Ca and Sr/Ca in living benthic foraminiferal tests from the northeastern Atlantic[END_REF]. However, our Mg/Ca values for G. affinis (14-19 mmol/ mol) deviates from the ratio of ~12 mmol/mol extrapolated with the paleothermometric calibration proposed by [START_REF] Skinner | Rapid fluctuations in the deep North Atlantic heat budget during the last glacial period[END_REF] ). Moreover, our Mg/Ca values are higher than those of commonly used benthic genera like Cibicidoides, Uvigerina, Bulimina [START_REF] Lear | Benthic foraminiferal Mg/Ca-paleothermometry: a revised core-top calibration[END_REF][START_REF] Raitzsch | Benthic foraminifer Mg/Ca anomalies in South Atlantic core top sediments and their implications for paleothermometry[END_REF][START_REF] Huang | Response of eastern tropical Atlantic central waters to Atlantic meridional overturning circulation changes during the Last Glacial Maximum and Heinrich Stadial 1[END_REF], and also B. vadescens (our data).

The minor differences in the stable oxygen and carbon isotope signatures between both study sites are also of note. Following temperature-dependent fractionation and a uniform bottom water δ 18 O (i.e., δ 18 O BW = 1.58‰; Table 1), the foraminiferal δ 18 O shows minor variability within each taxon from both environments (2.01-1.90‰ for G. affinis; 1.44-1.68‰ for B. vadescens) (Table 3). The δ 18 O of G. affinis is relatively close to the equilibrium calcite δ 18 O of the bottom water (δ 18 O e.c. = ~1.90‰), with the Δδ 18 O values (= δ 18 O G.affinis -δ 18 O e.c. ) ranging between + 0.11‰ and + 0.0‰. Our results differ from the Δδ 18 O offset (> + 0.15‰) previously recorded by [START_REF] Mccorkle | The influence of microhabitats on the carbon isotopic composition of deep-sea benthic foraminifera[END_REF] and [START_REF] Fontanier | Stable oxygen and carbon isotopes of live benthic foraminifera from the Bay of Biscay: microhabitats impact and seasonal variability[END_REF]Fontanier et al., ( , 2008b) ) but are consistent with the minor offset (+0.06‰) recorded in the Western Mediterranean Sea by [START_REF] Schmiedl | Environmental and biological effects on the stable isotope composition of Recent deep-sea benthic foraminifera from the Mediterranean Sea[END_REF]. The δ 18 O of B. vadescens is lighter than the δ 18 O e.c of the bottom water, with the Δδ 18 O values ranging from -0.47‰ to -0.31‰. Such an overall depletion (compared to both the δ 18 O e.c , and G. affinis signatures) could be related to a growth-ratedependent fractionation, potentially related to the opportunistic behavior of B. vadescens.

The δ 13 C of G. affinis is lower than the calculated δ 13 C DIC (depletion higher than -1.35‰ at both study sites). Even though G. affinis occupies a subsurface microhabitat, its δ 13 C signature is heavier compared to the shallow infaunal B. vadescens, which ranges between -2.11‰ and -2.34‰. Our observation does not comply with the "microhabitat" effect on carbon isotopes found by others (e.g. [START_REF] Schmiedl | Environmental and biological effects on the stable isotope composition of Recent deep-sea benthic foraminifera from the Mediterranean Sea[END_REF][START_REF] Fontanier | Stable oxygen and carbon isotopes of live benthic foraminifera from the Bay of Biscay: microhabitats impact and seasonal variability[END_REF]Fontanier et al., , 2008b[START_REF] Fontanier | Stable isotopes in deep-sea living (stained) foraminifera from the Mozambique Channel (eastern Africa): multispecies signatures and paleoenvironmental application[END_REF] and again, this enhanced depletion of B. vadescens δ 13 C may result from its growth-rate fractionation. Alternatively, B. vadescens may reproduce and biomineralise its test when ephemeral fluid seeps through the sediment-water interface. In such a setting, this opportunistic taxon would record a depleted δ 13 C compared to Globobulimina spp. which have a lower metabolic rate [START_REF] Nomaki | Deep-sea benthic foraminiferal respiration rates measured under laboratory conditions[END_REF]. However, because intraspecific foraminiferal δ 13 C is relatively uniform between both study areas, it is unlikely that methane-derived carbon is being added to the pore waters in appreciable amounts at sampling. This supports the idea that both push cores dedicated to foraminiferal investigation were obtained either during episodes of reduced gas emission or were located outside the active methane emission zone. The presence of the bacterial mat (and its role either as food source or as hydrogen sulfide oxidizer) has a minor impact on the foraminiferal δ 13 C at Central High. We may have recorded an important depletion in foraminiferal δ 13 C if bacterial biomass constituted an important diet for both investigated species, but this was not the case in this study. An alternative explanation could be that internal controls in foraminiferal cells (e.g., pH-regulation, endosymbiotic activity) may temper the effect of pore water geochemistry and food assimilation on foraminiferal δ 13 C but this is based on only a few measurements and further investigations are necessary.

In recent work regarding modern fjords and OMZ, foraminiferal test Mn/Ca has been proposed as a potentially reliable proxy of bottomwater oxygenation [START_REF] Groenveld | Mg/Ca and Mn/Ca ratios in benthic foraminifera: the potential to reconstruct past variations in temperature and hypoxia in shelf regions[END_REF][START_REF] Koho | Combining benthic foraminiferal ecologyand shell Mn/Ca to deconvolve past bottom water oxygenation and paleoproductivity[END_REF]. In the Sea of Marmara, the Mn/Ca ratio is an order of magnitude higher for both tested living species from the south Çinarcik Basin compared to foraminifera from the bacterial mat at Central High. The foraminiferal test values follow trends recorded in pore water geochemistry. As assumed above, Mn(II) content in the Çinarcik basin may be related to alternate sources and inputs (i.e., Mn(IV)-enriched particles provided from the shelf by riverine inputs and by gravity-induced sedimentation). Therefore, Mn/Ca enrichment for G. affinis and B. vadescens could be the result of physiographically-constrained accumulation/burial of manganese in the fully stratified Çinarcik Basin, where both strongly dysoxic conditions (< 10 µmol/L) and enhanced deposition of organic matter occurs at the seafloor. In the deep Çinarcik Basin, our data shows that Mn(II) does not completely escape the seafloor in heavily reduced sediments and living foraminifera record this geochemical background with higher Mn/Ca ratios. The interpretation of foraminiferal Mn/Ca as a proxy for bottom water oxygenation is not straightforward and depends strongly on regional physiography, sedimentary diagenetic processes and water column structure.

Conclusions

In this preliminary study, we have investigated living foraminifera from the Sea of Marmara. We have focused on faunal composition and geochemical signatures (trace elements, oxygen and carbon stable isotopes) in foraminiferal tests at two sites (Central High and south Çınarcık Basin), located near previously documented cold seeps. Both study areas are characterized by a dysoxic water mass (O 2 < 20 µmol/ L), and present extreme conditions characterized by remarkable spatial heterogeneity. Prevailing dysoxia at both study sites restricts foraminiferal diversity to very low values (S < 9, H' < 0.97). Stress-tolerant species Bolivina vadescens and Globobulimina affinis dominate living faunas in both environments, with higher standing stocks recorded at the shallower Central High site underneath a microbial mat. There is no obvious imprint of methane seepage in the geochemical signatures of benthic foraminifera collected at both sites. Our biogeochemical results suggest that interpreting bottom water oxygenation through foraminiferal Mn/Ca ratios is neither straightforward nor reliable, and depends strongly on regional physiography, water column structure and sedimentary and diagenetic processes close to the seafloor.

MRS-DV01

Fig. 1 .

 1 Fig. 1. Location of push cores (MRS-DV01-PC-02, MRS-DV01-PC-04, MRS-DV05-PC-04 and MRS-DV05-PC-06) and Calypso cores (MRS-CS-04 and MRS-CS-1) retrieved from the Sea of Marmara. Related geographic coordinates, depths and environmental parameters are listed in Tables1 and 2. Black stars correspond to CTD casts (MNT_CTD3 and MNT_CTD10), taken during the MARNAUT cruise (2007) (data available online at http://www.ifremer.fr/sismer/index_FR.htm).

Fig. 2 .

 2 Fig.2. CTD profiles of the water column at Central High and Çinarcik Basin (MARNAUT cruise sites MNT_CTD3 and MNT_CTD10 in Fig.1) including bottom-water temperature, salinity and dissolved oxygen. Sampling depths of push cores indicated by black arrows. Data available online at http://www.ifremer.fr/sismer/index_FR.htm.

Fig. 4 .

 4 Fig. 4. SEM photographs of dominant foraminiferal species documented at Central High and Çinarcik Basin. A-C. Bolivina vadescens (MRS-DV01-PC-04), lateral (A, B) and profile (C) views. D. Chilostomella ovoidea (MRS-DV01-PC-04) lateral view. (E) Globobulimina affinis (MRS-DV01-PC-04) lateral view. (F) Virgulinella fragilis (MRS-DV01-PC-04) profile view. (G, H) Dead G. affinis infilled with pyrite (MRS-DV05-PC-06) with a close-up (H) of octahedral and framboidal pyrite forms.

Fig. 5 .

 5 Fig. 5. Pore water geochemistry from both MRS-CS-04 and MRS-CS-17 Calypso cores collected at Central High and Çinarcik Basin respectively. Measured parameters include dissolved Strontium (Sr(II)), Magnesium (Mg(II)), Barium (Ba(II)), Manganese (Mn(II)), Sulfate (SO 4 -) and Alkalinity.

Fig. 6 .

 6 Fig. 6. Standing stocks, Species richness S, Dominance Index D, Shannon index H', Evenness index E and Berger-Parker index of living (stained) foraminiferal fauna separated by sieve fraction (63 µm and > 125 µm) from push cores MRS-DV01-PC-04 (Central High) and MRS-DV05-PC-06 (south Çinarcik Basin).

Fig. 8 .

 8 Fig.8. Trace elements ratios (Mg/Ca, Sr/Ca, Mn/Ca, Ba/Ca) of living (stained) Bolivina vadescens and Globobulimina affinis from push cores MRS-DV01-PC-04 (Central High) and MRS-DV05-PC-06 (south Çinarcik Basin). "n" indicates number of analyzed individuals (see Methods and Appendix C for further explanation). Error bars illustrate standard deviations.

  ).

	Push-core reference	Interval	S1	S2	Tmax	S3	TOC	HI	OI	MinC	eq CaCO3
		(cm)	(mg/g)	(mg/g)	(°C)	(mg/g)	(%)	(mg HC/g TOC)	mg CO2/g TOC	(%)	(%)
	MRS-DV01-PC-02	0-2	0.04	5.05	424	3.25	2.35	215	138	2.17	18
		1-2	0.04	2.86	421	2.27	1.77	162	128	2.19	18
		2-4	0.08	2.88	417	2.32	1.73	166	134	2.05	17
		4-6	0.05	2.39	416	2.59	1.51	158	172	2.24	19
		6-8	0.08	1.99	411	1.92	1.43	140	135	2.24	19
	MRS-DV05-PC-04	0-1	0.08	6.75	406	5.05	2.86	237	177	1.91	16
		2-4	0.08	5.79	441	3.84	1.92	303	201	6.00	50
		4-6	0.05	3.58	413	3.42	1.87	192	183	3.43	29
		6-8	0.04	2.27	412	2.37	1.26	180	188	4.92

Table 2

 2 Coordinates, sampling depth and core length of Calypso cores studied in this paper.

	Site	Calypso	Latitude (N) Longitude (E) Depth (m) Lenght (cm)
		Core
		reference
	Central High	MRS-CS-	40°51.7'	28°35.0'	326	638
		04
	South Çinarcik	MRS-CS-	40°43.0'	29°06.7'	1237	1060
	Basin	17

Table 3

 3 Foraminiferal density and assemblage diversity indices (S, H', E, D and Berger-Parker) for both Central High and Çinarcik Basin (MRS-DV01-PC-04 and MRS-DV05-PC-06 cores respectively). Standing stocks are normalized for a 100 cm 2 surface area. Two size fractions (63 µm and > 125 µm) were investigated.

		Central High, 329 m depth	South Çinarcik Basin, 1247 m
				depth
		MRS-DV592-01 MRS-DV01-	MRS-DV596-05 MRS-DV05-PC-
		PC-04		06
		63-125 µm	> 125 µm	63-125 µm	> 125 µm
	Species Richness S 8	9	2	3
	Individuals/core	1347	184	46	8
	Standing stocks	5885	804	201	35
	(No/100 cm 2 )
	Dominance	0.89	0.65	0.96	0.41
	Index D
	Shannon Index H'	0.29	0.83	0.10	0.97
	Evenness Index E	0.17	0.26	0.56	0.88
	Berger-Parker	0.94	0.80	0.98	0.50
	Index

  ).

	concentration at 4.7 m.
	Push-core reference	Species	Sediment Interval	Weight (µg)	δ 13 C PDB (‰)	δ 18 O PDB (‰)	δ 13 C DIC PDB (‰)	δ 18 O e.c. PDB (‰)
	MRS-DV01-PC-04	Globobulimina affinis	0.5-1 cm	24	-1.55	2.01	-0.18	1.91
	MRS-DV01-PC-04	Bolivina vadescens	0-0.5 cm	20	-2.34	1.44	-0.18	1.91
	MRS-DV05-PC-06	Globobulimina affinis	0.5-1 cm	28	-1.64	1.90	-0.24	1.89
	MRS-DV05-PC-06	Bolivina vadescens	0-0.5 cm	20	-2.11	1.68	-0.24	1.89

Table 5

 5 Results of Rock-Eval analysis for two push core samples retrieved from Central High and Çinarcik Basin (MRS-DV01-PC-02 and MRS-DV05-PC-04 cores respectively). TOC: Total Organic Carbon, HI: Hydrogen Index, OI: Oxygen Index. Refer to text for detailed descriptions of parameters.

	Push-core reference	Interval	S1	S2	Tmax	S3	TOC	HI	OI	MinC	eq CaCO3
		(cm)	(mg/g)	(mg/g)	(°C)	(mg/g)	(%)	(mg HC/g TOC)	mg CO2/g TOC	(%)	(%)
	MRS-DV01-PC-02	0-2	0.04	5.05	424	3.25	2.35	215	138	2.17	18
		1-2	0.04	2.86	421	2.27	1.77	162	128	2.19	18
		2-4	0.08	2.88	417	2.32	1.73	166	134	2.05	17
		4-6	0.05	2.39	416	2.59	1.51	158	172	2.24	19
		6-8	0.08	1.99	411	1.92	1.43	140	135	2.24	19
	MRS-DV05-PC-04	0-1	0.08	6.75	406	5.05	2.86	237	177	1.91	16
		2-4	0.08	5.79	441	3.84	1.92	303	201	6.00	50
		4-6	0.05	3.58	413	3.42	1.87	192	183	3.43	29
		6-8	0.04	2.27	412	2.37	1.26	180	188	4.92

  -PC-04 63-125 µm Bulimina elegans var. exilis Appendix C. Trace element data from foraminiferal tests. Mg/Ca, Sr/Ca, Mn/Ca, Ba/Ca were measured on the last chamber (F) of size fraction-selected foraminifera from both sites. Due to chamber size limitation, only one measurement was taken per F chamber for Bolivina vadescens but two ablations were performed per Globobulimina affinis. values of these measurements are presented here Push-core referenceSample referenceMg/Ca (mmol/mol) Sr/Ca (mmol/mol) Mn/Ca (μmol/mol) Ba/Ca (μmom/mol) Al/Ca (μmol/mol)

		Bolivina vadescens
	MRS-DV01-	BOLI1203	5.767		1.251		354.168	67.725		1173.454
	PC-04
		BOLI1503	3.408		1.109		87.279	32.874		114.618
		BOLI1602	5.225		1.360		775.245	5.990		280.916
		BOLI1701	6.414		1.433		343.336	19.457		2705.949
		BOLI1801	5.425		1.362		454.687	7.682		351.112
		BOLI1901	3.011		1.318		75.426	6.063		850.414
		BOLI2401	5.765		1.470		326.467	67.229		566.793
		BOLI2501	6.087		1.188		1012.227	33.487		118.423
		BOLI2602	7.120		1.401		710.488	38.222		317.602
		BOLI2801	6.509		1.452		294.754	43.051		559.588
		BOLI2901	7.059		1.054		24.637	60.087		627.612
	MRS-DV05-	BOLI3201	7.610		1.310		730.694	28.847		1458.576
	PC-06
		BOLI3301	5.416		1.387		5177.006	15.044		1512.360
		BOLI3602	4.722		1.312		2770.137	5.990		172.996
		BOLI3702	5.942		1.512		1152.592	15.802		307.011
		BOLI4203	4.718		1.390		2045.297	11.213		1543.228
		BOLI4402	7.493		1.620		2327.851	25.418		620.703
		BOLI4502	6.417		1.181		1322.864	6.019		161.348
		Globobulimina affinis
	MRS-DV01-Bolivina vadescens GLOB3001 PC-04 Bolivina seminuda GLOB3002 Leptohalysis scottii GLOB4002 Nonionella opima MRS-DV05-CFGL1211 Rotaliidae PC-06 Spiroplectammina sp. CFGL1212 Virgulinella fragilis CFGL1311 Total Density CFGL1312 Diversity CFGL1411 CFGL1412 MRS-DV01-PC-04 > 125 µm Bolivina vadescens CFGL16X1 Bulimina elegans var. exilis CFGL16X2	1 8 14.352 303 14.429 4 7 16.428 16.088 1 1 18.510 1 22 14.248 357 17.896 7 16.045 14.668 3 18.053 15.046	5 755 1 13 774 4 1	1.121 1.200 1.252 1.208 1.181 1.206 1.166 1.263 1.263 1.245 1.237	1 116 1 118 3 2	1 59.395 45 48.434 17.230 123.500 134.027 918.985 46 607.735 2 226.320 196.464 344.377 240.483	8.609 1 32 16.809 4.487 4.188 3.108 2.429 33 7.420 2 5.362 4.917 3.225 4.173	18 18 1 1	278.701 1617.943 578.605 572.972 63.379 12.502 66.180 185.631 281.879 51.996 47.508	1 1 1
	Chilostomella ovoidea		2		3	1
	Fursenkoina schreibersiana	1
	Globobulimina affinis	1	3 3		3 1	2 1	2 5	3 1		5
	Gyroidina lamarckiana				1
	Nonionella opima	2
	Rectuvigerina phlegeri	1	2		1
	Virgulinella fragilis	10	3		3
	Total Density		18	41		41	22	25	32		5
	Diversity		6	5		6	2	1	2		1
	MRS-DV05-PC-06 63-125 µm
	Bolivina vadescens	24	18		3
	Nonionella opima	1
	Total Density		25	18		3	0	0	0		0
	Diversity		2	1		1	0	0	0		0
	MRS-DV05-PC-06 > 125 µm
	Bolivina vadescens	3
	Chilostomella ovoidea	1
	GloboBulimina affinis		3		1
	Total Density		4	3		1	0	0	0		0
	Diversity		2	1		1	0	0	0		0

Acknowledgements

We thank the captain and crew of the RV Pourquoi pas? as well as the ROV Victor-6000 team for their technical support and advice. Financial support was provided by the European program "MARsite", under grant ENV.2012.6.4-2 -Long-term monitoring experiment in geologically active regions of Europe prone to natural hazards: The Supersite concept. We thank Pierre Henry (CEREGE), Dominique Birot (Ifremer) and Emeric Gautier (Ifremer) for their kind help concerning CTD measurements (MARNAUT cruise). We thank Florence LeCornec for her help with foraminiferal elemental concentration determination with the LA-ICPMS of the ALYSES Analytical Platform (Centre IRD France Nord). We thank Denis Fiorillo and Marie Balasse of the Museum of Natural History of Paris (MNHN) for allowing access to their machine, as well as their invaluable help while measuring bulk stable isotopes (C and O) of small quantities of benthic foraminifera carbonate. We have special thoughts for Pierre Anschutz (EPOC), who has provided valuable comments concerning Mn cycle. The ALYSES Analytical Platform IRD/ UPMC is supported by grants from Région Ile-de-France. Finally, we want to thank all reviewers (including associate editors) who provided very useful comments on this manuscript.

Depth interval (cm) 0-0.5 0.5-1.0 1.0-1.5 1.5-2.0 2.0-3.0 3.0-4.0 4.0-5.0

Appendix D

Previous paleo-ecological work has identified two different Brizalina species in fossil records from the Sea of Marmara [START_REF] Kaminski | Late Glacial to Holocene benthic foraminifera in the Marmara Sea: implications for Black Sea-Mediterranean Sea connections following the last deglaciation[END_REF]. As pictured and described in the original publications by [START_REF] Seguenza | Prime ricerche intorno ai rizopodi fossili delle argille Pleistoceniche dei dintorni di Catania[END_REF] and [START_REF] Williamson | On the Recent foraminifera of Great Britain[END_REF], Brizalina catanensis (Seguenza) and Brizalina spathulata (Williamson) consist of an oblong-to triangle-shaped test with relatively sharp, smooth margins and an acuminate posterior extremity. In our samples, we did not find these species but rather recorded the dominance of Bolivina vadescens Cushman in living (stained) faunas. As originally described [START_REF] Cushman | Some new Recent foraminifera from the Tropical Pacific[END_REF], it consists of an elongate test with a rounded periphery. Early stage chambers rapidly increase in width after which the sides become nearly parallel (Fig. 4A-C). Sutures are distinct, limbate and particularly sigmoid. Aperture consists of a long, narrow loop-shaped opening.

Appendix E. Supplementary material

Supplementary data associated with this article can be found in the online version at http://dx.doi.org/10.1016/j.dsr2.2017.12.011.