domain: sde sdu

text:
C Fontanier
email: fontanier@foram.eu.com

B Deflandre

S Rigaud

B Mamo

N Dubosq

B Lamarque

D Langlet

S Schmidt

P Lebleu

D Poirier

Fontanier

M.-A Cordier

Live (stained) benthic foraminifera from the West-Gironde Mud Patch (Bay of Biscay, NE Atlantic): Assessing the reliability of bio-indicators in a complex shelf sedimentary unit

Keywords: Benthic foraminifera; West-Gironde Mud Patch, Diversity, Organic matter, Sedimentary environment

    Live (stained) benthic foraminifera from the West-Gironde Mud Patch (Bay of Biscay, NE Atlantic): Assessing the reliability of bio-indicators in a complex shelf sedimentary unit.

Introduction

Continental shelves are areas of high primary production, playing a major role in the sequestration and mineralization of organic carbon [START_REF] Walsh | Biological export of shelf carbon is a sink of the global CO2 cycle[END_REF][START_REF] Hargrave | Particle sedimentation in the ocean[END_REF][START_REF] Smith | The ocean as a net heterotrophic system: implications for the carbon biogeochemical cycle[END_REF][START_REF] Walsh | On the nature of continental shelves[END_REF]Jahnke et al., 1990;[START_REF] Walsh | Importance of continental margins in the marine biogeochemical cycling of carbon and nitrogen[END_REF][START_REF] Wollast | The coastal organic carbon cycle: fluxes, sources and sinks[END_REF][START_REF] Hedges | Sedimentary organic matter preservation: an assessment and speculative synthesis[END_REF][START_REF] Bauer | Ocean margins as a significant source of organic matter to the deep open ocean[END_REF]. Indeed, biogeochemical cycles are exacerbated within the water column and sediments along the continental shelf where rivers deliver large quantities of dissolved nutrients and organic matter into coastal waters [START_REF] Hedges | What happens to terrestrial organic matter in the ocean?[END_REF]. Among these nutrients, nitrate and phosphate stimulate the seasonal or perennial appearance of high primary production plumes along the continental shelf, leading to increased export of phytodetritus to the seafloor [START_REF] Lohrenz | Enhanced primary production at the plume/oceanic interface of the Mississippi River[END_REF][START_REF] Lohrenz | Variations in primary production of northern Gulf of Mexico continental shelf waters linked to nutrient inputs from the Mississippi River[END_REF][START_REF] Dagg | Biological effects of Mississippi River nitrogen on the northern gulf of Mexico--a review and synthesis[END_REF]. Rivers further release large quantities of particulate organic compounds from terrestrial sources and large quantities of freshwater phytoplankton onto continental shelves [START_REF] Mopper | Organic carbon in the ocean: nature and cycling[END_REF][START_REF] Eppley | Relations between primary production and ocean chlorophyll determined by satellite[END_REF][START_REF] Romankevich | Geochemistry of Organic Matter in the Ocean[END_REF]. When not degraded in the water column or exported laterally along continental slopes, this complex particulate organic matter (terrestrial organic matter and exported phytoplankton production) concentrates in muddy environments on continental shelves (e.g., mud belt, mud patch) where it is buried and then variably degraded by diagenetic processes [START_REF] Froelich | Early oxidation of organic matter in pelagic sediments of the eastern equatorial Atlantic: suboxic diagenesis[END_REF][START_REF] Canfield | Pathways of organic carbon oxidation in three continental margin sediments[END_REF]. The efficiency of organic carbon burial and its final sequestration thus depends on (1) the deposition flux of organic matter at the sediment-water interface, [START_REF]3 Q-mode clustering and Indicative Values (IV) Based on faunal content, Q-mode cluster analysis of the seven stations reveals two groups of three stations and one isolated site (Fig. 6). The calculation of Indicative Values (IV) for the 13 major species of our study area shows a marked spatial variability for some taxa as well as species common to certain areas (Table 3). Station 1 (39 m), which is isolated by cluster analysis, is characterized by Q. laevigata (IV = 84%), A. beccarii (IV = 69%), and E. scaber (IV = 42%). Cluster 1 consisting of Stations 2, 7 and 9 (water depth comprised between 47-54 m), is characterized by N. turgidus (IV = 77%), Cancris auriculus (IV = 46%), N. polymorphinoides (IV = 43%). Cluster 2 includes Stations 3, 8 and 4 (all deeper than 56 m) and is characterized by P. neocarinata (IV = 98%), N. faba (IV = 80%), B. marginata (IV = 79%), A. falsobeccarii (IV = 63%)[END_REF] the rate of mineralization in surface sediments, and (3) the hydrosedimentary processes determining benthic biotope architecture [START_REF] Mckee | Transport and transformation of dissolved and particulate materials on continental margins influenced by major rivers: benthic boundary layer and seabed processes[END_REF].

The West-Gironde Mud Patch (WGMP) is a perfect example of a shelf environment where organic compounds from various sources (mainly marine phytodetritus) accumulate within fine sediments [START_REF] Lamarque | proximity, impacted by episodic high-energy hydrodynamics causing low sediment deposition, massive but sporadic sedimentary deposits characterize Station[END_REF]Dubosq et al., in press;Dubosq et al., in prep).

Together with the South-Gironde Mud Patch, the WGMP constitutes a particular set of morpho-sedimentary units that spread between 30-70 m water depth, covering the gravels and sands of the Northern Aquitaine continental shelf (Bay of Biscay, France) [START_REF] Lesueur | Shelf mud fields formation within historical times: examples from offshore the Gironde estuary, France[END_REF]2002;[START_REF] Cirac | Processus de mise en place et d'évolution de la couverture sédimentaire superficielle de la plate-forme nordaquitaine[END_REF]. These muddy patches extend off the two main channels of the Gironde Estuary, the main source of the fine-grained sediments within the WGMP (Fig. 1) [START_REF] Lesueur | Shelf mud fields formation within historical times: examples from offshore the Gironde estuary, France[END_REF]. The WGMP comprises of Gironde River silt deposited during flood events, and a smaller portion of inner continental shelf silts and fine sand deposited during periods of high energy (i.e., storms). Due to the complexity of its spatial structure, temporal dynamics and environmental characteristics, the WGMP has been the subject of intense multidisciplinary investigation for more than ten years (e.g., the BIOMIN project between 2009-2013, the VOG project between 2018[START_REF] Roberts | Labdsv: Ordination and Multivariate Analysis for Ecology[END_REF], the JERICO-NEXT European project with this study). In combination with geochemical, geophysical, sedimentological and biological analyses, these projects have aimed to describe the mineralization processes of organic compounds in the mudflat, taking into account (1) the activity of the benthic organisms thriving there (e. g. bioturbation, aerobic/anaerobic respiration), by [START_REF]3 Q-mode clustering and Indicative Values (IV) Based on faunal content, Q-mode cluster analysis of the seven stations reveals two groups of three stations and one isolated site (Fig. 6). The calculation of Indicative Values (IV) for the 13 major species of our study area shows a marked spatial variability for some taxa as well as species common to certain areas (Table 3). Station 1 (39 m), which is isolated by cluster analysis, is characterized by Q. laevigata (IV = 84%), A. beccarii (IV = 69%), and E. scaber (IV = 42%). Cluster 1 consisting of Stations 2, 7 and 9 (water depth comprised between 47-54 m), is characterized by N. turgidus (IV = 77%), Cancris auriculus (IV = 46%), N. polymorphinoides (IV = 43%). Cluster 2 includes Stations 3, 8 and 4 (all deeper than 56 m) and is characterized by P. neocarinata (IV = 98%), N. faba (IV = 80%), B. marginata (IV = 79%), A. falsobeccarii (IV = 63%)[END_REF] integrating the hydrosedimentary dynamics structuring this morpho-sedimentary unit in space and time, and by (3) trying to define in fine, reliable bio-indicators of the mudflat in all its complexity [START_REF] Lamarque | proximity, impacted by episodic high-energy hydrodynamics causing low sediment deposition, massive but sporadic sedimentary deposits characterize Station[END_REF]Dubosq et al., in press;Dubosq et al., in prep.). Benthic foraminifera constitute relevant proxies for studying present and past marine environments since their faunal communities (diversity, standing stock, microhabitat), their spatial distribution and their temporal dynamics are controlled by numerous physico-chemical parameters including exported organic matter flux, bottom-and pore-water oxygenation and sedimentary substrate (e.g., [START_REF] Gooday | Benthic Foraminifera (Protista) as tools in Deep-water Palaeoceanography: Environmental Influences on Faunal Characteristics[END_REF][START_REF] Murray | Ecology and Applications of Benthic Foraminifera[END_REF][START_REF] Jorissen | Chapter Seven Paleoceanographical Proxies Based on Deep-Sea Benthic Foraminiferal Assemblage Characteristics[END_REF]. The impact of seasonal phytodetritus input and the role of environmental oxygenation on benthic foraminiferal fauna has already been studied in "La Grande Vasière", a mud belt located on the outer continental shelf (between 80-130 m deep) northwest of the WGMP [START_REF] Duchemin | Living benthic foraminifera from "La Grande Vasière", French Atlantic continental shelf: faunal composition and microhabitats[END_REF]2008) (Fig. 1). These works have shown that living benthic communities respond to episodic inputs of organic matter related to phytoplankton blooms from spring to autumn. Certain opportunistic species (i.e. Nonionella iridea, Cassidulina carinata according to the taxonomy of [START_REF] Duchemin | Seasonal variability of living benthic foraminifera from the outer continental shelf of the Bay of Biscay[END_REF] dominate the Grande Vasière mud belt fauna. Foraminiferal diversity, standing stock and vertical distribution within sediments shifts with water depth [START_REF] Duchemin | Living benthic foraminifera from "La Grande Vasière", French Atlantic continental shelf: faunal composition and microhabitats[END_REF]2008).

Following the Grande Vasière studies, the aim of our paper is to assess the relevance of using benthic foraminifera as bio-indicators of the various environmental conditions prevailing along the WGMP. To do so, we can draw on geochemical, geophysical and sedimentological data acquired during the 2017 oceanographic JERICOBENT-2 cruise [START_REF] Deflandre | JERICOBENT-2 cruise, Côtes De La Manche R/V[END_REF]Dubosq et al., in prep; complementary sedimentological analysis presented in this paper). These data are compared to the faunal characteristics (diversity, standing stock, microhabitats) of the foraminiferal communities sampled at the seven stations ranging from 36-69 meters water depth (Fig. 1).

Material and Methods

Water parameters

This investigation is based on data obtained at seven stations sampled during the JERICOBENT-2 cruise in August 2017 (Fig. 1; Table 1) [START_REF] Deflandre | JERICOBENT-2 cruise, Côtes De La Manche R/V[END_REF]. Stations are organized according to a bathymetric gradient from the proximal part of the WGMP (Station 1, 39 m) to the distal (Station 4, 69 m) (Fig. 1; Table 1). Bottom water temperature (CTD measurements) decreases gradually from 14.6°C at station 1 (39 m) to 12.7°C at station 4 (69 m), whereas bottom water salinity (Conductivity-Temperature-Depth measurements) is constant (35.2) (Table 1). Bottom water oxygenation stays relatively high at all sites (between 184-197 µM) (Table 1), oxygen penetration depth (OPD) within the sediments is relatively limited (< 1 cm) indicating a relatively enhanced oxygen demand to degrade organic compounds compared to open-slope environments [START_REF] Fontanier | Live benthic foraminiferal faunas from the Bay of Biscay: faunal density, composition, and microhabitats[END_REF]Dubosq et al., in prep). [START_REF] Gillet | JERICOBENT-5-TH cruise, Thalia R/V[END_REF] Table 1. Location of the seven stations sampled during the JERICOBENT-2 cruise (August 2017) including station coordinates and depth. Physico-chemical parameters including BWT (bottom-water temperature in °C) and BWS (bottom-water salinity in psu) were extrapolated from CTD casts at each site. BWO 2 (bottom-water oxygen in µM) was measured in water overlying the sediment-water interface (SWI) of cores gathered during the JERICOBENT-2 cruise (Dubosq et al., in prep). Oxygen saturation (in %) of bottom water was also calculated (Dubosq et al., in prep). OPD (oxygen penetration depth in cm below the SWI) was determined after N in-situ measurements with a benthic profiler deployed at each station during the JERICOBENT-2 cruise.

Sediment sampling

Sediment samples were collected with a Barnett-type multiple corer equipped with Plexiglas tubes (9.6 mm internal diameter, surface area of 72 cm²) [START_REF] Barnett | A multiple corer for taking virtually undisturbed sample from shelf, bathyal and abyssal sediments[END_REF]. The multicorer allowed for sampling of the uppermost decimeters of the sediment column, the overlying bottom waters, and a comparatively undisturbed sediment-water interface. At each station, the multi-corer was deployed three to five times to get enough material for geochemical, sedimentological and biological investigations. Descriptors of sedimentary organic matter as well as the mineralization processes of organic compounds at and below the sediment-water interface are described in detail by Dubosq et al. (in press; in prep). We refer to a partial synthesis of their results in the discussion with data summarized in Tables 1 and2.

Sedimentological analysis

At each station, one entire core was radiographed with a Scopix system, which consists of an X-Ray imaging system combined with image analysis software (Migeon et al., 1999) (Fig. 2).

The aim of the X-ray radiography is to detect the presence of discrete sedimentary structures (e.g., erosional surfaces, burrows, coarse sedimentary layers). To visually evaluate changes, core photographs were also taken (Fig. 2). Particle grain sizes were measured with a Malvern Laser Diffraction Particle Sizer (type 2600). This technique was applied to sediment samples belonging to the previously radiographed and photographed core and allowed for the calculation of grain size frequency D 50 . To do so, each core was subsampled every 0.5 cm between 0-1 cm depth, every 1 cm between 1-4 cm depth, then every 2 cm between 4-22 cm depth, and with an adaptative resolution deeper downcore.

Table 2. Organic descriptors in the surface sediment (i.e. the 0-0.5 cm interval below the sediment-water interface) at the seven stations sampled during the JERICOBENT-2 cruise (August 2017) (Dubosq et al., in prep): Organic content (OC in % DW), Total nitrogen content (TN in % DW), C/N atomic ratio, Chlorophyllic pigment content (i.e. Chl-a, Chl-b and Phaeo-a) and their freshness index Chl-a/(Chl-a+Phaeo-a).

Foraminiferal faunal analysis

Foraminiferal faunas were studied in a single core per station. Onboard, each core was sliced horizontally every 0.5 cm from the sediment-water interface to a depth of 2 cm, then every centimeter between 2-10 cm depth. Samples (12 slices per core) were transferred into 500 cm 3 bottles, which were filled with 95% ethanol containing 2 g/L Rose Bengal stain, commonly used to identify live foraminifera [START_REF] Walton | Techniques for recognition of living Foraminifera[END_REF][START_REF] Murray | Mortality, protoplasm decay rate, and reliability of staining techniques to recognize 'living' foraminifera: a review[END_REF]. All samples were gently shaken for several minutes to obtain a homogeneous mixture. At the laboratory (one month after the cruise), samples were sieved through 150 µm mesh screens, and sieve residues were stored in 95% ethanol. Stained foraminifera belonging to the >150 µm fraction were sorted in wet samples and stored in Plummer slides. One concern with using Rose Bengal is that it may stain the protoplasm of dead foraminifera that may be relatively well-preserved for long time periods under the generally anoxic conditions prevailing in deep sediments [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]. We therefore applied very strict staining criteria (i.e., all chambers, except the last chamber, stained in bright pink), and compared doubtful individuals to perfectly stained specimens of the same species found in the superficial sediment layers. For miliolids, doubtful specimens were broken to inspect test interior. Most stained foraminifera were identified at species level and checked with the World Foraminifera Database [START_REF] Hayward | World Foraminifera Database[END_REF] for current taxonomic nomenclature (see Appendix A for taxonomical references and Appendix B for census data). Because samples were preserved and sorted in ethanol, many soft-shelled foraminiferal species may have shrunk and become unrecognizable during picking. Thus, our counts probably underestimate the soft-shelled foraminiferal abundance. We obtained digital photographs of major species using a scanning electron microscope at Angers University (Fig. 3). For each core, we calculated different indices to assess diversity. First, we calculated Species Richness (S) and then Shannon index, H' (log base e) as an information-statistic index as described in [START_REF] Murray | Ecology and Applications of Benthic Foraminifera[END_REF]. We determined the Berger-Parker index, which represents the highest relative contribution (in %) calculated for the dominant taxon at each station. A Q-mode cluster analysis based on normalized relative abundances P i values was applied for the seven stations and the 13 major species (≥2.5%), with P i defined as:

) sin( i i p Arc P 
in which "p i " is the relative frequency of the "ith" species, and "P i " is the normalized value of p i (J. Hohenegger, personal communication). We constructed a tree diagram using Ward's method based on Euclidian distance. To do so, we used the PAST Software [START_REF] Hammer | Past: Paleontological Statistics Software Package for Education and Data Analysis[END_REF]. Using Q-mode cluster analysis, we applied the Indicator Value (IV) Method [START_REF] Dufrêne | Species assemblages and indicator species: The need for a flexible asymmetrical approach[END_REF] with the 13 major species in order to determine indicative species in each cluster of stations. For this purpose, we used the following formula:

) ( ) , ( ) , ( ) ( ) , ( ) , ( ) , ( ) , ( ) , ( 100         Nstations Nstations B ls Nindividua ls Nindividua A B A IV i i i i i i i i     
Nindividuals (i,α) is the mean number of individuals belonging to the species i and present in the cluster α. Nindividuals (i) is the sum of the mean numbers of individuals of species i occurring in all clusters. Nstations (i,α) is the number of stations in the cluster α where the species i is present. Nstations (α) is the total number of sites in the cluster α. P values were calculated based on 999 permutations using R package "labdsv" (Roberts 2019; R core team 2020).

Additional details

Our study concerns benthic foraminiferal faunas sampled at a specific time of the year and constitute an ecological snapshot and not a temporal survey. Our investigation into the seasonal dynamics of WGMP benthic fauna remains a work in progress and will be the subject of future publications. Therefore, in this paper, we have focused on benthic foraminiferal communities belonging to the >150-µm-size fraction as bio-indicators of average environmental conditions at each of our seven stations at the end of a sustained period of increased primary productivity. Seasonal monitoring incorporating smaller benthic foraminifera (e.g., belonging to the 63-150 µm-size fraction) will certainly provide valuable additional information on the temporal variability of ecological conditions in this mudflat. But this is not the goal of this study. Furthermore, our study is based on the analysis of a single core per station. Although it is recommended to study several replicates at each site to obtain a more robust, averaged view of foraminiferal faunas [START_REF] Mendes | Distribution of living benthic foraminifera on the northern Gulf of Cadiz continental shelf[END_REF], a lot of studies published for the last decades on the ecology of benthic foraminifera sampled in large study areas integrating various marine ecosystems does not follow this recommendation (e.g., [START_REF] Fontanier | Live benthic foraminiferal faunas from the Bay of Biscay: faunal density, composition, and microhabitats[END_REF][START_REF] Duchemin | Living benthic foraminifera from "La Grande Vasière", French Atlantic continental shelf: faunal composition and microhabitats[END_REF]2008;[START_REF] Goineau | Live (stained) benthic foraminifera from the Rhône prodelta (Gulf of Lion, NW Mediterranean): Environmental controls on a river-dominated shelf[END_REF][START_REF] Dessandier | Lateral and vertical distributions of living benthic foraminifera off the Douro River (western Iberian margin): Impact of the organic matter quality[END_REF][START_REF] Deflandre | JERICOBENT-1 cruise, Côtes De La Manche R/V[END_REF]. Conversely, environmental interpretations of modern foraminiferal faunas are mostly based on a single sample per site. We therefore consider in this study that even if small-scale (metric) spatial variability exists between benthic faunas living at the same station, this variability does not hide the faunal variability existing at the spatial scale of the WGMP,

given that the seven sampled stations are several kilometres apart from each other. Finally, the many recent studies exclusively using >150 µm-sized benthic foraminifera living in the Bay of Biscay (e.g., [START_REF] Fontanier | Live benthic foraminiferal faunas from the Bay of Biscay: faunal density, composition, and microhabitats[END_REF]Ersnt et al., 2005;[START_REF] Langezaal | The influence of seasonal processes on geochemical profiles and foraminiferal assemblages on the outer shelf of the Bay of Biscay[END_REF][START_REF] Duchemin | Living benthic foraminifera from "La Grande Vasière", French Atlantic continental shelf: faunal composition and microhabitats[END_REF]2008) sufficiently provide reliable information concerning what we might expect in terms of foraminiferal diversity, standing stock and distribution on the Aquitaine Shelf. Our study adds new and precious data about benthic environments from a river-dominated inner shelf.

Results

Sedimentary features

Station 1 (depth 39 m) is characterized by a 5 cm-thick surface layer made of very fine sand (D 50 > 75 µm) (Fig. 2). Beneath this layer, dark grey sediments are made of highly compacted

Foraminiferal Composition and Microhabitat

As a general trend, the relative abundance of rotaliid species in the total living fauna increases with water depth, from 25% of the total fauna at Station 1 (39 m) to 64% at Station 8 (60 m).

Conversely, the relative abundance of textulariid taxa is relatively high at Stations 1, 2 and 7 (< 50 m) (% of the total fauna ranging between 60-70%) and reaches lower values at stations 3, 8 and 4 (< 56 m) (% ranging between 35-40%). Miliolids are only abundant at Station 1 (12% of the total fauna). At Station 1 (39 m), Eggerelloides scaber (55% of the total fauna; Fig. 3[1]) is the dominant species (Fig. 5a). It presents an erratic down-core vertical distribution with no preferential microhabitat. Quinqueloculina laevigata (13% of the total fauna; Fig. 3[5]) and Ammonia beccarii (12% of the total fauna; Fig. 3[ [START_REF]3 Q-mode clustering and Indicative Values (IV) Based on faunal content, Q-mode cluster analysis of the seven stations reveals two groups of three stations and one isolated site (Fig. 6). The calculation of Indicative Values (IV) for the 13 major species of our study area shows a marked spatial variability for some taxa as well as species common to certain areas (Table 3). Station 1 (39 m), which is isolated by cluster analysis, is characterized by Q. laevigata (IV = 84%), A. beccarii (IV = 69%), and E. scaber (IV = 42%). Cluster 1 consisting of Stations 2, 7 and 9 (water depth comprised between 47-54 m), is characterized by N. turgidus (IV = 77%), Cancris auriculus (IV = 46%), N. polymorphinoides (IV = 43%). Cluster 2 includes Stations 3, 8 and 4 (all deeper than 56 m) and is characterized by P. neocarinata (IV = 98%), N. faba (IV = 80%), B. marginata (IV = 79%), A. falsobeccarii (IV = 63%)[END_REF][3][4]) are two other major calcareous species. Their abundances are greatest within the uppermost 0.5 cm of the sediment column. Bulimina aculeata (7% of the total fauna; Fig. 3[6]), a calcareous species, presents a plurimodal distribution with a density maximum in the 3-4 cm interval (Fig. 5a).

The agglutinated Nouria polymorphinoides (4% of the total fauna; Fig. 3[7]) preferentially occupies the 0-0.5 cm interval (Fig. 5a). At Station 2 (47 m), E. scaber (50% of the total fauna) has a plurimodal distribution with a density maximum recorded in the 0-0.5 cm interval (Fig. 5b). Bulimina aculeata (15% of the total fauna) shows a bimodal distribution similar to Station 1. Ammonia falsobeccarii (9% of the total fauna) (Fig. 3[8-10]) and A.

beccarii (10% of the total fauna) are secondary species. Nouria polymorphinoides (5% of the total fauna) preferentially occupies the 0-0.5-cm interval. At Station 7 (50 m) E. scaber (52% of the total fauna) shows a peculiar vertical distribution with two maxima recorded in the 0-0.5 cm and 9-10 cm intervals respectively (Fig. 5c). Nouria polymorphinoides (16% of the total fauna) and A. falsobeccarii (8% of the total fauna) show the same microhabitat pattern as E. scaber. Nonionoides turgidus (5% of the total fauna) and B. aculeata (5% of the total fauna) are subsidiary calcareous species. Nonionoides turgidus inhabits the subsurface sediments, 2-3 cm below the sediment-water interface. At Station 9 (54 m), E. scaber (44% of the total fauna) constitutes a bimodal distribution with maxima recorded in the 0-0.5 cm and 6-7 cm intervals (Fig. 5d). The secondary taxon B. aculeata (25% of the total fauna) follows an erratic vertical distribution with two peaks at the 0-0.5 cm and 9-10 cm intervals.

Other major species, A. falsobeccarii (8% of the total fauna) and N. polymorphinoides (8% of the total fauna), are more abundant in the 0-0.5 cm interval. Nonion faba (4% of the total fauna) (Fig. 3[12-13]) presents a density maximum recorded between 1.5-3 cm. Nonionoides turgidus (2.5% of the total fauna) is characterised by a density maximum recorded at the 3-4 cm interval. At Station 3 (56 m), E. scaber (30% of the total fauna) preferentially occupies the uppermost two centimeters of the sediment (Fig. 5e). Bulimina aculeata (23% of the total fauna), A. falsobeccarii (21% of the total fauna) and Bulimina marginata (11% of the total fauna) (Fig. 3[15]) present erratic vertical distributions with density maxima recorded in the 0-0.5-cm interval. Nouria polymorphinoides (7% of the total fauna) preferentially occupies the 0-0.5-cm interval. At Station 8 (61 m), E. scaber (25% of the total fauna) comprises an erratic vertical distribution with a density maximum in the 2-3 cm interval (Fig. 5f). Bulimina aculeata (21% of the total fauna) has a plurimodal distribution with maxima recorded in the 0-0.5 cm, 4-3 cm and 6-7 cm intervals. Ammonia falsobeccarii (20% of the total fauna) has two maxima in the 0-0.5 cm and 1.5-3 cm intervals. Nonion faba (11% of the total fauna) is most abundant between 1-3 cm. Nouria polymorphinoides (7% of the total fauna) and B. marginata (7% of the total fauna) are characterised by density maxima recorded in the uppermost centimeter of sediment. At Station 4 (69 m), E. scaber (25% of the total fauna) is still the dominant taxon presenting a plurimodal vertical distribution (Fig. 5g). Ammonia falsobeccarii (15% of the total fauna) is most abundant in the uppermost centimeter of sediment. Nouria polymorphinoides (13% of the total fauna) occupies the uppermost 2 cm of the sediment. Nonion faba (11% of the total fauna) is most abundant between 2-4 cm. It is worthy to note the occurrence of Rectuvigerina phlegeri (6% of the total fauna) (Fig. 3[11])

and Paracassidulina neocarinata (4%) in the uppermost half centimeter of the sediment.

Discussion

Environmental features of the West-Gironde Mud Patch in August 2017

Sedimentological studies carried out over the last three decades on the WGMP have shown that this seafloor feature is difficult to isolate, define and categorise (e.g., Lesueur et al., 1991;[START_REF] Lesueur | Shelf mud fields formation within historical times: examples from offshore the Gironde estuary, France[END_REF]2002;[START_REF] Cirac | Carte des formations superficielles du plateau aquitain[END_REF] (Fig. 1). The boundaries between the muddy WGMP facies (silt-clay) and the sands of the surrounding Aquitaine Shelf are hard to define as episodic inputs of suspended matter from the Gironde River associated with storm-induced bottom currents cause these facies to migrate several hundred metres from their source [START_REF] Cirac | Processus de mise en place et d'évolution de la couverture sédimentaire superficielle de la plate-forme nordaquitaine[END_REF][START_REF] Lesueur | Origin and morphosedimentary evolution of fine grained modern continental shelf deposits: the Gironde mud fields (Bay of Biscay, France)[END_REF]. Figure 2 shows that Stations 1 and 7, located at the edge of the WGMP (presumably within the zone of shifting boundaries), present complex sedimentary facies where sandy layers are intercalated in finer sediments. Such sedimentary patterns were also documented in core samples collected in Autumn 2016 and in June 2018 during the River estuary. Other studies have also briefly described the seasonal evolution of primary production in the Bay of Biscay using satellite images (SeaWIFS/NASA data) to interpret chlorophyll-a pigment concentration in surface waters [START_REF] Lampert | Spatial variability of phytoplankton composition and biomass on the eastern continental shelf of the Bay of Biscay (north-east Atlantic Ocean). Evidence for a bloom of Emiliania huxleyi (Prymnesiophyceae) in spring 1998[END_REF][START_REF] Fontanier | Seasonal and interannual variability of benthic foraminiferal faunas at 550 m depth in the Bay of Biscay[END_REF][START_REF] Duchemin | Seasonal variability of living benthic foraminifera from the outer continental shelf of the Bay of Biscay[END_REF]. Both offshore and on the shelf, diatoms and coccolithophores bloom during the boreal spring (April-May) [START_REF] Lampert | Dynamique saisonnière et variabilité pigmentaire des populations phytoplanctoniques dans l'atlantique nord (Golfe de Gascogne)[END_REF][START_REF] Fontanier | Seasonal and interannual variability of benthic foraminiferal faunas at 550 m depth in the Bay of Biscay[END_REF][START_REF] Duchemin | Seasonal variability of living benthic foraminifera from the outer continental shelf of the Bay of Biscay[END_REF] (Fig. 8). Thereafter, autotrophic marine dinoflagellates and cyanobacteria form a Deep Chlorophyll Maximum during the summer stratification of surface waters [START_REF] Lampert | Dynamique saisonnière et variabilité pigmentaire des populations phytoplanctoniques dans l'atlantique nord (Golfe de Gascogne)[END_REF]. Phototrophic productivity in the coastal zone close to the Gironde estuary is particularly intense [START_REF] Lampert | Dynamique saisonnière et variabilité pigmentaire des populations phytoplanctoniques dans l'atlantique nord (Golfe de Gascogne)[END_REF]. Therefore, the export of marine phytodetritus between spring and late summer due to the phytoplankton bloom may explain the relatively high content of both degraded and fresh chlorophyll a (i.e., phytodetritus) in the surface sediments of our study area, especially in the central and distal areas of the WGMP (Stations 2, 9, 7, 3, 4 and 8) where hydrodynamic energy remodelling the sea floor is weaker compared to sandy Station 1 (Table 1). The presence of fresh chlorophyll b pigment ([Chl-b] >0.10 µg/g), which originates from land plants, demonstrates that terrestrial organic compounds have recently accumulated in the mud patch. This continental imprint is relatively well marked in the central WGMP (Stations 2, 9 and 7; [Chl-b] >0.10µg/g) (Table 2).

Benthic foraminifera biofacies and environmental implications

By the Q-mode clustering of the seven stations and by the IndVal calculation of our 13 most abundant species, benthic foraminifera living in the West-Gironde Mud Patch can be grouped into three main biofacies (Table 3, Fig. 5a-g). These can be further correlated with a clear bathymetric gradient and gradual changes of sedimentary and geochemical parameters (Fig. 6). The shallowest Station 1 (39 m), characterized by sandy sediments and low organic matter content, is dominated by E. scaber (55%), A. beccarii (12%) and Q. laevigata (13%) (Fig. 5a). At the other six stations characterized by clay-silt facies and variably enriched in organic carbon, foraminiferal diversity (i.e. Shannon index and simple diversity) increases and the cumulative contribution of E. scaber, A. beccarii and Q. laevigata decreases strongly with increasing water depth. Our observations at Station 1 are in agreement with many publications where both E. scaber, A. beccarii and Quinqueloculina spp. are described in inner-shelf, either prodeltaic or estuarine environments, near river mouths (e.g., Barmawidjaja et al., 1992;[START_REF] Debenay | Distribution of the twenty seven dominant species of shelf benthic foraminifers on the continental shelf, north of Dakar (Senegal)[END_REF][START_REF] Diz | Effects of contrasting upwelling-downwelling on benthic foraminiferal distribution in the Ria de Vigo (NW Spain)[END_REF][START_REF] Diz | Distribution of live benthic foraminifera in the Ría de Vigo (NW Spain)[END_REF][START_REF] Goineau | Live (stained) benthic foraminifera from the Rhône prodelta (Gulf of Lion, NW Mediterranean): Environmental controls on a river-dominated shelf[END_REF][START_REF] Mendes | Distribution of living benthic foraminifera on the northern Gulf of Cadiz continental shelf[END_REF][START_REF] Dessandier | Lateral and vertical distributions of living benthic foraminifera off the Douro River (western Iberian margin): Impact of the organic matter quality[END_REF][START_REF] Deflandre | JERICOBENT-1 cruise, Côtes De La Manche R/V[END_REF]. For instance, Dessandier et al.

(2016) documented a strong contribution of both E. scaber and A. beccarii at the shallower sites (< 50 m depth) of a bathymetric transect in front of the Tagus River (Portugal, NE Atlantic). Like Station 1, those inner-shelf environments were characterized by sandy sediments (Q 50 > 100 µm) and very low organic carbon content (< 0.05 % DW). [START_REF] Goineau | Live (stained) benthic foraminifera from the Rhône prodelta (Gulf of Lion, NW Mediterranean): Environmental controls on a river-dominated shelf[END_REF] similarly described a strong contribution of E. scaber (Eggerella scabra in their study), A. beccarii (Ammonia beccarii f. beccarii in their study) and Quinqueloculina spp. at stations sampled in inner-shelf environments from the Gulf of Lions (France, Western Mediterranean Sea). Those stations were located between 15-37 m depth on a relict prodeltaic lobe, adjacent to the Grand Rhône River and were subject to high-energy hydrodynamics.

They were characterized by sandy sediments with low organic matter comprised of continental and degraded compounds (OC content < 1.1 % DW, C:N ratio ranging between 11.5-17.7). It seems that E. scaber, A. beccarii and Q. laevigata thrive preferentially in shallow-water environments where hydro-sedimentary constraints (i.e., sedimentary reworking, winnowing and erosion by strong bottom currents) are enhanced. It is noteworthy that the erratic vertical distribution of E. scaber within anoxic sediments of all our stations underline its capacity to thrive under low oxygenation without any preference for fresh food [START_REF] Diz | Effects of contrasting upwelling-downwelling on benthic foraminiferal distribution in the Ria de Vigo (NW Spain)[END_REF][START_REF] Langlet | Foraminiferal species responses to in situ, experimentally induced anoxia in the Adriatic Sea[END_REF]. Such patterns have also been documented in laboratory experiments simulating hypoxia and/or organic supply with sediment material sampled in the Bay of Biscay [START_REF] Ernst | A comparison of foraminiferal infaunal distributions in field and experimental samples from 550-m depth in the Bay of Biscay[END_REF].

Q-mode analysis Cluster 1 groups stations located in the central part of the WGMP (between 47-54 m water depth). There, organic compounds (OC content between 0.9-1.8 % DW) with fresh and degraded marine phytodetritus ([Chl-a] >1.15 µg/g; [Phaeo-a] > 6.65 µg/g)) and terrestrial organic matter ([Chl-b] > 0.10 µg/g) focus in muddy sediments (Table 2; species (Table 3). Eggerelloides scaber is still the dominant species of all stations grouped in this cluster. Bulimina aculeata was described in the Gulf of Cadiz (SW Iberian Peninsula)

between water depths of 30-100 m by [START_REF] Mendes | Distribution of living benthic foraminifera on the northern Gulf of Cadiz continental shelf[END_REF]. This species occurs in muds associated with weak hydrodynamics, in-sediment enhanced hypoxia and high organic matter content. Nouria polymorphinoides with C. auriculus and A. pseudospiralis were documented in shelf environments between depths of 27-75 m in the Gulf of Guinea due to the high primary productivity and fresh organic matter found in the sediments along the Ivory Coast and near the Volta Delta (Altenbach et al., 2003). [START_REF] Debenay | Distribution of the twenty seven dominant species of shelf benthic foraminifers on the continental shelf, north of Dakar (Senegal)[END_REF] pseudospiralis (Ammobacculites pseudospirale in their study) on the shelf off Senegal (NW Africa), at the mouth of the Senegal River. [START_REF] Goineau | Live (stained) benthic foraminifera from the Rhône prodelta (Gulf of Lion, NW Mediterranean): Environmental controls on a river-dominated shelf[END_REF] have also documented the dominance of both living E. scaber (Eggerella scabra in their study) and N. turgidus (Nonionella turgida in their study) at depths ranging between 47-62 m close to the Rhône River mouth. There, both species take advantage of terrestrial and marine organic compounds buried within the sediments [START_REF] Goineau | Live (stained) benthic foraminifera from the Rhône prodelta (Gulf of Lion, NW Mediterranean): Environmental controls on a river-dominated shelf[END_REF]. Nonionoides turgidus is often considered an opportunistic and stress-tolerant taxon thriving in hypoxic and eutrophic conditions [START_REF] Duchemin | Seasonal variability of living benthic foraminifera from the outer continental shelf of the Bay of Biscay[END_REF][START_REF] Goineau | Live (stained) benthic foraminifera from the Rhône prodelta (Gulf of Lion, NW Mediterranean): Environmental controls on a river-dominated shelf[END_REF]. Its relatively deep infaunal microhabitat (> 2 cm depth) in our study area confirms both trophic and metabolic strategies.

Cluster 2 groups stations with silt-clay facies located between 56-60 m depth in the distal section of the WGMP. There, sedimentary organic carbon content is moderate with values ranging between 1.2-1.4% DW (Table 2). Fresh and degraded phytodetritus are available in a lesser quantity compared to the central area of the WGMP (Fig. 5e-g). Paracassidulina neocarinata, N. faba, B. marginata, A. falsobeccarrii, B. aculeata and R. phlegeri are the most indicative species of this 'outer-WGMP' cluster (Table 3). Those taxa are all commonly recorded in mid-to outer-shelf environments (e.g., [START_REF] Debenay | Distribution of the twenty seven dominant species of shelf benthic foraminifers on the continental shelf, north of Dakar (Senegal)[END_REF][START_REF] Fontanier | Live benthic foraminiferal faunas from the Bay of Biscay: faunal density, composition, and microhabitats[END_REF][START_REF] Langezaal | The influence of seasonal processes on geochemical profiles and foraminiferal assemblages on the outer shelf of the Bay of Biscay[END_REF]Duchemin.et al., 2005;2008;[START_REF] Goineau | Live (stained) benthic foraminifera from the Rhône prodelta (Gulf of Lion, NW Mediterranean): Environmental controls on a river-dominated shelf[END_REF][START_REF] Dessandier | Lateral and vertical distributions of living benthic foraminifera off the Douro River (western Iberian margin): Impact of the organic matter quality[END_REF][START_REF] Deflandre | JERICOBENT-1 cruise, Côtes De La Manche R/V[END_REF]. For example, N. faba, B. marginata and P. neocarinata dominate the >150 µm-sized faunas sampled between 80-140 m depth in La Grande Vasière mud belt in the Bay of Biscay (NE Atlantic) [START_REF] Duchemin | Living benthic foraminifera from "La Grande Vasière", French Atlantic continental shelf: faunal composition and microhabitats[END_REF]2008). In Goineau et al. comparable to our study area, P. neocarinata and R. phlegeri, present a shallow infaunal microhabitat typical of species feeding preferentially on labile organic compounds available in the most oxygenated sediments. Paracassidulina neocarinata behave as an opportunistic species relying on freshly deposited phytodetritus produced during spring to early summer blooms [START_REF] Fontanier | Seasonal and interannual variability of benthic foraminiferal faunas at 550 m depth in the Bay of Biscay[END_REF][START_REF] Duchemin | Seasonal variability of living benthic foraminifera from the outer continental shelf of the Bay of Biscay[END_REF]. In our study area, N. faba inhabits an intermediate infaunal distribution traversing the dysoxic and the anoxic sediments (Fig. 5f-g).

This pattern agrees with all other publications where this outer-shelf species is documented (e.g., [START_REF] Fontanier | Live benthic foraminiferal faunas from the Bay of Biscay: faunal density, composition, and microhabitats[END_REF][START_REF] Langezaal | The influence of seasonal processes on geochemical profiles and foraminiferal assemblages on the outer shelf of the Bay of Biscay[END_REF][START_REF] Goineau | Live (stained) benthic foraminifera from the Rhône prodelta (Gulf of Lion, NW Mediterranean): Environmental controls on a river-dominated shelf[END_REF][START_REF] Dessandier | Impact of organic matter source and quality on living benthic foraminiferal distribution on a river-dominated continental margin: A study of the Portuguese margin[END_REF]. Though N. faba's putative abilities such as denitrifying metabolism or endosymbiosis with procaryotes are still debated. In subsurface sediment layers, N. faba can rely on fresh or degraded organic compounds actively buried in deeper sediments [START_REF] Fontanier | Live benthic foraminiferal faunas from the Bay of Biscay: faunal density, composition, and microhabitats[END_REF][START_REF] Duchemin | Seasonal variability of living benthic foraminifera from the outer continental shelf of the Bay of Biscay[END_REF]. Alternatively, this species may migrate toward the sediment surface to gather fresher phytodetritus [START_REF] Langezaal | The influence of seasonal processes on geochemical profiles and foraminiferal assemblages on the outer shelf of the Bay of Biscay[END_REF].

An ecological continuum through the muddy environments of the Bay of Biscay

Our investigation allows us to appreciate the faunal continuum existing in the Bay of Biscay from the WGMP (40-70 m) (our study area) to the Grande Vasière located between 80-130 m depth on the outer continental shelf [START_REF] Duchemin | Living benthic foraminifera from "La Grande Vasière", French Atlantic continental shelf: faunal composition and microhabitats[END_REF]2008). Although geographically disconnected (Fig. 1), these two muddy environments have dominant foraminiferal species that appear clearly organized along a range of correlated environmental gradients. Nonion faba, B. marginata and P. neocarinata, typical of the deepest part of the WGMP, are all dominant in the Grande Vasière [START_REF] Duchemin | Seasonal variability of living benthic foraminifera from the outer continental shelf of the Bay of Biscay[END_REF]. These species can be considered specialists preferentially living in fine sediments from open-ocean environments and relying on marine phytodetritus derived from median and outer shelf primary production (i.e., diatoms and coccolithophore blooms in spring). In contrast, other species, although dominant in the distal WGMP, are absent from the outer continental shelf. This is notable in regard to A. falsobeccarrii, B. aculeata and R. phlegeri which seem restricted to the WGMP potentially due to trophic preferences (i.e., phytodetritus associated with coastal primary production, terrestrial organic compounds) or a higher competitive ability compared to taxa living in deeper ecosystems. Other species which are clearly dominant in the proximal part of the WGMP (E. scaber, Q. laevigata, A. beccarii) are extremely rare or even absent in the Grande Vasière [START_REF] Duchemin | Seasonal variability of living benthic foraminifera from the outer continental shelf of the Bay of Biscay[END_REF]. As explained previously, these species are considered to be generalists with the ability to proliferate in hydrodynamically-impacted costal ecosystems where hydro-sedimentary pressure and food availability represent major ecological constraints. To summarize, our Bay of Biscay study illustrates the utility of using foraminiferal faunas with muddy environmental preferences to discriminate well-oxygenated biotopes and how they are variably impacted by spatially disparate hydrodynamics and their correlated deposition of organic compounds. Due to their propensity to be readily preserved in the fossil record, the calcareous benthic foraminifera of the WGMP and Grand Vasière could be successfully used in sedimentary records to rebuild precisely how muddy sedimentary units developed in the Bay of Biscay during the Late Holocene.

Conclusions

Live (Rose-Bengal stained) shelf foraminiferal faunas have been studied at seven stations between 39-69-m depth in the West-Gironde Mud Patch (WGMP) (Bay of Biscay, NE Atlantic) to understand how complex environmental conditions (e.g., organic matter, oxygenation, sedimentary facies) control foraminiferal ecological patterns (i.e., diversity, faunal composition, standing stock, and microhabitats). The main conclusions of this work are:

(1) In the WGMP, foraminiferal simple diversity (S) presents relatively moderate values ranging between 15-35 taxa. According to Shannon Index H', foraminiferal diversity tends to increase with water depth. The relative contribution of Eggerelloides scaber, the dominant foraminiferal species at all stations, decreases with decreased proximity to the coast and increased depth in the WGMP.

(2) The shallowest station (Station 1, 39 m) proximal to the WGMP is characterized by the relatively important contribution of Eggerelloides scaber, Quinqueloculina laevigata and Ammonia beccarii, which are all typical of inner-shelf environments constrained by high-energy hydrodynamics and river discharge. There, surface sediments are comprised of winnowed sand strongly depleted in organic matter.

( Finally, our unique study underlines the foraminiferal continuum existing through the muddy environments of the Bay of Biscay, between the WGMP and the Grande Vasière.

MAGMA project (COTE cluster of Excellence ANR-10-LABX-45). NASA is acknowledged as a source of MODIS Satellite images (https://modis.gsfc.nasa.gov/). Finally, we thank both reviewers who have provided very useful comments to improve the overall quality of this paper.

Figure 1 .

 1 Figure 1. (a) Map of the Bay of Biscay continental shelf with the locations of mud belts and

Figure 2 .

 2 Figure 2. Photograph and X-Ray radiograph (Scopix) of split cores collected at the seven

Figure 3 .

 3 Figure 3. SEM photographs of some major foraminiferal taxa observed in our study area. 1

  and sticky mud (D 50 ~ 10 µm) within which some dense-material laminae are visible. Station 2 (depth 47 m) is characterized by a clay-silt facies (D 50 ranging between 15-25 µm) throughout the sampled section. Horizontal, vertical and oblique biological structures (i.e. burrows) are abundant all along the core (Fig.2). Station 7 (depth 50 m) constitutes a 4 cmthick subsurface layer made of sandy silt (D 50 reaching 50 µm) between 7-11 cm depth.Above and below this layer are sediments composed of fine particles (D 50 < 27 µm).Millimetric laminae are visible between 20 and 30 cm depth (Fig.2). Station 9 (54 m) is characterized by a silty layer (D 50 ~20 µm) 7 cm thick overlying very fine sediments (D 50 ~ 10 µm). Two gastropod shells of Turritella communis were found in the 10 first cm. Stations 3, 8 and 4 (between 56-69 m deep) present homogeneous facies made of clayey silt (D 50 ranging between 15-25 µm). Biological structures (i.e., burrows) are abundant all along these three cores (Fig.2).3.2. Foraminiferal faunas (>150 µm)3.2.1 Diversity IndicesTotal foraminiferal standing stocks vary between 1,299 individuals/core at Station 7 (50 m) and 3,737 individuals/core at Station 9 (54 m) (Fig.4a; Appendix B). There is no trend following water depth. Species richness S (/core) ranges between 18 at Station 7 and 31 taxa at the deepest Station 4 (69 m depth) (Fig.4a; Appendix B). Excluding Station 1 (39 m), species richness S increases gradually with water depth along the WGMP. The H' (/core) is low (1.6) at Station 1 and increases with water depth to 2.4 at Station 4 (Fig.4b). Berger-Parker index (/core) decreases with water depth between 0.24-0.55.

Figure 4 .

 4 Figure 4. (a-b) Ecological indices describing foraminiferal faunas at the seven stations from

Figure 5 .

 5 Figure 5. (a-g) Foraminiferal composition and down-core distribution of live benthic

Figure 5 .

 5 Figure 5. (a-g) Foraminiferal composition and down-core distribution of live benthic

Figure 6 .

 6 Figure 6. Q-mode cluster analysis of the seven stations following the Ward's method based on

Figure 7 .

 7 Figure 7. Synthetic seasonal maps of Chlorophyll a concentration in surface waters of the Bay

Fig. 6 )

 6 Fig.6). Foraminiferal faunas are characterized by a relatively high contribution of B.

  described live and dead A. falsobeccarii (Eponides falsobeccarii in their study), C. auriculus and A.

(

  2011), P. neocarinata (Cassidulina carinata in their study), N. faba (Nonion fabum in their study), and R. phlegeri statistically clustered together and were indicative of benthic ecosystems located between 44-86 m depth under the influence of the Rhône River plume. These species thrived in very fine sediments (D 50 ~10 µm) with moderate organic carbon content (OC between ~1.1-1.3% DW). These environmental conditions are close to those found at the distal end of the WGMP. In Dessandier et al. (2016), P. neocarinata (Cassidulina carinata in their study), R. phlegeri and N. faba (Nonion scaphum in their study) were documented between 50-100 m depth in mid-and outer-shelf environments characterized by silt to fine-sand facies supporting moderate quantities of organic compounds. In all studies

  ) In the central part of the WGMP where variably degraded marine phytodetritus and terrestrial organic compounds are concentrated within clay-silt facies, foraminiferal faunas are characterized by a relatively high contribution of Bulimina aculeata, Ammonia falsobeccarrii, Nouria polymorphinoides and Nonionoides turgidus. The agglutinated Eggerelloides scaber is still the most important taxon. (4) The deeper stations (>55 m depth) located distally within the mud patch are characterised by the high contribution of B. aculeata, A. falsobeccarrii and N. polymorphinoides. But they are accompanied by Bulimina marginata, Rectuvigerina phlegeri, Nonion faba and Paracassidulina neocarinata, typical of mid-and outershelf ecosystems where fine sediments and organic compounds accumulate.

Acknowledgement

We would like to thank the crews and the captain of the Côte de la Manche (CNRS-INSU) during the JERICOBENT-2 cruise. We have special thoughts for all scientific members who participated to this scientific mission. This work was supported by: (1) the JERICO-NEXT project (European Union's Horizon 2020 Research and Innovation program under grant agreement no. 654410), ( 2) the VOG project (LEFE-CYBER and EC2CO-PNEC), and (3) the

Appendix captions

Appendix A

Major foraminiferal species (≥ 5%) identified in the West-Gironde Mud Patch, with reference to plates and figures in the literature. Supplementary data associated with this article can be consulted in the online version at xxxx.

Appendix B

Census data for live (stained) benthic foraminifera in the >150 µm fraction for the seven stations sampled in the West-Gironde Mud Patch. N.B. Numbers are not standardized for sediment volume. Supplementary data associated with this article can be consulted in the online version at xxxx.