Capbreton Canyon Research Articles

Effect of circulation at early life stages of European anchovy in the Bay of Biscay from observational data and a Lagrangian approach

Coastal circulation influences the distribution of European anchovy (Engraulis encrasicolus) at early life stages (ELS) in the Bay of Biscay (BoB). However, how this happens is not yet fully understood. In this work, further insight is provided by performing Lagrangian diagnostics based on observations of ELS anchovies' initial distributions and currents. Surface diagnostics were obtained by using high-frequency radar (HFR) currents and were applied to analyse multiyear variability and detect the coastal processes that affect the distribution. Since ELS anchovies are also located at subsurface levels, subsurface diagnostics were obtained by using currents reconstructed from HFR and ADCP observations with a reduced order optimal interpolation (ROOI) method. The analyses included transport computations as well as the analysis of flow properties by Lagrangian Coherent Structures and chlorophyll-a satellite images.Results suggest that ELS anchovies are mostly retained over the shelf and slope, and that transport patterns highly vary across different periods. Mesoscale structures such as eddies, fronts and along-slope currents within the slope and the Capbreton canyon area, as well as strong and persistent winds, could significantly impact the distribution of ELS anchovies. In some periods, the resulting distribution might be due to a combination of these processes. Circulation can also play a key role in ELS anchovy aggregation within short time scales (20 days). This work showcases the potential of observation-based approaches and emphasizes the relevance of coastal observatories for integrated studies.

Deep learning-assisted high resolution mapping of vulnerable habitats within the Capbreton Canyon System, Bay of Biscay

The Capbreton Canyon System is an area currently under study for its proposal as a Site of Community Importance under the EU Habitats Directive in the context of the LIFE IP INTEMARES project. Identifying and mapping benthic Vulnerable Marine Ecosystems (VMEs) plays a key role in this process. Although obtaining information on species distribution in deep sea rocky habitats has traditionally been a complicated task, the development of underwater remote sensing techniques resulted in a massive increase in the collection of digital imagery; however, processing all this information has led to another bottleneck due to the time-consuming nature of biota manual annotation. At this point, the use of computer vision and deep learning to automate image processing has substantial benefits but has rarely been adopted within the field of marine ecology. This study presents the integration of deep learning techniques for benthic fauna identification, high resolution multibeam echosounder (MBES) data and Species Distribution Models (SDMs), to map the potential habitat of the yellow coral Dendrophyllia cornigera, a representative species of the VME 1170 Reef habitat, on the circalitoral area of the Capbreton Canyon System. The localization and identification of the coral colonies was based on more than 7500 photographs taken during the INTEMARES-CapBreton 0619 and 0620 surveys using the photogrammetric ROTV Politolana. For the automatic annotation of the image set a deep learning based framework was developed by testing two different deep neural networks architectures; a FasterRCNN+Resnet101 model, accomplishing a precision of 100% over human expert annotation for presence/absence discrimination, was selected. Environmental data included different quantitative terrain attributes derived from high resolution MBES bathymetry data. A presence-only species distribution model, Maximum Entropy (MaxEnt), was used to infer the spatial distribution of D. cornigera over the study area. Predicted occurrences corresponded mainly to relevant topographic structures with significant slope, mainly associated to the edge of the continental shelf. These results are consistent with the ecological knowledge on the species and validate the use of deep learning tools to assist in the identification and mapping of VME for management and conservation purposes. This study provides a baseline for the protection of vulnerable habitats of the Capbreton Canyon System in the context of the Natura 2000 Network.

Macrofaunal variability in the continental shelf and canyons in the southeastern Bay of Biscay

Located in the southeastern Bay of Biscay, the eastern Cantabrian Sea is characterized by the presence of the Capbreton Canyon and a highly diverse and complex geomorphology. The sedimentary seafloor is dominant and biota inhabiting it has been widely studied. The objective of the present research is to contribute to the knowledge of the spatial variability in the composition of the soft-bottom macrofaunal communities in a transitional zone from the continental shelf to the tributary valleys of the Capbreton Canyon. A total of 72 grab samples was studied in the southeastern Cantabrian Sea covering a range of depths of 97–1476 m. A decrease of density and species, and an increase of ‘phylogenetic’ diversity within depth were observed. In the continental shelf greater variability in species assemblages was noticed, according to greater variability in sedimentary characteristics. However, no clear relationship was found between the sedimentary characteristics and the macrofaunal structural indexes (species, Shannon (H’), ‘phylogenetic’ diversity). The most remarkable depth-related change in macrofauna happened at the depth of ca. 200–400 m, coinciding with a change in sediment characteristics, mainly organic matter content and mean grain size. Because the percentage of unidentified taxa at species level increased with depth, patterns in relation to depth should be considered with caution. The present research provides valuable information to gain knowledge in the communities living in the area for conservation and management purposes.

Coastal submesoscale processes and their effect on phytoplankton distribution in the southeastern Bay of Biscay

Abstract. Submesoscale processes have a determinant role in the dynamics of oceans by transporting momentum, heat, mass, and particles. Furthermore, they can define niches where different phytoplankton species flourish and accumulate not only by nutrient provisioning but also by modifying the water column structure or active gathering through advection. In coastal areas, however, submesoscale oceanic processes act together with coastal ones, and their effect on phytoplankton distribution is not straightforward. The present study brings the relevance of hydrodynamic variables, such as vorticity, into consideration in the study of phytoplankton distribution, via the analysis of in situ and remote multidisciplinary data. In situ data were obtained during the ETOILE oceanographic cruise, which surveyed the Capbreton Canyon area in the southeastern part of the Bay of Biscay in early August 2017. The main objective of this cruise was to describe the link between the occurrence and distribution of phytoplankton spectral groups and mesoscale to submesoscale ocean processes. In situ discrete hydrographic measurements and multi-spectral chlorophyll a (chl a) fluorescence profiles were obtained in selected stations, while temperature, conductivity, and in vivo chl a fluorescence were also continuously recorded at the surface. On top of these data, remote sensing data available for this area, such as high-frequency radar and satellite data, were also processed and analysed. From the joint analysis of these observations, we discuss the relative importance and effects of several environmental factors on phytoplankton spectral group distribution above and below the pycnocline and at the deep chlorophyll maximum (DCM) by performing a set of generalized additive models (GAMs). Overall, salinity is the most important parameter modulating not only total chl a but also the contribution of the two dominant spectral groups of phytoplankton, brown and green algae groups. However, at the DCM, among the measured variables, vorticity is the main modulating environmental factor for phytoplankton distribution and explains 19.30 % of the variance. Since the observed distribution of chl a within the DCM cannot be statistically explained without the vorticity, this research sheds light on the impact of the dynamic variables in the distribution of spectral groups at high spatial resolution.

Microbial degradation of hydrophobic emerging contaminants from marine sediment slurries (Capbreton Canyon) to pure bacterial strain

Despite emerging contaminants (ECs) are more and more monitored in environmental matrices, there is still a lack of data in marine ecosystems, especially on their fate and degradation potentials. In this work, for the first time, the degradation potential of synthetic musks (galaxolide and tonalide), UV filters (padimate O and octocrylene) and a pharmaceutical compound (carbamazepine) was studied in marine sediment samples, under laboratory conditions using sediment slurry incubations under biotic and abiotic conditions. Minimum half life times under biotic conditions were found at 21 days, 129 days and 199 days for padimate O, galaxolide and carbamazepine, respectively. Enrichments conducted under anoxic and oxic conditions demonstrated that degradations after one month of incubation either under both biotic and abiotic conditions were limited under anoxic conditions compared to oxic conditions for all the contaminants. Novel aerobic bacteria, able to degrade synthetic musks and UV filters have been isolated. These novel strains were mainly related to the Genus Bacillus. Based on these results, the isolated strains able to degrade such ECs, can have a strong implication in the natural resilience in marine environment, and could be used in remediation processes.

Eusirus bonnieri sp. nov. (Crustacea: Amphipoda: Eusiridae), a new deep speciesfrom the southeastern Bay of Biscay (NE Atlantic Ocean).

A new bathyal eusirid, Eusirus bonnieri sp. nov., is described from the SE Bay of Biscay, mainly characterized by its strongly deflexed rostrum (not mentioned for any other known Eusirus species) and by a long spiniform process at the posterodistal corner of pereopods 5-7 merus. It was sampled with a suprabenthic sledge between 370 and 1099 m on southern margin of the Cap Ferret Canyon and within the Capbreton Canyon. It was relatively scarce on the open slope and its maximum abundance was registered within the upper part of the Capbreton canyon. Beside some ecological/biological data, an identification key is provided for all known species in this genus.

Marine mercury-methylating microbial communities from coastal to Capbreton Canyon sediments (North Atlantic Ocean)

Microbial mercury (Hg) methylation transforms inorganic mercury to neurotoxic methylmercury (MeHg) mainly in aquatic anoxic environments. Sampling challenges in marine ecosystems, particularly in submarine canyons, leads to a lack of knowledge about the Hg methylating microbia in marine sediments. A previous study showed an enrichment of mercury species in sediments from the Capbreton Canyon where both geochemical parameters and microbial activities constrained the net MeHg production. In order to characterize Hg-methylating microbial communities from coastal to deeper sediments, we analysed the diversity of microorganisms’ (16S rDNA-based sequencing) and Hg methylators (hgcA based cloning and sequencing). Both, 16S rDNA and hgcA gene analysis demonstrated that the putative Hg-methylating prokaryotes were likely within the Deltaproteobacteria, dominated by sulfur-compounds based reducing bacteria (mainly sulfate reducers). Additionally, others clades were also identified as carrying HgcA gene, such as, Chloroflexi, Spirochaetes, Elusimicrobia, PVC superphylum (Plantomycetes, Verrucomicrobia and Chlamydiae) and Euryarchaea. Nevertheless, 61% of the hgcA sequences were not assigned to specific clade, indicating that further studies are needed to understand the implication of new microorganisms carrying hgcA in the Hg methylation in marine environments. These first results suggest that sulfur cycle drives the Hg-methylation in marine ecosystem.

Upstream migrating knickpoints and related sedimentary processes in a submarine canyon from a rare 20-year morphobathymetric time-lapse (Capbreton submarine canyon, Bay of Biscay, France)

The Capbreton submarine canyon is a striking feature of the south-east of the Bay of Biscay. This canyon forms a deep incision through the continental shelf and slope, and displays remarkable structures linked to its present-day hydrosedimentary activity. Its head has been disconnected from the Adour River since 1310 CE, but remains close enough to the coast to be supplied with sediment by longshore drift. Gravity processes in the canyon body are abundantly described and documented, but activity in the head and the fan of the canyon is poorly constrained. Furthermore, many questions remain regarding the details of processes affecting the head, the body and the fan of the Capbreton canyon. In this work, we address the paucity of documentation concerning (1) the temporal evolution of sediment transfer between the head and the deep reaches of the canyon, and (2) the interaction between gravity processes and the morphology of the canyon floor, including both shaping and feedback mechanisms.This study is based on the analysis and comparison of eight multibeam bathymetric surveys acquired in the upper part of the Capbreton canyon between 1998 and 2018, in depths ranging 10–320 m below sea level. This rare time series exposes the morphological evolution of this outstanding dynamic area over the last 20 years. Our work shows that much of the changes are located in the canyon floor and head. Following a period characterized by a unique flat floor thalweg, the canyon was affected by an incision with low lateral terraces which resulted in a narrow axial thalweg. The deepening of the narrow thalweg was induced by retrogressive erosion according to the presence of upstream-migrating knickpoints, while low elevation residual terraces formed as the canyon reached a local equilibrium profile.The flat thalweg observed in 1998 is likely a result of a partial filling of the canyon thalweg by a substantial emptying of the canyon head and significant mass transfer to the proximal part of the canyon. A flat floor thalweg was not observed again in the remaining of our time series (since 2010), suggesting a possible quieter working mode of the canyon. We also propose the first accurate volume quantification of sediment displacement on the canyon floor. Our findings underline the alternation of filling and erosive periods in the canyon axis and an unexpected continuous sediment deposition in the canyon head during the last 20 years.

Priority and emerging micropollutants distribution from coastal to continental slope sediments: A case study of Capbreton Submarine Canyon (North Atlantic Ocean)

Incising continental margins, submarine canyons are key issue for understanding shelf/deep sea exchange of particulate pollutant, impact on marine ecosystem and global geochemical cycling. The occurrence and distribution of 100 priority and emerging micropollutants were investigated in sediments within the first 25 km of the Capbreton submarine area. The most predominant compounds were polycyclic aromatic hydrocarbons (PAHs), trace metals and metalloid (TMs) (e.g. mercury, lead and arsenic), synthetical musks (e.g. musk ketone, galaxolide), UV filters (e.g. octocrylene and 2-ethylhexyl 4-methoxycinnamate, EHMC) as well as some pharmaceuticals (e.g. azithromycin, acetaminophen). Highest concentrations were measured in submarine canyon sediments, distant from the coast and were correlated with both organic carbon and fine fraction contents, where PAHs, EHMC and musk ketone concentrations up to 7116, 32 and 7 ng g−1 dry weight, respectively. Those results likely demonstrate, that atmospheric inputs of pyrogenic PAHs, and both trapping and transporting of polluted particles along the continuum shore/deep sea by the Capbreton Canyon, might lead to an accumulation of anthropogenic micropollutants. The ecological risk assessment indicates that priority pollutants raise a potentially high risk for benthic organisms (e.g. PAHs, TMs). This might raised a specific concern about how the human can impact this ecosystem.

Genome-wide SNP based population structure in European hake reveals the need for harmonizing biological and management units

AbstractDespite its economic importance, the population structure of the European hake, Merluccius merluccius, is unresolved, and the species is assessed based on two stocks (northern and southern) separated by the Capbreton Canyon. In order to shed light into the European hake population structure, we used Restriction-site-Associated DNA sequencing (RAD-seq) to discover and genotype thousands of genome-wide single nucleotide polymorphisms in more than a hundred samples. Our population genetic inferences confirm differentiation of Mediterranean and northeast Atlantic locations and reveal management relevant information within the latter. First, hake in the Norwegian Sea is genetically different from that of the rest of the locations under study and, second, samples from the eastern Bay of Biscay and the northwestern Iberian Peninsula are not genetically different. These results imply that samples from the northern stock belong to different genetic populations, and that samples belonging to locations included in the northern and southern stocks are part of a single genetically homogeneous population. Although the definition of the boundary between the northern and southern stocks and the potential need for additional stocks still requires further analyses, the mismatch between biological and management units should already be considered in further assessments of European hake.

A new species ofSpiogalea(Polychaeta: Spionidae) from Brazil, with an amended diagnosis of the genus

A newSpiogaleaspecies is described from South-east Brazil. The specimens were collected in muddy bottoms during a large survey (15–3000 m) in southern Brazil. This genus comprised, up to now, only one species described from Capbreton Canyon (Bay of Biscay). The new species differs from the type-species, mostly in the morphology of the prostomial chitinous plate, a character restricted to the genusSpiogalea. With this new species, the generic diagnosis of the genus was amended.

Benthic foraminiferal response to sedimentary disturbance in the Capbreton canyon (Bay of Biscay, NE Atlantic)

Living (Rose Bengal stained) and dead benthic foraminifera were investigated at 6 deep-sea sites sampled in the Capbreton canyon area (Bay of Biscay, France). Three sites were located along the canyon axis at 301m, 983m and 1478m and 3 stations were positioned on adjacent terraces at 251m, 894m and 1454m. Sedimentary features indicate that frequent sedimentary disturbances of different magnitudes occur along the Capbreton canyon axis and adjacent terraces. Such environmental conditions cause the presence of very particular benthic environments. Along the 6 studied sites, different foraminiferal responses to various sedimentary patterns are observed revealing the complexity of this canyon environment. Some sites (Gitan 3 (canyon axis), Gitan 5 (canyon axis) and Gitan 6 (terrace)) are characterized by moderate to low standing stocks and low diversity and are mainly dominated by pioneer taxa such as Fursenkoina brady, Reophax dentaliniformis and Technitella melo suggesting a recent response to turbidite deposits recorded at these sites. Others sites (Gitan 1 and Gitan 2) show extremely high standing stocks and are mainly dominated by the opportunistic Bolivina subaenariensis and Bulimina marginata. Such faunal characteristics belonging to a more advanced stage of ecosystem colonization indicates strongly food-enriched sediment but extremely unstable conditions. Moderate standing stocks and diverse assemblage composed of species such as Uvigerina mediterranea and U. peregrina has only been observed at the terrace site Gitan 4. More stable sedimentary conditions recorded at this terrace seem to be suitable to the development of a dense and diverse foraminiferal community. Numerous neritic allochtonous species were observed in the dead foraminiferal fauna. These allochthonous species mainly originate from shelf areas (<60m).

Anobothrus amourouxisp. nov., a new species of Ampharetidae (Polychaeta) from the Capbreton Canyon (Bay of Biscay, NE Atlantic Ocean)

A new species of Ampharetidae,Anobothrus amourouxisp. nov., has been identified from bathyal depths of the Capbreton Canyon, Bay of Biscay (NE Atlantic Ocean). This new species is characterized by inner branchiae with transversal ciliated ridges, notochaetae from modified eighth thoracic unciniger with hirsute tips, uncini from thoracic unciniger with 6–7 teeth in lateral view arranged in two vertical rows in frontal view, fused segments II + III with paleae from SII and reduced notopodia without chaetae from SIII. An identification key for all hitherto described species of the genusAnobothrusis provided.

High frequency environmental changes and deposition processes in a 2 kyr-long sedimentological record from the Cap-Breton canyon (Bay of Biscay)

The core MD03-2693 (43°39.258′N; 01°39.805′W; 431 m water depth) was collected on an abandoned meander of the Capbreton Canyon (SE Bay of Biscay), filled over the last millennia by very high sedimentation rates (mean sedimentation rate of 1.2 cm/yr) linked to its specific environmental location and fine-grained clayed sediment decantation from the proximal canyon axis. This archive thus permits to undertake the study of late Holocene regional climatic patterns at a decadal temporal resolution. In the present work, we use data derived from planktonic foraminifera assemblages coupled to a multiproxy approach that associates grain-size measurements, x-ray fluorescence (XRF) elemental analysis and stable oxygen isotope on Globigerina bulloides shells to infer Sea Surface Temperature (SST) and Sea Surface Salinity (SSS) changes over the last two millennia. Signals reconstructed in the Bay of Biscay show significant oscillations that are consistent with well-known temperature anomalies such as the ‘Little Ice Age’ (LIA) and the ‘Medieval Warm Period’ (MWP). It additionally displays strong similarities with other areas in the western temperate and northern North Atlantic Ocean, suggesting a narrow coupling between its main gyre surface systems. Abrupt decrease of SSS together with significant change in terrigenous inputs suggests a change in precipitation regime at the onset of the LIA (around ad 1400). Moreover, superimposed to the relative long-term change in environmental parameter, the core MD03-2693 records rapid and discrete pulses of sand grain–sized material that are correlated with the local history of migration of the mouth of the Adour River.

Deep-sea Ampharetidae (Polychaeta) from Capbreton Canyon (north-east Atlantic) with the description of a new species

During the Capbreton cruises (1987–1990), samples of bathyal benthic macrofauna were taken at 37 stations situated along the continental slope (480–1113 m depth) of the Capbreton Canyon (Bay of Biscay, north-east Atlantic). Ten species of polychaetes belonging to six genera (Melinna, Eclysippe, Amphicteis,Anobothrus, GlyphanostomumandTanseimaruana) of the family Ampharetidae Malmgren, 1866 were collected at 13 of these stations. Most of these species are reported for the first time in the area.Amphicteisaff.wesenbergaeis reported for the first time after its recent description and a new species belonging to the genusGlyphanostomumis here described. Moreover, the finding ofMelinna monoceroidesrepresents the northernmost record of the species;Tanseimaruana vestisis recorded for the second time from the East Atlantic after its recent finding in Icelandic waters;Anobothrusaff.gracilisis reported for the second time from the Iberian Peninsula, representing, the southernmost record of the species in the Atlantic Ocean. The potential identification of two fragments of an Ampharetinae indet asAnobothrus laubieri, a deep water Arctic species, is discussed.

High-resolution morphobathymetric analysis and evolution of Capbreton submarine canyon head (Southeast Bay of Biscay—French Atlantic Coast) over the last decade using descriptive and numerical modeling

Abstract In this study, the Capbreton canyon head, just off the coast, is investigated using high-resolution multibeam bathymetry datasets, sediment samples and numerical modeling. The HR bathymetry analysis reveals a morphological connection between the longshore trough and the head of the canyon. The analysis of recent sediment samples shows a clear correlation between the sediment of the canyon head and that of the nearshore. Hydrodynamic modeling (a coupled wave-flow model) shows that for high-energy waves, the rotational nature of surf-zone circulation reverses and wave-induced currents have the potential to transport large quantities of nearshore sands toward the canyon head. All these arguments support the assumption that the canyon head captures a part of the sand transported by longshore drift. Over the 15 years of observation (1998–2013), time-lapse bathymetry shows that the floor of the canyon head and one lateral gully network experienced significant morphological reworking. In terms of hazards, despite this strong activity, the position of the canyon head and the profile of its longitudinal slope remained stable and appear as a comforting factor. However, the activity of unusual lateral erosions needs to be monitored.

2000years of frequent turbidite activity in the Capbreton Canyon (Bay of Biscay)

Abstract Capbreton Canyon extends from 200 m water depth near the Aquitanian coast to 3000 m water depth before abruptly turning northward and merging with the Cap-Ferret systems. The Capbreton Canyon has been disconnected from the Adour River input since 1310 AD. Despite this situation, modern sedimentary activity is evident in the first kilometres from the head. Present sedimentation in the Capbreton Canyon was studied by combined analysis of acoustic data and cores. Cores from the topographic highs document moderate hemipelagic sedimentation and record the global climatic signal of the Bay of Biscay. Within the canyon, at ± 80 km from the head, on terraces bordering the thalweg at 1600 m water depth, cores attest to recent turbidite activity. Massive medium sand is restricted to the thalweg floor, where sediment transfer dominates. Fine-grained turbidites are preferentially accumulated on the shallower terraces near the thalweg (the accumulation rate is 3 and 1 cm/year at 75 m and 125 m above the thalweg, respectively). On a higher terrace (225 m), turbidite sequences are absent or too thin to be preserved from bioturbation. The sedimentation rate is lower (approximately 0.17 cm/year) but still 10 times higher than the hemipelagic sedimentation outside the Capbreton Canyon. We demonstrate that frequent turbidity currents (1/year) are currently responsible for very high accumulation of dominantly fine-grained sediments on the terraces that are the nearest from the thalweg. We assume an impact of nepheloid layers on the sedimentation of the highest terraces. Looking for any impact on sediment supply of the disconnection of the Capbreton Canyon head from the Adour River mouth, it appears that the impact on the sedimentation affected the nature of the particles, which are less carbonate-rich, rather than the quantity of sediments. This result suggests that the longshore drift at the canyon head and hydrodynamic events are major factors in the sedimentation of Capbreton Canyon.

Benthic foraminifera from Capbreton Canyon revisited; faunal evolution after repetitive sediment disturbance

At a 650m deep site in the axis of Capbreton Canyon an 18-cm-thick turbidite was deposited in December 1999. During subsequent campaigns, an almost monospecific fauna of the benthic foraminifer Technitella melo, considered as a pioneer species, was found in May 2000. In 2001 this fauna had disappeared and was replaced by an exceptionally rich fauna strongly dominated by the opportunistic species Bolivina subaenariensis. We present sedimentological, radionuclide and foraminiferal data of new cores, sampled in 2005 and 2011, taken with the aim to study the further evolution of the benthic ecosystem. Cores sampled in 2005 show that in the canyon axis a new, ca. 5cm thick, turbidite has been deposited. The live benthic foraminiferal faunas were much poorer than in 2001, but still had a high dominance and low diversity, although less extreme than in 2001. We conclude that in the canyon axis, benthic foraminiferal faunas remain in an early stage of ecosystem colonization. It appears that the very thick 1999 turbidite marks an exceptional event. The uncommonly rich faunas observed in 2001 could be a response to the concentration of organic-rich material in the fine-grained top of this deposit. In 2011, cores were sampled at a slightly different site, on the lower canyon flank. The sedimentary sequence here is marked by the absence of coarse turbidite layers, although some levels show slightly increased grain size, and lower 210Pbxs activities, indicative of an admixture with advected older sediments. Live foraminiferal faunas are much more equilibrated, as shown by their higher diversity, lower dominance, and deeper penetration into the sediment. All these characteristics are indicative of a much more stable ecosystem. Dead faunas are present throughout the core, indicating that the levels with slightly elevated grain size are not typical turbidites resulting from hyperpycnal currents (which are characterized by levels barren of foraminifera) but denote other, more long-term sedimentary processes leading to the advection of older material, such as bottom nepheloid layers, or repetitive fine-grained turbidite deposits due to small-scale slumping. The comparison of live and dead fauna shows that at both sites, the foraminiferal turnover rates are fairly low. At the lower canyon flank site sampled in 2011, the foraminiferal faunas are renewed every 1.5–2years. Such a fairly long foraminiferal lifespan corresponds to earlier estimates, but is surprisingly high for the opportunistic taxa that dominate the faunal assemblages in these unstable and food-enriched submarine canyon settings.

Bathyal suprabenthic assemblages from the southern margin of the Capbreton Canyon (“Kostarrenkala” area), SE Bay of Biscay

The bathyal suprabenthic fauna of the Kostarrenkala area (Capbreton Canyon, SE Bay of Biscay) was sampled during daytime at eight stations located on a bathymetric transect between 175 and 1000m depth using a multinet suprabenthic sled. Two hundred and five suprabenthic taxa were recorded in this area, mainly amphipods, cumaceans, isopods and mysids. Total abundances ranged from 752 to 2640ind./100m2, showing a decreasing trend with depth. Diversity values (H′) ranged between 3.83 and 5.72, increasing significantly with depth. Multivariate analysis of abundance data discriminated three assemblages according to depth: shelf break (72 sp., 1924ind./100m2), upper slope (93 sp., 1485ind./100m2) and mid slope (135 sp., 857ind./100m2) assemblages. Each assemblage was characterised by a distinct dominant species: the shelf amphipod Westwoodilla caecula at the shelf break, the isopod Munnopsurus atlanticus on muddy sand bottoms of the upper bathyal, and the amphipod Rhachotropis gracilis on mid-slope muddy bottoms below the mud line. Such a structure of bathyal assemblages seems to be generalised for the whole margin of the Bay of Biscay.

A restricted fishing area as a tool for fisheries management: Example of the Capbreton canyon, southern Bay of Biscay

Marine Protected Areas (MPAs) are generally considered as one of the most important tools, among the many regulations, designed to preserve marine resources as well as enhance fisheries. In the southern Bay of Biscay, local French fishermen requested creation of a restricted area to help settle disputes between the various metiers operating there. This restricted area, which lies mainly in French waters, covers part of a deep submarine canyon off the French and Spanish coasts, known to have a large population of mature hake. This study aims to better understand the effects of a restricted area upon French fleets operating there, particularly upon three main metiers—longliners, gillnetters and trawlers. The study area includes three ICES statistical rectangles. The data, based upon reported landings and auctions sales for the period 1985–2008, were analyzed using multivariate analysis. The fishing activity is more important in one rectangle which includes the restricted area. Bottom longliners and gillnetters, operate mainly in this one while trawlers are less dependent. The first metier concentrates particularly on hake and the second has targeted other species and has become less dependent on hake. Trawlers target a wider range of species. Over the past ten years, the restricted area has contributed to maintain the fleets operating here. The border with Spain adds other constraints over the issue of access to regional fisheries and makes management a little more complicated.