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Despite being generally located far from contamination sources, deep marine ecosystems are impacted by chemicals like PCB. The PCB contamination in five fish and shark species collected in the continental slope of the Gulf of Lions (NW Mediterranean Sea) was measured, with a special focus on intra- and interspecific variability and on the driving factors. Significant differences occurred between species. Higher values were measured in Scyliorhinus canicula , Galeus melastomus and Helicolenus dactylopterus and lower values in Phycis blennoides and Lepidorhombus boscii . These differences might be explained by specific abilities to accumulate and eliminate contaminant, mostly through cytochrome P450 pathway. Interindividual variation was also high and no correlation was observed between contamination and length, age or trophic level. Despite its major importance, actual bioaccumulation of PCB in deep fish is not as documented as in other marine ecosystems, calling for a better assessment of the factors driving individual bioaccumulation mechanisms and originating high variability in PCB contamination. [ABSTRACT FROM AUTHOR]

Polybromodiphenyl ethers (PBDEs) in superficial sediments from the Gulf of Lion were studied. They were largely predominated by BDE 209 (98.7% of all PBDEs) indicating that the main source of these pollutants was the commercial mixture deca-BDE. This compound and the less brominated BDE exhibited a southwestward decreasing concentration gradient following the dominant marine currents and bottom relief, e.g. the Mud Belt, the submarine canyons and the Open Continental Slope. All PBDEs exhibited statistically significant correlations confirming the common origin. However, a progressive transformation of the dumped BDE 209 was identified showing a depletion paralleled by increases of the less brominated BDEs (from 8.6% to 22%). These less brominated compounds were accumulated at about 100–140km away from the Rhone prodelta, e.g. at the end of the submarine canyons, evidencing that these transformation compounds can be accumulated at long distances from the dumping sites in the marine system. [Copyright &y& Elsevier]

The Var prodelta progrades across a straight, narrow shelf (less than 2 km wide) with a very steep continental slope reaching locally more than 30°. Historically, the Var delta front is sadly famous for the 1979 catastrophic submarine landslide that resulted in several casualties and infrastructural damage. Geotechnical and geophysical investigations carried out in late 2007 to the east of the 1979 landslide scar provide evidence for the possible occurrence of a new important sedimentary collapse and submarine landslide. Geophysical data acquired in the area show the presence of several seafloor morphological steps rooted to shallow subsurface seismic reflections. Moreover, in situ piezocone measurements demonstrate the presence of several shear zones at the border of the shelf break at different depths below the seafloor. The aim of this technical note is to present and discuss acquired geotechnical and geophysical data in terms of failure mechanisms and submarine landslides. Both geophysical and geotechnical data suggest the start-up of a progressive failure mechanism and reveal the possible occurrence of a submarine landslide and the urgent need for mitigation procedures. Le système prodeltaïque du Var prograde directement sur une plateforme étroite (inférieure à 2 km de large) jusqu’à une pente continentale abrupte, supérieure à 30°localement. Historiquement, le delta du Var est malheureusement célèbre pour la catastrophe de 1979 provoquée par un glissement sous-marin ayant entrainé des victimes et des dommages matériels. Les explorations géotechniques et géophysiques menées fin 2007 dans la partie orientale de la cicatrice du glissement de 1979 témoignent de la forte probabilité que des effondrements sédimentaires à venir provoquent à nouveau des glissements sous-marins. Les données géophysiques acquises sur la zone montrent l'existence de plusieurs terrasses morphologiques sur le fond de la mer connectées en profondeur à des surfaces sismiques superficielles. De plus, les mesures in-situ des piezocones démontrent la présence de plusieurs zones de cisaillement en rebord de plateau à plusieurs profondeurs sous le fond de la mer. L’objectif de cette note est de présenter et discuter les données géotechniques et géophysiques acquises en relation avec les mécanismes de rupture et de glissement sous-marin. L’ensemble de ces données met en évidence l’initiation d'un processus progressif de rupture qui pourrait être à l’origine d’un possible glissement sous-marin; il révèle l’urgente nécessité de mettre en place des procédures pour la réduction des risques. [ABSTRACT FROM AUTHOR]

The "Landes-Parentis area" (LPA) is located at the transition between the eastern end of the abyssal plain of the Bay of Biscay to the west, the Acquitaine basin to the east and the highly inverted Basque-Cantabrian basin (BCB) to the south, whichrepresents the main, but distant, Pyrenean deformation front. The LPA includes the Meso-Cenozoic Parentis basin (PB) bordered to the south by a Paleozoic high named the "Landes High" (LH). The purpose of the study is to describe the reactivation of an aborted rift following the Late Jurassic to Late Cretaceous extension and then during inversion from the Upper Cretaceous onward. One also questions the importance of the presence of a rigid block in the setting up of this system.We analyzed seven regional 2D seismic lines through the LPA: EW lines from the coast to the abyssal plain and NS lines from the LH to the Armorican margin. We mapped the main structures and picked the stratigraphic unconformities. We used PB well data for the age dating of the different unconformities.The maps show that the Mesozoic cover observed in the PB extends to the foot of the continental slope while the Jurassic and Lower Cretaceous series lack or are very reduced on the LH. On the contrary, Tertiary deposits are present throughout the study area. The LPA is crossed by a NW-SE oriented, sinistral accident: the Landes transfer zone (LTZ), which correlates to a set of NW-SE normal faults on the LH. This LTZ segments the LPA in two distinct domains, an eastern and a western area. In the eastern domain, the contact area between the PB and LH presents an asymmetry between a gentle south dipping northern flank and a steep and faulted southern flank in a direct contact with LH. The southern flank of the PB shows EW-oriented anticlinal structures, attributed to salt ripples, normal faults inverted during the Tertiary and ramp anticlines. A major mid-albian unconformity truncates the sediment pile. In the western domain, the southern flank presents a different structural scheme with two tilted blocks limited by EW-oriented crustal faults with a north-dipping normal movement. The Upper Cretaceous to Tertiary sedimentary deposits seal these faults with no mid-albian unconformity. The structural scheme is mainly extensive.The lateral partitioning of the local deformation is strongly influenced by the presence of LH that play the role of a rigid block and of the LTZ that segments the basin in two different domains aligned on the South Armorican direction. This LTZ could be an heritage of the Mesozoic opening of the Bay of Biscaye. [ABSTRACT FROM AUTHOR]