• European Marine Science
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This is the Coriolis data center report on GTSPP activities for year 2018. Between January 2018 and December 2018, 37000 new profiles from 75 platforms where collected, controlled and distributed.

International audience; A unique late Glacial–Preboreal record of changes in sea-level and sediment fluxes originating from the Alps is recorded in the Rhône subaqueous delta in the Western Mediterranean Sea. The compilation of detailed bathymetric charts, together with high-resolution seismic profiles and long cores, reveals the detailed architecture of several sediment lobes, related to periods of decreased sea-level rise and/or increased sediment flux. They are situated along the retreat path of the Rhône distributaries, from the shelf edge and canyon heads up to the modern coastline. They form transgressive backstepping parasequences across the shelf, the late Holocene (highstand) deltas being confined to the inner shelf. The most prominent feature is an elongated paleo-shoreface/deltaic system, with an uppermost sandy fraction remolded into subaqueous dunes. A long piston core into the bottomsets of this prograding unit allows precise dating of this ancient deltaic system. In seismic data, it displays aggradation, starting at not, vert, similar 15 cal kyr BP, followed by progradation initiated during the first phase of the Younger Dryas, a period of reduced sea-level rise or stillstand. The delta kept pace with resumed sea-level rise during the Preboreal (which is estimated at about 1 cm/yr), as a result of increased sediment supply from the Alps (melting of glaciers and more humid climate “flushing” the sediment down to the sea). Abandonment of the delta occurred around 10,500 cal yr BP, that is to say about 1000 yr after the end of the Younger Dryas, probably because of decreased sediment flux.

Subduction of a narrow slab of oceanic lithosphere beneath a tightly curved orogenic arc requires the presence of at least one lithospheric scale tear fault. While the Calabrian subduction beneath southern Italy is considered to be the type example of this geodynamic setting, the geometry, kinematics and surface expression of the associated lateral, slab tear fault offshore eastern Sicily remain controversial. Results from a new marine geophysical survey conducted in the Ionian Sea, using high-resolution bathymetry and seismic profiling reveal active faulting at the seafloor within a 140 km long, two-branched fault system near Alfeo Seamount. The previously unidentified 60 km long NW trending North Alfeo Fault system shows primarily strike-slip kinematics as indicated by the morphology and steep-dipping transpressional and transtensional faults. Available earthquake focal mechanisms indicate dextral strike-slip motion along this fault segment. The 80 km long SSE trending South Alfeo fault system is expressed by one or two steeply dipping normal faults, bounding the western side of a 500+ m thick, 5 km wide, elongate, syntectonic Plio-Quaternary sedimentary basin. Both branches of the fault system are mechanically capable of generating magnitude 6–7 earthquakes like those that struck eastern Sicily in 1169, 1542, and 1693. peer-reviewed

International audience; Subduction mega-thrust earthquakes in the SW Ryukyu trench pose a seismic and tsunami hazard. One of the objectives of this study is to estimate the downdip width of the seismogenic zone using numerical modeling to determine the temperature distribution along the plate interface. However, this approach depends strongly on the thermal parameters of the subducting slab. While the Philippine Sea plate (PSP) subducting beneath the central and eastern Ryukyu arc is of Eocene age (35-50 Ma), its age west of the Gagua Ridge is uncertain, with proposed ages ranging from Lower Cretaceous (140 Ma) to Upper Eocene (35 Ma). Since the sparse available heat flow data are insufficient to resolve this debate, both end-member hypotheses are tested as input parameters. We examined two transects at 122.5°E and 123.5°E on either side of the N-S trending, 4-km high, Gagua Ridge. The shallow forearc geometry is obtained from wide-angle seismic data. The deep slab geometry was obtained from hypocenter distribution and tomography. For an Eocene slab age, we obtain a 100 km and 110 km wide seismogenic zone (between the 150 °C and 350 °C isotherms) west and east of Gagua Ridge, respectively. This is in good agreement with the observed distribution of hypocenters. Using a Cretaceous slab west of Gagua Ridge predicts a deep seismogenic zone (25 km-60 km depth), inconsistent with observed thrust earthquakes. Tomographic images at 122.5°E and 123.5°E show a similar slab thickness of 70-80 km suggesting that the oceanic lithosphere has a young (Eocene) thermal age. The westernmost PSP (Huatung Basin) may have been thermally rejuvenated by mantle convection near the slab corner. The tectonic history since 6 Ma (transition from subduction to collision beneath Taiwan) may have also perturbed the thermal structure.

Annually exploited communities from the Nile delta and two nearby lagoons (Manzalah and Edkou) were monitored from 1962 to 1989. The changes in community structure were analysed as a function of two events: fishing pressure growth (motorized fishing vessels) which increased by a factor of 19 between 1952 and 1962; and the construction of the Aswan Dam, which was built between 1965 and 1969, reducing the flow of the Nile by 90 %. Before the construction of the dam, increased sea fishing pressure led to a decline in landings from 33,832 tons in 1962 to 8,522 tons in 1969, but with no structural change in the exploited community. However, following completion of the dam in 1969, the community structure changed and a significant correlation was detected between landings and community diversity. After 1978, a period of variability in landings and the simultaneous reorganization of the communities occurred. By 1989, fish landings reached 32,025 tons, a level recorded before the construction of the Aswan dam In contrast With the previous period, there Was no longer a significant correlation between community structure and catches. Quantitative variations were observed in Manzalah Lagoon landings but with no modification in community structure. Con-elation between diversity and catches was found only in the Edkou Lagoon.

La Petite Mer de Gavres est une zone conchylicole, classée salubre, et exploitée en pêche à pied, avec une commercialisation directe difficile à contrôler. A la suite de problèmes de salubrité rencontrés sur les coquillages de cette zone, une étude bactériologique a été réalisée par IFREMER de juin 1986 à septembre 1987, suivie en 1988 d'une comparaison des contaminations des différentes espèces de coquillages. Ces études montrent que l'insalubrité de certains coquillages de la petite Mer de Gavres est particulièrement évidente pour les fouisseurs (coques et palourdes). Malgré la proximité des sources de pollutions de la Rade de Lorient et la petitesse du bassin versant de la Petite Mer, c'est ce dernier qui la contamine, notamment aux abords du bourg de Riantec qui apparaît nettement insalubre. Cette pollution par les eaux douces d'un bassin versant très limité induit évidemment une forte saisonnalité des contaminations qui augmentent significativement en automne-hiver.

Dans le cadre du suivi DCE du paramètre « macroalgue intertidale » de la masse d’eau FRFC11 « côte basque », 2 stations ont été échantillonnées en 2015 à partir du protocole adapté pour cette masse d’eau. La moyenne des notes des deux stations classe la masse d’eau en « Bon ». Les deux stations obtiennent des résultats très proches et sont classées dans la même catégorie Dans le calcul de l'indicateur, l’abondance des espèces opportunistes est le paramètre le moins bien noté. La comparaison de ces résultats avec le paramètre macroalgue subtidale est concordant. De même ce paramètre obtient des résultats similaire sur les masses d'eau côtières basques espagnoles. Under the WFD monitoring, the intertidal macroalga parameter of the water body FRFC11 « coast Basque », two stations were sampled in 2015 from the appropriate protocol for this water body. The average of the two stations takes the water body in « Good ». Both stations get very similar results but are not classified in the same category: « Good » . The abundance of opportunistic species is the worst notation. The comparison with results for subtidal macroalgae is consistent. Also, for intertidal macroalgae on Spanich Basque waterbodies results are very similar.

232 analyses d'eau et 125 tests biologiques de toxicité ont été effectués dans le cadre du réseau de suivi des perturbations phytoplanctoniques (REPHY) en période d'alerte (du 10 avril 90 au 10 septembre 90). L’ "épisode" Dinophysis a été très sévère cette année touchant presque tout le département. Les concentrations en Dinophysis dans l'eau ainsi que les teneurs en toxine des coquillages ont atteint des valeurs importantes entraînant de nombreuses fermetures de secteurs conchylicoles. Toutefois, les améliorations apportées cette année au réseau de suivi ont permis d'accentuer son efficacité. Enfin une meilleure diffusion de l'information a contribué à assurer la protection du consommateur.

Plastic pollution in the environment is increasing at global scale. Microplastics (MP) are derived from degradation of larger plastic items or directly produced in microparticles form (<5 mm). Plastics, widely used in structures and equipments of pearl farming, are a source of pollution to the detriment of the lagoon ecosystem. In order to evaluate the impact of MP on the physiology of Pinctada margaritifera, a species of ecological and commercial interests, adult oysters were exposed to polystyrene microbeads (micro-PS of 6 and 10 μm) for 2 months. Three concentrations were tested: 0.25, 2.5, 25 μg L-1 and a control. Ingestion and respiration rate and assimilation efficiency were monitored on a metabolic measurement system to determine the individual energy balance (Scope For Growth, SFG). Effects on reproduction were also assessed. The assimilation efficiency decreased significantly according to micro-PS concentration. The SFG was significantly impacted by a dose-dependent decrease from 0.25 μg L-1 (p < 0.0001). A negative SFG was measured in oysters exposed to 25 μg L-1. Gonads may have provided the missing energy to maintain animals’ metabolism through the production of metabolites derived from germ cells phagocytosis. This study shows that micro-PS significantly impact the assimilation efficiency and more broadly the energy balance of P. margaritifera, with negative repercussions on reproduction.