Acoustic and optical variations during rapid downward motion episodes in the deep north-western Mediterranean Sea

An Acoustic Doppler Current Profiler (ADCP) was moored at the deep-sea site of the ANTARES neutrino telescope near Toulon, France, thus providing a unique opportunity to compare high-resolution acoustic and optical observations between 70 and 170 m above the sea bed at 2475 m. The ADCP measured downward vertical currents of magnitudes up to 0.03 m s-1 in late winter and early spring 2006. In the same period, observations were made of enhanced levels of acoustic reflection, interpreted as suspended particles including zooplankton, by a factor of about 10 and of horizontal currents reaching 0.35 m s-1. These observations coincided with high light levels detected by the telescope, interpreted as increased bioluminescence. During winter 2006 deep dense-water formation occurred in the Ligurian subbasin, thus providing a possible explanation for these observations. However, the 10-20 days quasi-periodic episodes of high levels of acoustic reflection, light and large vertical currents continuing into the summer are not direct evidence of this process. It is hypothesized that the main process allowing for suspended material to be moved vertically later in the year is local advection, linked with topographic boundary current instabilities along the rim of the 'Northern Current'.Comment: 30 pages, 7 figure

The ThomX project status

Work supported by the French Agence Nationale de la recherche as part of the program EQUIPEX under reference ANR-10-EQPX-51, the Ile de France region, CNRS-IN2P3 and Université Paris Sud XI - http://accelconf.web.cern.ch/AccelConf/IPAC2014/papers/wepro052.pdfA collaboration of seven research institutes and an industry has been set up for the ThomX project, a compact Compton Backscattering Source (CBS) based in Orsay - France. After a period of study and definition of the machine performance, a full description of all the systems has been provided. The infrastructure work has been started and the main systems are in the call for tender phase. In this paper we will illustrate the definitive machine parameters and components characteristics. We will also update the results of the different technical and experimental activities on optical resonators, RF power supplies and on the electron gun

Etude écologique et génétique des populations d'un dinoflagellé benthique toxique, Ostreopsis cf. ovata, en Méditerranée Nord Occidentale.

National audienceEtude écologique et génétique des populations d'un dinoflagellé benthique toxique, Ostreopsis cf. ovata, en Méditerranée Nord Occidentale

Importance of the large copepod Paraeuchaeta antarctica (Giesbrecht, 1902) in coastal waters and the diet of seabirds at Kerguelen, Southern Ocean

International audienceThe importance of the euchaetid copepod Paraeuchaeta antarctica in the subantarctic pelagic ecosystem was quantified in the coastal waters of the Golfe du Morbihan at Kerguelen Islands by comparing food samples from two diving seabirds with concurrent net samples taken within the predator foraging area. Paraeuchaeta antarctica occurred in very high densities (up to 30 individuals m–3 and 96 mg dry weight m–3) in the water column, being more abundant in the deepest part of the gulf than in shallow waters or at the more offshore shelf stations. The common diving petrel feeds almost exclusively on crustaceans, its diet being dominated by the amphipod Themisto gaudichaudii (52% by number and 84% by reconstituted mass) and P. antarctica (33% and 16%, respectively). Rockhopper penguins preyed upon crustaceans and fish, with four taxa being important, namely T. gaudichaudii (37% and 23%, respectively), Euphausia vallentini (24% and 41%), postlarval fish (10% and 24%), and P. antarctica (13% and 3%). Paraeuchaeta antarctica dominated numerically in 21% of the diving-petrel food samples and in 12% of penguin samples. The two bird species segregated by preying upon different developmental stages of P. antarctica, diving petrels fed equally on CV of both sexes and CVI, while penguins fed on CVI only. Comparison of P. antarctica found in net and food samples indicated no prey selection by common diving petrels that caught the different copepod stages in proportion to their availability in the water column. On the other hand, the diving performance of penguins, which is better than that of the petrels (mean maximum dive depths 69 m for penguins versus 32 m in petrels), allows them to catch CVI in deeper waters, probably near the bottom. Our study shows that P. antarctica is a major component of the coastal macrozooplankton community and a significant prey for two species of diving seabirds inhabiting Kerguelen. This is also the first record of a copepod species as a prey for penguin, and the first to highlight P. antarctica in the food of austral seabirds

Le massif d'Aran (Pyrénées-Atlantiques, France). Bilan des recherches spéléologiques

Poster. Colloque international A.F.K. (Association Française de Karstologie) ; A.R.D.K. ; A.R.S.I.P. : Le karst, indicateur performant des environnements passés et actuel, Arette, Pierre Saint-Martin, 6-9 septembre 200

Development of the benthic toxic dinoflagellate Ostreopsis cf. ovata in Monaco (NW Mediterranean sea).

Development of the benthic toxic dinoflagellate Ostreopsis cf. ovata in Monaco (NW Mediterranean sea)

Impacts des facteurs environnementaux sur le développement d'Ostreopsis cf. ovata durant les étés 2007 et 2008 à Monaco (Méditerranée Nord-Occidentale).

National audienceImpacts des facteurs environnementaux sur le développement d'Ostreopsis cf. ovata durant les étés 2007 et 2008 à Monaco (Méditerranée Nord-Occidentale)

Impact of environmental factors on Ostreopsis cf. ovata dynamic during the summers 2007 and 2008 in Monaco (NW Mediterranean Sea).

Impact of environmental factors on Ostreopsis cf. ovata dynamic during the summers 2007 and 2008 in Monaco (NW Mediterranean Sea)