Cartographie AMT du biseau salé sur le flanc sud du Piton de la Fournaise (Ile de la Réunion)

Dans le secteur du Baril, situé sur la planèze sud du volcan de la Fournaise, l'interprétation unidimensionnelle (1-D) de 34 sondages AMT montre une séquence à trois terrains, avec disparition du deuxième dans la zone côtière. Cette séquence comprend un horizon supérieur résistant (> 1000 Ohm.m), un horizon intermédiaire plus conducteur (100 à 600 Ohm.m), et un substratum très conducteur (< 10 Ohm.m). Les résistivités obtenues permettent d'assimiler ce substratum au biseau salé. Les variations importantes dans la topographie du toit du biseau salé apportent des données nouvelles concernant les phénomènes de pénétration saline dans les aquifères volcaniques et, indirectement, une meilleure connaissance de la géométrie et du fonctionnement de l'aquifère sus-jacent. (Résumé d'auteur

Impact of freshwater on a subarctic coastal ecosystem under seasonal sea ice (southeastern Hudson Bay, Canada) : 3. Feeding success of marine fish larvae

We monitored the feeding success (percent feeding incidence at length and mean feeding ratio at length) of Arctic cod (#Boreogadus saida) and sand lance (#Ammodytes sp. larvae in relation to prey density, light, temperature and potential predator density under the ice cover of southeastern Hudson Bay in the spring of 1988, 1989 and 1990. Both prey density and light limited larval fish feeding. The relationship between feeding success and actual food availability (nauplii density x irradiance) was adequately described by an Ivlev function which explained 64 and 76% of the variance in Arctic cod and sand lance feeding success respectively. By affecting both prey density and irradiance, the thickness of the Great Whale River plume (as defined by the depth of the 25 isohaline) was the main determinant of prey availability. Arctic cod and sand lance larvae stopped feeding when the depth of the 25 isohaline exceeded 9 m. Limitation of feeding success attributable to freshwater inputs occurred exclusively in 1988, the only time when the depth of the 25 isohaline exceeded the 9 m threshold. The close dependence of larval fish feeding success on the timing of the freshet and plume dynamics suggests a direct link between climate and survival of Arctic cod and sand lance larvae. The actual impact of climate fluctuations and/or hydro-electric developments on recruitment will depend on the fraction of the larval dispersal area of the two species that is affected by river plumes. (Résumé d'auteur

Debris avalanches on the western flank of Piton des Neiges shield volcano (Reunion Island)

Les faciès bréchiques reconnus à terre dans la région littorale de Saint-Gilles, sur le flanc ouest du volcan Piton des Neiges, sont clairement identifiés comme des dépôts d’avalanche de débris. Leur étude pétrographique, texturale et structurale permet de montrer, grâce à la présence de coulées autochtones interstratifiées, qu’au moins quatre glissements successifs se sont produits. Le premier est de grande ampleur puisqu’il affecte la zone centrale hydrothermalisée du volcan. Il est proposé que ce premier glissement, favorisé par la présence de matériaux ayant subi une importante altération hydrothermale, crée une zone d’instabilité qui influe sur le comportement ultérieur du Piton des Neiges. Dans ce même secteur, les glissements postérieurs concernent uniquement des domaines plus superficiels, mettant en jeu des matériaux non hydrothermalisés et vacuolaires. La bréchification des formations, et en particulier la désagrégation progressive des “blocs” durant le transport de l’avalanche de débris, implique une vitesse de progression élevée. Dans la zone du Cap La Houssaye, l’abrasion et la striation des formations laviques situées sous les unités bréchiques, ainsi que les phénomènes de tassement observés, sont interprétés comme des figures d’arrêt de l’avalanche

Benthic oxygen fluxes in a coastal upwelling system (Ria de Vigo, NW Iberia) measured by aquatic eddy covariance

Organic carbon mineralization and nutrient cycling in benthic environments are critically important for their biogeochemical functioning, but are poorly understood in coastal up - welling systems. The main objective of this study was to determine benthic oxygen fluxes in a muddy sediment in the Ria de Vigo (NW Iberian coastal upwelling), by applying the aquatic eddy covariance (AEC) technique during 2 campaigns in different seasons (June and October 2017). The main drivers of benthic fluxes were studied and compared among days in each season and between seasons. The 2 campaigns were characterized by an upwelling-relaxation period followed by a downwelling event, the last of which was due to the extratropical cyclone Ophelia in October. The mean (±SD) seasonal benthic oxygen fluxes were not significantly different for the 2 campaigns despite differences in hydrodynamic and biogeochemical conditions (June: -20.9 ± 7.1 mmol m-2d-1vs. October: -26.5 ± 3.1 mmol m-2d-1). Benthic fluxes were controlled by different drivers depending on the season. June was characterized by sinking labile organic material, which enhanced benthic fluxes in the downwelling event, whereas October had a significantly higher bottom velocity that stimulated the benthic fluxes. Finally, a comparison with a large benthic chamber (0.50 m2) was made during October. Despite methodological differences between AEC and chamber measurements, concurrent fluxes agreed within an acceptable margin (AEC:benthic chamber ratio = 0.78 ± 0.13; mean ± SD). Bottle incubations of water sampled from the chamber interior indicated that mineralization could explain this difference. These results show the importance of using non-invasive techniques such as AEC to resolve benthic flux dynamicsPostprin

The travel demands of an elite rugby sevens team: Effects on objective and subjective sleep parameters

Purpose: To explore the effects of travel related to international rugby sevens competition on sleep patterns. Methods: Seventeen international male rugby sevens players participated in this study. Sleep assessments were performed daily during two separate Sevens World Series competition legs (Oceania and America). The duration of each competition leg was subdivided into key periods (pre-tour, pre-competition, tournament 1 and 2, relocation and post-tour) lasting 2 to 7 nights. Linear mixed models in combination with magnitude-based decision were used to assess 1) the difference between pre-season and key periods and 2) the effect of travel direction (eastward or westward). Results: Shorter total sleep time (hh:mm) was observed during tournament 2 (mean ± SD, 06:16 ± 01:08), relocation (06:09 ± 01:09) and pre-tour week (06:34 ± 01:24) compared with pre-season (06:52 ± 01:00). Worse sleep quality (AU) was observed during tournament 1 (6.1 ± 65 2.0) and 2 (5.7 ± 1.2) as well as during the relocation week (6.3 ± 1.5) than during pre-season (6.5 ± 1.8). When traveling eastward compared with westward, earlier fall asleep time was observed during tournament 1 (ES -0.57, 90%CI [-1.12 to -0.01]), relocation week (-0.70 [-1.11 to -0.28]), and post-tour (-0.57 [-0.95 to -0.18]). However, possibly trivial and unclear differences were observed during pre-competition week (0.15 [-0.15 to 0.45]) and tournament 2 (0.81 [-0.29 to 1.91]). Conclusion: Sleep patterns of elite rugby sevens players are robust to the effects of long-haul travel and jet lag. However, staff should consider promoting sleep during the tournament and 73 relocation week

Spatial and temporal distribution of the minke whale, <i>Balaenoptera acutorostrata</i> (Lacépède, 1804), in the southern northeast Atlantic Ocean and the Mediterranean Sea, with reference to stock identity

New strandings, bycatch and sightings data for minke whales in the northeast Atlantic Ocean south of Cape Finisterre (Galicia) and the Mediterranean Sea were combined with earlier authenticated records, in order to re-assess spatial and temporal distribution, and provide clues to breeding areas and stock identity. The southern range of IWC-defined Northeastern Atlantic and Central North Atlantic stocks with no explicit, but a de facto, boundary of the Equator, was explored in particular. Senegal (6 records), Mauritania (1) and Western Sahara/Southern Morocco (3) are new West African Range States for the North Atlantic minke whale. Morocco and The Gambia are likely Range States. Specimens stranded or captured in Senegal and Mauritania were either calves (n=6) or neonate (n=1), a strong indication for a near-by calving ground. Juveniles and calves (median SL:418cm, n=6) commonly occur off the Canary Islands, without apparent seasonality. Two strandings, one of which was a neonate (in February), were documented in the Azores. Evidence of minke whales is lacking for Madeira and the Cape Verde Islands. The temporal distribution of 33 records from the western coasts of the Iberian Peninsula in the period 1905-1998 included all seasons, but 76% were registered in spring and summer (March-August). The majority of animals were juveniles (mean SL:537.5cm, n=26); none were neonates. Minke whales were encountered in low numbers in the western and central Mediterranean Sea mostly from March to November, although documented strandings in December and February argue for a year round presence. The Ligurian and Tyrrhenian Seas and the Gulf of Lion are concentration areas, presumably (cf. fin whales) linked to the abundance of euphausiids. Small calves (SL:300-360cm) suggest that at least some females give birth in the Mediterranean. An unusual stranding in the eastern Black Sea (Georgia) may be related to migration of schooling fish. The southernmost specimen known from the North Atlantic is a calf captured near Hann (14º41'N, 17º27'W), Senegal, in May. Southernmost sightings include: (a) inshore: a foraging individual at Garnet's Bay (24º51'N, 15º05'W) in November; (b) offshore: three minke whales at 10°40'N, 22°00'W in December. While small, the sample from West Africa does not seem to support a restricted, seasonal presence. Most likely, these individuals constitute the offspring and juveniles from the Northeastern Atlantic and/or Central North Atlantic populations, but an unrecognised local population cannot be discounted. Preliminary cladistic analysis of the mtDNA control region of one Senegal minke whale yielded equivocal results depending on the fragment sequenced. Field research in the region should be continued to provide the necessary samples to resolve the question of stock identity

The secretion inhibitor Exo2 perturbs trafficking of Shiga toxin between endosomes and the trans-Golgi network

The small-molecule inhibitor Exo2 {4-hydroxy-3-methoxy-(5,6,7,8-tetrahydrol[1]benzothieno[2,3-d]pyrimidin-4-yl)hydraz-one benzaldehyde} has been reported to disrupt the Golgi apparatus completely and to stimulate Golgi–ER (endoplasmic reticulum) fusion in mammalian cells, akin to the well-characterized fungal toxin BFA (brefeldin A). It has also been reported that Exo2 does not affect the integrity of the TGN (trans-Golgi network), or the direct retrograde trafficking of the glycolipid-binding cholera toxin from the TGN to the ER lumen. We have examined the effects of BFA and Exo2, and found that both compounds are indistinguishable in their inhibition of anterograde transport and that both reagents significantly disrupt the morphology of the TGN in HeLa and in BS-C-1 cells. However, Exo2, unlike BFA, does not induce tubulation and merging of the TGN and endosomal compartments. Furthermore, and in contrast with its effects on cholera toxin, Exo2 significantly perturbs the delivery of Shiga toxin to the ER. Together, these results suggest that the likely target(s) of Exo2 operate at the level of the TGN, the Golgi and a subset of early endosomes, and thus Exo2 provides a more selective tool than BFA for examining membrane trafficking in mammalian cells