Internal waves generated by a moving sphere and its wake in a stratified fluid
The internal gravity waves and the turbulent wake of a sphere moving through stratified fluid were studied by the fluorescent dye technique. The Reynolds number Re=U·2a/v was kept nearly constant at about 3 · 103 and the Froude number F;U/a N ranged from 0.5 to 12.5. It is observed that waves generated by the body are dominant only when F<4 and are replaced by waves generated by the large scale coherent structures of the wake when F>4.
(Experiments in Fluids. vol. 11, n° 0723-4864, pp. 255-261, 01/07/1991)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Mercury accumulation in delphinidae
The aim of this work is an attempt to synthetize the different results of our researches on dolphin's contamination by Hg and their interpretation. It is based on the results obtained following the total Hg determination in several organs of 35 specimens of Stenella coeruleoalba stranded on French Atlantic and Mediterranean coasts and 45 Stenella attenuata captured in the Eastern tropical Pacific. Considering our present knowledge on Hg ecotoxicological processes, the trophic route, via cumulative Hg transfers through the marine trophic network, can be considered as the major contamination route for the dolphins. However, considering the influence of the geographical origin of the individuals it also seems reasonable to assume that the principal contamination source of the high Hg concentrations observed in pelagic dolphins are natural metal deposits.
(Water, Air, and Soil Pollution. vol. 56, n° 0049-6979, pp. 187-201, 23/05/1991)
IMS, UB, CNRS, Bordeaux INP, ENSC, IMS, UB, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UBM
Comparative study of mercury accumulation in dolphins (Stenella coeruleoalba) from French Atlantic and Mediterranean coasts
Total mercury concentrations (Hgt) have been determined in liver, kidneys, skeletal muscle, melon, stomach and intestine of 35 specimens of Stenella coeruleoalba stranded on French Atlantic and Mediterranean coasts. Very high mercury levels, with concentrations reaching 80 mg Hgt kg−1 fresh weight (FW) in muscle and about 1500 mg Hgt kg−1 FW in liver tissue, were observed. Liver has the highest concentration, followed by muscle and kidney. The lowest concentrations were found in the melon. The levels observed in the Mediterranean specimens are among the highest observed in marine organisms and confirm previous reports of high mercury levels in marine mammals from the Mediterranean. Comparison between Hgt accumulation levels in these two geographic groups of dolphins shows that Mediterranean individuals have much higher concentrations than specimens from the Atlantic. These differences provide additional confirmation for the higher Hgt concentrations observed previously in other pelagic species (tuna, sardine, anchovy, etc.) from the Mediterranean Sea. Taking into consideration the pelagic habitat of the dolphin and the local influence of anthropogenic mercury sources it seems reasonable to assume that the main source of the high mercury concentrations observed in Mediterranean biota is natural mercury deposits located in many regions of the Mediterranean basin.
(Science of the Total Environment. vol. 104, n° 0048-9697, pp. 191-209, 23/05/1991)
UB, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
La distribution des kystes de Dinoflagellés dans les sédiments hémipélagiques (Ardèche) et pélagiques (Arc de Castellane, S.E. de la France) en domaine vocontien, du Valanginien terminal au Barrémien inférieur - Biostratigraphie et relations avec la stratigraphie séquentielle.
Deux coupes du Crétacé inférieur vocontien (SE de la France) représentant les milieux pélagiques (Clue de Vergons ; Alpes-de-Haute-Provence) et hémipélagiques (Ravin des Buissières ; Ardèche) ont été étudiées d'un point de vue palynologique (dinoflagellés essentiellement). Bien datées par les faunes d'ammonites, ces séries ont été recalées sur la stratigraphie séquentielle (modèle de Vail) dont les discontinuités ont été reconnues in situ sur chacun des affleurements. Réalisé sur 105 échantillons, l'inventaire original des dinokystes de ces séries a abouti à la reconnaissance de près de 190 taxons. Une biozonation basée sur les extensions stratigraphiques et les assemblages des dinokystes est proposée. Elle est comparée à celle fournie par les faunes d'ammonites ainsi qu'à la stratigraphie séquentielle : la dinozonation établie s'avère être une échelle biostratigraphique rarement dépendante des deux autres. Au niveau des cycles de 3ème ordre, aucune relation systématique n'est observable entre les discontinuités séquentielles et les assemblages de dinokystes. Quelques corrélations sont proposées au niveau des cycles de 2ème ordre (reconnaissance de l'intervalle transgressif ; remontée générale du niveau marin). D'un point de vue biostratigraphique, ces résultats locaux sont replacés dans un cadre plus global et comparés avec les dinozonations des principaux bassins du Crétacé inférieur. S'appuyant sur les variations du contenu des assemblages de dinokystes, sur les variations de fréquences de certains taxons, un essai de paléoécologie a été réalisé : certains paramètres environnementaux tels que variations du niveau marin, éloignement à la côte ou salinité de surface ont pu être appréhendés, indiquant une remontée globale du niveau marin de la base au sommet de l'Hauterivien. Le rapport de genres Muderongia/Phoberocysta permet de proposer un schéma des variations du niveau marin, en particulier pour l'Hauterivien inférieur.
(15/10/1990)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Mercury contamination levels and distribution in tissues and organs of delphinids (Stenella attenuata) from the Eastern Tropical Pacific, in relation to biological and ecological factors
(Marine Environmental Research. vol. 30, n° 0141-1136, pp. 43 - 72, 01/01/1990)
IMS, UB, CNRS, IMS, UB, CNRS, ENSC, Bordeaux INP, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Les modalités de la reproduction de la coque (Cerastoderma edule) sur le littoral français de la Manche et de l'Atlantique
Le cycle sexuel de Cerastoderma edule a été étudié durant l'année 1987 sur plusieurs sites le long du littoral atlantique français, de la baie de Somme au bassin d'Areachon. Cette étude vise à définir les modalités de la ponte et les facteurs qui la régissent, afin d'identifier à ce niveau, les causes de la variabilité du recrutement. Dans ce but, une méthode commune est mise en œuvre. Elle repose essentiellement sur la reconnaissance des stades de maturité sexuelle et sur les fluctuations de l'indice de condition. Les pontes peuvent être : précoce, printanière, estivale ou tardive, et, selon leur nombre et leur importance, variables selon les sites. La première ponte apparaît toujours en réponse au stimulus thermique qui correspond, au printemps, à l'amélioration des conditions climatiques et trophiques. A l'intérieur de l'espace latitudinal défini, il n'apparaît pas de net gradient au niveau des pontes, ce qui démontre que celles-ci ne sont pas déclenchées par une valeur définie de la température. L'efficacité de la ponte printanière est liée à une valeur seuil de l'indice de condition. Le nombre et l'intensité des pontes estivales et automnales sont fonction de l'importance de la ponte printanière. Il en résulte une forte variabilité dans les conditions de recrutement. Dans l'optique recherchée, certains principes prédictifs peuvent cependant être avancés.
(Aquatic Living Resources. vol. 3, n° 0990-7440, pp. 29 - 41, 01/01/1990)
LOPS, IRD, IFREMER, INSU - CNRS, UBO EPE, CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BOREA, UNICAEN, NU, MNHN, IRD, SU, CNRS, UA, LIENSs, INSU - CNRS, ULR, CNRS
Alkylated phenanthrene distribution in artificially matured kerogens from Kimmeridge clay and the Brent Formation (North Sea)
Kerogen and extractible organic matter from immature Kimmeridge clay and Brent coal were heated at different temperatures (270-500°C) under conditions to mimic natural maturation. Aromatic fractions have been examined for their phenanthrene compound distribution. Phenanthrene indices based on methylphenanthrenes (MP) and dimethylphenanthrenes (DMP) exhibit very sensible changes in the applied temperature range. However, at high temperatures (about 450°C and more) possible thermal degradation of phenanthrene compounds produces a decrease in the values of the indices. Experimental data obtained in this study are compared and discussed with data obtained on thermal evolution performed on total rocks. Vitrinite reflectance values measured on artificially matured coals are also tentatively correlated with phenanthrene ratios. Theoretical thermodynamic calculations on MP compounds confirm also the relative thermal stability of the individual isomers. \textcopyright 1990.
(Organic Geochemistry. vol. 16, n° 0146-6380, pp. 167--173, 23/05/1990)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LPTC, UB, CNRS
Cadmium contamination of tissues and organs of delphinids species (Stenella attenuata)—Influence of biological and ecological factors
Based on a sample of 27 dolphins (Stenella attenuata) captured in the Eastern tropical zone of the Pacific Ocean, this study was carried out to analyze the cadmium accumulation levels and distribution in 12 organs or tissue samples. The average cadmium concentrations were between 0.2 mg Cd · kg−1 in the brain and muscle and 48 mg Cd · kg−1 in the kidneys. For most of organs and tissues the average values were between 1 and 5 mg Cd · kg−1. Kidneys, liver, muscle, and intestine contained almost 85% of the total cadmium burden of all tissues considered in this study. Most of the biological and ecological factors taken into account (age, sex, total weight, and length of the dolphins, weight of the organs, place and date of capture) interacted with the cadmium concentrations and burdens in the collected organs or tissues. Three factors appear to be of prime importance: age, body weight, and geographical location of the area of capture.
(Ecotoxicology and Environmental Safety. vol. 20, n° 0147-6513, pp. 290-306, 23/05/1990)
ENSC, IMS, UB, CNRS, IMS, UB, CNRS, UN, IUML, UM, UA, UN, ECN, UBS, IFREMER, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Distribution of methylperylene isomers in selected sediments
Surface and deep sediment extracts, containing perylene compounds, have been examined by High Resolution Shpol'skii Spectroscopy. The first identification of the three methylperylene isomers is reported and indicates the predominance of 2-methylperylene among the methylperylene isomer distributions at any maturation stage. Perylene itself was nevertheless always found to be the most abundant perylene compound. \textcopyright 1988.
(Geochimica et Cosmochimica Acta. vol. 52, n° 0016-7037, pp. 901--907, 23/05/1988)
LPTC, UB, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LPPM, UB
Trace analysis of aromatic compounds in natural samples by Shpol'skii spectroscopy
Low molecular weight aromatic compounds (acenaphthene, acenaphthalene, fluorene, phenanthrene and anthracene) were difficult to detect due to their low fluorescence quantum yield. To evaluate the accuracy of this method, we have analyzed several organic extracts (diesel particulate, air particulate). The results (imprecision less than 15%) obtained by Shpol'skii spectroscopy have been compared with values obtained by other analytical methodologies (HPLC coupled with fluorescence detection, GC coupled to mass spectrometry). Good agreement is observed among the three analytical techniques, demonstrating the reliability of Shpol'skii spectroscopy for quantitative analysis.
(Journal of research of the National Bureau of Standards. vol. 93, pp. 441--443, 23/05/1988)
LPTC, UB, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS