Differential δ13C and δ15N signatures among scallop tissues: Implications for ecology and physiology

International audienceThere have been several studies where the isotopic composition of organisms has been determined seasonally, but fewer have examined separate organs. In this context, separate organs (e.g. gonad, digestive gland and muscle), of a suspension-feeder, the scallop Pecten maximus, were used to assess seasonal changes of both stable isotopes and biochemical components. Our study used multiple indicators (stable carbon and nitrogen isotopes ratios, biochemical components and seston Chl a) to track nutritive activity and energy allocation in P. maximus from the Bay of Brest (France). In addition to seasonal variation in the isotopic composition of P. maximus tissues, we found strong differences in the mean isotopic signatures of different organs. This has serious implications for interpretation of animal diets and potential use in animal physiology. Furthermore, we present evidence that seasonal variations of metabolism will cause changes in the isotopic composition not related to changes in the diet. Interpretation of isotopic data may require consideration of values from several separate organs. Finally, 15N appears powerful to track metabolite fates in the scallop P. maximus

An assessment of particulate organic carbon to thorium-234 ratios in the ocean and their impact on the application of 234Th as a POC flux proxy

Author Posting. © The Authors, 2006. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Marine Chemistry 100 (2006): 213-233, doi:10.1016/j.marchem.2005.10.013.Thorium-234 is increasingly used as a tracer of ocean particle flux, primarily as a means to estimate particulate organic carbon export from the surface ocean. This requires determination of both the 234Th activity distribution (in order to calculate 234Th fluxes) and an estimate of the C/234Th ratio on sinking particles, to empirically derive C fluxes. In reviewing C/234Th variability, results obtained using a single sampling method show the most predictable behavior. For example, in most studies that employ in situ pumps to collect size fractionated particles, C/234Th either increases or is relatively invariant with increasing particle size (size classes >1 to 100’s μm). Observations also suggest that C/234Th decreases with depth and can vary significantly between regions (highest in blooms of large diatoms and highly productive coastal settings). Comparisons of C fluxes derived from 234Th show good agreement with independent estimates of C flux, including mass balances of C and nutrients over appropriate space and time scales (within factors of 2-3). We recommend sampling for C/234Th from a standard depth of 100 m, or at least one depth below the mixed layer using either large volume size fractionated filtration to capture the rarer large particles, or a sediment trap or other device to collect sinking particles. We also recommend collection of multiple 234Th profiles and C/234Th samples during the course of longer observation periods to better sample temporal variations in both 234Th flux and the characteristic of sinking particles. We are encouraged by new technologies which are optimized to more reliably sample truly settling particles, and expect the utility of this tracer to increase, not just for upper ocean C fluxes but for other elements and processes deeper in the water column.Individuals and science efforts discussed herein were supported by many national science programs, including the U.S. National Science Foundation and U.S. Department of Energy. S.F. and J.C.M. acknowledge the support provided to the International Atomic Energy Agency (IAEA) Marine Environment Laboratory by the Government of the Principality of Monaco. T.T. acknowledges support from the Australian Antarctic Science Program. K.B. was supported in part by a WHOI Ocean Life Institute Fellowship

Evolution long-terme des communautés planctoniques autotrophes dans les écosystèmes côtiers : tendances pluriannuelles

Bien que les écosystèmes côtiers ne représentent que 8,5 % de la surface totale des océans, ils contribuent pour près de 60 % de la valeur économique générée. Une partie des services rendus par ces écosystèmes dépend de la structure du réseau trophique planctonique. La diversité taxonomique et morphologique de ce compartiment et sa sensibilité aux conditions environnementales lui permettent d’évoluer rapidement face aux fluctuations générées par les changements globaux. Les modifications long-terme des conditions environnementales ont des effets sur la structure, la phénologie et la biogéographie de ces communautés et donc sur le fonctionnement des écosystèmes. Cette étude s’inscrit dans le cadre d’un travail de thèse dont l’objectif principal est d’étudier ces modifications pour l’ensemble des communautés phytoplanctoniques (du pico- au micro-phytoplancton) du littoral français en lien avec des facteurs abiotiques. Elle s’appuie sur le réseau des Parcs Naturels Marins (PNM), une catégorie d’aires marines protégées réparties sur le littoral français, afin de préfigurer un observatoire du changement climatique. Ce travail mobilisera les données acquises par les Services Nationaux d’Observation (SNO) et de surveillance SOMLIT, PHYTOBS et le réseau REPHY. Dans le cadre de ce colloque, les tendances long-terme des communautés phytoplanctoniques et des facteurs environnementaux, calculées à partir de Modèles Linéaires Dynamiques (DLM), seront présentées pour le site Teychan/Tès du Bassin d’Arcachon. Ces premiers résultats obtenus pour le Bassin d’Arcachon serviront de base méthodologique pour être appliqués à l’ensemble des autres sites étudiés afin de dresser les trajectoires écologiques des différentes façades maritimes et faire une intercomparaison multi-sites

Imagerie fonctionnelle du tube digestif

résuméROUEN-BU Médecine-Pharmacie (765402102) / SudocPARIS-BIUM (751062103) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Fistulizing perianal Crohn's disease : contrast-enhanced magnetic resonance imaging assessment at 1 year on maintenance anti-TNFalpha therapy.

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Fistulizing perianal Crohn's disease : contrast-enhanced magnetic resonance imaging assessment at 1 year on maintenance anti-TNFalpha therapy.

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MR imaging of fistulizing perianal Crohn's disease : prospective study of semiological changes induced by anti-TNF therapy

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