Mercury distribution in fish organs and food regimes: significant relationships from twelve species collected in French Guiana (Amazonian basin)
(Science of the Total Environment. vol. 368, n° 0048-9697, pp. 262-270, 01/09/2006)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LMBA, UBS, UBO EPE, CNRS
Metallothionein response to cadmium and zinc exposures compared in two freshwater bivalves, Dreissena polymorpha and Corbicula fluminea
Metallothionein (MT) response to cadmium (Cd) and zinc (Zn) bioaccumulation after single or combined direct exposure was compared in two freshwater bivalves, Dreissena polymorpha (zebra mussel) and Corbicula fluminea (Asiatic clam). Bivalves were exposed to 0.133 microM Cd and/or 15.3 microM Zn, with metal and MT concentrations analysed in the whole soft body after 1, 3, 10 and 24 days of exposure and compared with controls. Results showed significant increase in MT concentrations in both species exposed to Cd and Cd+Zn with a higher accumulation of the protein compared to the control in D. polymorpha for nevertheless similar Cd levels accumulated with time. Exposure to Zn alone led to a significant increase in MT concentrations only in C. fluminea, whereas there was a lack of MT gene induction in the zebra mussels which was confirmed by MT mRNA quantification in gills (RT-PCR). Mussel mortality after 10 days of exposure to Zn and Cd + Zn is discussed with regard to detoxification mechanisms, which include metallothioneins.
(BioMetals. vol. 19, n° 0966-0844, pp. 399-407, 01/08/2006)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Metal adsorption by diatoms: A surface complexation model
Not Available
(Geochimica et Cosmochimica Acta. vol. 70, n° 0016-7037, pp. 197, 01/08/2006)
LMTG, UT3, Comue de Toulouse, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
$^{234}$Th sorption and export models in the water column: A review
Over the past few decades, the radioisotope pair of $^{238}$U/$^{234}$Th has been widely and increasingly used to describe particle dynamics and particle export fluxes in a variety of aquatic systems. The present paper is one of five review articles dedicated to $^{234}$Th. It is focused on the models associated with $^{234}$Th whereas the companion papers (same issue) are focused on present and future methodologies and techniques (Rutgers van der Loeff et al.), C/$^{234}$Th ratios (Buesseler et al.), $^{234}$Th speciation (Santschi et al.) and present and future applications of $^{234}$Th (Waples et al.). In this paper, we review current $^{234}$Th scavenging models and discuss the relative importance of the non steady state and physical terms associated with the most commonly used model to estimate $^{234}$Th flux. Based on this discussion we recommend that for future work the use of models should be accompanied by a discussion of the effect that model and data uncertainty have on the model results. We also suggest that future field work incorporate repeat occupations of sample sites on time scales of 1-4 weeks in order to evaluate steady state versus non steady state estimates of $^{234}$Th export, especially during high flux events (> ca. 800 dpm m$^{-2}$ d$^{-1}$). Finally, knowledge of the physical oceanography of the study area is essential, particularly in ocean margins and in areas of established upwelling (e.g. Equatorial Pacific). These suggestions will greatly enhance the application of $^{234}$Th as a tracer of particle dynamics and flux in more complicated regimes.
(Marine Chemistry. vol. 100, n° 0304-4203, pp. 234-249, 01/08/2006)
VUB, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, SBU, SUNY, WHOI, WHOI, WHOI, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GEDI, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, VUB
Variations climatiques interannuelles à interdécennales dans le Pacifique Tropical telles qu’enregistrées par les traceurs géochimiques contenus dans les coraux massifs
L'étude des paléoclimats tropicaux est importante pour cerner les variabilités climatiques liées au changement global et, à terme, l'augmentation de la capacité de prédiction climatique. A ce titre, les coraux massifs apparaissent comme d'excellents enregistreurs des climats marins tropicaux. Ainsi les variations du contenu géochimique des squelettes des coraux massifs varient corollairement à l'évolution des paramètres environnementaux. Ce travail met en évidence l'intérêt d'analyses couplées (isotopes stables δ18O et δ13C et éléments trace, Sr/Ca, U/Ca, Ba/Ca, Mg/Ca et Ba/Ca) pour comprendre entre autre la variabilité des températures et des salinités de surface de l'océan. Les méthodes existantes ainsi que celles développées dans le cadre de cette étude lors de la phase de calibration sont appliquées à deux sites d'étude situés dans le Pacifique tropical Sud Ouest. Ainsi, plus de 500 ans d'enregistrement des températures et des salinités sont reconstruites en continu, montrant des variations de type interdécennales marquées, qui s'expliquent essentiellement par la courantologie des masses d'eaux au Sud de l'île de la Nouvelle Calédonie. De forts événements ENSO (El Niño Southern Oscillation) ont également été mis en évidence aux alentours de 1600. L'autre site d'étude, Wallis, d'interprétation plus complexe, semble présenter des variations liées aux modulations basse fréquence de la SPCZ (South Pacific Convergence Zone). Finalement, ces résultats sont remis en perspective dans un cadre plus général et une synthèse des différents outils offerts aux paléoclimatologues est produite, incorporant les résultats issus des présents travaux.
(10/07/2006)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Ammonoïdes du Smithien (Trias inférieur) du Nord‐Ouest du Guangxi (Chine du Sud) et modélisation biogéographique de la récupération biotique des ammonoïdes après l'extinction de masse Permien/Trias
L'extinction de masse permo‐triasique (~252 Ma) a décimé plus de 90% des espèces marines vivant à cette époque. La récupération biotique consécutive était jusqu'alors considérée comme extrêmement lente (~10 millions d'années). Dans ce contexte, les ammonoïdes (céphalopodes) du Trias inférieur constituent un ensemble phylogénétiquement bien contraint d'organismes marins abondant dans le registre fossile, et donc particulièrement appropriés à l'étude de l'impact des conditions climatiques et océaniques (températures [SST], courants, etc.) sur les dynamiques macroécologiques et biogéographiques post‐crise. Afin d'appréhender l'impact relatif de ces paramètres, nous avons élaboré un modèle de simulation 2D, dit modèle « géophylétique », où les SST et les courants forcent la dispersion géographique d'un ensemble phylogénétique généré aléatoirement. Les simulations indiquent que la forme et l'intensité du gradient latitudinal de diversité résultent de la combinaison de deux effets « milieu de domaine », l'un géographique et l'autre thermique, en lien avec la forme et l'intensité du gradient de SST : plus celui‐ci est marqué, plus le gradient de diversité est accentué. Ces résultats sont comparés aux données fossiles, augmentées de plusieurs nouvelles faunes du Smithien de Chine du Sud, présentées ici sous une forme monographique. Celles‐ci indiquent que les ammonoïdes sont, après la crise permo‐triasique, parmi les organismes marins les plus rapides à se re‐diversifier et à reconquérir l'océan mondial (< ~2 ma). Le début du Trias inférieur est marqué par un gradient latitudinal de diversité très faible, avec de très nombreux genres cosmopolites. Ce gradient de diversité s'accentue progressivement durant le Trias inférieur, en lien avec une augmentation de la différentiation latitudinale et du degré d'endémisme des faunes. Cette accentuation correspond vraisemblablement au développement d'un fort gradient latitudinal de SST au cours du Trias inférieur.
(07/07/2006)
PEPS, UCBL, INSU - CNRS, CNRS, LMTG, UT3, Comue de Toulouse, CNRS
A 27 kyr terrestrial biomarker record in the southern Indian Ocean
[1] Terrestrial inputs were reconstructed using high molecular weight n-alkane concentrations recorded in the sub-Antarctic Indian Ocean core MD94-103 (45°35 0 S, 86°31 0 E, 3560 m) to examine regional changes in the atmospheric circulation over the last 27 kyr. This record was compared to the dust content of EPICA-Dome C ice and continental data from South Africa (e.g., pollen sequences and isotope records in speleothems) to get a comprehensive understanding of atmospheric links between low and midlatitudes of the Indian Ocean. Terrestrial n-alkanes indicate higher glacial than Holocene inputs and marked glacial oscillations. Minimum values during the Last Glacial Maximum (LGM) are consistent with colder and drier climate and presumably caused by the persistence of subtropical anticyclones over southern Africa limiting the amount of rainfall and vegetation growth. The otherwise higher glacial n-alkanes suggest a stronger influence of the tropical rainfall in southern Africa, likely associated with a contraction of the polar vortex with respect to its LGM position. During northern Heinrich events, moderate decline of n-alkanes suggests reduced rainfall over southern Africa possibly caused by weaker tropical easterly winds when, according to Stott et al. (2002), the Pacific Ocean would have experienced Super-ENSO conditions. Components: 5185 words, 3 figures.
(Geochemistry, Geophysics, Geosystems. vol. 7, pp. n/a-n/a, 01/07/2006)
LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, CLIMAG, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
First Record and Description of Metacercariae of Curtuteria Arguinae N. Sp. (Digenea: Echinostomatidae), Parasite of Cockles Cerastoderma Edule (Mollusca: Bivalvia) in Arcachon Bay, France
A new Himasthlinae species, Curtuteria arguinae, is described as metacercariae from the cockle Cerastoderma edule (L.), collected at Banc d'Arguin (southwestern France). These metacercariae encysted preferentially in the mantle and also in the foot of cockles. Encysted and chemically excysted metacercariae were studied by light microscopy and scanning electron microscopy, respectively. Excysted metacercariae were elongated and curved ventrally. They bore a 33-spine circumoral collar. Sensory papillae were arranged around the oral sucker and also symmetrically along the ventral surface body, from the collar to the acetabulum. The dorsal and ventral tegument surfaces were densely packed with similar pointed spines. The posterior end of the body was without any spines. Among the Curtuteria species described previously, only Curtuteria haematopodis Smogorjewskaja and Iskova, 1966 had the same number of circumoral collar spines. A 6-yr field survey showed that the cockle population at Banc d'Arguin was subjected to a summer infection of C. arguinae. Curtuteria arguinae phenology of infection is characterized by interannual variability and seasonality (beginning in July–August and maximum in autumn). The first intermediate and final hosts remain unknown.
(Journal of Parasitology. vol. 92, n° 0022-3395, pp. 578-587, 01/06/2006)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Comparative Effects of Direct Cadmium Contamination on Gene Expression in Gills, Liver, Skeletal Muscles and Brain of the Zebrafish (Danio rerio)
The effects of cadmium (Cd) on gene expression were examined in four organs (gills, liver, skeletal muscles and brain) of the zebrafish. Adult male fish were subjected to three different water contamination pressures over periods of 7 and 21 days: control medium (C(0): no Cd added) and two contaminated media (C(1): 1.9 +/- 0.6 microg Cd l(-1), and C(2): 9.6 +/- 2.9 microg Cd l(-1)). Fourteen genes involved in antioxidant defences, metal chelation, active efflux of organic compounds, mitochondrial metabolism, DNA repair and apoptosis were selected and their expression levels investigated by quantitative real-time PCR. Cadmium concentrations were determined in the four organs and metallothionein (MT) protein levels investigated in brain, liver and gills. Although skeletal muscle was a poor Cd-accumulating tissue, many genes were up-regulated at day 7: mt1, cyt, bax, gadd and rad51 genes. Three additional genes, c-jun, pyc and tap, were up-regulated in muscles at day 21 whereas bax, gadd and rad51 had returned to basal levels. Surprisingly, mt1 and c-jun were the only genes displaying a differential induction after 21 days in liver, although this organ accumulated the highest cadmium concentration. In brain, only mt1, mt2 and c-jun genes were up-regulated after 21 days. In gills, the highest response was observed after 7 days, featuring the differential expression of oxidative stress-response hsp70 and mitochondrial sod genes, along with genes involved in mitochondrial metabolism and metal detoxification. Then, after 21 days, the expression of almost every genes returned to basal levels while both mt1 and mt2 genes were up-regulated.
(BioMetals. vol. 19, n° 0966-0844, pp. 225-235, 01/06/2006)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Impact of digenean parasite infection on metallothionein synthesis by the cockle (Cerastoderma edule): A multivariate field monitoring
Metallothioneins (MT) are proteins that play an important role in metabolism of essential metals and detoxification of trace metals from living organisms. Their synthesis is induced by metal pollution but can also be exacerbated by other factors such as reproduction processes. In this context, we monitored MT concentrations in a cockle Cerastoderma edule (marine bivalve) population and highlighted the effect of a castrating digenean parasite, Labratrema minimus. In spent cockles, MT levels were low (ca. 5 nmol sites g−1, fresh weight) but slightly higher in parasitized individuals. During gametogenesis, MT synthesis increased in all cockles, but concentrations were lower in parasitized individuals (18 against 27 nmol sites g−1, fw in unparasitized cockles) in relation with gonad damage by parasites. Therefore, it is suggested that parasite infection in cockles can modulate MT synthesis that could consequently interfere with the response of these protective proteins in case of metal contamination.
(Marine Pollution Bulletin. vol. 52, n° 0025-326X, pp. 494-502, 01/05/2006)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS