Effects of dietary methylmercury on the zebrafish brain: Histological, mitochondrial, and gene transcription analyses
The neurotoxic compound methylmercury (MeHg) is a commonly encountered pollutant in the environment, and constitutes a hazard for wildlife and human health through fish consumption. To study the neurotoxic impact of MeHg on piscivorous fish, we contaminated the model fish species Danio rerio for 25 and 50 days with food containing 13.5 μg/g dry weight (dw) of MeHg (0.6 μg MeHg/fish/day), an environmentally relevant dose leading to brain mercury concentrations of 30 ± 4 μg of Hg g$^-$$^1$ (dw) after 25 days of exposure and 46 ± 7 μg of Hg g$^-$$^1$ (dw) after 50 days. Brain mitochondrial respiration was not modified by exposure to MeHg, contrary to what happens in skeletal muscles. A 6-fold increase in the expression of the sdh gene encoding the succinate dehydrogenase Fe/S protein subunit was detected in the contaminated brain after 50 days of exposure. An up regulation of 3 genes, atp2b3a, atp2b3b, and slc8a2b, encoding for calcium transporters was noticed after 25 days of exposure but the atp2b3a and atp2b3b were repressed and the slc8a2b gene expression returned to its basal level after 50 days, suggesting a perturbation of calcium homeostasis. After 50 days, we detected the up regulation of glial fibrillary acidic protein and glutathione S-transferase genes (gfap and gst), along with a repression of the glutathione peroxidase gene gpx1. These results match well with a MeHg-induced onset of oxidative stress and inflammation. A transmission electron microscopic observation confirmed an impairment of the optical tectum integrity, with a decrease of the nucleal area in contaminated granular cells compared to control cells, and a lower density of cells in the contaminated tissue. A potential functional significance of such changes observed in optical tectum when considering wild fish contaminated in their natural habitat might be an impaired vision and therefore a lowered adaptability to their environment.
(BioMetals. vol. 25, n° 0966-0844, pp. 165-180, 11/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IBGC, UB, CNRS
Electroactivity of phototrophic river biofilms and constitutive cultivable bacteria
Electroactivity is a property of microorganisms assembled in biofilms that has been highlighted in a variety of environments. This characteristic was assessed for phototrophic river biofilms at the community scale and at the bacterial population scale. At the community scale, electroactivity was evaluated on stainless steel and copper alloy coupons used both as biofilm colonization supports and as working electrodes. At the population scale, the ability of environmental bacterial strains to catalyze oxygen reduction was assessed by cyclic voltammetry. Our data demonstrate that phototrophic river biofilm development on the electrodes, measured by dry mass and chlorophyll a content, resulted in significant increases of the recorded potentials, with potentials of up to +120 mV/saturated calomel electrode (SCE) on stainless steel electrodes and +60 mV/SCE on copper electrodes. Thirty-two bacterial strains isolated from natural phototrophic river biofilms were tested by cyclic voltammetry. Twenty-five were able to catalyze oxygen reduction, with shifts of potential ranging from 0.06 to 0.23 V, cathodic peak potentials ranging from 0.36 to 0.76 V/SCE, and peak amplitudes ranging from 9.5 to 19.4 µA. These isolates were diversified phylogenetically (Actinobacteria, Firmicutes, Bacteroidetes, and Alpha-, Beta-, and Gammaproteobacteria) and exhibited various phenotypic properties (Gram stain, oxidase, and catalase characteristics). These data suggest that phototrophic river biofilm communities and/or most of their constitutive bacterial populations present the ability to promote electronic exchange with a metallic electrode, supporting the following possibilities: (i) development of electrochemistry-based sensors allowing in situ phototrophic river biofilm detection and (ii) production of microbial fuel cell inocula under oligotrophic conditions.
(Applied and Environmental Microbiology. vol. 77, n° 0099-2240, pp. 5394-5401, 11/04/2026)
LEFE, INEE-CNRS, CNRS, UT3, Comue de Toulouse, CNRS, Toulouse INP, Comue de Toulouse, UR REBX, CEMAGREF, CAI, INRA, ENSIACET, Toulouse INP, Comue de Toulouse, Toulouse INP, Comue de Toulouse, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Comments on "Stratigraphic, sedimentological and palaeoenvironmental constraints on the rise of the Urgonian platform in the western Swiss Jura.", by Godet, A., K. B. Föllmi et al., in Sedimentology vol. 57 (2010), pp. 1088-1125.
(Sedimentology. vol. 59, n° 0037-0746, pp. 1121-1125, 11/04/2026)
UCBL, CR2P, MNHN, UPMC, CNRS, LDO, INSU - CNRS, UBO EPE, CNRS, UEB
Hurricanes and climate in the Caribbean during the past 3700 years BP
A multiproxy analysis of lacustrine sediments cored in Grand-Case Pond at Saint-Martin, north of the Lesser Antilles archipelago, reveals three distinct climatic periods for the last 3700 years. From 3700 to ~2500 yr cal. BP and from 1150 yr cal. BP to the present, carbonate mud deposition occurred in connection with pond lowstands. These periods were also punctuated by severe drought events, marked by gypsum laminae, and hurricane landfalls, leading to marine sand inputs into the pond. The intermediate time interval, from 2500 to 1150 yr cal. BP, is typified by black organic mud deposition, suggesting that hypoxic to anoxic conditions prevailed at the pond bottom. These were probably linked with a perennial pond highstand and reflect more uniform and wetter climatic conditions than today. The carbon isotopic composition of the ostracod Perissocytheridea bisulcata shows that the lowest δ13C values are recorded during the hypoxic periods, as a consequence of bacterial recycling of isotopically depleted organic matter. Such a climatic history agrees closely with that documented from other records in the Caribbean area, such as the Cariaco Basin, central coast of Belize or Barbados. By constrast, discrepancies seem to emerge from the comparison between hurricane activity recorded at Saint-Martin on the one hand and Vieques (Puerto Rico) on the other hand. We explain this apparent contradiction by a balance between two distinct storm paths in response to latitudinal shifts of the Intertropical Convergence Zone (ITCZ). Stronger storm activity over the Gulf coast and the inner Caribbean Sea is favoured by a southern position of the ITCZ in connection with dry climatic conditions. Plausible links with the North Atlantic Oscillation (NAO) are also suggested.
(The Holocene. vol. 21, n° 0959-6836, pp. pp. 911-924, 11/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, Inrap, LAMPEA, AMU, CNRS, MC, GEODE, UT2J, Comue de Toulouse, CNRS, UAG, BioArch, MNHN, CNRS, SRA Guadeloupe, DAC Guadeloupe
Comments on "The Depth-Dependent Current and Wave Interaction Equations: A Revision
Equations for the wave-averaged three-dimensional momentum equations have been published in this journal. It appears that these equations are not consistent with the known depth-integrated momentum balance, especially over a sloping bottom. These equations should thus be considered with caution, because they can produce erroneous flows, particularly outside of the surf zone. It is suggested that the inconsistency in the equations may arise from the different averaging operators applied to the different terms of the momentum equation. It is concluded that other forms of the momentum equations, expressed in terms of the quasi-Eulerian velocity, are better suited for three-dimensional modeling of wave–current interactions.
(Journal of Physical Oceanography. vol. 41, n° 0022-3670, pp. 2008 - 2012, 11/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LOS, IFREMER, SHOM
A new 3D fully wave-current model MARS-WW3: development, validation and application to surf zone
(17/12/2010)
M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS, LOS, IFREMER, DYNECO, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Evolution décennale des zones côtières
Ne couvrant que 8% de l’océan mondial mais offrant 85% des ressources marines exploitées, les systèmes côtiers sont d’importantes plaques tournantes d’échanges de matières et d’énergie, jouant un rôle capital dans les cycles biogéochimiques. De plus, ces milieux sont marqués par une forte hétérogénéité spatio-temporelle des facteurs environnementaux, contribuant ainsi à leur complexité. Au cours des dernières décennies, les changements globaux s'exerçant sur ces systèmes sont devenus si intenses, que la mise en place de réseaux d'observation à long-terme est devenue cruciale afin d'extraire les grandes tendances et de prédire les changements potentiels. La question de l'identification de la réponse spécifique de ces zones d'interfaces littorales reste cependant posée. En France, le suivi des paramètres physiques et chimiques des eaux côtières est assuré depuis 1997 par le programme SOMLIT (Service d’Observation en Milieu LIToral). L'objectif de cette thèse est donc de caractériser l'évolution physico-chimique, à l'échelle décennale, des systèmes côtiers français et d'estimer les parts respectives de la variabilité naturelle et de l'influence anthropique. Dans un premier temps, l'analyse de ces séries chronologiques montre que les systèmes côtiers français présentent une variabilité temporelle importante, liée en partie aux fluctuations hydroclimatiques à méso-échelle, mais également à des échelles plus régionales. Dans un deuxième temps, le développement d'une nouvelle procédure multivariée non paramétrique, aboutissant à la construction d'états de référence relatifs et à la détection rapide des changements, permet de quantifier le phénomène de fertilisation en nutriments. Il est montré que la fertilisation peut être fortement influencée par le forçage climatique. Dans un troisième temps, après soustraction de la part de variabilité climatique naturelle, des indicateurs de fertilisation anthropique sont proposés, permettant la quantification de l'impact des activités humaines sur les systèmes côtiers français. Ce travail propose une nouvelle approche qui permet de détecter dès que les données deviennent accessibles les perturbations potentielles dans tous types de systèmes, avec plus particulièrement pour objectif de répondre aux attentes, scientifiques et sociétales, d'une gestion adaptée des milieux côtiers.
(17/12/2010)
LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Contribution to the Holocene North Atlantic wind activity reconstruction from Lake Igaliku, South Greenland
(. vol. Vol. 1, 13/12/2010)
LCE, CNRS, UFC, UBFC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ArScAn, UP1, UP8, UPN, MCC, CNRS, ACS, MCC, UB, CNRS
Sea ice and wind variability during the Holocene in East Antarctica: insight on middle–high latitude coupling
Micropaleontological and biomarker data from two high-accumulation marine sites from the Coastal and Continental Shelf Zone (CCSZ) off East Antarctica (Adélie Land at w140 E and eastern Prydz Bay at w77 E) are used to reconstruct Holocene changes in sea ice and wind stress at the basin-wide scale. These data demonstrate congruent increase in sea-ice concentration/persistence and wind stress-related sea-surface turbulence in the two regions since 7 cal ka BP, with a particularly strong signal since 4.5 e3.5 cal ka BP. Comparison of these high latitude records with sea ice and turbulence records from the southern mid-latitudes highlights distinctive climatic evolutions according to the different latitudinal bands. Sea-ice persistence and turbulence increase in East Antarctica CCSZ are opposite to sea-surface warming and sea-ice retreat recorded after 4.5e3.5 cal ka BP in the East Atlantic and Indian sector between 55 and 45 S. At the same period, paleodata suggest SST cooling in all major coastal upwelling systems of the southern hemisphere, caused by the northward transport of subpolar surface waters as a response to southern Westerlies reinforcement. We therefore propose, as suggested for the northern hemisphere, that Holocene changes in the latitudinal insolation gradient, primarily forced by obliquity and precession and amplified by sea-ice and glacial-ice expansions in the Antarctic realm, are responsible for the observed contrasted latitudinal patterns of southern latitudes.
(Quaternary Science Reviews. vol. 29, n° 0277-3791, pp. 3709-3719, 01/12/2010)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LOCEAN, IPSL, ENS-PSL, PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, IP Paris, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, VU
La "Zone minéralisée de l'Entre-deux-Mers" : Caractérisation hydrogéologique, géochimique et isotopique - CARISMEAU 2.
Au nord du Bassin Adour-Garonne, la ressource en eau principalement exploitée pour l'alimentation en eau potable est l'aquifère Eocène (masse d'eau 5071). Le projet de recherche CARISMEAU 2, initié début 2009 s'inscrit étroitement dans le cadre de la Directive Cadre sur l'Eau. Il vise à mieux comprendre les hétérogénéités et les interconnections au sein de la masse d'eau 5071. En effet, cet aquifère présente des teneurs anomaliques en sulfates et fluor qui induisent des difficultés d'exploitation de la ressource. L'origine de ces minéralisations excessives, réparties de façon hétérogène, n'est pas encore connue. Le projet CARISMEAU 2, auquel est associée la thèse " Zone minéralisée de l'Entre-deux-Mers ", met en application une approche couplée hydrogéologique, géochimique et isotopique. Les objectifs sont de mieux connaître l'origine de la salinité et de définir les circulations de ces eaux minéralisées dans l'aquifère Eocène, lui-même compris au sein du système aquifère multicouche du Bassin aquitain. Afin de mieux caractériser cette masse d'eau, une cinquantaine de points ont été suivis fin 2009. Des méthodes de géochimie et de géochimie isotopique classiques sont utilisées, mais aussi des méthodes isotopiques innovantes et/ou expérimentales. Les premiers résultats des analyses géochimiques et multi-isotopiques sont présentés dans l'objectif de mieux comprendre l'origine de ces éléments, leur comportement et leur migration dans les aquifères.
(25/11/2010)
BRGM, EGID, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS