On the variability of yellow substance in the skagerrak and the kattegat Auteur(s) : Karabashev, Gs Khanaev, Sa Kuleshov, Af Éditeur(s) : Gauthier-Villars Résumé : The variability of ''yellow substance'' in waters of the Skagerrak and the Kattegat was studied during the international Skagex programme in 1990 and 1991. Data on attenuation of light and fluorescence of dissolved organic matter (DOM) in sea water were collected with a spectral transmissiometer and a submersible fluorometer within a depth range of 0-250 m at several stations. More than fifty-fold variations of fluorescence intensity over space and time were due to the combined action of different sources of DOM in the straits. The surface maximum of fluorescing DOM, related to river outflow, was spreading from Oslo fjord to the central Skagerrak in late spring. This maximum may be ecologically important because it diminishes shortwave PAR. In the autumn the brightest DOM fluorescence was found in the Kattegat and along the Norwegian coast in accordance with earlier studies. The local minima of DOM fluorescence are associated with the Jutland current. Both the instability of the current and a ten-fold difference in DOM content between deep layers of the Skagerrak and Kattegat resulted in strong synoptic variability of fluorescence in the transitional area between the straits. Seasonal and synoptic variabilities of ''yellow substance'' were minimal in the southern Kattegat. The vertical gradients of DOM fluorescence were mostly negative at the depth of the thermocline of the open Skagerrak in spring, reaching values of 40-50 % m-1. Fine structure and complex shape were inherent to fluorescence profiles from areas of intensive water mixing. DOM fluorescence closely covaried with attenuation of UV light: the correlation coefficient was + 0.9 for wavelength w <= 350 nm regardless of season. The inverse dependence between wavelength derivative and magnitude of UV attenuation in the straits did not change with season. DOM fluorescence and water salinity were negatively correlated at depths of 25-50 m but they varied independently in the upper 10 m. No significant correlation between fluorescence and nitrates has been found. Estimates of correlation with phosphates ranged from 0.7 to 0.8. In general, the changes of fluorescence were due to variations of DOM content in sea water but not to variability of DOM composition or state. The properties of DOM fluorescence in the Skagerrak-Kattegat area make it a useful natural tracer of water movements suitable for active remote sensing with airborne lidar. Oceanologica Acta (0399-1784) (Gauthier-Villars), 1993 , Vol. 16 , N. 2 , P. 115-125 Droits : info:eu-repo/semantics/openAccess http://archimer.ifremer.fr/doc/00099/21041/18667.pdf http://archimer.ifremer.fr/doc/00099/21041/ | Partager |
Monomethylmercury sources in a tropical artificial reservoir Auteur(s) : Muresan, B Cossa, Daniel Richard, Sophie Dominique, Y Éditeur(s) : Elsevier Résumé : The distribution and speciation of mercury (Hg) in the water column, the inputs (wet deposition and tributaries) and the outputs (atmospheric evasion and outlet) of an artificial partially anoxic tropical lake (Petit-Sa-Lit reservoir, French Guiana) were investigated oil a seasonal basis in order to appraise the cycling and transformations of this metal. The total mercury (HgT) concentrations in the oxygenated epilimnetic waters averaged 5 +/- 3 pmol L-1 in the unfiltered samples (HgTUNF) and 4 +/- 2 pmol L-1 in the dissolved (HgTD) phase (< 0.45 mu m). On average, the monomethylmercury (MMHg) constituted 8%, 40%, and 18% of the HgT in the dissolved phase, tile particulate suspended matter and in tile unfiltered samples, respectively. Covariant elevated concentrations of particulate MMHg and chlorophyll a in the epilimnion suggest that phytoplankton is ail active component for the MMHg transfer in tile lake. In the anoxic hypolimnion the HgTUNF averages 13 +/- 6 pmol L-1 and tile HgTD 8 +/- 4 pmol L-1. The averages of MMHgP and MMHgD in hypolimnetic waters were two and three times the corresponding values of the epilimnion, 170 +/- 90 pmol g(-1) and 0.9 +/- 0.5 pmol L-1, respectively. In the long dry and wet seasons, at the flooded forest and upstream dam sampling stations, the vertical profiles of MMHgD concentrations accounted for two distinct maxima: one just below the oxycline and the other near the benthic interface. Direct wet atmospheric deposition accounted for 14 moles yr(-1) HgTUNF, with 0.7 moles yr(-1) as MMHgUNF, while circa 76 moles yr(-1) of HgTUNF, with 4.7 moles yr(-1) as MMHgUNF, coming from tributaries. Circa 78 moles (similar to 17% as MMHg) are annually exported through tile dam, while 23 moles yr(-1) of Hg-0 evolve in the atmosphere. A mass balance calculation suggests that the endogenic production of MMHgUNF attained 8.1 moles yr(-1), corresponding to a methylation rate of 0.06% d(-1). As a result, tile Petit-Saut reservoir is a large man-made reactor that has extensively altered mercury speciation in favor of methylated species. Applied Geochemistry (0883-2927) (Elsevier), 2008-05 , Vol. 23 , N. 5 , P. 1101-1126 Droits : 2008 Elsevier Ltd All rights reserved. http://archimer.ifremer.fr/doc/2008/publication-4198.pdf DOI:10.1016/j.apgeochem.2007.11.006 http://archimer.ifremer.fr/doc/00000/4198/ | Partager |
Variabilité des manifestations hydrothermales actuelles le long d'une dorsale ultra rapide. Dorsale Est Pacifique entre 17° et 19° S (campagne NAUDUR). Auteur(s) : Fouquet, Yves Auzende, Jean-marie Ballu, V Batiza, R Bideau, Daniel Cormier, Mh Geistdoerfer, P Lagabrielle, Yves Éditeur(s) : Gauthier-villars Résumé : 69 new hydrothermal sites were discovered during the Naudur diving cruise. Dives were conducted between 17 degrees 5 and 18 degrees 40'5 on four segments showing marked contrast in morphology, volcanic, tectonic and hydrothermal activity. At 17 degrees 10'5, 17 degrees 25'5 and 18 degrees 37'5 the ridge has a dome shaped cross-section and is dominated by very active volcanic activity. Early widespread low temperature (<50 degrees C) diffuse hydrothermal discharge is followed by focused high temperature black smokers. At 18 degrees 15'S tectonic activity is dominant, no recent lava was observed, and only two of the 20 hydrothermal sites are active. At 18 degrees 32'5 recent lava representing a new volcanic episode partly covers the bottom of the graben. Deep hydrothermal convection is reactivated with new black smokers along the graben wall. Also, there is low temperature shimmering water from cooling lava flows. These three segments can be considered as successive volcanic/tectonic episodes typical of a fast spreading ridge. Further, the observations support a new model for the temporal evolution of episodic hydrothermal activity. Hydrothermal convection is unstable and superficial during the volcanic stage (dykes injection). At the beginning of the teaonic stage (graben formation) faults allow deep circulation and hot fluid to reach the surface. As the graben widens hydrothermal activity is less important and may cease. The heat of a new volcanic episode reactivates the deep hot water circulation along the graben faults completing a cycle. 69 nouveaux sites hydrothermaux ont été découverts entre 17'5 et 18'40'5 sur quatre segments présentant des activités volcaniques et tectoniques contrastées. A 17°10'S,17025'S et 18'37'5, la ride forme un dôme et l'activité volcanique est dominante. Les émissions hydrothermales sont d'abord diffuses et de basse température, puis focalisées et de haute température. A 18°15'S la majorité des sites hydrothermaux sont inactifs dans un graben axial dépourvu de laves récentes. A 18'32'5, des laves récentes s'épanchent au fond du graben. Les circuits hydrothermaux réactivés par le nouvel épisode volcanique se traduisent par des diffusions sur les laves récentes et par une reprise des émissions de haute température le long des murs du graben. Ces quatre segments traduisent des épisodes volcanoltectoniques successifs, caractéristiques de I'évolution temporelle des dorsales rapides. Les observations permettent de proposer un nouveau modèle de l'activité hydrothermale. Les circuits hydrothermaux sont diffus, peu structurés, instables et superficiels durant les épisodes volcaniques. Au début des épisodes tectoniques, les failles du graben drainent les fluides chauds en profondeur, puis lorsque le graben s'élargit, l'activité s'interrompt. La reprise de l'activité volcanique réamorce les circulations profondes le long des failles du graben. Comptes Rendus de l'Academie des Sciences Serie II (1251-8069) (Gauthier-villars), 1994-12 , Vol. 319 , N. 11 , P. 1399-1406 Droits : Académie des Sciences http://archimer.ifremer.fr/doc/00183/29455/27889.pdf http://archimer.ifremer.fr/doc/00183/29455/ | Partager Voir aussi Hydrothermalisme Océan Dorsales rapides Min6ralisations sulfurées. HYDROTHERMAL ACTIVITY OCEAN FAST SPREADING RIDGES SULFIDES Télécharger |
Pour un suivi conjoncturel de l'environnement : à propos des ports du littoral français Auteur(s) : Ferlin, I Résumé : This study aims to integrate the problems associated with port development and related activities in an economic monitoring programme that surveys all the activities associated with the marine environment. The economic monitoring programme in this sector also includes studying coastal spatial planning. This type of study concerns the creation and remodelling of sites that involve investments. We can consider two types of coastal spatial planning: one which integrates port development, tourism, aquaculture and fisheries and one that deals with the marine environment (Abric, 1989). Economic surveys of port development on French coasts supposes that the problem of identifying information sources have been resolved and the sectors and the activities that should be accounted for have been characterised. In what follows, the limits of available information and the problems pertaining to the proposed classification of activities according to statistical nomenclature will be discussed. The absence of structured and localised data is aggravated in certain cases by the rules of confidentiality. In light of these difficulties, the first part of this report is devoted to the inventory of general information sources and to the characterisation of existing data. As information forms the basis of any economic monitoring programme, it is necessary to know where, how and by whom information is processed and the limits that one comes up against. This report does not pretend to be exhaustive given the deadlines and the duration of this study. The second part of this report constitutes a summary of the recent trends discerned in terms of port development, from a legal, as well as economic and financial, point of view. This study should be considered as the first step to establishing a basis for a more in-depth study. Cette étude a pour but d'intégrer les problèmes d'aménagement portuaire et les activités qui y sont liées dans un suivi conjoncturel de l'ensemble des activités économiques en relation avec le milieu maritime. Le suivi conjoncturel de ce secteur économique passe aussi par l'étude de l'aménagement physique du littoral. Celui-ci concerne la création et le remodelage de sites impliquant des investissements. On peut considérer deux types d'aménagements physiques -l'aménagement du littoral : portuaire, touristique, aquacole, halieutique; -l'aménagement du mineur marin (Abric, 1989). Un suivi conjoncturel de l'aménagement portuaire du littoral français, suppose en préalable la résolution du problème de l'identification des sources d'information et la caractérisation des secteurs et activités en prendre en compte. On verra par la suite les limites de l'information disponible et les problèmes afférents a la classification des activités selon les nomenclatures statistiques proposées. L'absence de données structurées et localisées est aggravée dans certains cas par des règles de confidentialité. Du fait de ces difficultés, la première partie de ce rapport est consacrée au recensement des sources d'information générale et à la caractérisation des données existantes. L'information étant à la base de tout suivi conjoncturel, il convient en effet d'être en mesure de savoir où, par qui et comment elle est traitée et les limites auxquelles on se heurte. Ce rapport ne peut prétendre à l'exhaustivité compte tenu des délais et de la période d'exécution de cette étude. La seconde partie constitue une première synthèse sur les évolutions récentes saisies en termes d'aménagements portuaires, tant d'un point de vue juridique qu'économique et financier. Cette étude est à considérer comme une première étape destinée à poser les bases pour une étude plus approfondie. [OCR NON CONTRÔLE] Droits : info:eu-repo/semantics/openAccess http://archimer.ifremer.fr/doc/1992/rapport-4169.pdf http://archimer.ifremer.fr/doc/00000/4169/ | Partager |
From the western boundary currents to the Pacific Equatorial Undercurrent: Modeled pathways and water mass evolutions Auteur(s) : Grenier, Melanie Cravatte, Sophie Blanke, Bruno Menkes, Christophe Koch-larrouy, Ariane Durand, Fabien Melet, Angelique Jeandel, Catherine Éditeur(s) : Amer Geophysical Union Résumé : The hydrological and geochemical properties of the waters constituting the Pacific Equatorial Undercurrent (EUC) determine the properties of the equatorial cold tongue. Understanding and quantifying the various EUC origins is therefore of prime importance. For this purpose, a high-resolution (1/4 degrees) interannual oceanic simulation was analyzed from the western tropical Pacific boundaries to 140 degrees W, using a Lagrangian framework. Waters from the Low-Latitude Western Boundary Currents (LLWBCs) transiting from Vitiaz Strait (the main contributor), from Solomon Strait, and via the Mindanao Current were identified as the principal sources to the EUC. Waters conveyed by the interior ocean off equator are negligible till 180 E. The LLWBCs' waters represent 87% of the EUC transport at 156 degrees E out of which the New Guinea Coastal Undercurrent (NGCU) is as large as 47%. The EUC meridional distribution suggests that the waters originating from Solomon Strait and Mindanao Current mostly remain in the hemisphere from which they originate. Contrastingly, Vitiaz Strait waters are found in both hemispheres. The vertical EUC distribution shows that the lower layer of the EUC is mainly composed of Vitiaz Strait waters. Finally, the source transport distributions were characterized, at their origin and within the EUC, as a function of density. These distributions showed that waters flowing through Vitiaz Strait at densities higher than those of the EUC (down to sigma(theta) = 27.2 kg m(-3)) undergo a diapycnal mixing and lighten during their journey to join the EUC. This lightening supports the suggestion that the NGCU is a major source for the EUC geochemical enrichment. Journal Of Geophysical Research-oceans (0148-0227) (Amer Geophysical Union), 2011-12 , Vol. 116 , N. C12044 , P. 16 p. Droits : 2011 by the American Geophysical Union http://archimer.ifremer.fr/doc/00060/17105/14621.pdf DOI:10.1029/2011JC007477 http://archimer.ifremer.fr/doc/00060/17105/ | Partager |
Environmental noise in spawning areas: the case of Atlantic bluefin tuna (Thunnus thynnus) Auteur(s) : Royer, Francois Fromentin, Jean-marc Éditeur(s) : Blackwell science Résumé : This paper provides an exploratory analysis aiming to seek whether the colour of environmental noise theory could help in understanding the intriguing reproductive strategy of Atlantic bluefin tuna (BFT). A frequency-based approach based on spectral exponents, f(beta) with beta < 0, is chosen and applied on 10 biogeographical provinces covering the North Atlantic. The major BFT spawning area, i.e. the Mediterranean Sea, was the only one to display a pink power spectrum, whereas open ocean regions displayed more reddened fluctuations, i.e. greater variance at low frequencies. Environmental noise in the Mediterranean could, thus, offer more favourable characteristics on the long-term than the open ocean. The implications of these findings are discussed in regards to medium and long (possibly evolutionary) time scales. Fisheries Oceanography (1054-6006) (Blackwell science), 2007-03 , Vol. 16 , N. 2 , P. 202-206 Droits : 2007 Blackwell science http://archimer.ifremer.fr/doc/2007/publication-2437.pdf DOI:10.1111/j.1365-2419.2006.00424.x http://archimer.ifremer.fr/doc/00000/2437/ | Partager |
Shewanella profunda sp nov., isolated from deep marine sediment of the Nankai Trough Auteur(s) : Toffin, Laurent Bidault, Adeline Pignet, Patricia Tindall, Brian Slobodkin, Alexander Kato, Chiaki Prieur, Daniel Éditeur(s) : Society for General Microbiology Résumé : A novel piezotolerant, mesophilic, facultatively anaerobic, organotrophic, polarly flagellated bacterium (strain LT13a(T)) was isolated from a deep sediment layer in the Nankai Trough (Leg 190, Ocean Drilling Program) off the coast of Japan. This organism used a wide range of organic substrates as sole carbon and energy sources: pyruvate, glutamate, succinate, fumarate, lactate, citrate, peptone and tryptone. Oxygen, nitrate, fumarate, ferric iron and cystine were used as electron acceptors. Maximal growth rates were observed at a hydrostatic pressure of 10 MPa. Hydrostatic pressure for growth was in the range 0.1-50 MPa. Predominant cellular fatty acids were 16:1 omega7c, 15: 0 iso, 16: 0 and 13: 0 iso. The G + C content of the DNA was 44.9 mol%. On the basis of 16S rRNA gene sequences, strain LT13a(T) was shown to belong to the gamma-Proteobacteria, being closely related to Shewanella putrefaciens (98%), Shewanella oneidensis (97%) and Shewanella baltica (96 %). Levels of DNA homology between strain LT13a(T) and S. putrefaciens, S. oneidensis and S. baltica were < 20 %, indicating that strain LT13a(T) represents a novel species. Genetic evidence and phenotypic characteristics showed that isolate LT13a(T) constitutes a novel species of the genus Shewanella, Because of the deep origin of the strain, the name Shewanella profunda sp. nov. is proposed, with LT13a(T) (= DSM 15900(T)-JCM 12080(T)) as the type strain. International journal of systematic and evolutionary microbiology (1466-5026) (Society for General Microbiology), 2004-11 , Vol. 54 , N. 6 , P. 1943-1949 Droits : 2004 International Union of Microbiological Societies http://archimer.ifremer.fr/doc/2004/publication-590.pdf DOI:10.1099/ijs.0.03007-0 http://archimer.ifremer.fr/doc/00000/590/ | Partager |
Isolation and partial characterization of bacteria (Pseudoalteromonas sp.) with potential antibacterial activity from a marine costal environment from New Caledonia Auteur(s) : Dufourcq, R. Chalkiadakis, Eletherios Fauchon, M. Deslandes, Eric Kerjean, V. Chanteau, S. Petit, Elodie Guezennec, Jean Éditeur(s) : Wiley-blackwell Résumé : Marine bacteria are a rich source of bioactive metabolites. However, the microbial diversity of marine ecosystem still needs to be explored. The aim of this study was to isolate and characterize bacteria with antimicrobial activities from various marine coastal environment of New Caledonia. We obtained 493 marine isolates from various environments and samples of which 63 (12.8%) presented an antibacterial activity against a panel of reference pathogenic strains (Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Enterococcus faecalis). Ten out of the most promising strains were cultured, fractionated and screened for antibacterial activity. Four of them (NC282, NC412, NC272 and NC120) showed at least an activity against reference and multidrug-resistant pathogenic strains and were found to belong to the genus Pseudoalteromonas, according to the 16S phylogenetic analysis. The NC282 strain does not belong to any described Pseudoalteromonas species and might be of interest for further chemical and biological characterization. These findings suggest that the identified strains may contribute to the discovery for new sources of antimicrobial substances to develop new therapies to treat infections caused by multidrug-resistant bacteria. Letters In Applied Microbiology (0266-8254) (Wiley-blackwell), 2014-02 , Vol. 58 , N. 2 , P. 102-108 Droits : 2013 The Society for Applied Microbiology http://archimer.ifremer.fr/doc/00174/28552/26994.pdf DOI:10.1111/lam.12162 http://archimer.ifremer.fr/doc/00174/28552/ | Partager |
Problématique de suivi de la pêche insulaire Auteur(s) : Reynal, Lionel Maguer, Cedric Taquet, Marc Éditeur(s) : University of Miami Résumé : Insular fisheries statistics are often insufficient to allow a good management of halieutics resources. The reasons of this insufficiency, in large part, is due to inadequate methods for recording catch data and analyzing fishing effort. This presentation proposes the use of a software pro gram (<< S.P.1. ») which helps to elaborate statistics from sampling, making easier the work of personnel who are charged with producing encoded informations on insular fisheries Les statistiques des pêches insulaires sont souvent insuffisantes pour permettre une bonne gestion des ressources halieutiques. Les causes de cette insuffisance qui porte essentiellement sur les données de prise et d'effort de pêche, sont analysées dans cette étude. Des propositions sont faites pour surmonter les difficultés rencontrées. Un logiciel '« S.P.1. ») d'aide à l'élaboration de statistiques par échantillonnage est proposé pour faciliter la tâche des personnels chargés de produire en routine des informations chiffrées sur les pêches insulaires Proceedings - Gulf and Caribbean Fisheries Institute, University of Miami (0072-9019) (University of Miami), 1998 , Vol. 50 , P. 1065-1074 Droits : info:eu-repo/semantics/openAccess http://archimer.ifremer.fr/doc/00113/22410/20107.pdf http://archimer.ifremer.fr/doc/00113/22410/ | Partager |
Probiotic effect of FLOC on Vibrios in the pacific white shrimp Litopenaeus Vannamei Auteur(s) : Aguilera-rivera, Diana Prieto-davo, Alejandra Escalante, Karla Chavez, Cristina Cuzon, Gerard Gaxiola, Gabriela Éditeur(s) : Elsevier Science Bv Résumé : The advantages of FLOC over clear water (CW) in rearing juvenile L. vannamei and its effects on Vibrio communities were evaluated. Survival rate in FLOC and clear water were recorded and a probiotic was tested under both conditions. Daily growth rate (DGR) was higher in FLOC (p < 0.05) than in CW. Survival in each system increased significantly when a probiotic was included in the diet (p < 0.05). The Vibrionaceae community from the hepatopancreas (HP) and the culture medium did not differ between the two culture media. Nevertheless, a novel group of Vibrio strains was found to be unique to FLOC. No high level of lesions was observed in shrimp tissues from the FLOC + probiotic treatment; it suggests that the probiotic contributed to homeostasis and prevented outbreak of opportunistic pathogenic species. Aquaculture (0044-8486) (Elsevier Science Bv), 2014-03 , Vol. 424 , P. 215-219 Droits : 2014 Elsevier B.V. All rights reserved. http://archimer.ifremer.fr/doc/00173/28379/26694.pdf DOI:10.1016/j.aquaculture.2014.01.008 http://archimer.ifremer.fr/doc/00173/28379/ | Partager |
Probiotic P-acidilactici application in shrimp Litopenaeus stylirostris culture subject to vibriosis in New Caledonia Auteur(s) : Castex, Mathieu Chim, Liet Pham, Dominique Lemaire, Pierrette Wabete, Nelly Nicolas, Jean-louis Schmidely, P Mariojouls, C Éditeur(s) : Elsevier Résumé : We studied the effects of a lactic acid bacterium, Pediococcus acidilactici (strain MA 18/5M, CNCM), as a dietary probiotic on growth performance and some nutritional and microbiological aspects of the shrimp Litopenaeus stylirostris. Experimental shrimp culture was carried out over 10 weeks, using floating cages of 14 m(2) each set in earthen ponds, in a New Caledonia farm affected by "Summer syndrome", a septicaemic vibriosis caused by Vibrio nigripulchritudo. The experiment design testing probiotic-coated pellets against control was replicated in two earthen ponds. High mortalities, characteristic of Summer syndrome, were observed during the first 2 weeks of the trial. The probiotic improved production in the treated cages from both ponds with increases in the survival rate (7% and 15% respectively) and final biomass (8% and 12% respectively). No differences were recorded among treatments on growth performances, but significant lower food conversion ratios were obtained with probiotic treatment. After 5 weeks of rearing, the Hepatosomatic Index and the adjusted dry weight of the digestive gland were significantly increased by 10% and by 9% respectively in shrimps treated with probiotic. In the meantime, the specific activities of alpha amylase and trypsin in the digestive gland showed a significant effect of the probiotic treatment with respective increases by 35% and 55%. The rise in total trypsin activity following morning feeding was also enhanced by the probiotic treatment (P < 0.001). The highest concentration of probiotic (between 10(4)-10(5) CFU g(-1) of fresh gut) in the shrimp gut was obtained 2 h after feeding. The concentration remained high for 4 h after feeding before decreasing until the next meal. Total bacterial counts on Marine agar and TCBS in the gut were significantly lowered by the probiotic treatment over the 10 weeks of the experiment. Additionally, during the first 2 weeks, prevalence and load of V nigripulchritudo strains in haemolymph was lower in animals fed with the probiotic diet. This study demonstrated, under pond conditions, that feeding shrimp with live terrestrial lactic acid bacteria can be an effective treatment for improving shrimp culture affected by vibriosis. (c) 2008 Elsevier B.V. All rights reserved. Aquaculture (0044-8486) (Elsevier), 2008-03 , Vol. 275 , N. 1-4 , P. 182-193 Droits : 2008 Elsevier B.V. All rights reserved. http://archimer.ifremer.fr/doc/2008/publication-4079.pdf DOI:10.1016/j.aquaculture.2008.01.011 http://archimer.ifremer.fr/doc/00000/4079/ | Partager |
Potential Effect of Freshwater Virus on the Structure and Activity of Bacterial Communities in the Marennes-Oléron Bay (France) Auteur(s) : Auguet, Jean-christophe Montanie, Helene Hartmann, Hans Lebaron, P. Casamayor, E. O. Catala, P. Delmas, Daniel Éditeur(s) : Springer Résumé : Batch culture experiments using viral enrichment were conducted to test the response of a coastal bacterial community to autochthonous (i.e., co-existing) or allochthonous riverine viruses. The effects of viral infections on bacterial dynamics and activity were assessed by epifluorescence microscopy and thymidine incorporation, respectively, whereas the effect of viral infection on bacterial community composition was examined by polymerase chain reaction-single strand conformation polymorphism 16S ribosomal RNA fingerprinting. The percentages of high nucleic acid-containing cells, evaluated by flow cytometry, were significantly correlated (r (2) = 0.91, n = 12, p < 0.0001) to bacterial production, making this value a good predictor of active cell dynamics along the study. While confinement and temperature were the two principal experimental factors affecting bacterial community composition and dynamics, respectively, additions of freshwater viruses had significant effects on coastal bacterial communities. Thus, foreign viruses significantly reduced net bacterial population increase as compared to the enrichment treated with inactivated virus. Moreover, freshwater viruses recurrently and specifically affected bacterial community composition, as compared to addition of autochthonous viruses. In most cases, the combined treatment viruses and freshwater dissolved organic matter helped to maintain or even enhance species richness in coastal bacterial communities in agreement to the 'killing the winner' hypothesis. Thus, riverine virus input could potentially influence bacterial community composition of the coastal bay albeit with modest modification of bulk bacterial growth. Microbial Ecology (0095-3628) (Springer), 2009-02 , Vol. 57 , N. 2 , P. 295-306 Droits : 2009 Springer http://archimer.ifremer.fr/doc/2009/publication-6636.pdf DOI:10.1007/s00248-008-9428-1 http://archimer.ifremer.fr/doc/00000/6636/ | Partager |
The duration of migration of Atlantic Anguilla larvae Auteur(s) : Bonhommeau, Sylvain Castonguay, Martin Rivot, Etienne Sabatie, Richard Le Pape, Olivier Éditeur(s) : Wiley-blackwell Publishing, Inc Résumé : Oceanic larvae of the European (Anguilla anguilla) and American (A. rostrata) eels have to cross the Atlantic Ocean from the Sargasso Sea to European or North American coasts before entering continental habitats. In some European rivers, eel recruitment is now < 1% of levels in the 1980s. A better understanding of the effects of anthropogenic pressures and environmental fluctuations on eel larvae and subsequent recruitment is a prerequisite to build efficient management plans. The present paper provides insight into the critical oceanic phase of the eel life cycle with a focus on the duration of the larval migration whose estimates varies between 7 months and more than 2 years in both species. Does this range correspond to a natural variability in larval duration or does it stem from methodological artefacts? We first review the different methods used to estimate the duration of larval migration and critically describe their possible sources of misinterpretation. We then evaluate the consistency of these methods with the current knowledge about the ecology and physiology of eel larvae and the physical oceanography. While a moderate discrepancy in migration duration was found between methods for the American eel, the discrepancy was large in the European eel. In this species, otolith microstructure studies indicated migration durations between 7 and 9 months, while other methods pointed to durations of about 2 years. We show that estimates in favour of a long migration duration seem more robust to methodological caveats than methods estimating short durations of migration. Fish And Fisheries (1467-2960) (Wiley-blackwell Publishing, Inc), 2010-09 , Vol. 11 , N. 3 , P. 289-306 Droits : 2010 Blackwell Publishing Ltd. http://archimer.ifremer.fr/doc/00011/12208/9033.pdf DOI:10.1111/j.1467-2979.2010.00362.x http://archimer.ifremer.fr/doc/00011/12208/ | Partager |
Comparison of spaceborne measurements of sea surface salinity and colored detrital matter in the Amazon plume Auteur(s) : Fournier, Severine Chapron, Bertrand Salisbury, J. Vandemark, Douglas Reul, Nicolas Éditeur(s) : Amer Geophysical Union Résumé : Large rivers are key hydrologic components in oceanography, particularly regarding air-sea and land-sea exchanges and biogeochemistry. We enter now in a new era of Sea Surface Salinity (SSS) observing system from Space with the recent launches of the ESA Soil Moisture and Ocean Salinity (SMOS) and the NASA Aquarius/Sac-D missions. With these new sensors, we are now in an excellent position to revisit SSS and ocean color investigations in the tropical northwest Atlantic using multi-year remote sensing time series and concurrent in situ observations. The Amazon is the world's largest river in terms of discharge. In its plume, SSS and upper water column optical properties such as the absorption coefficient of colored detrital matter (acdm) are strongly negatively correlated (<-0.7). Local quasi-linear relationships between SSS and acdm are derived for these plume waters over the period of 2010-2013 using new spaceborne SSS and ocean color measurements. Results allow unprecedented spatial and temporal resolution of this coupling. These relationships are then used to estimate SSS in the Amazon plume based on ocean color satellite data. This new product is validated against SMOS and in situ data and compared with previously developed SSS retrieval models. We demonstrate the potential to estimate tropical Atlantic SSS for the extended period from 1998 to 2010, prior to spaceborne SSS data collection. Journal Of Geophysical Research-oceans (0148-0227) (Amer Geophysical Union), 2015-05 , Vol. 120 , N. 5 , P. 3177-3192 Droits : 2015. American Geophysical Union. All Rights Reserved. http://archimer.ifremer.fr/doc/00255/36610/35742.pdf DOI:10.1002/2014JC010109 http://archimer.ifremer.fr/doc/00255/36610/ | Partager Voir aussi Amazon-Orinoco river plume SMOS SSS conservative mixing ocean color salinity satellite oceanography Télécharger |
L'arsenic en milieu marin. Biogeochimie et ecotoxicologie Auteur(s) : Michel, Pierre Résumé : Arsenic levels of in the marine environment are high in comparison with other contaminants. Over the past twenty years, a large number of arsenic organic compounds have been identified in the water, sediments and living species. This document constitutes a synthesis of current knowledge on arsenic sources, and contamination levels, on its biogeochemical cycle as well as its toxic effects on human and marine fauna. This paper highlights in particular the effects of phosynthesis on arsenic speciation and its distribution throughout the marine environment. Problems of toxicity in the case of certain phyto- and zooplankton species are identified. Bioaccumulation in seaweeds, molluscs and fishes is documented as well, with special attention to the species encountered in the French coastal waters. Les niveaux de présence de l'arsenic en milieu marin sont élevés comparativement à d'autres contaminants. Depuis une vingtaine d'années, de nombreux composés organiques de l'arsenic ont été identifiés dans l'eau, les sédiments et les espèces vivantes. Le présent document constitue une synthèse des connaissances sur les sources et les niveaux de contamination, le cycle biogéochimique, les effets toxiques pour l'homme et les espèces marines. L'accent est mis notamment sur les effets de la photosynthèse sur la spéciation de cet élément et sur sa distribution dans le milieu. Les problèmes de toxicité pour certaines espèces phyto- et zooplanctonniques sont identifiés. La bioaccumulation chez les algues, les mollusques et les poissons est bien documentée, avec une attention particulière pour les espèces présentes dans les eaux côtières françaises. Droits : info:eu-repo/semantics/openAccess http://archimer.ifremer.fr/doc/1993/rapport-1448.pdf http://archimer.ifremer.fr/doc/00000/1448/ | Partager Voir aussi Ecotoxicology Contamination Biogeochemistry Arsenic Ecotoxicologie Contamination Biogéochimie Arsenic Télécharger |
Post-glacial persistence of turbiditic activity within the Rhone deep-sea turbidite system (Gulf of Lions, Western Mediterranean): Linking the outer shelf and the basin sedimentary records Auteur(s) : Dennielou, Bernard Jallet, Laurent Sultan, Nabil Jouet, Gwenael Giresse, Pierre Voisset, Michel Berne, Serge Éditeur(s) : Elsevier Résumé : Emplacement of post-glacial turbidites is commonly controlled by rapid changes in sea level or by seismicity. On the continental rise of the Gulf of Lions (Western Mediterranean), an aseismic area, we identified turbiditic beds deposited during the rising stage and highstand of sea level. Swath bathymetry, sediment cores, in situ Cone Penetrating Tests (CPTU), heavy mineral associations and radiocarbon dating determined the source, composition, distribution and age of the turbiditic beds. Turbidites are composed of homogeneous to positively graded silts to medium sand with quartz (up to 90%), shell debris and shelfal benthic faunas. Their distribution on the sea floor is very patchy and controlled by abundant inherited erosional bedforms. Their source is found in relict regressive sands at the outershelf. Their deposition occurred just after the onset of the post-glacial sea level rise and the concomitant sediment starvation of the Rhone deep sea turbiditic system until recently. Whilst canyons are fed with sand by strong seasonal hydro-sedimentary dynamics on the outershelf, the emplacement of post-glacial turbidites is not controlled by sea level changes but probably by the periodic flushing of the canyons. Our study revealed that this low energy aseismic margin undergoes significant transport of sand, down to the base of slope, during the sea-level rise and the Holocene highstand. Marine Geology (0025-3227) (Elsevier), 2009-02 , Vol. 257 , N. 1-4 , P. 65-86 Droits : 2009 Published by Elsevier Ltd. http://archimer.ifremer.fr/doc/2009/publication-6316.pdf DOI:10.1016/j.margeo.2008.10.013 http://archimer.ifremer.fr/doc/00000/6316/ | Partager |
The major outer membrane protein OmpU of Vibrio splendidus contributes to host antimicrobial peptide resistance and is required for virulence in the oyster Crassostrea gigas Auteur(s) : Duperthuy, Marylise Binesse, Johan Le Roux, Frederique Romestand, Bernard Caro, Audrey Got, Patrice Givaudan, Alain Mazel, Didier Éditeur(s) : Wiley-blackwell Publishing, Inc Résumé : Vibrio splendidus, strain LGP32, is an oyster pathogen associated with the summer mortalities affecting the production of Crassostrea gigas oysters worldwide. Vibrio splendidus LGP32 was shown to resist to up to 10 mu M Cg-Def defensin and Cg-BPI bactericidal permeability increasing protein, two antimicrobial peptides/proteins (AMPs) involved in C. gigas immunity. The resistance to both oyster Cg-Def and Cg-BPI and standard AMPs (polymyxin B, protegrin, human BPI) was dependent on the ompU gene. Indeed, upon ompU inactivation, minimal bactericidal concentrations decreased by up to fourfold. AMP resistance was restored upon ectopic expression of ompU. The susceptibility of bacterial membranes to AMP-induced damages was independent of the ompU-mediated AMP resistance. Besides its role in AMP resistance, ompU proved to be essential for the adherence of V. splendidus LGP32 to fibronectin. Interestingly, in vivo, ompU was identified as a major determinant of V. spiendidus pathogenicity in oyster experimental infections. Indeed, the V. splendidus-induced oyster mortalities dropped from 56% to 11% upon ompU mutation (Kaplan Meier survival curves, P < 0.01). Moreover, in co-infection assays, the ompU mutant was out competed by the wild-type strain with competitive indexes in the range of 0.1-0.2. From this study, ompU is required for virulence of V. splendidus. Contributing to AMP resistance, conferring adhesive properties to V. splendidus, and being essential for in vivo fitness, the OmpU porin appears as an essential effector of the C. gigas/V. splendidus interaction. Environmental Microbiology (1462-2912) (Wiley-blackwell Publishing, Inc), 2010-04 , Vol. 12 , N. 4 , P. 951-963 Droits : 2010 Society for Applied Microbiology and Blackwell Publishing Ltd http://archimer.ifremer.fr/doc/00003/11421/8044.pdf DOI:10.1111/j.1462-2920.2009.02138.x http://archimer.ifremer.fr/doc/00003/11421/ | Partager |
Phosphorus forms related to sediment grain size and geochemical characteristics in French coastal areas Auteur(s) : Andrieux-loyer, Françoise Aminot, Alain Éditeur(s) : Elsevier Résumé : Phosphorus forms with respect to sediment characteristics, such as grain-size, and major chemical elements, were studied in French coastal marine areas (the Bay of Seine and the Loire and Gironde Estuaries).In the three areas, Fe/Al-bound phosphate (Fe/Al-P) and exchangeable phosphate (exch-P) were significantly related to the proportion of fine fraction (< 63 mum). The special association of these forms with fine particles, as well as the relationships between exch-P, Fe/Al-P and Fe showed that adsorption processes on Fe oxides had taken place. However, for similar Fe concentrations, Bay of Seine sediments showed Fe/Al-P concentrations which were four to five times higher than those found in the Loire and Gironde Estuaries. This was attributed to differences in sediment nature and processes in these two types of areas. Indeed, the Loire and Gironde Estuaries frequently show hypoxia.Calcium-bound phosphate (Ca-P) was found in all grain size classes with comparable concentrations in the Bay of Seine where there was no correlation between Ca-P and Ca. This corresponded to the calcium's marine origin (shells) in the Bay of Seine. In contrast, the correlation of Ca-P with Ca and the fine fraction of the sediment in the Loire and Gironde Estuaries was characteristic of the predominant metamorphic origin of Ca-P in these areas.Useful information for interpretation of P-forms can be obtained from major sediment characteristics. Thus, for areas where specific relationships have previously been established good estimates of P-forms could be predicted from sediment properties. Estuarine, Coastal and Shelf Science (0272-7714) (Elsevier), 2001-05 , Vol. 52 , N. 5 , P. 617-629 Droits : 2001 Academic Press. All rights reserved http://archimer.ifremer.fr/doc/2001/publication-469.pdf DOI:10.1006/ecss.2001.0766 http://archimer.ifremer.fr/doc/00000/469/ | Partager |
Reproductive performance, biochemical composition and fatty acid profile of wild-caught and 2nd generation domesticated Farfantepenaeus duorarum (Burkenroad, 1939) broodstock Auteur(s) : Emerenciano, Mauricio Cuzon, Gerard Mascaro, Maite Arevalo, Miguel Norena-barroso, Elsa Jeronimo, Gilberto Racotta, Ilie Gaxiola, Gabriela Éditeur(s) : Elsevier Science Bv Résumé : A 30-day trial was performed to evaluate the reproductive performance of wild and 2nd generation domesticated Farfantepenaeus duorarum broodstock. Changes in biochemical composition and fatty acids (FA) profile in the 1st and 4th spawn order females were used as indicators of nutritional condition. Wild population of F. duorarum presented significantly better reproductive outcomes as compared to domesticated ones. Wild spawners achieved significantly higher number of eggs per spawn, number of egg per spawn per g of spawner's body weight and number of nauplii per spawn (P<0.05). Latency period was significantly shorter (P<0.05) for wild than for domesticated females (11 vs 17 days). Wild spawners also presented less mortality (6 vs 12%), higher number of total spawns (51 vs 33), spawns per ablated and per spawning females as well as higher total eggs and nauplii production. On the other hand, domesticated females presented higher number of females that spawned at least once (89 vs 76%). The higher spawning activity was reflected in lower levels of acylglycerides (AG) and cholesterol content in wild hepatopancreas (HP) and ovary (OV) (P<0.05). FA profile, mainly represented by ARA, EPA and sum of n-3 were higher in hepatopancreas and ovary of wild females, however lower levels were detected in eggs as a result of a high spawning activity. Multivariate analysis performed to detected simultaneous variation in biochemical variables indicated AG as variation pattern's responsive. (c) 2012 Elsevier B.V. All rights reserved. Aquaculture (0044-8486) (Elsevier Science Bv), 2012-05 , Vol. 344 , P. 194-204 Droits : 2012 Elsevier B.V. All rights reserved. http://archimer.ifremer.fr/doc/00079/19042/17214.pdf DOI:10.1016/j.aquaculture.2012.03.014 http://archimer.ifremer.fr/doc/00079/19042/ | Partager |
First Evidence of Palytoxin and 42-Hydroxy-palytoxin in the Marine Cyanobacterium Trichodesmium Auteur(s) : Kerbrat, Anne Sophie Amzil, Zouher Pawlowiez, Ralph Golubic, Stjepko Sibat, Manoella Darius, Helene Taiana Chinain, Mireille Laurent, Dominique Éditeur(s) : Mdpi Ag Résumé : Marine pelagic diazotrophic cyanobacteria of the genus Trichodesmium (Oscillatoriales) are widespread throughout the tropics and subtropics, and are particularly common in the waters of New Caledonia. Blooms of Trichodesmium are suspected to be a potential source of toxins in the ciguatera food chain and were previously reported to contain several types of paralyzing toxins. The toxicity of water-soluble extracts of Trichodesmium spp. were analyzed by mouse bioassay and Neuroblastoma assay and their toxic compounds characterized using liquid chromatography coupled with tandem mass spectrometry techniques. Here, we report the first identification of palytoxin and one of its derivatives, 42-hydroxy-palytoxin, in field samples of Trichodesmium collected in the New Caledonian lagoon. The possible role played by Trichodesmium blooms in the development of clupeotoxism, this human intoxication following the ingestion of plankton-eating fish and classically associated with Ostreopsis blooms, is also discussed. Marine Drugs (1660-3397) (Mdpi Ag), 2011-04 , Vol. 9 , N. 4 , P. 543-560 Droits : 2011 MDPI Publishing http://archimer.ifremer.fr/doc/00040/15143/12576.pdf DOI:10.3390/md9040543 http://archimer.ifremer.fr/doc/00040/15143/ | Partager |