|   | 
Détails
   web
Enregistrements
Auteur Auguet, J.C.; Montanie, H.; Delmas, D.; Hartmann, H.J.; Huet, V.
Titre Dynamic of virioplankton abundance and its environmental control in the Charente estuary (France) Type Article scientifique
Année (up) 2005 Publication Revue Abrégée Microb Ecol
Volume 50 Numéro 3 Pages 337-349
Mots-Clés Bacteria/isolation & purification Ecosystem *Environment; Controlled France Plankton/*isolation & purification Rivers/chemistry/*microbiology Seasons Viruses/*isolation & purification Water Microbiology
Résumé The Charente River provides nutrient- and virus-rich freshwater input to the Marennes Oleron Basin, the largest oyster-producing region in Europe. To evaluate virioplankton distribution in the Charente Estuary and identify which environmental variables control dynamic of virioplankton abundance, five stations defined by a salinity gradient (0-0.5, 0.6-5, 13-17, 20-24, and higher than 30 PSU) were surveyed over a year. Viral abundance was related to bacterioplankton abundance and activities, photosynthetic pigments, nutrient concentration, and physical parameters (temperature and salinity). On a spatial scale, virus displayed a decreasing pattern seaward with abundance ranging over the sampling period from 1.4x10(7) to 20.8x10(7) viruses mL-1 making virioplankton the most abundant component of planktonic microorganisms in the Charente Estuary. A good correlation was found between viral and bacterial abundance (rs=0.85). Furthermore, bacterial abundance was the most important predictor of viral abundance explaining alone between 66% (winter) and 76% (summer) of viral variability. However, no relation existed between viral abundance and chlorophyll a. Temporal variations in viral distributions were mainly controlled by temperature through the control of bacterial dynamics. Spatial variations of viral abundance were influenced by hydrodynamic conditions especially during the winter season where virioplankton distribution was entirely driven by mixing processes.
Adresse
Auteur institutionnel Thèse
Editeur Lieu de Publication Éditeur
Langue Langue du Résumé Titre Original
Éditeur de collection Titre de collection Titre de collection Abrégé
Volume de collection Numéro de collection Edition
ISSN ISBN Médium
Région Expédition Conférence
Notes Approuvé pas de
Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1296
Lien permanent pour cet enregistrement
 

 
Auteur Auguet, J.C.; Montanie, H.; Lebaron, P.
Titre Structure of virioplankton in the Charente Estuary (France): transmission electron microscopy versus pulsed field gel electrophoresis Type Article scientifique
Année (up) 2006 Publication Revue Abrégée Microb Ecol
Volume 51 Numéro 2 Pages 197-208
Mots-Clés Capsid/chemistry *Electrophoresis; Electron Plankton Rivers/*virology Seasons Seawater/*microbiology/*virology Viruses/genetics/*isolation & purification/ultrastructure *Water Microbiology; Gel; Pulsed-Field Environmental Monitoring/methods France Genome; Viral/genetics *Microscopy
Résumé Changes in the composition of viral communities were investigated along a salinity gradient and at different times by means of transmission electron microscopy (TEM) and pulsed field gel electrophoresis (PFGE). Samples were collected in fresh (Charente River), estuarine (Charente Estuary), and coastal (Pertuis d'Antioche, French Atlantic coast) waters. Both methods revealed similar patterns in viral community structure with a dominance of small viral particles (capsid and genome size). Viruses with a head size below 65 nm made up 71 +/- 5% of total virus-like particles, and virus-like genomes (VLG) below 100 kb accounted for 89 +/- 9% of total VLG. Despite this apparent stability of virioplankton composition over spatial scale (salinity gradient), the occurrence of large viruses (capsid and genome size) in estuarine and seawater samples indicated the presence of viral populations specific to a geographical location. Temporal changes in the structure (capsid and genome size) of viral communities were more pronounced than those reported at the spatial scale. From January to May 2003, seasonal changes in viral abundance and bacterial production occurred concomitantly with an increase in viral genomic diversity (richness), suggesting that virioplankton composition was strongly linked to changes in microbial activity and/or in the structure of the host communities. Although PFGE and TEM yielded complementary results in the description of virioplankton structures, it seems that the use of PFGE alone should be enough for the monitoring of community changes.
Adresse
Auteur institutionnel Thèse
Editeur Lieu de Publication Éditeur
Langue Langue du Résumé Titre Original
Éditeur de collection Titre de collection Titre de collection Abrégé
Volume de collection Numéro de collection Edition
ISSN ISBN Médium
Région Expédition Conférence
Notes Approuvé pas de
Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1297
Lien permanent pour cet enregistrement
 

 
Auteur Bonilla-Findji, O.; Rochelle-Newall, E.; Weinbauer, M.G.; Pizay, M.D.; Kerros, M.E.; Gattuso, J.P.
Titre Effect of seawater-freshwater cross-transplantations on viral dynamics and bacterial diversity and production Type Article scientifique
Année (up) 2009 Publication Revue Abrégée Aquat. Microb. Ecol.
Volume 54 Numéro 1 Pages 1-11
Mots-Clés aquatic systems; Bacterial production; Bacterial richness; bacterioplankton; batch cultures; chesapeake bay; Communities; community composition; dissolved organic-matter; estuarine salinity gradient; growth efficiency; marine; microbial; population-dynamics; Transplantation; Virus
Résumé Dilution experiments were carried out to investigate the community composition and the metabolic response of seawater and freshwater bacteria to cross-transplantation, and the effects of nor.-indigenous bacterial hosts on viral dynamics. Changes in viral and bacterial abundance and production, as Well as bacterial respiration, carbon demand and diversity were regularly monitored over a 6 d period. Bacterial production in the transplanted seawater (SB-t) and freshwater (FB-t) bacteria treatments was stimulated up to 256 and 221 %, respectively, compared to controls. The stimulation of bacterial production and carbon demand was accompanied by a decrease in bacterial richness. Net viral production was stimulated by 81% in SB-t and repressed by 75% in FB-t. Transplantation increased the virus-induced mortality of marine bacteria, but decreased it for freshwater bacteria. These results suggest that (1) marine bacteria can readily oxidize freshwater dissolved organic matter, and (2) freshwater viruses might be able to infect marine hosts, thus highlighting their potential role in fueling bacterial growth under resource stress or nutrient-depleted conditions.
Adresse
Auteur institutionnel Thèse
Editeur Lieu de Publication Éditeur
Langue English Langue du Résumé Titre Original
Éditeur de collection Titre de collection Titre de collection Abrégé
Volume de collection Numéro de collection Edition
ISSN 0948-3055 ISBN Médium
Région Expédition Conférence
Notes Approuvé pas de
Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 546
Lien permanent pour cet enregistrement
 

 
Auteur Machu, E.; Ettahiri, O.; Kifani, S.; Benazzouz, A.; Makaoui, A.; Demarcq, H.
Titre Environmental control of the recruitment of sardines (Sardina pilchardus) over the western Saharan shelf between 1995 and 2002 : a coupled physical/biogeochemical modelling experiment Type Article scientifique
Année (up) 2009 Publication Revue Abrégée Fisheries Oceanography
Volume 18 Numéro 5 Pages 287-300
Mots-Clés biomass; Canary upwelling; hydrodynamic and biogeochemical modelling; plankton; potential spawning habitat; recruitment; Sardina pilchardus
Résumé Fisheries constitute an important economic sector for Morocco, where the species Sardina pilchardus represents the main landings. In acoustic evaluations conducted along the Moroccan coast since 1995, the absence of juveniles in 1996 and 1998 and the collapse of the sardine stock between 1996 and 1997 represent the main events until 2002. Sardines are known to be microphageous planktivores and thus are sensitive to environmental variability. A biogeochemical model coupled to a hydrodynamic model (ROMS) was run over the Canary Current System (1991-2002) to investigate the environmental factors that could have played a role in the variability of the sardine spawning. A grid refinement (1/12 degrees) centred on the Saharan Bank (SB) region was built to study the main spawning ground of sardines off northwest Africa. The volume of the potential spawning habitat (PSH) of sardines was defined as a function of depth, temperature and salinity, which are included in the ranges 0-200 m, 15-21 degrees C and 35.8-36.8, respectively. Our modelling frame was able to reproduce the seasonal cycle of temperature, phytoplankton concentration and PSH over the SB. It also captured the warming associated with the negative index of the North Atlantic Oscillation of 1995-1997 and allowed a description of the inter-annual variability of the PSH. Our experiment shows that the volume of PSH was much reduced in 1996 compared to the other years. The results suggest that the delay between high abundance of plankton and favourable spawning conditions is a good proxy for determining the recruitment failure of sardine in this oceanic region.
Adresse
Auteur institutionnel Thèse
Editeur Lieu de Publication Éditeur
Langue Langue du Résumé Titre Original
Éditeur de collection Titre de collection Titre de collection Abrégé
Volume de collection Numéro de collection Edition
ISSN 1054-6006 ISBN Médium
Région Expédition Conférence
Notes Approuvé pas de
Numéro d'Appel LL @ pixluser @ collection 43
Lien permanent pour cet enregistrement
 

 
Auteur Pringault, O.; Tesson, S.; Rochelle-Newall, E.
Titre Respiration in the Light and Bacterio-Phytoplankton Coupling in a Coastal Environment Type Article scientifique
Année (up) 2009 Publication Revue Abrégée Microb. Ecol.
Volume 57 Numéro 2 Pages 321-334
Mots-Clés bacteria; dissolved organic-carbon; enhanced dark; growth efficiency; heterotrophic; marine bacterioplankton; nw mediterranean sea; post-illumination respiration; respiration; salt-marsh estuaries; solar; ultraviolet-radiation; uv-radiation
Résumé In pelagic ecosystems, the principal source of organic matter is via autotrophic production and the primary sink is through heterotrophic respiration. One would therefore anticipate that there is some degree of linkage between these two compartments. Recent work has shown that respiration in the light is higher than dark respiration. Consequently, many of the methods used to determine respiration and production are biased as they require the assumption that light and dark respiration rates are equivalent. We show here that, in a coastal ecosystem, under visible light exposure, respiration in the light is related to gross production. More than 60% of the variation of respiration in the light, measured at 1 to 40 A mu g L(-1) of chlorophyll a (Chla), could be explained by the variations of gross production. Secondly, the relative contribution of bacterial respiration to community respiration in the light represented up to 79% at low Chla (1 A mu g L(-1)) and was negatively correlated with Chla concentration. Although bacterial production and bacterial respiration were both enhanced in the light, bacterial respiration in the light was more stimulated than bacterial production, which resulted in a decrease in bacterial growth efficiency during light exposure. These results show that the impact of light on the functioning of the microbial loop needs to be taken into account for a better understanding of the oceanic carbon cycle.
Adresse
Auteur institutionnel Thèse
Editeur Lieu de Publication Éditeur
Langue English Langue du Résumé Titre Original
Éditeur de collection Titre de collection Titre de collection Abrégé
Volume de collection Numéro de collection Edition
ISSN 0095-3628 ISBN Médium
Région Expédition Conférence
Notes Approuvé pas de
Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 826
Lien permanent pour cet enregistrement