bascule de visibilité Search & Display Options

Tout Sélectionner    Désélectionner
 |   | 
Détails
   print
  Enregistrements Liens
Auteur Brauer, V.S.; Stomp, M.; Rosso, C.; van Beusekom, S.A.M.; Emmerich, B.; Stal, L.J.; Huisman, J. url  doi
openurl 
  Titre Low temperature delays timing and enhances the cost of nitrogen fixation in the unicellular cyanobacterium Cyanothece Type Article scientifique
  Année 2013 Publication Revue Abrégée The ISME journal  
  Volume 7 Numéro 11 Pages 2105-2115  
  Mots-Clés climate change; day-night cycle; nitrogen fixation; nitrogenase; respiration; unicellular cyanobacteria  
  Résumé Marine nitrogen-fixing cyanobacteria are largely confined to the tropical and subtropical ocean. It has been argued that their global biogeographical distribution reflects the physiologically feasible temperature range at which they can perform nitrogen fixation. In this study we refine this line of argumentation for the globally important group of unicellular diazotrophic cyanobacteria, and pose the following two hypotheses: (i) nitrogen fixation is limited by nitrogenase activity at low temperature and by oxygen diffusion at high temperature, which is manifested by a shift from strong to weak temperature dependence of nitrogenase activity, and (ii) high respiration rates are required to maintain very low levels of oxygen for nitrogenase, which results in enhanced respiratory cost per molecule of fixed nitrogen at low temperature. We tested these hypotheses in laboratory experiments with the unicellular cyanobacterium Cyanothece sp. BG043511. In line with the first hypothesis, the specific growth rate increased strongly with temperature from 18 to 30 degrees C, but leveled off at higher temperature under nitrogen-fixing conditions. As predicted by the second hypothesis, the respiratory cost of nitrogen fixation and also the cellular C:N ratio rose sharply at temperatures below 21 degrees C. In addition, we found that low temperature caused a strong delay in the onset of the nocturnal nitrogenase activity, which shortened the remaining nighttime available for nitrogen fixation. Together, these results point at a lower temperature limit for unicellular nitrogen-fixing cyanobacteria, which offers an explanation for their (sub)tropical distribution and suggests expansion of their biogeographical range by global warming.  
  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 1751-7370 ISBN Médium  
  Région Expédition Conférence  
  Notes Approuvé pas de  
  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 696  
Lien permanent pour cet enregistrement
 

 
Auteur Clavier, J.; Chauvaud, L.; Carlier, A.; Amice, E.; van der Geest, M.; Labrosse, P.; Diagne, A.; Hily, C. url  openurl
  Titre Aerial and underwater carbon metabolism of a Zostera noltii seagrass bed in the Banc d'Arguin, Mauritania Type Article scientifique
  Année 2011 Publication Revue Abrégée Aquatic Botany  
  Volume 95 Numéro Pages 24-30  
  Mots-Clés Zostera noltii Seagrass Metabolism Intertidal Respiration Primary production Africa Isotope wadden sea marine angiosperms seasonal-variation coastal lagoon hornem photosynthesis oxygen respiration dynamics dioxide  
  Résumé Community respiration and primary production were measured in a dense intertidal Zostera noltii bed on the Banc d'Arguin, Mauritania (West Africa) under aerial and submerged conditions. Metabolism was studied in situ in dark and transparent benthic chambers. CO(2) fluxes in the air were measured over a series of short-term incubations (3 min) using an infrared gas analyzer. Dissolved inorganic carbon fluxes were calculated from concentration changes during one-hour underwater incubations. Air and underwater irradiance levels were measured every minute throughout the experiments. Carbon respiration was lower in the air (2.2 mmol m(-2) h(-1)) than underwater (5.0 mmol m(-2) h(-1)); similarly, a production-irradiance model fitted to the data indicated that gross maximal photosynthetic rate was markedly lower during emergence (6.0 mmol C m(-2) h(-1)) than under water (42.7 mmol C m(-2) h(-1)). The delta(13)C values observed in shoots indicated a decrease in atmospheric CO(2) contribution, compared to dissolved inorganic carbon, in Z. noltii metabolism along a depth gradient within a single location. As the seagrass bed remains under a thin layer of water at low tide at the studied site, the large difference in primary production can be mainly attributed to photosynthesis inhibition by high pH and oxygen concentration, as well as to the negative feedback of self-shading by seagrass leaves during emersion. The observed differences in respiration can be explained by the oxygen deficit at night during low tide near the sediment surface, a deficit that is consistent with the abundance of anoxia-tolerant species. (C) 2011 Elsevier B.V. All rights reserved.  
  Adresse [Clavier, Jacques] IUEM, CNRS, UMR 6539, LEMAR,Lab Sci Environm Marin, F-29280 Plouzane, France. [Van der Geest, Matthijs] NIOZ, Dept Marine Ecol, NL-1790 AB Den Burg, Netherlands. [Labrosse, Pierre; Diagne, Ahmed] IMROP, Nouadhibou, Mauritania. Clavier, J (reprint author), IUEM, CNRS, UMR 6539, LEMAR,Lab Sci Environm Marin, Pl Nicolas Copernic, F-29280 Plouzane, France. Jacques.Clavier@univ-brest.fr  
  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 0304-3770 ISBN Médium  
  Région Expédition Conférence  
  Notes ISI Document Delivery No.: 781BF Times Cited: 2 Cited Reference Count: 72 Clavier, Jacques Chauvaud, Laurent Carlier, Antoine Amice, Erwan Van der Geest, Matthijs Labrosse, Pierre Diagne, Ahmed Hily, Christian Franco-Mauritanian PACOBA project; Oceanographic and Fisheries Research Mauritanian Institute (IMROP); Banc d'Arguin National Park (PNBA) This study was funded by the Franco-Mauritanian PACOBA project. We thank the Oceanographic and Fisheries Research Mauritanian Institute (IMROP) and the Banc d'Arguin National Park (PNBA) for their support. Elsevier science bv Amsterdam Approuvé pas de  
  Numéro d'Appel MARBEC @ alain.herve @ 847 collection 1369  
Lien permanent pour cet enregistrement
 

 
Auteur Galasso, H.L.; Richard, M.; Lefebvre, S.; Aliaume, C.; Callier, M.D. doi  openurl
  Titre Body size and temperature effects on standard metabolic rate for determining metabolic scope for activity of the polychaete Hediste (Nereis) diversicolor Type Article scientifique
  Année 2018 Publication Revue Abrégée PeerJ  
  Volume 6 Numéro Pages e5675  
  Mots-Clés adaptation; Aerobic scope; Allometric coefficient; annelida; Annelida; Arrhenius temperature; Deposit-feeder; growth; Growth; muller; nereididae; Oxygen consumption; oxygen-uptake; populations; respiration; salinity; ventilation  
  Résumé Considering the ecological importance and potential value of Hediste diversicolor, a better understanding of its metabolic rate and potential growth rates is required. The aims of this study are: (i) to describe key biometric relationships; (ii) to test the effects of temperature and body size on standard metabolic rate (as measure by oxygen consumption) to determine critical parameters, namely Arrhenius temperature (T-A), allometric coefficient (b) and reaction rate; and (iii) to determine the metabolic scope for activity (MSA) of H. diversicolor for further comparison with published specific growth rates. Individuals were collected in a Mediterranean lagoon (France). After 10 days of acclimatization, 7 days at a fixed temperature and 24 h of fasting, resting oxygen consumption rates (VO2) were individually measured in the dark at four different temperatures (11, 17, 22 and 27 degrees C) in worms weighing from 4 to 94 mgDW (n = 27 per temperature). Results showed that DW and L3 were the most accurate measurements of weight and length, respectively, among all the metrics tested. Conversion of WW (mg), DW (mg) and L3 (mm) were quantified with the following equations: DW = 0.15 x WW, L3 = 0.025 x TL(mm) + 1.44 and DW = 0.8 x L3(3.68). Using an equation based on temperature and allometric effects, the allometric coefficient (b) was estimated at 0.8 for DW and at 2.83 for L3. The reaction rate (VO2) equaled to 12.33 mu mol gDW(-1) h(-1) and 0.05 mu mol mm L3(-1) h(-)(1) at the reference temperature (20 degrees C, 293.15 K). Arrhenius temperature (T-A) was 5,707 and 5,664 K (for DW and L3, respectively). Metabolic scope for activity ranged from 120.1 to 627.6 J gDW(-1) d(-1). Predicted maximum growth rate increased with temperature, with expected values of 7-10% in the range of 15-20 degrees C. MSA was then used to evaluate specific growth rates (SGR) in several experiments. This paper may be used as a reference and could have interesting applications in the fields of aquaculture, ecology and biogeochemical processes.  
  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 2167-8359 ISBN Médium  
  Région Expédition Conférence  
  Notes Approuvé pas de  
  Numéro d'Appel MARBEC @ alain.herve @ collection 2443  
Lien permanent pour cet enregistrement
 

 
Auteur Lefevre, S.; Domenici, P.; McKenzie, D.J. url  doi
openurl 
  Titre Swimming in air-breathing fishes Type Article scientifique
  Année 2014 Publication Revue Abrégée Journal of Fish Biology  
  Volume 84 Numéro 3 Pages 661-681  
  Mots-Clés acid-base; aerobic metabolism; amia-calva; bimodal respiration; dicentrarchus-labrax; european sea-bass; exercise; exhaustive exercise; gar lepisosteus-platyrhincus; megalops-cyprinoides; pacific; partitioning; rainbow-trout; recovery; respiratory; tarpon; trout oncorhynchus-mykiss  
  Résumé Fishes with bimodal respiration differ in the extent of their reliance on air breathing to support aerobic metabolism, which is reflected in their lifestyles and ecologies. Many freshwater species undertake seasonal and reproductive migrations that presumably involve sustained aerobic exercise. In the six species studied to date, aerobic exercise in swim flumes stimulated air-breathing behaviour, and there is evidence that surfacing frequency and oxygen uptake from air show an exponential increase with increasing swimming speed. In some species, this was associated with an increase in the proportion of aerobic metabolism met by aerial respiration, while in others the proportion remained relatively constant. The ecological significance of anaerobic swimming activities, such as sprinting and fast-start manoeuvres during predator-prey interactions, has been little studied in air-breathing fishes. Some species practise air breathing during recovery itself, while others prefer to increase aquatic respiration, possibly to promote branchial ion exchange to restore acid-base balance, and to remain quiescent and avoid being visible to predators. Overall, the diversity of air-breathing fishes is reflected in their swimming physiology as well, and further research is needed to increase the understanding of the differences and the mechanisms through which air breathing is controlled and used during exercise.  
  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 0022-1112 ISBN Médium  
  Région Expédition Conférence  
  Notes Approuvé pas de  
  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 877  
Lien permanent pour cet enregistrement
 

 
Auteur Lefevre, S.; Mckenzie, D.J.; Nilsson, G.E. doi  openurl
  Titre Models projecting the fate of fish populations under climate change need to be based on valid physiological mechanisms Type Article scientifique
  Année 2017 Publication Revue Abrégée Glob. Change Biol.  
  Volume 23 Numéro 9 Pages 3449-3459  
  Mots-Clés aerobic scope; coryphaena-hippurus; energy-demand teleosts; gadus-morhua l; gill surface area; growth; makaira-nigricans; marlin tetrapturus-albidus; metabolism; metabolism-size relationship; oxygen consumption; oxygen-consumption; ram ventilation; Respiration; scaling; swimming performance; tuna katsuwonus-pelamis  
  Résumé Some recent modelling papers projecting smaller fish sizes and catches in a warmer future are based on erroneous assumptions regarding (i) the scaling of gills with body mass and (ii) the energetic cost of 'maintenance'. Assumption (i) posits that insurmountable geometric constraints prevent respiratory surface areas from growing as fast as body volume. It is argued that these constraints explain allometric scaling of energy metabolism, whereby larger fishes have relatively lower mass-specific metabolic rates. Assumption (ii) concludes that when fishes reach a certain size, basal oxygen demands will not be met, because of assumption (i). We here demonstrate unequivocally, by applying accepted physiological principles with reference to the existing literature, that these assumptions are not valid. Gills are folded surfaces, where the scaling of surface area to volume is not constrained by spherical geometry. The gill surface area can, in fact, increase linearly in proportion to gill volume and body mass. We cite the large body of evidence demonstrating that respiratory surface areas in fishes reflect metabolic needs, not vice versa, which explains the large interspecific variation in scaling of gill surface areas. Finally, we point out that future studies basing their predictions on models should incorporate factors for scaling of metabolic rate and for temperature effects on metabolism, which agree with measured values, and should account for interspecific variation in scaling and temperature effects. It is possible that some fishes will become smaller in the future, but to make reliable predictions the underlying mechanisms need to be identified and sought elsewhere than in geometric constraints on gill surface area. Furthermore, to ensure that useful information is conveyed to the public and policymakers about the possible effects of climate change, it is necessary to improve communication and congruity between fish physiologists and fisheries scientists.  
  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 1354-1013 ISBN Médium  
  Région Expédition Conférence  
  Notes Approuvé pas de  
  Numéro d'Appel MARBEC @ alain.herve @ collection 2169  
Lien permanent pour cet enregistrement
Tout Sélectionner    Désélectionner
 |   | 
Détails
   print

Save Citations:
Export Records: