bascule de visibilité Search & Display Options

Tout Sélectionner    Désélectionner
 |   | 
Détails
   print
  Enregistrements Liens
Auteur Ben Gharbia, H.; Yahia, O.K.-D.; Cecchi, P.; Masseret, E.; Amzil, Z.; Herve, F.; Rovillon, G.; Nouri, H.; M’Rabet, C.; Couet, D.; Triki, H.Z.; Laabir, M. url  doi
openurl 
  Titre New insights on the species-specific allelopathic interactions between macrophytes and marine HAB dinoflagellates Type Article scientifique
  Année 2017 Publication Revue Abrégée Plos One  
  Volume 12 Numéro 11 Pages e0187963  
  Mots-Clés Dinoflagellates; Lagoons; Leaves; marine ecosystems; Phenols; Photosynthesis; Phytoplankton; Toxins  
  Résumé Macrophytes are known to release allelochemicals that have the ability to inhibit the proliferation of their competitors. Here, we investigated the effects of the fresh leaves of two magnoliophytes (Zostera noltei and Cymodocea nodosa) and thalli of the macroalgae Ulva rigida on three HAB-forming benthic dinoflagellates (Ostreopsis cf. ovata, Prorocentrum lima, and Coolia monotis). The effects of C. nodosa and U. rigida were also tested against the neurotoxic planktonic dinoflagellate Alexandrium pacificum Litaker sp. nov (former Alexandrium catenella). Co-culture experiments were conducted under controlled laboratory conditions and potential allelopathic effects of the macrophytes on the growth, photosynthesis and toxin production of the targeted dinoflagellates were evaluated. Results showed that U. rigida had the strongest algicidal effect and that the planktonic A. pacificum was the most vulnerable species. Benthic dinoflagellates seemed more tolerant to potential allelochemicals produced by macrophytes. Depending on the dinoflagellate/macrophyte pairs and the weight of leaves/thalli tested, the studied physiological processes were moderately to heavily altered. Our results suggest that the allelopathic activity of the macrophytes could influence the development of HAB species.  
  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 1932-6203 ISBN Médium  
  Région Expédition Conférence  
  Notes Approuvé pas de  
  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2242  
Lien permanent pour cet enregistrement
 

 
Auteur Bourgeois, S.; Hochard, S.; Pringault, O. url  doi
openurl 
  Titre Subtidal microphytobenthos: effects of inorganic and organic compound supplies on migration, production, and respiration in a tropical coastal environment Type Article scientifique
  Année 2010 Publication Revue Abrégée Aquat. Microb. Ecol.  
  Volume 61 Numéro 1 Pages 13-29  
  Mots-Clés Amino acids; Autotroph-heterotroph coupling; Glucose; Nutrients; Oxygen; Reflectance; availability; benthic diatoms; chlorophyll-a fluorescence; coral-reef lagoon; headwater streams; hypersaline microbial mat; lagoon; marine; microelectrode; new-caledonia; nutrient; oxygenic photosynthesis; phytoplankton  
  Résumé Microphytobenthos (MPB) is an important primary producer in coastal ecosystems. In oligotrophic environments, its activity may be controlled by the availability of organic or inorganic compounds but also by its migration behavior. The objective of this study was to determine, in MPB-colonized subtidal sediments, the consequences of short-term enrichments (< 24 h) of organic (alanine, glutamate, and glucose) and inorganic (ammonium, phosphate) compounds on MPB vertical migration and metabolisms, net production (NP), areal gross production (AGP), and community respiration (R). Two contrasting stations located in the southwest lagoon of New Caledonia were investigated: 1 under strong anthropogenic influence and 1 under more oceanic influence. Both stations were dominated by epipelic diatoms. Differences in net primary production were explained by diurnal variation of MPB biomass at the sediment surface, showing the importance of MPB migration in the functioning of these subtidal environments. However, a stimulation or inhibition of MPB migration did not necessarily impact the net primary production of the system; this strongly depends upon the interactions between the autotrophic and heterotrophic compartments, the latter being controlled by the environmental conditions. For the station under low anthropogenic influence, AGP and R were both significantly stimulated by alanine, glucose, and ammonium, and significantly inhibited by phosphate. The similar responses of AGP and R to enrichments suggest that autotrophs and heterotrophs were tightly coupled. Conversely, in the station under strong anthropogenic influence, AGP and R responded differently. Addition of ammonium inhibited AGP without having an impact on R, whereas addition of phosphate inhibited R whilst having no measurable effect on AGP. In this station, the coupling between autotrophs and heterotrophs was weakened, suggesting that the carbon demand of the heterotrophic compartment is probably sustained by the supplies of allochthonous organic matter rather than by exudates from the autotrophic compartment.  
  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 886  
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 Hickman-Lewis, K.; Gautret, P.; Arbaret, L.; Sorieul, S.; De Wit, R.; Foucher, F.; Cavalazzi, B.; Westall, F. url  doi
openurl 
  Titre Mechanistic morphogenesis of organo-sedimentary structures growing under geochemically stressed conditions: Keystone to proving the biogenicity of some archaean stromatolites? Type Article scientifique
  Année 2019 Publication Revue Abrégée Geosciences  
  Volume 9 Numéro 8 Pages 359  
  Mots-Clés anoxygenic photosynthesis; Archaean; Dresser Formation; early life; microbial mat; Middle Marker horizon; stromatolite; X-ray micro-scale computed tomography  
  Résumé Morphologically diverse organo-sedimentary structures (including microbial mats and stromatolites) provide a palaeobiological record through more than three billion years of Earth history. Since understanding much of the Archaean fossil record is contingent upon proving the biogenicity of such structures, mechanistic interpretations of well-preserved fossil microbialites can reinforce our understanding of their biogeochemistry and distinguish unambiguous biological characteristics in these structures, which represent some of the earliest records of life. Mechanistic morphogenetic understanding relies upon the analysis of geomicrobiological experiments. Herein, we report morphological-biogeochemical comparisons between micromorphologies observed in growth experiments using photosynthetic mats built by the cyanobacterium Coleofasciculus chthonoplastes (formerly Microcoleus) and green anoxygenic phototrophic Chloroflexus spp. (i.e., Coleofasciculus–Chloroflexus mats), and Precambrian organo-sedimentary structures, demonstrating parallels between them. In elevated ambient concentrations of Cu (toxic to Coleofasciculus), Coleofasciculus–Chloroflexus mats respond by forming centimetre-scale pinnacle-like structures (supra-lamina complexities) associated with large quantities of EPS at their surfaces. µPIXE mapping shows that Cu and other metals become concentrated within surficial sheath-EPS-Chloroflexus-rich layers, producing density-differential micromorphologies with distinct fabric orientations that are detectable using X-ray computed micro-tomography (X-ray µCT). Similar micromorphologies are also detectable in stromatolites from the 3.481 Ga Dresser Formation (Pilbara, Western Australia). The cause and response link between the presence of toxic elements (geochemical stress) and the development of multi-layered topographical complexities in organo-sedimentary structures may thus be considered an indicator of biogenicity, being an indisputably biological and predictable morphogenetic response reflecting, in this case, the differential responses of Coleofasciculus and Chloroflexus to Cu. Growth models for microbialite morphogenesis rely upon linking morphology to intrinsic (biological) and extrinsic (environmental) influences. Since the pinnacles of Coleofasciculus–Chloroflexus mats have an unambiguously biological origin linked to extrinsic geochemistry, we suggest that similar micromorphologies observed in ancient organo-sedimentary structures are indicative of biogenesis. An identical Coleofasciculus–Chloroflexus community subjected to salinity stress also produced supra-lamina complexities (tufts) but did not produce identifiable micromorphologies in three dimensions since salinity seems not to negatively impact either organism, and therefore cannot be used as a morphogenetic tool for the interpretation of density-homogeneous micro-tufted mats—for example, those of the 3.472 Ga Middle Marker horizon. Thus, although correlative microscopy is the keystone to confirming the biogenicity of certain Precambrian stromatolites, it remains crucial to separately interrogate each putative trace of ancient life, ideally using three-dimensional analyses, to determine, where possible, palaeoenvironmental influences on morphologies. Widespread volcanism and hydrothermal effusion into the early oceans likely concentrated toxic elements in early biomes. Morphological diversity in fossil microbialites could, therefore, reflect either (or both of) differential exposure to ambient fluids enriched in toxic elements and/or changing ecosystem structure and tolerance to elements through evolutionary time—for example, after incorporation into enzymes. Proof of biogenicity by deducing morphogenesis (i.e., a process preserved in the fossil record) overcomes many of the shortcomings inherent to the proof of biogenicity by descriptions of morphology alone.  
  Adresse  
  Auteur institutionnel Thèse  
  Editeur Lieu de Publication Éditeur  
  Langue en 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 WOS:000482981000025 Approuvé pas de  
  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2601  
Lien permanent pour cet enregistrement
Tout Sélectionner    Désélectionner
 |   | 
Détails
   print

Save Citations:
Export Records: