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Auteur (up) Annasawmy, P.; Ternon, J.-F.; Lebourges-Dhaussy, A.; Roudaut, G.; Cotel, P.; Herbette, S.; Menard, F.; Marsac, F.
Titre Micronekton distribution as influenced by mesoscale eddies, Madagascar shelf and shallow seamounts in the south-western Indian Ocean: an acoustic approach Type Article scientifique
Année 2020 Publication Revue Abrégée Deep-Sea Res. Part II-Top. Stud. Oceanogr.
Volume 176 Numéro Pages 104812
Mots-Clés biological production; circulation; community composition; deep-scattering layer; diel vertical migration; Diel vertical migration; dynamics; Madagascar shelf; mesopelagic fish; Mesoscale eddies; Micronekton; mozambique channel; Multi-frequency; myctophid fishes; Seamount; South-western indian ocean; zooplankton
Résumé An investigation of the vertical and horizontal distributions of micronekton, as influenced by mesoscale eddies, the Madagascar shelf and shallow seamounts, was undertaken using acoustic data collected during two research cruises at an unnamed pinnacle (summit depth similar to 240 m) thereafter named “MAD-Ridge”, and at La Perouse seamount (similar to 60 m) in the south-western Indian Ocean. MAD-Ridge is located to the south of Madagascar, in an “eddy corridor”, known both for its high mesoscale activity and high primary productivity. In contrast, La Perouse is located on the outskirts of the Indian South Subtropical Gyre (ISSG) province, characterised by low mesoscale activity and low primary productivity. During the MAD-Ridge cruise, a dipole was located in the vicinity of the seamount, with the anticyclone being almost stationary on the pinnacle. Total micronekton acoustic densities were greater at MAD-Ridge than at La Perouse. Micronekton acoustic densities of the total water column were lower within the anticyclone than within the cyclone during MAD-Ridge. Micronekton followed the usual diel vertical migration (DVM) pattern, except within the cyclone during MAD-Ridge where greater acoustic densities were recorded in the daytime surface layer. The backscatter intensities were stronger at the 38 kHz than at the 70 and 120 kHz frequencies in the daytime surface layer at MAD-Ridge cyclonic stations. These backscatter intensities likely correspond to gas-filled swimbladders of epi- and mesopelagic fish actively swimming and feeding within the cyclone or gelatinous organisms with gas inclusions. Our findings evidenced that the distributions of micronekton and DVM patterns are complex and are influenced significantly by physical processes within mesoscale eddies. The mesoscale eddies' effects were dominant over any potential seamount effects at the highly dynamic environment prevailing at MAD-Ridge during the cruise. No significant increase in total micronekton acoustic densities was observed over either seamount, but dense aggregations of biological scatterers were observed on their summits during both day and night.
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Langue English Langue du Résumé Titre Original
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Volume de collection Numéro de collection Edition
ISSN 0967-0645 ISBN Médium
Région Expédition Conférence
Notes WOS:000556810400001 Approuvé pas de
Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2836
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Auteur (up) Baselga, A.; Leprieur, F.
Titre Comparing methods to separate components of beta diversity Type Article scientifique
Année 2015 Publication Revue Abrégée Methods Ecol Evol
Volume 6 Numéro 9 Pages 1069-1079
Mots-Clés beta diversity; community composition; dissimilarity coefficients; nestedness; replacement; richness difference; turnover
Résumé * Two alternative frameworks have been proposed to partition compositional dissimilarity into replacement and nestedness-resultant component or into replacement and richness-difference components. These are, respectively, the BAS (Baselga 2010, Global Ecology and Biogeography, 19, 134–143) and POD (Podani & Schmera . Oikos, 120, 1625–1638) frameworks. * We conduct a systematic comparison of parallel components in alternative approaches. We test whether the replacement components derived from the BAS and POD frameworks are independent of richness difference. We also evaluate whether previously reported tests of monotonicity between indices and ecological processes are informative to assess the performance of indices. Finally, we illustrate the consequences of differences between the BAS and POD frameworks using the North American freshwater fish fauna as an empirical example. * In the BAS framework, the nestedness-resultant component (βjne or βsne) accounts only for richness differences derived from nested patterns while, in the POD framework, richness-difference dissimilarity (βrich or βrich.s) accounts for all kind of richness differences. Likewise, the replacement components of both alternative methods account for different concepts. Only the replacement component of the BAS framework (βjtu or βsim) is independent of richness difference, while the parallel component in the POD framework (β−3 or β−3.s) is not (i.e. it is mathematically constrained by richness difference). * Therefore, only the BAS framework allows separating (i) the variation in species composition derived from species replacement which is independent of richness difference (i.e. not mathematically constrained by it) and (ii) the variation in species composition derived from nested patterns.
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Volume de collection Numéro de collection Edition
ISSN 2041-210x ISBN Médium
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Numéro d'Appel MARBEC @ alain.herve @ collection 1473
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Auteur (up) Blanchet, M.; Pringault, O.; Panagiotopoulos, C.; Lefevre, D.; Charriere, B.; Ghiglione, J.-F.; Fernandez, C.; Aparicio, F.L.; Marrase, C.; Catala, P.; Oriol, L.; Caparros, J.; Joux, F.
Titre When riverine dissolved organic matter (DOM) meets labile DOM in coastal waters: changes in bacterial community activity and composition Type Article scientifique
Année 2017 Publication Revue Abrégée Aquat. Sci.
Volume 79 Numéro 1 Pages 27-43
Mots-Clés Bacterial community composition; bacterioplankton; biodegradation; carbon; coastal waters; Dissolved organic matter; Fluorescence; growth efficiency; lake water; marine; Mediterranean Sea; open-ocean; Priming effect; rhone river; terrestrial
Résumé Heterotrophic bacterial communities in marine environments are exposed to a heterogeneous mixture of dissolved organic compounds with different bioreactivity that may control both their activity and composition. The coastal environment is an example of a mixing area where recalcitrant allochthonous organic matter from rivers can encounter labile organic matter from marine phytoplanktonic blooms. The objective of this study was to explore the effects of mixed qualities of dissolved organic matter (DOM) on bacterial community activity (BCA) and bacterial community composition (BCC) and to test for a priming effect when DOM sources are added in combination. Coastal marine bacterial communities were incubated separately with a mixture of amino acids and with natural riverine DOM or with both sources together for 42 days. Addition of amino acids alone or in combination with riverine DOM led to a similar stimulation of BCA compared to control condition, whereas addition of riverine DOM alone did not modify BCA compared to the control. On the contrary, BCC analyzed by 16S rRNA gene pyrosequencing was not affected by the addition of amino acids alone, but changed dramatically with riverine DOM alone or in combination with amino acids. Our results show that changes in BCA and BCC can be driven by different types of DOM, but that these changes are not necessarily coupled. Moreover, the addition of labile DOM did not modify the microbial decomposition of riverine DOM, nor the BCC, suggesting that a priming effect did not occur under these experimental conditions.
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Langue English Langue du Résumé Titre Original
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Volume de collection Numéro de collection Edition
ISSN 1015-1621 ISBN Médium
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Numéro d'Appel MARBEC @ alain.herve @ collection 2090
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Auteur (up) 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 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.
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Langue English Langue du Résumé Titre Original
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Volume de collection Numéro de collection Edition
ISSN 0948-3055 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 546
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Auteur (up) Deininger, A.; Faithfull, C.L.; Lange, K.; Bayer, T.; Vidussi, F.; Liess, A.
Titre Simulated terrestrial runoff triggered a phytoplankton succession and changed seston stoichiometry in coastal lagoon mesocosms Type Article scientifique
Année 2016 Publication Revue Abrégée Mar. Environ. Res.
Volume 119 Numéro Pages 40-50
Mots-Clés climate change; communities; community composition; Diatoms; dynamics; ecosystems; events; food-web; growth; Mediterranean; Mesocosm; Phytoplankton; plankton; productivity; river flash-flood; schelde; soil; Stoichiometry; Thau lagoon
Résumé Climate change scenarios predict intensified terrestrial storm runoff, providing coastal ecosystems with large nutrient pulses and increased turbidity, with unknown consequences for the phytoplankton community. We conducted a 12-day mesocosm experiment in the Mediterranean Thau Lagoon (France), adding soil (simulated runoff) and fish (different food webs) in a 2 x 2 full factorial design and monitored phytoplankton composition, shade adaptation and stoichiometry. Diatoms (Chaetoceros) increased fourfold immediately after soil addition, prymnesiophytes and dinoflagellates peaked after six- and 12 days, respectively. Soil induced no phytoplanlcton shade adaptation. Fish reduced the positive soil effect on dinoflagellates (Scripsiella, Glenodinium), and diatom abundance in general. Phytoplankton community composition drove seston stoichiometry. In conclusion, pulsed terrestrial runoff can cause rapid, low quality (high carbon: nutrient) diatom blooms. However, bloom duration may be short and reduced in magnitude by fish. Thus, climate change may shift shallow coastal ecosystems towards famine or feast dynamics. (C) 2016 Elsevier Ltd. All rights reserved.
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Langue English Langue du Résumé Titre Original
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Volume de collection Numéro de collection Edition
ISSN 0141-1136 ISBN Médium
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Numéro d'Appel MARBEC @ alain.herve @ collection 2063
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