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Auteur (up) Krichen, E.; Harmand, T.; Torrijos, M.; Godon, J.J.; Bernet, N.; Rapaport, A.
Titre High biomass density promotes density-dependent microbial growth rate Type Article scientifique
Année 2018 Publication Revue Abrégée Biochem. Eng. J.
Volume 130 Numéro Pages 66-75
Mots-Clés culture; ecology; model; systems; Density-dependent growth rate; Flocculation; influent substrate concentration; kinetics; Mass balance models; Microbial ecosystem; Microbial ecosystem structure
Résumé Describing the interactions between a population and its resources is a research topic in both microbiology and population ecology. When there are fewer resources for the individuals in a large population, the overcrowding can lead to a density-dependent effect which is reflected by a negative feedback of the organism density on the consumption process. In this paper, we investigate the growth rate of an aerobic microbial ecosystem by two series of experiments performed in continuous agitated cultures. Using a constant dilution rate, but different input substrate concentrations in each experiment, the biomass and substrate concentration were measured at steady state to confront their values with those obtained theoretically from the well-known mathematical model of the chemostat using either resource or density-dependent kinetics. The structures of both flocs and microbial communities were monitored in order to interpret the results. The experiments confirm that density-dependent growth-rate can result either from a high concentration of biomass or from the structuration of this biomass into flocs and we have shown that a new parametrized family of growth functions, that we proposed in this paper, suits better the experimental data than Monod or Contois growth functions. (C) 2017 Elsevier B.V. All rights reserved.
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ISSN 1369-703x ISBN Médium
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Auteur (up) Navarro, J.; Saez-Liante, R.; Albo-Puigserver, M.; Coll, M.; Palomera, I.
Titre Feeding strategies and ecological roles of three predatory pelagic fish in the western Mediterranean Sea Type Article scientifique
Année 2017 Publication Revue Abrégée Deep-Sea Res. Part II-Top. Stud. Oceanogr.
Volume 140 Numéro Pages 9-17
Mots-Clés diet; ecosystem structure; iberian peninsula; indian-ocean; isotope ratios; Marine predators; Pelagic ecosystem; Stable isotopes; stable-isotopes; Stomach contents; swordfish; top predators; Trophic ecology; trophic level; xiphias-gladius; Yellowfin tuna
Résumé Knowing the feeding ecology of marine predators is pivotal to developing an understanding of their ecological role in the ecosystem and determining the trophic relationships between them. Despite the ecological importance of predatory pelagic fish species, research on these species in the Mediterranean Sea is limited. Here, by combining analyses of stomach contents and stable isotope values, we examined the feeding strategies of swordfish, Xiphias gladius, little tunny, Euthynnus alletteratus and Atlantic bonito, Sarda sarda, in the western Mediterranean Sea. We also compared the trophic niche and trophic level of these species with published information of other sympatric pelagic predators present in the ecosystem. Results indicated that, although the diet of the three species was composed mainly by fin-fish species, a clear segregation in their main feeding strategies was found. Swordfish showed a generalist diet including demersal species such as blue whiting, Micromesistius poutassou, and European hake, Merluccius merluccius, and pelagic fin-fish such as barracudina species (Arctozenus risso and Lestidiops jayakari) or small pelagic fish species. Little tunny and Atlantic bonito were segregated isotopically between them and showed a diet basically composed of anchovy, Engraulis encrasicolus, and round sardinella, Sardinella aurita, and sardines, Sardina pilchardus, respectively. This trophic segregation, in addition to potential segregation by depth, is likely a mechanism that allows their potential coexistence within the same pelagic habitat. When the trophic position of these three predatory pelagic fish species is compared with other pelagic predators such as bluefin tuna, Thunnus thynnus, and dolphinfish, Coryphaena hippurus, present in the western Mediterranean Sea, we found that they show similar intermediate trophic position in the ecosystem. In conclusion, the combined stomach and isotopic results highlight, especially for little tunny and Atlantic bonito, the trophic importance of Clupeoid species in their diet. In addition, the importance of demersal resources for swordfish provides evidence for the pelagic-demersal coupling of the ecosystem and the need to manage marine resources in an integrated way. (C) 2016 Elsevier Ltd. All rights reserved.
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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 0967-0645 ISBN Médium
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Numéro d'Appel MARBEC @ alain.herve @ collection 2175
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