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Auteur (up) BAUER, R.; Graewe, U.; Stepputtis, D.; Zimmermann, C.; Hammer, C. url  openurl
  Titre Identifying the location and importance of spawning sites of Western Baltic herring using a particle backtracking model Type Article scientifique
  Année 2014 Publication Revue Abrégée Ices Journal Of Marine Science  
  Volume 71 Numéro 3 Pages 499-509  
  Mots-Clés backtracking; Baltic Sea; Clupea harengus; hatching sites; lagoon; larval transport; spring spawning  
  Résumé The recruitment success of some herring stocks fluctuates strongly, and apparently, success is often already determined during the early life stages, i.e. before metamorphosis. In studying the survival of early life stages and its affecting factors, particularly those during the egg stage, it is crucial to examine the processes at the spawning sites, which often cannot be explored directly. A recent decline in the recruitment of Western Baltic spring-spawning herring (WBSSH) increases the urgency of filling the knowledge gap for this stock, especially because one bottleneck in the recruitment seems to occur before hatching. We examined the successful 20032009 spawning sites of WBSSH in the main spawning ground, the Greifswalder Bodden lagoon. Instead of using common techniques such as diving or underwater videography, which are usually unsuitable for mapping large areas, we applied a model approach. We tracked herring larvae at length 610 mm, recorded by larval surveys during MarchJune of the respective years, back to their hatching sites using a Lagrangian particle backtracking model. We compared the spawning areas identified by the model with the results of earlier field studies; however, we also analysed variations between years, larval length groups, and different applied growth models, which are needed to define hatch-dates. Although spawning sites could not be identified with high precision because of the strong diffusion in the area studied, results indicate that larvae up to 10 mm length are caught near their hatching sites. However, the location of successful spawning sites varied largely between years, with the main hatching sites situated in the Strelasund and the eastern entrance of the lagoon. This may reflect variations in spawning-site selection or quality. A better knowledge of the locations and relative importance of, and the processes occurring on, the different spawning sites will provide an important contribution to the sustainable management of this commercially valuable herring stock.  
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  ISSN 1054-3139 ISBN Médium  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1136  
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Auteur (up) Bauer, R.K.; Stepputtis, D.; Gräwe, U.; Zimmermann, C.; Hammer, C. url  doi
openurl 
  Titre Wind-induced variability in coastal larval retention areas: a case study on Western Baltic spring-spawning herring Type Article scientifique
  Année 2013 Publication Revue Abrégée Fisheries Oceanography  
  Volume Numéro Pages  
  Mots-Clés atmospheric forcing; Baltic Sea; biophysical modelling; Greifswalder Bodden; herring; larval retention; recruitment; spring spawners  
  Résumé The investigation of larval dispersal and retention, their variability and dependence on wind conditions, has become a major topic in fisheries research owing to potential effects on stock recruitment and stock structuring. The present study quantifies the wind-induced variability of larval retention of herring in a highly productive coastal lagoon of the Western Baltic Sea. This lagoon, the Greifswalder Bodden, represents the main spawning area of Western Baltic Spring-Spawning Herring, a stock that has recently undergone a continuous decline in recruitment. The study tests whether this decline was related to changes in larval retention, more precisely to changes in wind conditions, the main forcing of the lagoon's circulation. To answer this, a model approach was applied. Larvae were tracked as Lagrangian drifters under constant and variable wind conditions, examining the main drift patterns and reconstructing the incidents during the period of recruitment decline. For the latter, weekly cohorts of virtual larvae were released in the lagoon over the entire spawning period (April–June; \textgreater16 weeks). The fraction of retained larvae per cohort was related to observed larval abundances. On this basis, a new retention index was defined to evaluate the annual larval retention. The results presented cannot explain the observed recruitment decline but characterize the lagoon as an important larval retention area by virtue of unsteady wind conditions that prevent a steady outflow of larvae.  
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  ISSN 1365-2419 ISBN Médium  
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  Numéro d'Appel LL @ pixluser @ collection 255  
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Auteur (up) Duval, C.; Thomazeau, S.; Drelin, Y.; Yepremian, C.; Bouvy, M.; Couloux, A.; Troussellier, M.; Rousseau, F.; Bernard, C. doi  openurl
  Titre Phylogeny and salt-tolerance of freshwater Nostocales strains: Contribution to their systematics and evolution Type Article scientifique
  Année 2018 Publication Revue Abrégée Harmful Algae  
  Volume 73 Numéro Pages 58-71  
  Mots-Clés baltic sea; bloom; comb. nova; Cyanobacteria; dolichospermum; genera anabaena; genetics analysis; great oxidation event; hetR; Morphology; nijH; Nostocaceae; Phylogeny; Physiology; planktonic cyanobacteria; polyphasic approach; Polyphasic approach; Salt-tolerance; toxin production  
  Résumé Phylogenetic relationships among heterocytous genera (the Nostocales order) have been profoundly modified since the use of polyphasic approaches that include molecular data. There is nonetheless still ample scope for improving phylogenetic delineations of genera with broad ecological distributions, particularly by integrating specimens from specific or up-to-now poorly sampled habitats. In this context, we studied 36 new isolates belonging to Chrysosporum, Dolichospermum, Anabaena, Anabaenopsis, and Cylindrospermopsis from freshwater ecosystems of Burkina-Faso, Senegal, and Mayotte Island. Studying strains from these habitats is of particular interest as we suspected different range of salt variations during underwent periods of drought in small ponds and lakes. Such salt variation may cause different adaptation to salinity. We then undertook a polyphasic approach, combining molecular phylogenies, morphological analyses, and physiological measurements of tolerance to salinity. Molecular phylogenies of 117 Nostocales sequences showed that the 36 studied strains were distributed in seven lineages: Dolichospermum, Chrysosporum, Cylindrospermopsis Raphidiopsis, Anabaenopsis, Anabaena sphaerica var tenuis/Sphaerospermopsis, and two independent Anabaena sphaerica lineages. Physiological data were congruent with molecular results supporting the separation into seven lineages. In an evolutionary context, salinity tolerance can be used as an integrative marker to reinforce the delineation of some cyanobacterial lineages. The history of this physiological trait contributes to a better understanding of processes leading to the divergence of cyanobacteria. In this study, most of the cyanobacterial strains isolated from freshwater environments were salt-tolerant, thus suggesting this trait constituted an ancestral trait of the heterocytous cyanobacteria and that it was probably lost two times secondarily and independently in the ancestor of Dolichospermum and of Cylindrospermopsis. (C) 2018 Elsevier B.V. All rights reserved.  
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  ISSN 1568-9883 ISBN Médium  
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  Numéro d'Appel MARBEC @ alain.herve @ collection 2341  
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Auteur (up) Pringault, O.; Viret, H.; Duran, R. url  doi
openurl 
  Titre Interactions between Zn and bacteria in marine tropical coastal sediments Type Article scientifique
  Année 2012 Publication Revue Abrégée Environ. Sci. Pollut. Res.  
  Volume 19 Numéro 3 Pages 879-892  
  Mots-Clés Bacterial diversity; Metal spiking; Microcosms; New Caledonia; T-Rflp; baltic sea sediments; community; coral-reef lagoon; fragment-length-polymorphism; heavy-metals; hypersaline microbial mat; new-caledonia lagoon; polluted anoxic sediments; salins-de-giraud; south-west lagoon; tolerance pict  
  Résumé Purpose The main goals of this study were (1) to examine the effects of zinc on the microbial community structure of anthropogenically impacted sediments in a tropical coastal ecosystem and (2) to determine whether these microbial benthic communities may enhance the adsorption of zinc. Methods The interactions between zinc and bacteria in tropical sediments were studied in sediment microcosms amended with 2.5 mg L-1 of Zn in the water phase and incubated for 8 days under different environmental conditions, oxic/anoxic and glucose addition. At the end of incubation, microbial structure was assessed by molecular fingerprints (T-RFLP) analysis and Zn speciation in the sediment was determined by sequential extraction. Results In the three studied sediments, Zn spiking resulted in only slight changes in bacterial community structure. In contrast, the addition of low concentrations of glucose (5mM) strongly modified the bacterial community structure: <20% of similarity with the initial structure concomitant with a strong diminution of the specific richness. Overall, these results suggest that highly labile organic matter has a larger impact on microbial structure than heavy metal. These weak impacts of Zn on bacteria diversity might be partly explained by (1) the strong adsorption of Zn in the presence of bacteria and/or (2) the incorporation of Zn into a nonbioavailable fraction. Nevertheless, Zn spiking resulted in significant changes in nutrient cycles, suggesting that bacterial metabolisms were impacted by the heavy metal. This led to an increase in nutrient supplies to the water column, potentially enhancing eutrophication in a nutrient-limited, oligotrophic ecosystem.  
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  Volume de collection Numéro de collection Edition  
  ISSN 0944-1344 ISBN Médium  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 683  
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Auteur (up) Ramirez-Romero, E.; Molinero, J.C.; Paulsen, M.; Javidpour, J.; Clemmesen, C.; Sommer, U. doi  openurl
  Titre Quantifying top-down control and ecological traits of the scyphozoan Aurelia aurita through a dynamic plankton model Type Article scientifique
  Année 2018 Publication Revue Abrégée J. Plankton Res.  
  Volume 40 Numéro 6 Pages 678-692  
  Mots-Clés 2 hydromedusae; annual cycle; baltic sea; coastal ecosystem; common jellyfish; ctenophore mnemiopsis-leidyi; jellyfish; kiel-bight; planktonic food web; population modeling; population-dynamics; predation impact; sarsia-tubulosa; stage-resolved model; zooplankton  
  Résumé Aurelia aurita (Linneaus, 1758) is a cosmopolitan scyphozoan, probably the most investigated jellyfish in temperate and highly productive coastal ecosystems. Despite a prominent top-down control in plankton food webs, a mechanistic understanding of A. aurita population dynamics and trophic interactions has been barely addressed. Here we develop a food web dynamic model to assess A. aurita role in the seasonal plankton dynamics of the Kiel Fjord, southwestern Baltic Sea. The model couples low trophic level dynamics, based on a classical Nutrient Phytoplankton Zooplankton Detritus (NPZD) model, to a stage-resolved copepod model (referencing Pseudocalanus sp.) and a jellyfish model (A. aurita ephyra and medusa) as consumers and predators, respectively. Simulations showed the relevance of high abundances of A. aurita, which appear related with warm winter temperatures, promoting a shift from a copepod-dominated food web to a ciliate and medusa dominated one. The model captured the intraspecific competition triggered by the medusae abundance and characterized by a negative relationship between population density and individual size/weight. Our results provide a mechanistic understanding of an emergent trait such as size shaping the food web functioning, driving predation rates and population dynamics of A. aurita, driving its sexual reproductive strategy at the end of the pelagic phase.  
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  ISSN 0142-7873 ISBN Médium  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2476  
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