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Author: Vincent Rossi
Publisher:
ISBN:
Category :
Languages : en
Pages : 277
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Book Description
The objectives were numerous but centered on a scientific overarching question: the influence of mesoscale physical processes on planktonic ecosystems in coastal upwellings. The use of several and complementary tools was necessary to assess the various mechanisms occurring at these scales. First, the variability of the physical and biogeochemical properties of the Iberian Peninsula Upwelling System was studied using in-situ data from the MOUTON 2007 survey. The coastal domain was divided into different biogeochemical provinces: high nutrient concentrations are found in the northern part due to upwelled waters of subpolar origin whereas the southern area was characterized by moderate nutrient concentrations (waters of subtropical origin). The intense cross-shore gradient revealed that the biological activity is associated with the successive upwelling pulses. Data from a filament allowed us to assess its impact in terms of cross-shore exchanges of biological material. Then, a secondary upwelling front located at the shelf break was observed in these data. We built a simplified 2D numerical model to explain it by the eastward advection from upwelling currents of deep water columns onto the shelf. It creates a negative anomaly of Potential Vorticity (PV) which generates the secondary front. A simulation revealed a filamentation process that was further investigated numerically. The interaction between the alongshore upwelling current and a promontory creates anomalies of PV in the lower layer that generates the development of a filament trapped in the vicinity of the promontory. Finally, we used satellite data associated with a lagrangian tool (Finite-Size Lyapunov Exponent) to study the horizontal mixing in relation to the biological activity over the four eastern boundary upwelling zones. We showed a negative relationship between horizontal surface mixing and chlorophyll content, which seems related to a diminution of vertical velocities of the coastal upwelling, as well as a lateral loss of nutrient due to moving eddies. Horizontal mixing induced by eddies thus has an inhibiting effect on the phytoplankton in coastal upwellings, whereas a positive effect stands for the open ocean. Using diverse and complementary tools allowed us to improve our knowledge of the large influence of physical processes on marine ecosystems.
Author: Vincent Rossi
Publisher:
ISBN:
Category :
Languages : en
Pages : 277
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Book Description
The objectives were numerous but centered on a scientific overarching question: the influence of mesoscale physical processes on planktonic ecosystems in coastal upwellings. The use of several and complementary tools was necessary to assess the various mechanisms occurring at these scales. First, the variability of the physical and biogeochemical properties of the Iberian Peninsula Upwelling System was studied using in-situ data from the MOUTON 2007 survey. The coastal domain was divided into different biogeochemical provinces: high nutrient concentrations are found in the northern part due to upwelled waters of subpolar origin whereas the southern area was characterized by moderate nutrient concentrations (waters of subtropical origin). The intense cross-shore gradient revealed that the biological activity is associated with the successive upwelling pulses. Data from a filament allowed us to assess its impact in terms of cross-shore exchanges of biological material. Then, a secondary upwelling front located at the shelf break was observed in these data. We built a simplified 2D numerical model to explain it by the eastward advection from upwelling currents of deep water columns onto the shelf. It creates a negative anomaly of Potential Vorticity (PV) which generates the secondary front. A simulation revealed a filamentation process that was further investigated numerically. The interaction between the alongshore upwelling current and a promontory creates anomalies of PV in the lower layer that generates the development of a filament trapped in the vicinity of the promontory. Finally, we used satellite data associated with a lagrangian tool (Finite-Size Lyapunov Exponent) to study the horizontal mixing in relation to the biological activity over the four eastern boundary upwelling zones. We showed a negative relationship between horizontal surface mixing and chlorophyll content, which seems related to a diminution of vertical velocities of the coastal upwelling, as well as a lateral loss of nutrient due to moving eddies. Horizontal mixing induced by eddies thus has an inhibiting effect on the phytoplankton in coastal upwellings, whereas a positive effect stands for the open ocean. Using diverse and complementary tools allowed us to improve our knowledge of the large influence of physical processes on marine ecosystems.
Author: Marine Herrmann
Publisher:
ISBN:
Category :
Languages : fr
Pages : 308
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Book Description
Notre objectif est de contribuer à la compréhension du fonctionnement du système Méditerranéen grâce à la modélisation. Nous nous intéressons d'abord à la formation et au devenir des masses d'eau en Méditerranée nord-occidentale. L'influence de la résolution spatiale du modèle océanique est examinée lors de l'étude de la convection profonde au large pour une année réelle. Le rôle essentiel joué par les structures de méso-échelle dans la formation et le devenir de l'eau profonde est mis en évidence. La comparaison de simulations effectuées avec différents forçages atmosphériques permet de montrer l'influence de la résolution spatiale de ce forçage sur la modélisation de la convection, liée à l'importance des extrêmes atmosphériques. Puis nous examinons l'impact de la variabilité interannuelle atmosphérique et du changement climatique sur la formation d'eau dense sur le plateau du Golfe du Lion. Les volumes d'eau dense formée, exportée, et cascadant sont corrélés à la perte de chaleur atmosphérique hivernale. L'intensification de la stratification de la colonne d'eau d'ici la fin du XXIème siècle provoque une quasi-disparition du cascading. L'influence des processus physiques sur l'écosystème planctonique pélagique est examinée au moyen d'un modèle couplé hydrodynamique-biogéochimie...
Author: Coralie Perruche
Publisher:
ISBN:
Category :
Languages : fr
Pages : 170
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Book Description
L’océan est un milieu fortement turbulent caractérisé par des structures tourbillonnaires très énergétiques interagissant entre elles. Dans les couches de surface, les observations et les modèles montrent que cette dynamique méso- et subméso-échelle combinée à la dynamique de la couche mélangée, contraint fortement la distribution des espèces phytoplanctoniques. L’objet de cette thèse est de réaliser une étude de processus en modélisation numérique afin de rationaliser l’effet de la turbulence méso- et subméso-échelle d’une part et du melange vertical d’autre part, sur la diversité phytoplanctonique. L’étude de la dynamique intrinsèque d’un modèle d’écosystème avec deux phytoplanctons à l’aide de la théorie des systèmes dynamiques a tout d’abord permis de déterminer les équilibres non-linéaires ainsi que leur stabilité en fonction des paramètres. Nous avons montré ensuite que la diffusion verticale turbulente est un moteur de la coexistence phytoplanctonique. La sensibilité de ces résultats a étè testée à la fois vis à vis de la profondeur de la couche mélangée, de l’intensité du mélange et du nombre d’espèces. Enfin, nous avons montré que la turbulence quasi-géostrophique de surface permet la coexistence de deux phytoplanctons sur une ressource limitante à l’équilibre statistique. Ce type de turbulence organise différemment les espèces selon les structures les structures filamentaires sont favorables au grand phytoplancton alors que les tourbillons apparaissent comme des niches écologiques pour le petit phytoplancton. Cette étude révèle que les injections verticales de nutriments sont un facteur important induisant cette différence de distribution entre les espèces.
Author:
Publisher: International Publishers Service, Incorporated
ISBN:
Category : Science
Languages : en
Pages : 234
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Author: Collectif
Publisher: IRD Éditions
ISBN: 2709922207
Category : Nature
Languages : en
Pages : 736
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Book Description
This book has been published by Allenvi (French National Alliance for Environmental Research) to coincide with the 22nd Conference of Parties to the United Nations Framework Convention on Climate Change (COP22) in Marrakesh. It is the outcome of work by academic researchers on both sides of the Mediterranean and provides a remarkable scientific review of the mechanisms of climate change and its impacts on the environment, the economy, health and Mediterranean societies. It will also be valuable in developing responses that draw on “scientific evidence” to address the issues of adaptation, resource conservation, solutions and risk prevention. Reflecting the full complexity of the Mediterranean environment, the book is a major scientific contribution to the climate issue, where various scientific considerations converge to break down the boundaries between disciplines.
Author: Food and Agriculture Organization of the United Nations
Publisher: Food & Agriculture Org.
ISBN: 9251325553
Category : Technology & Engineering
Languages : en
Pages : 108
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Book Description
In the Mediterranean and the Black Sea, the assessment of demersal stocks mainly relies on scientific surveys (bottom and beam trawl) while the assessment of pelagic stocks is essentially based on acoustic surveys using acoustic techniques with mid-water trawling. These routine surveys-at-sea provide essential information, which in turn are crucial to fine-tune the assessments of the status of resources and to estimate more precisely indicators at the population and fish community levels. However, survey practices differ from one subregion to another, each approach having its own strengths and limitations. In addition, there is still a lack of large-scale standardized surveys aimed at analysing the diversity and distribution of the main demersal and pelagic species across the Mediterranean and the Black Sea. One way of tackling this issue is to carry out international scientific surveys covering the main demersal and pelagic stocks based on a common methodology. The methodology presented in this publication aims at supporting the planning and implementation of regional demersal (bottom and beam) trawl and pelagic acoustic surveys. It can be useful for the implementation of new surveys-at-sea in areas where demersal trawl and pelagic acoustic surveys are not regularly carried out. It can also contribute to increasing comparability between existing surveys thanks to the standardization of methods, sampling of catches and data recording and analysis. Finally, it represents a valuable tool to define minimum requirements towards sustainability and management objectives at the regional and subregional level.
Author: Gary A. Polis
Publisher: Springer Science & Business Media
ISBN: 1461570077
Category : Science
Languages : en
Pages : 475
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Book Description
Reflecting the recent surge of activity in food web research fueled by new empirical data, this authoritative volume successfully spans and integrates the areas of theory, basic empirical research, applications, and resource problems. Written by recognized leaders from various branches of ecological research, this work provides an in-depth treatment of the most recent advances in the field and examines the complexity and variability of food webs through reviews, new research, and syntheses of the major issues in food web research. Food Webs features material on the role of nutrients, detritus and microbes in food webs, indirect effects in food webs, the interaction of productivity and consumption, linking cause and effect in food webs, temporal and spatial scales of food web dynamics, applications of food webs to pest management, fisheries, and ecosystem stress. Three comprehensive chapters synthesize important information on the role of indirect effects, productivity and consumer regulation, and temporal, spatial and life history influences on food webs. In addition, numerous tables, figures, and mathematical equations found nowhere else in related literature are presented in this outstanding work. Food Webs offers researchers and graduate students in various branches of ecology an extensive examination of the subject. Ecologists interested in food webs or community ecology will also find this book an invaluable tool for understanding the current state of knowledge of food web research.
Author: Marie-Hélène Durand
Publisher: IRD Orstom
ISBN:
Category : Climatic changes
Languages : en
Pages : 612
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Author: Villy Christensen
Publisher: WorldFish
ISBN: 9711022842
Category : Aquatic ecology
Languages : en
Pages : 402
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Book Description
Author: Mercedes Pascual
Publisher: Oxford University Press
ISBN: 9780195188165
Category : Mathematics
Languages : en
Pages : 422
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Book Description
Food webs are one of the most useful, and challenging, objects of study in ecology. These networks of predator-prey interactions, conjured in Darwin's image of a "tangled bank," provide a paradigmatic example of complex adaptive systems. This book is based on a February 2004 Santa Fe Institute workshop. Its authors treat the ecology of predator-prey interactions, food web theory, structure and dynamics. The book explores the boundaries of what is known of the relationship between structure and dynamics in ecological networks and will define directions for future developments in this field.
