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The location of the Antarctic Polar Front (PF) is mapped in the Southern Indian Ocean bydecomposing the shape of temperature and salinity profiles into vertical modes using a functional PrincipalComponent Analysis. We define the PF as the northernmost minimum of temperature at the subsurface andrepresent it as a linear combination of the first three modes. This method is applied on an ocean reanalysisdata set and on in situ observations, revealing a seasonal variability of the PF latitudinal position that ismost pronounced between the Conrad Rise and the Kerguelen Plateau. This shift coincides with variationsin the transport across the Northern Kerguelen Plateau. We suggest that seasonal changes of the upperstratification may drive the observed variability of the PF, with potentially large implications for thepathways and residence time of water masses over the plateau and the phytoplankton bloom extendingsoutheast of the Kerguelen Islands.

The location of the Antarctic Polar Front (PF) is mapped in the Southern Indian Ocean bydecomposing the shape of temperature and salinity profiles into vertical modes using a functional PrincipalComponent Analysis. We define the PF as the northernmost minimum of temperature at the subsurface andrepresent it as a linear combination of the first three modes. This method is applied on an ocean reanalysisdata set and on in situ observations, revealing a seasonal variability of the PF latitudinal position that ismost pronounced between the Conrad Rise and the Kerguelen Plateau. This shift coincides with variationsin the transport across the Northern Kerguelen Plateau. We suggest that seasonal changes of the upperstratification may drive the observed variability of the PF, with potentially large implications for thepathways and residence time of water masses over the plateau and the phytoplankton bloom extendingsoutheast of the Kerguelen Islands.

The location of the Antarctic Polar Front (PF) is mapped in the Southern Indian Ocean bydecomposing the shape of temperature and salinity profiles into vertical modes using a functional PrincipalComponent Analysis. We define the PF as the northernmost minimum of temperature at the subsurface andrepresent it as a linear combination of the first three modes. This method is applied on an ocean reanalysisdata set and on in situ observations, revealing a seasonal variability of the PF latitudinal position that ismost pronounced between the Conrad Rise and the Kerguelen Plateau. This shift coincides with variationsin the transport across the Northern Kerguelen Plateau. We suggest that seasonal changes of the upperstratification may drive the observed variability of the PF, with potentially large implications for thepathways and residence time of water masses over the plateau and the phytoplankton bloom extendingsoutheast of the Kerguelen Islands.

The location of the Antarctic Polar Front (PF) is mapped in the Southern Indian Ocean bydecomposing the shape of temperature and salinity profiles into vertical modes using a functional PrincipalComponent Analysis. We define the PF as the northernmost minimum of temperature at the subsurface andrepresent it as a linear combination of the first three modes. This method is applied on an ocean reanalysisdata set and on in situ observations, revealing a seasonal variability of the PF latitudinal position that ismost pronounced between the Conrad Rise and the Kerguelen Plateau. This shift coincides with variationsin the transport across the Northern Kerguelen Plateau. We suggest that seasonal changes of the upperstratification may drive the observed variability of the PF, with potentially large implications for thepathways and residence time of water masses over the plateau and the phytoplankton bloom extendingsoutheast of the Kerguelen Islands.

The location of the Antarctic Polar Front (PF) is mapped in the Southern Indian Ocean bydecomposing the shape of temperature and salinity profiles into vertical modes using a functional PrincipalComponent Analysis. We define the PF as the northernmost minimum of temperature at the subsurface andrepresent it as a linear combination of the first three modes. This method is applied on an ocean reanalysisdata set and on in situ observations, revealing a seasonal variability of the PF latitudinal position that ismost pronounced between the Conrad Rise and the Kerguelen Plateau. This shift coincides with variationsin the transport across the Northern Kerguelen Plateau. We suggest that seasonal changes of the upperstratification may drive the observed variability of the PF, with potentially large implications for thepathways and residence time of water masses over the plateau and the phytoplankton bloom extendingsoutheast of the Kerguelen Islands.

The location of the Antarctic Polar Front (PF) is mapped in the Southern Indian Ocean bydecomposing the shape of temperature and salinity profiles into vertical modes using a functional PrincipalComponent Analysis. We define the PF as the northernmost minimum of temperature at the subsurface andrepresent it as a linear combination of the first three modes. This method is applied on an ocean reanalysisdata set and on in situ observations, revealing a seasonal variability of the PF latitudinal position that ismost pronounced between the Conrad Rise and the Kerguelen Plateau. This shift coincides with variationsin the transport across the Northern Kerguelen Plateau. We suggest that seasonal changes of the upperstratification may drive the observed variability of the PF, with potentially large implications for thepathways and residence time of water masses over the plateau and the phytoplankton bloom extendingsoutheast of the Kerguelen Islands.

Climate change has a strong impact on marine ecosystems, including temperate species. Analysing the diversity of thermotolerance levels within species along with their genetic structure enables a better understanding of their potential response to climate change. We performed this integrative study on the Mediterranean octocoral Eunicella cavolini, with samples from different depths and by means of a common garden experiment. This species does not host photosynthetic Symbiodinium, enabling us to focus on the cnidarian response. We compared the thermotolerance of individuals from 20 m and 40 m depths from the same site and with replicates from the same colony. On the basis of an innovative statistical analysis of necrosis kinetics and risk, we demonstrated the occurrence of a very different response between depths at this local scale, with lower thermotolerance of deep individuals. Strongly thermotolerant individuals were observed at 20 m with necrosis appearing at higher temperatures than observed in situ. On the basis of nine microsatellite loci, we showed that these marked thermotolerance differences occur within a single population. This suggests the importance of acclimatization processes in adaptation to these different depths. In addition, differences between replicates demonstrated the occurrence of a variability of response between fragments from the same colony with the possibility of an interaction with a tank effect. Our results provide a basis for studying adaptation and acclimatization in Mediterranean octocorals in a heterogeneous environment.

Climate change has a strong impact on marine ecosystems, including temperate species. Analysing the diversity of thermotolerance levels within species along with their genetic structure enables a better understanding of their potential response to climate change. We performed this integrative study on the Mediterranean octocoral Eunicella cavolini, with samples from different depths and by means of a common garden experiment. This species does not host photosynthetic Symbiodinium, enabling us to focus on the cnidarian response. We compared the thermotolerance of individuals from 20 m and 40 m depths from the same site and with replicates from the same colony. On the basis of an innovative statistical analysis of necrosis kinetics and risk, we demonstrated the occurrence of a very different response between depths at this local scale, with lower thermotolerance of deep individuals. Strongly thermotolerant individuals were observed at 20 m with necrosis appearing at higher temperatures than observed in situ. On the basis of nine microsatellite loci, we showed that these marked thermotolerance differences occur within a single population. This suggests the importance of acclimatization processes in adaptation to these different depths. In addition, differences between replicates demonstrated the occurrence of a variability of response between fragments from the same colony with the possibility of an interaction with a tank effect. Our results provide a basis for studying adaptation and acclimatization in Mediterranean octocorals in a heterogeneous environment.

Climate change has a strong impact on marine ecosystems, including temperate species. Analysing the diversity of thermotolerance levels within species along with their genetic structure enables a better understanding of their potential response to climate change. We performed this integrative study on the Mediterranean octocoral Eunicella cavolini, with samples from different depths and by means of a common garden experiment. This species does not host photosynthetic Symbiodinium, enabling us to focus on the cnidarian response. We compared the thermotolerance of individuals from 20 m and 40 m depths from the same site and with replicates from the same colony. On the basis of an innovative statistical analysis of necrosis kinetics and risk, we demonstrated the occurrence of a very different response between depths at this local scale, with lower thermotolerance of deep individuals. Strongly thermotolerant individuals were observed at 20 m with necrosis appearing at higher temperatures than observed in situ. On the basis of nine microsatellite loci, we showed that these marked thermotolerance differences occur within a single population. This suggests the importance of acclimatization processes in adaptation to these different depths. In addition, differences between replicates demonstrated the occurrence of a variability of response between fragments from the same colony with the possibility of an interaction with a tank effect. Our results provide a basis for studying adaptation and acclimatization in Mediterranean octocorals in a heterogeneous environment.

Analytical flow cytometry (FCM) is well suited for the analysis of phytoplankton communities in fresh and sea waters. The measurement of light scatter and autofluorescence properties of particles by FCM provides optical fingerprints, which enables different phytoplankton groups to be separated. A submersible version of the CytoSense flow cytometer (the CytoSub) has been designed for in situ autonomous sampling and analysis, making it possible to monitor phytoplankton at a short temporal scale and obtain accurate information about its dynamics. For data analysis, a manual clustering is usually performed a posteriori: data are displayed on histograms and scatterplots, and group discrimination is made by drawing and combining regions (gating). The purpose of this study is to provide greater objectivity in the data analysis by applying a nonmanual and consistent method to automatically discriminate clusters of particles. In other words, we seek for partitioning methods based on the optical fingerprints of each particle. As the CytoSense is able to record the full pulse shape for each variable, it quickly generates a large and complex dataset to analyze. The shape, length, and area of each curve were chosen as descriptors for the analysis. To test the developed method, numerical experiments were performed on simulated curves. Then, the method was applied and validated on phytoplankton cultures data. Promising results have been obtained with a mixture of various species whose optical fingerprints overlapped considerably and could not be accurately separated using manual gating. © 2011 International Society for Advancement of Cytometry., Analytical flow cytometry (FCM) is well suited for the analysis of phytoplankton communities in fresh and sea waters. The measurement of light scatter and autofluorescence properties of particles by FCM provides optical fingerprints, which enables different phytoplankton groups to be separated. A submersible version of the CytoSense flow cytometer (the CytoSub) has been designed for in situ autonomous sampling and analysis, making it possible to monitor phytoplankton at a short temporal scale and obtain accurate information about its dynamics. For data analysis, a manual clustering is usually performed a posteriori: data are displayed on histograms and scatterplots, and group discrimination is made by drawing and combining regions (gating). The purpose of this study is to provide greater objectivity in the data analysis by applying a nonmanual and consistent method to automatically discriminate clusters of particles. In other words, we seek for partitioning methods based on the optical fingerprints of each particle. As the CytoSense is able to record the full pulse shape for each variable, it quickly generates a large and complex dataset to analyze. The shape, length, and area of each curve were chosen as descriptors for the analysis. To test the developed method, numerical experiments were performed on simulated curves. Then, the method was applied and validated on phytoplankton cultures data. Promising results have been obtained with a mixture of various species whose optical fingerprints overlapped considerably and could not be accurately separated using manual gating. © 2011 International Society for Advancement of Cytometry.

Analytical flow cytometry (FCM) is well suited for the analysis of phytoplankton communities in fresh and sea waters. The measurement of light scatter and autofluorescence properties of particles by FCM provides optical fingerprints, which enables different phytoplankton groups to be separated. A submersible version of the CytoSense flow cytometer (the CytoSub) has been designed for in situ autonomous sampling and analysis, making it possible to monitor phytoplankton at a short temporal scale and obtain accurate information about its dynamics. For data analysis, a manual clustering is usually performed a posteriori: data are displayed on histograms and scatterplots, and group discrimination is made by drawing and combining regions (gating). The purpose of this study is to provide greater objectivity in the data analysis by applying a nonmanual and consistent method to automatically discriminate clusters of particles. In other words, we seek for partitioning methods based on the optical fingerprints of each particle. As the CytoSense is able to record the full pulse shape for each variable, it quickly generates a large and complex dataset to analyze. The shape, length, and area of each curve were chosen as descriptors for the analysis. To test the developed method, numerical experiments were performed on simulated curves. Then, the method was applied and validated on phytoplankton cultures data. Promising results have been obtained with a mixture of various species whose optical fingerprints overlapped considerably and could not be accurately separated using manual gating. © 2011 International Society for Advancement of Cytometry., Analytical flow cytometry (FCM) is well suited for the analysis of phytoplankton communities in fresh and sea waters. The measurement of light scatter and autofluorescence properties of particles by FCM provides optical fingerprints, which enables different phytoplankton groups to be separated. A submersible version of the CytoSense flow cytometer (the CytoSub) has been designed for in situ autonomous sampling and analysis, making it possible to monitor phytoplankton at a short temporal scale and obtain accurate information about its dynamics. For data analysis, a manual clustering is usually performed a posteriori: data are displayed on histograms and scatterplots, and group discrimination is made by drawing and combining regions (gating). The purpose of this study is to provide greater objectivity in the data analysis by applying a nonmanual and consistent method to automatically discriminate clusters of particles. In other words, we seek for partitioning methods based on the optical fingerprints of each particle. As the CytoSense is able to record the full pulse shape for each variable, it quickly generates a large and complex dataset to analyze. The shape, length, and area of each curve were chosen as descriptors for the analysis. To test the developed method, numerical experiments were performed on simulated curves. Then, the method was applied and validated on phytoplankton cultures data. Promising results have been obtained with a mixture of various species whose optical fingerprints overlapped considerably and could not be accurately separated using manual gating. © 2011 International Society for Advancement of Cytometry.

Two trawl surveys (1 993 may, october) have been conducted by the IFREMER in order to carry out a typology of demersal populations and to map the spatial distribution of the penaeid shrimp Penoeus subtilis (French Guyana shrimp fishery Deet target species) over the French Guyana continental shelf. For this purpose, a particular data analyses procedure was designed. On one hand, inertia and cluster analysis were used to detemline the main structures of dcmersal communities. On the other hand, mapping of Penaeus subtilis distribution, and espccially of the recruits in the fisher)', \Vas obtained through geostatistic technique. Impacts of the Amazon and Guyana ri vers on the demersal ecosystem are strong. They inducc separation between the demersal communities, in-shore and off-shore species. The 25-30 met ers strata may be considered as a "buffer" area, between briny shallow waters and off-shore marine waters, respectively associated with muddy (Amazon alluvionary influence) and sandy (fine to rough) sedimentodological facies. For Penaeus subtilis, results show a spatial distribution gradient with respect to dcpth, and a particular distribution pattern within the transition zone. Three prcferential distribution areas have becn identified off the main Guyane rivers ': Maroni, Oyapock and Sinnamary. The Penaeus subtilis recruitment mecanism have been completed, large concentrations of recruits being pointed out off the Maroni and Oyapock rivers, up to 40 meters in depth, Deux campagnes de chalutage (mai et octobre 1993) ont été réalisées par l'IFREMER, l'objectif étant d'obtenir une typologie des peuplements démersaux du plateau continental de la Guyane française et de cartographier la répartition de la crevette Penaeus subtilis (espèce cible de la pêcherie crevettière guyanaise). Un protocole d'analyse de données a été élaboré à cet effet. Des techniques d'analyse d'inertie et de classification ont servi à la détermination des principales structures des peuplements démersaux et une méthode de géostastique a été employée pour cartographier la répartition de Penaeus subtilis et en particulier celle des recrues dans la pêcherie. L'influence de l'Amazone et des fleuves guyanais sur l'écosytème démersal est forte, leur impact semble induire une différenciation de deux peuplements démersaux; l'un côtier, l'autre hauturier. Ces deux peuplements sont séparés par la strate de profondeur 25-30 mètres qui jouerait le rôle de zone "tampon" entre les eaux côtières dessalées et les eaux marines du large, dont les faciès sédimentologiques associés sont respectivement vaseux (influence des dépots alluvionnaires de l'Amazone) et sableux (fin à grossier). La crevette Penoeus subtilis semble avoir un préférendum de répartition dans cette zone d'interface. La technique de cartographie par krigeage a permis d'identifier des zones privilégiées de distribution au large des trois grands fleuves de Guyane, le Maroni, l'Oyapock, et la Sinnamary: Cette étude a permis de plus de compléter les connaissances par ailleurs encore partielle du mécanisme de recrutement de cette espèce, puisque de fortes concentrations de recrues ont été identifiées au large des fleuves Maroni et Oyapock, sur des fonds atteignant 40 mètres.

Two trawl surveys (1 993 may, october) have been conducted by the IFREMER in order to carry out a typology of demersal populations and to map the spatial distribution of the penaeid shrimp Penoeus subtilis (French Guyana shrimp fishery Deet target species) over the French Guyana continental shelf. For this purpose, a particular data analyses procedure was designed. On one hand, inertia and cluster analysis were used to detemline the main structures of dcmersal communities. On the other hand, mapping of Penaeus subtilis distribution, and espccially of the recruits in the fisher)', \Vas obtained through geostatistic technique. Impacts of the Amazon and Guyana ri vers on the demersal ecosystem are strong. They inducc separation between the demersal communities, in-shore and off-shore species. The 25-30 met ers strata may be considered as a "buffer" area, between briny shallow waters and off-shore marine waters, respectively associated with muddy (Amazon alluvionary influence) and sandy (fine to rough) sedimentodological facies. For Penaeus subtilis, results show a spatial distribution gradient with respect to dcpth, and a particular distribution pattern within the transition zone. Three prcferential distribution areas have becn identified off the main Guyane rivers ': Maroni, Oyapock and Sinnamary. The Penaeus subtilis recruitment mecanism have been completed, large concentrations of recruits being pointed out off the Maroni and Oyapock rivers, up to 40 meters in depth, Deux campagnes de chalutage (mai et octobre 1993) ont été réalisées par l'IFREMER, l'objectif étant d'obtenir une typologie des peuplements démersaux du plateau continental de la Guyane française et de cartographier la répartition de la crevette Penaeus subtilis (espèce cible de la pêcherie crevettière guyanaise). Un protocole d'analyse de données a été élaboré à cet effet. Des techniques d'analyse d'inertie et de classification ont servi à la détermination des principales structures des peuplements démersaux et une méthode de géostastique a été employée pour cartographier la répartition de Penaeus subtilis et en particulier celle des recrues dans la pêcherie. L'influence de l'Amazone et des fleuves guyanais sur l'écosytème démersal est forte, leur impact semble induire une différenciation de deux peuplements démersaux; l'un côtier, l'autre hauturier. Ces deux peuplements sont séparés par la strate de profondeur 25-30 mètres qui jouerait le rôle de zone "tampon" entre les eaux côtières dessalées et les eaux marines du large, dont les faciès sédimentologiques associés sont respectivement vaseux (influence des dépots alluvionnaires de l'Amazone) et sableux (fin à grossier). La crevette Penoeus subtilis semble avoir un préférendum de répartition dans cette zone d'interface. La technique de cartographie par krigeage a permis d'identifier des zones privilégiées de distribution au large des trois grands fleuves de Guyane, le Maroni, l'Oyapock, et la Sinnamary: Cette étude a permis de plus de compléter les connaissances par ailleurs encore partielle du mécanisme de recrutement de cette espèce, puisque de fortes concentrations de recrues ont été identifiées au large des fleuves Maroni et Oyapock, sur des fonds atteignant 40 mètres.

Two trawl surveys (1 993 may, october) have been conducted by the IFREMER in order to carry out a typology of demersal populations and to map the spatial distribution of the penaeid shrimp Penoeus subtilis (French Guyana shrimp fishery Deet target species) over the French Guyana continental shelf. For this purpose, a particular data analyses procedure was designed. On one hand, inertia and cluster analysis were used to detemline the main structures of dcmersal communities. On the other hand, mapping of Penaeus subtilis distribution, and espccially of the recruits in the fisher)', \Vas obtained through geostatistic technique. Impacts of the Amazon and Guyana ri vers on the demersal ecosystem are strong. They inducc separation between the demersal communities, in-shore and off-shore species. The 25-30 met ers strata may be considered as a "buffer" area, between briny shallow waters and off-shore marine waters, respectively associated with muddy (Amazon alluvionary influence) and sandy (fine to rough) sedimentodological facies. For Penaeus subtilis, results show a spatial distribution gradient with respect to dcpth, and a particular distribution pattern within the transition zone. Three prcferential distribution areas have becn identified off the main Guyane rivers ': Maroni, Oyapock and Sinnamary. The Penaeus subtilis recruitment mecanism have been completed, large concentrations of recruits being pointed out off the Maroni and Oyapock rivers, up to 40 meters in depth, Deux campagnes de chalutage (mai et octobre 1993) ont été réalisées par l'IFREMER, l'objectif étant d'obtenir une typologie des peuplements démersaux du plateau continental de la Guyane française et de cartographier la répartition de la crevette Penaeus subtilis (espèce cible de la pêcherie crevettière guyanaise). Un protocole d'analyse de données a été élaboré à cet effet. Des techniques d'analyse d'inertie et de classification ont servi à la détermination des principales structures des peuplements démersaux et une méthode de géostastique a été employée pour cartographier la répartition de Penaeus subtilis et en particulier celle des recrues dans la pêcherie. L'influence de l'Amazone et des fleuves guyanais sur l'écosytème démersal est forte, leur impact semble induire une différenciation de deux peuplements démersaux; l'un côtier, l'autre hauturier. Ces deux peuplements sont séparés par la strate de profondeur 25-30 mètres qui jouerait le rôle de zone "tampon" entre les eaux côtières dessalées et les eaux marines du large, dont les faciès sédimentologiques associés sont respectivement vaseux (influence des dépots alluvionnaires de l'Amazone) et sableux (fin à grossier). La crevette Penoeus subtilis semble avoir un préférendum de répartition dans cette zone d'interface. La technique de cartographie par krigeage a permis d'identifier des zones privilégiées de distribution au large des trois grands fleuves de Guyane, le Maroni, l'Oyapock, et la Sinnamary: Cette étude a permis de plus de compléter les connaissances par ailleurs encore partielle du mécanisme de recrutement de cette espèce, puisque de fortes concentrations de recrues ont été identifiées au large des fleuves Maroni et Oyapock, sur des fonds atteignant 40 mètres.

Two trawl surveys (1 993 may, october) have been conducted by the IFREMER in order to carry out a typology of demersal populations and to map the spatial distribution of the penaeid shrimp Penoeus subtilis (French Guyana shrimp fishery Deet target species) over the French Guyana continental shelf. For this purpose, a particular data analyses procedure was designed. On one hand, inertia and cluster analysis were used to detemline the main structures of dcmersal communities. On the other hand, mapping of Penaeus subtilis distribution, and espccially of the recruits in the fisher)', \Vas obtained through geostatistic technique. Impacts of the Amazon and Guyana ri vers on the demersal ecosystem are strong. They inducc separation between the demersal communities, in-shore and off-shore species. The 25-30 met ers strata may be considered as a "buffer" area, between briny shallow waters and off-shore marine waters, respectively associated with muddy (Amazon alluvionary influence) and sandy (fine to rough) sedimentodological facies. For Penaeus subtilis, results show a spatial distribution gradient with respect to dcpth, and a particular distribution pattern within the transition zone. Three prcferential distribution areas have becn identified off the main Guyane rivers ': Maroni, Oyapock and Sinnamary. The Penaeus subtilis recruitment mecanism have been completed, large concentrations of recruits being pointed out off the Maroni and Oyapock rivers, up to 40 meters in depth, Deux campagnes de chalutage (mai et octobre 1993) ont été réalisées par l'IFREMER, l'objectif étant d'obtenir une typologie des peuplements démersaux du plateau continental de la Guyane française et de cartographier la répartition de la crevette Penaeus subtilis (espèce cible de la pêcherie crevettière guyanaise). Un protocole d'analyse de données a été élaboré à cet effet. Des techniques d'analyse d'inertie et de classification ont servi à la détermination des principales structures des peuplements démersaux et une méthode de géostastique a été employée pour cartographier la répartition de Penaeus subtilis et en particulier celle des recrues dans la pêcherie. L'influence de l'Amazone et des fleuves guyanais sur l'écosytème démersal est forte, leur impact semble induire une différenciation de deux peuplements démersaux; l'un côtier, l'autre hauturier. Ces deux peuplements sont séparés par la strate de profondeur 25-30 mètres qui jouerait le rôle de zone "tampon" entre les eaux côtières dessalées et les eaux marines du large, dont les faciès sédimentologiques associés sont respectivement vaseux (influence des dépots alluvionnaires de l'Amazone) et sableux (fin à grossier). La crevette Penoeus subtilis semble avoir un préférendum de répartition dans cette zone d'interface. La technique de cartographie par krigeage a permis d'identifier des zones privilégiées de distribution au large des trois grands fleuves de Guyane, le Maroni, l'Oyapock, et la Sinnamary: Cette étude a permis de plus de compléter les connaissances par ailleurs encore partielle du mécanisme de recrutement de cette espèce, puisque de fortes concentrations de recrues ont été identifiées au large des fleuves Maroni et Oyapock, sur des fonds atteignant 40 mètres.