Ecologie des foraminifères planctoniques du golfe de Gascogne : variations spatio-temporelles des assemblages et géochimie de leurs tests
This PhD was realised within the framework of the research project ANR FORCLIM. The fundamental aim of this study focused on the ecology of planktic foraminifera in the recent ecosystem of the Bay of Biscay. Samples from plankton tows and hydrological data were collected during 5 cruises. Results sh...
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| Other Authors: | , , , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | French |
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HAL CCSD
2009
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| Subjects: | |
| Online Access: | https://theses.hal.science/tel-00480660 https://theses.hal.science/tel-00480660/document https://theses.hal.science/tel-00480660/file/These_Sophie_Retailleau.pdf |
| Summary: | This PhD was realised within the framework of the research project ANR FORCLIM. The fundamental aim of this study focused on the ecology of planktic foraminifera in the recent ecosystem of the Bay of Biscay. Samples from plankton tows and hydrological data were collected during 5 cruises. Results show a strong seasonal variation in planktic foraminiferal densities and species assemblages. Faunal assemblages changed in quantity and quality on a seasonal scale. High concentrations of N. pachyderma dextral, G. inflata, G. scitula, and G. glutinata marked the end of winter and the beginning of spring in the plankton community. T. quinqueloba, G. uvula, G. bulloides and G. glutinata were abundant during the spring phytoplanktonic bloom. During the summer, these species were progressively replaced by others species, such as O. universa and G. trilobus at low water depths, and G. scitula at greater depths. From March to June, along a bathymetric transect, planktic foraminiferal concentrations decreased toward the coast. Seasonal variability of nutrients derived from river discharge, or hydrological effects caused by sub marine canyons did affect the distribution of planktic foraminifers. In November, G. calida was abundant at onshore stations, marking an autumn bloom event. Size analysis of living and dead specimens showed that planktonic foraminifera were larger during summer. Temperature did not seem to significantly affect size variation of planktic foraminifers. It can be assumed that food supply, salinity and turbidity do affect the distribution of planktic foraminifers. Stable oxygen isotope ratios from tests of living planktic foraminifers indicate that populations in June were clearly lower than March and April populations, suggesting that they are from different generations. Cette thèse a été réalisée dans le cadre du projet de recherche ANR FORCLIM. L'objectif fondamental de ce travail était d'effectuer une étude poussée de l'écologie des foraminifères planctoniques dans les écosystèmes actuels du Golfe de ... |
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