DYNAMIQUE SAISONNIERE ET VARIABILITE PIGMENTAIRE DES POPULATIONS PHYTOPLANCTONIQUES DANS L'ATLANTIQUE NORD (GOLFE DE GASCOGNE)

• Main Author: LAMPERT, LUIS
• Other Authors: Service Hydrographique et Océanographique de la Marine (SHOM), Ministère de la Défense, S.H.O.M., UNIVERSITE DE BRETAGNE OCCIDENTALE, Dr. QUEGUINER Bernard
• Format: Thesis
• Language: French
• Published: HAL CCSD 2001
• Subjects: BAY OF BISCAY; PHYTOPLANKTON; HPLC; GOLFE DE GASCOGNE; PHYTOPLANCTON; PIGMENTS; envir; geo; North Atlantic
• Online Access: https://hal.archives-ouvertes.fr/tel-01280376/file/Lampert%202001%20these.pdf; https://hal.archives-ouvertes.fr/tel-01280376

Phytoplankton dynamics on the French Atlantic continental shelf (PCAF) have been studied by pigment analysis using High Performance Liquid Chromatography (HPLC) and a data analysis protocol following the chemotaxonomic approach using the CHEMTAX software.The study shows the good agreement between the results of pigment analysis and the results of phytoplankton countings for diatoms, prymnesiophyceans, cryptophyceans, and cyanobacteria. The limits of the ecological interpretation of pigment analysis results is acceptable with the major exception of dinoflagellates; this probably results from heterotrophy and endosymbiosis which are common features of the group and thus microscopic countings remains the best method for dinoflagellate evaluation. For picophytoplanktonic classes, flow cytometry also remains the reference method. The combined use of size fractionation and pigment analysis was found to be a good analytical approach in ecological studies; this can be improved by the exhaustive study and knowledge of the main algal classes. The microscopic analysis of the dominant species helps in identifying unusual situations like the Gymnodinium chlorophorum bloom observed in June 1999. Classical analytical approaches including microscopic countings and flow cytometry should always be used in conjunction with HPLC pigment analysis.The phytoplankton cycle of the PCAF is described. On the PCAF combined actions of winds, rain, and irradiance control the position of river plumes and their ability to export off shore their physical (temperature) as well as chemical (salinity, nutrient concentrations) properties. Nutrients can rapidly be exhausted by the end of winter when favourable conditions are settled and a species succession starts precociously. The succession is closely controlled by the physical environment which results in large interannual variability, especially in winter and spring.Diatoms are present all year round on the PCAF but their dominance is at its maximum in winter and spring. A spatial segregation ...