Phytoplankton pigment variations during the transition from spring bloom to oligotrophy in the northwestern Mediterranean sea

Phytoplankton taxonomic pigments and primary production were measured at the JGOFS-France time-series station DYFAMED in the northwestern Mediterranean Sea during May 1995 to investigate changes in phytoplankton composition and the biogeochemical implications (DYNAPROC experiment). The study period covered the transitional situation from late spring bloom to pre-oligotrophic. The late spring bloom situation, occurring at the beginning of the study, revealed high chlorophyll a concentrations (maximum 3 mg m(-3) at 30 m) and high primary production (maximum 497 mg C m(-2) 14 h(-1)). At the end of the experiment, the trophic regime shifted towards pre-oligotrophic and was characterized by lower chlorophyll a concentrations (