THE SPATIAL AND TEMPORAL DEVELOPMENT OF THE SPRING BLOOM DURING THE JGOFS NORTH-ATLANTIC BLOOM EXPERIMENT, 1989

The south to north development of the spring bloom in the North Atlant ic Ocean was observed during four cruises from April to August 1989. T ransects with towed undulating instrumentation packages and CTD profil es on station were made between 42-degrees-N and 54-degrees-N, along 1 7-degrees-W and 20-degrees-W in April and between 47-degrees-N and 60- degrees-N along 20-degrees-N in May, June and July/August, giving vert ical sections of temperature and chlorophyll concentration derived fro m in vivo fluorescence. These sections show the relationship between t he onset of seasonal stratification and the initiation of the spring b loom. Supporting data from microscopic analysis of the major phytoplan kton species show that the seasonal succession commenced with diatoms, followed in tum by coccolithophores, flagellates and dinoflagellates. During the development of summer stratification the mesoscale distrib ution of chlorophyll was strongly determined by the depth of the mixed layer, but once stratification had been firmly established higher chl orophyll values tended to be found within the warmer eddies (meanders) . One possible explanation of this result is that phytoplankton growth is higher in the warmer eddies.