PHYTOPLANKTON CARBON INCORPORATION PATTERNS AND BIOCHEMICAL-COMPOSITION OF PARTICULATE MATTER IN THE EASTERN NORTH-ATLANTIC SUBTROPICAL REGION

Photosynthetic carbon metabolism and the biochemical composition of la te-winter phytoplankton assemblages in the eastern North Atlantic Ocea n were studied during an oceanographic cruise carried out in March 199 2. Enhanced levels of phytoplankton biomass and primary production wer e linked to the subtropical front-Azores Current (STF/AC) region. High values of the relative incorporation of carbon into proteins indicate d that the phytoplankton was growing at a rate close to the maximum gr owth rate. A very high percentage of carbon was incorporated into the lipid fraction at southern latitudes, whereas incorporation into polys accharides peaked al the AC. In general, the biochemical composition o f particulate matter reflected the observed patterns of photosynthate partitioning. Latitudinal changes in phytoplankton species composition accounted for the geographical Variability in C-14 labelling patterns . Turnover times of particulate matter estimated for the STF/AC region were relatively low (3-5 days) and suggested balanced growth of the m icroplankton community over daily time scales.