The feeding ecology of Calanus finmarchicus was investigated during spring 1997 at a permanent station in the Norwegian Sea (Stn M, 66°N, 2°E) as part of the TASC (Trans Atlantic Study of Calanus finmarchicus) project time-series investigations. The phytoplankton bloom began in mid May, coinciding with the onset of the stratification, and was mainly composed of diatoms and prymnesiophytes. Daily ingestion of phytoplankton by C. finmarchicus was about 2% of body carbon for the long period before the bloom, 30% during the bloom and 14 % after the bloom. Due to their low abundance, ingestion of ciliates represented only 2 to 6% of the phytoplankton ingestion. Body carbon and carbon/nitrogen ratio decreased significantly before the bloom indicating a deficit in carbon ingestion and the use of storage lipid during this period.