Calanus finmarchicus in the North Atlantic: the year of Calanus in the context of interdecadal change

Using data collected by the Continuous Plankton Recorder survey, ne review the regional characteristics of Calanus populations from distinct areas of the North Atlantic and update the observations of dominant changes that hav e occurred during the past four decades. Timing of the seasonal cycle of ab undance of C. finmarchicus can vary by up to four months between oceanic pr ovinces. We provide the first pan-Atlantic estimate of the contribution of C. finmarchicus to the biomass of the planktonic ecosystem in comparison wi th other copepod taxa. This estimate reveals that, over most of the North A tlantic, C. finmarchicus represents more than half the copepod biomass samp led by the CPR. Comparison of the abundance of C. finmarchicus recorded dur ing the "Year of Calanus" (1997) with that recorded in the past indicates t hat, in the Northeast Atlantic, the abundance and relative biomass of the s pecies during the TASC years have been the lon est ever recorded. (C) 2000 International Council for the Exploration of the Sea.