Long-term and regional variability of phytoplankton biomass in the Northeast Atlantic (1960-1995)

Long-term regional changes in phytoplankton biomass in the Northeast Atlant ic and North Sea are investigated using data from the Continuous Plankton R ecorder survey. During the last decade there have been large changes in the long-term variation in phytoplankton biomass in the Northeast Atlantic and North Sea. Most regions, particularly in the North Sea, have shown a consi derable increase in phytoplankton biomass while the opposite pattern was se en in the northern oceanic region of the Northeast Atlantic. These differen t spatial responses show similar patterns of change to the decadal variabil ity in sea surface temperature influenced by the North Atlantic Oscillation index. Two rare oceanographic events and their relationship to the interan nual changes in phytoplankton biomass are discussed. The results highlight the importance of maintaining long-term biological monitoring programmes to assess the biological responses to slow oceanic/atmospheric processes and to rare or episodic physical events. (C) 2001 International Council for the Exploration of the Sea.