What we have learned about plankton variability and its physical controls from 70 years of CPR records

The first tow of the Continuous Plankton Recorder (CPR) Survey took place in September 1931 between Hull and Hamburg in the North Sea. The development of the CPR was, for Sir Alister Hardy, one contribution to the "great plan" of ICES, the ultimate aim of which was "the rational exploitation of the sea". Seven decades and 200 000 samples later, the survey is the longest plankton monitoring programme ever carried out and is now a major player in biological oceanography research in the North Atlantic. From the description of plankton species in the early days of the survey, the knowledge gained from the CPR has evolved to spatial distribution, seasonal dynamics, interannual and interdecadal variability, responses of populations to climatic forcing, and changes in the ecosystem structure and dynamics. The building of the CPR plankton series, which has paralleled the initiation and maintenance of monitoring programmes by ICES, has provided support and interpretative power to the many environmental and biological data series collected under the auspices of the Council. These data series now form the basis of our understanding of the North Atlantic ecosystem over the scale of greatest variability: the multi-decadal scale.