MEASURING THE FILTRATION EFFICIENCY OF THE CONTINUOUS PLANKTON RECORDER

The Continuous Plankton Recorder (CPR) survey has analysed over 160 00 0 plankton samples taken in the North East Atlantic over the last 60 y ears. However, flowmeters have not been routinely fitted to the record ers and there has been the implicit assumption that a CPR sample repre sents the organisms filtered from 3 m(3) of sea water. We describe an electromagnetic flowmeter designed for the CPR and present results whi ch show that on occasions the filtered volume per sample varied signif icantly from this value.