Instrument: Continous Plankton Recorder


The CPR is a plankton sampling instrument designed to be towed from merchant ships or ships of opportunity on their normal sailings. The CPR is towed at a depth of approximately 10 metres. Water passes through the CPR and plankton are filtered onto a slow-moving band of silk (270 micrometre mesh size) and covered by a second silk. The silks and plankton are then spooled into a storage tank containing formalin. On return to the laboratory, the silk is removed from the mechanism and divided into samples representing 10 nautical miles (19 km) of tow.

CPR samples are analyzed in two ways. Firstly, the Phytoplankton Color Index (PCI) is determined for each sample. The colour of the silk is evaluated against a standard colour chart and given a 'green-ness' value based on the visual discoloration of the CPR silk produced by green chlorophyll pigments; the PCI is a semiquantitative estimate of phytoplankton biomass. In this way the PCI takes into account the chloroplasts of broken cells and small phytoplankton which cannot be counted during the microscopic analysis stage. After determination of the PCI, microscopic analysis is undertaken for each sample, and individual phytoplankton and zooplanktontaxa are identified and counted.

Reid, P.C.; Colebrook, J.M.; Matthews, J.B.L.; Aiken, J.; et al. (2003). "The Continuous Plankton Recorder: concepts and history, from plankton indicator to undulating recorders".Progress in Oceanography 58(2-4): 117-175. doi:10.1016/j.pocean.2003.08.002.

Warner, A.J., and Hays, G.C.,; Hays, G (1994). "Sampling by the Continuous Plankton Recorder survey". Progress in Oceanography 34(2–3): 237–256. doi:10.1016/0079-6611(94)90011-6.