Phytoplankton Index Colour from the Continuous Plankton Recorder 1946-2023

The excel file consists of samples in rows, with the following information in columns - A: midpoint of sample local date and time B: midpoint of sample latitude in decimal degrees C: midpoint of sample longitude in decimal degrees D:chlorophyll index. The Continuous Plankton Recorder (CPR) is a marine sampler that is towed behind volunteer ships of opportunity at speeds of up to ∼20 knots and samples at a depth of ∼7 m below the surface. The CPR unit is a metal casing in the shape of a ∼1 m torpedo that houses a roll of silk which automatically rotates using a geared propeller system. The seawater enters the front aperture where plankton and small particles are captured onto the rotating silk, which has a mesh size of 270 µm. This silk is stored in 4 % buffered formalin to preserve the sample until microscopic analysis at the laboratory in Plymouth. The silk is cut into pre-defined sections that represent one sample and equate to 10 nautical miles of tow. The Phytoplankton Colour Index is a record of the colour gradient of the mesh as one of 4 colour categories (0,1,2,6.5) and has been shown to relate to the chlorophyll content of the water, including organisms not visible in the sample (Raitsos et al., 2013, Raitsos, D.E., Walne, A., Lavender, S.J., Licandro, P., Reid, P.C., and Edwards, M. 2013. A 60-year ocean colour data set from the Continuous Plankton Recorder. Journal of Plankton Research, 35(1).