North Atlantic (35° N to 60° N, 71° W to 11° E). North pacific since 1997

Chlorophyll pigment concentrations in water bodies; Salinity of the water column; Temperature of the water column; Zooplankton taxonomy-related abundance per unit volume of the water column; Zooplankton non taxonomy-related abundance per unit volume of the water column; Phytoplankton generic abundance in water bodies; Phytoplankton taxonomic abundance in water bodies

Fluorometers; plankton recorders; salinity sensor

The Continuous Plankton Recorder is a piece of apparatus towed by vessels for sampling plankton near the sea surface. The CPR now used is changed little from that described by Hardy (1939). The CPRs are towed by ships-of-opportunity at a depth of 10m and are deployed as far as possible, at monthly intervals over a standard set of routes. Water enters through an aperture in the nose cone and is slowed to one thirtieth of its original speed before being filtered through a slowly moving band of bolting silk. The plankton is retained on the filtering silk and held in position by a second band of silk to form a 'sandwich' which is wound onto a spool in a tank containing a preservative (formalin) (Fig 1). The silk is cut into lengths representing 10 nautical miles of tow, and the lengths of silk are then subjected to a standard routine analysis. Each 10-mile length of tow is regarded as a sample taken at its centre point and stored with its corresponding co-ordinates. The current catalogue of CPR records lists a total of 508 taxa identified to varying taxonomic levels. Phytoplankton counts only are available for the years from 1958 onwards; before this only presence/absence is available. Data for the most abundant of the zooplankton taxa are available for the years from 1946, and data for all are available from 1958. For the pre-war years, when the survey was being developed, only a few taxa are as yet available. Some effort is being expended in an attempt to extract more data from the notebooks of the period. Data handling procedures in the CPR survey have evolved alongside the development of the laboratory computer, with the data archive and retrieval systems being elaborated as computer systems became more sophisticated. Since the Survey was established nearly 75 years ago, over 196,000 samples have been analysed and the data entered into the data archive. Since 1994 the CPRs towed on some routes have been instrumented to measure either temperature alone or conductivity (salinity), temperature, depth and chlorophyll fluorescence. On return to the SAHFOS laboratory these data (typically at 2 minute intervals) are assigned a position by interpolation of a CPR tow record provided by the towing vessel. The data are quality controlled by comparison with data from the previous month and year on the same route. The accuracy of the instruments are checked at 6 month intervals.

Hardy, A.C. (1939) Ecological investigations with the Continuous Plankton Recorder: object, plan and methods., Hull Bulletins of Marine Ecology, 1: 1-47.

Sir Alister Hardy Foundation for Ocean Science
The Laboratory Citadel Hill
Plymouth
Devon
PL1 2PB
United Kingdom