Phytoplankton Colour Index (PCI)
The Phytoplankton Colour Index (PCI) is the visual estimation of the green colour of the silk mesh that filters the surface waters. This colouration is due to the green chlorophyll pigments derived from chloroplasts of intact and broken cells and small unarmoured flagellates (Batten et al., 2003).
There are four levels of greenness which are visually assigned by
comparison with standard colour charts (Colebrook, 1960):
Code 0 = No Colour
Code 1 = Very Pale Green
Code 2 = Pale Green
Code 6.5 = Green
The PCI has been extensively used to describe the major temporal and spatial patterns of phytoplankton. It has also been used as an indicator of phytoplankton standing stock as previous studies have shown that this index overall varies consistently with phytoplankton biomass.
References for PCI methodology
Batten, SD, Clarke R, Flinkman J et al. (2003). CPR sampling: the technical background, material and methods, consistency and comparability. Progress in Oceanography, 58, 193-215.
Colebrook, J. M. (1960). Continuous Plankton records: methods of analysis, 1950-59. Bulletins of Marine Ecology, 5, 51-64
