This dataset collection contains a 10 year monthly climatology and monthly composites of the fractional contributions of three phytoplankton size classes (micro-, nano- and picoplankton) over the globe for the period Sep 1997-2007, as produced by the Plymouth Marine Laboratory (PML) using SeaWIFs data. Accompanying maps are also available.

This dataset contributes to fulfilling the first objective of the National Centre for Earth Observation (NCEO) Theme 2 programme (Monitoring, Diagnosis and Prediction of the Global Carbon-Cycle), Quantification of ocean biogeochemistry and carbon fluxes sub-theme 6 (ST6): Quantify the global oceanic organic C cycle using OC data, partitioned into phytoplankton (pigments, biomass, size structure & PFTs), particulate organic C, coloured dissolved organic matter (CDOM), dissolved and particulate inorganic components.

Understanding the interaction between phytoplankton and the in-water light field is crucial to model ocean primary production and to improve our comprehension of the role of biological processes in the ocean–carbon cycle. The absorption coefficient of phytoplankton is a fundamental quantity in marine primary production models because:
- it alters the transmission of light underwater;
- it modifies the photosynthetic response of phytoplankton to available light;
- it can be used as a direct indicator of phytoplankton abundance and phytoplankton size;
- it can be used as an indicator of environmental variability

It is well known that the phytoplankton absorption coefficient is a function of the dominant phytoplankton pigment, chlorophyll-a, and that this relationship is directly linked to changes in both pigment composition and size structure.