Phytoplankton Functional Types (PFTs) are conceptual groupings of phytoplankton species, which have a ecological functionality in common (either in terms of the food web or biogeochemical cycles). Examples include nitrogen fixers (e.g. Trichodesmium), calcifiers (coccolithophores), DMS producers (e.g., Phaeocystis) and silicifiers (e.g., diatoms). The groupings are not necessarily related to physiological characteristics, but are often based on functionality (export of organic carbon to the deep ocean vs. local recycling) or other characteristics, such as cell size (pico, nano and micro-phytoplankton).
PFTs are of interest to the biogeochemical community because they are relevant proxies of ecosystem functioning, and may be a function of climate change, with potential impacts on the efficiency of ocean carbon sequestration. Incorporation of PFTs into biogeochemical models may improve the predictive capabilities of such models.
PFTs can be derived from ocean-colour remote sensing both through direct effects (e.g. changes in phytoplankton composition can lead to changes in absorption and backscattering coefficients, affecting the reflectance spectra) as well as indirect effects (e.g. changes in phytoplankton composition is accompanied by changes in the ensemble of particles and dissolved substances, leading to changes in the reflectance spectra).
Members
Jim Aiken CASIX/Plymouth Marine Laboratory, UK
Séverine Alvain Université du Littoral, France
Aurea Ciotti São Paulo State University, Brazil
Hervé Claustre Laboratoire d’Océanographie de Villefranche (LOV), France
Julia Uitz Scripps Institution of Oceanography, USA
Lesley Clementson CSIRO, Australia
Susanne E. Craig Dalhousie University, Canada
Emmanuel Devred Bedford Institute of Oceanography, Canada
Corinne Le Quéré University of East Anglia , UK
Cyril Moulin LSCE/IPSL, France
Collin S. Roesler University of Maine, USA
Shubha Sathyendranath Plymouth Marine Laboratory, UK
Heidi M. Sosik Woods Hole Oceanographic Institution, USA
Darius Stramski Scripps Institution of Oceanography, USA
Terms of Reference:
- Establish the relevance of identifying phytoplankton functional types (PFTs) from ocean colour (OC) measurements.
- Define the major PFTs and propose a common terminology.
- Summarize our current understanding of the physics of PFTs identification from OC: from cell size and pigment composition to inherent optical properties (IOPs) and to marine reflectances.
- Review existing techniques/algorithms to detect PFTs from marine reflectance: from radiative transfer simulations to empirical relationships.
- Compare the results of the various algorithms on selected case studies and at different scales (regional vs. global).
- Examine the interest of the identification of PFTs from OC for chlorophyll and primary production estimates.
- Examine how PFTs derived from OC can be meaningful for the validation/improvement of global biogeochemical models.
- Make recommendations about which studies/measurements are needed to (1) better understand the relationships between marine reflectances and PFTs, (2) validate the PFT products, and (3) further improve the algorithms.
- Make recommendations about the specification of future OC sensors to improve PFT identification.
- Prepare a report to be published within the IOCCG series.
The sixth International Ocean Colour Science (IOCS) meeting will take place in Darmstadt, Germany from 1 – 4 December 2025, hosted by EUMETSAT and ESA with support from other agencies.