Global patterns in primary production of marine phytoplankton taxonomic groups

Documenting variations in phytoplankton primary productivity has garnered global attention. However, little is known about its composition, since the phytoplankton community is a complex assemblage of different phytoplankton taxonomic groups (PTGs) with distinct functions. This study developed an absorption-based technical solution to gain dominant PTGs' primary production, including diatoms, chlorophytes, cyanobacteria, cryptophytes, dinoflagellates, and haptophytes. The core of our method is to decompose the satellite-derived total phytoplankton absorption coefficient (a_ph(λ)) into group-specific components using a Gaussian decomposition technique constrained by diagnostic pigment analysis. Satellite-derived results over the past two decades (2002−2022) indicate that cyanobacteria dominate the equatorial and mid-low latitude oceans, accounting for more than 60 % of primary production, whereas diatoms and chlorophytes primarily prevail in coastal and mid-high latitude regions. The primary production trends of PTGs have been generally stable, with short-term (one-year) periodic fluctuations. Globally, diatoms contribute the largest share (38 %) to the variation in total primary production, followed by cyanobacteria (23 %) and chlorophytes (22 %). Our work provides the first global two-decadal record of sea surface PTGs' primary productivity variations.