Phytoplankton biomass and diversity Climate Change Initiative (PHYTO-CCI)

Phytoplankton are microscopic organisms that form the foundation of marine food webs and play a central role in regulating the Earth’s climate. Through photosynthesis, they absorb vast amounts of carbon dioxide and drive key processes in the ocean carbon cycle. However, assessing how phytoplankton communities are changing globally has been challenging due to the lack of consistent, long-term observations.

PHYTO‑CCI addresses this gap by developing new satellite‑based data products for two Essential Climate Variables (ECVs): phytoplankton carbon biomass and pigment diversity. These variables are critical for understanding the structure and functioning of marine ecosystems, as well as how they respond to climate change and other human pressures.

The project combines and evaluates multiple satellite retrieval algorithms, using optical water classification to improve accuracy across different ocean conditions. The resulting datasets include uncertainty estimates and are rigorously validated using in situ measurements and model data, followed by comprehensive scientific assessment.

By delivering globally consistent, climate‑quality datasets, PHYTO‑CCI provides new insights into the ocean biosphere and enables better monitoring of long‑term trends in marine ecosystems. These data support climate research, improve Earth system models, and enhance our ability to understand and predict changes in ocean productivity and carbon uptake.