Published in Nature Climate Change, the research analysed ESA's Climate Change Initiative records of sea surface temperature, ocean colour and sea ice extent, combined with pigment data from over 14,000 in-situ samples collected between 1997 and 2023. Machine learning models linked satellite and sample data to map phytoplankton group changes.
Results show a marked decline in diatoms across the Antarctic continental shelf until 2016, when sea ice retreat triggered both a diatom rebound and rapid cryptophyte growth. Haptophytes increased before 2017, while West Antarctica continued to see diatom declines after that year.
Diatoms, making up 46% of phytoplankton in the region, are more efficient than smaller nanoplankton such as haptophytes and cryptophytes at locking away carbon, as their silica shells sink with absorbed carbon. They are also the preferred food of krill, which sustain higher predators.
Satellites like Copernicus Sentinel-3 cannot directly detect phytoplankton types but measure subtle changes in ocean colour. These reflect chlorophyll and accessory pigments, which can be linked to species composition using in-situ pigment profiles.
ESA's new Phyto-CCI project will create global phytoplankton type records from space, improving monitoring of marine ecosystem health and the ocean's climate role. Lead author Alexander Hayward warned that fewer diatoms could weaken the biological carbon pump, reducing carbon transfer to the deep ocean.
Research Report:Antarctic phytoplankton communities restructure under shifting sea-ice regimes
Related Links
Space for our climate at ESA
Beyond the Ice Age
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