A team from the Physical Oceanography section of the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), led by Hongyan Xi, contributed to the recently published 9th Copernicus Ocean State Report. Coordinated by Mercator Ocean International on behalf of the European Commission, the report summarizes the latest developments in global and European ocean monitoring.
In their contribution, the AWI researchers highlight the key achievements of the Copernicus Marine Service Evolution project GLOPHYTS (2022–2024), which also lays the groundwork for their ongoing project “ML-PhyTAO” (2024–2026). Both projects aim to establish a consistent, long-term monitoring framework for phytoplankton groups, with the former on the global scale and the latter tailored to the Arctic Ocean using improved AI-based retrieval algorithm. The group had also previously contributed preliminary results from the GLOPHYTS project to the 7th Copernicus Ocean State Report (OSR7), presenting long-term trends in phytoplankton composition in the Atlantic Ocean.
Phytoplankton are microscopic organisms inhabiting the sunlit surface layers of the ocean. They form the foundation of marine food webs and drive essential biogeochemical cycles. In OSR9 chapter 2.4, the AWI team investigated the five major phytoplankton groups diatoms, haptophytes, prokaryotes, chlorophytes, and dinoflagellates, using long-term, inter-sensor consistent satellite data corrected with a machine learning scheme developed at AWI in collaboration with ACRI-ST (France). Their time series analysis revealed increasing global trends for diatoms and dinoflagellates and decreasing trends for haptophytes and prokaryotic phytoplankton. Chlorophytes remain relatively stable with regional variations. The trends of these phytoplankton groups are most pronounced in high latitudes and coastal zones. For prokaryotes, they are also evident in the equatorial region.
‘The Copernicus Ocean State Report is an ideal platform on which to share our latest progress in observing global phytoplankton from space using optical satellites,’ says Hongyan Xi. ‘Machine learning is a powerful technique that can further improve the quality and consistency of ocean colour data, supporting assessments of ocean health and ecosystem change.
By combining satellite observations with advanced data analysis, the AWI team is contributing to the long-term monitoring of marine ecosystems and the ongoing development of the Copernicus Marine Service.
The study was conducted by Hongyan Xi, Astrid Bracher and Ehsan Mehdipour from the AWI’s Physical Oceanography section, together with Marine Bretagnon, Julien Demaria and Antoine Mangin from ACRI-ST in France.
Link to the study: https://sp.copernicus.org/articles/6-osr9/