15 août 2025
Space-based monitoring uncovers climate-driven Antarctic plankton transformation
Diatom decline and surge in smaller species threatens Antarctic food web and carbon storage
Scientists have uncovered a climate-driven shift of Antarctic phytoplankton that underpins Antarctica's marine ecosystem, revealing how climate change is reshaping the Southern Ocean from the bottom up. The research team used 25 years of satellite observations of sea surface temperature, ocean colour and sea-ice extent (between 1997 and 2023), plus over 14,000 in-situ ocean samples, to train machine-learning models. These models were then used to map changes in the key plankton groups. Based on this, researchers discovered that diatoms – the large, silica-shelled algae that feed krill and efficiently store carbon – have declined significantly across Antarctica's continental shelf, while smaller phytoplankton groups have surged.
A shift occurred after 2016, coinciding with sea ice loss, when these smaller phytoplankton groups rapidly proliferated while diatoms began a modest recovery. These changes threaten to disrupt the krill-centered food web that supports whales, penguins, and seals, while potentially weakening the Southern Ocean's role as a global carbon sink. “If we observe a decrease in the number of diatoms, it is likely that the biological carbon pump will weaken, resulting in less carbon dioxide being transported to the deep sea. Now more than ever, we need more research and observation to monitor the changes in this sensitive ecosystem. What’s happening at the microscopic level could impact the climate itself and needs our attention,” says Alexander Hayward, Earth System Scientist at the Danish Meteorological Institute.
Climate Change Initiative enables long-term monitoring and new insights
Although vital to Earth’s climate, long-term changes in phytoplankton communities are poorly understood. Recognising this, the Global Climate Observing System (GCOS) has designated phytoplankton species composition as a new Essential Climate Variable. In response, ESA launched the PHYTOplankton biomass and diversity Climate Change Initiative (PHYTO-CCI) project to generate global records of phytoplankton types from space using advanced analysis of satellite-detected pigments. PHYTO-CCI will equip scientists to better monitor marine ecosystem health and the ocean’s role in climate regulation.
Read the full article and learn more about the paper's findings: https://www.esa.int/Applications/Observing_the_Earth/Space_for_our_climate/Tracking_the_climate-driven_shift_in_Antarctic_plankton_from_space