In 2023, 22% of the world’s ocean surface experienced at least one severe or extreme marine heatwave. Increasingly frequent and intense, each one of them upsets the balance of the oceans. By disrupting the spring bloom of phytoplankton, they weaken the marine food chain and compromise the oceans’ ability to capture carbon. These disturbances directly threaten biodiversity and amplify the global climate crisis.
by Laurie Henry
Cover photo: Whirlpools of proliferating algae in the northern Adriatic Sea, along the Italian coast. © ESA
In the north-western Mediterranean, the sea temperature continues to break seasonal records, revealing a phenomenon that is part of a global climate trend. This warming is not limited to the surface since it modifies the very structure of the water column, disrupting the natural mechanisms that allow marine productivity.
To understand how these thermal anomalies affect ocean biology, a team of researchers from the Italian National Research Council (CNR-ISMAR), East China Normal University and Mercator Ocean International has been studying the effects of winter marine heatwaves. Conducted as part of the European CAREHeat project and published in 2024 in Geophysical Research Letters, this study uses satellite observations, BGC-Argo floats and digital models to assess the impact of these episodes on the spring bloom of phytoplankton, a central link in marine ecosystems.