Phytoplankton blooms are one of the most important factors contributing to the efficiency of the carbon pump in the North Atlantic Ocean. To better understand this phenomenon, the ERC remOcean project, led by researchers at the Laboratoire d”Océanographie de Villefranche (CNRS/UPMC), has developed a new class of robots: biogeochemical profiling floats, the first robots able to collect data in the ocean throughout the year. Using these unparalleled data, the researchers have identified the starting point for the explosive spring phytoplankton bloom. Their results are the subject of two articles published in Nature Geoscience and Nature Communications.