DYPHYRAD data are acquired using a semi-automated approach along a coastal-offshore transect in the eastern English Channel, off the Slack estuary (northern limit of the Marine Protected Area of Picard Estuaries and Opal seas EPMO) by the Strait of Dover (Pas de Calais), at fine spatial resolution (9 stations at ∼1 km interval). Phytoplankton functional groups are characterized in sub-surface waters, both by multispectral fluorometry (Fluoroprobe, bbe Moldaenke, Gmbh) and at single-cell level using an automated flow cytometer (CytoSense/CytoSub, Cytobuoy b.v., Netherlands). Total phytoplankton biomass is estimated by chlorophyll a extraction and in vivo fluorescence. Spectral groups, abundance, size and total chlorophyll a of phytoplankton functional groups were estimated in surface waters, along with biogeochemical and hydrological variables such as temperature, salinity, water column, PAR and nutrients (nitrate, nitrite, phosphate, silicate).