This dataset includes measured and calculated data over the epipelagic layer (0-200 m depth) of 25 stations with 14 of them inside or in the vicinity of a cyclonic eddy that formed off Mauritania along the ∼ 900 km zonal corridor between Mauritania and the Cabo Verde islands in the eastern Tropical North Atlantic during the M156 cruise on the RV Meteor from July 3rd to August 1st 2019. Mixed layer depth and surface chlorophyll-a concentrations are shown.