Subsurface Phytoplankton Responses to Ocean Eddies Can Run Counter to Satellite-Based Inference from Surface Properties in Subtropical Gyres

•A cyclonic and an anticyclonic eddy were simultaneously tracked by two biogeochemical-Argo floats for 3 months in the South Indian Ocean.•A spring subsurface phytoplankton bloom with a reduction in surface chlorophyll is detected in the cyclonic eddy.•A subsurface chlorophyll maximum layer with vertically homogenized phytoplankton is observed in the anticyclonic eddy in the spring.•The anticyclonic eddy exhibited higher surface chlorophyll than the cyclonic eddy and lower subsurface phytoplankton biomass and productivity.•Similar biological responses to eddy perturbations are observed in a global analysis.