Abstract: As ubiquitous features in the oceans, mesoscale eddies play a significant role in supplying the nutrients required for phytoplankton blooms and redistributing biomass in the ocean. However, how eddies influence nutrient flux and biomass distribution remains unclear. Two important dynamical processes (radial displacement and vertical fluctuations) within an anticyclonic eddy are revealed from Argo floats' observations. The Argo floats in the eddy were displaced toward the eddy edge due to the imbalance of radial momentum. Vertical fluctuations below the mixed layer resulted in alternating upwelling and downwelling in the inner and outer parts of the eddy. These processes represent crucial dynamical mechanisms for the motion of particles in mature anticyclonic eddies.