1] Eulerian and Lagrangian characteristics of simultaneously recorded temperature, salinity and phytoplankton biomass time series are investigated over a seasonal cycle. Time series are analyzed in the spectral and multifractal scaling frameworks. We show that passive scalar time series (temperature and salinity) are characterized by scaling laws representative of Eulerian and Lagrangian turbulence. The two different regimes identified are separated by a transition linked to the characteristic scale of turbulent structures of the same size as the boat. While the scaling behavior exhibited by phytoplankton biomass fluctuations is close to the expected passive scalar behavior over Eulerian scales, it is quite far from it over Lagrangian scales. For these scales, the observed scaling behavior exhibits a significant density-dependence, indicative of biological activity.