Dissolved Free Amino Acids (DFAA) concentra tions were measured in the water column during a night and day sampling period, following a Lagrangian drogue within Concepción Bay (Chile). For the night-time sampling period no correlations between DFAA and either chlorophyll-fl or zooplankton were observed, although a positive and significant correlation between phytoplankton and zooplankton biomass did exist. During the day chlorophyll-fl and DFAA were correlated throughout the water column, suggesting that excretion, enhanced by photosynthetic activity of primary producers was occurring.