. Abstract: The liquid eftluent from an oil maritime terminal, with produced water as the main component, had its toxicity evaluated through toxicity tests with the diatom Skeletonema costatum. Two previously treated eftluent samples (eftluents A and B), were provided by PETROBRAS for the experiments. Both samples presented high salinity (67%0for eftluent A and 62%0for eftluent B) and low pH va...