Abstract: A method for producing biomass from a microalgae includes culturing the microalgae in an effluent diluted in seawater. A method for bioremediating an effluent includes culturing a microalgae in the effluent diluted in seawater. The microalgae is at least one of a strain of the genus Nodularia, a strain of the genus Chrysoreinhardia, a strain of the genus Halochlorella, or combinations thereof. At the beginning of culturing, the diluted effluent exhibits concentrations of total nitrogen (N) in the range of 30-150 mg/l and concentrations of total phosphorus (P) in the range of 1-15 mg/l. The N/P quotient is in the range of 5-40.