Cultures of Gonyaulax tamarensis were grown on Hastings medium based on 100%, 10%, 1%, 0.1% and 0% (control) of seawater elutrients of bottom sediments. Both "clean" and heavily polluted sediments were used. Very low concentrations of polluted elutrients (0.01% v/v) slightly enhanced the growth of Gonvaulax tamarensis; greater concentrations of polluted elutrient depressed growth. Elutrient from "clean" sediments did not enhance growth; the depression of growth at any given elutrient concentrate was not as great as that seen with the polluted elutrients.