This International Standard specifies a method for the determination of the inhibition of growth of the macroalga Ceramium tenuicorne by substances and mixtures contained in seawater or by waste water with salinities between 4S and 32S. This method is applicable to substances that are easily soluble in water. NOTE With modifications as described in ISO 14442[4] and ISO 5667-16[2], the inhibitory effects of poorly soluble organic and inorganic materials, volatile compounds, metals, waste water, marine water samples, and elutriates of sediments can be tested