Macroalgal growth inhibition assay for screening coastal water pollution

Chemicals from past and present maritime activities and land effluents pollute coastal areas. Cybutryne, a banned antifoulants, has been reported to persist in the environment. Diuron is banned in Europe, but in Japan itâ��s still used with Cu₂O in ship hullsâ�� paints. These substances are persistent, and even cybutryne, may remain for extended period of time and potentially affect organisms. Algae are relatively sensitive to antifoulants, making screening evaluations using algae suitable for assessing seawater pollution. However, it remains unclear which species are suitable for screening test organism. Therefore, this study aims to develop a screening method using highly sensitive macroalgae by comparing the sensitivity of multiple macroalgal species. The toxicity of Cu, diuron, and cybutryne to 25 strains was evaluated, and Planosiphon zosterifolius (KU-0856) showed a relatively high specific growth rate (SGR, 0.11â��0.16/day) and was sensitive to all three antifoulants. This test method, which uses the SGR calculated from in vivo chlorophyll (measured by a microplate reader) as an endpoint, is simpler than the standardized test method. Furthermore, P. zosterifolius is more sensitive than Ceramium tenuicorne , which is designated as a test organism in ISO 10710. Therefore, this test method surpasses the standardized test method in terms of experimental simplicity and sensitivity, and can be used for screening coastal water polluted by the antifoulants. The 5 hazardous concentrations for 25 macroalgae were 0.16, 0.81, and 7.2 µg/L for cybutryne, diuron, and Cu, respectively, and these values can be used for future risk assessment. © 2026 Elsevier B.V.