Effects of Antifouling Compounds on the Growth of Macroalgae Undaria Pinnatifida

Seaweeds are some of the principal primary producers of marine environments, and they are important ecological elements of coastal ecosystems. Therefore, the effects of harmful chemicals on seaweeds may adversely affect coastal ecosystems. In this study, we aimed to develop a standardized phytotoxicity test using the gametophytes of a common temperate kelp species, Undaria pinnatifida (KU-1630). Test chemical substances were Cybutryne, Diuron, Cu²⁺, and Zn²⁺, which are widely used as ship bottom antifouling agents. Toxicity to gametophytes of U. pinnatifida was assessed by comparing the relative growth rate (RGR) at the logarithmic growth phase. Fragmentation method, initial algal biomass, photon irradiance, and adhesive period were investigated for developing optimal test conditions. Cybutryne exposure tests were performed at 7 repeats, with control RGR ranging from 0.17 to 0.19, while mean 7-day EC 50 and no observed effect concentration (NOEC) were 5.1 µg/L and 1.8 µg/L, respectively. The 7-day EC 50 for other chemicals was 14 µg/L for Diuron, 17 µg/L for Cu²⁺, and 1500 µg/L for Zn²⁺. This test method demonstrated high sensitivity and reproducibility and it may be added to the methods routinely used for toxicity evaluation of hazardous chemicals.