Phytotoxicity of the New Antifouling Compound Irgarol 1051 and a Major Degradation Product

Abstract

The phytotoxicity of the new antifouling compound Irgarol 1051 (2-methylthio-4- tert-butylamino-6-cyclopropylamino- s-triazine) and its degradation product M1 (2-methylthio-4- tert-butylamino-6-amino- s-triazine) was assessed by a battery of bioassays with marine and freshwater species. Both compounds at low concentrations affected aquatic plant species such as the red macroalga Porphyra yezoensis conchospores, the brown macroalga Eisenia bicyclis gametophytes, the freshwater green microalga Closterium ehrenbergii, the floating macrophytes Lemna gibba G3 and Lemna minor 1769. The toxicity of Irgarol 1051 was higher than that of M1 for all the aquatic plant species tested, but M1 showed a higher toxicity to root elongation of a terrestrial plant. The NOEC (0.3 μg/ l) of Irgarol to the brown seaweed was identical to the maximum concentration (0.296 μg/ l) detected in Japanese coastal waters, and the maximum concentration of M1 (1.87 μg/ l) detected amounted to only 20% of the NOEC value. The bioassay results suggest the possibility that both Irgarol 1051 and M1 may influence the primary producer community in the aquatic environment.