Enhanced species-specific chemical control of red tide organism by the thiazolidinedione derivative TD49

Abstract

Culture experiments involving 23 algal strains were conducted to evaluate the algicidal effects of a newly developed algicidal thiazolidinedione derivative (TD49) on non-harmful and harmful algal bloom (HAB) species. We also assessed the effect of various concentrations of TD49 on various growth phases (lag, logarithmic and stationary) of the harmful algae Heterocapsa circularisquama (Dinophyceae) and Heterosigma akashiwo (Raphidophyceae), and the non-harmful diatoms Skeletonema costatum and Chaetoceros didymus. The inhibitory ratios (%) for H. circularisquama and H. akashiwo at 2.0 &micro M TD49 were significantly higher than at other concentrations, and the inhibitory ratio varied depending on growth phase and species as follows: logarithmic ≥ stationary > lag phase for H. circularisquama, and logarithmic ≥ lag > stationary phase for H. akashiwo. Although the inhibitory ratios for C. didymus were similar to those for the two harmful algae (H. circularisquama and H. akashiwo), inhibitory effects on S. costatum were not apparent at > 2.0 &micro M in any growth phase. The algicidal activity of TD49 on the harmful and non-harmful algae was: unarmored HAB species > armored HAB species > diatom species > cryptophyte species. TD49 was algicidal to most HABs but had little inhibitory effect on some non-harmful algae, implying that TD49 has selective algicidal activity. Our results indicate that TD49 is potentially of usefect of various concentrations of TD49 on various growth phases (lag, logarithmic and stationary) of the harmful algae Heterocapsa circularisquama (Dinophyceae) and Heterosigma akashiwo (Raphidophyceae), and the non-harmful diatoms Skeletonema costatum and Chaetoceros didymus. The inhibitory ratios (%) for H. circularisquama and H. akashiwo at 2.0 &micro M TD49 were significantly higher than at other concentrations, and the inhibitory ratio varied depending on growth phase and species as follows: logarithmic ≥ stationary > lag phase for H. circularisquama, and logarithmic ≥ lag > stationary phase for H. akashiwo. Although the inhibitory ratios for C. didymus were similar to those for the two harmful algae (H. circularisquama and H. akashiwo), inhibitory effects on S. costatum were not apparent at > 2.0 &micro M in any growth phase. The algicidal activity of TD49 on the harmful and non-harmful algae was: unarmored HAB species > armored HAB species > diatom species > cryptophyte species. TD49 was algicidal to most HABs but had little inhibitory effect on some non-harmful algae, implying that TD49 has selective algicidal activity. Our results indicate that TD49 is potentially of use