Algae. 2001; 16(1): 67-73.

Control of Harmful Algal Blooms by Clay via Photochemical Reactions

Chang Sook Kim, Heon Meen Bae, Yong Chul Cho

Harmful algal Blooms Research Division, National Fisheries Research and Develoment Institute

In an attempt to improve the removal efficiency of natural clay to red tide dinoflagellates, Cochlodinium polykrikoides and Prorocentrum micans, the synergistic effect of clay plus light was investigated. The removal capacity of dinoflagellates by clay via photochemical reactions was increased to about 20% of the dark control values. Light induced effect began to be occurred when the light intensities above about 2,300 μmol m super(-2)?S super(-1). The capacity of clay plus light to removal the C. polykrikoides was related to the concentration of TiO sub(2) in caly: the higher the content of TiO sub(2), the higher the removal rates. Particularly, when the C. polykrikoides treated with TiO sub(2) or rose bengal were subjected to UV-A (600 μmol?m super(-2)?s super(-1)) or white light (λ>320 nm; 1,400 μmol?m super(-2)?s super(-1)) for 10 min under aerobic conditions, the algal cell was severely damaged with the membrane lysis. The suspension of clay, when exposed to white light, generate reactive oxygen species (ROS) such as singlet oxygen (super(1) O sub(2)), as measured by the imidazole plus RNO method. These data show that the ROS, photogenerated from clay, -mediated oxidative damages are enhanced the original effect of clay to algal species. These results suggest that the removal efficiency of red tide dinoflagellates by clay under bright sunlight is higher than that of a cloudy day.

Keywords : clay, photochemical reaction, reactive oxygen species, red tide dinoflagellates