Abstract

Karenia mikimotoi bloom is known to damage abalones via chemical toxicity, but the toxic mechanism remains unclear. In an attempt to gain an insight into its damage potential to abalone spats Haliotis discus hannai, the spats were exposed to 0, 10, 50, or 100% of $7,500cells\;ml^{-1}$ K. mikimotoi in types of ICS (intact cell suspension), BCS (broken cell suspension) or CFE (cell-free elutriate) at 13 and $18^{\circ}C$, respectively. The spats were also exposed to corresponding type and dilution of $7,500cells\;ml^{-1}$ Cochlodinium polykrikoides and $2,000cells\.ml^{-1}$ Alexandrium affine which were equivalent to $7,500cells\;ml^{-1}$ K. mikimotoi on the basis of TOC (total organic carbon). K. mikimotoi was proved to be damageable to the spats with damage potential not bigger than A. affine and C. polykrikoides. In algal type, ICS was most influential, particularly in lower dilutions (with an occasional significance of p < 0.01 or p < 0.05), suggesting that toxicity potential might be more associated with intact cell membrane. Overall, the spat damages of experimental trials were in concurrence with those of controls which were solely due to culture stress, suggesting that the culture stress might be an additional parameter influencing the spat damage and thus should be countered into consideration in future study.