ALLELOPATHIC EFFECTS OF Prorocentrum donghaiense AND Karenia mikimotoi ON EACH OTHER UNDER DIFFERENT TEMPERATURE

Allelopathic effects of Prorocentrum donghaiense and Karenia mikimotoi, which are the main dinoflagellates bloom species, were investigated by using cell-free filtrate of algal culture experiments on each other under different temperatures with several combinations of initial cell densities. The growth of P donghaiense was dramatically suppressed in the K. mikimotoi culture filtrate at these initial cell densities at 16 degrees C, 20 degrees C, 24 degrees C and 28 degrees C compared with the control and the inhibitory effect of K. mikimotoi culture filtrate on the growth of P donghaiense was ordered as 16 degrees C > 20 degrees C > 24 degrees C > 28 degrees C; the growth of K. mikimotoi was suppressed in the P donghaiense culture filtrate with the highest initial cell density under four tempeartures compared with the control, and the inhibitory effect of P donghaiense culture filtrate on the growth of K. mikimotoi was ordered as 16 degrees C > 20 degrees C > 28 degrees C > 24 degrees C, while the inhibitory effect of P donghaiense culture filtrate was smaller with middle initial cell density at 20 degrees C, 24 degrees C and 28 degrees C. Besides, there was little inhibitory effect even the stimulating effect at some treatment groups when the initial cell density was low. The results indicated that the allelochemicals released by K. mikimotoi was heat-sensitive and P donghaiense was not heat-sensitive. The results also showed that the culture temperature and the initial cell density play key roles in allelopathic effects of P donghaiense and K. mikimotoi.