赤潮异弯藻(Heterosigma akashiwo)对蒙古裸腹溞(Moina mongolica)和日本新糠虾(Neomysis japonica)的毒性影响

Zooplankton is an important link between phytoplankton and higher consumers in the marine food chain. Experiments were designed to investigate the harmful effects of Heterosigma akashiwo on Moina mongolica and Neomysis japonica under laboratory conditions. The results show that, after 96h, the survival rate of M. mongolica exposed to 1×10^4, 5×10^4, 10×10^4, and 20×10^4cells/ml of H. akashiwo is 10%, 23.3%, 21.67% and 0%, respectively, significantly lower than that of the control (98.4%);while the survival rates of N. japonica exposed to 1×10^4, 5×10^4, and 10×10^4cells/ml of H. akashiwo are 33.3%, 27.8%, and 33.7%, respectively, obviously lower than that of the control at 66.7%. The harmful effect of 2×10^4, 4×10^4 cells/ml of H. akashiwo on M. mongolica is as follows, (1) the body length of M. mongolica was reduced slightly to 1.44 mm and 1.37 mm after 13 days, respectively, while that of the control was 1.46 mm; (2) the development was delayed, as the time for the first brood of M. mongolica was 4.0 and 4.1d, while that in of control was 3.7d; (3) the gross fecundity was decreased to 30.2, and 26.7, respectively, and that in control was 35.5; (4) the average life-time was shortened to 11.4 and 12.5d, respectively, and that of control was 14.5d. Moreover, H. akashiwo inhibited obviously the population dynamics of M. mongolia, as the population number of M. mongolia exposed to 2×10^4cells/ml and 5×10^4 cells/ml of H. akashiwo was 36.5% and 0% of the control after 17 days, respectively. Microscope observation shows, M. mongolica could feed on H. akashiwo filled with in intestinal tract; however, it seemed that M. mongolica could not digest very well, and H. akashiwo could excrete some materials to stick on the intestinal tract end of M. mongolica; moreover, H. akashiwo also stuck to the setae of N. japonica. Thus, H. akashiwo can disturb normal activities of the zooplankton, and cause them death rapidly.