Interactions between Two Species of Marine Bloom Microalgae (Heterosigma akashiwo Hada and Karenia mikimotoi Hansen) and Their Response to UV-B Radiation

In the role of UV-B radiation, using the method of co-culture, by measuring the number of algal cells to study UV-B radiation on different initial concentrations of Karenia mikimotoi Hansen and Heterosigma akashiwo Hada affect interspecific competition between the two red tide algaes. The results demonstrated the different inoculative proportions of K. mikimotoi and H. akashiwo ap- parent effects on interspecific competition between them. When the inoculative proportion of K. mikimotoi and H. akashiwo was 4:1 and 1:1, K. mikimotoi would be in predominance in the compe- tition. However, H. akashiwo would be absolute advantage in the competition when K:H was 1:4. The UV-B radiation could change the competition relationship between K. mikimotoi and H. aka- shiwo. But both of the population densities were decreased. When K:H was 1:1, H. akashiwo was in predominance and the competition of the other two groups was unchanged. In conclusion, UV-B radiation plays an important effect on the competition between both of the microalgae, it could offer powerful basis for researching how UV-B radiation to effect red tide.