不同起始密度对3种赤潮微藻种间竞争的影响

The effect of initial cell density on the interspecific competition between three species of red tide microalgae

通过共培养的方法,研究了不同起始密度对赤潮异弯藻和中肋骨条藻、塔玛亚历山大藻和赤潮异弯藻、塔玛亚历山大藻和中肋骨条藻之间种间竞争的影响。结果表明1赤潮异弯藻对中肋骨条藻的生长有一定的抑制作用,随着初始接种时赤潮异弯藻细胞密度的提高,这种抑制作用愈加明显。2塔玛亚历山大藻和中肋骨条藻与塔玛亚历山大藻和赤潮异弯藻之间的种间竞争结果相类似,即起始密度比例为A∶S(H)=1∶4时,中肋骨条藻和赤潮异弯藻分别在竞争中占优势;当起始密度比例为A∶S(H)=1∶1和A∶S(H)=4∶1,塔玛亚历山大藻在竞争中占优势。

Red tides is a ubiquitous and natural phenomenon caused by the excessive growth of phytoplankton. It has caused serious social problems and heavy damage to fisheries worldwide. Therefore, this has become a major environmental issue in the world. The red tide occurrence can be affected by the effects of the initial cell density on the interspecific competition between different species of red tide microalgae. However, few studies have been focused on the interspecific competition between different microalgae species. In this paper, three red tide microalgae, Alexandrium tamarense, Skeletonema costatum and Heterosigma akashiwo were used. We investigated the effect of initial cell density on the interspecific competition between them by a mixed culture method. Cultures were grown at (19±1) ℃ under a 12/12 dark/light cycle of 3000lx illumination in f/2 culture medium. Cells were counted on under the microscope after it was fixed by Lugol liquid every two days. The results showed that H. akashiwo inhibited the growth of S. costatum, and the inhibition was more obvious with the promoting of inoculation proportions of H. akashiwo and S. costatum. When the inoculation proportions of A. tamarense and H. akashiwo (A∶H) was 1∶4, H. akashiwo was in predominance in this competition. On the contrary, A. tamarense was in predominance when A∶H = 1∶1 and A∶H = 4∶1. The result on the competition between A. tamarense and S. costatum was similar to that between A. tamarense and H. akashiwo. In conclusion, our results showed that the effect of initial cell density on the interspecific competition between different species of red tide microalgae was a very important factor in red tide occurrence. Not only the consummation of nutritional sources but also the interaction could notably affect the interspecific competition. We suggested that the inhibition of H. akashiwo on the growth of S. costatum and A. tamarense was due to the direct contact of cells, while the inhibition of A. tamarense on the growth of S. costatum and H. akashiwo was caused by the indirect contact of cells. The inhibition of S. costatum on the growth of A. tamarense and H. akashiwo need to be further determined.