LAUSR

Abstract The interspecific competition among algal species is an important process that can change the community structure in aquatic ecosystems. However, there is still a lack of understanding of the impact of various factors on interspecific competition. In this study, both experimental and mathematical modeling approaches were employed to investigate how various combinations of the initial cell densities of Pseudokirchneriella subcapitata and Chlorella vulgaris and copper exposure levels affect interspecific competition between these species. In the simulation results, C. vulgaris appeared to be superior to P. subcapitata in the absence of copper exposure. However, in the copper-exposed groups, the competitive positions of both algal species varied with the initial cell density and the copper exposure level. In particular, at the highest copper concentration (10 μg/L), C. vulgaris became less competitive than P. subcapitata in most initial cell density combinations, resulting in a shift in competitive dominance. This study clearly showed that the dominant species in the interspecific competition could be altered by the two factors studied herein. The developed model provided a more detailed and intuitive understanding of the effects of the two factors on the interspecific competition by simulating the competition at various combinations of initial algal density and copper exposure levels. In this study, the initial algal density and copper exposure levels were selected as the factors influencing the interspecific competition between P. subcapitata and C. vulgaris, but the proposed model could be used to study the effects of other toxicants on the interspecific competition between other algal species.