The Interspecific Competition And Allelopathic Interaction Between Karenia Mikimotoi And Dunaliella Salina In Laboratory Cultures

Algal allelopathy is a manifold ecological/physiological phenomenon that focused on chemical interactions and autotoxicity. It is also an adaptive mechanism for environment stresses and competition between different species.We investigated the interspecific competition and allelopathic interactions between Karenia mikimotoi and Dunaliella salina in laboratory cultures based on different temperature (15℃,20℃,25℃) and lighting (40μmol/(m2·s),80 μmol/(m2 s),160μmol/(m2·s)) conditions. The growth of D. salina in bi-algae culture (1:1 size/density) was significantly restrained. Results of cell-free filtrate culture indicated that direct cell-to-cell contact was not necessary in interspecific competition. Further experimental results showed allelochemicals released from K. mikimotoi were markedly influenced by both temperature (P=0.013) and irradiance (P=0.003), causing different growth characteristics of D. salina in filtrate mediums. Compared with plateau period, K. mikimotoi exudates in exponential phase had a stronger short-term inhibition effect on D. salina at normal condition. A clear concentration-dependent relationship was observed in the effect of allelochemicals released from K. mikimotoi, with low-promoting and high-repressing to D. Salina in a short time-scale. In addition, allelopathic substances still keep stable and effective under high temperature and pressure stress. Much flocculent sediments adhered with D. salina cells, was found in all filtrate mediums, while the quantity and colour depended on original culture conditions. In conclusion, this paper provides theoretical basis to deeply research the allelopathy between those microalgae.