Cite this paper:
Zengling MA, Xiaoqiao ZHANG, Renhui LI, Min WANG, Wenli QIN, He ZHANG, Gang LI, Henguo YU, Chuanjun DAI, Min ZHAO. Competitiveness of alga Microcystis aeruginosa co-cultivated with cyanobacterium Raphidiopsis raciborskii confirms its dominating position[J]. Journal of Oceanology and Limnology, 2022, 40(5): 1804-1818

Competitiveness of alga Microcystis aeruginosa co-cultivated with cyanobacterium Raphidiopsis raciborskii confirms its dominating position

Zengling MA1,2, Xiaoqiao ZHANG1,2, Renhui LI1,2, Min WANG1,2, Wenli QIN1,2, He ZHANG1,2, Gang LI3, Henguo YU1,2, Chuanjun DAI1,2, Min ZHAO1,2
1 Zhejiang Provincial Key Laboratory for Subtropical Water Environment and Marine Biological Resources Protection, Wenzhou University, Wenzhou 325035, China;
2 National and Local Joint Engineering Research Center of Ecological Treatment Technology for Urban Water Pollution, Wenzhou University, Wenzhou 325035, China;
3 Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China
Microcystis aeruginosa has always been regarded as the main culprit of cyanobacterial blooms in freshwater. However, in recent years, Raphidiopsis raciborskii has gradually replaced M. aeruginosa as the culprit of cyanobacterial blooms in some tropical and subtropical shallow lakes. To reveal which one plays a more dominant role, interactions between cylindrospermospin (CYN)-producing R. raciborskii and microcystins (MCs)-producing or non-MCs-producing M. aeruginosa strains were studied using bialgal cultures at different initial ratios of biomasses of the two species at 25 �C. During the co-cultivation, the M. aeruginosa strains inhibited the growth and heterocyst formation of R. raciborskii filaments, and thus occupied a dominant position during the co-cultivation regardless of the initial biomass ratios in the cultures. In addition, the MCs-producing M. aeruginosa strain contributed to a higher portion of the total biomass and exerted a stronger inhibitory effect on R. raciborskii compared with the non-MCs-producing strain. However, the growth of both MCs-producing and non-MCs-producing M. aeruginosa strains was stimulated by R. raciborskii in the co-cultures compared with M. aeruginosa monoculture, indicating that M. aeruginosa could outcompete R. raciborskii if given enough time, enabling it to develop into the dominant species even in very low initial concentration. To our best knowledge, this is the first report on the loss of heterocyst formation by a species of cyanobacteria that resulted from interactions between two different species of cyanobacteria. These findings indicate that it is difficult for R. raciborskii to replace the dominant position of M. aeruginosa under the experimental environmental condition, and the allelopathic effects of M. aeruginosa on R. raciborskii could significantly contribute to the success of M. aeruginosa.
Key words:    competition    growth    heterocyst    Microcystis aeruginosa    morphology    Raphidiopsis raciborskii   
Received: 2021-11-18   Revised: 2022-01-07
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