Different responses to high light stress of toxic and non-toxic Microcystis aeruginosa acclimated under two light intensities and zinc concentrations

Abstract

In this study, interaction effects of high light (HL) and zinc on two Microcystis aeruginosa strains (toxic CPCC299 and non-toxic CPCC632) were investigated. Our results suggested that CPCC632 was more sensitive to high zinc (HZn; 7.8 × 10⁻⁶ M) concentration than CPCC299 when acclimated to HL (500 μmol photons m⁻² s⁻¹). When M. aeruginosa strains were treated 20 min to HL (2000 μmol photons m⁻² s⁻¹), the maximal and the operational PSII quantum yields (Φ_M and ) of the two strains decreased, but CPCC632 (50 μmol photons m⁻² s⁻¹ (low light (LL)) + HZn) has the biggest decrease among the four growth conditions. Under LL growth conditions, CPCC632 was more sensitive to HL stress than CPCC299. However, these differences disappeared when they were grown under HL condition. These results suggested that CPCC632 had the lowest ability to acclimate HL stress under LL + HZn conditions. We also showed that the response mechanisms to HL stress of M. aeruginosa were linked to the change of pigments, energy dissipation processes, and microcystin content (for the toxic strain). Our data indicated that different effects of HL and zinc on M. aeruginosa strains may influence the dominance of different strains in aquatic system.

Keywords:

• Microcystis aeruginosa
• high light
• zinc
• photosynthesis

Acknowledgements

Financial support for this study was provided by the Natural Sciences and Engineering Research Council of Canada (NSERC) (to Philippe Juneau) and Kui Xu received a scholarship from the China Scholarship Council (CSC).