Effect of light and temperature on the population dynamics of two toxic bloom forming Cyanobacteria – Microcystis ichthyoblabe and Anabaena aphanizomenoides

Abstract

The effect of light and temperature on the growth of Microcystis ichthyoblabe and Anabaena aphanizomenoides, isolated from the subtropical Oued Mellah lake, Morocco (33°30′N–07°20′W), were investigated in batch culture. Growth rates at 66 light–temperature combinations were determined and fitted with different mathematical models. The results show that the two Cyanobacteria grow at all light intensities and temperatures, except at 10 °C for A. aphanizomenoides, where the growth was strongly limited. The μ_max of M. ichthyoblabe increased with temperature from 0.56 d⁻¹ at 10 °C to 1.32 d⁻¹ at 35 °C. At all tested temperatures, a relative photoinhibition within the studied range of irradiance was observed and the photosensitivity was thermodependent. For Anabaena, the obtained μ_max ranged between 0.07 d⁻¹ at 10 °C and 1.46 d⁻¹ at 35 °C, and a weak photoinhibition was observed at 15 °C. The positive correlation between μ_max and I_opt (r²≥0.93) indicates a close interaction between light and temperature on the cyanobacteria growth. The results obtained in this work suggest that the growth of these two species is possible under low light and low temperature.

Keywords:

• Cyanobacteria
• Microcystis ichthyoblabe
• Anabaena aphanizomenoides
• light–temperature interaction
• ecophysiology

Acknowledgements

This work was supported by the projects PARS 189 Biology and PROTARS P1T1/36. We acknowledge the critical analyses of two anonymous reviewers.