Environmental factors influence cylindrospermopsin production of Cylindrospermopsis raciborskii (CR12)

Cylindrospermopsis raciborskii is a closely monitored freshwater cyanobacterial species due to its potential to produce cylindrospermopsin (CYN). The existence of multiple strains with varying levels of toxicities necessitates further studies from different regions to compare their physiological responses and acclimation to different environments. This is the first study that examines the growth and CYN production of an equatorial strain. A Singaporean strain, CR12, was cultured in three batch culture experiments under a range of phosphorus, temperature and light conditions. Growth rates ranged from 0.299 to 0.591 day(-1), with the maximum observed at the highest light intensity (86.1 mol m(-2) s(-1)). Optimal growth temperature was at 33 degrees C, higher than most strains previously studied. The CYN cell quota of the CR12 strain was 100 times lower than Australian strains. A significant non-linear relationship was observed between net cellular CYN production rate and growth rate, with maximum net CYN production rate occurring when the growth rate was 0.37 day(-1). This study highlights the differences in growth and net CYN production of an equatorial strain compared with other previously studied strains. Optimal growth conditions, which occur throughout the year in equatorial regions, can potentially result in prolonged blooms and substantial CYN accumulation.