Effects of temperature fluctuation on the development of cyanobacterial dominance in spring: implication of future climate change

Abstract

Global warming is predicted to increase the intensity and frequency of short-term temperature fluctuation. However, the effect of temperature fluctuation on phytoplankton is rarely considered. We analyzed the effect of fluctuating temperature on cyanobacterial dominance and blooms in spring (March–May) with long-term data analyses, laboratory simulation, and field observation. Our results showed that the magnitude of air temperature fluctuation in spring has increased in Lake Taihu over the past 58 years (1956–2013) and was negatively correlated with cyanobacterial blooms onset time (1987–2013). Air temperature fluctuation was one of the predictors of the best model for the variability in the bloom size in spring (2000–2011). The results from the field observation (2009–2013) also indicated that there was a positive correlation between diel air temperature difference and the ratio of cyanobacteria to total algae. Laboratory experiments suggested that water temperature fluctuation slowed the growth rates of Chlorella pyrenoidosa and Cyclotella meneghiniana but not Microcystis aeruginosa, which confirmed our findings of field observation and long-term data analysis. Therefore, the increased temperature fluctuation under global warming may promote cyanobacterial dominance. Our findings provide further understanding of inter-annual difference of cyanobacterial blooms onset time in the warming world.