Abstract
Effects of marine aluminum (Al) on phytoplankton are controversial, making it important to elucidate the mechanisms underlying Al effects. This study was aimed at identifying the effects of Al on the growth, chlorophyll a (chl a) content and the antioxidant mechanism of cyanobacteria Synechococcus sp. WH7803. The growth rate increased from 0.33 to 0.52 d-1 in media with the increasing Al concentration from 0.2 (control) to 20 μmol l-1 and almost saturated to 0.44 d-1 at ~ 0.5 μmol Al l-1. The higher growth resulted in the higher biomass in both stationary and decay phases in the conditions of higher Al content. Chl a per cell reached 10.19 μg cell-1 in the exponential phase at 20 μmol Al l-1, approximately 1.6 and 3.1 times higher than those in stationary and decay phases, respectively, and chl a per cell showed a similar pattern as a growth rate when plotted with Al content. Al addition increased the cellular methane dicarboxylic aldehyde (MDA) content in the exponential phase and decreased the superoxide dismutase (SOD) activity in the decay phase. In particular, our results indicated a positive relationship between chl a per cell and the growth rate, suggesting the stimulation of increasing Al on the growth of Synechococcus is related to the enhancement of cellular chl a content.