Potential maximum quantum yield of photosystem II reflects the growth rate of Chattonella marina in field bloom samples

Time series variations in the potential maximum quantum yield of photosystem II (F_v/F_m ratio) and growth rate of field Chattonella marina cells were investigated during a HAB occurred in the inner part of Ariake Sea, Japan (5-14 September, 2012). This study aimed at investigating the usability of Fv/Fm ratio in evaluating the growth of C. marina and its HAB dynamic under natural conditions, by analyzing its correlations with algal growth rate and various environmental variables. Field observation showed that exhaustion of dissolved inorganic nitrogen (DIN) was likely responsible for controlling the growth of C. marina cells and finally induced the bloom termination. As the bloom progressed, both the F_v/F_m ratio (0.62 to 0.72) and growth rate (-0.25 to 0.81 div. d^-1) of C. marina cells tended to decrease, and there was a significant positive correlation between the two parameters. Both the F_v/F_m ratio and growth rate of C. marina cells were positively correlated with DIN concentrations, which also supported the inference that DIN was responsible for controlling the dynamics C. marina HAB. Thus, our results suggest that the F_v/F_m ratio, combined with information about environmental factors, may be useful in evaluating the nutrient status and growth potential of C. marina during field blooms.