Figure 1.

Effects of putrescine with or without ammonium on dinoflagellates. Relative in vivo fluorescence (FLR) of dinoflagellates Prorocentrum minimum, Karlodinium veneficum, and Levanderina fissa treated with different concentrations of putrescine with or without 100 μM ammonium. The bioassay was conducted for 24 h, and the FLR was measured at the end of the experiments. Relative FLR was calculated by dividing the FLR of the treatments by the average FLR of the controls (no ammonium or putrescine added). K. veneficum and L. fissa were treated with 500 or 750 μM putrescine with or without 100 μM ammonium. P. minimum was treated with 250 or 500 μM putrescine with or without 100 μM ammonium. Error bars indicate standard deviations of 3 replicates. Asterisks “*” indicate significant differences in the relative FLR (p < 0.05; N = 3) between the 0 µM NH₄⁺ and the 100 µM NH₄⁺ treatments.