Figure 1. Variation of (a) intracellular Cd concentration ([Cd]_intra) and (b) intracellular Cd to phosphorus ratio (Cd/P) with free Cd ion concentration of the experimental media ([Cd²⁺]_F, 1.00×10^-13—1.21×10^-8 M) in the nutrient-enriched (+NP, circle), phosphorus-limited (-P, star), and nitrogen-limited (-N, triangle) toxicity tests for Microcystis aeruginosa PCC 7806 (WT, filled symbols) and its MC-lacking mutant (MT, open symbols).

Dashed lines are the simulation of the positive relationship between [Cd²⁺]_F and [Cd]_intra or Cd/P by the Freundlich isotherm. Data are mean ± standard error (n = 2)