Fig. 4. Molecular differences between different CO₂ treatments.

(A) Exemplary van Krevelen diagrams showing only the molecular formulae (out of 7360) that significantly varied in their intensities between the five high PCO₂ and control mesocosm replicates, tested for the respective day (P < 0.001). The different colors represent differences in normalized relative peak intensity: blue dots indicate an increase in peak intensity, whereas red dots indicate a decrease in peak intensity. Green dashed lines represent time points of phytoplankton blooms. (B) The results are within the statistical error, determined by performing the same test on a randomized data set.