Fig. 4: Statistical analysis of heterogeneous uptake of N and C.

Frequency distribution of a, b 15N:14N for Crocosphaera and Cyanothece (6 L to 12 L) and c, d 13C:12C for Crocosphaera and Cyanothece (6 L to 12 L), respectively. Red dashed curve is the normal distribution for the initial condition (t = t0) with the special y-axis on the right (that on the left is for other plotted values). Green dashed curve is the normal distribution based on the mean value and standard deviation of the probability density. S, bimodal separation; Dev, deviation from the normal distribution; n, number of samples. Both for Crocosphaera and Cyanothece, S and Dev are larger for 15N:14N, suggesting stronger heterogeneity for N uptake.