Figure 3.

(a) Dynamics of replicate populations of C. reinhardtii, nine replicates in rich medium. Upper panel: mean dynamics (line) shown with the standard deviation across replicates (gray) and the mean fluctuation within systems assuming Poisson statistics (black). The illumination was turned on at 12 h as indicated by the arrow. Middle panel: the coefficient of variation (CV) across replicates (c_vm, gray) and the mean CV assuming Poisson statistics (c_vp, black). Lower panel: the ratio c_vm∕c_vp. The straight black line denotes c_vm∕c_vp=1, where variation between systems is equal to the variation we expect from counting statistics alone. (b) Dynamics of six replicate nitrogen-deprived populations with fluctuating illumination. Panels are the same as in (a). Mean illumination is constant. Fluctuations in illumination vary across replicates from no fluctuation to 30% of the mean. Upper panel: points within the shaded region are above the calibrated maximum algal density of 10⁵∕mL. Here, densities as high as 5×10⁵ were determined from counts within in a ∼1 μL volume (Ref. ¹⁰). Middle and lower panels: shaded regions indicate where c_vm,c_vp and c_vm∕c_vp were estimated from counts above the maximum calibrated density.