Fig. 1: Day-to-night ratios for individual bins of the optical particle counter, total marine aerosol count for optical diameter (D_op) ≥ 0.25 μm, and chlorophyll-a concentration along R/V Tara’s route.

(M) Tara’s route, color-coded by month and dotted arrows showing the sailing direction. A The ratio (5-day running average) of day-to-night concentration of marine aerosol for each size bin of the optical particle counter. B The total aerosol count (daily mean) for D_op ≥ 0.25 μm, the gray dots are the raw total counts per minute. The colors as defined in the map. C A 5-day running average of chlorophyll-a concentration measured with the AC-S aboard Tara (black circles) and calculated using satellite data (green triangles; see “Methods”), with the shaded area outlining one standard deviation. The day-to-night ratios are greater than one on the vast majority of the route and largest in clean areas with low chl-a concentration, i.e., in oligotrophic (“blue”) waters.