Extended Data Fig. 10: Positive relationship between dinoflagellate protein abundance and carbon flux.

Particulate export estimates through average mass flux (a) and particulate carbon flux (b) from the oligotrophic (St. 1, red) to equatorial upwelling region (St. 5, blue), as visualized by latitude in Fig. 5 (n = 3 tubes per depth from the same sediment trap array; error bars represent standard deviation.). c, Vertical profiles of absolute dinoflagellate exclusive protein spectral counts derived from the 3-51 µm size fraction and (d) absolute Prochlorococcus exclusive spectral counts from the 0.2-3 µm fraction along the surface gradient. Absolute spectral counts were not NSAF-normalized as performed in the functional analysis. Depth-integrated spectral counts from (e) 50-200m and (f) 200-400m highlight changes to protein inventory across the biogeochemical gradient and between the euphotic and mesopelagic zones, with the coefficient of carbon flux attenuation (b value) shown in brown (three depths per station were used to calculate the slope (b) via non-linear flux curve fitting to the Martin power law). Depth-integrated values were obtained by calculating the area under the profile for spectral counts versus depth. Depth-integrated dinoflagellate spectral counts show a positive relationship with carbon flux to 150 m (g) in contrast to Prochlorococcus which demonstrates a negative relationship.