Time series measurements of group-specific picophytoplankton primary production

14C-based primary production by flow cytometrically determined pico plankton (Prochlorococcus, Synechococcus, and photosynthetic picoeukaryotes) were measured at six discrete depths (5, 25, 45, 75, 100, and 125 m) at Station ALOHA. Seawater samples from each depth were subsampled into triplicate 30-mL polycarbonate centrifuge tubes from a pre-dawn cast, inoculated under subdued light with 70 µL of NaH14CO3-, then incubated over the full photoperiod (~12-14 hours). At the end of the incubation period (after sundown), 5 mL of each radiolabeled sample was preserved in cryotubes containing 30 µL of 16% (final concentration 0.24% w/v) microscopy-grade paraformaldehyde, flash-frozen in liquid nitrogen, and stored at -80°C for subsequent flow cytometric sorting. Group-specific rates of 14C-assimilation by Prochlorococcus, Synechococcus, and PPE were determined by measuring the amount of 14C assimilated into populations sorted using a BD Influx sorting flow cytometer.