Time-series measurements of size fractionated primary production (14C-assimilation) in the subtropical North Pacific Ocean

Filter size-fractionated (>0.2-3 μm) particulate 14C-based rates of primary production were measured at six discrete depths (5, 25, 45, 75, 100, and 125 m) throughout the euphotic zone. Seawater samples from each depth were subsampled into triplicate 30-mL polycarbonate centrifuge tubes from a pre-dawn cast, inoculated with 70 µL of NaH14CO3-, then incubated over the full photoperiod (~12-14 hours) on a floating in situ array at the corresponding depths where the water was collected. At the end of the incubation period (after sundown), 25 mL of each sample was vacuum-filtered first onto a 25-mm diameter 3-μm pore size polycarbonate membrane, then the filtrate was vacuum-filtered onto a 25-mm diameter 0.2-μm pore size polycarbonate membrane filter. The rates reported here are for the >0.2-3 μm size fraction.