Time series measurements of leucine incorporation as a measure of bacterial production in the subtropical North Pacific Ocean

Samples were collected at or in the vicinity of Station ALOHA on 24 different cruises. On each cruise, rates of 3H-Leu incorporation into protein were measured. Seawater samples for measurements of production were collected from pre-dawn vertical hydrocasts at 6 discrete depths (5, 25, 45, 75, 100, 125 m) using polyvinyl chloride sampling bottles affixed to a rosette sampler. Polyethylene amber bottles (125 ml capacity) were subsampled from the CTD rosette bottles, and duplicate acid-cleaned 12 ml polycarbonate centrifuge tubes were filled from each depth. Each polycarbonate tube was inoculated with 20 nmol L-1 (final concentration) 3,4,5-3H-leucine. An additional 1.5 ml per depth was subsampled into 2 ml microcentrifuge tubes  containing 100 µl of 100% (w/v) ice-cold trichloroacetic acid (TCA) to serve as a killed blank. The polycarbonate sample tubes were capped and incubated in situ over the photoperiod to measure rates of 3H-Leu incorporation in both dark (through use of black cloth bags) and light on a free-drifting array. At the end of the photoperiod, triplicate 1.5 ml subsamples were removed from each tube and added to 2 ml microcentrifuge tubes containing 100 µl of 100% ice-cold TCA; these tubes were stored frozen until analysis. Samples were processed following a modified method of the microcentrifuge method.