CTD and Niskin sampling follow HOT procedures summarized in detail: https://hahana.soest.hawaii.edu/hot/protocols/protocols.html#

Dissolved Oxygen sampling and titrations from Niskin bottles follow HOT procedures. Briefly, oxygen samples were the first samples drawn from the Niskin bottles as soon as the rosette arrived on deck, free of bubbles, and fixed. Samples were analyzed with a computer controlled potentiometric titration. At 2 depths on each cast, 3 titrations were performed and had an average standard deviation of 0.4 micromol/L.

Particulate Carbon and Nitrogen field and laboratory protocols follow HOT procedures (except sample analysis took place at Princeton University using a Vario ISOTOPE select EA-IRMS). Briefly, 4 to 20 L of water was collected from Niskin bottles, pre-filtered with an inline 202um mesh screen, and collected on combusted 25mm GF/F (Whatman, nominal pore size 0.7um), folded, and wrapped in clean (combusted) foil for storage at -20 degrees C until laboratory analysis. Samples were oven dried at 55-60 degrees celsius (samples were not acidified so C represents total C), pelletized in 9x11 tins, and analyzed via EA-IRMS for particulate carbon, delta-13C particulate carbon, particulate nitrogen, delta-15N particulate nitrogen. Six blank (dry) filters were analyzed for background C and N and subtracted from measured PC and PN sample values.

Particulate Phosphate field and laboratory protocols follow HOT procedures. Briefly, 4 to 10 L of water was collected from Niskin bottles, pre-filtered with an inline 202um mesh screen, and collected on combusted 25mm GF/F (Whatman, nominal pore size 0.7um), folded, and placed in clean glass tube, storage at -20 degrees C until laboratory analysis. One sample from each depth was combusted in 16 x 100 mm clean glass test tubes at 450°C for 4.5 hours in a muffle furnace, allowed to cool and immersed in 10ml 0.15N HCL/vortex/ 1 hour leach/vortex/30 Minute Spin/ 1 hour color development) (5ml sample : 500ul Mixed Reagent). The liberated orthophosphate is reacted with a mixed reagent of molybdic acid, ascorbic acid and trivalent antimony to form phosphomolybdic acid. This heteropoly acid is then reduced to the colored molybdenum blue complex by ascorbic acid and the solution is measured spectrophotometrically. This procedure measures all forms of phosphorus which can be released by combustion and acid hydrolysis. Three blank (dry) filters were analyzed for background P and subtracted from measured PP sample values.

niskin.csv