Dataset: Model-building biogeochemical data set from ASPIRE
Deployment: NBP1005

Dissolved inorganic nutrient samples were pre-filtered through 0.45-μm polycarbonate syringe filters, kept refrigerated, and analyzed onboard the ship within 1 day of sampling. Nitrate (NO3−), nitrite (NO2−), am- monium (NH4+), phosphate (HPO42−), and silicic acid (Si(OH)4) were measured using a five-channel Lachat Instruments QuikChem FIA+ 8000s series autoanalyzer in conjunction with a Lachat Instruments XYZ AutoSampler (ASX-500 Series), two Lachat Instruments RP-100 Series peristaltic Reagent Pumps, and Omnion Software, version 3.0.220.02. 

Seawater samples were analyzed for dissolved Fe over the period of January to August 2012, using an automated flow injection ICP-MS method developed at Rutgers University (Lagerström et al., 2013). Briefly, the automated device loaded a 9 mL aliquot of seawater, buffered online to pH 7.0 with 3 mL of acetic acid/ammonium hydroxide buffer, onto a column packed with Nobias PA1 chelating resin (Hitachi High-Technologies). The column was eluted with 1.5 M nitric acid directly into the nebulizer of an Element-1 sector field ICP-MS (Thermo-Finnigan, Bremen, Germany). The eluate, a 200-fold concentrate of the sample, was analyzed in medium resolution and temporal peak integration was performed in Matlab using a script written in-house. Quantification was carried out using isotope dilution (Fe, Ni, Cu and Zn) or a matrix-matched external standard curve (Mn). 

Samples for particulate organic carbon (POC) and nitrogen (PN) were collected by cleanly filtering 100–600 mL of seawater onto a 25-mm diameter, combusted GF/F filter (nominal pore size of 0.7 μm) which was then folded sample side in and frozen at −80°C. Samples were processed at Rutgers University and analyzed using a Carlo-Erba CHN analyzer (Hedges and Stern, 1984). 

Water column Chl a concentration (used as a proxy for algal biomass) was measured onboard ship using acetone extraction and a spectrofluorometer (Alderkamp et al., 2015). Shipboard values were calibrated against a second set of samples collected similarly, flash-frozen in liquid N2, stored at −80°C, and analyzed at Mote Marine Lab using HPLC (Wright et al., 1991; see Alderkamp et al., 2015).