Gradients1-KOK1606-PP-UW_2020-03-10-v1.0

Cruise: KOK1606, Gradients 1 Project Name: Simons Foundation Gradients NPSG Description: The phosphorus content of particulate material (PP) was collected by semi-automated and sequential filtration of the ship’s underway flow through seawater onto acid-washed and combusted GFF filters. Select samples had a piggybacked GFF filter holder in sequence for collection of dissolved organic material and/or evaluation of trapping efficiency of GFF; these samples are termed ‘<0.7 micron P’. Following filtration, filters were placed in histoprep capsules and stored at -80°C for later analysis. Post-cruise, all filters were thawed overnight, combusted at 450°C for 4.5 hours, then extracted with 0.15 M HCl for 1 hour at 60°C. PP was then analyzed spectrophotometrically as SRP in a 1.0 cm cell at 880 nm following Strickland and Parsons (1972). Recovery efficiency was assessed from the analysis of a known dry weight of certified reference material (National Institute of Standards, NIST 1515, apple leaves, certified 0.159% P by weight). The ship’s location, sea surface temperature and salinity from ship’s underway instrumentation are matched to the mid-point of each PP filtration time.