The samples were collected using a CTD rosette and an appropriate volume of water was filtered through a 25mm GF/F filter soon after collection. The filters were then stored in liquid nitrogen until analyzed. The analysis and duplicate filter precision details as well as calibration details are provided in may18atl_HPLC_readme.pdf. The samples were run at NASA GSFC by Crystal Thomas.

The diagnostic pigments were measured using High-performance liquid chromatography as detailed in Van Heukelem and Thomas (2001) and Hooker et al (2005).

The HPLC used for pigment analysis is an Agilent RR1200 with a programmable autoinjector (900 ul syringe head), refrigerated autosampler, degasser, and photo-diode array detector with deuterium and tungsten lamps. The HPLC is controlled by Agilent Chemstation software. The 4.6 x 150 mm HPLC Eclipse XDB column (Agilent Technologies, Palo Alto, CA) is filled with a C8 stationary phase (3.5 um stationary phase); the mobile phase consists of a linear gradient from 5-95% solvent B over the 27 minutes, for which solvent A is 70 parts methanol, 30 parts 28 mM tetrabutylammononium acetate (pH 6.5) and solvent B is methanol. The column temperature is 60 C and the photo diode array detector is set to plot chromatograms at 450, 665, and 222 nm to acquire visible absorbance spectra between 350 and 750 nm.