R/V Melville 1405 took place in the North Pacific Ocean along the California coast from 32°S to 43°N and extending from -117°E to -127°E. The Line P cruise on CCGS John P. Tully was in the North Pacific Ocean off the coast British Columbia from Vancouver (48°N, 123°W) to Ocean Station Papa (50°N, 145°W).
Samples were collected with trace-metal clean bottles or trace-metal clean pump. A small aliquot of unfiltered seawater was collected following protocols described in Twining et al. (2015). Cellular metals were analyzed with the 2-ID-E microprobe beamline at the Advanced Photon Source, Argonne National Laboratory. Incident beam energy was 10 keV to enable the excitation of Kα fluorescence for elements ranging in atomic number from Si (14) to Zn (30). Element quantification was performed by averaging the spectra from pixels representing the cells of interest. Spectra were also extracted from a background area close to each cell. The spectra were then fit with MAPS, a custom fitting software package (Vogt, 2003). Concentrations were calculated based on conversion factors obtained by running the thin-film standards NBS 1832, NBS 1833, and custom Si, P, and Fe standards made by Micromatter XRF. Cell volume was calculated based on measurements taken from bright field images of the cells and using the equations of Hillebrand et al. (1999). Cellular C was then calculated from the volumes using the equations described in Menden-Deuer and Lessard (2000).
Complete methodology is published in Twining et al. (2020).
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