Dataset: Quantification of different chemical forms of cobalamin from San Pedro Ocean Time Series (SPOT) cruises on R/V Nerissa and R/V Yellowfin from March to December 2017

Samples for quantification of the different cobalamin forms were collected at a six of depths within the euphotic zone (5-250m). Seawater was collected from each CTD depth using Niskin bottles and immediately filtered. Cobalamins were analyzed as in 1 Suffridge et al. (2017). Two liters of seawater were filtered through µm pore-size filters and then preconcentrated using a C18 resin (HF Bondesil (Agilent Technologies) and analyzed by liquid chromatography/triple mass spectrometry (LC/MS/MS/MS). The LC-MS system consists of a ThermoTSQ Quantum Access electro-spray ionization triple quadrupole mass spectrometer, coupled to a Thermo Accela High Speed Liquid Chromatography system. The LC system used a stable- bond C18 reversed-phase column (DiscoveryHSC18 10cm × 2.1mm,5 μm column, Supelco Analytical) with a100 μL sample loop.In order to increase the sensitivity and precision,theLC/MS was run in full-loop mode (100 μl/injection).

The LC-MS system used for the pigment quantification consists of a Thermo TSQ Quantum Access electro-spray ionization triple quadruple mass spectrometer, coupled to a Thermo Accela High Speed Liquid Chromatography pump and auto-sampler.