Dataset: IRN-BRU MV1405 Transect 5 BioGeoChem

Sampling location: California Current System 38 N -126 E depth of sampling ~2m

Nitrate-nitrite, Phosphate, Silicate: Samples were collected from a trace-metal clean towed-fish system (Bruland et al 2005), filtered through an acid-cleaned, seawater flushed 0.2 um Acropak filter capsule (Pall 500) and analyzed shortly after collection at sea using standard spectrophotometric methods (Parsons 1984) on a Lachat QuickChem 8000 Flow Injection Analysis System.

Dissolved iron and manganese samples were collected from a trace-metal clean towed-fish system (Bruland et al., 2005), filtered through an acid-cleaned, seawater flushed 0.2 um Acropak Supor 200 filter capsule (Pall), acidified at sea to pH 1.7-1.8 with quartz-distilled HCl and stored at room temperature until analysis. Once in the lab, samples were buffered to pH 6.0 +/- 0.2 with ammonium acetate and immediately pre-concentrated using Nobias-chelate PA1 chelating resin (concentration factor ~24). Extracts were analyzed on an Element XR High-Resolution Inductively Coupled Plasma Mass Spectrometer (HR ICP-MS) using techniques described initially in Biller and Bruland (2012) with adaptations listed in Parker et al. (2016).

Diatom Amplicon Sequencing: Whole seawater was collected from a trace-metal clean towed-fish system (Bruland et al 2005) and filtered onto 3 um polyester filters using a peristaltic pump system. Filters were preserved in RLTPlus buffer and immediately frozen in liquid nitrogen.  For long term storage samples were maintained at -80 degrees celsius until extraction.  DNA extraction, PCR amplification, and analysis followed that of Chappell et al. 2016 with modification listed in Oliver et al. 2021. Briefly, DNA and RNA were co-extracted using a Qiagen Allprep RNA/DNA mini kit. Diatom 18S was amplified from the DNA using diatom-specific primers modified for Illumina indexing.  PCR products were purified, multiplexed using Illumina indices, and sequenced on an Illumina MiSeq desktop sequencer.