Time series measurements of nifH gene abundances for several cyanobacteria in the subtropical North Pacific Ocean

Time series measurements of nitrogenase (nifH) gene abundances at Station ALOHA in the subtropical North Pacific Ocean. Seawater for subsequent DNA extractions was subsampled from CTD rosette bottles into 4L polycarbonate bottles. At sea, samples were filtered onto 0.2 µm filters and filters were stored frozen until processing. Genomic DNA was extracted using either the Qiagen Plant Kit (2006-2016) or MasterPure Complete DNA and RNA Purification Kit (Lucigen; 2016-2017) and quantitfied with a Qubit v4 flourometer and a High-Sensitivity DNA Kit (ThermoFisher Scientific). Analyses of nifH gene abundances were determined by quantitative PCR using TaqMan probes and primers (as described in Church et al. 2009), relative to standard curves consisting of ten-fold dilutions of plasmids containing the appropriate nifH gene fragment. Abundances converted to concentrations (genes per liter of seawater) based on sample volumes filtered.