Water was collected from 3 meters depth at the San Pedro Ocean Time-series (SPOT) station (33°33'N, 118°24'W, off the coast of Southern California in March 2015. Six treatments were used: control, nitrate, nitrate+B1, nitrate+B7, nitrate+B12, and nitrate+B1+B7+B12 with triplicate 10L incubations. Growth was tracked daily. Particulate B-vitamin samples were collected initially, and at two points during the experiment: exponential growth and stationary phase. Exponential growth occurred at day 7. Stationary growth varied between treatment ranging from 10-12 days. The incubations were co-limited by nitrate and B12. Samples were collected from two size fractions (0.2um-3um, and >3um) using in-line peristaltic filtration. Samples were flash frozen and stored at -80C until analysis. B-vitamin extraction was performed as described in Suffridge et. al (2017).
Particulate B-vitamins were extracted in acidic methanol (pH 3.5, 5% MeOH, 95% LC/MS Grade water) using bead-beating for cell lysis and a 30C incubation for B-vitamin extraction. A liquid phase extraction using chloroform (1:1 v/v) was used to clean up the samples prior to analysis.
Analysis was conducted using a Thermo TSQ Quantum Access triple quadrupole LC/MS with an ESI interface and a C18 column (Discovery HS C18 10cm x 2, 1mm, 5μm column, Supelco Analytical) Sanudo 2012. Quantification conducted using an internal standard. Triplicate injections were used to increase precision.
Cited References:
Suffridge, Christopher; Cutter, Lynda; Sanudo-Wilhelmy, Sergio (2017) A New Analytical Method for Direct Measurement of Particulate and Dissolved B-vitamins and Their Congeners in Seawater. Front. Mar. Sci. vol.4 doi.org/10.3389/fmars.2017.00011
Sanudo 2012 - Proc Natl Acad Sci U S A. 2012 Aug 28;109(35):14041-5. doi: 10.1073/pnas.1208755109. Epub 2012 Jul 23