Dataset: SPOT- Retinoid

Location: San Pedro Ocean Time Series (SPOT) station (33°33′N, 118°24′W)

Samples for quantification of retinal oxime 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. Particulate samples were collected using in-line 0.2µm, 3µm and 10µm pore-size filters and a peristaltic pump (flow rate < 50 ml per minute), transferred into sterile cryovials and were immediately stored at -80 degrees C until analysis.

Pigments were extracted from the filters in 3 mL of methanol, BHT (butylated hydroxytoluene) was added and placed in a -20 degrees C freezer overnight. The retinal oxime was formed by the addition of hydroxylamine hydrochloride and irradiated under yellow light for 2 hours before analysis. Retinal oxime samples were analyzed by liquid chromatography/triple mass spectrometry (LC/MS/MS/MS). The LCMS system consists of a ThermoTSQ Quantum Access electro-spray ionization triple quadrupole mass spectrometer, coupled to a Thermo Accela High Speed Liquid Chromatography system.

For chlorophyll-a measurements, 100 microliters of the pigment extraction were diluted in acetone (50x dilution) and analyzed using a Turner 10AU fluorometer.

Bacterial production was estimated by incorporation of [3H] thymidine and [3H] leucine into DNA and protein, respectively, as earlier described (Simon & Azam, 1989, Fuhrman and Azam 1982).