Measurement of DMS, DMSO, and DMSP in natural waters by automated sequential chemical analysis

Abstract

Dimethyl sulfide (DMS), dimethylsulfoniopropionate (DMSP), and dimethyl sulfoxide (DMSO) are key components of the marine sulfur cycle. The concentrations of these compounds exhibit large spatial and temporal variability in the surface ocean, creating a need for high resolution sampling. Existing automated underway measurement systems for DMS do not measure DMSP or DMSO, so their spatial variability is less well-characterized. We present an accurate and robust method for the automated, high throughput sampling and measurement of DMS, DMSO, and DMSP (DMS/O/P) in a single water sample. The method is based on a three-step sequence of purge and trap gas chromatography, where DMS analysis is followed by the enzymatic reduction of DMSO to DMS and the alkaline hydrolysis of DMSP to DMS. The system, which we call the Organic Sulfur Sequential Chemical Analysis Robot (OSSCAR), includes automated calibrations and blank determinations. OSSCAR can be used as a front-end system for any sulfur detector and is suited for continuous underway analysis or the measurement of discrete water samples. The system described here has a minimum detection limit of 0.

Concentrations and cycling of DMS, DMSP, and DMSO in coastal and offshore waters of the Subarctic Pacific during summer, 2010‐2011

“…[] likely reflect the difference in sampling time (late‐summer vs. early spring), and the role of DMS photo‐oxidation in the formation of DMSO d [ Toole et al ., ; Bouillon et al ., ]. Our own recent measurements [ Asher et al ., ] demonstrate high DMSO d/t concentrations along Line P during August of 2014, with a mean value of ∼11 nM. These additional data suggest persistently high summer‐time DMSO concentrations in the NE Subarctic Pacific.…”

“…Due to a bottle labeling problem, we were forced to average DMSO d samples from the coastal and transitional stations (P4‐P12), which limits our ability to discern DMSO d variability among coastal/transitional waters. Nonetheless, the averaged DMSO d concentrations we measured (range 13.4‐23 nM; Table ) were higher than previous values obtained in the Subarctic Pacific [ Asher et al ., ; Bates et al ., ], likely reflecting seasonal and inter‐annual variability.…”

“…As both an important sink of DMS through photo‐oxidation and biological oxidation, and as a source of DMS from DMSO reduction, DMSO measurements should be included in future DMS research programs. We have recently developed an automated method for surface DMSO (and DMS/P) measurements [ Asher et al ., ], which will enable future research into the spatial distribution of this compound in marine surface waters.…”

Impact of ocean acidification on Arctic phytoplankton blooms and dimethyl sulfide concentration under simulated ice-free and under-ice conditions

“…Water samples for DMS concentration analysis were withdrawn on days T0, T2, T4, and every day for the remainder of the incubation period. DMS concentrations were determined on-board the ship using purging, trapping, and S-specific gas chromatography, as described by Asher et al (2015). The custom-built system described by Asher et al (2015) was used here in manual mode by directly injecting 10 mL of each incubation sample into a sparge vessel.…”

“…DMS concentrations were determined on-board the ship using purging, trapping, and S-specific gas chromatography, as described by Asher et al (2015). The custom-built system described by Asher et al (2015) was used here in manual mode by directly injecting 10 mL of each incubation sample into a sparge vessel. Water for DMS analysis was subsampled directly from each bag using a Luer-lock syringe and injected into the custom-built system at most 40 min after sampling.…”