A robust approach for the determination of dimethylsulfoxide in sea ice

Abstract

The melting of sea ice samples is acknowledged to be deleterious to sympagic microorganisms due to the hypo-osmotic shock undergone by the organism when released from high salinity brine inclusions into the sample melt. Because melting of sea ice samples was also anticipated to modify the initial proportions of dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), and dimethylsulfoxide (DMSO), three sample treatments were tested on an Antarctic sea ice sample, with the aim of identifying an efficient procedure that could routinely be applied for the determination of DMSO in sea ice. Herein, it was demonstrated that purging the melted sample before the determination of DMSO in the sample via an enzyme-linked method produced reliable DMSO results (215.8 ± 8.9 nmol L -1 , precision 4.1%). However, analysis revealed that the unintentional enzymatic cleavage of DMSP through the subsequent production of interfering DMS during melting caused an overestimation of the DMSO content in the sample by more than 59% and concurrently an underestimation of the DMSP content by approximately 9%. The sequential determination of DMSP after the DMSO determination by the enzyme-linked method was shown to be problematic. To circumvent all of these issues, we recommend an analytical procedure for the sequential determination of DMS, DMSP, and DMSO in sea ice. Ultimately, the first depth profile of DMSO at high resolution in sea ice was produced. The depth-integrated DMSO concentration in sea ice was determined to be 718 µmol m -2 , which indicated that Antarctic sea ice is a potentially important source of DMSO for the Southern Ocean. Limnol. Oceanogr.: Methods 9, 2011Methods 9, , 261-274 © 2011, by the American Society of Limnology and Oceanography, Inc. LIMNOLOGY and OCEANOGRAPHY: METHODSthe subsequent gas phase analysis of the produced DMS via a gas chromatography procedure. Depending on the reduction method used, interference with DMSP in the sample may occur, leading to an overestimation of DMSO content (reviewed by Simó 1998).Elimination of DMSP prior to DMSO analysis (Simó et al. 1996;Simó et al. 1998) or the use of a specific reducing agent, such as DMSO reductase (DMSOr) (Hatton et al. 1994), can prevent this bias. The main motivation of studying DMSO in sea ice is that DMSO can be produced in high concentrations by ice algae, because of the potential role of DMSO in osmoregulation and cryoprotection (Lee et al. 2001). A good correlation between intracellular levels of DMSO (particulate DMSO or DMSOp) and DMSP (particulate DMSP or DMSPp) has been shown in data collected in various marine biomes and during different seasons. The data suggest that both compounds have a common origin in phytoplankton and that DMSP may be the precursor of DMSO (Simó and Vila-Costa 2006; Hatton and Wilson 2007). If the same correlation applies to sea ice, high levels of DMSO are expected to be found in sea ice because high levels of DMSP (up to three orders of magnitude higher than background sub-nanomolar values in seawater) are co...

Ice sheet record of recent sea‐ice behavior and polynya variability in the Amundsen Sea, West Antarctica

“…This is consistent with the hypothesis that a larger sea‐ice breakup and more open water in summer will often result in larger phytoplankton blooms and increased release of DMS, which others have shown [ Pasteur et al ., ; Isaksson et al ., ; Abram et al ., ; Rhodes et al ., ; Abram et al ., ; Arrigo et al ., ]. This is also consistent with several studies that show that polynyas can produce more significant fluxes of DMS into the overlying atmosphere than adjacent waters in the sea‐ice zone [ Zemmelink et al ., , 2008; Tison et al ., ; Asher et al ., ; Brabant et al ., ].…”

Influence of short-term synoptic events and snow depth on DMS, DMSP, and DMSO dynamics in Antarctic spring sea ice

“…The vials were crimp sealed and stored to melt at 4°C in the dark until analysis as DMS. Total DMSO (particulate + dissolved fractions) was measured in the home laboratory a few months after sampling using the enzyme-linked method (Hatton et al, 1994) adapted for the determination of DMSO in sea ice as fully described by Brabant et al (2011), with overall precision < 5%.…”

High concentrations and turnover rates of DMS, DMSP and DMSO in Antarctic sea ice

“…The Southern Ocean is the largest natural source of DMS to the atmosphere [ Lana et al , 2011], contributing more than 50% of the total S aerosols in the Southern Hemisphere [ Bates et al , 1992; Chin et al , 2000]. Recent work has also documented high concentrations of DMS and the related compounds dimethylsulfoniopropionate (DMSP) and dimethylsulfoxide (DMSO) in the sea‐ice zone (SIZ) adjacent to polynya waters [ Brabant et al , 2011; Tison et al , 2010; Trevena and Jones , 2006; Zemmelink et al , 2005, 2008]. At present, the spatial and temporal coverage of sea ice sulfur measurements remains severely limited.…”