Particulate dimethyl sulphoxide in seawater:production by microplankton

Abstract

Dirnethyl sulphoxide (DMSO) represents a major pool of dissolved dimethylated sulphur in seawater However, the origin and fate of this compound in the marine environment, and its role in the biogeochermcal cycle of dimethyl sulphide (DMS), remain unclear. The only established route for the formation of DMSO in oxygenated seawater is photochemical oxidation of DMS. It is not known whether significant biotic production pathways exist. In a study of methylated sulphur speciation in coastal North Sea waters and cultures of marinc unicellular algae, we measured pools of particulate DMSO (DMSO,) at nanomolar and micromolar concentrations, respectively. Analyses of size-fractionated seawater particulates and incubation experiments provded evidence that DiviSO, wds dssociaiea with mlcroplanktonic organisms. Log-phase cultures of Amphidinium carterae and Emilianja huxleyi exhibited intracellular dimethylsulphoniopropionate (DMSP) to DMSO molar ratios of 25 and 8, respectively. Our results strongly suggest the existence of biological production and release of DMSO in eukaryotic microplankton.

Extracellular respiration of dimethyl sulfoxide by Shewanella oneidensis strain MR-1

“…It is possible, albeit unlikely, that sources produce DMSO in high enough local concentrations that it could exist in the solid state. A more likely scenario is that DMSO could exist in pseudoparticulate form by adsorbing to the silicate and calcite surfaces of marine diatoms and coccolithophorids, given its strong capacity to adsorb to positively charged surface (7,16). Finally, cold temperatures may inhibit diffusion of DMSO into the cell.…”

“…Another possible advantage may be to optimize substrate utilization. For example, algae and other eukaryotic microplankton are known to produce DMSO in aquatic environments (6,7), and strains of Shewanella have been isolated from the surface of algae (35,36). If positioning the DMSO reductase externally allows Shewanella to more efficiently capture DMSO, Shewanella might have a selective advantage for using this substrate over other organisms with an internal DMSO reductase.…”

“…systems (4,7). Accessing this source of DMSO for respiration might be difficult using traditional mechanisms.…”

Annual cycle of dimethylsulfoniopropionate (DMSP) and dimethylsulfoxide (DMSO) related to phytoplankton succession in the Southern North Sea

“…Generally, DMSPd is very low compared to DMSPp while DMSOd dominates DMSO pool and can exceed concentration of both DMS and DMSPd in euphotic waters (Hatton and Wilson, 2007). Simó et al (1998) reported DMSOp and DMSOd concentrations for North Sea samples containing Phaeocystis (UK coast, in June) of respectively 16 and 25 nmol L − 1 . This is lower than our concentrations but their samples were probably taken at the end of Phaeocystis bloom, while our samples covered the whole bloom period.…”

“…Only a few studies focused on DMSO concentrations in the North Sea because of the later evidence of the existence of particulate DMSO (DMSOp) until recent years (Simó et al, 1998) and its importance for the S cycle (Hatton et al, 2004;Green and Hatton, 2014). Unlike DMS and DMSP that are usually restricted to the euphotic zone, DMSO is ubiquitous and dominant throughout the water column (Hatton et al, 2004).…”