The relative abundance of dimethylsulfoniopropionate (DMSP) among other zwitterions in branching coral at Heron Island, southern Great Barrier Reef.

Dimethylsulfoniopropionate (DMSP) and eleven other target zwitterions were quantified in the branch tips of six Acropora species and Stylophora pistillata hard coral growing on the reef flat surrounding Heron Island in the southern Great Barrier Reef (GBR), Australia. Hydrophilic interaction liquid chromatography mass spectrometry (HILIC-MS) was used for sample analysis with isotope dilution MS applied to quantify DMSP. The concentration of DMSP was ten times greater in A. aspera than A. valida, with this difference being maintained throughout the spring, summer and winter seasons. In contrast, glycine betaine was present in significantly higher concentrations in these species during the summer than the winter. Exposure of branch tips of A. aspera to air and hypo-saline seawater for up to 1 h did not alter the concentrations of DMSP present in the coral when compared with control samples. DMSP was the most abundant target zwitterion in the six Acropora species examined, ranging from 44-78% of all target zwitterions in A. millepora and A. aspera, respectively. In contrast, DMSP only accounted for 7% in S. pistillata, with glycine betaine and stachydrine collectively accounting for 88% of all target zwitterions in this species. The abundance of DMSP in the six Acropora species examined points to Acropora coral being an important source for the biogeochemical cycling of sulfur throughout the GBR, since this reef-building branching coral dominates the coral cover of the GBR. Graphical Abstract HILIC-MS extracted ion chromatogram showing zwitterionic metabolites from the branching coral Acropora isopora.

Quantification of dimethylsulfoniopropionate (DMSP) in Acropora spp. of reef-building coral using mass spectrometry with deuterated internal standard.

Dimethylsulfoniopropionate (DMSP) in scleractinian coral is usually analysed indirectly as dimethylsulfide (DMS) using gas chromatography (GC) with a sulfur-specific detector. We developed a headspace GC method for mass spectral analysis of DMSP in branching coral where hexa-deuterated DMSP (d 6 -DMSP) was added to samples and standards to optimise the analytical precision and quantitative accuracy. Using this indirect HS-GC-MS method, we show that common coral sample handling techniques did not alter DMSP concentrations in Acropora aspera and that endogenous DMS was insignificant compared to the store of DMSP in A. aspera. Field application of the indirect HS-GC-MS method in all seasons over a 5-year period at Heron Island in the southern Great Barrier Reef indicated that healthy colonies of A. aspera ordinarily seasonally conserve their branch tip store of DMSP; however, this store increased to a higher concentration under extended thermal stress conditions driven by a strong El Niño Southern Oscillation event. A liquid chromatography mass spectral method (LC-MS) was subsequently developed for direct analysis of DMSP in branching coral, also utilising the d 6 -DMSP internal standard. The quantitative comparison of DMSP in four species of Acropora coral by indirect HS-GC-MS and direct LC-MS analyses gave equivalent concentrations in A. aspera only; in the other three species, HS-GC-MS gave consistently higher concentrations, indicating that indirect analysis of DMSP may lead to artificially high values for some coral species. Graphical Abstract Dimethylsulfoniopropionate (DMSP) was quantified in Acropora spp. of branching coral using deuterated stable isotope dilution mass spectrometry.

Surface flux and vertical profile of dimethyl sulfide in acid sulfate soils at Cudgen Lake, northern New South Wales, Australia.

A dimethyl sulfide (DMS) vertical concentration profile and DMS surface emission flux were quantified in undisturbed acid sulfate soils (ASS) at Cudgen Lake on the north coast of New South Wales, Australia. A deuterated internal standard was used to account for soil adsorption characteristics. The DMS vertical concentration profile increased exponentially from 0.6 m depth to the surface layer. This profile reflected the adsorption properties of the ASS horizons present and the experimentally determined octanol/water partition coefficient for DMS of 1.36, suggesting that DMS would be mobilised in the soil water medium for upward translocation in time due to surface evaporation. The organic material in the oxidised ASS crustal layer had a chemically strong adsorption affinity for DMS, which appeared to restrain its emission from surface soil particles to the atmosphere. The seasonally averaged DMS surface flux estimate from the Cudgen Lake ASS was 9 ng S m-2 min-1, which is relatively low by comparison to DMS fluxes reported from other wetland soils such as salt-marshes and acidic peat bogs. The worldwide annual average DMS emission from ASS was estimated to be 1.14 × 10-3 Tg S, which is globally insignificant by comparison to DMS emission from the world's oceans.