Michael received his PhD in 1997 from the University of Bremen. He then worked as a postdoctoral research and postdoctoral fellow at the University of East Anglia (Norwich) before he became a lecturer at the University of Essex (Colchester). Michael’s research interest is the production of biogenic trace gases in marine environments and their ecological and physiological roles. Marine algae are a source of volatile organohalogens (e.g. methyl iodide), non-methane hydrocarbons (e.g. ethene, isoprene) and the sulphur gas dimethyl sulphide (DMS). These compounds can affect atmospheric processes after sea-to-air transfer. Over the last 30 years, much research has focused on the production of DMS. This volatile compound plays a major role in the biogeochemical cycling of sulphur, influences atmospheric acidity and is thought to affect climate through the production of cloud condensation nuclei. The precursor of DMS is dimethylsulphoniopropionate (DMSP), a compatible solute found in the cells of some types of marine phytoplankton and seaweeds, but the conversion of DMSP to DMS occurs via a network of processes within the marine microbial foodweb.
Dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) are sulfur compounds that may function as antioxidants in algae. Symbiotic dinoflagellates of the genus Symbiodinium show strain-specific differences in their susceptibility to temperature-induced oxidative stress and have been shown to contain high concentrations of DMSP. We investigated continuous cultures of four strains from distinct phylotypes (A1, A1.1, A2 and B1) that can be characterised by differential thermal tolerances. We hypothesised that strains with high thermal tolerance have higher concentrations of DMSP and DMS in comparison to strains with low thermal tolerance. DMSP concentrations were strain-specific with highest concentrations found in A1 (225±3.5 mmol·L-1 cell volume) and lowest in A2 (158±3.8 mmol·L-1 cell volume). Both strains have high thermal tolerance. Strains with low thermal tolerance (A1.1 and B1) showed DMSP concentrations in between these extremes (194±19.0 and 160±6.1 mmol L-1 cell volume, respectively). DMS data did further confirm this general pattern with high DMS concentrations in A1 and A1.1 (4.1±1.22 and 2.1±0.37 mmol·L-1 cell volume, respectively) and low DMS concentrations in A2 and B1 (0.3±0.06 and 0.5±0.22 mmol·L-1 cell volume, respectively). Hence, the strain-specific differences in DMSP and DMS concentrations did not explain the different abilities of the four phylotypes to withstand thermal stress. Future work should quantify the possible dynamics in DMSP and DMS concentrations during periods of high oxidative stress in Symbiodinium sp. and address the role of these antioxidants in zooxanthellate cnidarians.