The effect atmospheric aerosols have on solar radiation is a significant uncertainty in climate change research. Sulfate aerosols in particular could have a significant mediating effect on the radiative balance of the planet, due to both their light-scattering properties and their effectiveness as cloud condensation nuclei (CCN). The main natural source of sulfate aerosols is the production of dimethylsulfide (DMS) by marine phytoplankton communities. In the Southern Ocean and Antarctica, anthropogenic sulfate contributions are minimal and non-sea-salt sulfate aerosol concentrations are wholly dominated by the seasonal flux of DMS from the ocean. The magnitude of this flux is controlled by Antarctic marine microbial communities.
Ozone depletion is likely to have a significant effect on Antarctic marine microbial communities, and therefore the production of DMS. Given the variability of DMS production from species through to the community level, it is unknown whether enhanced UVR resulting from ozone depletion will increase or decrease DMS production.
This study investigated the effects of natural solar radiation on Antarctic marinenmicrobial communities using long-term (two-week) incubations at Davis Station, Antarctica. These experiments resulted in a number of findings. Firstly, rapid sea-ice break-up may be a major contributor to DMS release, as dimethylsulfoniopropionate (DMSP - the precursor to DMS) increased substantially (by up to 100×) and rapidly when the microbial communities were subjected to surface irradiances while still acclimated to sub-ice light. Indeed, light-induced stress had a far greater effect on DMSP production than UVR-induced changes to community composition. Secondly, turnover rates of DMS and DMSP were very rapid in all our experiments. Thus the net changes in DMS and DMSP concentrations calculated in the incubations were a fraction of the gross production and consumption occurring. These findings have major implications for estimations of seasonal Antarctic production of DMS, given the magnitude and speed of both the stress-induced DMSP production response, and the turnover rates observed.