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Diatom ecology and biogeochemistry of the Antarctic sea-ice zone

A brief summary:

The region of the western Antarctic Peninsula is warming rapidly, affecting the timing, thickness and extent of sea-ice. Modelling projections of continued warming predict a vast decline in sea-ice extent in this region. Whilst the sea-ice environment is widely acknowledged as particularly sensitive to climate change, the consequences of this variability for carbon export and marine ecosystems are largely unknown. Changes in overall primary productivity of seasonal sea-ice zones will likely have a large impact on the export of organic carbon from surface waters. The regional food web will consequently be affected, as deep dwelling organisms rely on sinking remains of surface-growing phytoplankton as food during the summer growing period. Changes in phytoplankton community structure, in response to sea-ice conditions, are also crucial in determining the downward flux of organic detritus, due to large differences in export potential between algal groups.

Diatoms are tiny, single-celled algae with cell walls made of glass. They are responsible for ~25% of global photosynthesis, and are a very large component of Southern Ocean primary production. Diatom fossils are frequently used to understand past climate and oceanographic processes, through species-level and chemical analyses. This project will document changes in these microalgal communities, particularly diatoms, in response to sea ice changes in order to understand the oceanographic and biological processes governing algal growth and speciation and link them to the production and export of carbon. Our primary research questions are: (1) How do changes in sea ice and the associated marine environment changes impact diatom communities, the main primary producers? and (2) How do changes in diatom communities in turn impact the flux of organic detritus to the deep sea?

Two of the smallest Antarctic diatoms commonly found in Ryder Bay, near Rothera Base. Thalassiosira dichotomica (left), and Navicula gelida (right), seen by scanning electron microscopy.