The bacterial biomass of sea ice from Seabees Hook, Cape Hallett region

In the lab, bacterial samples were grown under light and dark conditions. Epi-fluorescence microscopy was used to analyse the metabolic activity of bacterial cells by CTC staining (which reveals metabolically active cells), DAPI staining (total cell numbers), VSP (Vital Stain and Probe which utilises oligonucleotide probes to distinguish metabolic activity), DVC (Direct Viable Count - which indicates whether cells are capable of undergoing division) and VIAGRAM (which distinguishes between live and dead cells and also gram positive and gram negative cells).

The results were examined using laser based technology (flow cytometry) and epi-fluorescence microscopy. If bacteria do respond to light, one possible explanation is that they respond to increased levels of algal photosynthate. Sugars produced by photosynthesis may be released into the seawater and then be taken up by bacterial cells.

To test this idea, 14CO2 was fed to sea ice algae and then they were incubated in the light at -2 �C. The algal cells were removed and the filtrate containing labelled photosynthate was fed to sea ice bacteria. Samples were analysed by a Liquid Scintillation counter.