Abstract:
A taxonomic assessment of sea ice bacteria abundance and their response to climate induced stress was investigated from the sea ice around Seabee Hook, Cape Hallett. Four sites at different points around Seabee Hook were established for a representative survey of the annual ice present in Edisto Inlet. The ice had broken out the previous year and new ice formed over the winter providing ideal
... conditions to compare the distribution and abundance of bacteria occurring in pack ice at the tongue of the Mertz Glacier with bacteria from fast ice at Cape Hallett. Bacteria were collected from the ice at regular intervals with ice cores. A complete ice profile was extracted at each site to examine community composition and structure. Water samples were also collected from 5, 25 and 50m depths and processed in the same way as ice cores and compared. 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. 
