Functional dynamics of the microbial loop in saline lakes of the Vestfold Hills

Chlorophyll a concentrations in the mixolimnion ranged between 0.3 and 4.4 micrograms per litre during the study period and a deep chlorophyll maximum persisted throughout the year below the chemo/oxycline. Bacterioplankton abundance showed considerable seasonal variation related to light and substrate availability. Autotrophic bacterial abundance ranged between 0.02 and 8.94 x 10 to the 8 per litre and heterotrophic bacterial abundance between 1.26 and 72.8 x 10 to the 8 per litre throughout the water column. the mixolimnion phtyoplankton was dominated by phytoflagellates, in particular Pyramimonas gledicola.

P. geldicola remained active for most of the year by virtue of its mixotrophic behaviour. Photosynthetic dinoflagellates occurred during the austral summer, but the entire population encysted for the winter. Two communities of heterotrophic flagellates were apparent; a community living in the upper monimolimnion and a community living in the aerobic mixolimnion.

Both exhibited different seasonal dynamics. The cliliate community was dominated by the autotroph Mesodinium rubrum. The abundance of M. rubrum peaked in summer.

A proportion of the population encysted during winter. Only one other ciliate, Euplotes sp., occurred regularly. Two species of Metazoa occurred in the mixolimnion; a calanoid copepod (Paralabidocera antarctica) and a rotifer (Notholca sp.).

However, there was no evidence of grazing pressure on the microbial community. In common with most other Antarctic lakes, Ace Lake appears to be driven by 'bottom-up' forces. The fields in this dataset are: Ace Lake Aerobic monimolimnion Ammonia Ammonium Ash free dry weight Autotrophic Bacteria Bacterial Production Leucine Bacterial Production Thymidine Biomass Carbon Cell Chlorophyll a Concentration Copepods Date Date Code Depth Diatoms Dinoflagellates Dissolved Organic Carbon Dissolved Oxygen Doubling Generation Time Heterotrophic Bacteria Heterotrophic Nanoflagellates Ice Thickness Intrinsic Growth Rate Julian Day Julian Month Mesodinium rubrum Mesodinium rubrum cysts Mixolimnion Monimolimnion Nauplii Nitrate Nitrite Notholca sp.

Other Ciliates Oxygenated strata Paralabidocera antarctica copepodid Paralabidocera antarctica naupliar Particulate Organic Carbon Phosphate Phototrophic Nanoflagellates Salinity Season Soluble Reactive Phosphorus Total Ciliates Water Temperature