What are we studying?

Identifying the biodiversity of Southern Ocean protist populations.

New organisms are being found and described every year. A guide to more than 500 Antarctic protists with photographs and descriptions was published in 2005, as an aid to the identification of these organisms.

Antarctic Marine Protists
F.J. Scott & H.J Marchant, editors
Published by: Australian Biological Resources Study, Canberra and Australian Antarctic Division, Hobart, 2005. 563 pp. ISBN 0 642 56835 9

Determining the distribution and abundance of protists in the Southern Ocean.

The distribution, abundance and types of phytoplankton present are being determined using their photosynthetic pigments, by light and electron microscopy, and using electronic particle counters. Factors that control population abundance are being studied in relation to oceanography, nutrients and grazers - information vital to models of global carbon budgets. We are also investigating associations between species and ecological processes or oceanic regimes.

Chlorophyll distribution map off the antarctic coast (at bottom) in relation to 1000m depth contour and ice edge. Values represent the total abundance in the top 150m of the water.
Distribution of chlorophyll a near the Antarctic coast, integrated to 150m depth.
Vertical distribution of chlorophyll a, showing highest concentrations on the pycnocline (layer where density changes).
Vertical distribution of chlorophyll (mg.m-3) in the top 200m along a north-south transect off Antarctica. Ice cover is shown at top left. ASF = Antarctic Slope Front where cold (-2°C) coastal water meets warmer (1°C) oceanic water. Tmin = temperature minimum layer.

Determining the response of protist populations to enhanced ultraviolet radiation due to the Antarctic ozone hole.

Protists in the upper waters of the ocean are exposed to increased ultraviolet radiation (UV) at the time of the "spring bloom". Different species vary in their susceptibility to damage by UV, and changes of species composition have been observed in Antarctic protist communities. Such changes directly affect the abundance and nature of food available to larger organisms as well as the extent of CO2 uptake in surface waters.

Determining the feeding rates and preferences of protozoa.

Measurements are being made of the rates of protozoan feeding in the Southern Ocean, as well as studies of their feeding selectivity. Protozoan preference for food of particular sizes and "flavours" affects their role in the "microbial loop".

Determining the abundance, viability and activity of marine bacteria.

Scientists are measuring phytoplankton production, carbon dioxide uptake, carbon sedimentation, nutrient concentrations and oceanography to build an integrated picture of the smallest, but the most important, components of the marine food web.

Effect of elevated CO2 on phytoplankton

To find out how Southern Ocean phytoplankton and microbial communities will change as atmospheric CO2 concentrations increase scientists are:

  • Characterising the effects of enhanced CO2 on key species, in particular the carbonate producing coccolithophorids and key diatoms.
  • Characterising the effect of enhanced CO2 on taxonomic composition and cell size of microbial communities and the processes of photosynthesis, respiration, grazing and biogenic sedimentation.
This page was last modified on 12 August 2010.