The prevailing oceanographic conditions and circulation within a region influences the distribution of marine biota (such as plankton, invertebrates and fish) and, therefore, the feeding areas of their land-based predators.

Knowing which areas are highly productive or species rich is important in understanding the Heard Island and McDonald Islands (HIMI) ecosystem and in managing fisheries and conserving habitats.

Oceanographic research was conducted as part of the multi-disciplinary voyage to the waters around Heard Island during the summer of 2003/04.

How the oceanographic research was carried out

The aim of this research was to:

  • describe the physical features of the system such as fronts, currents and eddies;
  • determine the spatial and temporal variation of these features; and
  • investigate linkages between the distribution and abundance of primary and secondary production.

A range of instruments were used to sample various water properties. Currents were measured with an acoustic doppler current profiler (ADCP) mounted on the ship’s hull. A CTD (conductivity-temperature-depth) instrument was deployed 42 times to measure salinity, temperature and depth from the surface to the sea floor. Water samples were also taken at regular depths, and later analysed for their oxygen and nutrient content and filtered to determine the abundance of phytoplankton.