Southern Ocean Ecosystems - program overview

A black-browed albatross chick eagerly awaits its meal. Photo: Roger Kirkwood

The Southern Ocean represents a vast international resource and national resource to Australia. Elevated productivity in parts of the region, such as in the sea ice zone, supports a high biomass of certain species, and considerable biodiversity. Australia is a leading nation in the Commission for Conservation of Antarctic Marine Living Resources (CCAMLR) and Australia's CCAMLR policy position is underpinned by sound scientific research. This research focuses on the species that are targets, or potential targets, for commercial fisheries and on the dependent and related species in the ecosystem. During the planning period covered by this Science Strategy a significant research capability in cetacean biology will be developed to provide scientific data to support Australia's policy position in the International Whaling Commission. Scientific research to contribute to other international treaties is also required such as the Agreement on the Conservation of Albatrosses and Petrels (ACAP), the Convention on the Conservation of Antarctic Seals (CCAS), and will contribute to international research programs such as Southern Ocean GLOBEC (Global Ocean Ecosystem Dynamics) and the Census of Marine Life (CoML). As yet little is known about the effects of climate change and natural variability on the ecosystems of the Southern Ocean, which will be addressed by the Ice Ocean Atmosphere and Climate program. Models of biological productivity at all trophic levels will enable predictions to be made of the effects of variability and change on the region's marine ecosystems.

How are Southern Ocean ecosystems structured?

King Penguins landing, Heard Island. Photo: Nick Gales

CCAMLR's Convention includes objectives that demand that the requirements of the 'dependent and related species' as well as the well-being of the harvested species be taken into account when determining fishing levels. Thus commercial harvesting must not adversely impact upon natural stocks of predators of the target species and other ecosystem effects, such as by-catch need to be minimised. The demands this makes on ecosystem modellers are substantial because a more detailed knowledge on critical energy flows within the Southern Ocean's ecosystems to ensure catch limits are correctly set is needed. Emphasis will be placed on understanding the ecosystems supported by the current target species – krill, icefish and toothfish – and the food chains leading to their predators. Because whales are significant predators in marine ecosystems, an understanding of population dynamics and trophic biology is required to add veracity to existing models of ecosystem function. A further objective of the program will be to develop a program of cetacean research that enhances and strengthens our quantitative studies of Southern Ocean ecosystem dynamics.

Deploying a net from the trawl deck of the Aurora Australis. Photo: Steve Nicol

What are the limits for sustainable harvesting of the Southern Ocean without damaging ecosystems?

CCAMLR has relied upon a precautionary approach to regulate catches at levels where the best available scientific information indicates that there will be no lasting damage to the harvested species or to the ecosystem. Three main strands of research will provide better predictions and thus greater accuracy for these estimates. Firstly refinement of methods to estimate the abundance of natural stocks of harvested, or potentially harvested species (fish, squid, crabs and krill) are needed. Secondly, a better understanding of the key biological parameters of harvested species and thirdly through the development of ecosystem models that better reflect observed complexity are required. Research under this program will continue to focus clearly on the support of Australia's policy position in CCAMLR and will incorporate research, monitoring and modelling studies.

What are the main sources of natural and anthropogenic variability of the Southern Ocean and how do they exert their effects on biological productivity?

Expeditioners on the helipad of the Aurora Australis. Photo: Steve Nicol

Research conducted in the Ice, Oceans Atmosphere and Climate priority program will examine natural changes in the Southern Ocean occurring annually, inter-annually, over decades and centuries, and on even longer time scales. The Southern Ocean is also likely to be subject to anthropogenic forcing. Research is starting to describe variations in the physical and biological environment over shorter time scales but these observations must be extended, and be applied to the longer time scales principally through modelling studies. Variations in the winter extent of sea ice are thought to have profound effects on biological productivity, such as algal growth and the reproduction of Antarctic krill, with subsequent flow-on effects through the food web. Research and modelling studies can clarify these linkages. Global warming and other environmental changes can be expected to have a major direct effect on the region's physical systems and it is thus important to develop a capacity to understand the likely consequences of these changes on the marine ecosystems so that their effects can be taken into account when developing management strategies. Interdisciplinary research into the effects of variability and change in the physical environment of the Southern Ocean and their effects on the region's biological systems (see The Antarctic Climate & Ecosystems CRC: a truly collaborative partnership) is an integral part of the focus of the Antarctic Marine Ecosystems theme of the ACE-CRC.