Great South Australian Coast Upwelling System compared to the Great Barrier Reef as world marine natural wonder
The three centres – Bonney Coast, Kangaroo Island and eastern Eyre Peninsula – of the Great South Australian Coastal Upwelling System. At left: Blue whales are attracted to the Bonney Upwelling by krill in its nutrient-rich waters.
The Great South Australian Coastal Upwelling System has been rated alongside the Great Barrier Reef as one of Australia's natural wonders. The ecosystem extends over about 800 kilometres of the eastern Great Australian Bight from Ceduna, South Australia, to Portland, Victoria.
The Great South Australian Coastal Upwelling System has nutrient-enriched water coming from depths exceeding 300 metres that attracts blue whales and supports rich fisheries. The upwelling, from November to May, is caused by seasonal southeast winds forcing coastal waters offshore and drawing cold nutrient-rich waters from the ocean floor.
Key upwelling centres form in three Southern Australian locations: the Bonney Coast, Kangaroo Island and Eyre Peninsula.
The Bonney Upwelling is the largest and most predictable, stretching from Robe, South Australia, to Portland, Victoria, as a narrow 20km continental shelf dropping to the continental slope where deep water is funneled to the surface through submarine canyons. During upwelling, surface chlorophyll a increases tenfold, indicating abundant phytoplankton blooms, bringing swarms of krill that attract blue whales.
The Bonney Upwelling region is one of 12 identified blue whale feeding sites worldwide, with an estimated 100 visiting the area each year. In 2002, the Bonney Upwelling was listed as critical habitat “requiring effective protection from user impacts” – particularly natural gas exploration – under Australia’s environment protection laws.
Upwelling at Kangaroo Island and Eyre Peninsula is different, with the continental shelf (up to 100km) generally much wider than the Bonney Coast. Water isn’t drawn directly from the seafloor but follows a chain of processes starting in the deep submarine canyons of the Murray Canyon Group, south of Kangaroo Island, where localised subsurface upwelling brings a pool of cold water from the abyssal plains up to the continental shelf. This dense-water Kangaroo Island pool, drifts along the shelf bottom just offshore of Kangaroo Island and Eyre Peninsula.
Southern rock lobsters (crayfish) and trawling are the most important fishing industries in the Bonney Upwelling, while upwelling off the Eyre Peninsula supports a large sardine fishery, operating chiefly out of Port Lincoln. Other marine life thriving in the upwelling includes filter feeders like sponges, bryozoans and corals. These feed predators such as seabirds, fishes, Australian fur seals and penguins.
The upwelling is important in the life cycle of juvenile southern bluefin tuna that feed on sardines and anchovies. Dead organisms that fall to the continental shelf support crayfish and giant crabs.
The abundance of the Great South Australian Coastal Upwelling System ecosystem rivals some of the world’s most productive upwelling centres, such as those offshore Peru, California and Namibia.