What are Australian marine ecosystems?

Australian marine ecosystems are some of the largest and most biologically diverse in the world, surrounding a continent with the third-largest exclusive economic zone on the planet at about 8.2 million square kilometres. They include coral reefs, kelp forests, seagrass meadows, mangrove forests, deep ocean trenches, and Antarctic waters.

The Great Barrier Reef on the Queensland coast and Ningaloo Reef off the Western Australian coast are the two most internationally recognised reef systems. The Great Barrier Reef stretches 2,300 kilometres and contains more than 2,900 individual reefs. Ningaloo, listed as World Heritage in 2011, is the world's largest fringing reef and the easiest place on Earth to swim with whale sharks. Lord Howe Island and the Houtman Abrolhos host the world's southernmost coral reefs.

South of the tropics, the Great Southern Reef is a connected system of rocky reefs, kelp forests, and seagrass beds running 8,000 kilometres along the temperate southern coastline from Kalbarri in Western Australia to the northern New South Wales border, taking in Tasmania. About 70 per cent of the species in the Great Southern Reef are found nowhere else, including leafy seadragons, giant cuttlefish, and the southern bluefin tuna stock.

Australian marine ecosystems support major commercial fisheries including rock lobster, prawns, salmon, abalone, scallops, and tuna. The Australian Fisheries Management Authority oversees federal fisheries, while state agencies manage inshore stocks. About 40 per cent of Australia's exclusive economic zone is now within the national network of Australian Marine Parks, making it one of the largest networks of marine protected areas in the world. Climate change, ocean warming, marine heatwaves, and acidification are reshaping these ecosystems, with mass coral bleaching events and the loss of giant kelp forests in eastern Tasmania the clearest signs.