The Great Barrier Reef

Coral reefs

The Great Barrier Reef is not technically a single reef, but a network comprising over 3,000 individual reefs. Coral reefs come in a wide range of different types, from the long, narrow ribbon reefs that form a barrier on the outer-edge of the northern Great Barrier Reef to fringing reefs that surround continental islands. While many of these reefs reach the sea surface, new reefs hidden below the surface continue to be discovered. The types of creatures living on different reefs varies depending on the habitat: inshore reefs can be exposed to high levels turbidity and fresh water, particularly during the wet season when rivers that flow into the Great Barrier Reef are in flood. In contrast, life on the outer barrier must be capable of dealing with the full force of oceanic swells rolling in from the Pacific Ocean.

Islands and Cays

The Great Barrier Reef World Heritage Area contains over 900 islands, ranging from large continental islands such Hinchinbrook Island to small, unvegetated coral cays submerged at high tides. The rocky, densely vegetated continental islands form part of the Australian continent that have been separated from the mainland by rising sea levels since the last ice age. In contrast, coral cays are composed of material generated by the skeletons of corals and other calcifying flora and fauna. Over time, larger coral cays may be colonised by a range of plants and animals. Great Barrier Reef islands are important breeding sites for many seabirds, as well as turtles and other species.

Coastal Ecosystems

The coastal waters of the Great Barrier Reef ecosystem are generally turbid and influenced by inflow from rivers, which are not ideal conditions for coral growth. However, coastal areas support important habitats, including mangrove forests and seagrass beds, that are home to a range of species including fish, sea snakes and dugongs.

Open Ocean and Deep Sea Ecosystems

Beyond the reefs of the outer barrier, the seafloor plunges to depths over 1,000 metres. Open ocean ecosystems are inhabited by species including marlin, tuna, pelagic sharks and whales. The margin of the Australian continent is scarred by huge canyon systems, which support unusual communities of invertebrates such as brachiopods and crinoids or ‘sea lilies’ - groups which dominated marine ecosystems before the time of the dinosaurs. These ecosystems exist in perpetual darkness, and despite their tropical latitude, water temperatures are only a few degrees above freezing.

Human History

The human history of the Reef is no less intriguing. First Nations people have known the Reef since time immemorial. We are constantly learning from First Nations people about their deep history and continuing connection to land and sea Country. European interactions over the last 500 years have left physical reminders of the dangers in navigating the reef, such as infamous shipwrecks like HMS Pandora and SS Yongala. Human interaction with the reef is diverse, detailed and unique.