Coral Sea Islands & Reefs

Bougainville Reef Located east of Australia's Great Barrier Reef and some distance off the continental shelf are a large number of reef formations and small sand cays scattered across the Coral Sea. Those in the west belong to Australia (some of which form an external territory of Australia), those in the east from a dependency of the French territory of New Caledonia, while those in the northeast belong to Papua New Guinea.

The reefs of the western Coral Sea can be split in to three separate groups. In the far north are the Portlock Reefs, Ashmore Reef, the Eastern Fields and many smaller reef structures, some of which lie closer to Papua New Guinea than they do to Australia. In the central region a large submarine feature known as the Coral Sea Shelf (or Queensland Plateau) contains most of the reefs and forms the core of the Australian Coral Sea Islands External Territory. It stretches from Osprey Reef in the north to the Saumarez Reefs in the south. It contains the largest reef formation to be found in the western Coral Sea — the 2,500 km², largely submerged Lihou Reef. Found also in this central region are the Coringa Islets, Herald Cays, Magdelaine Cays, Tregosse Reefs & Diamond Islets, Flinders Reefs, Bougainville Reef, Holmes Reef, Flora Reef, Malay Reef, Abington Reef, Dart Reef, Moore Reef, Heralds Surprise, Dianne Bank and the Willis Islets. The third group of reefs are those that lie farther east and south, located off the Coral Sea Shelf; these include Cato Reef, the Frederick Reefs, Kenn Reef, Wreck Reefs and the distant Mellish Reef.

Many maps — both modern and old — show the presence of a fairly large island, known as Île de Sable, in the eastern waters of the Coral Sea. The island is said to be located midway between the Îles Chesterfield and Grande Terre (New Caledonia), and northwest from Nereus Reef. There are, in fact, no islands in this region. The existence of Île de Sable is more than likely a misreported observation of a submerged reef or bank.

Ecologically, some of the most important groups in the Coral Sea lie around 440 km east of Cairns, where three reef systems are protected as the Coringa-Herald National Nature Reserve (8,860 km²), and a fourth as the Lihou Reef Nature Reserve (8,440 km²).

Coringa-Herald consists of 6 small cays, grouped into three pairs: the Herald Cays — South West and North East Cays; the Coringa Islets — South West and Chilcott Islet; and the Magdelaine Cays — North West Islet and South East Cay. Each has a fringing coral reef and range in size from 0.16 to 0.37 km², covering 1.24 km² in total. South-East Magdelaine Cay is the largest measuring about 1,200 m by 500 m. Most of the islets and cays are composed of sand, rocks and coral rubble, that rise no higher than 5 m above sea level. All the cays, except for North West Cay in the Magdelaine Cays are vegetated with grasses and herbs, while North East Herald Cay and South East Magdelaine Cay have forests of Pisonia grandis and Cordia, providing an important habitat for nesting seabirds.

At the eastern side of the Coral Sea are a number of reefs and cays that form the Chesterfield Group, located around 600 km west of the northern tip of the French Overseas Territory of New Caledonia. They include the Îles Chesterfield and Bampton Reefs complex which together form a large open-atoll like structure of submerged reefs, and small sand cays. To the south are the Bellona Reefs and Observatory Cay. Farther east still, sitting on the southern edge of the Landsdowne Bank, halfway between the Bellona Reefs and New Caledonia is the small and isolated Fairway Reef.

The reefs and cays of the eastern Coral Sea are extremely remote and as a result have been little explored. They are currently protected as minor reserves, providing habitat to nesting seabirds, green turtles and endemic gastropod species.