Which Australian island has the world's southernmost coral reef?

Lord Howe Island has the world’s southernmost true coral reef ecosystem. It lies in the Tasman Sea, where warm currents allow reef-building corals to survive farther south than at other comparable sites.

The island’s reef environment is unusual because it combines tropical and temperate marine species. The southward-flowing East Australian Current carries warm water toward Lord Howe Island, helping sustain corals and supporting a diverse fish and invertebrate community. A lagoonal reef and fringing reefs occur around the island, while a larger barrier reef protects the western lagoon.

The island is not a typical tropical coral destination. Its reefs sit near the climatic limit for coral growth, so they coexist with extensive algae beds and temperate open-ocean habitats. Lord Howe Island’s geographic position also makes its marine life distinctive: more than 400 inshore fish species have been recorded, including species found nowhere else.