High Quality Content by WIKIPEDIA articles! Heron Island is a coral cay located near the Tropic of Capricorn in the southern Great Barrier Reef, 72 km north-east of Gladstone, Queensland, Australia, and 539 km north of the state capital Brisbane. The island is situated on the leeward (western) side of Heron Reef, a fringing platform reef of significant biodiversity, supporting around 900 of the 1,500 fish species and 72% of the coral species found on the Great Barrier Reef.