Masthead Island is a coral cay located in the southern Great Barrier Reef, 60 kilometres northeast of Gladstone, Queensland. The island is a protected area and forms part of Capricornia Cays National Park. Masthead Island is one of the most undisturbed cays in the national park because human and feral animal impacts have been rare. The cay covers an area of and is surrounded by a coral reef that is partially exposed at low-tide. It is part of the Capricornia Cays Important Bird Area.
The island is closed to the public from mid-October to Easter to protect nesting seabirds and turtle hatchlings. At other times the island is open for camping, however there are no facilities provided.
Masthead Island was the shooting location for the 2010 film Uninhabited.
Geomorphology and landscape
Beach rock is well developed along the southern beach and an occurrence of older beach rock is situated some distance from the beach on the north western corner of the cay. Vegetation is similar to that occurring on Heron island.
The vegetation and tree heights and trunk diameters can be used to interpret coral cay dynamics and thus the growth of the cay. It is postulated that the 'nucleus' old growth Pisonia grandis forest pattern (with trees up to 23m high and 2.4m trunk diameter) is in the central western part of this cay and is able to provide identification of the older forested sections of the island.
The Capricorn and Bunker Cays form part of a distinct geomorphic province at the southern end of the Great Barrier Reef. The cays and their reefs lie on the western marginal shelf, and are separated from the mainland by the Curtis Channel. The cays are not generally visible from the mainland, although Masthead Island may be viewed from Mount Larcom on a clear day.
Geologically the cays are young, having developed during the Holocene period, they are mostly around 5000 years old. The sea level was much lower during the last Ice Age (at the end of the Pleistocene period) and the coastal plain on which today's reefs and cays developed was completely exposed. Early in the Holocene (around 10,000 years ago) the sea level began to rise, until it stabilised at its present level around 6000 years ago. Once the sea level stabilised, it was possible for reef flats to expand and provide potential sites for the formation of cays.
Masthead Island Reef is an Elongate Platform Reef.
The coral cay is a Vegetated sand cay The sand cay is located to the lee of their reef flat.
History
The explorer Matthew Flinders discovered and named Masthead Island in 1802. Masthead was incorporated into the Capricornia Cays National Park in 1994.
Ecology
Flora
The centre of the island is dominated by a dense forest of Pisonia (both birdcatcher pisonia and Pisonia grandis) vegetation while pandanus, velvet soldierbush and she-oaks are found around the island fringes.
A total of 50 taxa of vascular plants have been recorded since first collections in 1909 including 7 naturalised exotic plant species.
The May 1998 census records 37 native and 3 naturalised plant species. The majority of plant species are dispersed by sea (52%) and seabirds (38%).
Thirteen percent (27ha) of the total Pisonia grandis closed forest in Australia is located on Masthead Island.
Fauna
Masthead Island is an internationally important rookery for green and loggerhead turtles, who come ashore to lay eggs on the island's beaches during spring and summer, from late October to late February. This is a major breeding site for the turtles, the fifth most important in the South Pacific.
The cay also supports a diverse seabird population. The black noddy and wedge-tailed shearwater are most common, while the black-naped tern, bridled tern, Capricorn silvereye, roseate tern and silver gull are also regularly seen on the island.
The coral reef around the cay is a habitat for a vast array of marine life, the most common including angelfish, parrotfish, butterflyfish, sweetlips, batfish, sting rays, bronze whalers, sea snakes and stonefish.
Masthead was the discovery ground of an entirely new species of fish, the Masthead Island Pipefish.
Pests
Currently, weeds are a problem on some of the cays where the vulnerability of cays to environmental weeds has been well shown on Masthead with prickly pear, introduced from the Main Land, and was well established over the entire cay in the 1970s . Weed control programs have been implemented to eradicate introduced plants with a significant reduction of Opuntia on Masthead Island.