These species can either be woody or herbaceous, with the woody being situated mainly in the northern islands and the herbaceous in the southern islands. There are 2,195 known plant species in the reef, 3 of those being endemic. Most nesting sites for birds are on islands in the northern and southern regions of the reef, attracting 1.4 to 1.4 million birds, including 22 species of seabirds and 32 species of shorebirds. These species include the green sea turtle, leatherback sea turtle, hawksbill turtle, loggerhead sea turtle, flatback turtle and the Olive Ridley. Fifteen species of seagrass in beds attract the dugongs and turtles, with six species of sea turtles choosing the reef as its breeding spot.
Thirty species of crustaceans have been recorded in the reef, such as the dwarf minke whale, Indo-Pacific humpback dolphin and the humpback whale. More than 1,500 species of fish inhabit the reef, such as wrasses, damselfish, triggerfish, angelfish, rays and sharks. The Great Barrier Reef is a biodiversity hotspot, housing at least 450 species of hard coral aa well as anemones, sponges, worms, gastropods, lobsters, crayfish, prawns and crabs. The remains of an ancient barrier reef, similar to the Great Barrier reef, can be found in the Kimberly, Western Australia.
km, most of which has grown on top of limestone platforms that date to the Pleistocene phase of reef growth. Shallow water reefs cover an area of 20,679 sq.
The corals then grew over these submerged hills to form the present cays and reefs. The continental islands, which were then hills of the coastal plain, became submerged as the sea levels continued to rise. As the sea level rose 20,000 years ago, corals were able to grow higher on the newly submerged maritime margins of the hills of the coastal plain. The calcareous remains of the coral polyps and hydrocorals form the reef framework, while the coralline algae bind these remains together. The reefs however share a common origin: the skeletons and skeletal waste of a mass of living marine organisms. According to the Australian Institute of Marine Sciences, current reef growth began at the Last Glacial Maximum. The Great Barrier Reef Marine Park Authority (GBRMPA) estimates that complete reef structures date back to 600,000 years ago. The land forming the substrate of the reef was originally a coastal plain formed from the erosion of the East Australian Cordillera. The sea level then lowered 10 million years ago, distancing the reef’s substrate from suspended sediments that were inhibiting the coral growth. However, when Queensland was still in tropical water 24 million years ago, the erosion of the East Australian Cordillera created a sedimentation regime, making conditions unsuitable for coral growth. Coral reefs began growing only after the Coral Sea basin was formed. At the same time, volcanic eruptions in Queensland led to central and shield volcanoes and basalt flows, some of which became high islands. The drainage divide in Queensland was moved about 400 km inland after eastern Australia experienced a tectonic uplift, a process where a piece of land increases in elevation due to plate tectonics. The plate tectonic theory states that Australia has moved north during the Cenozoic Era.