Osprey Reef Osprey Reef Osprey Reef is a submerged atoll in the Coral Sea, northeast of Queensland, Australia. It is part of the Northwestern Group of the Coral Sea Islands. Osprey Reef is roughly oval in shape, measuring , and covers around . It has a perimeter of . The central lagoon is only deep. The reef sits atop a seamount in deep water. It is an isolated location some from other reefs. The almost vertical reef walls, which rise from a depth of about , are home to a dwarf form of "Nautilus pompilius" that is isolated from other nautilus populations
Coral reef that build reefs. In the early Cambrian period, "Archaeocyatha" sponges were the world's first reef-building organisms, and sponges were the only reef-builders until the Ordovician. Sclerosponges still assist corals building modern reefs, but like coralline algae are much slower-growing than corals and their contribution is (usually) minor. In the northern Pacific Ocean cloud sponges still create deep-water mineral-structures without corals, although the structures are not recognizable from the surface like tropical reefs. They are the only extant organisms known to build reef-like structures in cold water. In "The Structure and Distribution of Coral Reefs", published in 1842, Darwin described how