Great Barrier Reef, Queensland, Australia. The Great Barrier Reef (GBR), located off the coast of Queensland in northeastern Australia, is the largest living thing on Earth and can even be visible from outer space. The 2,300 km long ecosystem, which covers an area of approximately 344,400 km2, is comprised of thousands of reefs and hundreds of islands made of over 600 types of hard and soft coral (as shown in the photograph). It is home to around 1,500 species of fish, 4,000 species of molluscs (e.g., clams, snails, cuttlefish, nudibranchs), 1,500 species of sponge, 800 species of echinoderms (e.g., starfish, sea cucumbers, sea urchins), 30 species of marine mammals (e.g., whales, dolphins, dugong), and six of the world's seven species of marine turtles.
Considered one of the seven natural wonders of the world, the Great Barrier Reef dwarfs the next two largest barrier reef systems on Earth (i.e. the Mesoamerican Barrier Reef System at approximately 1,125km long and the Florida Reef Tract at about 270km long). In October of 1981, theGBRgained a World Heritage listing that included the entire Great Barrier Reef Marine Park area. Within its confines, various marine ecosystems are protected, such as coral reefs, seagrass beds, mangrove forests and nurseries, sand and vegetated cayes, algal fields, sponge gardens, inter-reefal communities, and deep oceanic regions. (Photograph taken April 2016 by Chris Makowski, Coastal Education and Research Foundation, Coconut Creek, Florida, U.S.A.)