Fiji comprises about 844 islands and islets, and is thought to include over 10,000 km2 of reef. The Fiji Barrier Reef marine ecoregion includes a diversity of marine habitats, including estuaries, mangrove communities, sea grass beds, macroalgal assemblages, and sand and mudflats. An abundance of coral life thrives throughout in the form of fringing, platform, patch, barrier, oceanic ribbon, atolls, near atolls, and drowned coral reefs. Research has recorded close to 300 species of coral, over 475 species of molluscs, and almost 2,000 fish species, although the actual number of species of fish and coral is likely to be much greater. Fiji's coral reefs are thus rightfully recognized as being world class in ecological significance.