Marine

The biome of the open and coastal ocean, covering roughly seventy percent of the Earth's surface and, by volume, the largest habitable space on the planet. It is not one uniform environment but a stack of zones defined by light and pressure, from the sunlit surface layer where photosynthetic plankton form the base of nearly every marine food web, down through the twilight and midnight zones to the deep sea floor, plus coastal shallows such as coral reefs, among them the Great Barrier Reef, that concentrate a disproportionate share of marine biodiversity. Large-bodied filter feeders such as the blue whale and wide-ranging predators alike depend on the productivity of this biome's surface waters.