The marine biome is essentially all of the world’s connected salt and brackish waters, including the oceans, seas, coral reefs and estuaries. Most of the planet’s life lives in the marine biome, as it covers approximately 75 percent of the Earth’s surface. The marine biome contains the largest living creatures, such as whales and giant fish, as well as many of the strangest, such as sea spiders and sea horses.
In addition to the numerous species that spend their entire life living in oceans and estuaries, many animals live in terrestrial biomes, but venture into the marine biome to obtain resources. For example, polar bears swim so much in the ocean that their scientific name is Ursus maritimus. Many birds regularly pluck fish and squid from marine areas and the marine iguana of the Galapagos Islands feed on algae growing underwater.
Many of the world’s whales and sharks are very large, but blue whale are the largest animals to ever inhabit the planet, as they sometimes exceed 200 tons in weight. However, these behemoths reach these large sizes by consuming some of the smallest prey in the world – primarily plankton and krill.
Because it is difficult to explore, the marine biome likely holds many species not yet recognized or explored.