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Marine biology studies species that live in marine habitats. Most of the Earth's surface is covered by ocean, which is the home to marine life. Oceans average nearly four kilometers in-depth and are fringed with coastlines that run for about 360,000 kilometres. [4] [5] Marine biology can be contrasted with biological oceanography.
Marine life, sea life, or ocean life is the plants, animals, and other organisms that live in the salt water of seas or oceans, or the brackish water of coastal estuaries. At a fundamental level, marine life affects the nature of the planet. Marine organisms, mostly microorganisms, produce oxygen and sequester carbon.
Most oceanic species (78 per cent, or 44 per cent of all fish species), live near the shoreline. These coastal fish live on or above the relatively shallow continental shelf. Only 13 per cent of all fish species live in the open ocean, off the shelf. Of these, 1 per cent are epipelagic, 5 per cent are pelagic, and 7 per cent are deep water. [16]
Marine ecosystems are the largest of Earth 's aquatic ecosystems and exist in waters that have a high salt content. These systems contrast with freshwater ecosystems, which have a lower salt content. Marine waters cover more than 70% of the surface of the Earth and account for more than 97% of Earth's water supply [1][2] and 90% of habitable ...
The ocean is known to be the habitat of over 230,000 species, but may hold considerably more – perhaps over two million species. [18] Yet, the ocean faces many environmental threats, such as marine pollution, overfishing, and the effects of climate change. Those effects include ocean warming, ocean acidification and sea level rise.
Fish species are roughly divided equally between freshwater and marine (oceanic) ecosystems; there are some 15,200 freshwater species and around 14,800 marine species. [27] Coral reefs in the Indo-Pacific constitute the center of diversity for marine fishes, [ 28 ] whereas continental freshwater fishes are most diverse in large river basins of ...
Life histories connect disparate ecosystems; species that live at the surface during one life history stage may occupy the deep sea, benthos, reefs, or freshwater ecosystems during another. A diversity of fish species utilize the ocean's surface, [119] either as adults or as nursery habitat for eggs and young. In contrast, species floating on ...
Balaenoptera sibbaldii Sars 1875. The blue whale (Balaenoptera musculus) is a marine mammal and a baleen whale. Reaching a maximum confirmed length of 29.9 m (98 ft) and weighing up to 199 t (196 long tons; 219 short tons), it is the largest animal known ever to have existed. [a] The blue whale's long and slender body can be of various shades ...