Open ocean in the context of "Marine habitats"

A marine habitat is a habitat that supports marine life. Marine life depends in some way on the saltwater that is in the sea (the term marine comes from the Latin mare, meaning sea or ocean). A habitat is an ecological or environmental area inhabited by one or more living species. The marine environment supports many kinds of these habitats.

Marine habitats can be divided into coastal and open ocean habitats. Coastal habitats are found in the area that extends from as far as the tide comes in on the shoreline out to the edge of the continental shelf. Most marine life is found in coastal habitats, even though the shelf area occupies only seven percent of the total ocean area. Open ocean habitats are found in the deep ocean beyond the edge of the continental shelf.

Ocean deoxygenation is the reduction of the oxygen content in different parts of the ocean due to human activities. There are two areas where this occurs. Firstly, it occurs in coastal zones where eutrophication has driven some quite rapid (in a few decades) declines in oxygen to very low levels. This type of ocean deoxygenation is also called dead zones. Secondly, ocean deoxygenation occurs also in the open ocean. In that part of the ocean, there is nowadays an ongoing reduction in oxygen levels. As a result, the naturally occurring low oxygen areas (so called oxygen minimum zones (OMZs)) are now expanding slowly. This expansion is happening as a consequence of human caused climate change. The resulting decrease in oxygen content of the oceans poses a threat to marine life, as well as to people who depend on marine life for nutrition or livelihood. A decrease in ocean oxygen levels affects how productive the ocean is, how nutrients and carbon move around, and how marine habitats function.

As the oceans become warmer this increases the loss of oxygen in the oceans. This is because the warmer temperatures increase ocean stratification. The reason for this lies in the multiple connections between density and solubility effects that result from warming. As a side effect, the availability of nutrients for marine life is reduced, therefore adding further stress to marine organisms.

The great white shark (Carcharodon carcharias), also known as the white shark, white pointer, or simply great white, is the largest living macropredatory shark and fish. It is a mackerel shark and closely related to the mako sharks, the porbeagle and the salmon shark. It is a robustly built species with a grayish upper-side and a white underside, the latter feature gives it its name. Females average 4.6 to 4.9 m (15 to 16 ft) while males average 3.4 to 4.0 m (11 to 13 ft). Females typically weigh 1,000–1,900 kg (2,200–4,200 lb) compared to 680–1,000 kg (1,500–2,200 lb) for males. They are estimated to reach a length close to 6.1 m (20 ft) and a weight of over 2,494.9 kg (5,500 lb). The shark has approximately 300 triangular, serrated teeth that are continuously replaced. Its massive, fatty liver can reach over a quarter of its body weight and provides buoyancy and energy. White sharks are unusual among fish in that they are warm-blooded, allowing them to remain active in colder waters.

White sharks inhabit tropical and temperate ocean waters around the world and can be found both along the coast and further out to sea. Populations are most concentrated at the Pacific and Atlantic sides of North America and in the waters of southern Africa and Oceania. They are a highly migratory species, traveling between the coast and open ocean and even between continents. The great white shark is an apex predator and preys on marine mammals such as pinnipeds and dolphins, as well as fish, including other sharks, and cephalopods. It is also a prolific scavenger of whale carcasses. Despite its apex predator status, the species itself is sometimes preyed on by orcas. White sharks are generally solitary but gather in aggregations, particularly at feeding sites. They may communicate and establish dominance hierarchies with body language. Reproductive behavior in the species is less understood, but it is known to be ovoviviparous; with pups hatching from eggs within the female, who gives live birth after 12 months. Juvenile white sharks typically inhabit shallower water and cannot eat marine mammals until they reach around 3 m (9.8 ft).

A brown-water navy or riverine navy, in the broadest sense, is a naval force capable of military operations in inland waters (rivers, lakes and inland seas) and nearshores. The term originated in the United States Navy during the American Civil War, when it referred to Union forces patrolling the muddy Mississippi River, and has since been used to describe the small gunboats and patrol boats commonly used in rivers, along with the larger "mother ships" that supported them.

Brown-water navies are typically only used for patrolling and enforcing internal waters, in contrast to blue-water navies, which can independently conduct operations in the open oceans and project power far offshore. Green-water navies, which operate mainly in brackish estuaries, bays and shallow seas not too far off coasts (typically within the bounds of exclusive economic zones), fill the operational gap between brown-water and blue-water navies.

A green-water navy is a maritime force that is capable of operating in its state's littoral zones and has limited competency to operate in the surrounding marginal seas. It is a relatively new term, and has been created to better distinguish, and add nuance, between two long-standing descriptors: blue-water navy (deep waters of open oceans) and brown-water navy (inland waters, littoral and shallow seas).

As a non-doctrinal term with no concrete legal or political definition, it can be used in several different ways. It originated with the United States Navy, who use it to refer to the portion of their fleet that specializes in offensive operations in coastal waters. Nowadays such ships rely on stealth or speed to avoid destruction by shore batteries or land-based aircraft.

The oceanic zone is typically defined as the area of the ocean lying beyond the continental shelf (e.g. the neritic zone), but operationally is often referred to as beginning where the water depths drop to below 200 metres (660 ft), seaward from the coast into the open ocean with its pelagic zone.

It is the region of open sea beyond the edge of the continental shelf and includes 65% of the ocean's completely open water. The oceanic zone has a wide array of undersea terrain, including trenches that are often deeper than Mount Everest is tall, as well as deep-sea volcanoes and basins. While it is often difficult for life to sustain itself in this type of environment, many species have adapted and do thrive in the oceanic zone.