1.
Marine habitats
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The marine environment supplies many kinds of habitats that support marine life. Marine life depends in some way on the saltwater that is in the sea, a habitat is an ecological or environmental area inhabited by one or more living species. 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 habitats, even though the shelf area occupies only seven percent of the total ocean area. Open ocean habitats are found in the ocean beyond the edge of the continental shelf. Alternatively, marine habitats can be divided into pelagic and demersal zones, pelagic habitats are found near the surface or in the open water column, away from the bottom of the ocean. Demersal habitats are near or on the bottom of the ocean, an organism living in a pelagic habitat is said to be a pelagic organism, as in pelagic fish. Similarly, a living in a demersal habitat is said to be a demersal organism. Pelagic habitats are shifting and ephemeral, depending on what ocean currents are doing. Marine habitats can be modified by their inhabitants, some marine organisms, like corals, kelp, mangroves and seagrasses, are ecosystem engineers which reshape the marine environment to the point where they create further habitat for other organisms. In contrast to terrestrial habitats, marine habitats are shifting and ephemeral, swimming organisms find areas by the edge of a continental shelf a good habitat, but only while upwellings bring nutrient rich water to the surface. Shellfish find habitat on sandy beaches, but storms, tides, the presence of seawater is common to all marine habitats. Beyond that many other things determine whether a marine area makes a good habitat, the ocean occupies 71 percent of the world surface, averaging nearly four kilometres in depth. There are five major oceans, of which the Pacific Ocean is nearly as large as the rest put together, coastlines fringe the land for nearly 380,000 kilometres. Marine habitats can be divided into pelagic and demersal habitats. Pelagic habitats are the habitats of the water column, away from the bottom of the ocean. Demersal habitats are the habitats that are near or on the bottom of the ocean, an organism living in a pelagic habitat is said to be a pelagic organism, as in pelagic fish. Similarly, a living in a demersal habitat is said to be a demersal organism
2.
Wild fisheries
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A fishery is an area with an associated fish or aquatic population which is harvested for its commercial value. Fisheries can be marine or freshwater and they can also be wild or farmed. Wild fisheries are sometimes called capture fisheries, the aquatic life they support is not controlled in any meaningful way and needs to be captured or fished. Wild fisheries exist primarily in the oceans, and particularly around coasts and they also exist in lakes and rivers. Issues with wild fisheries are overfishing and pollution, significant wild fisheries have collapsed or are in danger of collapsing, due to overfishing and pollution. Overall, production from the wild fisheries has levelled out. As a contrast to wild fisheries, farmed fisheries can operate in sheltered waters, in rivers, lakes and ponds. Farmed fisheries are technological in nature, and revolve around developments in aquaculture, farmed fisheries are expanding, and Chinese aquaculture in particular is making many advances. Nevertheless, the majority of fish consumed by humans continues to be sourced from wild fisheries, as of the early 21st century, fish is humanitys only significant wild food source. This can be contrasted with 59.9 million tonnes produced in fish farms, worldwide, freshwater lakes have an area of 1.5 million square kilometres. Saline inland seas add another 1.0 million square kilometres, there are 28 freshwater lakes with an area greater than 5,000 square kilometres, totalling 1.18 million square kilometres or 79 percent of the total. Pollution is the introduction of contaminants into an environment, land run-off and industrial, agricultural, and domestic waste enter rivers and are discharged into the sea. Pollution from ships is also a problem, Marine debris is human-created waste that ends up floating in the sea. Oceanic debris tends to accumulate at the centre of gyres and coastlines, eighty percent of all known marine debris is plastic - a component that has been rapidly accumulating since the end of World War II. Discarded plastic bags, six rings and other forms of plastic waste which finish up in the ocean present dangers to wildlife. Aquatic life can be threatened through entanglement, suffocation, and ingestion, nurdles, also known as mermaids tears, are plastic pellets typically under five millimetres in diameter, and are a major contributor to marine debris. They are used as a raw material in manufacturing, and are thought to enter the natural environment after accidental spillages. Nurdles are also created through the weathering of larger plastic debris
3.
Hydrothermal vent
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A hydrothermal vent is a fissure in a planets surface from which geothermally heated water issues. Hydrothermal vents are found near volcanically active places, areas where tectonic plates are moving apart, ocean basins. Hydrothermal vents exist because the earth is both active and has large amounts of water on its surface and within its crust. Common land types include hot springs, fumaroles and geysers, under the sea, hydrothermal vents may form features called black smokers. Chemosynthetic bacteria and archaea form the base of the chain, supporting diverse organisms, including giant tube worms, clams, limpets. Active hydrothermal vents are believed to exist on Jupiters moon Europa, and Saturns moon Enceladus, Hydrothermal vents in the deep ocean typically form along the mid-ocean ridges, such as the East Pacific Rise and the Mid-Atlantic Ridge. These are locations where two plates are diverging and new crust is being formed. The proportion of each varies from location to location, in contrast to the approximately 2 °C ambient water temperature at these depths, water emerges from these vents at temperatures ranging from 60 to as high as 464 °C. Due to the hydrostatic pressure at these depths, water may exist in either its liquid form or as a supercritical fluid at such temperatures. The critical point of water is 375 °C at a pressure of 218 atmospheres, however, introducing salinity into the fluid raises the critical point to higher temperatures and pressures. The critical point of seawater is 407 °C and 298.5 bars, accordingly, if a hydrothermal fluid with a salinity of 3.2 wt. % NaCl vents above 407 °C and 298.5 bars, furthermore, the salinity of vent fluids have been shown to vary widely due to phase separation in the crust. The critical point for lower salinity fluids is at lower temperature and pressure conditions than that for seawater, for example, a vent fluid with a 2.24 wt. % NaCl salinity has the point at 400 °C and 280.5 bars. Thus, water emerging from the hottest parts of some hydrothermal vents can be a supercritical fluid, examples of supercritical venting are found at several sites. Sister Peak vents low salinity phase-separated, vapor-type fluids, sustained venting was not found to be supercritical but a brief injection of 464 °C was well above supercritical conditions. A nearby site, Turtle Pits, was found to vent low salinity fluid at 407 °C, which is above the critical point of the fluid at that salinity. A vent site in the Cayman Trough named Beebe, which is the worlds deepest known hydrothermal site at ~5000 m below sea level, has shown sustained supercritical venting at 401 °C and 2.3 wt% NaCl
4.
Pacific Ocean
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The Pacific Ocean is the largest and deepest of the Earths oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean in the south and is bounded by Asia and Australia in the west, the Mariana Trench in the western North Pacific is the deepest point in the world, reaching a depth of 10,911 metres. Both the center of the Water Hemisphere and the Western Hemisphere are in the Pacific Ocean, the oceans current name was coined by Portuguese explorer Ferdinand Magellan during the Spanish circumnavigation of the world in 1521, as he encountered favourable winds on reaching the ocean. He called it Mar Pacífico, which in both Portuguese and Spanish means peaceful sea, important human migrations occurred in the Pacific in prehistoric times. Long-distance trade developed all along the coast from Mozambique to Japan, trade, and therefore knowledge, extended to the Indonesian islands but apparently not Australia. By at least 878 when there was a significant Islamic settlement in Canton much of trade was controlled by Arabs or Muslims. In 219 BC Xu Fu sailed out into the Pacific searching for the elixir of immortality, from 1404 to 1433 Zheng He led expeditions into the Indian Ocean. The east side of the ocean was discovered by Spanish explorer Vasco Núñez de Balboa in 1513 after his expedition crossed the Isthmus of Panama and he named it Mar del Sur because the ocean was to the south of the coast of the isthmus where he first observed the Pacific. Later, Portuguese explorer Ferdinand Magellan sailed the Pacific East to West on a Castilian expedition of world circumnavigation starting in 1519, Magellan called the ocean Pacífico because, after sailing through the stormy seas off Cape Horn, the expedition found calm waters. The ocean was often called the Sea of Magellan in his honor until the eighteenth century, sailing around and east of the Moluccas, between 1525 and 1527, Portuguese expeditions discovered the Caroline Islands, the Aru Islands, and Papua New Guinea. In 1542–43 the Portuguese also reached Japan, in 1564, five Spanish ships consisting of 379 explorers crossed the ocean from Mexico led by Miguel López de Legazpi and sailed to the Philippines and Mariana Islands. The Manila galleons operated for two and a half centuries linking Manila and Acapulco, in one of the longest trade routes in history, Spanish expeditions also discovered Tuvalu, the Marquesas, the Cook Islands, the Solomon Islands, and the Admiralty Islands in the South Pacific. In the 16th and 17th century Spain considered the Pacific Ocean a Mare clausum—a sea closed to other naval powers, as the only known entrance from the Atlantic the Strait of Magellan was at times patrolled by fleets sent to prevent entrance of non-Spanish ships. On the western end of the Pacific Ocean the Dutch threatened the Spanish Philippines, Spain also sent expeditions to the Pacific Northwest reaching Vancouver Island in southern Canada, and Alaska. The French explored and settled Polynesia, and the British made three voyages with James Cook to the South Pacific and Australia, Hawaii, and the North American Pacific Northwest, one of the earliest voyages of scientific exploration was organized by Spain in the Malaspina Expedition of 1789–1794. It sailed vast areas of the Pacific, from Cape Horn to Alaska, Guam and the Philippines, New Zealand, Australia, and the South Pacific. Growing imperialism during the 19th century resulted in the occupation of much of Oceania by other European powers, and later, Japan, in Oceania, France got a leading position as imperial power after making Tahiti and New Caledonia protectorates in 1842 and 1853 respectively. After navy visits to Easter Island in 1875 and 1887, Chilean navy officer Policarpo Toro managed to negotiate an incorporation of the island into Chile with native Rapanui in 1888, by occupying Easter Island, Chile joined the imperial nations
5.
Bathyscaphe Trieste
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On 23 January 1960, Jacques Piccard and US Navy Lieutenant Don Walsh achieved the goal of Project Nekton. Trieste was the first manned vessel to have reached the bottom of the Challenger Deep, Trieste consisted of a float chamber filled with gasoline for buoyancy, with a separate pressure sphere to hold the crew. This configuration, allowed for a dive, rather than the previous bathysphere designs in which a sphere was lowered to depth. Trieste was designed by the Swiss scientist Auguste Piccard and originally built in Italy and his pressure sphere, composed of two sections, was built by the company Acciaierie Terni. The upper part was manufactured by the company Cantieri Riuniti dellAdriatico, in the Free Territory of Trieste, the installation of the pressure sphere was done in the Cantiere navale di Castellammare di Stabia, near Naples. Trieste was launched on 26 August 1953 into the Mediterranean Sea near the Isle of Capri, the design was based on previous experience with the bathyscaphe FNRS-2. Trieste was operated by the French Navy, after several years of operation in the Mediterranean Sea, the Trieste was purchased by the United States Navy in 1958 for $250,000. At the time of Project Nekton, Trieste was more than 15 m long, the pressure sphere provided just enough room for two people. Trieste was subsequently fitted with a new sphere, manufactured by the Krupp Steel Works of Essen, Germany. To withstand the pressure of 1.25 metric tons per cm² at the bottom of Challenger Deep. The sphere weighed 14.25 metric tons in air and 8 metric tons in water, outside illumination for the craft was provided by quartz arc-light bulbs, which proved to be able to withstand the over 1,000 standard atmospheres of pressure without any modification. Trieste departed San Diego on 5 October 1959 for Guam aboard the freighter Santa Maria to participate in Project Nekton, on 23 January 1960, she reached the ocean floor in the Challenger Deep, carrying Jacques Piccard and Don Walsh. This was the first time a vessel, manned or unmanned, had reached the deepest known point of the Earths oceans, the descent to the ocean floor took 4 hours 47 minutes at a descent rate of 0.9 metres per second. After passing 9,000 metres, one of the outer Plexiglas window panes cracked, the two men spent barely twenty minutes on the ocean floor. The temperature in the cabin was 7 °C at the time, while at maximum depth, Piccard and Walsh unexpectedly regained the ability to communicate with the support ship, USS Wandank, using a sonar/hydrophone voice communications system. While at the bottom, Piccard and Walsh observed a number of small sole and their claim the fish were swimming would prove at least some vertebrate life can withstand the extreme pressure at the oceans deepest point. They noted that the floor of the Challenger Deep consisted of diatomaceous ooze, the ascent took 3 hours and 15 minutes. Beginning in April 1963, Trieste was modified and used in the Atlantic Ocean to search for the missing submarine USS Thresher, Trieste was delivered to Boston Harbor by USS Point Defiance under the command of Captain H. H. Haisten
6.
Submarine
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A submarine is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability, the term most commonly refers to a large, crewed vessel. It is also used historically or colloquially to refer to remotely operated vehicles and robots, as well as medium-sized or smaller vessels, such as the midget submarine. The noun submarine evolved as a form of submarine boat, by naval tradition, submarines are usually referred to as boats rather than as ships. Although experimental submarines had been built before, submarine design took off during the 19th century, Submarines were first widely used during World War I, and now figure in many navies large and small. Civilian uses for submarines include marine science, salvage, exploration and facility inspection, Submarines can also be modified to perform more specialized functions such as search-and-rescue missions or undersea cable repair. Submarines are also used in tourism, and for undersea archaeology, most large submarines consist of a cylindrical body with hemispherical ends and a vertical structure, usually located amidships, which houses communications and sensing devices as well as periscopes. In modern submarines, this structure is the sail in American usage, a conning tower was a feature of earlier designs, a separate pressure hull above the main body of the boat that allowed the use of shorter periscopes. There is a propeller at the rear, and various hydrodynamic control fins, smaller, deep-diving and specialty submarines may deviate significantly from this traditional layout. Submarines use diving planes and also change the amount of water, Submarines have one of the widest ranges of types and capabilities of any vessel. Submarines can work at greater depths than are survivable or practical for human divers, modern deep-diving submarines derive from the bathyscaphe, which in turn evolved from the diving bell. In 1578, the English mathematician William Bourne recorded in his book Inventions or Devises one of the first plans for an underwater navigation vehicle and its unclear whether he ever carried out his idea. The first submersible of whose construction there exists reliable information was designed and built in 1620 by Cornelis Drebbel and it was propelled by means of oars. By the mid-18th century, over a dozen patents for submarines/submersible boats had been granted in England, in 1747, Nathaniel Symons patented and built the first known working example of the use of a ballast tank for submersion. His design used leather bags that could fill with water to submerge the craft, a mechanism was used to twist the water out of the bags and cause the boat to resurface. In 1749, the Gentlemens Magazine reported that a design had initially been proposed by Giovanni Borelli in 1680. By this point of development, further improvement in design stagnated for over a century, until new industrial technologies for propulsion. The first military submarine was the Turtle, a hand-powered acorn-shaped device designed by the American David Bushnell to accommodate a single person and it was the first verified submarine capable of independent underwater operation and movement, and the first to use screws for propulsion
7.
Deepsea Challenger
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Deepsea Challenger is a 7. 3-metre deep-diving submersible designed to reach the bottom of Challenger Deep, the deepest-known point on Earth. On 26 March 2012, Canadian film director James Cameron piloted the craft to accomplish this goal in the second manned dive reaching the Challenger Deep. Deepsea Challenger was secretly built in Australia, in partnership with the National Geographic Society and with support from Rolex, the construction of the submersible was headed by Australian engineer Ron Allum. Many of the developer team members hail from Sydneys cave-diving fraternity including Allum himself with many years cave-diving experience. The foam is composed of small hollow glass spheres suspended in an epoxy resin. The foam supersedes gasoline-filled tanks for flotation as used in the historic submarine, Allum also built many innovations, necessary to overcome the limitations of existing products. Allum gained much of his developing the electronic communication used in Camerons Titanic dives in filming Ghosts of the Abyss, Bismarck. Power systems for the submarine were supplied by batteries that were housed within the foam. The lithium battery charging systems were designed by Ron Allum, the submersible contains over 180 onboard systems, including batteries, thrusters, life support, 3D cameras, and LED lighting. These interconnected systems are monitored and controlled by a programmable automation controller from Temecula, the crucial structural elements, such as the backbone and pilot sphere that carried Cameron, were engineered by the Tasmanian company Finite Elements. The submersible features a pilot sphere measuring 1.1 metres in diameter, the sphere, with steel walls 64 mm thick, was tested for its ability to withstand the required 114 megapascals of pressure in a pressure chamber at Pennsylvania State University. The sphere sits at the base of the 11. 8-tonne vehicle, the vehicle operates in a vertical attitude, and carries 500 kg of ballast weight that allows it to both sink to the bottom, and when released, rise to the surface. In late January 2012, to test systems, Cameron spent three hours in the submersible while submerged just below the surface in Australias Sydney Naval Yard. On 21 February 2012, a test dive intended to reach a depth of over 1,000 m was aborted after only an hour because of problems with cameras and life support systems. On 28 February 2012, during a dive, Cameron spent six hours in the submersible at a depth of 3,700 m. Power system fluctuations and unforeseen currents presented unexpected challenges, on 4 March 2012, a record-setting dive to more than 7,260 m stopped short of the bottom of the New Britain Trench when problems with the vertical thrusters led Cameron to return to the surface. Days later, with the problem solved, Cameron successfully took the submersible to the bottom of the New Britain Trench. There, he found a plain of loose sediment, anemones, jellyfish
8.
Benthos
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Benthos is the community of organisms that live on, in, or near the seabed, also known as the benthic zone. This community lives in or near marine sedimentary environments, from tidal pools along the foreshore, out to the continental shelf, many organisms adapted to deep-water pressure cannot survive in the upper parts of the water column. The pressure difference can be very significant and this dead and decaying matter sustains the benthic food chain, most organisms in the benthic zone are scavengers or detritivores. The term benthos, coined by Haeckel in 1891, comes from the Greek noun βένθος depth of the sea, Benthos is also used in freshwater biology to refer to organisms at the bottom of freshwater bodies of water, such as lakes, rivers, and streams. There is also a redundant synonym, benthon, the main food sources for the benthos are algae and organic runoff from land. The depth of water, temperature and salinity, and type of local substrate all affect what benthos is present, in coastal waters and other places where light reaches the bottom, benthic photosynthesizing diatoms can proliferate. Filter feeders, such as sponges and bivalves, dominate hard, deposit feeders, such as polychaetes, populate softer bottoms. Fish, such as dragonets, as well as sea stars, snails, cephalopods, and crustaceans are important predators and scavengers. Benthic organisms, such as sea stars, oysters, clams, sea cucumbers, brittle stars and sea anemones, play an important role as a source for fish, such as the California sheephead. They are easily visible to the eye with the lower range of body size at 0.5 mm. In the coastal water ecosystem, they include several species of organisms from different taxa including Porifera, Annelids, Coelenterates, Mollusks, Crustaceans, zoobenthos comprises the animals belonging to the benthos. Phytobenthos comprises the plants belonging to the benthos, mainly benthic diatoms, endobenthos lives buried, or burrowing in the sediment, often in the oxygenated top layer, e. g. a sea pen or a sand dollar. Epibenthos lives on top of the sediments, e. g. like a sea cucumber or a sea snail crawling about, hyperbenthos lives just above the sediment, e. g. a rock cod. Contrast the terms plankton, nekton, and neuston, ryan, Paddy Benthic communities Te Ara - the Encyclopædia of New Zealand, updated 21 September 2007. Yip, Maricela and Madl, Pierre Benthos University of Salzburg
9.
Primary production
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In ecology, primary production is the synthesis of organic compounds from atmospheric or aqueous carbon dioxide. Almost all life on Earth relies directly or indirectly on primary production, the organisms responsible for primary production are known as primary producers or autotrophs, and form the base of the food chain. In terrestrial ecoregions, these are mainly plants, while in aquatic ecoregions algae predominate in this role, ecologists distinguish primary production as either net or gross, the former accounting for losses to processes such as cellular respiration, the latter not. Primary production is the production of energy in organic compounds by living organisms. The main source of energy is sunlight but a minute fraction of primary production is driven by lithotrophic organisms using the chemical energy of inorganic molecules. Regardless of its source, this energy is used to complex organic molecules from simpler inorganic compounds such as carbon dioxide. Consumption of primary producers by heterotrophic organisms, such as animals, then transfers these organic molecules up the food web, gross primary production is the amount of chemical energy as biomass that primary producers create in a given length of time. Some fraction of this energy is used by primary producers for cellular respiration. The remaining fixed energy is referred to as net primary production, some net primary production goes toward growth and reproduction of primary producers, while some is consumed by herbivores. Both gross and net primary production are in units of mass per area per unit time interval. In terrestrial ecosystems, mass of carbon per area per year is most often used as the unit of measurement. On the land, almost all production is now performed by vascular plants, with a small fraction coming from algae and non-vascular plants such as mosses. Before the evolution of plants, non-vascular plants likely played a more significant role. Primary production on land is a function of many factors, but principally local hydrology, while plants cover much of the Earths surface, they are strongly curtailed wherever temperatures are too extreme or where necessary plant resources are limiting, such as deserts or polar regions. Water is consumed in plants by the processes of photosynthesis and transpiration, the latter process is driven by the evaporation of water from the leaves of plants. Transpiration allows plants to transport water and mineral nutrients from the soil to growth regions, diffusion of water vapour out of a leaf, the force that drives transpiration, is regulated by structures known as stomata. These structure also regulate the diffusion of carbon dioxide from the atmosphere into the leaf, certain plants use alternative forms of photosynthesis, called Crassulacean acid metabolism and C4. In a reversal of the pattern on land, in the oceans, almost all photosynthesis is performed by algae, with a small fraction contributed by vascular plants, algae encompass a diverse range of organisms, ranging from single floating cells to attached seaweeds
10.
Giant squid
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The giant squid is a deep-ocean dwelling squid in the family Architeuthidae. The mantle is about 2 m long, and the length of the squid excluding its tentacles rarely exceeds 5 m, claims of specimens measuring 20 m or more have not been scientifically documented. The number of different giant squid species has been debated, in 2004, Japanese researchers took the first images of a live giant squid in its natural habitat, and in July 2012, a live adult was first filmed in its natural habitat off Chichi-jima. Like all squid, a giant squid has a mantle, eight arms, the arms and tentacles account for much of the squids great length, making it much lighter than its chief predator, the sperm whale. Scientifically documented specimens have masses of hundreds, rather than thousands, the inside surfaces of the arms and tentacles are lined with hundreds of subspherical suction cups,2 to 5 cm in diameter, each mounted on a stalk. The circumference of these suckers is lined with sharp, finely serrated rings of chitin, the perforation of these teeth and the suction of the cups serve to attach the squid to its prey. It is common to find circular scars from the suckers on or close to the head of sperm whales that have attacked giant squid, each tentacular club is divided into three regions – the carpus, manus and dactylus. The carpus has a cluster of cups, in six or seven irregular. The manus is broader, closer to the end of the club, the bases of all the arms and tentacles are arranged in a circle surrounding the animals single, parrot-like beak, as in other cephalopods. Giant squid have small fins at the rear of their mantles used for locomotion, like other cephalopods, they are propelled by jet – by pulling water into the mantle cavity, and pushing it through the siphon, in gentle, rhythmic pulses. They can also move quickly by expanding the cavity to fill it with water, Giant squid breathe using two large gills inside the mantle cavity. The circulatory system is closed, which is a characteristic of cephalopods. Like other squid, they contain dark ink used to deter predators, the giant squid has a sophisticated nervous system and complex brain, attracting great interest from scientists. It also has the largest eyes of any living creature except perhaps the colossal squid – up to at least 27 cm in diameter, large eyes can better detect light, which is scarce in deep water. The giant squid probably cannot see colour, but it can discern small differences in tone. Giant squid and some other large squid species maintain neutral buoyancy in seawater through an ammonium chloride solution which is found throughout their bodies and is lighter than seawater and this differs from the method of flotation used by most fish, which involves a gas-filled swim bladder. The solution tastes somewhat like salmiakki and makes giant squid unattractive for general human consumption, like all cephalopods, giant squid use organs called statocysts to sense their orientation and motion in water. The age of a giant squid can be determined by growth rings in the statocysts statolith, much of what is known about giant squid age is based on estimates of the growth rings and from undigested beaks found in the stomachs of sperm whales
11.
Ocean current
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Depth contours, shoreline configurations, and interactions with other currents influence a currents direction and strength. Therefore ocean currents are primarily horizontal water movements, Ocean currents flow for great distances, and together, create the global conveyor belt which plays a dominant role in determining the climate of many of the Earth’s regions. More specifically, ocean currents influence the temperature of the regions through which they travel, for example, warm currents traveling along more temperate coasts increase the temperature of the area by warming the sea breezes that blow over them. Perhaps the most striking example is the Gulf Stream, which makes northwest Europe much more temperate than any region at the same latitude. Another example is Lima, Peru where the climate is cooler than the tropical latitudes in which the area is located, in these wind driven currents, the Ekman spiral effect results in the currents flowing at an angle to the driving winds. In addition, the areas of ocean currents move somewhat with the seasons. Deep ocean basins generally have a surface current, in that the eastern equatorward-flowing branch is broad. These western boundary currents are a consequence of the rotation of the Earth, Deep ocean currents are driven by density and temperature gradients. Thermohaline circulation is known as the oceans conveyor belt. These currents, called submarine rivers, flow under the surface of the ocean and are hidden from immediate detection, where significant vertical movement of ocean currents is observed, this is known as upwelling and downwelling. Deep ocean currents are currently being researched using a fleet of robots called Argo. The South Equatorial Currents of the Atlantic and Pacific straddle the equator, though the Coriolis effect is weak near the equator, water moving in the currents on either side of the equator is deflected slightly poleward and replaced by deeper water. Thus, equatorial upwelling occurs in these westward flowing equatorial surface currents, upwelling is an important process because this water from within and below the pycnocline is often rich in nutrients and greatly benefits the growth of marine organisms. By contrast, generally poor conditions for growth prevail in most of the tropical ocean because strong layering isolates deep. Ocean currents are measured in sverdrup, where 1 sv is equivalent to a flow rate of 1,000,000 m3 per second. Surface currents are found on the surface of an ocean, and are driven by large scale wind currents and they are directly affected by the wind—the Coriolis effect plays a role in their behaviors. Horizontal and vertical currents also exist below the pycnocline in the deeper waters. The movement of water due to differences in density as a function of water temperature, ripple marks in sediments, scour lines, and the erosion of rocky outcrops on deep-ocean floors are evidence that relatively strong, localized bottom currents exist
