154-587: Blue Marine Foundation (stylised as Blue Marine ) is a marine conservation organisation. It was founded as a legacy project following the 2009 documentary film The End of the Line . It has been involved in establishing marine reserves in Lyme Bay , Turneffe Atoll and 4 million square kilometres of protection in the UK Overseas Territories . Chris Gorell Barnes , the executive producer of
308-517: A biodiverse range of larger and smaller animal life. Light is only able to penetrate the top 200 metres (660 ft) so this is the only part of the sea where plants can grow. The surface layers are often deficient in biologically active nitrogen compounds. The marine nitrogen cycle consists of complex microbial transformations which include the fixation of nitrogen , its assimilation, nitrification , anammox and denitrification. Some of these processes take place in deep water so that where there
462-683: A mediterranean sea ) or wholly (as inland seas ) enclosed by land . However, an exception to this is the Sargasso Sea which has no coastline and lies within a circular current, the North Atlantic Gyre . Seas are generally larger than lakes and contain salt water, but the Sea of Galilee is a freshwater lake . The United Nations Convention on the Law of the Sea states that all of the ocean
616-422: A channel in the seabed. It may occur at a gap in a sandbar or near a man-made structure such as a groyne . These strong currents can have a velocity of 3 ft (0.9 m) per second, can form at different places at different stages of the tide and can carry away unwary bathers. Temporary upwelling currents occur when the wind pushes water away from the land and deeper water rises to replace it. This cold water
770-400: A height of less than three feet, so they often pass unnoticed at this stage. In contrast, ocean surface waves caused by winds have wavelengths of a few hundred feet, travel at up to 65 miles per hour (105 km/h) and are up to 45 feet (14 metres) high. As a tsunami moves into shallower water its speed decreases, its wavelength shortens and its amplitude increases enormously, behaving in
924-422: A key player in the survival of entire ecosystems. They provide various marine animals with food, protection, and shelter which keep generations of species alive. Furthermore, coral reefs are an integral part of sustaining human life through serving as a food source (i.e., fish and mollusks) as well as a marine space for ecotourism which provides economic benefits. Also, humans are now conducting research regarding
1078-507: A large and multidisciplinary field: it examines the properties of seawater ; studies waves , tides , and currents ; charts coastlines and maps the seabeds ; and studies marine life . The subfield dealing with the sea's motion, its forces, and the forces acting upon it is known as physical oceanography . Marine biology (biological oceanography) studies the plants , animals , and other organisms inhabiting marine ecosystems . Both are informed by chemical oceanography , which studies
1232-402: A living. However, many fishermen are unable to catch as many fish as they used to, so they are increasingly using cyanide and dynamite in fishing , which further degrades the coral reef ecosystem. This perpetuation of bad habits simply leads to the further decline of coral reefs and therefore perpetuates the problem. One way of stopping this cycle is by educating the local community about why
1386-453: A low-pressure system, can raise the surface of the sea at high tide dramatically. The Earth is composed of a magnetic central core , a mostly liquid mantle and a hard rigid outer shell (or lithosphere ), which is composed of the Earth's rocky crust and the deeper mostly solid outer layer of the mantle. On land the crust is known as the continental crust while under the sea it is known as
1540-521: A major decrease in biological diversity of plants and animals in our environment. These impacts include increased pressure from fisheries including reef degradation and overfishing as well as pressure from the tourism industry which has increased over the past few years. The deterioration of coral reefs is mainly linked to human activities – 88% of reefs are threatened through various reasons as listed above, including excessive amounts of CO 2 ( carbon dioxide ) emissions. Oceans absorb approximately 1/3 of
1694-521: A major threat to turtles in their marine environment. Many sea turtles are accidentally captured, injured or killed by fishing. In response to this threat the National Oceanic and Atmospheric Administration (NOAA) worked with the shrimp trawling industry to create the TEDs. By working with the industry they insured the commercial viability of the devices. A TED is a series of bars that is placed at
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#17327987377101848-534: A new world of creatures living on the seabed that scientists had not previously known to exist. Some like the detrivores rely on organic material falling to the ocean floor. Others cluster round deep sea hydrothermal vents where mineral-rich flows of water emerge from the seabed, supporting communities whose primary producers are sulphide-oxidising chemoautotrophic bacteria, and whose consumers include specialised bivalves, sea anemones, barnacles, crabs, worms and fish, often found nowhere else. A dead whale sinking to
2002-407: A predetermined date every year, Ocean Conservancy promotes The International Coastal Cleanup to rally communities to volunteer to collect trash from the coastlines across the globe. The campaign has expanded originally from its two founders and has now reached over 100 countries. Oceana is an example of an advocacy/lobbying group that encourages donations as a means to enact legislation and protect
2156-536: A saline body of water and therefore solely a sea in the sense of the common use of the word, like all other saltwater lakes called sea. Earth is the only known planet with seas of liquid water on its surface, although Mars possesses ice caps and similar planets in other solar systems may have oceans. Earth's 1,335,000,000 cubic kilometers (320,000,000 cu mi) of sea contain about 97.2 percent of its known water and covers approximately 71 percent of its surface. Another 2.15% of Earth's water
2310-611: A specific level of protection and a specific allowed range of activities. There are marine conservation non-governmental organizations throughout the world that focus on funding conservation efforts, educating the public and stakeholders, and lobbying for conservation law and policy. Examples of these include: On a regional level, PERSGA, the Regional Organization for the Conservation of the Environment of
2464-552: A steward of the natural resources of the earth has been a discouraging one, there has long been a certain comfort in the belief that the sea, at least was inviolate, beyond man’s ability to change and to despoil. But this belief, unfortunately, has proved to be naïve”. Rachel Carson , The Sea Around Us ,(1951) If the oceans die, we all die. – Paul Watson Increasing human populations have resulted in increased human impact on ecosystems. Human activities has resulted in an increased extinction rate of species which has caused
2618-401: A sub-discipline of conservation biology . Public interest in marine biology increased in the post-war years with the publication of Rachel Carson `s sea trilogy (1941-1955); which helped inspire an era known as the "marine revolution". The United States federal legislation showed its support for marine conservation by institutionalizing protected areas and creating marine estuaries. In 1969,
2772-471: A very high range in bays or estuaries . Submarine earthquakes arising from tectonic plate movements under the oceans can lead to destructive tsunamis , as can volcanoes, huge landslides , or the impact of large meteorites . The seas have been an integral element for humans throughout history and culture. Humans harnessing and studying the seas have been recorded since ancient times and evidenced well into prehistory , while its modern scientific study
2926-414: A wide array of species including corals (only six of which contribute to reef formation). Marine primary producers – plants and microscopic organisms in the plankton – are widespread and very essential for the ecosystem. It has been estimated that half of the world's oxygen is produced by phytoplankton. About 45 percent of the sea's primary production of living material
3080-529: Is "sea". The law of the sea has at its center the definition of the boundaries of the ocean, clarifying its application in marginal seas . But what bodies of water other than the sea the law applies to is being crucially negotiated in the case of the Caspian Sea and its status as "sea", basically revolving around the issue of the Caspian Sea about either being factually an oceanic sea or only
3234-449: Is a continuous circulation of water in the oceans. Warm surface currents cool as they move away from the tropics, and the water becomes denser and sinks. The cold water moves back towards the equator as a deep sea current, driven by changes in the temperature and density of the water, before eventually welling up again towards the surface. Deep seawater has a temperature between −2 °C (28 °F) and 5 °C (41 °F) in all parts of
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#17327987377103388-539: Is a large body of salt water . There are particular seas and the sea . The sea commonly refers to the Ocean , the interconnected body of seawaters that spans most of Earth. Particular seas are either marginal seas , second-order sections of the oceanic sea (e.g. the Mediterranean Sea ), or certain large, nearly landlocked bodies of water. The salinity of water bodies varies widely, being lower near
3542-399: Is a point of land jutting out into the sea and a larger promontory is known as a cape . The indentation of a coastline, especially between two headlands, is a bay , a small bay with a narrow inlet is a cove and a large bay may be referred to as a gulf . Coastlines are influenced by several factors including the strength of the waves arriving on the shore, the gradient of the land margin,
3696-487: Is an upwelling of cold waters, and also near estuaries where land-sourced nutrients are present, plant growth is higher. This means that the most productive areas, rich in plankton and therefore also in fish, are mainly coastal. There is a broader spectrum of higher animal taxa in the sea than on land, many marine species have yet to be discovered and the number known to science is expanding annually. Some vertebrates such as seabirds , seals and sea turtles return to
3850-556: Is called oceanography and maritime space is governed by the law of the sea , with admiralty law regulating human interactions at sea. The seas provide substantial supplies of food for humans, mainly fish , but also shellfish , mammals and seaweed , whether caught by fishermen or farmed underwater. Other human uses of the seas include trade , travel, mineral extraction , power generation , warfare , and leisure activities such as swimming , sailing , and scuba diving . Many of these activities create marine pollution . The sea
4004-478: Is contributed by diatoms . Much larger algae, commonly known as seaweeds , are important locally; Sargassum forms floating drifts, while kelp form seabed forests. Flowering plants in the form of seagrasses grow in " meadows " in sandy shallows, mangroves line the coast in tropical and subtropical regions and salt-tolerant plants thrive in regularly inundated salt marshes . All of these habitats are able to sequester large quantities of carbon and support
4158-590: Is directly addressed by it, which makes it the only international intergovernmental instrument to do so. Through the Intergovernmental Oceanographic Commission , the United Nations Educational, Scientific and Cultural Organization ( UNESCO ) organizes programs in marine research, observation systems, hazard mitigation, and better managing ocean and coastal ecosystems. The Organization is the originator of
4312-679: Is equipped with a means to transmit the collected data via satellite. Though the data are physically stored on the tag, its major advantage is that it does not have to be physically retrieved like an archival tag for the data to be available, making it a viable independent tool for animal behavior studies. These tags have been used to track movements of ocean sunfish , marlin , blue sharks , bluefin tuna , swordfish and sea turtles . Location, depth, temperature, and body movement data are used to answer questions about migratory patterns, seasonal feeding movements, daily habits, and survival after catch and release. Turtle excluder devices (TEDs) remove
4466-481: Is frozen, found in the sea ice covering the Arctic Ocean , the ice cap covering Antarctica and its adjacent seas , and various glaciers and surface deposits around the world. The remainder (about 0.65% of the whole) form underground reservoirs or various stages of the water cycle , containing the freshwater encountered and used by most terrestrial life : vapor in the air , the clouds it slowly forms,
4620-776: Is included in the United Nations framework of Sustainable Development Goals (SDGs), most notably in SDG 14 ("Life below water"). The text of Target 14.5 is: "By 2020, conserve at least 10 per cent of coastal and marine areas, consistent with national and international law and based on the best available scientific information". This target has one indicator: Indicator 14.5.1 is the "coverage of protected areas in relation to marine areas". The term " Marine Protected Areas " include marine reserves, fully protected marine areas, no-take zones, marine sanctuaries, ocean sanctuaries, marine parks, locally managed marine areas and other. Each area has
4774-482: Is indicated through data collected by the MTSG that analyzes abundance and historical information on the species. This data examined the global population of green turtles at 32 nesting sites, and determined that over the last 100–150 years there has been a 48–65 percent decrease in the number of mature nesting females. The Kemp's ridley sea turtle population fell in 1947 when 33,000 nests, which accounted for 80 percent of
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4928-505: Is key, as is education of the public about conservation issues. This includes educating tourists that come to an area who might not be familiar with certain regulations regarding the marine habitat. One example of this is a project called Green Fins based in Southeast Asia that uses the scuba diving industry to educate the public. This project, implemented by UNEP , encourages scuba diving operators to educate their students about
5082-401: Is likely to reduce levels of oxygen in surface waters since the solubility of oxygen in water falls at higher temperatures. Ocean deoxygenation is projected to increase hypoxia by 10%, and triple suboxic waters (oxygen concentrations 98% less than the mean surface concentrations), for each 1 °C of upper-ocean warming. The amount of light that penetrates the sea depends on the angle of
5236-530: Is near the Mariana Islands , a volcanic archipelago in the West Pacific. Its deepest point is 10.994 kilometres (nearly 7 miles) below the surface of the sea. The zone where land meets sea is known as the coast and the part between the lowest spring tides and the upper limit reached by splashing waves is the shore . A beach is the accumulation of sand or shingle on the shore. A headland
5390-402: Is necessary to cater to the needs of fishermen while also protecting marine life. Pop-up satellite archival tag (PSAT or PAT) plays a vital role in marine conservation by providing marine biologists with an opportunity to study animals in their natural environments. These are used to track movements of (usually large, migratory) marine animals. A PSAT is an archival tag (or data logger ) that
5544-613: Is now extinct due to European and Native American whaling. Since the 1960s the global population of monk seals has been rapidly declining. The Hawaiian and Mediterranean monk seals are considered to be one of the most endangered marine mammals on the planet, according to the NOAA . The last sighting of the Caribbean monk seal was in 1952, and it has now been confirmed extinct by the NOAA. The vaquita porpoise, discovered in 1958, has become
5698-541: Is often rich in nutrients and creates blooms of phytoplankton and a great increase in the productivity of the sea. Tides are the regular rise and fall in water level experienced by seas and oceans in response to the gravitational influences of the Moon and the Sun, and the effects of the Earth's rotation. During each tidal cycle, at any given place the water rises to a maximum height known as "high tide" before ebbing away again to
5852-656: Is one of the places in the world that is the most impacted by foreign and invasive species. According to the Baykeeper organization, 97 percent of the organisms in the San Francisco Bay have been compromised by the 240 invasive species that have been brought into the ecosystem. Invasive species in the bay such as the Asian clam have changed the food web of the ecosystem by depleting populations of native species such as plankton. The Asian clam clogs pipes and obstructs
6006-595: Is the interconnected system of all the Earth's oceanic waters, including the Atlantic , Pacific , Indian , Southern and Arctic Oceans . However, the word "sea" can also be used for many specific, much smaller bodies of seawater, such as the North Sea or the Red Sea . There is no sharp distinction between seas and oceans , though generally seas are smaller, and are often partly (as marginal seas or particularly as
6160-609: Is the protection and preservation of ecosystems in oceans and seas through planned management in order to prevent the over-exploitation of these marine resources . Marine conservation is informed by the study of marine plants and animal resources and ecosystem functions and is driven by response to the manifested negative effects seen in the environment such as species loss , habitat degradation and changes in ecosystem functions and focuses on limiting human-caused damage to marine ecosystems , restoring damaged marine ecosystems, and preserving vulnerable species and ecosystems of
6314-469: Is the widely acknowledged system in charge of resolving all matters regarding the law of the sea. The Convention regulates all facets of ocean space, including delimitation, environmental control, marine scientific research, economic and commercial activity, transfer of technology, and the resolution of disputes pertaining to ocean issues. It has 320 articles and nine annexes. The UN Environment Programme (UNEP) works to safeguard oceans and seas and encourage
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6468-419: Is turned into kinetic energy, creating a shallow wave, a tsunami, radiating outwards at a velocity proportional to the square root of the depth of the water and which therefore travels much faster in the open ocean than on a continental shelf. In the deep open sea, tsunamis have wavelengths of around 80 to 300 miles (130 to 480 km), travel at speeds of over 600 miles per hour (970 km/h) and usually have
6622-1052: The Convention on the protection of the Underwater Cultural Heritage , the Global Ocean Observing System and UNESCO global geoparks . Around 1 800 quantifiable and monetary pledges totaling $ 108 billion have been obtained since 2017 for the UN Ocean Conference and the Our Ocean Conference. At the 1998 Oslo and Paris Convention for the Protection of the Marine Environment of the North-East Atlantic, environmental ministers from 15 Northeast Atlantic states and members of
6776-651: The Coriolis effect . The surface currents flow in a clockwise direction in the Northern Hemisphere and anticlockwise in the Southern Hemisphere. The water moving away from the equator is warm, and that flowing in the reverse direction has lost most of its heat. These currents tend to moderate the Earth's climate, cooling the equatorial region and warming regions at higher latitudes. Global climate and weather forecasts are powerfully affected by
6930-618: The Endangered Species Act , and in 1998, it was granted protection as an endangered species. It is now known to be a clone of the widespread Halophila ovalis and protection was withdrawn. Data on this plant is limited, but it is known that since the 1970s there has been a 50 percent decrease in abundance. There are many reasons behind the decline in the seagrass's proliferation, such as degradation of water quality, careless boating activities, anchoring. In addition to that hurricane activity caused by climate change , increase
7084-857: The Mediterranean and Red Sea with the Egyptian Hannu reaching the Arabian Peninsula and the African Coast around 2750 BC. In the first millennium BC, Phoenicians and Greeks established colonies throughout the Mediterranean and the Black Sea . Around 500 BC, the Carthaginian navigator Hanno left a detailed periplus of an Atlantic journey that reached at least Senegal and possibly Mount Cameroon . In
7238-616: The National Marine Sanctuaries program. In 2010, the Scottish Parliament enacted new legislation for the protection of marine life with the Marine (Scotland) Act 2010 . Its provisions include marine planning, marine licensing, marine conservation, seal conservation, and enforcement. Since 2006, United Nations introduce vulnerable marine ecosystem concept for the management of deep-sea fisheries in
7392-458: The North pacific seastar which was introduced to Tasmania, Australia. Vectors for the translocation of organisms include hull biofouling , the dumping of ballast water and dumping of water from marine aquaria. A tank of ballast water is estimated to contain around 3,000 non-native species. Once established, it is difficult to eradicate an exotic organism from an ecosystem. The San Francisco Bay
7546-694: The Pacific bluefin tuna from "least concerned" to "vulnerable" on a scale that represents level of extinction risk. The Pacific bluefin tuna is targeted by the fishing industry mainly for its use in sushi. A stock assessment released in 2013 by the International Scientific Committee for Tuna and Tuna-Like Species in the North Pacific Ocean (ISC) shows that the Pacific bluefin tuna population dropped by 96 percent in
7700-584: The early Mediaeval period , the Vikings crossed the North Atlantic and even reached the northeastern fringes of North America. Novgorodians had also been sailing the White Sea since the 13th century or before. Meanwhile, the seas along the eastern and southern Asian coast were used by Arab and Chinese traders. The Chinese Ming Dynasty had a fleet of 317 ships with 37,000 men under Zheng He in
7854-614: The hundred-year wave ) they are designed against. Rogue waves, however, have been documented at heights above 25 meters (82 ft). The top of a wave is known as the crest, the lowest point between waves is the trough and the distance between the crests is the wavelength. The wave is pushed across the surface of the sea by the wind, but this represents a transfer of energy and not a horizontal movement of water. As waves approach land and move into shallow water , they change their behavior. If approaching at an angle, waves may bend ( refraction ) or wrap rocks and headlands ( diffraction ). When
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#17327987377108008-562: The marine life . Marine conservation is a relatively new discipline which has developed as a response to biological issues such as extinction and marine habitats change. Marine conservationists rely on a combination of scientific principles derived from marine biology , Ecology , oceanography , and fisheries science , as well as on human factors, such as demand for marine resources, maritime law , economics, and policy, in order to determine how to best protect and conserve marine species and ecosystems. Marine conservation may be described as
8162-422: The oceanic crust . The latter is composed of relatively dense basalt and is some five to ten kilometres (three to six miles) thick. The relatively thin lithosphere floats on the weaker and hotter mantle below and is fractured into a number of tectonic plates . In mid-ocean, magma is constantly being thrust through the seabed between adjoining plates to form mid-oceanic ridges and here convection currents within
8316-436: The photosynthetic activity of these plants produces oxygen, which dissolves in the seawater and is used by marine animals. At night, photosynthesis stops, and the amount of dissolved oxygen declines. In the deep sea, where insufficient light penetrates for plants to grow, there is very little dissolved oxygen. In its absence, organic material is broken down by anaerobic bacteria producing hydrogen sulphide . Climate change
8470-421: The rain falling from them, and the lakes and rivers spontaneously formed as its waters flow again and again to the sea. The scientific study of water and Earth's water cycle is hydrology ; hydrodynamics studies the physics of water in motion. The more recent study of the sea in particular is oceanography . This began as the study of the shape of the ocean's currents but has since expanded into
8624-412: The swash moves beach material seawards. Under their influence, the sand and shingle on the beach is ground together and abraded. Around high tide, the power of a storm wave impacting on the foot of a cliff has a shattering effect as air in cracks and crevices is compressed and then expands rapidly with release of pressure. At the same time, sand and pebbles have an erosive effect as they are thrown against
8778-420: The water , carbon , and nitrogen cycles . The surface of water interacts with the atmosphere, exchanging properties such as particles and temperature, as well as currents . Surface currents are the water currents that are produced by the atmosphere's currents and its winds blowing over the surface of the water, producing wind waves , setting up through drag slow but stable circulations of water, as in
8932-569: The Austronesian " Lapita " peoples displayed great feats of navigation, reaching out from the Bismarck Archipelago to as far away as Fiji , Tonga , and Samoa . Their descendants continued to travel thousands of miles between tiny islands on outrigger canoes , and in the process they found many new islands, including Hawaii , Easter Island (Rapa Nui), and New Zealand. The Ancient Egyptians and Phoenicians explored
9086-468: The CO 2 produced by humans, which has detrimental effects on the marine environment. The increasing levels of CO 2 in oceans change the seawater chemistry by decreasing the pH , which is known as ocean acidification . Oil spills also impact marine environments, contributing to marine pollution as a result of human activity. The effects of oil on marine fish have been studied following major spills in
9240-672: The Coastal Maine National Wildlife Refuge was renamed the Rachel Carson National Wildlife Refuge , highlighting Carson's contribution. The refuge protects various kinds of habitat, including barrier beach , dune , tidal estuary , salt marsh, and rocky coastline. However, it wasn't until the 1970s when the modern science of marine conservation would become first recognised; with undersea explorations equipped with new technologies, such as computers, being undertaken at
9394-405: The Earth , clarified the process of sedimentation , and assisted the study of volcanism and earthquakes . A characteristic of seawater is that it is salty. Salinity is usually measured in parts per thousand ( ‰ or per mil), and the open ocean has about 35 grams (1.2 oz) solids per litre, a salinity of 35 ‰. The Mediterranean Sea is slightly higher at 38 ‰, while the salinity of
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#17327987377109548-420: The Earth is closest to the Moon because it is also where the effect of the Moon's gravity is stronger. On the opposite side of the Earth, the lunar force is at its weakest and this causes another bulge to form. As the Moon rotates around the Earth, so do these ocean bulges move around the Earth. The gravitational attraction of the Sun is also working on the seas, but its effect on tides is less powerful than that of
9702-411: The Earth to make a complete revolution and return the Moon to its previous position relative to an observer. The Moon's mass is some 27 million times smaller than the Sun, but it is 400 times closer to the Earth. Tidal force or tide-raising force decreases rapidly with distance, so the moon has more than twice as great an effect on tides as the Sun. A bulge is formed in the ocean at the place where
9856-691: The European Commission agreed to identify marine species, habitats, and ecosystems that need protection and to "promote the establishment of a network of marine protected areas to ensure the sustainable use, protection, and conservation of marine biological diversity.” In June 2023, the High Seas Treaty was adopted by the UN to better protect marine environment and ecosystems in international waters. It needs ratification by at least 60 member states to enter into force. Marine conservation
10010-737: The Lyme Bay Working Group is designed to ensure fishing communities can continue to fish while the fragile ecosystem is protected and conserved. The charity also played a central role in the creation of a marine reserve around the Turneffe Atoll , which is part of the Belize Barrier Reef . This project was completed in partnership with local fishermen and organizations and the Government of Belize . The Bertarelli Foundation also provided funding. Blue Marine
10164-413: The Moon, and when the Sun, Moon and Earth are all aligned (full moon and new moon), the combined effect results in the high "spring tides". In contrast, when the Sun is at 90° from the Moon as viewed from Earth, the combined gravitational effect on tides is less causing the lower "neap tides". A storm surge can occur when high winds pile water up against the coast in a shallow area and this, coupled with
10318-756: The Pacific Ocean. According to the ISC assessment, 90 percent of the Pacific bluefin tuna caught are juveniles that have not reproduced. Between 2011 and 2014, the European eel , Japanese eel , and American eel were put on the IUCN red list of endangered species. In 2015, the Environmental Agency concluded that the number of European eels has declined by 95 percent since 1990. An Environmental Agency officer, Andy Don, who has been researching eels for
10472-581: The Red Sea and the Gulf of Aden, is a regional entity which serves as the secretariat for the Jeddah Convention-1982, one of the first regional marine agreements. PERSGA member states are Djibouti, Egypt, Jordan, Saudi Arabia, Somalia, Sudan and Yemen. There have been a number of organized efforts from marine conservation groups such as those aforementioned in this article to raise awareness of
10626-556: The Southern Hemisphere in the Roaring Forties , long, organised masses of water called swell roll across the ocean. If the wind dies down, the wave formation is reduced, but already-formed waves continue to travel in their original direction until they meet land. The size of the waves depends on the fetch , the distance that the wind has blown over the water and the strength and duration of that wind. When waves meet others coming from different directions, interference between
10780-673: The Sylvia Earle Alliance, Deep Search Foundation, and Deep Search). Mission Blue aims to establish marine protected areas (dubbed "Hope Spots") around the globe with the support of more than two hundred organisations. These supporters range from large, global companies to small, bespoke research teams. That same year Earle also published 'The World is Blue: How Our Fate and the Ocean's Are One', widely acclaimed as being 'a Silent Spring for our era'; in which Earle reveals how just 50 years of swift and dangerous oceanic change threatens
10934-593: The UK government around the Chagos Archipelago in the Indian Ocean. At the time of its creation in 2010, it was the world's largest marine reserve. The Bertarelli Foundation funded the first five years, after which the government promised to internalise the costs and enforce the reserve. Henry Bellingham , a UK junior Foreign Office minister, described the initiative as a "great example" of government and
11088-487: The United States. Shipping is a major vector for the introduction of exotic marine species, some of which can become overabundant and transform ecosystems. Collisions with ships can also be fatal for whales and can impact on the viability of whole populations, including the right whale population off the east coast of the United States. Coral reefs are the epicenter of immense amounts of biodiversity and are
11242-517: The added CO 2 is absorbed by the oceans, forming carbonic acid and lowering the pH (now below 8.1 ) through a process called ocean acidification . The extent of further ocean chemistry changes, including ocean pH, will depend on climate change mitigation efforts taken by nations and their governments. The amount of oxygen found in seawater depends primarily on the plants growing in it. These are mainly algae, including phytoplankton , with some vascular plants such as seagrasses . In daylight,
11396-455: The air or by water, gliding over and under the ocean’s surface. She conveyed the sense that she was the living ocean…” In 2010, over 100 scientists, business leaders, philanthropists, and entertainment icons came together to support Dr. Sylvia Earle ’s Mission Blue wish and the following year, Gigi Brisson founded a group of Ocean Elders with the goal of unifying scientists with government and entertainment leaders. “Although man’s record as
11550-581: The areas beyond national jurisdiction. This concept has been transposed by the European parliament for Atlantic European waters. The United Nations Convention on the Law of the Sea establishes guidelines for all uses of the oceans' resources and establishes a comprehensive regime of law and order in the world's oceans and seas. On December 10, 1982, the convention was made available for signature at Montego Bay, Jamaica . More than 150 nations representing all world regions, all legal and political systems, and
11704-411: The behavior of elements and molecules within the oceans: particularly, at the moment, the ocean's role in the carbon cycle and carbon dioxide 's role in the increasing acidification of seawater. Marine and maritime geography charts the shape and shaping of the sea, while marine geology (geological oceanography) has provided evidence of continental drift and the composition and structure of
11858-529: The bottom of the ocean provides food for an assembly of organisms which similarly rely largely on the actions of sulphur-reducing bacteria. Such places support unique biomes where many new microbes and other lifeforms have been discovered. Humans have travelled the seas since they first built sea-going craft. Mesopotamians were using bitumen to caulk their reed boats and, a little later, masted sails . By c. 3000 BC, Austronesians on Taiwan had begun spreading into maritime Southeast Asia . Subsequently,
12012-467: The boundaries between the land and sea, the slightly denser oceanic plates slide beneath the continental plates and more subduction trenches are formed. As they grate together, the continental plates are deformed and buckle causing mountain building and seismic activity. The Earth's deepest trench is the Mariana Trench which extends for about 2,500 kilometres (1,600 miles) across the seabed. It
12166-516: The case of the ocean sustaining deep-sea ocean currents . Deep-sea currents, known together as the global conveyor belt , carry cold water from near the poles to every ocean and significantly influence Earth's climate. Tides , the generally twice-daily rise and fall of sea levels , are caused by Earth's rotation and the gravitational effects of the Moon and, to a lesser extent, of the Sun . Tides may have
12320-437: The coast scour out channels and transport sand and pebbles away from their place of origin. Sediment carried to the sea by rivers settles on the seabed causing deltas to form in estuaries. All these materials move back and forth under the influence of waves, tides and currents. Dredging removes material and deepens channels but may have unexpected effects elsewhere on the coastline. Governments make efforts to prevent flooding of
12474-446: The composition and hardness of the coastal rock, the inclination of the off-shore slope and the changes of the level of the land due to local uplift or submergence. Normally, waves roll towards the shore at the rate of six to eight per minute and these are known as constructive waves as they tend to move material up the beach and have little erosive effect. Storm waves arrive on shore in rapid succession and are known as destructive waves as
12628-507: The conservation of marine spaces that include coral reefs is important. Overfishing is one of main causes of the decrease in the ocean's wildlife population over the past years. The Food and Agriculture Organization of the United Nation reported that the percentage of the world's fish stocks that are at biologically sustainable levels have decreased from 90% in 1974 to 65.8% in 2017. The overfishing of these large fisheries destroys
12782-598: The continental shelf. Alternatively, marine habitats can be divided vertically into pelagic (open water), demersal (just above the seabed) and benthic (sea bottom) habitats. A third division is by latitude : from polar seas with ice shelves, sea ice and icebergs, to temperate and tropical waters. Coral reefs, the so-called "rainforests of the sea", occupy less than 0.1 percent of the world's ocean surface, yet their ecosystems include 25 percent of all marine species. The best-known are tropical coral reefs such as Australia's Great Barrier Reef , but cold water reefs harbour
12936-522: The currents. Most of the smallest organisms are the larvae of fish and marine invertebrates which liberate eggs in vast numbers because the chance of any one embryo surviving to maturity is so minute. The zooplankton feed on phytoplankton and on each other and form a basic part of the complex food chain that extends through variously sized fish and other nektonic organisms to large squid , sharks , porpoises , dolphins and whales . Some marine creatures make large migrations, either to other regions of
13090-410: The destruction may be caused by the flood water draining back into the sea after the tsunami has struck, dragging debris and people with it. Often several tsunami are caused by a single geological event and arrive at intervals of between eight minutes and two hours. The first wave to arrive on shore may not be the biggest or most destructive. Wind blowing over the surface of the sea causes friction at
13244-413: The direction of the wind. The friction between air and water caused by a gentle breeze on a pond causes ripples to form. A strong blow over the ocean causes larger waves as the moving air pushes against the raised ridges of water. The waves reach their maximum height when the rate at which they are travelling nearly matches the speed of the wind. In open water, when the wind blows continuously as happens in
13398-485: The documentary film The End of the Line , co-founded the Blue Marine Foundation with Charles Clover (the author of the book The End of the Line ) and filmmaker George Duffield , as a legacy project of the film. It was formed with the aim of fixing environmental issues impacting the oceans. Blue Marine Foundation secured funding to enforce the protection of the no-take marine reserve created by
13552-571: The early fifteenth century, sailing the Indian and Pacific Oceans. In the late fifteenth century, Western European mariners started making longer voyages of exploration in search of trade. Bartolomeu Dias rounded the Cape of Good Hope in 1487 and Vasco da Gama reached India via the Cape in 1498. Christopher Columbus sailed from Cadiz in 1492, attempting to reach the eastern lands of India and Japan by
13706-500: The effectiveness of marine conservation through change caused by social events and encourage sustainable tourism development to raise the public awareness of it. Researchers suggest integrating customary management into marine conservation and emphasize that practical and conceptual differences exist between customary management and contemporary conservation which have often led to failed attempts to hybridize these systems. Others have suggested to integrate marine conservation and tourism,
13860-474: The end of the decade. During these explorations, fundamental principles of change were discovered in relation to marine ecosystems. Through this discovery, the interdependent nature of the ocean was revealed. This led to a change in the approach of marine conservation efforts, and a new emphasis was put on restoring systems within the environment, along with protecting biodiversity. In 1972 Marine Protection, Research, and Sanctuaries Act (MPRSA) passed, beginning
14014-611: The establishment of conservation areas can help reduce conflicts. Zoning the protected areas enables the grouping of compatible areas into specific zones and the separation of incompatible areas. Common techniques to raise the general public's attention also include exposure to the concept of the carbon footprint and to educate people to make sustainable food choices and use fewer plastic products. Marine conservation technologies are used to protect endangered and threatened marine organisms and/or habitat. These technologies are innovative and revolutionary because they reduce by-catch, increase
14168-486: The flow of water in electrical generating facilities. Their presence in the San Francisco Bay has cost the United States an estimated one billion dollars in damages. Baleen whales were predominantly hunted from 1600 through the mid-1900s, and were nearing extinction when a global ban on commercial whaling was put into effect in 1986 by the IWC (International Whaling Convention). The Atlantic gray whale, last sighted in 1740,
14322-422: The food chain or precipitated into the deeper, more carbon-rich layers as dead soft tissue or in shells and bones as calcium carbonate . It circulates in this layer for long periods of time before either being deposited as sediment or being returned to surface waters through thermohaline circulation. The oceans are home to a diverse collection of life forms that use it as a habitat. Since sunlight illuminates only
14476-467: The full range of socio-economic development participated. The Convention introduced new legal concepts, addressed new issues, and combined the conventional norms for the usage of the oceans into one document. The convention also established the framework for furthering the study of particular facets of maritime law. On November 16, 1994, the Convention came into effect in line with article 308. Today, it
14630-464: The gap and a circular movement of surface currents known as a gyre is formed. There are five main gyres in the world's oceans: two in the Pacific, two in the Atlantic and one in the Indian Ocean. Other smaller gyres are found in lesser seas and a single gyre flows around Antarctica . These gyres have followed the same routes for millennia, guided by the topography of the land, the wind direction and
14784-570: The globe. Seawater with a typical salinity of 35 ‰ has a freezing point of about −1.8 °C (28.8 °F). When its temperature becomes low enough, ice crystals form on the surface. These break into small pieces and coalesce into flat discs that form a thick suspension known as frazil . In calm conditions, this freezes into a thin flat sheet known as nilas , which thickens as new ice forms on its underside. In more turbulent seas, frazil crystals join into flat discs known as pancakes. These slide under each other and coalesce to form floes . In
14938-500: The human impact on the situation and inspire people to take action. Some groups take on more public facing campaigns that directly attempt to get civilians engaged with the issue compared to other groups who encourage donations from civilians which goes towards lobbying and advocacy towards the government. Ocean Conservancy and its International Coastal Cleanup is an example of a public-facing campaign that aims to increase participation in conservation efforts among every day civilians. On
15092-761: The importance of marine conservation and encourage them to dive in an environmentally friendly manner that does not damage coral reefs or associated marine ecosystems. Scientists divide the process by a few parts, and there are various techniques in each part of it. In marking and capturing, the normal techniques include techniques for restraint in pinnipeds, chemical restraint and immobilization in pinnipeds, techniques for capture-release of cetaceans and techniques for restraint and handling. Recently, some novel approaches include remote sensing techniques to model exposure of coastal-marine ecosystems to riverine flood plumes and advanced iconography. Techniques also include many social science-based methods. Many researchers have found
15246-442: The interface between air and sea. Not only does this cause waves to form, but it also makes the surface seawater move in the same direction as the wind. Although winds are variable, in any one place they predominantly blow from a single direction and thus a surface current can be formed. Westerly winds are most frequent in the mid-latitudes while easterlies dominate the tropics. When water moves in this way, other water flows in to fill
15400-484: The land by the building of breakwaters , seawalls , dykes and levees and other sea defences. For instance, the Thames Barrier is designed to protect London from a storm surge, while the failure of the dykes and levees around New Orleans during Hurricane Katrina created a humanitarian crisis in the United States. The sea plays a part in the water or hydrological cycle , in which water evaporates from
15554-523: The land to breed but fish, cetaceans and sea snakes have a completely aquatic lifestyle and many invertebrate phyla are entirely marine. In fact, the oceans teem with life and provide many varying microhabitats. One of these is the surface film which, even though tossed about by the movement of waves, provides a rich environment and is home to bacteria, fungi , microalgae , protozoa , fish eggs and various larvae. The pelagic zone contains macro- and microfauna and myriad zooplankton which drift with
15708-525: The laws of the ocean. Specifically, Oceana is currently lobbying to prevent the expansion of offshore drilling with emphasis in areas such as the Arctic and Belize. Oceana is currently mentioned in a wide range of bills in the US Congress regarding issues such as anti-drilling protections on the Atlantic coast and the penalty for buying, selling, possessing, or transporting shark fins. Sea A sea
15862-648: The levels of salinity in different seas, the relative composition of the dissolved salts is stable throughout the world's oceans. Seawater is too saline for humans to drink safely, as the kidneys cannot excrete urine as salty as seawater. Although the amount of salt in the ocean remains relatively constant within the scale of millions of years, various factors affect the salinity of a body of water. Evaporation and by-product of ice formation (known as "brine rejection") increase salinity, whereas precipitation , sea ice melt, and runoff from land reduce it. The Baltic Sea , for example, has many rivers flowing into it, and thus
16016-508: The mantle tend to drive the two plates apart. Parallel to these ridges and nearer the coasts, one oceanic plate may slide beneath another oceanic plate in a process known as subduction . Deep trenches are formed here and the process is accompanied by friction as the plates grind together. The movement proceeds in jerks which cause earthquakes, heat is produced and magma is forced up creating underwater mountains, some of which may form chains of volcanic islands near to deep trenches. Near some of
16170-532: The marine conservation movement. The act allowed the regulation by the United States Environmental Protection Agency (EPA) over dumping in the seas. Though the act was later amended, it was one of several key events to bring marine issues towards the front of environmental issues in the United States. In 2009, Sylvia Earle received the million dollar TED prize which led to the foundation of Mission Blue (also known as
16324-530: The marine environment and threatens the livelihood of billions who depend on fish as protein or as a source of income for catching and selling. According to the World Wildlife Fund , illegal, unreported, and unregulated fishing is a major factor in overfishing. Illegal fishing is estimated to account for up to 30% of the catch for some high value species, and the industry is estimated to be worth $ 36 billion per year. Overabundance can occur when
16478-416: The minimum "low tide" level. As the water recedes, it uncovers more and more of the foreshore , also known as the intertidal zone. The difference in height between the high tide and low tide is known as the tidal range or tidal amplitude. Most places experience two high tides each day, occurring at intervals of about 12 hours and 25 minutes. This is half the 24 hours and 50 minute period that it takes for
16632-631: The most endangered marine species. Over half the population has disappeared since 2012, leaving 100 left in 2014. The vaquita frequently drowns in fishing nets, which are used illegally in marine protected areas off the Gulf of Mexico. In 2004, the Marine Turtle Specialist Group (MTSG), from the International Union for Conservation of Nature (IUCN), ran an assessment which determined that green turtles were globally endangered. Population decline in ocean basins
16786-539: The northern Red Sea can reach 41‰. In contrast, some landlocked hypersaline lakes have a much higher salinity, for example, the Dead Sea has 300 grams (11 oz) dissolved solids per litre (300 ‰). While the constituents of table salt ( sodium and chloride ) make up about 85 percent of the solids in solution, there are also other metal ions such as magnesium and calcium , and negative ions including sulphate , carbonate , and bromide . Despite variations in
16940-730: The novel means of travelling westwards. He made landfall instead on an island in the Caribbean Sea and a few years later, the Venetian navigator John Cabot reached Newfoundland . The Italian Amerigo Vespucci , after whom America was named, explored the South American coastline in voyages made between 1497 and 1502, discovering the mouth of the Amazon River . In 1519 the Portuguese navigator Ferdinand Magellan led
17094-484: The ocean depths caused by the movement of deep water masses. A main deep ocean current flows through all the world's oceans and is known as the thermohaline circulation or global conveyor belt. This movement is slow and is driven by differences in density of the water caused by variations in salinity and temperature. At high latitudes the water is chilled by the low atmospheric temperature and becomes saltier as sea ice crystallizes out. Both these factors make it denser, and
17248-440: The ocean on a seasonal basis or vertical migrations daily, often ascending to feed at night and descending to safety by day. Ships can introduce or spread invasive species through the discharge of ballast water or the transport of organisms that have accumulated as part of the fouling community on the hulls of vessels. The demersal zone supports many animals that feed on benthic organisms or seek protection from predators and
17402-471: The ocean, travels through the atmosphere as vapour, condenses , falls as rain or snow , thereby sustaining life on land, and largely returns to the sea. Even in the Atacama Desert , where little rain ever falls, dense clouds of fog known as the camanchaca blow in from the sea and support plant life. In central Asia and other large land masses, there are endorheic basins which have no outlet to
17556-423: The open pelagic zone. The organisms living in the sea range from whales 30 metres (98 feet) long to microscopic phytoplankton and zooplankton , fungi, and bacteria. Marine life plays an important part in the carbon cycle as photosynthetic organisms convert dissolved carbon dioxide into organic carbon and it is economically important to humans for providing fish for use as food. Life may have originated in
17710-795: The organisation was part of a restoration project launched in the Solent , the Solent Seascape Project. In the same year it partnered with Convex Insurance and University of Exeter to launch a global survey to assess carbon captured and stored in the seabed of the continental shelves, the Convex Seascape Survey. In 2023 the charity declared its intention to take the UK government to court for enabling decades of overfishing in UK waters. Marine conservation Marine conservation , also known as ocean conservation ,
17864-434: The past 20 years, said, "There is no doubt that there is a crisis. People have been reporting catching a kilo of glass eels this year when they would expect to catch 40 kilos. We have got to do something." Johnson's seagrass , a food source for the endangered green sea turtle, reproduces asexually , which limits its ability to populate and colonize habitats. This seagrass was formerly the only marine plant to be listed under
18018-462: The population of a certain species cannot be controlled naturally or by human intervention. The domination of one species can create an imbalance in an ecosystem, which can lead to the demise of other species and of the habitat. Overabundance occurs predominately among invasive species . The international shipping trade has led to the establishment of many marine species beyond their native ranges. Some of these can have adverse consequences, such as
18172-636: The population, were collected and sold by villagers in Racho Nuevo, Mexico. In the early 1960s only 5,000 individuals were left, and between 1978 and 1991, 200 Kemp's Ridley Turtles nested annually. In 2015, the World Wildlife Fund and National Geographic Magazine named the Kemp's ridley the most endangered sea turtle in the world, with 1000 females nesting annually. In 2014, the IUCN moved
18326-520: The populations of endangered species through artificial means. Another focus of conservationists is on curtailing human activities that are detrimental to either marine ecosystems or species through policy, techniques such as fishing quotas , like those set up by the Northwest Atlantic Fisheries Organization , or laws such as those listed below. Recognizing the economics involved in human use of marine ecosystems
18480-469: The private sector working together and said the reserve would "double the global coverage of the world's oceans benefiting from full protection". In July 2012, the charity helped start an alliance between fishermen and conservationists in the UK. This alliance was designed to protect Lyme Bay , a reef habitat on the southern coast of the UK. Scallopers and dredgers were banned from part of the bay, but overfishing continued. The deal brokered by Blue Marine and
18634-430: The process of freezing, salt water and air are trapped between the ice crystals. Nilas may have a salinity of 12–15 ‰, but by the time the sea ice is one year old, this falls to 4–6 ‰. Seawater is slightly alkaline and had an average pH of about 8.2 over the past 300 million years. More recently, climate change has resulted in an increase of the carbon dioxide content of the atmosphere; about 30–40% of
18788-418: The quality of the inflowing water. Oceans contain the greatest quantity of actively cycled carbon in the world and are second only to the lithosphere in the amount of carbon they store. The oceans' surface layer holds large amounts of dissolved organic carbon that is exchanged rapidly with the atmosphere. The deep layer's concentration of dissolved inorganic carbon is about 15 percent higher than that of
18942-762: The risk of extinction. Strategies and techniques for marine conservation tend to combine theoretical disciplines, such as population biology, with practical conservation strategies, such as setting up protected areas, as with marine protected areas (MPAs) or Voluntary Marine Conservation Areas . These protected areas may be established for a variety of reasons and aim to limit the impact of human activity. These protected areas operate differently which includes areas that have seasonal closures and/or permanent closures as well as multiple levels of zoning that allow people to carryout different activities in separate areas; including, speed, no take and multi-use zones. Other techniques include developing sustainable fisheries and restoring
19096-417: The rocks. This tends to undercut the cliff, and normal weathering processes such as the action of frost follows, causing further destruction. Gradually, a wave-cut platform develops at the foot of the cliff and this has a protective effect, reducing further wave-erosion. Material worn from the margins of the land eventually ends up in the sea. Here it is subject to attrition as currents flowing parallel to
19250-409: The same way as a wind-generated wave in shallow water but on a vastly greater scale. Either the trough or the crest of a tsunami can arrive at the coast first. In the former case, the sea draws back and leaves subtidal areas close to the shore exposed which provides a useful warning for people on land. When the crest arrives, it does not usually break but rushes inland, flooding all in its path. Much of
19404-479: The sea and all the major groups of animals are represented there. Scientists differ as to precisely where in the sea life arose: the Miller-Urey experiments suggested a dilute chemical "soup" in open water, but more recent suggestions include volcanic hot springs, fine-grained clay sediments, or deep-sea " black smoker " vents, all of which would have provided protection from damaging ultraviolet radiation which
19558-436: The sea could be considered as brackish . Meanwhile, the Red Sea is very salty due to its high evaporation rate. Sea temperature depends on the amount of solar radiation falling on its surface. In the tropics, with the sun nearly overhead, the temperature of the surface layers can rise to over 30 °C (86 °F) while near the poles the temperature in equilibrium with the sea ice is about −2 °C (28 °F). There
19712-537: The sea level has been higher than it is today. The main factor affecting sea level over time is the result of changes in the oceanic crust, with a downward trend expected to continue in the very long term. At the last glacial maximum , some 20,000 years ago, the sea level was about 125 metres (410 ft) lower than in present times (2012). For at least the last 100 years, sea level has been rising at an average rate of about 1.8 millimetres (0.071 in) per year. Most of this rise can be attributed to an increase in
19866-399: The sea under the influence of gravity. A tsunami is an unusual form of wave caused by an infrequent powerful event such as an underwater earthquake or landslide, a meteorite impact, a volcanic eruption or a collapse of land into the sea. These events can temporarily lift or lower the surface of the sea in the affected area, usually by a few feet. The potential energy of the displaced seawater
20020-671: The sea, separated from the ocean by mountains or other natural geologic features that prevent the water draining away. The Caspian Sea is the largest one of these. Its main inflow is from the River Volga , there is no outflow and the evaporation of water makes it saline as dissolved minerals accumulate. The Aral Sea in Kazakhstan and Uzbekistan, and Pyramid Lake in the western United States are further examples of large, inland saline water-bodies without drainage. Some endorheic lakes are less salty, but all are sensitive to variations in
20174-657: The seabed provides a range of habitats on or under the surface of the substrate which are used by creatures adapted to these conditions. The tidal zone with its periodic exposure to the dehydrating air is home to barnacles , molluscs and crustaceans . The neritic zone has many organisms that need light to flourish. Here, among algal-encrusted rocks live sponges , echinoderms , polychaete worms, sea anemones and other invertebrates. Corals often contain photosynthetic symbionts and live in shallow waters where light penetrates. The extensive calcareous skeletons they extrude build up into coral reefs which are an important feature of
20328-427: The seabed. These provide a biodiverse habitat for reef-dwelling organisms. There is less sea life on the floor of deeper seas but marine life also flourishes around seamounts that rise from the depths, where fish and other animals congregate to spawn and feed. Close to the seabed live demersal fish that feed largely on pelagic organisms or benthic invertebrates. Exploration of the deep sea by submersibles revealed
20482-481: The seas, which offers a wide range of marine habitats and ecosystems , ranging vertically from the sunlit surface and shoreline to the great depths and pressures of the cold, dark abyssal zone , and in latitude from the cold waters under polar ice caps to the warm waters of coral reefs in tropical regions . Many of the major groups of organisms evolved in the sea and life may have started there. The ocean moderates Earth's climate and has important roles in
20636-534: The size of Great Britain. The Programme is highly ecologically representative with protected areas in the Pacific, Atlantic, Southern and Indian oceans and the Caribbean. Blue Belt Programme Marine Protected Areas (MPAs) are monitored using satellite technology including Global Fishing Watch and OceanMind, and enforced via coordination between the UK Marine Management Organisation, INTERPOL and other international agencies. In 2022,
20790-418: The slope under the effect of gravity. The larger the breaking waves, the longer the beach and the more oblique the wave approach, the stronger is the longshore current. These currents can shift great volumes of sand or pebbles, create spits and make beaches disappear and water channels silt up. A rip current can occur when water piles up near the shore from advancing waves and is funnelled out to sea through
20944-429: The sun, the weather conditions and the turbidity of the water. Much light gets reflected at the surface, and red light gets absorbed in the top few metres. Yellow and green light reach greater depths, and blue and violet light may penetrate as deep as 1,000 metres (3,300 ft). There is insufficient light for photosynthesis and plant growth beyond a depth of about 200 metres (660 ft). Over most of geologic time,
21098-430: The surface and loops back on itself. It takes a thousand years for this circulation pattern to be completed. Besides gyres, there are temporary surface currents that occur under specific conditions. When waves meet a shore at an angle, a longshore current is created as water is pushed along parallel to the coastline. The water swirls up onto the beach at right angles to the approaching waves but drains away straight down
21252-495: The surface and the mouths of large rivers and higher in the depths of the ocean; however, the relative proportions of dissolved salts vary little across the oceans. The most abundant solid dissolved in seawater is sodium chloride . The water also contains salts of magnesium , calcium , potassium , and mercury , amongst many other elements, some in minute concentrations. A wide variety of organisms , including bacteria , protists , algae , plants, fungi , and animals live in
21406-473: The surface layer and it remains there for much longer periods of time. Thermohaline circulation exchanges carbon between these two layers. Carbon enters the ocean as atmospheric carbon dioxide dissolves in the surface layers and is converted into carbonic acid , carbonate , and bicarbonate : It can also enter through rivers as dissolved organic carbon and is converted by photosynthetic organisms into organic carbon. This can either be exchanged throughout
21560-415: The survivorship and health of marine life and habitat, and benefit fishermen who depend on the resources for profit. Examples of technologies include marine protected areas (MPAs), turtle excluder devices (TEDs), autonomous recording unit , pop-up satellite archival tag , and radio-frequency identification (RFID). Commercial practicality plays an important role in the success of marine conservation because it
21714-526: The symptoms but not the cause of the declines. Examples of halfway technologies include hatcheries and fish ladders. International laws and treaties related to marine conservation include the 1966 Convention on Fishing and Conservation of Living Resources of the High Seas . United States laws related to marine conservation include the 1972 Marine Mammal Protection Act , as well as the 1972 Marine Protection, Research and Sanctuaries Act , which established
21868-453: The temperature of the sea due to climate change , and the resulting slight thermal expansion of the upper 500 metres (1,600 ft) of water. Additional contributions, as much as one quarter of the total, come from water sources on land, such as melting snow and glaciers and extraction of groundwater for irrigation and other agricultural and human needs. Wind blowing over the surface of a body of water forms waves that are perpendicular to
22022-464: The top or bottom of a trawl net, fitting the bars into the "neck" of the shrimp trawl and acting as a filter to ensure that only small animals may pass through. The shrimp will be caught but larger animals such as marine turtles that become caught by the trawler will be rejected by the filter function of the bars. Similarly, halfway technologies work to increase the population of marine organisms. However, they do so without behavioral changes, and address
22176-432: The two can produce broken, irregular seas. Constructive interference can cause individual (unexpected) rogue waves much higher than normal. Most waves are less than 3 m (10 ft) high and it is not unusual for strong storms to double or triple that height; offshore construction such as wind farms and oil platforms use metocean statistics from measurements in computing the wave forces (due to for instance
22330-431: The upper layers, the major part of the ocean exists in permanent darkness. As the different depth and temperature zones each provide habitat for a unique set of species, the marine environment as a whole encompasses an immense diversity of life. Marine habitats range from surface water to the deepest oceanic trenches , including coral reefs, kelp forests , seagrass meadows , tidepools , muddy, sandy and rocky seabeds, and
22484-503: The use of corals as new potential sources for pharmaceuticals (i.e. steroids and anti-inflammatory drugs). Because of the human impact on coral reefs, these ecosystems are becoming increasingly degraded and in need of conservation. The biggest threats include overfishing , destructive fishing practices, sedimentation, and pollution from land-based sources. This, in conjunction with increased carbon in oceans, coral bleaching, and diseases, means that there are no pristine reefs anywhere in
22638-474: The very existence of life on Earth. Sylvia Earle life work has also been shaped directly by Rachel Carson, whose talent she rhapsodizes about in the Introduction to the 2018 edition of Carson’s 1951 best-seller, The Sea Around Us: “Most remarkable to me is what she did imagine. Her writings are so sensitive to the feelings of fish, birds and other animals that she could put herself in their place, buoyed by
22792-460: The water sinks. From the deep sea near Greenland, such water flows southwards between the continental landmasses on either side of the Atlantic. When it reaches the Antarctic, it is joined by further masses of cold, sinking water and flows eastwards. It then splits into two streams that move northwards into the Indian and Pacific Oceans. Here it is gradually warmed, becomes less dense, rises towards
22946-426: The wave reaches a point where its deepest oscillations of the water contact the seabed , they begin to slow down. This pulls the crests closer together and increases the waves' height , which is called wave shoaling . When the ratio of the wave's height to the water depth increases above a certain limit, it " breaks ", toppling over in a mass of foaming water. This rushes in a sheet up the beach before retreating into
23100-504: The wise use of marine resources, particularly through its Regional Seas Program. The sole international legal foundation for regional ocean and sea protection is the Regional Seas Conventions and Action Plans. The Global Programme of Action for the Protection of the Marine Environment from Land-based Activities was also established by UNEP. The relationship between terrestrial, freshwater, coastal, and marine ecosystems
23254-445: The world ocean, so global climate modelling makes use of ocean circulation models as well as models of other major components such as the atmosphere , land surfaces, aerosols and sea ice. Ocean models make use of a branch of physics, geophysical fluid dynamics , that describes the large-scale flow of fluids such as seawater. Surface currents only affect the top few hundred metres of the sea, but there are also large-scale flows in
23408-559: The world. Up to 88% of coral reefs in Southeast Asia are now threatened, with 50% of those reefs at either "high" or "very high" risk of disappearing, which directly affects the biodiversity and survival of species dependent on coral. This is especially harmful to island nations such as Samoa , Indonesia , and the Philippines , because many people there depend on the coral reef ecosystems to feed their families and to make
23562-663: Was a founder member of the Great Blue Ocean coalition, of six NGOs that in 2017 campaigned for the UK Government to establish the Blue Belt Programme widely recognised as one of the world's leading marine conservation initiatives. Ten of the 16 UK Overseas Territories today participate in the programme, in partnership with local communities, the UK Government and NGOs, protecting more than 4.3 million square kilometres of ocean, an area more than 20 times
23716-407: Was not blocked by the early Earth's atmosphere. Marine habitats can be divided horizontally into coastal and open ocean habitats. Coastal habitats extend from the shoreline to the edge of the continental shelf . Most marine life is found in coastal habitats, even though the shelf area occupies only 7 percent of the total ocean area. Open ocean habitats are found in the deep ocean beyond the edge of
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