Marine ecosystems are the largest of Earth's aquatic ecosystems and are distinguished by waters that have a high salt content. These systems contrast with freshwater ecosystems, which have a lower salt content. Marine waters cover more than 70% of the surface of the Earth and account for more than 97% of Earth's water supply and 90% of habitable space on Earth. Marine ecosystems include nearshore systems, such as the salt marshes, mudflats, seagrass meadows, mangroves, rocky intertidal systems and coral reefs. They also extend outwards from the coast to include offshore systems, such as the surface ocean, pelagic ocean waters, the deep sea, oceanic hydrothermal vents, and the sea floor. Marine ecosystems are characterized by the biological community of organisms that they are associated with and their physical environment.
Salt marshes are a transition from the ocean to the land, where fresh and salt water mix. The soil in these marshes is often made up of mud and a layer of organic material called peat. Peat is characterized as waterlogged and root-filled decomposing plant matter that often causes low oxygen levels (hypoxia). These hypoxic conditions are caused the growth of bacteria that also give salt marshes the sulfurous smell they are often known for. Salt marshes exist around the world and are needed for healthy ecosystems and a healthy economy. They are extremely productive ecosystems and they provide essential services for more than 75 percent of fishery species and protect shorelines from erosion and flooding.  Salt marshes can be generally divided into the high marsh, low marsh and the upland border. The low marsh is closer to the ocean, with it being flooded at nearly every tide except low tide.  The high marsh is located between the low marsh and the upland border and it usually only flooded when higher than usual tides are present.  The upland border is the freshwater edge of the marsh and is usually located at elevations slightly higher than the high marsh. This region is usually only flooded under extreme weather conditions and experiences much less waterlogged conditions and salt stress than other areas of the marsh.
Mangroves are trees or shrubs that grow in low-oxygen soil near coastlines in tropical or subtropical latitudes.  They are an extremely productive and complex ecosystem that connects the land and sea. Mangroves consist of species that are not necessarily related to each other, and are often grouped together for the characteristics they share rather than genetic similarity. Because of their proximity to the coast, they have all developed adaptions such as salt excretion and root aeration to live in salty, oxygen-depleted water. Mangroves can often be recognized by their dense tangle of roots that act to protect the coast by reducing erosion from storm surges, currents, wave, and tides. The mangrove ecosystem is also an important source of food for many species as well as excellent at sequestering carbon dioxide from the atmosphere with global mangrove carbon storage being estimated at 34 million metric tons per year. 
Intertidal zones are the areas that are visible and exposed to air during low tide and covered up by saltwater during high tide.  There are four physical divisions of the intertidal zone with each one having its own distinct characteristics and wildlife. These divisions are the Spray zone, High intertidal zone, Middle Intertidal zone and Low intertidal zone. The Spray zone is a damp area that is usually only reached by ocean and submerged only under high tides or storms. The high intertidal zone is submerged at high tide but remains dry for long periods of time between high tides. Due to the large variance of conditions possible in this region, it is inhabited by resilient wildlife that can withstand these changes such as barnacles, marine snails, mussels and hermit crabs. Tides flow over the middle intertidal zone two times a day and this zone has a larger variety of wildlife.  The low intertidal zone is submerged nearly all the time except during the lowest tides and life is more abundant here due to the protection that the water gives. 
Estuaries occur where there is a noticeable change in salinity between saltwater and freshwater sources. This is typically found where rivers meet the ocean or sea. The wildlife found within estuaries is quite unique as the water in these areas is brackish - a mix of freshwater flowing to the ocean and salty seawater.  Other types of estuaries also exist and have similar characteristics as traditional brackish estuaries. The Great Lakes are prime example. There, river water mixes with lake water and creates freshwater estuaries. Estuaries are extremely productive ecosystems that many humans and animal species rely on for various different activities. This can be seen as, of the 32 largest cities in the world, 22 are located on estuaries as they provide many environmental and economic benefits such as crucial habitat for many species, and being economic hubs for many coastal communities. Estuaries also provide essential ecosystem services such as water filtration, habitat protection, erosion control, gas regulation nutrient cycling, and it even gives education, recreation and tourism opportunities to people. 
Lagoons are areas that are separated from larger water by natural barriers such as coral reefs or sandbars. There are two types of lagoons, coastal and oceanic/atoll lagoons. A coastal lagoon is, as the definition above, simply a body of water that is separated from the ocean by a barrier. An atoll lagoon is a circular coral reef, or a number of coral islands that surround a lagoon. Atoll lagoons are often much deeper than coastal lagoons.  Most lagoons are very shallow meaning that they are greatly affected by changed in precipitation, evaporation and wind. This means that salinity and temperature are widely varied in lagoons and that they can have water that ranges from fresh to hypersaline.  Lagoons can be found in on coasts all over the world, on every continent except Antarctica and is an extremely diverse habitat being home to a wide array of species including birds, fish, crabs, plankton and more.  Lagoons are also important to the economy as they provide a wide array of ecosystem services in addition to being the home of so many different species. Some of these services include fisheries, nutrient cycling, flood protection, water filtration and even human tradition.
Coral reefs are one of the most well-known marine ecosystems in the world, with the largest being the Great Barrier Reef. These reefs are composed of large coral colonies of a variety of species living together. The corals form multiple symbiotic relationships with the organisms around them.
The deep sea contains up to 95% of the space occupied by living organisms. Combined with the sea floor (or benthic zone), these two areas have yet to be fully explored and have their organisms documented.
In addition to providing many benefits to the natural world, marine ecosystems also provide social, economic, and biological ecosystem services to humans. Pelagic marine systems regulate the global climate, contribute to the water cycle, maintain biodiversity, provide food and energy resources, and create opportunities for recreation and tourism. Economically, marine systems support billions of dollars worth of capture fisheries, aquaculture, offshore oil and gas, and trade and shipping.
Ecosystem services fall into multiple categories, including supporting services, provisioning services, regulating services, and cultural services.
Although marine ecosystems provide essential ecosystem services, these systems face various threats.
Coastal marine ecosystems experience growing population pressures with nearly 40% of people in the world living within 100 km of the coast. Humans often aggregate near coastal habitats to take advantage of ecosystem services. For example, coastal capture fisheries from mangroves and coral reef habitats are estimated to be worth a minimum of $34 billion per year. Yet, many of these habitats are either marginally protected or not protected. Mangrove area has declined worldwide by more than one-third since 1950, and 60% of the world's coral reefs are now immediately or directly threatened. Human development, aquaculture, and industrialization often lead to the destruction, replacement, or degradation of coastal habitats.
Moving offshore, pelagic marine systems are directly threatened by overfishing. Global fisheries landings peaked in the late 1980s, but are now declining, despite increasing fishing effort. Fish biomass and average trophic level of fisheries landing are decreasing, leading to declines in marine biodiversity. In particular, local extinctions have led to declines in large, long-lived, slow-growing species, and those that have narrow geographic ranges. Biodiversity declines can lead to associated declines in ecosystem services. A long-term study reports the decline of 74–92% of catch per unit effort of sharks in Australian coastline from 1960s to 2010s.
Antigenic shift is the process by which two or more different strains of a virus, or strain of two or more different viruses, combine to form a new subtype having a mixture of the surface antigens of the two or more original strains. The term is often applied specifically to influenza, as that is the best-known example, but the process is also known to occur with other viruses, such as visna virus in sheep. Antigenic shift is a specific case of reassortment or viral shift that confers a phenotypic change.
Antigenic shift is contrasted with antigenic drift, which is the natural mutation over time of known strains of influenza (or other things, in a more general sense) which may lead to a loss of immunity, or in vaccine mismatch. Antigenic drift occurs in all types of influenza including influenzavirus A, influenza B and influenza C. Antigenic shift, however, occurs only in influenzavirus A because it infects more than just humans. Affected species include other mammals and birds, giving influenza A the opportunity for a major reorganization of surface antigens. Influenza B and C principally infect humans, minimizing the chance that a reassortment will change its phenotype drastically.Antigenic shift is important for the emergence of new viral pathogens as it is a pathway that viruses may follow to enter a new niche. It could occur with primate viruses and may be a factor for the appearance of new viruses in the human species such as HIV. Due to the structure of its genome, HIV does not undergo reassortment, but it does recombine freely and via superinfection HIV can produce recombinant HIV strains that differ significantly from their ancestors.COASST
COASST (Coastal Observation and Seabird Survey Team) is a citizen science project of the University of Washington, Seattle, WA, USA, with a vision of monitoring marine ecosystem health with the support of citizens within coastal communities. With the help of hundreds of volunteers from different locations spanning the entire U.S. west coast from Washington to California and into the northern state of Alaska, COASST assesses beach conditions and identifies and tracks any carcasses of dead seabirds found. Data on the carcass of a seabird contributes to creation of a baseline record for the death rates of various species of seabirds including which beaches birds are found at and in what density. Any irregularities can be identified and evaluated so the cause of any increased mortality can be identified. COASST believes citizen scientists partnered with trained scientists create an invaluable relationship that benefits our ability to track and understand marine ecosystems. COASST works closely with state, tribal and federal agencies, environmental organizations and community groups to help this vision of monitoring, and successfully establish marine conservation solutions.Goldeneye (estate)
Goldeneye is the original name of novelist Ian Fleming's estate on Oracabessa bay on the northern coastline of Jamaica. He purchased 15 acres (61,000 m2) adjacent to the Golden Clouds estate in 1946 and built his home on the edge of a cliff overlooking a private beach. The three bedroom structure was constructed from Fleming's sketch, fitted with wooden jalousie windows and a swimming pool. Fleming's visitors at Goldeneye included actors, musicians, and filmmakers. The property now operates as Goldeneye Hotel and Resort, consisting of Fleming's main house and several cottages.
The estate is located in the Oracabessa Bay Fish Sanctuary, established in 2011 to protect the area's marine ecosystem. It is adjacent to James Bond Beach.Greater Farallones National Marine Sanctuary
The Greater Farallones National Marine Sanctuary (formerly Gulf of the Farallones National Marine Sanctuary) protects the wildlife, habitats, and cultural resources of one of the most diverse and bountiful marine environments in the world, an area of 3,295 square miles off the northern and central California coast. The waters within Greater Farallones National Marine Sanctuary are part of a nationally significant marine ecosystem, and support an abundance of life, including many threatened or endangered species.Gulf of Honduras
The Gulf or Bay of Honduras is a large inlet of the Caribbean Sea, indenting the coasts of Belize, Guatemala, and Honduras. From north to south, it runs for approximately 200 km from Dangriga, Belize, to La Ceiba, Honduras.
The inner Gulf of Honduras is lined by the Belize Barrier Reef which forms the southern part of the 900 km long Mesoamerican Barrier Reef System, the second-largest coral reef system in the world. The Belize Barrier Reef includes a number of small islands, called cays, and collectively known as the Pelican Cays.The Gulf of Honduras is marked by complex dynamics of coastal and open waters, and ocean currents, which have produced a very diverse and unique ecosystem with a wide variety of coastal marine waters, including coastline estuaries, barrier beaches, lagoons, intertidal salt marshes, mangrove forests, seagrass beds, keys and barrier reefs.The gulf receives the runoff from the watersheds of 12 rivers with an estimated discharge of 1232 m³ s−1. These rivers include the Moho, Sarstún, Río Dulce, Motagua, and Ulúa. Increased volumes of sediments drained in the Gulf of Honduras pose a threat to its marine ecosystem.Tourists are often taken on boat trips to the Pelican Cays, notably Caye Caulker and Ambergris Caye.
In 1961 Hurricane Hattie swept across the Gulf of Honduras, destroying buildings in Belize.
The infamous pirate Blackbeard spent the winter of 1717–1718 harassing shipping boats sailing to and from the port of Vera Cruz, Mexico and traversing the Bay of Honduras. In April 1718, at Turneffe Atoll, Blackbeard captured the logwood cutting sloop Adventure and forced its captain, David Herriot, to join him. Blackbeard then made Israel Hands captain of the Adventure and began sailing for North Carolina.Large marine ecosystem
Large marine ecosystems (LMEs) are regions of the world's oceans, encompassing coastal areas from river basins and estuaries to the seaward boundaries of continental shelves and the outer margins of the major ocean current systems. They are relatively large regions on the order of 200,000 km² or greater, characterized by distinct bathymetry, hydrography, productivity, and trophically dependent populations. Productivity in LME protected areas is generally higher than in the open ocean.
The system of LMEs has been developed by the US National Oceanic and Atmospheric Administration (NOAA) to identify areas of the oceans for conservation purposes. The objective is to use the LME concept as a tool for enabling ecosystem-based management to provide a collaborative approach to management of resources within ecologically-bounded transnational areas. This will be done in an international context and consistent with customary international law as reflected in 1982 UN Convention on the Law of the Sea.Although the LMEs cover mostly the continental margins and not the deep oceans and oceanic islands, the 66 LMEs produce about 80% of global annual marine fishery biomass. In addition, LMEs contribute $12.6 trillion in goods and services each year to the global economy. Due to their close proximity to developed coastlines, LMEs are in danger of ocean pollution, overexploitation, and coastal habitat alteration. NOAA has conducted studies of principal driving forces affecting changes in biomass yields for 33 of the 66 LMEs, which have been peer-reviewed and published in ten volumes.LME-based conservation is based on recognition that the world’s coastal ocean waters are degraded by unsustainable fishing practices, habitat degradation, eutrophication, toxic pollution, aerosol contamination, and emerging diseases, and that positive actions to mitigate these threats require coordinated actions by governments and civil society to recover depleted fish populations, restore degraded habitats and reduce coastal pollution. Five modules are considered when assessing LMEs: productivity, fish and fisheries, pollution and ecosystem health, socioeconomics, and governance. Periodically assessing the state of each module within a marine LME is encouraged to ensure maintained health of the ecosystem and future benefit to managing governments.Makogai
Makogai (pronounced [makoˈŋai]) is an island belonging to Fiji's Lomaiviti Archipelago. Covering an area of 8.4 square kilometres (2,100 acres), it is situated at 17.26° South and 178.58° East. It has a maximum altitude of 267 metres (876 ft).
The beach forest, cycad dominated, and coastal/marine ecosystem of the island and its surrounding reef contribute to its national significance as outlined in Fiji's Biodiversity Strategy and Action Plan.Makogai is visible from Ovalau. The island used to house a leper colony.Mamanuca Islands
The Mamanuca Islands (Fijian: [mamaˈnuða]) of Fiji are a volcanic archipelago lying to the west of Nadi and to the south of the Yasawa Islands. The group, a popular tourist destination, consists of about 20 islands, but about seven of these are covered by the Pacific Ocean at high tide.
The islands offer crystal clear waters, palm fringed sandy beaches and live coral reefs. There are islands, villages, resorts to visit, snorkel and swim.
The coastal/marine ecosystem and recreation value of the archipelago contribute to its national significance as outlined in Fiji's Biodiversity Strategy and Action Plan.One of the islands, Monuriki, was made famous as the anonymous island that featured in the 2000 Robert Zemeckis film, Cast Away, starring Tom Hanks.Marine Living Resources Act, 18 of 1998
The Marine Living Resources Act, 18 of 1998 is a South African statutory law to provide for the conservation of the marine ecosystem and sustainable utilisation of marine living resources within the territorial waters and exclusive economic zone of the Republic of South Africa.North Atlantic Marine Mammal Commission
The North Atlantic Marine Mammal Commission (NAMMCO) is an "international body for co-operation on conservation, management and study of marine mammals in the North Atlantic."
The NAMMCO Agreement was signed in Nuuk, Greenland on 9 April 1992 by Norway, Iceland, Greenland, and the Faroe Islands, and entered into force 90 days later on 8 July 1992. The agreement focuses on modern approaches to the study of the marine ecosystem as a whole, and better understanding of marine mammals' role in this system.
The body was founded in 1992 by its current members Norway, Iceland, Greenland, and the Faroe Islands. The organization came about because the member nations were (and continue to be) dissatisfied with the international management of cetaceans and other marine mammals by the International Whaling Commission. NAMMCO believes that decisions regarding whaling should be based on scientific principles regarding management of whale populations. Through regional cooperation, the member nations of NAMMCO aim to strengthen and further develop effective conservation and management measures for marine mammals. Such measures should be based on the best available scientific evidence, and should take into account both the complexity and vulnerability of the marine ecosystem, and the rights and needs of coastal communities to make a sustainable living from what the sea can provide.
The IWC currently has a moratorium in effect which prohibits all (large species) whaling with a few specific exceptions. Nations opposed to whaling, such as the United Kingdom, do not recognize NAMMCO's claim to be the proper body for management of whale stocks in the North Atlantic, and continue to support the IWC.Quião Beach, Portugal
Quião Beach (Praia do Quião in Portuguese) is an extensive maritime beach of Póvoa de Varzim, Portugal, located just South of Cape Santo André in the area of A Ver-o-Mar. It has fine to medium sand and several rocky outcrops. The beach is a coastal dune habitat and a rich and diverse marine ecosystem, including large honeycomb reefs. It has a popular beach restaurant, Praia do Mestre.
In northern section of Quião beach, where the waterfront street ends, the traditional Sargassum seaweed gathering is still practiced; it is spread and laid in the beach for sun drying, leaving a pleasant sargassum breeze in the beach, before being pilled to make "medas". This area is protected by dunes, the gneiss. Given its quietude, can be occasionally used naturists, and as a flirting area. It is increasingly popular by other groups of people. In 2016, a boardwalk was built crossing all Cape Santo André, allowing an easy cross of Northern Quião, it is used by the Portuguese Coastal Way of Saint James.Rantau Abang
Rantau Abang is a small village in Terengganu, Malaysia, which used to be noted for its Leatherback Sea Turtle nesting.It is located 22 km north of Kuala Dungun and 80 km south of Kuala Terengganu, Terengganu, Malaysia.
At one time, every year during the months of May to August, the turtles would come ashore and lay their eggs.
However, the number of sea turtles that lay their eggs has severely decreased in recent years. It has been estimated that during the 1950s over 10,000 of these turtles called the beaches on Rantau Abang their sanctuary. Recently the local government declared these turtles extinct as no turtle landings have been sighted for quite some time. The biggest reasons for the decline have been poachers who take the turtle eggs and sell them in local villages, as turtle eggs are a local delicacy, and disturbance from tourists. The Turtle and Marine Ecosystem Centre has been set up in Rantau Abang to spearhead conservation efforts.
The beach is safe for swimming, and is still used for other tourist activities.Santa Barbara Island
Santa Barbara Island (Tongva: Tchunashngna) is a small island of the Channel Islands archipelago in Southern California. It is protected within Channel Islands National Park, and its marine ecosystem is part of the Channel Islands National Marine Sanctuary.Scotian Shelf
The Scotian Shelf is a geological formation, part of the Continental shelf, located southwest of Nova Scotia, Canada. It covers an area of 120,000 km², is 700 km long and ranges in width from 120 to 240 km. It has an average depth of 90 metres. The Scotian Shelf contains the ecologically important Scotian Shelf Large Marine Ecosystem (LME) and the Scotian Shelf Waters (SSW).The northeastern boundary is defined by the Laurentian Channel, where it drops off to 400 m. Further south is the continental slope, which sharply drops off to a depth of more than 3,000 m. The southwestern boundary ends at the Northeast Channel, including the Gulf of Maine.The Scotian Shelf is characterized by shallow, offshore banks 25 m to 100 m under the ocean surface, with deep basins and troughs between that vary in depth from 160 m to 300 m. These culminate at Sable Island.A southwesterly ocean current, (occasionally containing runoff from the Gulf of St Lawrence) flows over the inner shelf. The water flow over the banks is weaker and tends have greater variation. The Scotian Shelf contains a canyon called the "Gully", which is more than 1000 m deep. Currents flow through this canyon southward, mixing offshore waters with the Nova Scotia Current. This causes an increase in biological productivity toward the east, across the Continental Shelf.
The Scotian Shelf is heavily influenced by the Gulf Stream, resulting in a variety of marine species being present which are normally found further south. These appear at regular intervals due to the main current spinning off cores of warm water.Shark culling
Shark culling is the deliberate killing of sharks by government authorities, usually in response to one or more shark attacks. The term "shark control" is often used by governments when referring to culls. Shark culling has been criticized by environmentalists, conservationists and animal welfare advocates — they say killing sharks harms the marine ecosystem and is unethical. Government officials often cite public safety (attempting to reduce the risk of shark attacks) as a reason for culling. The impact of culling is also minor compared to bycatch with 50 million sharks caught each year by the commercial fishing industry.Shark culling mainly occurs in four locations: New South Wales, Queensland, KwaZulu-Natal and Réunion.Carl Meyer, a researcher at the Hawaii Institute of Marine Biology, calls the disagreements about shark culling a "philosophical" debate, about "whether it is ethical to kill large predators in order to make the natural environment a safer playground for humans."South African Institute for Aquatic Biodiversity
The South African Institute for Aquatic Biodiversity (SAIAB), is involved in research, education and in applications of its knowledge and research to African fish fauna, for either economic or conservation benefit.
The institute was formerly named the JLB Smith Institute of Ichthyology, in honour of Professor James Leonard Brierley Smith, who named and described the living coelacanth Latimeria chalumnae.
Situated in Grahamstown in the Eastern Cape, the South African Institute for Aquatic Biodiversity (SAIAB) is an internationally recognised centre for the study of aquatic biodiversity.
As a National Facility of the NRF, SAIAB serves as a major scientific resource for knowledge and understanding the biodiversity and functioning of globally significant aquatic ecosystems. With both marine and freshwater biogeographical boundaries, southern Africa is ideally placed to monitor and document climate change.
From a marine perspective South Africa forms the southern apex of a major continental mass, flanked by very different marine ecosystems on the east and west coasts, and projecting towards the cold southern Ocean large marine ecosystem. SAIAB's scientific leadership and expertise in freshwater aquatic biodiversity is vital to the national interest when dealing with issues arising from exponentially increasing pressures of human population growth and development.Strait of Messina
The Strait of Messina (Italian: Stretto di Messina), is a narrow strait between the eastern tip of Sicily (Punta del Faro) and the western tip of Calabria (Punta Pezzo) in the south of Italy. It connects the Tyrrhenian Sea to the north with the Ionian Sea to the south, within the central Mediterranean. At its narrowest point, between Torre Faro and Villa San Giovanni, it is 3.1 km (1.9 mi) wide. At the town of Messina it is 5.1 km (3.2 mi) wide. The strait's maximum depth is about 250 m (820 ft).
The strait has strong tidal currents that create a unique marine ecosystem. A natural whirlpool in the northern portion of the strait has been linked to the Greek legend of Scylla and Charybdis. In some circumstances, the mirage of Fata Morgana can be observed when looking at Sicily from Calabria. With its bottleneck shape, it is also a compulsory point of transit of the migration of many bird species.
In 1957, a 220 kV overhead power line was built across the Strait of Messina. Its pylons are among the highest in the world. This power line has since been replaced by a submarine power cable, but the pylons remain and are protected as historical monuments (see Pylons of Messina).Teluk Cenderawasih National Park
Teluk Cenderawasih National Park is the largest marine national park of Indonesia, located in Cenderawasih Bay, south-east of Bird's Head Peninsula. It includes the islands of Mioswaar, Nusrowi, Roon, Rumberpon and Yoop. The park protects a rich marine ecosystem, with over 150 recorded coral species, for which it is considered a potential World Heritage Site.Tropical marine climate
A tropical marine climate is a tropical climate that is primarily influenced by the ocean. It is usually experienced by islands and coastal areas 10° to 20° north and south of the equator. There are two main seasons in a tropical marine climate: the wet season and the dry season. The annual rainfall is 1000 to over 1500 mm (39 to 59 inches). The temperature ranges from 20 °C to 35 °C (68 ° to 95 °F). The trade winds blow all year round and are moist, as they pass over warm seas. These climatic conditions are found, for example, across the Caribbean; the eastern coasts of Brazil, Madagascar and Queensland; and many islands in tropical waters.