Mudflat in the context of Pegwell Bay

Marine ecosystems are the largest of Earth's aquatic ecosystems and exist in waters that have a high salt content. These systems contrast with freshwater ecosystems, which have a lower salt content. Marine waters cover more than 70% of the surface of the Earth and account for more than 97% of Earth's water supply and 90% of habitable space on Earth. Seawater has an average salinity of 35 parts per thousand of water. Actual salinity varies among different marine ecosystems. Marine ecosystems can be divided into many zones depending upon water depth and shoreline features. The oceanic zone is the vast open part of the ocean where animals such as whales, sharks, and tuna live. The benthic zone consists of substrates below water where many invertebrates live. The intertidal zone is the area between high and low tides. Other near-shore (neritic) zones can include mudflats, seagrass meadows, mangroves, rocky intertidal systems, salt marshes, coral reefs, kelp forests and lagoons. In the deep water, hydrothermal vents may occur where chemosynthetic sulfur bacteria form the base of the food web.

Marine ecosystems are characterized by the biological community of organisms that they are associated with and their physical environment. Classes of organisms found in marine ecosystems include brown algae, dinoflagellates, corals, cephalopods, echinoderms, and sharks.

A river island is any exposed landmass surrounded by river water. Properly defined, it excludes shoals between seasonally varying flows and may exclude semi-coastal islands in river deltas such as Marajó.

These islands result from changes in the course of a river. Such changes may be caused by interactions with a tributary, or by the opposing fluvial actions of deposition and/or erosion that form a natural cut and meander. Nascent vegetation-free shoals and mudflats may dissipate and shift or build up into such islands through deposition; the process may be assisted through artificial reinforcement or natural factors, such as reeds, palms, evergreen trees or willows, that act as obstacles or erosion barriers, so that water flows around them. Islands may be small or large, covering many square kilometers, examples of which are given below.

Morecambe Bay is an estuary in north-west England, just to the south of the Lake District National Park. It is the largest expanse of intertidal mudflats and sand in the United Kingdom, covering a total area of 120 sq mi (310 km). In 1974, the second largest gas field in the UK was discovered 25 mi (40 km) west of Blackpool, with original reserves of over 7 trillion cubic feet (tcf) (200 billion cubic metres). At its peak, 15% of Britain's gas supply came from the bay but production is now in decline. Morecambe Bay is also an important wildlife site, with abundant birdlife and varied marine habitats.

Clam digging is a North American term for a common way to harvest clams (edible infaunal bivalve mollusks) from below the surface of the tidal sand flats or mudflats where they live. It is done both recreationally (for enjoyment or as a source of food) and commercially (as a source of income). Commercial digging in Canada and the United States is colloquially referred to as clamming, and is done by a clammer.

The intertidal zone or foreshore is the area above water level at low tide and underwater at high tide; in other words, it is the part of the littoral zone within the tidal range. This area can include several types of habitats with various species of life, such as sea stars, sea urchins, and many species of coral with regional differences in biodiversity. Sometimes it is referred to as the littoral zone or seashore, although those can be defined as a wider region.

The intertidal zone also includes steep rocky cliffs, sandy beaches, bogs or wetlands (e.g., vast mudflats). This area can be a narrow strip, such as in Pacific islands that have only a narrow tidal range, or can include many meters of shoreline where shallow beach slopes interact with high tidal excursion. The peritidal zone is similar but somewhat wider, extending from above the highest tide level to below the lowest. Organisms in the intertidal zone are well-adapted to their environment, facing high levels of interspecific competition and the rapidly changing conditions that come with the tides. The intertidal zone is also home to several species from many different phyla (Porifera, Annelida, Coelenterata, Mollusca, Arthropoda, etc.).

Waders or shorebirds are birds of the order Charadriiformes commonly found wading along shorelines and mudflats in order to forage for food crawling or burrowing in the mud and sand, usually small arthropods such as aquatic insects or crustaceans. The term "wader" is used in Europe, while "shorebird" is used in North America, where "wader" may be used instead to refer to long-legged wading birds such as storks and herons.

There are about 255 species of wader, most of which live in wetland or coastal environments. Many species of Arctic and temperate regions are strongly migratory, but tropical birds are often resident, or move only in response to rainfall patterns. Some of the Arctic species, such as the sanderling and grey plover, are amongst the longest distance migrants, spending the non-breeding season in the Southern Hemisphere; the bar-tailed godwit holds the global record for the longest non-stop flight of any bird, some flying over 13,000 km from Alaska to New Zealand.

Nordfriesland (German pronunciation: [nɔʁtˈfʁiːslant] ; Danish: Nordfrisland; North Frisian: Nordfraschlönj [nɔʀdˈfʀaʃlœɲ] Low German: Noordfreesland), also known as North Frisia, is the northernmost district of Germany, part of the state of Schleswig-Holstein. It includes almost all of traditional North Frisia (with the exception of the island of Heligoland), as well as adjacent parts of the Schleswig Geest to the east and Stapelholm to the south, and is bounded (from the east and clockwise) by the districts of Schleswig-Flensburg and Dithmarschen, the North Sea and the Danish county of South Jutland. The district is called Kreis Nordfriesland in German, Kreis Noordfreesland in Low German, Kris Nordfraschlönj in Mooring North Frisian, Kreis Nuurdfresklun in Fering North Frisian and Nordfrislands amt in Danish.

As of 2008, Nordfriesland was the most visited rural district in Germany.

Sundarbans (Bengali: সুন্দরবন; pronounced /sʌnˈdɑːrbənz/) is a mangrove forest area in the Ganges Delta formed by the confluence of the Ganges, Brahmaputra and Meghna Rivers in the Bay of Bengal. It spans the area from the Hooghly River in India's state of West Bengal to the Baleswar River in Bangladesh's Khulna Division. It comprises closed and open mangrove forests, land used for agricultural purpose, mudflats and barren land, and is intersected by multiple tidal streams and channels. Spread across 10,000 km (3,900 sq mi), it is the world's largest mangrove forest. The islands are also of great economic importance as a storm barrier, shore stabiliser, nutrient and sediment trap, a source of timber and natural resources, and support a wide variety of aquatic, benthic and terrestrial organisms. They are an excellent example of the ecological processes of monsoon rain flooding, delta formation, tidal influence and plant colonisation. Covering 133,010 ha, the area is estimated to comprise about 55% forest land and 45% wetlands in the form of tidal rivers, creeks, canals and vast estuarine mouths of the river. About 66% of the entire mangrove forest area is estimated to occur in Bangladesh, with the remaining 34% in India.[1]

Four protected areas in the Sundarbans are enlisted as UNESCO World Heritage Sites, viz. Sundarbans West, Sundarbans South, Sundarbans East in Bangladesh and Sundarbans National Park in India.The Indian Sundarbans were considered endangered in a 2020 assessment under the IUCN Red List of Ecosystems framework. The most abundant tree species are sundri (Heritiera fomes) and gewa (Excoecaria agallocha). The forests provide habitat to 453 fauna wildlife, including 290 bird, 120 fish, 42 mammal, 35 reptile and eight amphibian species. Despite a total ban on all killing or capture of wildlife other than fish and some invertebrates, there has been a consistent pattern of depleted biodiversity or loss of species in the 20th century, with the ecological quality of the forest declining.

The Ubin–Khatib Important Bird Area, also known as the North-East Conservation Area , is an 8940 ha tract of largely undeveloped land in north-eastern Singapore on the border with the Malaysian state of Johor. It encompasses the island of Ubin and much of the islands of Tekong and Tekong Kechil, as well as a coastal strip of the main island, including the Lower Seletar Reservoir, with the intervening coastal waters, seagrass beds, mangroves and intertidal mudflats.

51°34′12″N 2°49′30″W / 51.57°N 2.825°W / 51.57; -2.825

The Caldicot and Wentloog Levels are two areas of low-lying estuarine alluvial wetland and intertidal mudflats adjoining the north bank of the Severn Estuary, either side of the River Usk estuary near Newport in south east Wales. They are also known collectively as the Monmouthshire Levels or Gwent Levels, and the name Wentloog is sometimes spelled Wentlooge in official publications.

Mexicali Municipality is a municipality (Spanish: municipio) in the Mexican state of Baja California. Its municipal seat (Spanish: cabecera municipal) is located in the city of Mexicali. As of 2020, the municipality had a total population of 1,049,792. The municipality has an area of 13,700 km (5,300 sq mi). This includes many smaller outlying communities as well as the city of Mexicali. Also, the islands of Baja California located in the Gulf of California are part of the municipality, among them the mudflat islands at the mouth of the Colorado River (the largest one being Montague Island), Isla Ángel de la Guarda and the islands of San Lorenzo Marine Archipelago National Park. Mexicali is the northernmost municipality of Baja California, Mexico, and Latin America.

The city of Mexicali was founded in 1903, and its name is a portmanteau of Mexico and California, as is the name of Calexico, California across the border.

The pied avocet (Recurvirostra avosetta) is a species of wader in the Recurvirostridae family, the only member of the genus Recurvirostra found in Europe.

This characteristic wader of coastal lagoons and marshes is easily recognizable by its long, upturned bill, long legs, and striking black-and-white plumage. Measuring approximately 40 cm (16 in) in length with a wingspan of about 70 cm (28 in), it is a relatively large species that feeds on various invertebrates in water and mudflats, captured using its distinctive bill. It typically nests in colonies of 10 to 70 pairs on islets or dikes near water, laying usually four eggs in a simple, shallow scrape in the sand. Highly territorial when defending its chicks against conspecifics or predators—such as various raptors, corvids, and mammals—the pied avocet has a lifespan of about 20 years, with a record of 27 years.