# kb

id: zebra-medicine-20260505-0
file: data/en.wikipedia.org/wiki/Zebra_(medicine)-0.md
category: reference
title: Zebra (medicine)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Zebra_(medicine)
date_saved: 2026-05-05T07:34:13.381602+00:00
instance: kb-cron
parent: zebra-medicine-20260505-0
summary:
Zebra is American medical slang for a surprising, often exotic, medical diagnosis, especially when a more commonplace explanation is more likely. It is shorthand for the aphorism coined in the late 1940s by Theodore Woodward, professor at the University of Maryland School of Medicine, who instructed his medical interns: "When you hear hoofbeats behind you, don't expect to see a zebra." (Alternative phrasing: "When you hear hoofbeats, think of horses, not zebras." Since zebras are much rarer than horses in the United States, the sound of hoofbeats would almost certainly be from a horse.) By 1960, the aphorism was widely known in medical circles. The saying is a warning against the statistical base rate fallacy where the likelihood of something like a disease among the population is not taken into consideration for an individual. Medical novices are predisposed to make rare diagnoses because of (a) the availability heuristic ("events more easily remembered are judged more probable") and (b) the phenomenon first enunciated in Rhetorica ad Herennium (c. 85 BC), "the striking and the novel stay longer in the mind." Thus, the aphorism is an important caution against these biases when teaching medical students to weigh medical evidence. Diagnosticians have noted,


id: abyssal-plain-20260505-0
file: data/en.wikipedia.org/wiki/Abyssal_plain-0.md
category: reference
title: Abyssal plain
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Abyssal_plain
date_saved: 2026-05-05T07:34:14.960702+00:00
instance: kb-cron
parent: abyssal-plain-20260505-0
summary:
An abyssal plain is an underwater plain on the deep ocean floor, usually found at depths between 3,000 and 6,000 metres (9,800 and 19,700 ft). Lying generally between the foot of a continental rise and a mid-ocean ridge, abyssal plains cover more than 50% of the Earth's surface. They are among the flattest, smoothest, and least explored regions on Earth. Abyssal plains are key geologic elements of oceanic basins, the other elements being an elevated mid-ocean ridge and flanking abyssal hills. The creation of the abyssal plain is the result of the spreading of the seafloor (plate tectonics) and the melting of the lower oceanic crust. Magma rises from above the asthenosphere (a layer of the upper mantle), and as this basaltic material reaches the surface at mid-ocean ridges, it forms new oceanic crust, which is constantly pulled sideways by spreading of the seafloor. Abyssal plains result from the blanketing of an originally uneven surface of oceanic crust by fine-grained sediments, mainly clay and silt. Much of this sediment is deposited by turbidity currents that have been channelled from the continental margins along submarine canyons into deeper water. The rest is composed chiefly of pelagic sediments. Metallic nodules are common


id: abyssal-plain-20260505-1
file: data/en.wikipedia.org/wiki/Abyssal_plain-1.md
category: reference
title: Abyssal plain
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Abyssal_plain
date_saved: 2026-05-05T07:34:14.960702+00:00
instance: kb-cron
parent: abyssal-plain-20260505-0
summary:
The ocean can be conceptualized as zones, depending on depth, and presence or absence of sunlight. Nearly all life forms in the ocean depend on the photosynthetic activities of phytoplankton and other marine plants to convert carbon dioxide into organic carbon, which is the basic building block of organic matter. Photosynthesis in turn requires energy from sunlight to drive the chemical reactions that produce organic carbon. The stratum of the water column nearest the surface of the ocean (sea level) is referred to as the photic zone. The photic zone can be subdivided into two different vertical regions. The uppermost portion of the photic zone, where there is adequate light to support photosynthesis by phytoplankton and plants, is referred to as the euphotic zone (also referred to as the epipelagic zone, or surface zone). The lower portion of the photic zone, where the light intensity is insufficient for photosynthesis, is called the dysphotic zone (dysphotic means "poorly lit" in Greek). The dysphotic zone is also referred to as the mesopelagic zone, or the twilight zone. Its lowermost boundary is at a thermocline of 12 °C (54 °F), which, in the tropics generally lies between 200 and 1,000 metres (660 and


id: abyssal-plain-20260505-2
file: data/en.wikipedia.org/wiki/Abyssal_plain-2.md
category: reference
title: Abyssal plain
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Abyssal_plain
date_saved: 2026-05-05T07:34:14.960702+00:00
instance: kb-cron
parent: abyssal-plain-20260505-0
summary:
Oceanic crust, which forms the bedrock of abyssal plains, is continuously being created at mid-ocean ridges (a type of divergent boundary) by a process known as decompression melting. Plume-related decompression melting of solid mantle is responsible for creating ocean islands like the Hawaiian islands, as well as the ocean crust at mid-ocean ridges. This phenomenon is also the most common explanation for flood basalts and oceanic plateaus (two types of large igneous provinces). Decompression melting occurs when the upper mantle is partially melted into magma as it moves upwards under mid-ocean ridges. This upwelling magma then cools and solidifies by conduction and convection of heat to form new oceanic crust. Accretion occurs as mantle is added to the growing edges of a tectonic plate, usually associated with seafloor spreading. The age of oceanic crust is therefore a function of distance from the mid-ocean ridge. The youngest oceanic crust is at the mid-ocean ridges, and it becomes progressively older, cooler and denser as it migrates outwards from the mid-ocean ridges as part of the process called mantle convection. The lithosphere, which rides atop the asthenosphere, is divided into a number of tectonic plates that are continuously being created and consumed at


id: abyssal-plain-20260505-3
file: data/en.wikipedia.org/wiki/Abyssal_plain-3.md
category: reference
title: Abyssal plain
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Abyssal_plain
date_saved: 2026-05-05T07:34:14.960702+00:00
instance: kb-cron
parent: abyssal-plain-20260505-0
summary:
Beginning in 1916, Canadian physicist Robert William Boyle and other scientists of the Anti-Submarine Detection Investigation Committee (ASDIC) undertook research which ultimately led to the development of sonar technology. Acoustic sounding equipment was developed which could be operated much more rapidly than the sounding lines, thus enabling the German Meteor expedition aboard the German research vessel Meteor (1925–27) to take frequent soundings on east-west Atlantic transects. Maps produced from these techniques show the major Atlantic basins, but the depth precision of these early instruments was not sufficient to reveal the flat featureless abyssal plains. As technology improved, measurement of depth, latitude and longitude became more precise and it became possible to collect more or less continuous sets of data points. This allowed researchers to draw accurate and detailed maps of large areas of the ocean floor. Use of a continuously recording fathometer enabled Tolstoy & Ewing in the summer of 1947 to identify and describe the first abyssal plain. This plain, south of Newfoundland, is now known as the Sohm Abyssal Plain. Following this discovery many other examples were found in all the oceans. The Challenger Deep is the deepest surveyed point of all of Earth's oceans; it is at


id: abyssal-plain-20260505-4
file: data/en.wikipedia.org/wiki/Abyssal_plain-4.md
category: reference
title: Abyssal plain
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Abyssal_plain
date_saved: 2026-05-05T07:34:14.960702+00:00
instance: kb-cron
parent: abyssal-plain-20260505-0
summary:
Though the plains were once assumed to be vast, desert-like habitats, research over the past decade or so shows that they teem with a wide variety of microbial life. However, ecosystem structure and function at the deep seafloor have historically been poorly studied because of the size and remoteness of the abyss. Recent oceanographic expeditions conducted by an international group of scientists from the Census of Diversity of Abyssal Marine Life (CeDAMar) have found an extremely high level of biodiversity on abyssal plains, with up to 2,000 species of bacteria, 250 species of protozoans, and 500 species of invertebrates (worms, crustaceans and molluscs), typically found at single abyssal sites. New species make up more than 80% of the thousands of seafloor invertebrate species collected at any abyssal station, highlighting our heretofore poor understanding of abyssal diversity and evolution. Richer biodiversity is associated with areas of known phytodetritus input and higher organic carbon flux. Abyssobrotula galatheae, a species of cusk eel in the family Ophidiidae, is among the deepest-living species of fish. In 1970, one specimen was trawled from a depth of 8,370 m (27,460 ft) in the Puerto Rico Trench. The animal was dead, however, upon arrival at the surface.


id: abyssal-plain-20260505-5
file: data/en.wikipedia.org/wiki/Abyssal_plain-5.md
category: reference
title: Abyssal plain
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Abyssal_plain
date_saved: 2026-05-05T07:34:14.960702+00:00
instance: kb-cron
parent: abyssal-plain-20260505-0
summary:
Fueled by the chemicals dissolved in the vent fluids, these areas are often home to large and diverse communities of thermophilic, halophilic and other extremophilic prokaryotic microorganisms (such as those of the sulfide-oxidizing genus Beggiatoa), often arranged in large bacterial mats near cold seeps. In these locations, chemosynthetic archaea and bacteria typically form the base of the food chain. Although the process of chemosynthesis is entirely microbial, these chemosynthetic microorganisms often support vast ecosystems consisting of complex multicellular organisms through symbiosis. These communities are characterized by species such as vesicomyid clams, mytilid mussels, limpets, isopods, giant tube worms, soft corals, eelpouts, galatheid crabs, and alvinocarid shrimp. The deepest seep community discovered thus far is in the Japan Trench, at a depth of 7700 meters. Probably the most important ecological characteristic of abyssal ecosystems is energy limitation. Abyssal seafloor communities are considered to be food limited because benthic production depends on the input of detrital organic material produced in the euphotic zone, thousands of meters above. Most of the organic flux arrives as an attenuated rain of small particles (typically, only 0.5–2% of net primary production in the euphotic zone), which decreases inversely with water depth. The small particle flux can


id: abyssal-plain-20260505-6
file: data/en.wikipedia.org/wiki/Abyssal_plain-6.md
category: reference
title: Abyssal plain
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Abyssal_plain
date_saved: 2026-05-05T07:34:14.960702+00:00
instance: kb-cron
parent: abyssal-plain-20260505-0
summary:
== Exploitation of resources == In addition to their high biodiversity, abyssal plains are of great current and future commercial and strategic interest. For example, they may be used for the legal and illegal disposal of large structures such as ships and oil rigs, radioactive waste and other hazardous waste, such as munitions. They may also be attractive sites for deep-sea fishing, and extraction of oil and gas and other minerals. Future deep-sea waste disposal activities that could be significant by 2025 include emplacement of sewage and sludge, carbon sequestration, and disposal of dredge spoils. As fish stocks dwindle in the upper ocean, deep-sea fisheries are increasingly being targeted for exploitation. Because deep sea fish are long-lived and slow growing, these deep-sea fisheries are not thought to be sustainable in the long term given current management practices. Changes in primary production in the photic zone are expected to alter the standing stocks in the food-limited aphotic zone. Hydrocarbon exploration in deep water occasionally results in significant environmental degradation resulting mainly from accumulation of contaminated drill cuttings, but also from oil spills. While the oil blowout involved in the Deepwater Horizon oil spill in the Gulf of Mexico originates from a


id: abyssal-zone-20260505-0
file: data/en.wikipedia.org/wiki/Abyssal_zone-0.md
category: reference
title: Abyssal zone
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Abyssal_zone
date_saved: 2026-05-05T07:34:16.154926+00:00
instance: kb-cron
parent: abyssal-zone-20260505-0
summary:
The abyssal zone or abyssopelagic zone is a layer of the pelagic zone of the ocean. The word abyss comes from the Greek word ἄβυσσος (ábussos), meaning "bottomless". At depths of 4,000–6,000 m (13,000–20,000 ft), this zone remains in perpetual darkness. It covers 83% of the total area of the ocean and 60% of Earth's surface. The abyssal zone has temperatures around 2–3 °C (36–37 °F) through the large majority of its mass. The water pressure can reach up to 76 MPa (750 atm; 11,000 psi). As there is no light, photosynthesis cannot occur, and there are no plants producing molecular oxygen (O2), which instead primarily comes from ice that had melted long ago from the polar regions. The water along the seafloor of this zone is largely devoid of molecular oxygen, resulting in a death trap for organisms unable to quickly return to the oxygen-enriched water above or to survive in the low-oxygen environment. This region also contains a much higher concentration of nutrient salts, like nitrogen, phosphorus, and silica, due to the large amount of dead organic material that drifts down from the ocean zones above and decomposes. The region below the abyssal zone is the sparsely inhabited


id: abyssal-zone-20260505-1
file: data/en.wikipedia.org/wiki/Abyssal_zone-1.md
category: reference
title: Abyssal zone
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Abyssal_zone
date_saved: 2026-05-05T07:34:16.154926+00:00
instance: kb-cron
parent: abyssal-zone-20260505-0
summary:
== Animals == The abyssal zone is made up of many different types of organisms, including microorganisms, crustaceans, molluscs (bivalves, snails, and cephalopods), different classes of fishes, and possibly some animals that have yet to be discovered. Most of the fish species in this zone are described as demersal or benthopelagic fishes. Demersal fish are fish whose habitats are on or near (typically less than five meters from) the seafloor. Most fish species fit into that classification, because the seafloor contains most of the abyssal zone's nutrients; therefore, the most complex food web or greatest biomass would be in this region of the zone. Organisms in the abyssal zone rely on the natural processes of higher ocean layers. When animals from higher ocean levels die, their carcasses occasionally drift down to the abyssal zone, where organisms in the deep can feed on them. When a whale carcass falls down to the abyssal zone, this is called a whale fall. The carcass of the whale can create complex ecosystems for organisms in the depths. Benthic organisms in the abyssal zone would need to have evolved morphological traits that could either keep them out of oxygen-depleted water above the sea floor or


id: abyssal-zone-20260505-2
file: data/en.wikipedia.org/wiki/Abyssal_zone-2.md
category: reference
title: Abyssal zone
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Abyssal_zone
date_saved: 2026-05-05T07:34:16.154926+00:00
instance: kb-cron
parent: abyssal-zone-20260505-0
summary:
== Environmental concerns == Climate change has had negative effects on the abyssal zone. Due to the zone's depth, increasing global temperatures do not affect it as quickly or drastically as the rest of the world, but the zone is still afflicted by ocean acidification. Pollutants, such as plastics, are also present in this zone. Plastics are especially bad for the abyssal zone because these organisms have evolved to eat or try to eat anything that moves or appears to be detritus, resulting in organisms consuming plastics instead of nutrients. Both ocean acidification and pollution are decreasing the already small biomass that resides within the abyssal zone. Another problem caused by humans is overfishing. Even though no fishery can fish for organisms anywhere near the abyssal zone, they can still cause harm in deeper waters. The abyssal zone depends on dead organisms from the upper zones sinking to the seafloor, since the ecosystem lacks producers due to a lack of sunlight. As fish and other animals are removed from the ocean, the frequency and amount of dead material reaching the abyssal zone decreases. Deep sea mining operations could cause problems for the abyssal zone in the future. The talks and


id: albufera-lagoon-20260505-0
file: data/en.wikipedia.org/wiki/Albufera_(lagoon)-0.md
category: reference
title: Albufera (lagoon)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Albufera_(lagoon)
date_saved: 2026-05-05T07:34:17.363720+00:00
instance: kb-cron
parent: albufera-lagoon-20260505-0
summary:
Albufera (Catalan/Valencian, 'lagoon') is the name of several estuarine lagoons in Spain: Albufera de València, on the Gulf of Valencia Albufera Natural Park, Natural Park in Valencia Albufera de Gaianes, in Gaianes (province of Alicante) S'Albufera de Mallorca, on the island of Mallorca S'Albufereta, also on Mallorca S'Albufera des Grau, on Menorca == See also == Albufeira, a city in Portugal


id: archipelago-20260505-0
file: data/en.wikipedia.org/wiki/Archipelago-0.md
category: reference
title: Archipelago
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Archipelago
date_saved: 2026-05-05T07:34:18.531660+00:00
instance: kb-cron
parent: archipelago-20260505-0
summary:
An archipelago ( AR-kə-PEL-ə-goh), sometimes called an island group or island chain, is a chain, cluster, or collection of islands. An archipelago may be in an ocean, a sea, or a smaller body of water. Examples of archipelagos include the Aegean Islands (the origin of the term archipelago), the Canadian Arctic Archipelago, the Stockholm Archipelago, the Malay Archipelago (which includes the Indonesian and Philippine Archipelagos), the Lucayan (Bahamian) Archipelago, the Japanese archipelago, the Hawaiian Archipelago, and the Galapagos. == Etymology == The word archipelago is derived from the Italian arcipelago (used as a proper name for the Aegean Sea), itself perhaps a deformation of the Greek Αιγαίον Πέλαγος. Usage later shifted to refer to the Aegean Islands (since the sea has a large number of islands). The erudite paretymology, deriving the word from Ancient Greek ἄρχι- (arkhi-, "chief") and πέλαγος (pélagos, "sea"), proposed by Buondelmonti, can still be found. == Geographic types == Archipelagos may be found isolated in large bodies of water or neighboring a large land mass. For example, Scotland has more than 700 islands surrounding its mainland, which form an archipelago. Depending on their geological origin, islands forming archipelagos can be referred to as oceanic islands, continental


id: atoll-20260505-0
file: data/en.wikipedia.org/wiki/Atoll-0.md
category: reference
title: Atoll
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atoll
date_saved: 2026-05-05T07:34:19.794424+00:00
instance: kb-cron
parent: atoll-20260505-0
summary:
An atoll () is a ring-shaped island, including a coral rim that encircles a lagoon. There may be coral islands or cays on the rim. Atolls are located in warm tropical or subtropical parts of the oceans and seas where corals can develop. Most of the approximately 440 atolls in the world are in the Pacific Ocean. Two different, well-cited models, the subsidence model and the antecedent karst model, have been used to explain the development of atolls. According to Charles Darwin's subsidence model, the formation of an atoll is explained by the sinking of a volcanic island around which a coral fringing reef has formed. Over geologic time, the volcanic island becomes extinct and eroded as it subsides completely beneath the surface of the ocean. As the volcanic island subsides, the coral fringing reef becomes a barrier reef that is detached from the island. Eventually, the reef and the small coral islets on top of it are all that is left of the original island, and a lagoon has taken the place of the former volcano. The lagoon is not the former volcanic crater. For the atoll to persist, the coral reef must be maintained at the sea surface,


id: atoll-20260505-1
file: data/en.wikipedia.org/wiki/Atoll-1.md
category: reference
title: Atoll
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atoll
date_saved: 2026-05-05T07:34:19.794424+00:00
instance: kb-cron
parent: atoll-20260505-0
summary:
=== List of atolls === === Gallery === == Formation == In 1842, Charles Darwin explained the creation of coral atolls in the southern Pacific Ocean based upon observations made during a five-year voyage aboard HMS Beagle from 1831 to 1836. Darwin's explanation suggests that several tropical island types: from high volcanic island, through barrier reef island, to atoll, represented a sequence of gradual subsidence of what started as an oceanic volcano. He reasoned that a fringing coral reef surrounding a volcanic island in the tropical sea will grow upward as the island subsides (sinks), becoming an "almost atoll", or barrier reef island, as typified by an island such as Aitutaki in the Cook Islands, and Bora Bora and others in the Society Islands. The fringing reef becomes a barrier reef for the reason that the outer part of the reef maintains itself near sea level through biotic growth, while the inner part of the reef falls behind, becoming a lagoon because conditions are less favorable for the coral and calcareous algae responsible for most reef growth. In time, subsidence carries the old volcano below the ocean surface and the barrier reef remains. At this point, the island has become


id: barrier-island-20260505-0
file: data/en.wikipedia.org/wiki/Barrier_island-0.md
category: reference
title: Barrier island
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Barrier_island
date_saved: 2026-05-05T07:34:21.177659+00:00
instance: kb-cron
parent: barrier-island-20260505-0
summary:
Barrier islands are a coastal landform, a type of dune system and sand island, where an area of sand off the coast has been formed by wave and tidal action parallel to the mainland coast. Barrier islands are commonly formed in long, narrow systems parallel to shorelines and are shaped by waves, tides, sediment movement, and sea-level change, which cause them to shift, grow, or erode over time. They protect coastlines by absorbing energy, and create areas of protected waters where wetlands may flourish. A barrier chain may extend for hundreds of kilometers, with islands periodically separated by tidal inlets. The longest barrier island in the world is Padre Island of Texas, United States, at 113 miles (182 km) long. Sometimes an important inlet may close permanently, transforming an island into a barrier peninsula, often including a barrier beach. Barrier islands are related to other coastal landforms such as barrier beaches and spits, which share similar physical features but differ primarily in their degree of attachment to the mainland and the presence of water on their landward side. Though many are long and narrow, the length and width of barriers and overall morphology of barrier coasts are related to parameters


id: barrier-island-20260505-1
file: data/en.wikipedia.org/wiki/Barrier_island-1.md
category: reference
title: Barrier island
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Barrier_island
date_saved: 2026-05-05T07:34:21.177659+00:00
instance: kb-cron
parent: barrier-island-20260505-0
summary:
=== Critical width concept === Barrier islands are often formed to have a certain width. The term "critical width concept" has been discussed with reference to barrier islands, overwash, and washover deposits since the 1970s. The concept basically states that overwash processes were effective in migration of the barrier only where the barrier width is less than a critical value. The island did not narrow below these values because overwash was effective at transporting sediment over the barrier island, thereby keeping pace with the rate of ocean shoreline recession. Sections of the island with greater widths experienced washover deposits that did not reach the bayshore, and the island narrowed by ocean shoreline recession until it reached the critical width. The only process that widened the barrier beyond the critical width was breaching, formation of a partially subaerial flood shoal, and subsequent inlet closure. Critical barrier width can be defined as the smallest cross-shore dimension that minimizes net loss of sediment from the barrier island over the defined project lifetime. The magnitude of critical width is related to sources and sinks of sand in the system, such as the volume stored in the dunes and the net long-shore and cross-shore sand


id: barrier-island-20260505-2
file: data/en.wikipedia.org/wiki/Barrier_island-2.md
category: reference
title: Barrier island
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Barrier_island
date_saved: 2026-05-05T07:34:21.177659+00:00
instance: kb-cron
parent: barrier-island-20260505-0
summary:
Scientists have proposed numerous explanations for the formation of barrier islands for more than 150 years. There are three major theories: offshore bar, spit accretion, and submergence. No single theory can explain the development of all barriers, which are distributed extensively along the world's coastlines. Scientists accept the idea that barrier islands, including other barrier types, can form by a number of different mechanisms. There appears to be some general requirements for formation. Barrier island systems develop most easily on wave-dominated coasts with a small to moderate tidal range. Coasts are classified into three groups based on tidal range: microtidal, 0–2 meter tidal range; mesotidal, 2–4 meter tidal range; and macrotidal, >4 meter tidal range. Barrier islands tend to form primarily along microtidal coasts, where they tend to be well developed and nearly continuous. They are less frequently formed in mesotidal coasts, where they are typically short with tidal inlets common. Barrier islands are very rare along macrotidal coasts. Along with a small tidal range and a wave-dominated coast, there must be a relatively low gradient shelf. Otherwise, sand accumulation into a sandbar would not occur and instead would be dispersed throughout the shore. An ample sediment supply is also


id: barrier-island-20260505-3
file: data/en.wikipedia.org/wiki/Barrier_island-3.md
category: reference
title: Barrier island
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Barrier_island
date_saved: 2026-05-05T07:34:21.177659+00:00
instance: kb-cron
parent: barrier-island-20260505-0
summary:
=== Wave-dominated === Wave-dominated barrier islands are long, low, and narrow, and usually are bounded by unstable inlets at either end. The presence of longshore currents caused by waves approaching the island at an angle will carry sediment long, extending the island. Longshore currents, and the resultant extension, are usually in one direction, but in some circumstances the currents and extensions can occur towards both ends of the island (as occurs on Anclote Key, Three Rooker Bar, and Sand Key, on the Gulf Coast of Florida). Washover fans on the lagoon side of barriers, where storm surges have over-topped the island, are common, especially on younger barrier islands. Wave-dominated barriers are also susceptible to being breached by storms, creating new inlets. Such inlets may close as sediment is carried in them by longshore currents, but may become permanent if the tidal prism (volumn and force of tidal flow) is large enough. Older barrier islands that have accumulated dunes are less subject to washovers and opening of inlets. Wave-dominated islands require an abundant supply of sediment to grow and develop dunes. If a barrier island does not receive enough sediment to grow, repeated washovers from storms will migrate the island towards


id: bay-20260505-0
file: data/en.wikipedia.org/wiki/Bay-0.md
category: reference
title: Bay
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Bay
date_saved: 2026-05-05T07:34:23.463029+00:00
instance: kb-cron
parent: bay-20260505-0
summary:
A bay is a recessed, coastal body of water that directly connects to a larger main body of water, such as an ocean, a lake, or another bay. A large bay is usually called a gulf, sea, sound, or bight. A cove is a small, circular bay with a narrow entrance. A fjord is an elongated bay formed by glacial action. The term embayment is also used for related features, such as extinct bays or freshwater environments. A bay can be the estuary of a river, such as the Chesapeake Bay, an estuary of the Susquehanna River. Bays may also be nested within each other; for example, James Bay is an arm of Hudson Bay in northeastern Canada. Some bays are large enough to have varied marine geology, such as the Bay of Bengal (2,600,000 km2 or 1,000,000 sq mi) and Hudson Bay (1,230,000 km2 or 470,000 sq mi). The land surrounding a bay often reduces the strength of winds and blocks waves. Bays may have as wide a variety of shoreline characteristics as other shorelines. In some cases, bays have beaches, which "are usually characterized by a steep upper foreshore with a broad, flat fronting terrace". Bays were significant


id: beach-20260505-0
file: data/en.wikipedia.org/wiki/Beach-0.md
category: reference
title: Beach
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Beach
date_saved: 2026-05-05T07:34:24.791061+00:00
instance: kb-cron
parent: beach-20260505-0
summary:
A beach is a landform alongside a body of water which consists of loose particles. The particles composing a beach are typically made from rock, such as sand, gravel, shingle, pebbles, etc., or biological sources, such as mollusc shells or coralline algae. Sediments settle in different densities and structures, depending on the local wave action and weather, creating different textures, colors and gradients or layers of material. Though some beaches form on inland freshwater locations such as lakes and rivers, most beaches are in coastal areas where wave or current action deposits and reworks sediments. Erosion and changing of beach geologies happens through natural processes, like wave action and extreme weather events. Where wind conditions are correct, beaches can be backed by coastal dunes which offer protection and regeneration for the beach. However, these natural forces have become more extreme due to climate change, permanently altering beaches at very rapid rates. Some estimates describe as much as 50 percent of the earth's sandy beaches disappearing by 2100 due to climate-change driven sea level rise. Sandy beaches occupy about one third of global coastlines. These beaches are popular for recreation, playing important economic and cultural roles—often driving local tourism industries. To


id: beach-20260505-1
file: data/en.wikipedia.org/wiki/Beach-1.md
category: reference
title: Beach
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Beach
date_saved: 2026-05-05T07:34:24.791061+00:00
instance: kb-cron
parent: beach-20260505-0
summary:
Beaches are the result of wave action by which waves or currents move sand or other loose sediments of which the beach is made as these particles are held in suspension. Alternatively, sand may be moved by saltation (a bouncing movement of large particles). Beach materials come from erosion of rocks offshore, as well as from headland erosion and slumping producing deposits of scree. A coral reef offshore is a significant source of sand particles. Some species of fish that feed on algae attached to coral outcrops and rocks can create substantial quantities of sand particles over their lifetime as they nibble during feeding, digesting the organic matter, and discarding the rock and coral particles which pass through their digestive tracts. The composition of the beach depends upon the nature and quantity of sediments upstream of the beach, and the speed of flow and turbidity of water and wind. Sediments are moved by moving water and wind according to their particle size and state of compaction. Particles tend to settle and compact in still water. Once compacted, they are more resistant to erosion. Established vegetation (especially species with complex network root systems) will resist erosion by slowing the fluid flow


id: beach-20260505-2
file: data/en.wikipedia.org/wiki/Beach-2.md
category: reference
title: Beach
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Beach
date_saved: 2026-05-05T07:34:24.791061+00:00
instance: kb-cron
parent: beach-20260505-0
summary:
==== Causes ==== Beaches are changed in shape chiefly by the movement of water and wind. Any weather event that is associated with turbid or fast-flowing water or high winds will erode exposed beaches. Longshore currents will tend to replenish beach sediments and repair storm damage. Tidal waterways generally change the shape of their adjacent beaches by small degrees with every tidal cycle. Over time these changes can become substantial leading to significant changes in the size and location of the beach. ==== Effects on flora ==== Changes in the shape of the beach may undermine the roots of large trees and other flora. Many beach adapted species (such as coconut palms) have a fine root system and large root ball which tends to withstand wave and wind action and tends to stabilize beaches better than other trees with a lesser root ball. ==== Effects on adjacent land ==== Erosion of beaches can expose less resilient soils and rocks to wind and wave action leading to undermining of coastal headlands eventually resulting in catastrophic collapse of large quantities of overburden into the shallows. This material may be distributed along the beach front leading to a change in the habitat as


id: beach-20260505-3
file: data/en.wikipedia.org/wiki/Beach-3.md
category: reference
title: Beach
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Beach
date_saved: 2026-05-05T07:34:24.791061+00:00
instance: kb-cron
parent: beach-20260505-0
summary:
==== Concentration of runoff ==== Beaches provide a filter for runoff from the coastal plain. If the runoff is naturally dispersed along the beach, water borne silt and organic matter will be retained on the land and will feed the flora in the coastal area. Runoff that is dispersed along the beach will tend to percolate through the beach and may emerge from the beach at low tide. The retention of the freshwater may also help to maintain underground water reserves and will resist salt water incursion. If the surface flow of the runoff is diverted and concentrated by drains that create constant flows over the beach above the sea or river level, the beach will be eroded and ultimately form an inlet unless longshore flows deposit sediments to repair the breach. Once eroded, an inlet may allow tidal inflows of salt water to pollute areas inland from the beach and may also affect the quality of underground water supplies and the height of the water table. ==== Deprivation of runoff ==== Some flora naturally occurring on the beach head requires freshwater runoff from the land. Diversion of freshwater runoff into drains may deprive these plants of their water supplies


id: beach-20260505-4
file: data/en.wikipedia.org/wiki/Beach-4.md
category: reference
title: Beach
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Beach
date_saved: 2026-05-05T07:34:24.791061+00:00
instance: kb-cron
parent: beach-20260505-0
summary:
The extension of this form of leisure to the middle and working classes began with the development of the railways in the 1840s, which offered cheap fares to fast-growing resort towns. In particular, the completion of a branch line to the small seaside town of Blackpool from Poulton led to a sustained economic and demographic boom. A sudden influx of visitors, arriving by rail, led entrepreneurs to build accommodation and create new attractions, leading to more visitors and a rapid cycle of growth throughout the 1850s and 1860s. The growth was intensified by the practice among the Lancashire cotton mill owners of closing the factories for a week every year to service and repair machinery. These became known as wakes weeks. Each town's mills would close for a different week, allowing Blackpool to manage a steady and reliable stream of visitors over a prolonged period in the summer. A prominent feature of the resort was the promenade and the pleasure piers, where an eclectic variety of performances vied for the people's attention. In 1863, the North Pier in Blackpool was completed, rapidly becoming a centre of attraction for upper class visitors. Central Pier was completed in 1868, with a theatre


id: beach-20260505-5
file: data/en.wikipedia.org/wiki/Beach-5.md
category: reference
title: Beach
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Beach
date_saved: 2026-05-05T07:34:24.791061+00:00
instance: kb-cron
parent: beach-20260505-0
summary:
=== Artificial beaches === Some beaches are artificial; they are either permanent or temporary (For examples, see Copenhagen, Hong Kong, Manila, Monaco, Nottingham, Paris, Rotterdam, Singapore, Tianjin, and Toronto). The soothing qualities of a beach and the pleasant environment offered to the beachgoer are replicated in artificial beaches, such as "beach style" pools with zero-depth entry and wave pools that recreate the natural waves pounding upon a beach. In a zero-depth entry pool, the bottom surface slopes gradually from above water down to depth. Another approach involves so-called urban beaches, a form of public park becoming common in large cities. Urban beaches attempt to mimic natural beaches with fountains that imitate surf and mask city noises, and in some cases can be used as a play park. Beach nourishment involves pumping sand onto beaches to improve their health. Beach nourishment is common for major beach cities around the world; however the beaches that have been nourished can still appear quite natural and often many visitors are unaware of the works undertaken to support the health of the beach. Such beaches are often not recognized by consumers as artificial. A famous example of beach nourishment came with the replenishment of Waikīkī


id: beach-20260505-6
file: data/en.wikipedia.org/wiki/Beach-6.md
category: reference
title: Beach
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Beach
date_saved: 2026-05-05T07:34:24.791061+00:00
instance: kb-cron
parent: beach-20260505-0
summary:
=== Corduroy (beach ladder) === A corduroy road or beach ladder (or board and chain) is an array of planks (usually hardwood or treated timber) laid close together and perpendicular to the direction of traffic flow, and secured at each end by a chain or cable to form a pathway or ramp over the sand dune. Corduroys are cheap and easy to construct and quick to deploy or relocate. They are commonly used for pedestrian access paths and light duty vehicular access ways. They naturally conform to the shape of the underlying beach or dune profile, and adjust well to moderate erosion, especially longshore drift. However, they can cease to be an effective access surface if they become buried or undermined by erosion by surface runoff coming from the beach head. If the corduroy is not wide enough for vehicles using it, the sediment on either side may be displaced creating a spoon drain that accelerates surface runoff and can quickly lead to serious erosion. Significant erosion of the sediment beside and under the corduroy can render it completely ineffective and make it dangerous to pedestrian users who may fall between the planks. === Fabric ramp === Fabric ramps are


id: beach-evolution-20260505-0
file: data/en.wikipedia.org/wiki/Beach_evolution-0.md
category: reference
title: Beach evolution
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Beach_evolution
date_saved: 2026-05-05T07:34:26.041541+00:00
instance: kb-cron
parent: beach-evolution-20260505-0
summary:
Beach evolution is a natural process occurring along shorelines where sea, lake, or river water erodes the land. Beaches form as sand accumulates over centuries through recurrent processes that erode rocky and sedimentary material into sand deposits. River deltas contribute by depositing silt carried from upriver, accreting at the river's outlet to extend lake or ocean shorelines. Catastrophic events such as tsunamis, hurricanes, and storm surges accelerate beach evolution. == Accretion and erosion == === Sudden and rapid processes === ==== Tsunamis and hurricane-driven storm surges ==== Tsunamis can cause significant erosion and sediment displacement. They can strip away years of accumulated sand from beaches and devastate coastal vegetation. These powerful waves can flood inland areas far beyond the typical high-tide mark. Additionally, the swift currents associated with the inundating tsunami can demolish homes and other coastal structures. A storm surge is an onshore gush of water associated with a low pressure weather system. Storm surges can cause beach accretion and erosion. Historically notable storm surges occurred during the North Sea Flood of 1953, Hurricane Katrina, and the 1970 Bhola cyclone. ==== Volcanism and earthquakes related sea-level changes ==== Both geological events and the climate can change (progressively or suddenly)


id: beach-evolution-20260505-1
file: data/en.wikipedia.org/wiki/Beach_evolution-1.md
category: reference
title: Beach evolution
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Beach_evolution
date_saved: 2026-05-05T07:34:26.041541+00:00
instance: kb-cron
parent: beach-evolution-20260505-0
summary:
Abandonment of shore: do nothing, let the natural process takeover. Managed retreat, also called realignment. Hold the shoreline: by using shoreline hardening techniques to create permanent concrete and rock constructions such as groynes. Move beach seaward: by using hard and soft intervention techniques usually in areas of high economic significance. Limited intervention: usually in areas of low economic significance, often includes the succession of haloseres, including salt marshes and sand dunes. === Coastal engineering === Coastal engineering techniques can be classified into two categories: hard engineering methods and soft engineering methods ==== Hard engineering methods ==== Hard engineering methods are also called "Structural methods". "Move towards the sea" beach accretion can be facilitated by the four main type of hard engineering structures, namely seawall, revetment, groyne or breakwater. Most commonly used hard structures are seawall and series of "headland groyne" (breakwater connected to the shore with groyne). ===== Main types of structures ===== Four main types of structures or accropodes are seawalls, groynes, breakwater and revetments. Headland groynes are a combination of breakwater and groyne. ====== Seawalls ====== Seawalls re-direct most of the incident energy in the form of sloping revetments, resulting in low reflected waves and much reduced turbulence.


id: beach-evolution-20260505-2
file: data/en.wikipedia.org/wiki/Beach_evolution-2.md
category: reference
title: Beach evolution
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Beach_evolution
date_saved: 2026-05-05T07:34:26.041541+00:00
instance: kb-cron
parent: beach-evolution-20260505-0
summary:
====== Concrete objects ====== These are complex reinforced concrete objects, such as A-jack, Akmon, Dolos, Honeycomb sea wall (Seabees), KOLOS, Tetrapod and Xbloc. Simple concrete blocks have been replaced by these complex concrete objects because these objects are more resistant to wave action and require less concrete to produce a superior result. These could be used to build seawalls, groynes, breakwaters, and other structures including residential buildings. Tetrapods used along Marine Drive, Mumbai are an example of complex concrete objects. ====== Gabions ====== Gabions are constructed by wiring boulders and rocks into mesh cages and placed in front of areas vulnerable to erosion, sometimes at cliffs edges or at right angles to the beach. When the ocean lands on the gabion, the water drains through leaving sediment, while the structure absorbs a moderate amount of wave energy. Gabions need to be securely tied to protect the structure. They can be used to build seawalls, groynes, breakwaters, revetments, buildings, underwater reefs, etc., ==== Soft engineering methods ==== Soft engineering uses a "soft" (non-permanent) structure by creating a larger sand reservoir, pushing the shoreline seaward. It gained popularity because it preserved beach resources and avoided the negative effects of hard structures. =====


id: beach-evolution-20260505-3
file: data/en.wikipedia.org/wiki/Beach_evolution-3.md
category: reference
title: Beach evolution
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Beach_evolution
date_saved: 2026-05-05T07:34:26.041541+00:00
instance: kb-cron
parent: beach-evolution-20260505-0
summary:
This Integrated coastal zone management example is based on the "move beach seaward" general planning approach which involves both hard and soft engineering methods. This scenario minimizes the maintenance effort and cost by making optimal use of the coastal geography by incorporating natural coastal geographical features in the engineering design. The cost is kept low by the use of easily available free or cost-effective local material, use of which is already known to or easily acquired by the local workforce. This solution entails beach nourishment (creating recreational area by filling with sand), and further beach expansion and prevention of beach erosion caused by longshore drift and coastal development hazards. The design makes use of a shorter groyne slightly inclined toward the beach in the same direction as downdrift, with a series of "headland groyne" perpendicular to the shore, and a longer "headland groyne" at the end of downdrift side of the beach with smaller "headland groyne" perpendicular to it facing the updrift end of the beach. This example of tropical setting, part of the sea could be reclaimed by building a seawall with revetment (slope) fortified with armament of honeycomb seebee made of concrete with hexagonal holes, parts of seawall


id: beach-evolution-20260505-4
file: data/en.wikipedia.org/wiki/Beach_evolution-4.md
category: reference
title: Beach evolution
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Beach_evolution
date_saved: 2026-05-05T07:34:26.041541+00:00
instance: kb-cron
parent: beach-evolution-20260505-0
summary:
==== California beaches ==== California's beaches and other shoreline features change according to the availability of beach sand, the wave and current energy impinging on the coast, and other physical processes that affect the movement of sand. A constant supply of sand is necessary for beaches to form and be maintained along this shoreline. Many human activities, including dam construction and river channelization, have reduced the supply of sand that reaches the ocean. This, in turn, has prevented beaches from being replenished and has thus created greater vulnerability for shorelines that have always been subject to varying levels of erosion. There are few practical solutions to improving sand supply from inland sources, so management of shoreline erosion will likely continue to focus at the land/sea interface along the California coastline. Construction of breakwaters, jetties, or groyne fields to protect harbor entrances, maintain beaches, or protect coastal structures have both helped and harmed the movement of sand along the shoreline. Protective armoring formations trap sand and allow beaches to expand up-coast from the device, but can interrupt the flow of sand to beaches located down-coast. ==== France ==== ===== Atlantic coast ===== Some of the coastal defence bunkers of the Atlantic


id: beachrock-20260505-0
file: data/en.wikipedia.org/wiki/Beachrock-0.md
category: reference
title: Beachrock
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Beachrock
date_saved: 2026-05-05T07:34:27.242877+00:00
instance: kb-cron
parent: beachrock-20260505-0
summary:
Beachrock is a friable to well-cemented sedimentary rock that consists of a variable mixture of gravel-, sand-, and silt-sized sediment that is cemented with carbonate minerals and has formed along a shoreline. Depending on location, the sediment that is cemented to form beachrock can consist of a variable mixture of shells, coral fragments, rock fragments of different types, and other materials. It can also contain scattered artifacts, pieces of wood, and coconuts. Beachrock typically forms within the intertidal zone within tropical or semitropical regions. However, Quaternary beachrock is also found as far north and south as 60° latitude. == Overview == Beachrock units form under a thin cover of sediment and generally overlie unconsolidated sand. They typically consist of multiple units, representing multiple episodes of cementation and exposure. The mineralogy of beachrocks is mainly high-magnesium calcite or aragonite. The main processes involved in the cementation are : supersaturation with CaCO3 through direct evaporation of seawater, groundwater CO2 degassing in the vadose zone, mixing of marine and meteoric water fluxes and precipitation of micritic calcium carbonate as a byproduct of microbiological activity. On retreating coasts, outcrops of beachrock may be evident offshore where they may act as a barrier against coastal


id: benthic-zone-20260505-0
file: data/en.wikipedia.org/wiki/Benthic_zone-0.md
category: reference
title: Benthic zone
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Benthic_zone
date_saved: 2026-05-05T07:34:28.462475+00:00
instance: kb-cron
parent: benthic-zone-20260505-0
summary:
The benthic zone, from Ancient Greek βένθος (bénthos) 'the depths of the ocean', is the ecological region at the lowest level of a body of water, such as a stream, river, lake, or ocean, including the sediment surface and some sub-surface layers. Organisms living in this zone are called benthos, or more informally bottom dwellers. They include microorganisms such as bacteria and fungi, as well as larger invertebrates such as crustaceans and polychaetes. Benthos generally live in close relationship with the substrate and many are permanently attached to the bottom. The benthic boundary layer, which includes the bottom layer of water and the uppermost layer of sediment directly influenced by the overlying water, is an integral part of the benthic zone, as it greatly influences the biological activity that takes place there. Examples of contact soil layers include sand bottoms, rocky outcrops, coral, and bay mud. == Physical description == === Oceans === The benthic region of the ocean begins at the shore line (intertidal or littoral zone) and extends downward along the surface of the continental shelf out to sea. Thus, the region incorporates a great variety of physical conditions differing in depth, light penetration and pressure. The benthic


id: benthic-zone-20260505-1
file: data/en.wikipedia.org/wiki/Benthic_zone-1.md
category: reference
title: Benthic zone
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Benthic_zone
date_saved: 2026-05-05T07:34:28.462475+00:00
instance: kb-cron
parent: benthic-zone-20260505-0
summary:
Benthos is the community of organisms that live in the benthic zone, that is, on, in, or near the bottom of a stream, river, lake, or ocean. This community lives in or near marine or freshwater sedimentary environments, from tidal pools along the foreshore, out to the continental shelf, and then down to the abyssal depths. The term benthos, coined by Haeckel in 1891, comes from the Greek noun βένθος 'depth of the ocean'. Additionally to oceans, benthos is also used in freshwater biology to refer to organisms at the bottom of freshwater bodies of water, such as streams, rivers, and lakes. There is also a redundant, occasionally used synonym, benthon. Benthos is also referred to more loosely and informally as bottom dwellers or bottom feeders. Light is an important energy source for shallow benthic systems. However, because light is absorbed before it can reach deep ocean water, the energy source for deep benthic ecosystems is often organic matter from higher up in the water column that drifts down to the depths. This dead and decaying matter sustains the benthic food chain; most organisms in the benthic zone are scavengers or detritivores. Many organisms adapted to deep-water pressure cannot survive


id: benthic-zone-20260505-2
file: data/en.wikipedia.org/wiki/Benthic_zone-2.md
category: reference
title: Benthic zone
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Benthic_zone
date_saved: 2026-05-05T07:34:28.462475+00:00
instance: kb-cron
parent: benthic-zone-20260505-0
summary:
Both foraminifera and diatoms have planktonic and benthic forms, that is, they can drift in the water column or live on sediment at the bottom of the ocean. Regardless of form, their shells sink to the seafloor after they die. These shells are widely used as climate proxies. The chemical composition of the shells are a consequence of the chemical composition of the ocean at the time the shells were formed. Past water temperatures can be also be inferred from the ratios of stable oxygen isotopes in the shells, since lighter isotopes evaporate more readily in warmer water leaving the heavier isotopes in the shells. Information about past climates can be inferred further from the abundance of forams and diatoms, since they tend to be more abundant in warm water.The sudden extinction event which killed the dinosaurs 66 million years ago also rendered extinct three-quarters of all other animal and plant species. However, deep-sea benthic forams flourished in the aftermath. In 2020 it was reported that researchers have examined the chemical composition of thousands of samples of these benthic forams and used their findings to build the most detailed climate record of Earth ever. Some endoliths have extremely long lives.


id: benthic-zone-20260505-3
file: data/en.wikipedia.org/wiki/Benthic_zone-3.md
category: reference
title: Benthic zone
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Benthic_zone
date_saved: 2026-05-05T07:34:28.462475+00:00
instance: kb-cron
parent: benthic-zone-20260505-0
summary:
=== Nutrient flux === Sources of food for benthic communities can derive from the water column above these habitats in the form of aggregations of detritus, inorganic matter, and living organisms. These aggregations are commonly referred to as marine snow, and are important for the deposition of organic matter, and bacterial communities. The amount of material sinking to the ocean floor can average 307,000 aggregates per m2 per day. This amount will vary on the depth of the benthos, and the degree of benthic-pelagic coupling. The benthos in a shallow region will have more available food than the benthos in the deep sea. Because of their reliance on it, microbes may become spatially dependent on detritus in the benthic zone. The microbes found in the benthic zone, specifically dinoflagellates and foraminifera, colonize quite rapidly on detritus matter while forming a symbiotic relationship with each other. In the deep sea, which covers 90–95% of the ocean floor, 90% of the total biomass is made up of prokaryotes. To release all the nutrients locked inside these microbes to the environment, viruses are important in making it available to other organisms. The main food sources for the benthos are phytoplankton and organic detrital


id: benthic-zone-20260505-4
file: data/en.wikipedia.org/wiki/Benthic_zone-4.md
category: reference
title: Benthic zone
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Benthic_zone
date_saved: 2026-05-05T07:34:28.462475+00:00
instance: kb-cron
parent: benthic-zone-20260505-0
summary:
Benthic macroinvertebrates have many important ecological functions, such as regulating the flow of materials and energy in river ecosystems through their food web linkages. Because of this correlation between flow of energy and nutrients, benthic macroinvertebrates have the ability to influence food resources on fish and other organisms in aquatic ecosystems. For example, the addition of a moderate amount of nutrients to a river over the course of several years resulted in increases in invertebrate richness, abundance, and biomass. These in turn resulted in increased food resources for native species of fish with insignificant alteration of the macroinvertebrate community structure and trophic pathways. The presence of macroinvertebrates such as Amphipoda also affect the dominance of certain types of algae in Benthic ecosystems as well. In addition, because benthic zones are influenced by the flow of dead organic material, there have been studies conducted on the relationship between stream and river water flows and the resulting effects on the benthic zone. Low flow events show a restriction in nutrient transport from benthic substrates to food webs, and caused a decrease in benthic macroinvertebrate biomass, which lead to the disappearance of food sources into the substrate. Because the benthic system regulates energy


id: cape-geography-20260505-0
file: data/en.wikipedia.org/wiki/Cape_(geography)-0.md
category: reference
title: Cape (geography)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cape_(geography)
date_saved: 2026-05-05T07:34:31.991235+00:00
instance: kb-cron
parent: cape-geography-20260505-0
summary:
In geography, a cape is a headland, peninsula or promontory extending into a body of water, usually a sea. A cape usually represents a marked change in trend of the coastline, often making them important landmarks in sea navigation. This also makes them prone to natural forms of erosion, mainly tidal actions, resulting in a relatively short geological lifespan. == Formation == Capes can be formed by glaciers, volcanoes, and changes in sea level. Erosion plays a large role in each of these methods of formation. Coastal erosion by waves and currents can create capes by wearing away softer rock and leaving behind harder rock formations. Movements of the Earth's crust can uplift land, forming capes. For example, the Cape of Good Hope was formed by tectonic forces. Volcanic eruptions can create capes by depositing lava that solidifies into new landforms. Cape Verde, (also known as Cabo Verde) is an example of a volcanic cape. Glaciers can carve out capes by eroding the landscape as they advance and retreat. Cape Cod in the United States was formed by glacial activity during the last Ice Age. == Importance in navigation == Capes (and other headlands) are conspicuous visual landmarks along a


id: capillary-wave-20260505-0
file: data/en.wikipedia.org/wiki/Capillary_wave-0.md
category: reference
title: Capillary wave
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Capillary_wave
date_saved: 2026-05-05T07:34:33.305688+00:00
instance: kb-cron
parent: capillary-wave-20260505-0
summary:
A capillary wave is a wave traveling along the phase boundary of a fluid, whose dynamics and phase velocity are dominated by the effects of surface tension. Capillary waves are common in nature, and are often referred to as ripples. The wavelength of capillary waves on water is typically less than a few centimeters, with a phase speed in excess of 0.2–0.3 meter/second. A longer wavelength on a fluid interface will result in gravity–capillary waves which are influenced by both the effects of surface tension and gravity, as well as by fluid inertia. Ordinary gravity waves have a still longer wavelength. Light breezes upon the surface of water which stir up such small ripples are also sometimes referred to as 'cat's paws'. On the open ocean, much larger ocean surface waves (seas and swells) may result from coalescence of smaller wind-caused ripple-waves. == Dispersion relation == The dispersion relation describes the relationship between wavelength and frequency in waves. Distinction can be made between pure capillary waves – fully dominated by the effects of surface tension – and gravity–capillary waves which are also affected by gravity. === Capillary waves, proper === The dispersion relation for capillary waves is ω 2 =


id: capillary-wave-20260505-1
file: data/en.wikipedia.org/wiki/Capillary_wave-1.md
category: reference
title: Capillary wave
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Capillary_wave
date_saved: 2026-05-05T07:34:33.305688+00:00
instance: kb-cron
parent: capillary-wave-20260505-0
summary:
==== Derivation ==== As Richard Feynman put it, "[water waves] that are easily seen by everyone and which are usually used as an example of waves in elementary courses [...] are the worst possible example [...]; they have all the complications that waves can have." The derivation of the general dispersion relation is therefore quite involved. There are three contributions to the energy, due to gravity, to surface tension, and to hydrodynamics. The first two are potential energies, and responsible for the two terms inside the parenthesis, as is clear from the appearance of g {\displaystyle g} and σ {\displaystyle \sigma } . For gravity, an assumption is made of the density of the fluids being constant (i.e., incompressibility), and likewise g {\displaystyle g} (waves are not high enough for gravitation to change appreciably). For surface tension, the deviations from planarity (as measured by derivatives of the surface) are supposed to be small. For common waves both approximations are good enough. The third contribution involves the kinetic energies of the fluids. It is the most complicated and calls for a hydrodynamic framework. Incompressibility is again involved (which is satisfied if the speed of the waves is much less than the


id: coast-20260505-0
file: data/en.wikipedia.org/wiki/Coast-0.md
category: reference
title: Coast
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Coast
date_saved: 2026-05-05T07:34:34.633460+00:00
instance: kb-cron
parent: coast-20260505-0
summary:
A coast (also called the coastline, shoreline, or seashore) is the land next to the sea or the line that forms the boundary between the land and the ocean or a lake. Coasts are influenced by the topography of the surrounding landscape and by aquatic erosion, such as that caused by waves. The geological composition of rock and soil dictates the type of shore that is created. Earth has about 620,000.0 km (385,250.1 mi) of coastline. Coasts are important zones in natural ecosystems, often home to a wide range of biodiversity. On land, they harbor ecosystems, such as freshwater or estuarine wetlands, that are important for birds and other terrestrial animals. In wave-protected areas, coasts harbor salt marshes, mangroves, and seagrasses, all of which can provide nursery habitat for finfish, shellfish, and other aquatic animals. Rocky shores are usually found along exposed coasts and provide habitat for a wide range of sessile animals (e.g. mussels, starfish, barnacles) and various kinds of seaweeds. In physical oceanography, a shore is the wider fringe that is geologically modified by the action of the body of water past and present, and the beach is at the edge of the shore, including the intertidal zone


id: coast-20260505-1
file: data/en.wikipedia.org/wiki/Coast-1.md
category: reference
title: Coast
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Coast
date_saved: 2026-05-05T07:34:34.633460+00:00
instance: kb-cron
parent: coast-20260505-0
summary:
Tides often determine the range over which sediment is deposited or eroded. Areas with high tidal ranges allow waves to reach farther up the shore, and areas with lower tidal ranges produce deposition at a smaller elevation interval. The tidal range is influenced by the size and shape of the coastline. Tides do not typically cause erosion by themselves; however, tidal bores can erode as the waves surge up the river estuaries from the ocean. Geologists classify coasts on the basis of tidal range into macrotidal coasts with a tidal range greater than 4 m (13 ft); mesotidal coasts with a tidal range of 2 to 4 m (6.6 to 13 ft); and microtidal coasts with a tidal range of less than 2 m (7 ft). The distinction between macrotidal and mesotidal coasts is more important. Macrotidal coasts lack barrier islands and lagoons, and are characterized by funnel-shaped estuaries containing sand ridges aligned with tidal currents. Wave action is much more important for determining bedforms of sediments deposited along mesotidal and microtidal coasts than in macrotidal coasts. Waves erode coastline as they break on shore releasing their energy; the larger the wave the more energy it releases and the more


id: coast-20260505-2
file: data/en.wikipedia.org/wiki/Coast-2.md
category: reference
title: Coast
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Coast
date_saved: 2026-05-05T07:34:34.633460+00:00
instance: kb-cron
parent: coast-20260505-0
summary:
==== Destructive and constructive waves ==== Swash is the shoreward flow after the break, backwash is the water flow back down the beach. The relative strength of flow in the swash and backwash determines what size grains are deposited or eroded. This is dependent on how the wave breaks and the slope of the shore. Depending on the form of the breaking wave, its energy can carry granular material up the beach and deposit it, or erode it by carrying more material down the slope than up it. Steep waves that are close together and break with the surf plunging down onto the shore slope expend much of their energy lifting the sediment. The weak swash does not carry it far up the slope, and the strong backwash carries it further down the slope, where it either settles in deeper water or is carried along the shore by a longshore current induced by an angled approach of the wave-front to the shore. These waves which erode the beach are called destructive waves. Low waves that are further apart and break by spilling, expend more of their energy in the swash which carries particles up the beach, leaving less energy for


id: coast-20260505-3
file: data/en.wikipedia.org/wiki/Coast-3.md
category: reference
title: Coast
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Coast
date_saved: 2026-05-05T07:34:34.633460+00:00
instance: kb-cron
parent: coast-20260505-0
summary:
"Coastal waters" (or "coastal seas") is a term that carries different meanings depending upon the context, ranging from a geographic reference to the waters within a few kilometers of the coast, to describing the entire continental shelf that may stretch for more than a hundred kilometers from land. The term is used in a different manner when describing legal and economic boundaries, such as territorial waters and international waters, or when describing the geography of coastal landforms or the ecological systems operating through the continental shelf (marine coastal ecosystems). The dynamic fluid nature of the ocean means that all components of the whole ocean system are ultimately connected, although certain regional classifications are useful and relevant. The waters of the continental shelves represent such a region. The term "coastal waters" has been used in a wide variety of different ways in different contexts. In European Union environmental management it extends from the coast to just a few nautical miles while in the United States the US EPA considers this region to extend much further offshore. "Coastal waters" has specific meanings in the context of commercial coastal shipping, and somewhat different meanings in the context of naval littoral warfare. Oceanographers and


id: cold-seep-20260505-0
file: data/en.wikipedia.org/wiki/Cold_seep-0.md
category: reference
title: Cold seep
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cold_seep
date_saved: 2026-05-05T07:34:36.156842+00:00
instance: kb-cron
parent: cold-seep-20260505-0
summary:
A cold seep (sometimes called a cold vent) is an area of the ocean floor where seepage of fluids rich in hydrogen sulfide, methane, and other hydrocarbons occurs, often in the form of a brine pool. Cold does not mean that the temperature of the seepage is lower than that of the surrounding sea water; on the contrary, its temperature is often slightly higher. The "cold" is relative to the very warm (at least 60 °C or 140 °F) conditions of a hydrothermal vent. Cold seeps constitute a biome supporting several endemic species. Cold seeps develop unique topography over time, where reactions between methane and seawater create carbonate rock formations and reefs. These reactions may also be dependent on bacterial activity. Ikaite, a hydrous calcium carbonate, can be associated with oxidizing methane at cold seeps. == Types == Types of cold seeps can be distinguished according to the depth, as shallow cold seeps and deep cold seeps. Cold seeps can also be distinguished in detail, as follows: oil/gas seeps gas seeps: methane seeps gas hydrate seeps brine seeps are formed in brine pools pockmarks mud volcanoes == Formation and ecological succession == Cold seeps occur over fissures on the seafloor


id: cold-seep-20260505-1
file: data/en.wikipedia.org/wiki/Cold_seep-1.md
category: reference
title: Cold seep
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cold_seep
date_saved: 2026-05-05T07:34:36.156842+00:00
instance: kb-cron
parent: cold-seep-20260505-0
summary:
=== The Benthic Filter === The organisms living at cold seeps have a large impact on the carbon cycle and on climate. Chemosynthetic organisms, specifically methanogenic (methane-consuming) organisms, prohibit the methane seeping up from beneath the seafloor from being released into the water above. Since methane is such a potent greenhouse gas, methane release could cause global warming when gas hydrate reservoirs destabilized. The consumption of methane by aerobic and anaerobic seafloor life is called "the benthic filter". The first part of this filter is the anaerobic bacteria and archaea underneath the seafloor that consume methane through the anaerobic oxidation of methane (AOM). If the flux of methane flowing through the sediment is too large, and the anaerobic bacteria and archaea are consuming the maximum amount of methane, then the excess methane is consumed by free-floating or symbiotic aerobic bacteria above the sediment at the seafloor. The symbiotic bacteria have been found in organisms such as tube worms and clams living at cold seeps; these organisms provide oxygen to the aerobic bacteria as the bacteria provide energy they obtain from the consumption of methane. Understanding how efficient the benthic filter is can help predict how much methane escapes the seafloor


id: cold-seep-20260505-2
file: data/en.wikipedia.org/wiki/Cold_seep-2.md
category: reference
title: Cold seep
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cold_seep
date_saved: 2026-05-05T07:34:36.156842+00:00
instance: kb-cron
parent: cold-seep-20260505-0
summary:
==== Discoveries ==== The chemosynthetic communities of the Gulf of Mexico have been studied extensively since the 1990s, and communities first discovered on the upper slope are likely the best understood seep communities in the world. The history of the discovery of these remarkable animals has all occurred since the 1980s. Each major discovery was unexpected―from the first hydrothermal vent communities anywhere in the world to the first cold seep communities in the Gulf of Mexico. Communities were discovered in the eastern Gulf of Mexico in 1983 using the crewed submersible DSV Alvin, during a cruise investigating the bottom of the Florida Escarpment in areas of "cold" brine seepage, where they unexpectedly discovered tubeworms and mussels. Two groups fortuitously discovered chemosynthetic communities in the central Gulf of Mexico nearly concurrently in November and December 1984. During investigations in late December on the research vessel R/V Gyre cruise 84-G-12, by Texas A&M University, two bottom trawls were conducted to determine the effects of oil seepage on benthic ecology (until this investigation, all effects of oil seepage were assumed to be detrimental). Trawls unexpectedly recovered extensive collections of chemosynthetic organisms, including tubeworms and clams. a month earlier, LGL Ecological Research Associates was


id: cold-seep-20260505-3
file: data/en.wikipedia.org/wiki/Cold_seep-3.md
category: reference
title: Cold seep
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cold_seep
date_saved: 2026-05-05T07:34:36.156842+00:00
instance: kb-cron
parent: cold-seep-20260505-0
summary:
The widespread nature of Gulf of Mexico chemosynthetic communities was first documented during contracted investigations by the Geological and Environmental Research Group (GERG) of Texas A&M University for the Offshore Operators Committee. This survey remains the most widespread and comprehensive, although numerous additional communities have been documented since that time. Industry exploration for energy reserves in the Gulf of Mexico has also documented numerous new communities through a wide range of depths, including the deepest-known occurrence in the Central Gulf of Mexico in Alaminos Canyon Block 818 at a depth of 2,750 metres (9,020 feet). The occurrence of chemosynthetic organisms dependent on hydrocarbon seepage has been documented in water depths as shallow as 290 metres (950 feet) and as deep as 2,744 metres (9,003 feet). This depth range specifically places chemosynthetic communities in the deepwater region of the Gulf of Mexico, which is defined as water depths greater than 305 metres (1,001 feet). Chemosynthetic communities are not found on the continental shelf, although they do appear in the fossil record in water shallower than 200 metres (660 feet). One theory explaining this is that predation pressure has varied substantially over the time period involved (Callender and Powell 1999). More than


id: cold-seep-20260505-4
file: data/en.wikipedia.org/wiki/Cold_seep-4.md
category: reference
title: Cold seep
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cold_seep
date_saved: 2026-05-05T07:34:36.156842+00:00
instance: kb-cron
parent: cold-seep-20260505-0
summary:
==== Stability ==== According to Sassen (1997) the role of hydrates at chemosynthetic communities has been greatly underestimated. The biological alteration of frozen gas hydrates was first discovered during the MMS study entitled "Stability and Change in Gulf of Mexico Chemosynthetic Communities". It is hypothesized that the dynamics of hydrate alteration could play a major role as a mechanism for regulation of the release of hydrocarbon gases to fuel biogeochemical processes and could also play a substantial role in community stability. Recorded bottom-water temperature excursions of several degrees in some areas such as the Bush Hill site (4–5 °C at 500-metre (1,600-foot) depth) are believed to result in dissociation of hydrates, resulting in an increase in gas fluxes (MacDonald et al., 1994). Although not as destructive as the volcanism at vent sites of the mid-ocean ridges, the dynamics of shallow hydrate formation and movement will clearly affect sessile animals that form part of the seepage barrier. There is potential of a catastrophic event where an entire layer of shallow hydrate could break free of the bottom and considerably affect local communities of chemosynthetic fauna. At deeper depths (>1,000 metres (3,300 feet)), the bottom-water temperature is colder (by approximately 3 °C)


id: cold-seep-20260505-5
file: data/en.wikipedia.org/wiki/Cold_seep-5.md
category: reference
title: Cold seep
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cold_seep
date_saved: 2026-05-05T07:34:36.156842+00:00
instance: kb-cron
parent: cold-seep-20260505-0
summary:
MacDonald et al. (1990) has described four general community types. These are communities dominated by Vestimentiferan tube worms (Lamellibrachia c.f. barhami and Escarpia spp.), mytilid mussels (Seep Mytilid Ia, Ib, and III, and others), vesicomyid clams (Vesicomya cordata and Calyptogena ponderosa), and infaunal lucinid or thyasirid clams (Lucinoma sp. or Thyasira sp.). Bacterial mats are present at all sites visited to date. These faunal groups tend to display distinctive characteristics in terms of how they aggregate, the size of aggregations, the geological and chemical properties of the habitats in which they occur, and, to some degree, the heterotrophic fauna that occur with them. Many of the species found at these cold seep communities in the Gulf of Mexico are new to science and remain undescribed. Individual lamellibrachid tube worms, the longer of two taxa found at seeps, can reach lengths of 3 metres (9.8 feet) and live hundreds of years (Fisher et al., 1997; Bergquist et al., 2000). Growth rates determined from recovered marked tube worms have been variable, ranging from no growth of 13 individuals measured one year to a maximum growth of 9.6 cm/yr (3.8 in/yr) in a Lamellibrachia individual (MacDonald, 2002). Average growth rate was 2.19 cm/yr


id: cold-seep-20260505-6
file: data/en.wikipedia.org/wiki/Cold_seep-6.md
category: reference
title: Cold seep
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cold_seep
date_saved: 2026-05-05T07:34:36.156842+00:00
instance: kb-cron
parent: cold-seep-20260505-0
summary:
Cold-seep communities in the western Atlantic Ocean have also been described from a few dives on mud volcanoes and diapirs between 1,000 and 5,000 m (3,300–16,400 ft) depth in the Barbados accretionary prism area and from the Blake Ridge diapir off North Carolina. More recently, seep communities have been discovered in the eastern Atlantic, on a giant pockmark cluster in the Gulf of Guinea near the Congo deep channel, and also on other pockmarks of the Congo margin, Gabon margin and Nigeria margin and in the Gulf of Cádiz. The occurrence of chemosymbiotic biota in the extensive mud volcano fields of the Gulf of Cádiz was first reported in 2003. The chemosymbiotic bivalves collected from the mud volcanoes of the Gulf of Cadiz were reviewed in 2011. Cold seeps are also known from the Northern Atlantic Ocean, even ranging into the Arctic Ocean, off Canada and Norway. Extensive faunal sampling has been conducted from 400 and 3,300 m (1,300–10,800 ft) in the Atlantic Equatorial Belt from the Gulf of Mexico to the Gulf of Guinea including the Barbados accretionary prism, the Blake Ridge diapir, and in the Eastern Atlantic from the Congo and Gabon margins and the recently explored Nigeria


id: cold-seep-20260505-7
file: data/en.wikipedia.org/wiki/Cold_seep-7.md
category: reference
title: Cold seep
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cold_seep
date_saved: 2026-05-05T07:34:36.156842+00:00
instance: kb-cron
parent: cold-seep-20260505-0
summary:
=== In the Mediterranean === The first biological evidence for reduced environments in the Mediterranean Sea was the presence of Lucinidae and Vesicomyidae bivalve shells cored on the top of the Napoli mud volcano (33°43′52″N 24°40′52″E; "Napoli" is only a name of a seamount. It is located south of Crete), located at 1,900 m deep on the Mediterranean Ridge in the subduction zone of the African Plate. This was followed by the description of a new Lucinidae bivalve species, Lucinoma kazani, associated with bacterial endosymbionts. In the southeastern Mediterranean, communities of polychaetes and bivalves were also found associated with cold seeps and carbonates near Egypt and the Gaza Strip at depths of 500–800 m, but no living fauna was collected. The first in situ observations of extensive living chemosynthetic communities in the eastern Mediterranean Sea prompted cooperation between biologists, geochemists, and geologists. During submersible dives, communities comprising large fields of small bivalves (dead and alive), large siboglinid tube worms, isolated or forming dense aggregations, large sponges, and associated endemic fauna were observed in various cold seep habitats associated with carbonate crusts at 1,700–2,000 m depth. Two mud volcano fields were first explored, one along the Mediterranean Ridge, where most of


id: cold-seep-20260505-8
file: data/en.wikipedia.org/wiki/Cold_seep-8.md
category: reference
title: Cold seep
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cold_seep
date_saved: 2026-05-05T07:34:36.156842+00:00
instance: kb-cron
parent: cold-seep-20260505-0
summary:
==== New Zealand ==== Off the mainland coast of New Zealand, shelf-edge instability is enhanced in some locations by cold seeps of methane-rich fluids that likewise support chemosynthetic faunas and carbonate concretions. Dominant animals are tubeworms of the family Siboglinidae and bivalves of families Vesicomyidae and Mytilidae (Bathymodiolus). Many of its species appear to be endemic. Deep bottom trawling has severely damaged cold seep communities, and those ecosystems are threatened. Cold seeps are found at depths down to 2,000 m, and the topographic and chemical complexity of the habitats are not yet mapped. The scale of new-species discovery in these poorly-studied or unexplored ecosystems is likely to be high. === In the East Pacific === In the deep sea, the COMARGE project has studied the biodiversity patterns along and across the Chilean margin through a complexity of ecosystems such as methane seeps and oxygen minimum zones, reporting that such habitat heterogeneity may influence the biodiversity patterns of the local fauna. Seep fauna include bivalves of families Lucinidae, Thyasiridae, Solemyidae (Acharax sp.), and Vesicomyidae (Calyptogena gallardoi) and polychaetes (Lamellibrachia sp. and two other polychaete species). Furthermore, in these soft reduced sediments below the oxygen minimum zone off the Chilean margin, a


id: cold-seep-20260505-9
file: data/en.wikipedia.org/wiki/Cold_seep-9.md
category: reference
title: Cold seep
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cold_seep
date_saved: 2026-05-05T07:34:36.156842+00:00
instance: kb-cron
parent: cold-seep-20260505-0
summary:
== Environmental impacts == Major threats that cold seep ecosystems and their communities face today are seafloor litter, chemical contaminants, and climate change. Seafloor litter alters the habitat by providing hard substrate where none was available before or by overlying the sediment, thereby inhibiting gas exchange and interfering with organisms on the bottom of the sea. Studies of marine litter in the Mediterranean include surveys of seabed debris on the continental shelf, slope, and bathyal plain. In most studies, plastic items accounted for much of the debris, sometimes as much as 90% or more of the total, owing to their ubiquitous use and poor degradability. Weapons and bombs have also been discarded at sea, and their dumping in open waters contributes to seafloor contamination. Another major threat to the benthic fauna is the presence of lost fishing gear, such as nets and longlines, which contribute to ghost fishing and can damage fragile ecosystems such as cold-water corals. Chemical contaminants such as persistent organic pollutants, toxic metals (e.g., Hg, Cd, Pb, Ni), radioactive compounds, pesticides, herbicides, and pharmaceuticals are also accumulating in deep-sea sediments. Topography (such as canyons) and hydrography (such as cascading events) play a major role in the transportation


id: continental-margin-20260505-0
file: data/en.wikipedia.org/wiki/Continental_margin-0.md
category: reference
title: Continental margin
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Continental_margin
date_saved: 2026-05-05T07:34:37.444285+00:00
instance: kb-cron
parent: continental-margin-20260505-0
summary:
A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. The continental margin consists of three different features: the continental rise, the continental slope, and the continental shelf. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. Continental margins constitute about 28% of the oceanic area. == Subzones == The continental shelf is the relatively shallow water area found in proximity to continents; it is the portion of the continental margin that transitions from the shore out towards the ocean. Continental shelves are believed to make up 7% of the sea floor. The width of continental shelves worldwide varies in the range of 0.03–1500 km. The continental shelf is generally flat, and ends at the shelf break, where there is a drastic increase in slope angle: The mean angle of continental shelves worldwide is 0° 07′, and typically steeper closer to the coastline than it is near the shelf break. At the shelf break begins the continental slope, which can be 1–5 km above the deep-ocean floor. The continental slope often exhibits features called submarine canyons. Submarine canyons often cut into the


id: continental-shelf-20260505-0
file: data/en.wikipedia.org/wiki/Continental_shelf-0.md
category: reference
title: Continental shelf
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Continental_shelf
date_saved: 2026-05-05T07:34:38.658115+00:00
instance: kb-cron
parent: continental-shelf-20260505-0
summary:
A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island is known as an "insular shelf." The continental margin, between the continental shelf and the abyssal plain, comprises a steep continental slope, surrounded by the flatter continental rise, in which sediment from the continent above cascades down the slope and accumulates as a pile of sediment at the base of the slope. Extending as far as 500 km (310 mi) from the slope, it consists of thick sediments deposited by turbidity currents from the shelf and slope. The continental rise's gradient is intermediate between the gradients of the slope and the shelf. Under the United Nations Convention on the Law of the Sea, the name continental shelf was given a legal definition as the stretch of the seabed adjacent to the shores of a particular country to which it belongs. == Topography == The shelf usually ends at a point of increasing slope (called the shelf break). The sea floor below the break is the continental slope.


id: continental-shelf-20260505-1
file: data/en.wikipedia.org/wiki/Continental_shelf-1.md
category: reference
title: Continental shelf
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Continental_shelf
date_saved: 2026-05-05T07:34:38.658115+00:00
instance: kb-cron
parent: continental-shelf-20260505-0
summary:
In shallower water with stronger tides and away from river mouths, tidal turbulence overcomes the stratifying influence of surface heating, and the water column remains well mixed for the entire seasonal cycle. In contrast, in deeper water, the surface heating wins out in summer, to produce seasonal stratification with a warm surface layer overlying the isolated deep water. (The well mixed and seasonally stratifying regimes are separated by persistent features called tidal mixing fronts.) A third regime which links estuaries to shelf seas, Regions of Freshwater Influence (ROFIs), is found where estuaries enter shelf seas, for example in the Liverpool Bay area of the Irish Sea and Rhine Outflow region of the North Sea. Here, stratification can vary on timescales from the semidiurnal tidal cycle through to the springs-neap tidal cycle due to a process known as "tidal straining". While the North Sea and Irish Sea are two of the better studied shelf seas, they are not necessarily representative of all shelf seas as there is a wide variety of behaviours to be found: Indian Ocean shelf seas are dominated by major river systems, including the Ganges and Indus rivers. The shelf seas around New Zealand are complicated because the


id: continental-shelf-20260505-2
file: data/en.wikipedia.org/wiki/Continental_shelf-2.md
category: reference
title: Continental shelf
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Continental_shelf
date_saved: 2026-05-05T07:34:38.658115+00:00
instance: kb-cron
parent: continental-shelf-20260505-0
summary:
== References == Atkinson, Larry P.; Lee, Thomas N.; Blanton, Jackson O.; Chandler, William S. (30 May 1983). "Climatology of the southeastern United States continental shelf waters". Journal of Geophysical Research: Oceans. 88 (C8): 4705–4718. Bibcode:1983JGR....88.4705A. doi:10.1029/JC088iC08p04705. de Haas, Henk; van Weering, Tjeerd C.E; de Stigter, Henko (March 2002). "Organic carbon in shelf seas: sinks or sources, processes and products". Continental Shelf Research. 22 (5): 691–717. Bibcode:2002CSR....22..691D. doi:10.1016/S0278-4343(01)00093-0. "shelf break – geology". Encyclopædia Britannica. Figueiredo, Alberto Garcia; Pacheco, Carlos Eduardo Pereira; de Vasconcelos, Sérgio Cadena; da Silva, Fabiano Tavares (2016). "Continental Shelf Geomorphology and Sedimentology". Geology and Geomorphology: 13–31. doi:10.1016/B978-85-352-8444-7.50009-3. ISBN 9788535284447. Gattuso, Jean-Pierre; Gentili, B.; Duarte, C. M.; Kleypas, J. A.; Middelburg, J. J.; Antoine, D. (2006). "Light availability in the coastal ocean: impact on the distribution of benthic photosynthetic organisms and their contribution to primary production". Biogeosciences. 3 (4). European Geosciences Union: 489–513. Bibcode:2006BGeo....3..489G. doi:10.5194/bg-3-489-2006. hdl:20.500.11937/23744. S2CID 13715554. hal-00330315. Retrieved 1 July 2021. Gross, M. Grant (1972). Oceanography: A View of the Earth. Englewood Cliffs: Prentice-Hall. ISBN 978-0-13-629659-1. Retrieved 12 January 2016. Guihou, K.; Polton, J.; Harle, J.; Wakelin, S.; O'Dea, E.; Holt, J. (January 2018). "Kilometric Scale Modeling of the North West European Shelf Seas: Exploring the


id: continental-shelf-pump-20260505-0
file: data/en.wikipedia.org/wiki/Continental_shelf_pump-0.md
category: reference
title: Continental shelf pump
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Continental_shelf_pump
date_saved: 2026-05-05T07:34:39.905353+00:00
instance: kb-cron
parent: continental-shelf-pump-20260505-0
summary:
In oceanic biogeochemistry, the continental shelf pump is proposed to operate in the shallow waters of the continental shelves, acting as a mechanism to transport carbon (as either dissolved or particulate material) from surface waters to the interior of the adjacent deep ocean. == Overview == Originally formulated by Tsunogai et al. (1999), the pump is believed to occur where the solubility and biological pumps interact with a local hydrography that feeds dense water from the shelf floor into sub-surface (at least subthermocline) waters in the neighbouring deep ocean. Tsunogai et al.'s (1999) original work focused on the East China Sea, and the observation that, averaged over the year, its surface waters represented a sink for carbon dioxide. This observation was combined with others of the distribution of dissolved carbonate and alkalinity and explained as follows : the shallowness of the continental shelf restricts convection of cooling water as a consequence, cooling is greater for continental shelf waters than for neighbouring open ocean waters this leads to the production of relatively cool and dense water on the shelf the cooler waters promote the solubility pump and lead to an increased storage of dissolved inorganic carbon this extra carbon storage is


id: coral-reef-20260505-0
file: data/en.wikipedia.org/wiki/Coral_reef-0.md
category: reference
title: Coral reef
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Coral_reef
date_saved: 2026-05-05T07:34:41.179437+00:00
instance: kb-cron
parent: coral-reef-20260505-0
summary:
A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups. Coral belongs to the class Anthozoa in the animal phylum Cnidaria, which includes sea anemones and jellyfish. Unlike sea anemones, corals secrete hard carbonate exoskeletons that support and protect the coral. Most reefs grow best in warm, shallow, clear, sunny, and agitated water. Coral reefs first appeared 485 million years ago, at the dawn of the Early Ordovician, displacing the microbial and sponge reefs of the Cambrian. Sometimes called rainforests of the sea, shallow coral reefs form some of Earth's most diverse ecosystems. They occupy less than 0.1% of the world's ocean area, about half the area of France. Yet, they provide a home for at least 25% of all marine species, including fish, mollusks, worms, crustaceans, echinoderms, sponges, tunicates and other cnidarians. Coral reefs flourish in ocean waters that provide few nutrients. They are most commonly found at shallow depths in tropical waters, but deep water and cold water coral reefs exist on smaller scales in other areas. Shallow tropical coral reefs


id: coral-reef-20260505-1
file: data/en.wikipedia.org/wiki/Coral_reef-1.md
category: reference
title: Coral reef
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Coral_reef
date_saved: 2026-05-05T07:34:41.179437+00:00
instance: kb-cron
parent: coral-reef-20260505-0
summary:
=== Material === As the name implies, coral reefs are made up of coral skeletons from mostly intact coral colonies. As other chemical elements present in corals become incorporated into the calcium carbonate deposits, aragonite is formed. However, shell fragments and the remains of coralline algae such as the green-segmented genus Halimeda can add to the reef's ability to withstand damage from storms and other threats. Such mixtures are visible in structures such as Eniwetok Atoll. === In the geologic past === The times of maximum reef development were in the Middle Cambrian (513–501 Ma), Devonian (416–359 Ma) and Carboniferous (359–299 Ma), owing to extinct order Rugosa corals, and Late Cretaceous (100–66 Ma) and Neogene (23 Ma–present), owing to order Scleractinia corals. Not all reefs in the past were formed by corals: those in the Early Cambrian (542–513 Ma) resulted from calcareous algae and archaeocyathids (small animals with conical shape, probably related to sponges) and in the Late Cretaceous (100–66 Ma), when reefs formed by a group of bivalves called rudists existed; one of the valves formed the main conical structure and the other, much smaller valve acted as a cap. Measurements of the oxygen isotopic composition of the aragonitic


id: coral-reef-20260505-2
file: data/en.wikipedia.org/wiki/Coral_reef-2.md
category: reference
title: Coral reef
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Coral_reef
date_saved: 2026-05-05T07:34:41.179437+00:00
instance: kb-cron
parent: coral-reef-20260505-0
summary:
Atolls or atoll reefs are a more or less circular or continuous barrier reef that extends all the way around a lagoon without a central island. They are usually formed from fringing reefs around volcanic islands. Over time, the island erodes away and sinks below sea level. Atolls may also be formed by the sinking of the seabed or rising of the sea level. A ring of reefs results, which encloses a lagoon. Atolls are numerous in the South Pacific, where they usually occur in mid-ocean, for example, in the Caroline Islands, the Cook Islands, French Polynesia, the Marshall Islands, and Micronesia. Atolls are found in the Indian Ocean, for example, in the Maldives, the Chagos Islands, the Seychelles, and around Cocos Island. The entire Maldives consists of 26 atolls. === Other reef types or variants === Apron reef – short reef resembling a fringing reef, but more sloped; extending out and downward from a point or peninsular shore. The initial stage of a fringing reef. Bank reef – isolated, flat-topped reef larger than a patch reef and usually on mid-shelf regions and linear or semi-circular in shape; a type of platform reef. Patch reef – common, isolated, comparatively small


id: coral-reef-20260505-3
file: data/en.wikipedia.org/wiki/Coral_reef-3.md
category: reference
title: Coral reef
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Coral_reef
date_saved: 2026-05-05T07:34:41.179437+00:00
instance: kb-cron
parent: coral-reef-20260505-0
summary:
The reef surface is the shallowest part of the reef. It is subject to surge and tides. When waves pass over shallow areas, they shoal, as shown in the adjacent diagram. This means the water is often agitated. These are the precise conditions under which corals flourish. The light is sufficient for photosynthesis by the symbiotic zooxanthellae, and agitated water brings plankton to feed the coral. The off-reef floor is the shallow sea floor surrounding a reef. This zone occurs next to reefs on continental shelves. Reefs around tropical islands and atolls drop abruptly to great depths and do not have such a floor. Usually sandy, the floor often supports seagrass meadows, which are important foraging areas for reef fish. The reef drop-off is, for its first 50 m, habitat for reef fish who find shelter on the cliff face and plankton in the water nearby. The drop-off zone primarily occurs around oceanic islands and atolls. The reef face is the zone above the reef floor or the reef drop-off. This zone is often the reef's most diverse area. Coral and calcareous algae provide complex habitats and areas that offer protection, such as cracks and crevices. Invertebrates and epiphytic algae


id: coral-reef-20260505-4
file: data/en.wikipedia.org/wiki/Coral_reef-4.md
category: reference
title: Coral reef
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Coral_reef
date_saved: 2026-05-05T07:34:41.179437+00:00
instance: kb-cron
parent: coral-reef-20260505-0
summary:
The Great Barrier Reef—largest, comprising over 2,900 individual reefs and 900 islands stretching for over 2,600 kilometers (1,600 mi) off Queensland, Australia The Mesoamerican Barrier Reef System—second largest, stretching 1,000 kilometers (620 mi) from Isla Contoy at the tip of the Yucatán Peninsula down to the Bay Islands of Honduras The New Caledonia Barrier Reef—second longest double barrier reef, covering 1,500 kilometers (930 mi) The Andros, Bahamas Barrier Reef—third largest, following the east coast of Andros Island, Bahamas, between Andros and Nassau The Red Sea—includes 6,000-year-old fringing reefs located along a 2,000 km (1,240 mi) coastline The Florida Reef Tract—largest continental US reef and the third-largest coral barrier reef, extends from Soldier Key, located in Biscayne Bay, to the Dry Tortugas in the Gulf of Mexico Blake Plateau has the world's largest known deep-water coral reef, comprising a 6.4 million-acre reef that stretches from Miami to Charleston, S. C. Its discovery was announced in January 2024. Pulley Ridge—deepest photosynthetic coral reef, Florida Numerous reefs around the Maldives The Philippines coral reef area, the second-largest in Southeast Asia, is estimated at 26,000 square kilometres. They are populated by over 900 reef fish species and 400 scleractinian coral species, 12 of which


id: coral-reef-20260505-5
file: data/en.wikipedia.org/wiki/Coral_reef-5.md
category: reference
title: Coral reef
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Coral_reef
date_saved: 2026-05-05T07:34:41.179437+00:00
instance: kb-cron
parent: coral-reef-20260505-0
summary:
Corals reproduce both sexually and asexually. An individual polyp uses both reproductive modes within its lifetime. Corals reproduce sexually by either internal or external fertilization. The reproductive cells are found on the mesenteries, membranes that radiate inward from the layer of tissue that lines the stomach cavity. Some mature adult corals are hermaphroditic; others are exclusively male or female. A few species change sex as they grow. Internally fertilized eggs develop in the polyp for a period ranging from days to weeks. Subsequent development produces a tiny larva, known as a planula. Externally fertilized eggs develop during synchronized spawning. Polyps across a reef simultaneously release eggs and sperm into the water en masse. Spawn disperse over a large area. The timing of spawning depends on the time of year, water temperature, and tidal and lunar cycles. Spawning is most successful when there is little variation between high and low tide. The less water movement, the better the chance for fertilization. The release of eggs or planula usually occurs at night and is sometimes in phase with the lunar cycle (three to six days after a full moon). The period from release to settlement lasts only a few days, but some


id: coral-reef-20260505-6
file: data/en.wikipedia.org/wiki/Coral_reef-6.md
category: reference
title: Coral reef
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Coral_reef
date_saved: 2026-05-05T07:34:41.179437+00:00
instance: kb-cron
parent: coral-reef-20260505-0
summary:
In The Structure and Distribution of Coral Reefs, published in 1842, Darwin described how coral reefs were found in some tropical areas but not others, with no obvious cause. The largest and strongest corals grew in parts of the reef exposed to the most violent surf, and corals were weakened or absent where loose sediment accumulated. Tropical waters contain few nutrients yet a coral reef can flourish like an "oasis in the desert". This has given rise to the ecosystem conundrum, sometimes called "Darwin's paradox": "How can such high production flourish in such nutrient poor conditions?" Coral reefs support over one-quarter of all marine species. This diversity results in complex food webs, with large predator fish eating smaller forage fish, which eat yet smaller zooplankton, and so on. However, all food webs ultimately depend on plants, which serve as primary producers. Coral reefs typically produce 5–10 grams of carbon per square meter per day (gC·m−2·day−1) biomass. One reason for the unusual clarity of tropical waters is their nutrient deficiency and drifting plankton. Further, the sun shines year-round in the tropics, warming the surface layer, making it less dense than subsurface layers. The warmer water is separated from deeper, cooler water


id: coral-reef-20260505-7
file: data/en.wikipedia.org/wiki/Coral_reef-7.md
category: reference
title: Coral reef
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Coral_reef
date_saved: 2026-05-05T07:34:41.179437+00:00
instance: kb-cron
parent: coral-reef-20260505-0
summary:
== Biodiversity == Coral reefs form some of the world's most productive ecosystems, providing complex and varied marine habitats that support a wide range of organisms. Fringing reefs just below low tide level have a mutually beneficial relationship with mangrove forests at high tide level and sea grass meadows in between: the reefs protect the mangroves and seagrass from strong currents and waves that would damage them or erode the sediments in which they are rooted, while the mangroves and sea grass protect the coral from large influxes of silt, fresh water and pollutants. This level of environmental variety benefits many coral reef animals, which, for example, may feed on seagrass and use the reefs for protection or breeding. Reefs are home to a variety of animals, including fish, seabirds, sponges, cnidarians (which includes some types of corals and jellyfish), worms, crustaceans (including shrimp, cleaner shrimp, spiny lobsters and crabs), mollusks (including cephalopods), echinoderms (including starfish, sea urchins and sea cucumbers), sea squirts, sea turtles and sea snakes. Aside from humans, mammals are rare on coral reefs, with visiting cetaceans such as dolphins being the main exception. A few species feed directly on corals, while others graze on algae on


id: coral-reef-20260505-8
file: data/en.wikipedia.org/wiki/Coral_reef-8.md
category: reference
title: Coral reef
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Coral_reef
date_saved: 2026-05-05T07:34:41.179437+00:00
instance: kb-cron
parent: coral-reef-20260505-0
summary:
== Ecosystem services == Coral reefs deliver ecosystem services to tourism, fisheries, and coastline protection. The global economic value of coral reefs has been estimated to be between US$29.8 billion and $375 billion per year. About 500 million people benefit from ecosystem services provided by coral reefs. The economic cost of destroying one square kilometre of coral reef over 25 years has been estimated at between $137,000 and $1,200,000. To improve the management of coastal coral reefs, the World Resources Institute (WRI) developed and published tools to calculate the value of coral reef-related tourism, shoreline protection, and fisheries, partnering with five Caribbean countries. As of April 2011, published working papers covered St. Lucia, Tobago, Belize, and the Dominican Republic. The WRI was "making sure that the study results support improved coastal policies and management planning". The Belize study estimated the value of reef and mangrove services at $395–559 million annually. Bermuda's coral reefs provide economic benefits to the Island worth, on average, $722 million per year, based on six key ecosystem services, according to Sarkis et al. (2010). === Shoreline protection === Coral reefs protect shorelines by absorbing wave energy, and many small islands would not exist without reefs. Coral


id: coral-reef-20260505-9
file: data/en.wikipedia.org/wiki/Coral_reef-9.md
category: reference
title: Coral reef
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Coral_reef
date_saved: 2026-05-05T07:34:41.179437+00:00
instance: kb-cron
parent: coral-reef-20260505-0
summary:
Marine protected areas (MPAs) are areas designated because they provide various kinds of protection to ocean and/or estuarine areas. They are intended to promote responsible fishery management and habitat protection. MPAs can also encompass social and biological objectives, including reef restoration, aesthetics, biodiversity, and economic benefits. The effectiveness of MPAs is still debated. For example, a study investigating the success of a small number of MPAs in Indonesia, the Philippines, and Papua New Guinea found no significant differences between the MPAs and unprotected sites. Furthermore, in some cases they can generate local conflict, due to a lack of community participation, clashing views of the government and fisheries, effectiveness of the area and funding. In some situations, as in the Phoenix Islands Protected Area, MPAs provide revenue to locals. The level of income provided is similar to the income they would have generated without controls. Overall, it appears the MPAs can protect local coral reefs, but that clear management and sufficient funds are required. The Caribbean Coral Reefs – Status Report 1970–2012 states that coral decline may be reduced or even reversed. For this, overfishing needs to be stopped, especially fishing on species key to coral reefs, such as parrotfish. Direct


id: coral-reef-20260505-10
file: data/en.wikipedia.org/wiki/Coral_reef-10.md
category: reference
title: Coral reef
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Coral_reef
date_saved: 2026-05-05T07:34:41.179437+00:00
instance: kb-cron
parent: coral-reef-20260505-0
summary:
Coral gardens take advantage of a coral's natural ability to fragment and continue to grow if the fragments can anchor themselves onto new substrates. This method was first tested by Baruch Rinkevich in 1995 which found success at the time. By today's standards, coral farming has evolved into various forms, but it still aims to cultivate corals. Consequently, coral farming quickly replaced previously used transplantation methods, which involved physically moving sections or entire coral colonies to a new area. Transplantation has seen success in the past, and decades of experiments have led to a high success and survival rate. However, this method still requires removing corals from existing reefs. Given the current state of reefs, this method should generally be avoided if possible. Saving healthy corals from eroding substrates or reefs doomed to collapse could be a significant advantage of using transplantation. Coral gardens generally take on safe forms, no matter where you go. It begins with the establishment of a nursery where operators can observe and care for coral fragments. It goes without saying that nurseries should be established in areas that are going to maximize growth and minimize mortality. Floating offshore coral trees or even aquariums are possible


id: coral-reef-20260505-11
file: data/en.wikipedia.org/wiki/Coral_reef-11.md
category: reference
title: Coral reef
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Coral_reef
date_saved: 2026-05-05T07:34:41.179437+00:00
instance: kb-cron
parent: coral-reef-20260505-0
summary:
=== Heat-tolerant symbionts === Another possibility for coral restoration is gene therapy: inoculating coral with genetically modified bacteria, or naturally occurring heat-tolerant varieties of coral symbiotes, may make it possible to grow corals that are more resistant to climate change and other threats. Warming oceans are forcing corals to adapt to unprecedented temperatures. Those that do not have a tolerance for the elevated temperatures experience coral bleaching and eventually mortality. There is already research aimed at creating genetically modified corals that can withstand a warming ocean. Madeleine J. H. van Oppen, James K. Oliver, Hollie M. Putnam, and Ruth D. Gates described four levels of human intervention for genetically modifying corals, each increasing in intensity. These methods focus on altering the genetics of the zooxanthellae within coral rather than the alternative. The first method is to induce acclimatization of the first generation of corals. The idea is that when adult and offspring corals are exposed to stressors, the zooxanthellae will gain a mutation. This method is based primarily on the chance that the zooxanthellae will acquire the specific trait that will enable them to better survive in warmer waters. The second method focuses on identifying the different kinds of zooxanthellae


id: coral-reef-20260505-12
file: data/en.wikipedia.org/wiki/Coral_reef-12.md
category: reference
title: Coral reef
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Coral_reef
date_saved: 2026-05-05T07:34:41.179437+00:00
instance: kb-cron
parent: coral-reef-20260505-0
summary:
Deep-water coral — Corals living in the cold waters of deeper, darker parts of the oceans Mesophotic coral reef — Corals living in the mesopelagic or twilight zone Fossil Coral Reef – National Natural Landmark in Le Roy, New York Census of Coral Reefs – Field project of the Census of Marine Life Catlin Seaview Survey Coral reef organizations Sponge reef – Reefs produced by sea sponges Pseudo-atoll – Island that encircles a lagoon == References == == Further references == Coral Reef Protection: What Are Coral Reefs?. US EPA. UNEP. 2004. Coral Reefs in the South China Sea. UNEP/GEF/SCS Technical Publication No. 2. UNEP. 2007. Coral Reefs Demonstration Sites in the South China Sea. UNEP/GEF/SCS Technical Publication No. 5. UNEP, 2007. National Reports on Coral Reefs in the Coastal Waters of the South China Sea. UNEP/GEF/SCS Technical Publication No. 11. == External links == "Coral Reef Factsheet". Waitt Institute. Archived from the original on 9 June 2015. Retrieved 8 June 2015. Corals and Coral Reefs overview at the Smithsonian Ocean Portal About Corals Archived 26 December 2013 at the Wayback Machine Australian Institute of Marine Science. International Coral Reef Initiative Moorea Coral Reef Long Term Ecological Research Site (US


id: cyclic-steps-20260505-0
file: data/en.wikipedia.org/wiki/Cyclic_steps-0.md
category: reference
title: Cyclic steps
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cyclic_steps
date_saved: 2026-05-05T07:34:42.484931+00:00
instance: kb-cron
parent: cyclic-steps-20260505-0
summary:
Cyclic steps are rhythmic bedforms associated with Froude super-critical flow instability. They are a type of sediment wave, and are created when supercritical sediment-laden water (turbidity currents) travels downslope through sediment beds. Each "step" has a steep drop, and together they tend to migrate upstream. On the ocean floor, this phenomenon was first shown to be possible in 2006, although it was observed in open-channel flows over a decade earlier. Geological features appearing to be submarine cyclic steps have been detected in the northern lowlands of Mars in the Aeolis Mensae region, providing evidence of an ancient Martian ocean. == Formation == There are many parameters which govern the formation of cyclic steps: bed slope, bed porosity, erosion resistance, sediment concentration, and flow rate all play a role. Tilting flumes can be used to create cyclic steps in subaerial laboratory conditions, provided the Froude number is high enough. If the Froude number is lower than required, then antidunes will form instead. Additionally, if the sediment is too fine, then chute-and-pool features will form. In subaqueous conditions, most of the work has traditionally been in building mathematical, rather than physical, models of cyclic step formation. However, cyclic steps have attracted increasing


id: dark-oxygen-20260505-0
file: data/en.wikipedia.org/wiki/Dark_oxygen-0.md
category: reference
title: Dark oxygen
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dark_oxygen
date_saved: 2026-05-05T07:34:43.702448+00:00
instance: kb-cron
parent: dark-oxygen-20260505-0
summary:
Dark oxygen production refers to the generation of molecular oxygen (O2) through processes that do not involve light-dependent oxygenic photosynthesis. The name therefore uses a different sense of 'dark' than that used in the phrase "biological dark matter" (for example) which indicates obscurity to scientific assessment rather than the photometric meaning. While the majority of Earth's oxygen is produced by plants and photosynthetically active microorganisms via photosynthesis, dark oxygen production occurs via a variety of abiotic and biotic processes and may support aerobic metabolism in dark, anoxic environments. The theory for dark oxygen production by manganese nodules on the abyssal seafloor is controversial, with scientists disagreeing about its validity. == Abiotic production == Abiotic production of dark oxygen can occur through several mechanisms, such as: Water radiolysis: This process typically takes place in dark geological ecosystems, such as aquifers, where the decay of radioactive elements in surrounding rock leads to the breakdown of water molecules, producing O2. Oxidation of surface-bound radicals: On silicon-bearing minerals like quartz, surface-bound radicals can undergo oxidation, contributing to O2 production. In addition to direct O2 formation, these processes often produce reactive oxygen species (ROS), such as hydroxyl radicals (OH•), superoxide (O2•-), and hydrogen peroxide (H2O2).


id: dead-zone-ecology-20260505-0
file: data/en.wikipedia.org/wiki/Dead_zone_(ecology)-0.md
category: reference
title: Dead zone (ecology)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dead_zone_(ecology)
date_saved: 2026-05-05T07:34:44.955451+00:00
instance: kb-cron
parent: dead-zone-ecology-20260505-0
summary:
Dead zones are hypoxic (low-oxygen) areas in the world's oceans and large lakes. Hypoxia occurs when dissolved oxygen (DO) concentration falls to or below 2 mg of O2/liter. When a body of water experiences hypoxic conditions, aquatic flora and fauna begin to change behavior in order to reach sections of water with higher oxygen levels. Once DO declines below 0.5 mg O2/liter in a body of water, mass mortality occurs. With such a low concentration of DO, these bodies of water fail to support the aquatic life living there. Historically, many of these sites were naturally occurring. However, in the 1970s, oceanographers began noting increased instances and expanses of dead zones. These occur near inhabited coastlines, where aquatic life is most concentrated. Coastal regions, such as the Baltic Sea, the northern Gulf of Mexico, and the Chesapeake Bay, as well as large enclosed water bodies like Lake Erie, have been affected by deoxygenation due to eutrophication. Excess nutrients are put into these systems by rivers, ultimately from urban and agricultural runoff and exacerbated by deforestation. These nutrients lead to high productivity that produces organic material that sinks to the bottom and is respired. The respiration of that organic material uses


id: dead-zone-ecology-20260505-1
file: data/en.wikipedia.org/wiki/Dead_zone_(ecology)-1.md
category: reference
title: Dead zone (ecology)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dead_zone_(ecology)
date_saved: 2026-05-05T07:34:44.955451+00:00
instance: kb-cron
parent: dead-zone-ecology-20260505-0
summary:
Limnologist David Schindler, whose research at the Experimental Lakes Area led to the banning of harmful phosphates in detergents, warned about algal blooms and dead zones, "The fish-killing blooms that devastated the Great Lakes in the 1960s and 1970s haven't gone away; they've moved west into an arid world in which people, industry, and agriculture are increasingly taxing the quality of what little freshwater there is to be had here....This isn't just a prairie problem. Global expansion of dead zones caused by algal blooms is rising rapidly." The major groups of algae are cyanobacteria, green algae, dinoflagellates, coccolithophores and diatom algae. An increase in the input of nitrogen and phosphorus generally causes cyanobacteria to bloom. Other algae are consumed and thus do not accumulate to the same extent as cyanobacteria. Cyanobacteria are not good food for zooplankton and fish and hence accumulate in water, die, and then decompose. The bacterial degradation of their biomass consumes the oxygen in the water, thereby creating the state of hypoxia. Dead zones can be caused by natural and by anthropogenic factors. Natural causes include coastal upwelling, changes in wind, and water circulation patterns. Other environmental factors that determine the occurrence or intensity of a


id: dead-zone-ecology-20260505-2
file: data/en.wikipedia.org/wiki/Dead_zone_(ecology)-2.md
category: reference
title: Dead zone (ecology)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dead_zone_(ecology)
date_saved: 2026-05-05T07:34:44.955451+00:00
instance: kb-cron
parent: dead-zone-ecology-20260505-0
summary:
The most notable effects of eutrophication are vegetal blooms, sometimes toxic, loss of biodiversity and anoxia, which can lead to the massive death of aquatic organisms. Due to the hypoxic conditions present in dead zones, marine life within these areas tends to be scarce. Most fish and motile organisms tend to emigrate out of the zone as oxygen concentrations fall, and benthic populations may experience severe losses when oxygen concentrations are below 0.5 mg l−1 O2. In severe anoxic conditions, microbial life may experience dramatic shifts in community identity as well, resulting in an increased abundance of anaerobic organisms as aerobic microbes decrease in number and switch energy sources for oxidation such as nitrate, sulfate, or iron reduction. Sulfur reduction is a particular concern as hydrogen sulfide is toxic and stresses most organisms within the zone further, exacerbating mortality risks. Low oxygen levels can have severe effects on survivability of organisms inside the area while above lethal anoxic conditions. Studies conducted along the Gulf Coast of North America have shown hypoxic conditions lead to reduction of reproductive rates and growth rates in a variety of organisms including fish and benthic invertebrates. Organisms able to leave the area typically do so


id: dead-zone-ecology-20260505-3
file: data/en.wikipedia.org/wiki/Dead_zone_(ecology)-3.md
category: reference
title: Dead zone (ecology)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dead_zone_(ecology)
date_saved: 2026-05-05T07:34:44.955451+00:00
instance: kb-cron
parent: dead-zone-ecology-20260505-0
summary:
=== Jellyfish blooms === Despite most other life forms being killed by the lack of oxygen, jellyfish can thrive and are sometimes present in dead zones in vast numbers. Jellyfish blooms produce large quantities of mucus, leading to major changes in food webs in the ocean since few organisms feed on them. The organic carbon in mucus is metabolized by bacteria which return it to the atmosphere in the form of carbon dioxide in what has been termed a "jelly carbon shunt". The potential worsening of jellyfish blooms as a result of human activities has driven new research into the influence of dead zones on jelly populations. The primary concern is the potential for dead zones to serve as breeding grounds for jelly populations as a result of the hypoxic conditions driving away competition for resources and common predators of jellyfish. The increased population of jellyfish could have high commercial costs with loss of fisheries, destruction and contamination of trawling nets and fishing vessels, and lowered tourism revenue in coastal systems. === Seagrass beds === Globally, seagrass has been declining rapidly. It is estimated that 21% of the 71 known seagrass species have decreasing population trends and 11% of those


id: dead-zone-ecology-20260505-4
file: data/en.wikipedia.org/wiki/Dead_zone_(ecology)-4.md
category: reference
title: Dead zone (ecology)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dead_zone_(ecology)
date_saved: 2026-05-05T07:34:44.955451+00:00
instance: kb-cron
parent: dead-zone-ecology-20260505-0
summary:
Researchers from Baltic Nest Institute published in one of PNAS issues reports that the dead zones in the Baltic Sea have grown from approximately 5,000 km2 to more than 60,000 km2 in recent years. Some of the causes behind the elevated increase of dead zones can be attributed to the use of fertilizers, large animal farms, the burning of fossil fuels, and effluents from municipal wastewater treatment plants. With its massive size, the Baltic Sea is best analyzed in sub-areas rather than as a whole. In a paper published in 2004, researchers specifically divided the Baltic Sea into 9 sub-areas, each having its own specific characteristics. The 9 sub-areas are discerned as follows: Gulf of Bothnia, Archipelago region, Gulf of Finland, Gulf of Riga, Gulf of Gdansk, Swedish East-coast, Central Baltic, Belt Sea region, and Kattegat. Each sub-area has responded differently to nutrient additions and eutrophication; however, there are a few general patterns and measures for the Baltic Sea as a whole. As the researchers Rönnberg and Bonsdorff state, "Irrespective of the area-specific effects of the increased loads of nutrients to the Baltic Sea, the sources are more or less similar in the whole region. The extent and the severity


id: dead-zone-ecology-20260505-5
file: data/en.wikipedia.org/wiki/Dead_zone_(ecology)-5.md
category: reference
title: Dead zone (ecology)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dead_zone_(ecology)
date_saved: 2026-05-05T07:34:44.955451+00:00
instance: kb-cron
parent: dead-zone-ecology-20260505-0
summary:
=== Lower St. Lawrence Estuary === A dead zone exists in the Lower St. Lawrence River area from east the Saguenay River to east of Baie Comeau, greatest at depths over 275 metres (902 ft) and noticed since the 1930s. The main concern for Canadian scientists is the impact on fish found in the area. === Oregon === There is a hypoxic zone covering the coasts of Oregon and Washington that reached peak size in 2006 at an area of over 1,158 square miles. Strong surface winds between April and September cause frequent upwelling that results in an increase of algae blooms, rendering the hypoxia a seasonal occurrence. The upwelling has contributed to lower temperatures within the zone. The dead zone has resulted in sea organisms such as crabs and fish relocating and an interference with commercial fishing. Organisms that cannot relocate have been found to suffocate, leaving them useless for fishermen. In 2009, one scientist described "thousands and thousands" of suffocated, crabs, worms, and sea stars along the seafloor of the hypoxic zone. In 2021, 1.9 million dollars were put into monitoring and continuing to study the hypoxic conditions in the area that the dead zone occurs in. ===


id: dead-zone-ecology-20260505-6
file: data/en.wikipedia.org/wiki/Dead_zone_(ecology)-6.md
category: reference
title: Dead zone (ecology)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dead_zone_(ecology)
date_saved: 2026-05-05T07:34:44.955451+00:00
instance: kb-cron
parent: dead-zone-ecology-20260505-0
summary:
==== Economic impact ==== Some assert that the dead zone threatens lucrative commercial and recreational fisheries in the Gulf of Mexico. "In 2009, the dockside value of commercial fisheries in the Gulf was $629 million. Nearly three million recreational fishers further contributed about $10 billion to the Gulf economy, taking 22 million fishing trips." The seafood production is not only hurting states located on the Gulf of Mexico but the U.S. as a whole. It is reported that the Gulf of Mexico dead zone is costing the U.S. seafood and tourism industries about $82 million a year. Louisiana is ranked second in seafood production behind Alaska, and this impact can be devastating for the nations seafood production since the Gulf of Mexico sources 40% of the nations seafood. Scientists are not in universal agreement that nutrient loading has a negative impact on fisheries. Grimes makes a case that nutrient loading enhances the fisheries in the Gulf of Mexico. Courtney et al. hypothesize that nutrient loading may have contributed to the increases in red snapper in the northern and western Gulf of Mexico. In 2017, Tulane University offered a $1 million challenge grant for growing crops with less fertilizer. ==== History


id: dead-zone-ecology-20260505-7
file: data/en.wikipedia.org/wiki/Dead_zone_(ecology)-7.md
category: reference
title: Dead zone (ecology)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dead_zone_(ecology)
date_saved: 2026-05-05T07:34:44.955451+00:00
instance: kb-cron
parent: dead-zone-ecology-20260505-0
summary:
== Prediction and Use of AI for Dead Zones == Dead zones are hard to predict since they use multiple environmental factors. They use nutrient runoff, rainfall, water temperature, and dissolved oxygen levels. Due to this, traditional modeling uses field sampling and satellite observations in order to see major changes. Though this does not measure rapid change, it won't be able to see complete coverage of major areas. Due to this issue, there has been research using artificial intelligence (AI) and machine learning models to increase prediction accuracy and areas that are at risk. This can help see what areas risk of hypoxia before it develops. AI can examine large environmental databases to recognize patters associated with dead zone formations. Machine learning algorithms process information like nitrogen and phosphorus concentrations, precipitation rates, and more, to estimate where low oxygen conditions occur and when. These systems come in handy when monitoring data are incomplete or unavailable allowing researchers to estimate missing data and improve prediction rates. Researchers at Louisiana state University have developed AI-based tools to predict nutrient pollution in watersheds connected to Gulf of Mexico. These tools use machine learning to estimate nutrient runoff from rivers and agriculture land. This


id: dead-zone-ecology-20260505-8
file: data/en.wikipedia.org/wiki/Dead_zone_(ecology)-8.md
category: reference
title: Dead zone (ecology)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dead_zone_(ecology)
date_saved: 2026-05-05T07:34:44.955451+00:00
instance: kb-cron
parent: dead-zone-ecology-20260505-0
summary:
== Biotechnology Application == There are some options that can aid in the reversal process of a dead zone and eventual recovery of water quality and benthic communities through applied biotechnology methodology if a given management project can apply it if the conditions of a dead-zone fit within the criteria. One of the more natural options is established filter feeding species within a marine community that are nearby a impacted ecological area transitioned into a dead zone that can then spread and possibly establish a population there in which recovery time can vary as they filter out access nitrogen and phosphorus. Given that many filter feeding species have different tolerance levels due to the extreme hypoxic conditions, it can be determined through research of how various species respond behaviorally to those specific conditions and deduce the most appropriate species based on a dead-zone of interest to recover. An 8-day study was done on eastern oysters (Crassostrea virginica) and soft-shell clams (Mya arenaria) to assess their reactions to hypoxic and heatwave conditions. While this study was meant for establishing an understanding of behavioral patterns in warming conditions for filter-feeding species, this type of approach can be conducted on other filter-feeding species


id: dead-zone-ecology-20260505-9
file: data/en.wikipedia.org/wiki/Dead_zone_(ecology)-9.md
category: reference
title: Dead zone (ecology)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dead_zone_(ecology)
date_saved: 2026-05-05T07:34:44.955451+00:00
instance: kb-cron
parent: dead-zone-ecology-20260505-0
summary:
== Further reading == Growing 'dead zone' Confirmed by Underwater Robots in the Gulf of Oman, phys.org, April 2018 Hendy, Ian (August 2017), Gulf of Mexico 'dead zone' is already a disaster – but it could get worse, The Conversation Bryant, Lee (April 2015), Ocean 'dead zones' are spreading – and that spells disaster for fish, The Conversation Deprecated link at archive.today (archived January 29, 2013) Suzie Greenhalgh and Amanda Sauer (WRI), "Awakening the 'Dead Zone': An investment for agriculture, water quality, and climate change" 2003 Reyes Tirado (July 2008) Dead Zones: How Agricultural Fertilizers are Killing our Rivers, Lakes and Oceans. Greenpeace publications. See also: "Dead Zones: How Agricultural Fertilizers are Killing our Rivers, Lakes and Oceans". Greenpeace Canada. July 7, 2008. Archived from the original on September 8, 2010. Retrieved August 3, 2010. MSNBC report on dead zones, March 29, 2004 Joel Achenbach, "A 'Dead Zone' in The Gulf of Mexico: Scientists Say Area That Cannot Support Some Marine Life Is Near Record Size", The Washington Post, July 31, 2008 Joel Achenbach, "'Dead Zones' Appear In Waters Worldwide: New Study Estimates More Than 400", The Washington Post, August 15, 2008 == External links == Louisiana Universities Marine Consortium


id: deep-sea-20260505-0
file: data/en.wikipedia.org/wiki/Deep_sea-0.md
category: reference
title: Deep sea
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Deep_sea
date_saved: 2026-05-05T07:34:46.246452+00:00
instance: kb-cron
parent: deep-sea-20260505-0
summary:
The deep sea is broadly defined as the ocean depth where light begins to fade, at an approximate depth of 200 m (660 ft) or the point of transition from continental shelves to continental slopes. Conditions within the deep sea are a combination of low temperatures, darkness, and high pressure. The deep sea is considered the least explored Earth biome as the extreme conditions make the environment difficult to access and explore. Organisms living within the deep sea have a variety of adaptations to survive in these conditions. Organisms can survive in the deep sea through a number of feeding methods including scavenging, predation and filtration, with a number of organisms surviving by feeding on marine snow. Marine snow is organic material that has fallen from upper waters into the deep sea. In 1960, the bathyscaphe Trieste descended to the bottom of the Mariana Trench near Guam, at 10,911 m (35,797 ft; 6.780 mi), the deepest known spot in any ocean. If Mount Everest (8,848 m or 29,029 ft or 5.498 mi) were submerged there, its peak would be more than 2 km (1.2 mi) beneath the surface. After the Trieste was retired, the Japanese remote-operated vehicle (ROV) Kaikō was


id: deep-sea-20260505-1
file: data/en.wikipedia.org/wiki/Deep_sea-1.md
category: reference
title: Deep sea
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Deep_sea
date_saved: 2026-05-05T07:34:46.246452+00:00
instance: kb-cron
parent: deep-sea-20260505-0
summary:
Regions below the epipelagic are divided into further zones, beginning with the bathyal zone (also considered the continental slope) which spans from 200 to 3,000 meters (660 to 9,840 ft) below sea level and is essentially transitional, containing elements from both the shelf above and the abyss below. Below this zone, the deep sea consists of the abyssal zone (ocean depth between 3–6 km; 1.9–3.7 mi) and the hadal zone (6–11 km; 3.7–6.8 mi). Food consists of falling organic matter known as 'marine snow' and carcasses derived from the productive zone above, and is scarce both in terms of spatial and temporal distribution. Instead of relying on gas for their buoyancy, many deep-sea species have jelly-like flesh consisting mostly of glycosaminoglycans, which provides them with very low density. It is also common among deep water squid to combine the gelatinous tissue with a flotation chamber filled with a coelomic fluid made up of the metabolic waste product ammonium chloride, which is lighter than the surrounding water. The midwater fish have special adaptations to cope with these conditions—they are small, usually being under 25 centimetres (10 in); they have slow metabolisms and unspecialized diets, preferring to sit and wait for food


id: deep-sea-20260505-2
file: data/en.wikipedia.org/wiki/Deep_sea-2.md
category: reference
title: Deep sea
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Deep_sea
date_saved: 2026-05-05T07:34:46.246452+00:00
instance: kb-cron
parent: deep-sea-20260505-0
summary:
=== Adaptation to hydrostatic pressure === Deep-sea fish have different adaptations in their proteins, anatomical structures, and metabolic systems to survive in the Deep sea, where the inhabitants have to withstand great amount of hydrostatic pressure. While other factors like food availability and predator avoidance are important, the deep-sea organisms must have the ability to maintain well-regulated metabolic system in the face of high pressures. In order to adjust for the extreme environment, these organisms have developed unique characteristics. Proteins are affected greatly by the elevated hydrostatic pressure, as they undergo changes in water organization during hydration and dehydration reactions of the binding events. This is due to the fact that most enzyme-ligand interactions form through charged or polar non-charge interactions. Because hydrostatic pressure affects both protein folding and assembly and enzymatic activity, the deep sea species must undergo physiological and structural adaptations to preserve protein functionality against pressure. Actin is a protein that is essential for different cellular functions. The α-actin serves as a main component for muscle fiber, and it is highly conserved across numerous different species. Some Deep-sea fish developed pressure tolerance through the change in mechanism of their α-actin. In some species that live in depths


id: deep-sea-fish-20260505-0
file: data/en.wikipedia.org/wiki/Deep-sea_fish-0.md
category: reference
title: Deep-sea fish
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Deep-sea_fish
date_saved: 2026-05-05T07:34:47.616452+00:00
instance: kb-cron
parent: deep-sea-fish-20260505-0
summary:
Deep-sea fish are fish that live in the darkness below the sunlit surface waters, that is below the epipelagic or photic zone of the sea. The lanternfish is, by far, the most common deep-sea fish. Other deep-sea fishes include the flashlight fish, cookiecutter shark, bristlemouths, anglerfish, viperfish, and some species of eelpout. Only about 2% of known marine species inhabit the pelagic environment. This means that they live in the water column as opposed to the benthic organisms that live in or on the sea floor. Deep-sea organisms generally inhabit bathypelagic (1–4 km; 0.62–2.49 mi deep) and abyssopelagic (4–6 km; 2.5–3.7 mi deep) zones. However, characteristics of deep-sea organisms, such as bioluminescence can be seen in the mesopelagic (200–1,000 m; 660–3,280 ft deep) zone as well. The mesopelagic zone is the disphotic zone, meaning light there is minimal but still measurable. The oxygen minimum layer exists somewhere between a depth of 700 and 1,000 metres (2,300 and 3,300 ft) depending on the place in the ocean. This area is also where nutrients are most abundant. The bathypelagic and abyssopelagic zones are aphotic, meaning that no light penetrates this area of the ocean. These zones make up about 75% of the


id: deep-sea-fish-20260505-1
file: data/en.wikipedia.org/wiki/Deep-sea_fish-1.md
category: reference
title: Deep-sea fish
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Deep-sea_fish
date_saved: 2026-05-05T07:34:47.616452+00:00
instance: kb-cron
parent: deep-sea-fish-20260505-0
summary:
In the deep ocean, the waters extend far below the epipelagic zone, and support very different types of pelagic fishes adapted to living in these deeper zones. In deep water, marine snow is a continuous shower of mostly organic detritus falling from the upper layers of the water column. Its origin lies in activities within the productive photic zone. Marine snow includes dead or dying plankton, protists (diatoms), fecal matter, sand, soot and other inorganic dust. The "snowflakes" grow over time and may reach several centimetres in diameter, travelling for weeks before reaching the ocean floor. However, most organic components of marine snow are consumed by microbes, zooplankton and other filter-feeding animals within the first 1,000 metres (3,300 ft) of their journey, that is, within the epipelagic zone. In this way, marine snow may be considered the foundation of deep-sea mesopelagic and benthic ecosystems: as sunlight cannot reach them, deep-sea organisms rely heavily on marine snow as an energy source. Since there is no light in the deep sea (aphotic), there is a lack of primary producers. Therefore, most organisms in the bathypelagic rely on the marine snow from regions higher in the vertical column. Some deep-sea pelagic groups, such


id: deep-sea-fish-20260505-2
file: data/en.wikipedia.org/wiki/Deep-sea_fish-2.md
category: reference
title: Deep-sea fish
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Deep-sea_fish
date_saved: 2026-05-05T07:34:47.616452+00:00
instance: kb-cron
parent: deep-sea-fish-20260505-0
summary:
The fish of the deep-sea have evolved various adaptations to survive in this region. Since many of these fish live in regions where there is no natural illumination, they cannot rely solely on their eyesight for locating prey and mates and avoiding predators; deep-sea fish have evolved appropriately to the extreme sub-photic region in which they live. Many of these organisms are blind and rely on their other senses, such as sensitivities to changes in local pressure and smell, to catch their food and avoid being caught. Those that aren't blind have large and sensitive eyes that can use bioluminescent light. These eyes can be as much as 100 times more sensitive to light than human eyes. Rhodopsin (Rh1) is a protein found in the eye's rod cells that helps animals see in dim light. While most vertebrates usually have one Rh1 opsin gene, some deep-sea fish have several Rh1 genes, and one species, the silver spinyfin (Diretmus argenteus), has 38. This proliferation of Rh1 genes may help deep-sea fish to see in the depths of the ocean. Also, to avoid predation, many species are dark to blend in with their environment. Many deep-sea fish are bioluminescent, with extremely large


id: deep-sea-fish-20260505-3
file: data/en.wikipedia.org/wiki/Deep-sea_fish-3.md
category: reference
title: Deep-sea fish
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Deep-sea_fish
date_saved: 2026-05-05T07:34:47.616452+00:00
instance: kb-cron
parent: deep-sea-fish-20260505-0
summary:
Below the epipelagic zone, conditions change rapidly. Between 200 m and about 1000 m, light continues to fade until there is almost none. Temperatures fall through a thermocline to temperatures between 3.9 and 7.8 °C (39.0 and 46.0 °F). This is the twilight or mesopelagic zone. Pressure continues to increase, at the rate of one atm (0.1 MPa) every 10 m (33 ft), while nutrient concentrations fall, along with dissolved oxygen and the rate at which the water circulates. Sonar operators, using the newly developed sonar technology during World War II, were puzzled by what appeared to be a false sea floor 300–500 metres (984–1,640 ft) deep by day, and less deep at night. This turned out to be due to millions of marine organisms, most particularly small mesopelagic fish, with swim bladders that reflected the sonar. These organisms migrate up into shallower water at dusk to feed on plankton. The layer is deeper when the moon is out, and can become shallower when clouds pass over the moon. This phenomenon has come to be known as the deep scattering layer. Most mesopelagic fish make daily vertical migrations, moving at night into the epipelagic zone, often following similar migrations of


id: deep-sea-fish-20260505-4
file: data/en.wikipedia.org/wiki/Deep-sea_fish-4.md
category: reference
title: Deep-sea fish
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Deep-sea_fish
date_saved: 2026-05-05T07:34:47.616452+00:00
instance: kb-cron
parent: deep-sea-fish-20260505-0
summary:
Below the mesopelagic zone it is pitch dark. This is the midnight (or bathypelagic zone), extending from 1,000 metres (3,281 ft) to the bottom deep-water benthic zone. If the water is exceptionally deep, the pelagic zone below 4,000 metres (13,123 ft) is sometimes called the lower midnight (or abyssopelagic zone). Temperatures in this zone range from 1 to 4 °C (34 to 39 °F) and it is completely aphotic. Conditions are somewhat uniform throughout these zones; the darkness is complete, the pressure is crushing, and temperatures, nutrients and dissolved oxygen levels are all low. Bathypelagic fish have special adaptations to cope with these conditions – they have slow metabolisms and unspecialized diets, being willing to eat anything that comes along. They prefer to sit and wait for food rather than waste energy searching for it. The behaviour of bathypelagic fish can be contrasted with the behaviour of mesopelagic fish. Mesopelagic fish are often highly mobile, whereas bathypelagic fish are almost all lie-in-wait predators, normally expending little energy in movement. The dominant bathypelagic fishes are small bristlemouth and anglerfish; fangtooth, viperfish, daggertooth and barracudina are also common. These fishes are small, many about 10 centimetres (3.9 in) long, and not many


id: deep-sea-fish-20260505-5
file: data/en.wikipedia.org/wiki/Deep-sea_fish-5.md
category: reference
title: Deep-sea fish
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Deep-sea_fish
date_saved: 2026-05-05T07:34:47.616452+00:00
instance: kb-cron
parent: deep-sea-fish-20260505-0
summary:
== Adaptation to high pressure == As a fish moves deeper into the sea, the weight of the water overhead exerts increasing hydrostatic pressure on the fish. This increased pressure amounts to about one atm (0.1 MPa) for every 10 m (33 ft)in depth. For a fish at the bottom of the bathypelagic zone, this pressure amounts to about 400 atm (40 MPa, 6000 psi). Deep-sea organisms possess adaptations at cellular and physiological levels that allow them to survive in environments of great pressure. Not having these adaptations limits the depths at which shallow-water species can operate. High levels of external pressure affects how metabolic processes and biochemical reactions proceed. The equilibrium of many chemical reactions is disturbed by pressure, and pressure can inhibit processes which result in an increase in volume. Water, a key component in many biological processes, is very susceptible to volume changes, mainly because constituents of cellular fluid have an effect on water structure. Thus, enzymatic reactions that induce changes in water organization effectively change the system's volume. Proteins responsible for catalyzing reactions are typically held together by weak bonds and the reactions usually involve volume increases. Species that can tolerate these depths have evolved changes


id: deep-ocean-water-20260505-0
file: data/en.wikipedia.org/wiki/Deep_ocean_water-0.md
category: reference
title: Deep ocean water
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Deep_ocean_water
date_saved: 2026-05-05T07:34:48.870613+00:00
instance: kb-cron
parent: deep-ocean-water-20260505-0
summary:
Deep ocean water (DOW) is the name for cold, salty water found in the deep sea, starting at 200 m (660 ft) below the surface of Earth's oceans. Ocean water differs in temperature and salinity. Warm surface water is generally saltier than the cooler deep or polar waters; in polar regions, the upper layers of ocean water are cold and fresh. Deep ocean water makes up about 90% of the volume of the oceans. Deep ocean water has a very uniform temperature, around 0–3 °C (32–37 °F), and a salinity of about 3.5% or, as oceanographers state, 35‰ (parts per thousand). In specialized locations, such as the Natural Energy Laboratory of Hawaii, ocean water is pumped to the surface from approximately 900 m (3,000 ft) deep for applications in research, commercial and pre-commercial activities. DOW is typically used to describe ocean water at sub-thermal depths sufficient to provide a measurable difference in water temperature. == Cold-bed agriculture == A potential indirect use of cold ocean water is "cold-bed agriculture". During condensation or ocean thermal energy conversion operations, the water does not reach ambient temperature, because a certain temperature gradient is required to make these processes viable. The water leaving those


id: deep-sea-wood-20260505-0
file: data/en.wikipedia.org/wiki/Deep-sea_wood-0.md
category: reference
title: Deep-sea wood
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Deep-sea_wood
date_saved: 2026-05-05T07:34:50.198701+00:00
instance: kb-cron
parent: deep-sea-wood-20260505-0
summary:
Deep-sea wood is the term for wood which sinks to the ocean floor. These wood-falls develop deep sea ecosystems. Deep-sea wood supports unique forms of deep sea community life including chemo-synthetic bacteria. Sources of carbon for these deep sea ecosystems are not limited to sunken wood, but also include kelp and the remains of whales. Much of what is known about deep-sea wood is obtained from experiments by marine biologists, in which wood is forced to the bottom of the ocean for a set amount of time and is then collected later for sampling. == Organisms present == === Wood boring bivalves === Colonization experiments revealed the presence of wood boring bivalves that belong to the subfamily Xylophagainae, such as Xylophaga dorsalis, or other species recently described from deep-sea canyons. They range in shell size from 1 to 10 mm (0.04 to 0.4 in). These bivalves are able to digest wood with the help of symbiotic bacteria in their gills. === Chemosyntheic fauna === Chemosyntheic mussels identified as Idas modiolaeformis were also found in deep sea wood when organic matter settled for at least one year. They are slightly smaller than the bivalves found and range in length from 1


id: demersal-zone-20260505-0
file: data/en.wikipedia.org/wiki/Demersal_zone-0.md
category: reference
title: Demersal zone
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Demersal_zone
date_saved: 2026-05-05T07:34:51.436336+00:00
instance: kb-cron
parent: demersal-zone-20260505-0
summary:
The demersal zone (from Latin demergere, "to sink") is the part of the sea or ocean (or deep lake) consisting of the part of the water column near to (and significantly affected by) the seabed and the benthos. The demersal zone is just above the benthic zone and forms a layer of the larger profundal zone. Being just above the ocean floor, the demersal zone is variable in depth and can be part of the photic zone where light can penetrate, and photosynthetic organisms grow, or the aphotic zone, which begins between depths of roughly 200 and 1,000 m (700 and 3,300 ft) and extends to the ocean depths, where no light penetrates. == Fish == The distinction between demersal species of fish and pelagic species is not always clear cut. The Atlantic cod (Gadus morhua) is a typical demersal fish, but can also be found in the open water column, and the Atlantic herring (Clupea harengus) is predominantly a pelagic species but forms large aggregations near the seabed when it spawns on banks of gravel. Two types of fish inhabit the demersal zone: those that are heavier than water and rest on the seabed, and those that have neutral


id: fracture-zone-20260505-0
file: data/en.wikipedia.org/wiki/Fracture_zone-0.md
category: reference
title: Fracture zone
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fracture_zone
date_saved: 2026-05-05T07:34:52.674187+00:00
instance: kb-cron
parent: fracture-zone-20260505-0
summary:
A fracture zone is a linear feature on the ocean floor—often hundreds, even thousands of kilometers long—resulting from the action of offset mid-ocean ridge axis segments. They are a consequence of plate tectonics. Lithospheric plates on either side of an active transform fault move in opposite directions; here, strike-slip activity occurs. Fracture zones extend past the transform faults, away from the ridge axis; are usually seismically inactive (because both plate segments are moving in the same direction), although they can display evidence of transform fault activity, primarily in the different ages of the crust on opposite sides of the zone. In actual usage, many transform faults aligned with fracture zones are often loosely referred to as "fracture zones" although technically, they are not. They can be associated with other tectonic features and may be subducted or distorted by later tectonic activity. They are usually defined with bathymetric, gravity and magnetic studies. == Structure and formation == Mid-ocean ridges are divergent plate boundaries. As the plates on either side of an offset mid-ocean ridge move, a transform fault forms at the offset between the two ridges. Fracture zones and the transform faults that form them are separate but related features. Transform


id: gas-hydrate-stability-zone-20260505-0
file: data/en.wikipedia.org/wiki/Gas_hydrate_stability_zone-0.md
category: reference
title: Gas hydrate stability zone
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Gas_hydrate_stability_zone
date_saved: 2026-05-05T07:34:53.961204+00:00
instance: kb-cron
parent: gas-hydrate-stability-zone-20260505-0
summary:
Gas hydrate stability zone, abbreviated GHSZ, also referred to as methane hydrate stability zone (MHSZ) or hydrate stability zone (HSZ), refers to a zone and depth of the marine environment at which methane clathrates naturally exist in the Earth's crust. == Description == Gas hydrate stability primarily depends upon temperature and pressure, however other variables such as gas composition and ionic impurities in water influence stability boundaries. The existence and depth of a hydrate deposit is often indicated by the presence of a bottom-simulating reflector (BSR). A BSR is a seismic reflection indicating the lower limit of hydrate stability in sediments due to the different densities of hydrate saturated sediments, normal sediments and those containing free gas. == Limits == The upper and lower limits of the HSZ, as well as its thickness, depend upon the local conditions in which the hydrate occurs. The conditions for hydrate stability generally restrict natural deposits to polar regions and deep oceanic regions. In polar regions, due to low temperatures, the upper limit of the hydrate stability zone occurs at a depth of approximately 150 meters.1 The maximal depth of the hydrate stability zone is limited by the geothermal gradient. Along continental margins the


id: hadal-zone-20260505-0
file: data/en.wikipedia.org/wiki/Hadal_zone-0.md
category: reference
title: Hadal zone
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Hadal_zone
date_saved: 2026-05-05T07:34:56.432817+00:00
instance: kb-cron
parent: hadal-zone-20260505-0
summary:
The hadal zone, also known as the hadopelagic zone, is the deepest region of the ocean, lying within oceanic trenches. The hadal zone ranges from around 6 to 11 km (3.7 to 6.8 mi; 20,000 to 36,000 ft) below sea level, and exists in long, narrow, topographic V-shaped depressions. The total area occupied by the 46 individual hadal habitats worldwide is less than 0.25% of the world's seafloor, yet trenches account for over 40% of the ocean's depth range. Most hadal habitats are found in the Pacific Ocean, the largest and deepest of the conventional oceanic divisions. == Terminology and definition == Historically, the hadal zone was not recognized as distinct from the abyssal zone, although the deepest sections were sometimes called "ultra-abyssal". During the early 1950s, the Danish Galathea II and Soviet Vityaz expeditions separately discovered a distinct shift in the life at depths of 6,000–7,000 m (20,000–23,000 ft) not recognized by the broad definition of the abyssal zone. The term "hadal" was first proposed in 1956 by Anton Frederik Bruun to describe the parts of the ocean deeper than 6,000 m (20,000 ft), leaving abyssal for the parts at 4,000–6,000 m (13,000–20,000 ft). The name refers to Hades,


id: hadal-zone-20260505-1
file: data/en.wikipedia.org/wiki/Hadal_zone-1.md
category: reference
title: Hadal zone
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Hadal_zone
date_saved: 2026-05-05T07:34:56.432817+00:00
instance: kb-cron
parent: hadal-zone-20260505-0
summary:
== Exploration == The exploration of the hadal zone requires the use of instruments that are able to withstand pressures of up to a thousand or more atmospheres. A few haphazard and non-standard tools have been used to collect limited, but valuable, information about the basic biology of a few hadal organisms. Manned and unmanned submersibles, however, can be used to study the depths in greater detail. Unmanned robotic submersibles may be remotely operated (connected to the research vessel by a cable) or autonomous (freely moving). Cameras and manipulators on submersibles allow researchers to observe and take samples of sediment and organisms. Failures of submersibles under the immense pressure at hadal zone depths have occurred. HROV Nereus is thought to have imploded at a depth of 9,990 meters while exploring the Kermadec Trench in 2014. == Notable missions == The first manned exploration to reach Challenger Deep, the deepest known part of the ocean located in the Mariana Trench, was accomplished in 1960 by Jacques Piccard and Don Walsh. They reached a maximum depth of 10,911 metres (35,797 ft) in the bathyscaphe Trieste. James Cameron also reached the bottom of Mariana Trench in March 2012 using the Deepsea Challenger. The


id: haff-lagoon-20260505-0
file: data/en.wikipedia.org/wiki/Haff_(lagoon)-0.md
category: reference
title: Haff (lagoon)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Haff_(lagoon)
date_saved: 2026-05-05T07:34:57.591702+00:00
instance: kb-cron
parent: haff-lagoon-20260505-0
summary:
Haff (German for "lagoon", pronounced [haf] ) or Bodden may refer to several estuarine lagoons along the Southern Baltic coast: Frisches Haff Großes Haff Kamieński Lagoon or Camminer Bodden Kleines Haff Kurisches Haff Stettiner Haff, also Pommersches Haff or Oderhaff In Northern Germany and the Netherlands, the now obsolete Frisian word hef may refer to the Wadden Sea, which has some properties of a lagoon.


id: iceberg-20260505-0
file: data/en.wikipedia.org/wiki/Iceberg-0.md
category: reference
title: Iceberg
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Iceberg
date_saved: 2026-05-05T07:34:58.808748+00:00
instance: kb-cron
parent: iceberg-20260505-0
summary:
An iceberg is a piece of fresh water ice more than 15 meters (16 yards) long that has broken off a glacier or an ice shelf and is floating freely in open water. Smaller chunks of floating glacially derived ice are called "growlers" or "bergy bits". Much of an iceberg is below the water's surface, which led to the expression "tip of the iceberg" to illustrate a small part of a larger unseen issue. Icebergs are considered a serious maritime hazard. Icebergs vary considerably in size and shape. Icebergs that calve from glaciers in Greenland are often irregularly shaped while Antarctic ice shelves often produce large tabular (table top) icebergs. The largest iceberg in recent history, named B-15, was measured at nearly 300 by 40 kilometres (186 by 25 mi) in 2000. The largest iceberg on record was an Antarctic tabular iceberg measuring 335 by 97 kilometres (208 by 60 mi) sighted 240 kilometres (150 mi) west of Scott Island, in the South Pacific Ocean, by the USS Glacier on November 12, 1956. This iceberg was larger than Belgium. == Etymology == The word iceberg is a partial loan translation from the Dutch word ijsberg, literally meaning ice mountain, cognate


id: iceberg-20260505-1
file: data/en.wikipedia.org/wiki/Iceberg-1.md
category: reference
title: Iceberg
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Iceberg
date_saved: 2026-05-05T07:34:58.808748+00:00
instance: kb-cron
parent: iceberg-20260505-0
summary:
=== Stability === An iceberg may flip, or capsize, as it melts and breaks apart, changing the center of gravity. Capsizing can occur shortly after calving when the iceberg is young and establishing balance. Icebergs are unpredictable and can capsize anytime and without warning. Large icebergs that break off from a glacier front and flip onto the glacier face can push the entire glacier backwards momentarily, producing 'glacial earthquakes' that generate as much energy as an atomic bomb. === Color === Icebergs are generally white because they are covered in snow, but can be green, blue, yellow, black, striped, or even rainbow-colored. Seawater, algae and lack of air bubbles in the ice can create diverse colors. Sediment can create the dirty black coloration present in some icebergs. === Shape === In addition to size classification, icebergs can be classified on the basis of their shapes. The two basic types of iceberg forms are tabular and non-tabular. Tabular icebergs have steep sides and a flat top, much like a plateau, with a length-to-height ratio of more than 5:1. This type of iceberg, also known as an ice island, can be quite large, as in the case of Pobeda Ice Island. Antarctic


id: iceberg-20260505-2
file: data/en.wikipedia.org/wiki/Iceberg-2.md
category: reference
title: Iceberg
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Iceberg
date_saved: 2026-05-05T07:34:58.808748+00:00
instance: kb-cron
parent: iceberg-20260505-0
summary:
=== Commercial use === The idea of towing large icebergs to other regions as a source of water has been raised since at least the 1950s, without having been put into practice. In 2017, a business from the UAE announced plans to tow an iceberg from Antarctica to the Middle East; in 2019 salvage engineer Nick Sloane announced a plan to move one to South Africa at an estimated cost of $200 million. In 2019, a German company, Polewater, announced plans to tow Antarctic icebergs to places like South Africa. Companies have used iceberg water in products such as bottled water, fizzy ice cubes and alcoholic drinks. For example, Iceberg Beer by Quidi Vidi Brewing Company is made from icebergs found around St. John's, Newfoundland. Although annual iceberg supply in Newfoundland and Labrador exceeds the total freshwater consumption of the United States, in 2016 the province introduced a tax on iceberg harvesting and imposed a limit on how much fresh water can be exported yearly. == Oceanography and ecology == The freshwater injected into the ocean by melting icebergs can change the density of the seawater in the vicinity of the iceberg. Fresh melt water released at depth is lighter,


