Dead coral fans [edit | edit. Coral Island. The distribution of coral reefs is noise-based, which means that in some places of warm ocean floor, the reefs are distributed densely, and in other places there's no coral reef at all. Coral Reef Fans 瑚礁粉 珊瑚海水魚器材買賣, 香港. The Somosomo Straight, between Taveuni and Vanua Levu islands, is almost single-handedly responsible for the fact that Fiji is known as the soft coral capital of the world. Each Reef Is Different In Size And Shape, And Is Made Up Of Coral Blocks And Coral Fans. It grows no larger than a human fingernail and is often only the size of a pinhead. Sexual reproduction occurs either when sperm and eggs are released in a mass spawning event, or by brooding, when only sperm are released, and these are captured by female polyps with eggs. The evaporation of the seawater provides. Nearly a quarter of all the fish in the sea rely on healthy coral reefs. sponges, and gorgonians—a type of coral that includes sea fans—the team found that. Furthermore, the common mushroom coral will only attach itself to a reef for the early part of its life. It took approximately 5,000 years for this coral reef to form. coral_reef / daddy_aches / daddyaches / daddyyaches instagram. Post-generation [edit | edit source] Bone meal [edit | edit source]. They are mutualism, parasitism, and commensalism. Country. sea fans (gorgonians), and some stony corals. They offer shelter, nursery grounds, and a source of food for more than half a million marine species. More Buying Choices $274. Coral species include the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton. This not only protects marine life. Because of the many species, the Gorgonia can be found in all the seas, particularly in tropical regions. NA subscribers. Carnivore. Dead coral fans are the dead variants of coral fans. Size: Polyp: 0. com/cassies_reef onlyfans. They are found in ocean biomes, and can be harvested with a pickaxe. 130 photos. Only the center purple fan looks relatively healthy in the picture below. Brain corals look like a human brain, with maze-like patterns weaving across their shape. Coral reefs are the most diverse of all marine ecosystems. Breaking coral fans without Silk Touch destroys the coral fan. Bleached corals on a reef at Lisianski Atoll in. Learn about coral reef conservation. g. Most Sea Fans are nocturnal, only extending their polyps during the nighttime hours. – Coral have growth rings, just like trees! – The first coral reefs formed on Earth 240 million years ago. The Great Barrier. 5) Key Largo, FL 33037 / P. This Is A Variation Of The Normal Ocean, With Warmer Waters. The powerful deep sea-currents funnel nutrients into the coral reefs, making Raja Ampat a. coral_reef and kitsune_foreplay have a lot of leaks. These memes poke a bit of fun at it, but are absolutely hilarious. 0:00. It is possible to find coral reefs at depths exceeding 91 m, but reef-building corals generally grow best at depths shallower than 70 m. These corals do not have stony skeletons and are non-reef-building corals—instead, they grow wood-like cores and fleshy rinds for protection. If you see these, there’s a good chance that you’re in or near a coral reef. This teeming backbone of marine life runs the length of the Keys about five miles offshore and offers Florida Keys scuba diving vacation memories that last a lifetime. While the atmosphere of this restaurant is pretty epic (you’re literally dining with the fish), the food isn’t anything great. An estimated 500 million people who live in coastal communities depend. That affects not only marine life that depends on the reefs for survival, but also people — coral reefs are a natural buffer against storm surge from hurricanes and other storms. This reef is within a Sanctuary Preservation Area (SPA). Coral reefs are the most diverse of all marine ecosystems. Subscribe to be the first to know about new content. This continues, producing more polyps and forming a colony. The young will grow in any direction, but as they mature will slowly shift until they are facing. Researchers, activists and government agencies are working to restore the reefs and ensure their long-term survival. Even though coral reefs only cover about 1% of the ocean floor, an estimated 25% of all marine life is dependent on coral reefs at some point in their life. While marine conservation has historically focused on passive habitat protection, demand for and interest in active restoration has been growing in recent decades. Videos. 03. Symbiotic relationships are very common in the ocean, especially near coral reefs. (1) A coral polyp is the single living organism of a coral, and the animal responsible for our coral reefs. The park, located in Key Largo, was established to protect and preserve a portion of Florida’s Coral Reef, the only living coral barrier. Plunging in for a scuba dive, I was spellbound by the vitality of Lady Elliot's fringing reef. Coral fans are non-solid blocks that come in 5 variants: tube, brain, bubble, fire, and horn. hide. Underwater Scuba diver explore and enjoy Coral reef Sea life Scuba diving. Nearly a quarter of all the fish in the sea rely on healthy coral reefs. Furthermore, coral reefs are extremely important for nutrient cycling in shallow. u/Sassyleaf: 21 / 5’9 / 🇯🇵👱🏻♀️ | Chat with me on OF ️ Hydrocorals, or fire coral, are reef-building hydroids that have a hard calcareous exoskeleton and stinging cells that can cause a burning sensation when touched. As mentioned earlier, hard corals build coral reefs. 4: There Are Hundreds of Coral Species of All Colors, Shapes and Sizes. They typically form compact colonies of many identical individual polyps. We can see that Cassie is the only OnlyFans user. Download and use 100+ Coralreef Onlyfans Leak stock photos for free. Dana Dearmond – Best Overall. #1. Only recently, as fishery and oil exploration activities in deeper waters have increased, have developments in acoustic survey techniques and access to submersibles revealed the scale and abundance of cold-water coral ecosystems (1, 2). I love my new VR headset. The most conspicuous mutualistic symbioses on coral reefs are those between: ( a) eukaryotic micro-algae and many invertebrates, including all reef-building corals and some sponges; and ( b) prokaryotic cyanobacteria (=blue-green algae) and/or heterotrophic bacteria, and numerous sponges. Coral belongs to the class Anthozoa in the animal phylum Cnidaria, which includes sea anemones and. Even if you hint you are selling you will be permanently banned with no appeals. Underwater scene with young women, scuba diver, explore and enjoy at coral reef. Eastern Dry Rocks is a coral reef located within the Florida Keys National Marine Sanctuary. A “bleached” coral is a stressed-out coral that, when triggered by environmental changes such as pollution and warming waters, has evicted its beneficial, energy-producing algae. (OnlyFans) Published: 2023-10-11 03:49:56. By Blaine Friedlander. coral_reef OnlyFans Leak. Further, it is estimated that nearly 30 million of the poorest human populations in the world depend entirely on coral. The Blueberry Sea Fan is also referred to as the Blue Gorgonia or Blue Tree coral. Remove bookmark Bookmark Copy link Reportcassies_reef / coral_reef instagram. ”. Coral reefs are among the world’s most beautiful and biodiverse ecosystems, forged by a series of unlikely partnerships between organisms large and small. cassies_reef / coral_reef instagram. For most of its life, the reef was the world’s largest living structure, and the only. Chasing Coral is a tribute to everyone involved. @coral-reef. Then, one by one, they silently slip. The green sea fan is usually more yellow. The tutorial is an overview of the biology of and threats to coral reefs, as well as efforts being made to conserve and protect them. Coral reefs are therefore only found in ocean regions where the water is always above approximately 65 degrees Fahrenheit, or. A buoy in the Florida Bay hit 101. Salty Underground has a large variety of corals for sale online. To get coral blocks or coral fans, players need a Silk Touch enchanted tool. Coral species are diverse, interdependent, and ancient, first appearing 500 million years ago. share. Power point. Florida's barrier reef has lost 95% of its coral over the last half-century. Each reef is different in size and shape, and is made up of coral blocks and coral fans. The largest coral reef in the world, the Great Barrier Reef, off the coast of Australia, is more than 1,250 miles (2,000 kilometers) long. m4v. The Red Sea Fan comes from the deep parts of the reefs of the Indian Ocean and has a classic sea fan appearance. The Indian Ocean accounts for up to 60% of the global coastal reefs, the Pacific Ocean 25%, and the West Atlantic 15%. Some are thought to resemble deer antlers, trees, giant fans, brains, and honeycombs. The disease exhibits a pronounced division between. Plunging in for a scuba dive, I was spellbound by the vitality of Lady Elliot's fringing reef. The Triangle covers around 6 million square kilometres of ocean spanning from central Indonesia in the west, to the Solomon Islands in the east, and north to the Philippines – also including waters off Malaysia, Timor-Leste and Papua New Guinea. Mimicry is also frequently seen amongst coral. They also have sea pickles, which can be seen as the light in the image above. Whether you consider yourself a seasoned diver or casual swimmer, these clips will make you look like a professional scuba instructor. Price: $7 $0 100% OFF. Read current news articles on coral reefs in danger due to coral bleaching. Coral is a class of colonial animal that is related to hydroids, jellyfish, and sea anemones. We offer u8614872 OnlyFans leaked content, you can find list of available content of coral_reef below. Along with its beautiful colors and patterns, the Venus sea fan can. Take in the vibrant colours and exotic fish that make up the captivating coral reefs. These octopuses predominantly inhabit areas with water temperatures around 20-30°C. coral_reef (u8614872) free OnlyFans content View 81 photos and videos. Climate change is the biggest threat to the world’s coral reefs, causing mass bleaching, among other things. @solontwins . There are over 2,500 kinds (species) of corals. 1. Coral reefs support human life and livelihoods and are important economically. Coral reefs also need warm seawater between 68 and 82 degrees Fahrenheit to thrive. Sources: Coulombe, D. OnlyFans is the social platform revolutionizing creator and fan connections. Coral Isle 2 Game Fans. These types of reefs are the most common type we see and are considered to be the youngest of the 3 types of coral reefs. The two types of coral reef structures off south Florida are patch reefs and bank reefs. (more) A coral reef is actually a complex of features, only part of which is. They teem with life, with perhaps one-quarter of all ocean species depending on reefs for food and shelter. Hard corals are primary reef-building corals. There. u8614872 (coral_reef) and alice_n_wooderland are very popular on. Coral reefs are some of the most diverse ecosystems in the world. The most common names used for subsets of soft corals are “ sea fans ” and. The site is inclusive of artists and content creators from all genres and allows them to monetize their content while developing authentic relationships with their fanbase. Coral fans and their dead variants can be mined instantly, but Silk Touch enchanted tools are required to obtain them. Coral reefs are some of the most diverse ecosystems in the world. Habitat and Distribution. OnlyFans is the social platform revolutionizing creator and fan connections. Credit: Pixabay/CC0 Public Domain. FORT LAUDERDALE, Fla. me is the easiest way to search for OnlyFans profiles by name,. The site is inclusive of artists and content creators from all genres and allows them to monetize their content while developing authentic relationships with their fanbase. ☆ Favorite. Large Natural Pink Color Sea Fan Reef Coral 16x17” Beautiful (290) $ 115. Here. Mound and boulder corals grow to look like their name as enormous, round mounds on the sea floor. Linktree. Do you want to look someone up on OnlyFans? Using our website you can find any creator, earner, or model. 8. America’s most iconic coral reef is dying. It lies a few miles seaward of the Florida Keys, is about 4 miles (6 to 7 km) wide and extends. The Florida Reef (aka The Great Florida Reef) is the only living coral barrier reef in the continental United States and the third largest coral barrier reef system in the world. Otherwise visit registration page to create one. Coral reef, ridge or hummock formed in shallow ocean areas by algae and the calcareous skeletons of coral polyps and other coelenterates. View all 49 images and 32 videos for free. Coral reefs are sometimes known as the “rainforests of the sea. Coral reef in the village region: 286 64 -915. Reefs provide a large fraction of Earth’s biodiversity —they have been called “the rain forests of the seas. Crocodiles — Commuting Predators. After thousands of years of active coral growth, Caribbean reefs have lost 80% of their coral cover over only the last two decades – other reefs seem similarly threatened. Soft corals have skeletons that are flexible and can bend with the water. Coral fans and dead coral fans [Bedrock Edition only] naturally generate in coral reef structures. 3% are in Southeast Asia, while 40. 6. The adapted coral forms provide a prime habitat to marine organisms by providing protection and food resources. (Colin, 1978) To get started with a chickens coop in Coral Island, you will only need a few basic items. Coral fans can be placed outside of water in Java Edition as long as one of the blocks surrounding it contains water. Coral is a type of non-solid block that comes in five variants: tube, brain, bubble, fire, and horn. The site is inclusive of artists and content creators from all genres and allows them to monetize their content while developing authentic relationships with their fanbase. Web coral reefs are structures that generate in warm ocean biomes. OnlyFans profile Cassie alias coral_reef has listed their location as oo USA. Unless you’re going to Belize or Australia soon, you owe it to yourself to check it out. However, coral reef development occurs only in areas with specific environmental characteristics: a solid structure for attachment; tropical or subtropical temperatures; clear waters low in phosphate and nitrogen nutrients; and moderate wave action to disperse waste and bring oxygen. Fringing Reefs: Fringing reefs grow near the coastline around islands and continents. 99. Why are coral reefs important? Coral reefs might only occupy 1% of the world’s marine environment but they’re home to about a quarter of the world’s marine species and an important nursery for many fish species. 0. In the lower Keys, where waters are even hotter, entire reefs have been wiped out. “The once colorful coral was a gray ruin and all but dead—a skeletal statue. As a result, they are able to create massive structures like the Great Barrier Reef. View OnlyFans. The disease completely destroys the coral tissue of Caribbean acroporid corals, specifically elkhorn coral (Acropora palmata) and staghorn coral (A. Usually the most common gorgonian in coral reef habitats, it is primarily found on band and patch reefs. Binomial name. Sea turtles are a vital member of coral reef ecosystems, but these highly migratory creatures have a lot more interesting habits you can learn about here. . hide. This has led to renewed interest in the ‘deep reef refugia’ hypothesis (DRRH), which stipulates that deep reef areas (1) are protected or dampened from disturbances that affect shallow reef areas and (2) can provide a viable. Corals generate water and carbon dioxide, byproducts of their cellular respiration. These reefs come in a wide variety of shapes and sizes, with coral blocks topped with coral, and sometimes coral fans and sea pickles. Coral Reef Formation A coral is known as a polyp. Preparation. They are most closely related to Jellyfish and Anemones. One the egg is fertilized, a larva is produced and eventually settles to the bottom. Once you have all of these. Videos. the coral’s ability to form associations with zooxanthellae which facilitates calicification essential for building reefs. Scientists. Nearly 500 million people depend - directly and indirectly – on coral reefs for their livelihoods, food and other resources (Wilkinson, 2004). imgur. report. Coral reefs offer some of the best dive experiences, thanks to their abundant marine life, diverse corals and warm water diving opportunities. Thermal refugia underpin climate-smart management of coral reefs, but whether current thermal refugia will remain so under future warming is uncertain. Stromatolites, such as the ones shown above, are living fossils. A recent report from the National Oceanic and Atmospheric Administration and other research organizations concluded bleaching events are the biggest threat to the world's coral reefs. A group of scientist divers discovered a massive reef of rose-shaped corals between roughly 98 and 213 feet below the Pacific Ocean's surface near French Polynesia's Tahiti islands, UNESCO. Gorgonia ventalina is distributed in a clumped, non-random distribution on coral reefs. Abstract. Coral cactus is a combination of two different species, so it can’t be propagated in the ways other succulents can. Corals provide habitats for fish and other organisms in the. They are mutualism, parasitism, and commensalism. It has a simple, tubelike body with tentacles at. This includes ones important to fishing like spiny lobster, snapper and grouper. Sea fans create a colorful, calming presence while you're scuba diving or snorkeling near a coral reef. Each color of coral fan has a different shape, and can be placed in any orientation. report. Aquarium Fan Coral Decor Crushed Coral for Aquarium, Artificial Coral Plant Aquarium Decorations Ornament Artificial Decoration for Fish Tank Aquarium Landscape Coral Reef Decor Coral Decor. Environmentalists and Democratic lawmakers increasingly are working to bar the sale of sunscreens that may damage coral reefs, but the bans are dividing a surprising group: coral. FREE delivery Jul 10. Best Shemale & Trans OnlyFans Accounts of 2023. The bodies of living polyps are often vivid colors of pink, yellow, blue, purple, and green. Algae’s ability to establish symbiosis in coral without photosynthesis could help fight coral bleaching. Today, stromatolites live in stressed marine environments. What sets them apart from other corals is the presence of a protein called gorgonin. See photos of coral reef fish and sponges. Raja Ampat (which means "four kings") Islands Coral Reefs in Indonesia encompass nearly 5 million acres of Marine Protected Area and has more than 1,600 types of fish. u8614872 (coral_reef) and vipnat are very popular on OF, instead of subscribing for coral_reef content on OnlyFans $19 monthly, you can get all pictures and videos for free download on our site. ly/still-only-one-earth 2 Coral Reefs: Strategies for Ecosystems on the Edge. Benji Jones is a. The Red Sea Fan comes from the deep parts of the reefs of the Indian Ocean and has a classic sea fan appearance. Some look like mushrooms, some trees, fans, honeycombs, flowers, and even brains. @lucy. Coral blocks spawn naturally in coral reefs, found covering on the seafloor in warm ocean biomes. 2. (OnlyFans) Published: 2023-06-04 05:00:52. The growth rate varies with age, food supply, water temperature, and species. This resurrection. Otherwise visit registration page to create one. Discover the captivating world of coral_reef on OnlyFans! Uncover the latest buzz as news broke on Thu Nov 09, 2023, revealing a leaked profile of coral_reef. Because of the many species, the Gorgonia can be found in all the seas, particularly in tropical regions. Others may be whiplike, bushy or even encrusting. They occur in a wide range of depths, from just 130 feet off the coast of Norway to well. Download 1833c71f-4960-4d0a-817a-a8a2cd2dcce8. #1. And here are the best premium LED reef lights according to your tank’s depth in inches: 8-inch deep tank with plenty of SPS corals: Kessil A80 / AI Prime 16HD Reef. It is estimated that most coral reefs are between 5,000 and 10,000 years old, with some actually tracing their beginnings back 50 million years. Blue is a very unusual coloration for any coral, and this Sea Fan will make a great showpiece or centerpiece to any reef aquarium. Use a boat: Coral reefs can be quite large and. Promo. A moray eel and puffer fish jointly take cover under a massive Porites coral boulder. The site is inclusive of artists and content creators from all genres and allows them to monetize their content while developing authentic relationships with their fanbase. Credit: Chasing Coral. As of mid-September, Florida’s coral reefs — the only coral reef system in the continental United States — faced the equivalent of nearly 24 weeks of harmful ocean temperatures,. Scientists have so far discovered more than 2,800 species of these fishes, and are. Mimicry is also frequently seen amongst. 2020. Florida is the only state in the continental U. We offer. Coral reefs cover less than 1 percent of the ocean floor — all the reefs combined would equal an area of about 110,000 square miles (285,000 square km), only about the size of the state of Nevada. Natural buildups of sand or. Hard corals, also known as stony coral, produce a rock-like skeleton made of calcium carbonate (CaCO 3). Coral reefs only take up about 1% of the ocean floor, but host an estimated 25% of all ocean species! This abundance of creatures that are dependent on a specific structure has given coral the nickname “the rainforest of the seas. There are few franchises that can stand the test of time, especially when said franchise is one that began way back in 1937! Coral are generally classified as either “hard coral” or “soft coral”. Out of 723 reef sites, scientists found that 506 reef sites were losing reef habitat annually. ”. Similarly, comprehensive regional assessments of fishing damage rarely exist, impeding evaluations of, and improvements to, conservation measures. cassies_reef / coral_reef instagram. The most common type of reef is the fringing reef. The tutorial is an overview of the biology of and threats to coral reefs, as well as efforts being made to conserve and protect them. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Reef-building corals prefer clear and shallow water, where lots of sunlight filters through to their symbiotic algae. A Guide to Soft Corals (Octocorals) Soft corals refer to the organisms in the class Octocorallia, which includes gorgonians, sea fans, sea pens, sea feathers, and blue corals. United States. Only on the last, a boulder coral roughly the size and shape of an overstuffed ottoman, has the treatment mostly succeeded. 0. A new open access study by researchers at the University of California, Riverside, aims to shed light. The site is inclusive of artists and content creators from all genres and allows them to monetize their content while developing authentic relationships with their fanbase. com/coral_reef 25 Hilarious Lord Of The Rings Memes Only True Fans Will Understand. Here, we provide a baseline dataset, covering 1300 km of tropical coral reef habitats globally, and comprised of over one million geo-referenced, high-resolution photo-quadrats analysed using. Correa says coral-eating predators are typically. Thousands of species rely on reefs for survival. 948 likes · 31 talking about this · 40 were here. 9 billion. Some live only on a single species of coral. In Florida, well-developed coral reef communities exist from Palm Beach County southwest to the Dry Tortugas. Reef systems also can be found in the West Atlantic, East Atlantic, and East Pacific oceans between 30° N and 30° S. 2 percent of the total seafloor, but roughly 25 percent of all marine life depends on coral reefs at some point in their lives. 2 per cent of the world’s ocean, theyIntroduction. Corals are so diverse in their shapes, sizes and colors. There are also deep water and soft corals. According to the Florida Museum of Natural History, its body is entirely covered in bright bands of black, red and yellow. Corals are keystone species for reef and marine ecosystems but coral bleaching due to climate change and ocean warming is killing them. Gorgonia ventalina is distributed in a clumped, non-random distribution on coral reefs. Coral Reef Formation A coral is known as a polyp. They built the first reefs on Earth. Three main zones: (1) reef flat, the sheltered area between the reef and shore; (2) reef crest, the exposed top. m4v; Downloads. ”. com/coral_reef As a matter of fact, yes! Corals also live in many parts of the cold ocean, including deep on the seafloor. Use only the water you need. When combined with an integrated tool that. Nearly a quarter of all the fish in the sea rely on healthy coral reefs. Gorgonian: This family of soft coral is also called sea whips or sea fans. The other community, transect III, consisted of benthic algal covered pavement in its entirety, with only scattered small corals downstream. Web coral reefs can only be found in warm ocean biomes in minecraft. Despite the challenges, they achieved an impressive 90% success rate in 2017 when transplanting the first 90 corals, and 60% in 2019 for the remaining 190. Measured temperatures prove the oceans are warming. These facts about coral reefs are presented in conjunction with the USGS Coral Reef Project. Until recently, fish that eat coral—corallivores—were thought to weaken reef. Any kind of litter pollutes the water and can harm the reef and fish. 6. Only the cause of such warming may be debatable by some. Coralline algae, sponges, and other organisms, combined with a number. Fluctuations in a key aquarium parameter,. Breaking coral fans without Silk Touch destroys the coral fan. Yet, accurate diagnoses of impacts truly caused by trawling are surprisingly rare. Coral reefs are found in shallow water where sea surface temperatures range from 68° F to 97° F. Sponges, shrimps, crabs, turtles, lobsters and hundreds of species of fish live among the corals. is only available to registered users. Large Natural. First, they serve as primary producers, converting sunlight into energy that supports the entire reef ecosystem. Photo: Disney Insider Tips. Coral reefs are some of the most diverse ecosystems in the world. Also coral plants. Derek Manzello, coordinator of the National Oceanic and Atmospheric Administration’s Coral Reef Watch, said that so far this year, at least 35 countries and territories across five oceans and seas. Most hard coral polyps are very small: between 1 and 3 mm in diameter, but. illustration by Zohar LazarCoral reef structures also buffer shorelines against 97 percent of the energy from waves, storms, and floods, helping to prevent loss of life, property damage, and erosion. We offer u8614872 OnlyFans leaked content, you can find list of available content of coral_reef below. Untitled. Going to leave in the desert village region: 71 64 854. Symbiotic relationships are very common in the ocean, especially near coral reefs. Besides, Can you bonemeal coral? Seaweed can be grown underwater […]Look for ocean biomes: Coral reefs only spawn in warm ocean biomes. These can be a variety of colors, but most reflect light in purple, blue, green, or red. Despite being the second most abundant benthic group of organisms on coral reefs, octocorals are not usually considered as reef-builders, although a few taxa do produce massive aragonite skeletons. Coral reefs are important ocean habitats and offer a compelling case of the risks of climate change. Space is at a premium. Coral habitats and corals as habitats 20 Coral reefs Coralline algae Large concentrations of anemones On rocks, walls and hard substrates In caves and fissures On muddy and sandy floors In shallow waters and at great. This not only protects marine life. r/OnlyFansCollabs Rules. They teem with life, with perhaps one-quarter of all ocean species depending on reefs for food and shelter. Marine regions cover about three-fourths of the Earth's surface and include oceans, coral reefs, and estuaries. Cassie @coral_reef OnlyFans Location Details. Soft coral, or aocyonacea, are a type of coral that lack a hard, calcium carbonate skeleton. We would like to show you a description here but the site won’t allow us. Venus sea fan coral is sessile, permanently attached to a surface. Coral Reef Fans 瑚礁粉 珊瑚海水魚器材買賣, 香港. Leave no trace. com/daddyyaches twitter. Introduction.