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. 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 protect the coral. Most reefs grow best in warm, clear 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, worms, echinoderms, sponges and other cnidarians. Coral reefs flourish in ocean waters, they are most found at shallow depths in tropical waters, but deep water and cold water coral reefs exist on smaller scales in other areas.

Coral reefs deliver ecosystem services for tourism and shoreline protection. The annual global economic value of coral reefs is estimated between US$30–375 billion and US$9.9 trillion. Coral reefs are fragile because they are sensitive to water conditions, they are under threat from excess nutrients, rising temperatures, oceanic acidification, sunscreen use, harmful land-use practices, including runoff and seeps. Most coral reefs were formed after the last glacial period when melting ice caused sea level to rise and flood continental shelves. Most coral reefs are less than 10,000 years old; as communities established themselves, the reefs grew pacing rising sea levels. Reefs that rose too could become drowned, without sufficient light. Coral reefs are found in the deep sea away from continental shelves, around oceanic islands and atolls; the majority of these islands are volcanic in origin. Others have tectonic origins. In The Structure and Distribution of Coral Reefs, Charles Darwin set out his theory of the formation of atoll reefs, an idea he conceived during the voyage of the Beagle.

He theorized that subsidence of the Earth's crust under the oceans formed the atolls. Darwin set out a sequence of three stages in atoll formation. A fringing reef forms around an extinct volcanic island as the ocean floor subsides; as the subsidence continues, the fringing reef becomes a barrier reef and an atoll reef. Darwin predicted that underneath each lagoon would be a bedrock base, the remains of the original volcano. Subsequent research supported this hypothesis. Darwin's theory followed from his understanding that coral polyps thrive in the tropics where the water is agitated, but can only live within a limited depth range, starting just below low tide. Where the level of the underlying earth allows, the corals grow around the coast to form fringing reefs, can grow to become a barrier reef. Where the bottom is rising, fringing reefs can grow around the coast, but coral raised above sea level dies. If the land subsides the fringing reefs keep pace by growing upwards on a base of older, dead coral, forming a barrier reef enclosing a lagoon between the reef and the land.

A barrier reef can encircle an island, once the island sinks below sea level a circular atoll of growing coral continues to keep up with the sea level, forming a central lagoon. Barrier reefs and atolls do not form complete circles, but are broken in places by storms. Like sea level rise, a subsiding bottom can overwhelm coral growth, killing the coral and the reef, due to what is called coral drowning. Corals that rely on zooxanthellae can die when the water becomes too deep for their symbionts to adequately photosynthesize, due to decreased light exposure; the two main variables determining the geomorphology, or shape, of coral reefs are the nature of the substrate on which they rest, the history of the change in sea level relative to that substrate. The 20,000-year-old Great Barrier Reef offers an example of how coral reefs formed on continental shelves. Sea level was 120 m lower than in the 21st century; as sea level rose, the water and the corals encroached on what had been hills of the Australian coastal plain.

By 13,000 years ago, sea level had risen to 60 m lower than at present, many hills of the coastal plains had become continental islands. As sea level rise continued, water topped most of the continental islands; the corals could overgrow the hills, forming cays and reefs. Sea level on the Great Barrier Reef has not changed in the last 6,000 years; the age of living reef structure is estimated to be between 8,000 years. Although the Great Barrier Reef formed along a continental shelf, not around a volcanic island, Darwin's principles apply. Development stopped at the barrier reef stage, it formed 300 -- 1,000 m from shore, stretching for 2,000 km. Healthy tropical coral reefs grow horizontally from 1 to 3 cm per year, grow vertically anywhere from 1 to 25 cm per year; as the name implies, coral reefs are made up of coral skeletons from intact

Nihon Yakushi Gakkai is a learned society, which aims to promote the study of the history of pharmacy and to contribute to the development of Japanese pharmaceutical science. The JSHP was founded in 1954 by the chemist Dr. Yasuhiko Asahina, Professor emeritus at the University of Tokyo, who became the first president; the JSHP maintains close relationships with related institutions and learned societies such as the Yōgakushi Gakkai and Nihon Ishi Gakkai. Since 1966, the JSHP has published a biannual journal Yakushigaku Zasshi. English abstracts are accessible from 2015 on. Back-numbers are available as pdf-files from the JSHP’s website. In 2016 the society published an extensive "Encyclopedia of Pharmaceutical History" with contributions of more than 80 experts. Website of the JSHP Yakushigaku Zasshi

Cray Valley Paper Mills Football Club is a football club based in Eltham, in the Royal Borough of Greenwich, England. They are members of the Isthmian League South East Division and play at the Badgers Sports Ground; the club joined Division Two of the Sidcup & Kent League. Playing in green and white, the colours of the mill's vehicles, Their first match was played on 20 September 1919, a 1–0 win against Hamilton House; the club won the division at the first attempt. They joined the Kent County Amateur League, winning Division Three of the western section in 1936–37; the club left the league at the end of the 1954–55 season. Cray Valley subsequently joined the South London Alliance, they won the Premier Division two seasons later. The club won Division One again in 1983–84, finished as runners-up in the Premier Division in 1988–89. In 1991 they joined Division One of the Spartan League; when it merged with the South Midlands League to form the Spartan South Midlands League in 1997, the club were placed in Division One South.

Despite finishing as runners-up in the league's first season, they left to become founder members of the London Intermediate League. However, in 2001 they left becoming members of Division One West. In 2002 -- 03 Cray Valley won earning promotion to the Premier Division. Two seasons they won the Premier Division. After finishing third in 2010–11, they moved up to the Kent League, renamed the Southern Counties East League in 2013; when the league gained a second division in 2016, the club became members of the Premier Division. In 2016–17 they won the London Senior Cup, beating Metropolitan Police 2–1 in the final, becoming the lowest-ranked team to win the trophy, they were runners-up in the Kent Reliance Senior Trophy in the same season. However they were disqualified from the first round of the FA Vase for fielding an ineligible player, former Crystal Palace defender Matthew Parsons; the club lost 4 -- 1 to Balham. The 2018–19 season saw Cray reach the FA Vase final for the first time, in which they lost 3–1 after extra time to Chertsey Town at Wembley Stadium.

They were Southern Counties East League Premier Division champions, earning promotion to the South East Division of the Isthmian League. Cray Valley have had several prominent players appear for them, including former Charlton forward Kevin Lisbie and former Bournemouth player and Bangladesh national team manager Jamie Day; the club played at the sports ground of the paper mills in St Paul's Cray. However, the mills closed in 1981 and the club played at numerous grounds until moving permanently to the Badgers Sports Ground in Eltham. In 2016 Greenwich Borough agreed a 30-year lease to share the ground; the ground includes a 100-seat stand on a small covered area on the other. Kent County League Premier Division Champions 2004–05 Division One West champions 2002–03 Division Three champions 1933–37 South London Alliance Premier Division winners 1980–81 Division One champions 1979–80, 1983–84 Sidcup & Kent League Division Two champions 1919–20 London Senior Cup Winners 2016–17 London Intermediate Cup Winners 2002–03, 2003–04, 2009–10 Kent Intermediate Shield Winners 2004–05 Kent Junior Cup Winners 1921–22, 1977–78, 1980–81 Best FA Cup performance: Preliminary round, 2013–14, 2015–16, 2016–17 Best FA Vase performance: Runners-up, 2018–19 Attendance: 663 vs Canterbury City, FA Vase semi-final, 17 March 2019 Cray Valley Paper Mills F.

C. players Official website