Қара маржан: құрылысы, өмір сүру ортасы және пайдалануы

Order of soft deep water corals with chitin skeletons

Antipatharians, also known as black corals or thorn corals, Black corals are also known as thorn corals due to the microscopic spines lining their skeletons. In Malay, the corals are called akah bahar ("root of the sea"), likely named for their tendency to grow at low light depths.

The skeletons of these corals grow in many patterns unique to this order, such as whips, trees, fans, or coils. These range in size from , though polyps can be as small as in size. Skeletons are also lined with tiny spikes. and are gelatinous and have six tentacles (the same as hard corals and unlike soft corals, which have eight). These polyps can be nearly any color. Unlike the vast majority of other corals, black corals have no protection against abrasive materials such as sand and rocks and lack muscular development which can help the corals to hide. These factors can lead to sediment tearing the soft tissue, resulting in death. In response, corals live near crevices, which allows much of their body to be protected. Black corals are found on reefs, and may contribute to overall reef building, but are also often found as solitary colonies on isolated outcroppings. Most individuals require a hard surface for attachment. They will frequently grow where undersea currents flow, which allows them to feed on the meiofauna that is swept by. Since undersea currents benefit the corals, they will often grow on or by geographic structures that cause currents, such as continental slopes, cliffs, caves, or undersea plateaus.

Black corals are carnivorous, with the coral's polyps allowing it to feed mostly on meiofauna such as zooplankton.

Due to the slow life cycle and deep water habitats of black coral, little is known about their life cycle and reproduction. Asexual reproduction can also occur if a branch breaks off and a replacement is needed. Sexual reproduction in these corals remains largely unstudied. It occurs after the coral colony is established; a colony will produce eggs and sperm, which meet in the water to create larvae that use currents to disperse and settle in new areas. A large tall coral tree is somewhere between 30 and 40 years old. Rarely, black corals will grow too large to support their own weight, and collapse. More recent harvesting has been for use as jewelry. Many Indo Pacific peoples believed that black coral has curative and anti evil powers and made them into necklace and bracelets; however, black corals are not ideal for jewelry making due to it being soft as opposed to stony, causing jewelry made with it to dry out and break. The best studied and regulated black coral fisheries are in Hawaii, where they have been harvested since the 1960s. In the Caribbean harvesting is typically done to produce jewelry for sale to tourists, and has followed a boom and bust cycle, where new coral populations are discovered and overexploited leading to rapid declines. leading to widespread black coral population declines. Despite improvements in management in Cozumel, including no harvesting permits issued since the mid 1990s, the black coral population had failed to recover when assessed in 2016. Though it is illegal to move black corals across international borders without authorization, as they are listed in Appendix II of the Convention on International Trade in Endangered Species (CITES), it is still possible to buy them. Though various methods have been proposed for quicker and more efficient rejuvenation of black coral colonies, none have worked to the point where these corals could be commercially farmed.

Though black corals are not listed on the IUCN Red List, a number of factors threaten them today. The largest single threat is poaching— though the majority of black coral fisheries are heavily regulated, there is still a black market for the corals. Particularly on tropical islands and Madagascar, the market for illegally harvested black corals is large. Due to overfishing of mature corals, in some areas nearly 90% of corals are juveniles (less than tall.) Global warming is the primary threat to black corals worldwide, as well as all other corals. Though black corals rarely builds reefs (the most threatened areas), threats caused by climate change such as coral bleaching, rising sea temperatures, changing underwater currents, and changing salinity and pH also affect deep sea corals. Invasive species such as Carijoa riisei, which were introduced to Hawaiian waters by humans, may pose a significant threat to black corals.