History of Coral in Timeline
Corals are marine invertebrates belonging to the phylum Cnidaria and subphylum Anthozoa. They form colonies of individual polyps and are vital reef builders in tropical oceans. These corals secrete calcium carbonate, creating a hard skeleton structure. A coral "head" is a colony of myriad genetically identical polyps. Each polyp is a sac-like animal typically only a few millimeters in diameter and a few centimeters in height. Reef-building corals are found in shallow, clear, sunny, and agitated water usually between 30°N and 30°S of the Equator.
1911: The Use of Red Coral in Qing Dynasty China
Red coral held cultural significance in China, particularly during the Manchu or Qing Dynasty (1644-1911). Its red color and resemblance to deer antlers linked it to longevity, virtue, and high rank. The Qianlong Emperor established a code in 1759 regulating its use, often combined with pearls in court jewelry or Penjing (miniature mineral trees). A "coral network" traded this precious material, reaching China through the English East India Company.
1998: Worldwide Coral Reef Decline
In 1998, 16% of the world's coral reefs died due to increased water temperatures. Localized threats to coral ecosystems include coral mining, runoff, pollution, overfishing, blast fishing, disease, and canal digging. Broader threats are sea temperature rise, sea level rise and ocean acidification, all linked to greenhouse gas emissions.
2018: Phylosymbiosis between Corals and Microbiomes
A 2018 study found evidence of phylosymbiosis between corals and their microbiomes, especially in the skeleton. Coral microbiome composition reflects coral phylogeny. For example, the abundance of Endozoicomonas bacteria is influenced by both bacterial and coral phylogeny. However, not all coral-associated bacteria demonstrate cophylogeny.
2019: Sanger Sequencing for Coral Microbial Community Analysis
In 2019, Goldsmith et al. demonstrated the effectiveness of Sanger sequencing in studying coral microbial communities. It reproduces the diversity found by next-generation sequencing and produces longer sequences, useful for primer and probe design. This is particularly helpful for studying Astrangia poculata, the northern star coral, and its symbiotic relationship with zooxanthellae.
2020: Challenges in Coral Species Delineation
In 2020, there were 2175 identified coral species, with 237 endangered. Distinguishing between species is crucial for conservation. Morphological and molecular tree-based methods for identification sometimes conflict. Coral adaptation continues in response to climate change.
