Emiliania huxleyi
| Emiliania huxleyi | |
|---|---|
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| A scanning electron micrograph of a single Emiliania huxleyi cell. | |
| Scientific classification | |
| Domain: | Eukaryota |
| (unranked): | Haptophyta |
| Class: | Prymnesiophyceae |
| Order: | Isochrysidales |
| Family: | Noelaerhabdaceae |
| Genus: | Emiliania |
| Species: | E. huxleyi |
| Binomial name | |
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Emiliania huxleyi (Lohm.) Hay and Mohler |
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Emiliania huxleyi, often abbreviated "EHUX", is a species of coccolithophore with a global distribution from the tropics to subarctic waters. It is one of thousands of different photosynthetic plankton that freely drift in the euphotic zone of the ocean, forming the basis of virtually all marine food webs. It is studied for the extensive blooms it forms in nutrient-depleted waters after the reformation of the summer thermocline. Like other coccolithophores, E. huxleyi is a single-celled phytoplankton covered with uniquely ornamented calcite disks called coccoliths (also informally known as liths or scales). Individual coccoliths are abundant in marine sediments although complete coccospheres are more unusual. In the case of E. huxleyi, not only the shell, but also the soft part of the organism may be recorded in sediments. It produces a group of chemical compounds that are very resistant to decomposition. These chemical compounds, known as alkenones, can be found in marine sediments long after other soft parts of the organisms have decomposed. Alkenones are most commonly used by earth scientists as a means to estimate past sea surface temperatures.
Emiliania huxleyi was named after Thomas Huxley and Cesare Emiliani, who were the first to examine sea-bottom sediment and discover the coccoliths within it. It is the most numerically abundant and widespread coccolithophore species. Its coccoliths are transparent and commonly colourless, but are formed of calcite which refracts light very efficiently in the water column. This, and the high concentrations caused by continual shedding of their coccoliths makes E. huxleyi blooms easily visible from space. Satellite images show that blooms can cover large areas, with complementary shipboard measurements indicating that E. huxleyi is by far the dominant phytoplankton species under these conditions. This species has been an inspiration for James Lovelock's Gaia hypothesis which claims that living organisms collectively self-regulate biogeochemistry and climate at nonrandom metastable states.
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