Coccolith

Coccoliths are individual plates of calcium carbonate formed by coccolithophores (single-celled algae such as Emiliania huxleyi) which are arranged around them in a coccosphere.

Gephyrocapsa oceanica color
False-colour scanning electron micrograph of Gephyrocapsa oceanica, showing the coccoliths.

Formation and composition

Coccoliths are formed within the cell in vesicles derived from the golgi body. When the coccolith is complete these vesicles fuse with the cell wall and the coccolith is exocytosed and incorporated in the coccosphere. The coccoliths are either dispersed following death and breakup of the coccosphere, or are shed continually by some species. They sink through the water column to form an important part of the deep-sea sediments (depending on the water depth). Thomas Huxley was the first person to observe these forms in modern marine sediments and he gave them the name 'coccoliths' in a report published in 1858. Coccoliths are composed of calcium carbonate as the mineral calcite and are the main constituent of chalk deposits such as the white cliffs of Dover (deposited in Cretaceous times), in which they were first described by Henry Clifton Sorby in 1861.

Types

There are two main types of coccoliths, heterococcoliths and holococcoliths. Heterococcoliths are formed of a radial array of elaborately shaped crystal units. Holococcoliths are formed of minute (ca 0.1 micrometre) calcite rhombohedra, arranged in continuous arrays. The two coccolith types were originally thought to be produced by different families of coccolithophores. Now, however, it is known through a mix of observations on field samples and laboratory cultures, that the two coccolith types are produced by the same species but at different life cycle phases. Heterococcoliths are produced in the diploid life-cycle phase and holococcoliths in the haploid phase. Both in field samples and laboratory cultures, there is the possibility of observing a cell covered by a combination of heterococcoliths and holococcoliths. This indicates the transition from the diploid to the haploid phase of the species. Such combination of coccoliths has been observed in field samples, with many of them coming from the Mediterranean.[1][2]

Shape

Helicosphaera-carteri hg
Helicoliths of Helicosphaera carteri
Emiliania huxleyi coccolithophore (PLoS)
Coccosphere of Emiliania huxleyi consisting of overlapping placoliths

Coccoliths are also classified depending on shape. Common shapes include:[3][4]

  • Calyptrolith – basket-shaped with openings near the base
  • Caneolith – disc- or bowl-shaped
  • Ceratolith – horseshoe or wishbone shaped
  • Cribrilith – disc-shaped, with numerous perforations in the central area
  • Cyrtolith – convex disc shaped, may with a projecting central process
  • Discolith – ellipsoidal with a raised rim, in some cases the high rim forms a vase or cup-like structure
  • Helicolith – a placolith with a spiral margin
  • Lopadolith – basket or cup-shaped with a high rim, opening distally
  • Pentalith – pentagonal shape composed of five-four sided crystals
  • Placolith – rim composed of two plates stacked on top of one another
  • Prismatolith – polygonal, may have perforations
  • Rhabdolith – a single plate with a club-shaped central process
  • Scapholith – rhombohedral, with parallel lines in center

Function

Although coccoliths are remarkably elaborate structures whose formation is a complex product of cellular processes, their function is unclear. Hypotheses include defence against grazing by zooplankton or infection by bacteria or viruses; maintenance of buoyancy; release of carbon dioxide for photosynthesis; to filter out harmful UV light; or in deep-dwelling species, to concentrate light for photosynthesis.

Fossil record

Because coccoliths are formed of low-Mg calcite, the most stable form of calcium carbonate, they are readily fossilised. They are found in sediments together with similar microfossils of uncertain affinities (nanoliths) from the Upper Triassic to recent. They are widely used as biostratigraphic markers and as paleoclimatic proxies. Coccoliths and related fossils are referred to as calcareous nanofossils or calcareous nannoplankton (nanoplankton).

References

  1. ^ Fortuño, José Manuel; Cros, Lluïsa (2002-03-30). "Atlas of Northwestern Mediterranean Coccolithophores". Scientia Marina. 66 (S1): 1–182. doi:10.3989/scimar.2002.66s11. ISSN 1886-8134.
  2. ^ Malinverno, E; Dimiza, MD; Triantaphyllou, MV; Dermitzakis, MD; Corselli, C (2008). Coccolithophores of the Eastern Mediterranean sea: A look into the marine microworld. Athens: "ION" Publishing Group. ISBN 978-960-411-660-7.
  3. ^ Amos Winter; William G. Siesser (2006). Coccolithophores. Cambridge University Press. pp. 54–58. ISBN 978-0-521-03169-1.
  4. ^ Carmelo R Tomas (2012). Marine Phytoplankton: A Guide to Naked Flagellates and Coccolithophorids. Academic Press. pp. 161–165. ISBN 978-0-323-13827-7.

External links

Black Sea deluge hypothesis

The Black Sea deluge is the most well known of three hypothetical flood scenarios proposed for the Late Quaternary history of the Black Sea. It is one of the two of these flood scenarios which propose a rapid, even catastrophic, rise in sea level of the Black Sea occurred during the Late Quaternary.

Chalk Group

The Chalk Group (often just called the Chalk) is the lithostratigraphic unit (a certain number of rock strata) which contains the Late Cretaceous limestone succession in southern and eastern England. The same or similar rock sequences occur across the wider northwest European chalk 'province'. It is characterised by thick deposits of chalk, a soft porous white limestone, deposited in a marine environment.

Chalk is a limestone that consists of coccolith biomicrite. A biomicrite is a limestone composed of fossil debris ("bio") and calcium carbonate mud ("micrite"). Most of the fossil debris in chalk consists of the microscopic plates, which are called coccoliths, of microscopic green algae known as coccolithophores. In addition to the coccoliths, the fossil debris includes a variable, but minor, percentage of the fragments of foraminifera, ostracods and mollusks. The coccolithophores lived in the upper part of the water column. When they died, the microscopic calcium carbonate plates, which formed their shells settled downward through the ocean water and accumulated on the ocean bottom to form a thick layer of calcareous ooze, which eventually became the Chalk Group.

The Chalk Group usually shows few signs of bedding, other than lines of flint nodules which become common in the upper part. Nodules of the mineral pyrite also occur and are usually oxidized to brown iron oxide on exposed surfaces.

Well-known outcrops include the White Cliffs of Dover, Beachy Head, the southern coastal cliffs of the Isle of Wight and the quarries and motorway cuttings at Blue Bell Hill, Kent, (which has been classified as a Site of Special Scientific Interest) and at the Stokenchurch Gap on the Oxfordshire/Buckinghamshire border where the M40 motorway cuts through the Aston Rowant National Nature Reserve.

Coccoid

Coccoid means shaped like or resembling a coccus, that is, spherical.The noun coccoid or coccoids may refer to:

a level of organization, characterized by unicellular, non-flagellated, non-amoeboid organisms, with a definite shape, in general but not always ovoid. It is found in many groups, e.g.:

some bacteria, also called cocci (pl. of coccus)

some green algae, like the desmids and the former Chlorococcales (now in several orders within the division Chlorophyta)

some dinoflagellates, notably Symbiodinium

some chrysophytes

some xanthophytes

the diatoms

the superfamily Coccoidea of scale insects

the Coccidae family within the Coccoidea

Coccolithophore

A coccolithophore (or coccolithophorid, from the adjective) is a unicellular, eukaryotic phytoplankton (alga). They belong either to the kingdom Protista, according to Robert Whittaker's Five kingdom classification, or clade Hacrobia, according to the newer biological classification system. Within the Hacrobia, the coccolithophorids are in the phylum or division Haptophyta, class Prymnesiophyceae (or Coccolithophyceae). Coccolithophorids are distinguished by special calcium carbonate plates (or scales) of uncertain function called coccoliths, which are also important microfossils. However, there are Prymnesiophyceae species lacking coccoliths (e.g. in genus Prymnesium), so not every member of Prymnesiophyceae is coccolithophorid. Coccolithophores are almost exclusively marine and are found in large numbers throughout the sunlight zone of the ocean.

The most abundant species of coccolithophore, Emiliania huxleyi, belongs to the order Isochrysidales and family Noëlaerhabdaceae. It is found in temperate, subtropical, and tropical oceans. This makes E. huxleyi an important part of the planktonic base of a large proportion of marine food webs. It is also the fastest growing coccolithophore in laboratory cultures. It is studied for the extensive blooms it forms in nutrient depleted waters after the reformation of the summer thermocline. and for its production of molecules known as alkenones that are commonly used by earth scientists as a means to estimate past sea surface temperatures. Coccolithophores are of particular interest to those studying global climate change because as ocean acidity increases, their coccoliths may become even more important as a carbon sink. Furthermore, management strategies are being employed to prevent eutrophication-related coccolithophore blooms, as these blooms lead to a decrease in nutrient flow to lower levels of the ocean.

Coccolithovirus

Coccolithovirus is a genus of giant double-stranded DNA virus, in the family Phycodnaviridae. Algae, specifically Emiliania huxleyi, a species of coccolithophore[1], serve as natural hosts. There is currently only one species in this genus: Emiliania huxleyi virus 86.

Elma González

Elma L. González (born June 6, 1942) is a Mexican-born American plant cell biologist. She is Professor Emerita of Ecology and Evolutionary Biology at the University of California, Los Angeles. In 1974, she was appointed professor of cell and molecular biology at the University of California, Los Angeles. At the time, she was the only Mexican American woman scientist in the University of California system faculty. Professor Martha Zúñiga at the University of California, Santa Cruz, appointed in 1990, was the second. In 2004, the Society for the Advancement of Chicanos/Hispanics and Native Americans in Science recognized González with a Distinguished Scientist Award.

Emiliania huxleyi

Emiliania huxleyi is a species of coccolithophore found in almost all ocean ecosystems from the equator to sub-polar regions, and from nutrient rich upwelling zones to nutrient poor oligotrophic 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. 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.

Glossary of geology

This glossary of geology is a list of definitions of terms and concepts relevant to geology, its sub-disciplines, and related fields. For other terms related to the Earth sciences, see Glossary of geography terms.

Haynesville Shale

The Haynesville Shale is an informal, popular name for a Jurassic Period rock formation that underlies large parts of southwestern Arkansas, northwest Louisiana, and East Texas. It lies at depths of 10,500 to 13,000 feet below the land’s surface. It is part of a large rock formation which is known by geologists as the Haynesville Formation. The Haynesville Shale underlies an area of about 9,000 square miles and averages about 200 to 300 feet thick. The Haynesville Shale is overlain by sandstone of the Cotton Valley Group and underlain by limestone of the Smackover Formation.It contains vast quantities of recoverable natural gas. This natural gas is known as "shale gas" because the wells produce from low permeability mudstones that are also the source for the natural gas. It was known to contain large quantities of natural gas prior to 2008. However, prior to that time, it was uneconomic to extract the natural gas. As a result of rising gas prices and improved technology in hydraulic fracturing and directional drilling, it became possible to extract the gas from the Haynesville Shale in an economic and cost-effective manner.

Marine biogenic calcification

Marine biogenic calcification is the process by which marine organisms such as oysters and clams form calcium carbonate. Seawater is full of dissolved compounds, ions and nutrients that organisms can utilize for energy and, in the case of calcification, to build shells and outer structures. Calcifying organisms in the ocean include molluscs, foraminifera, coccolithophores, crustaceans, echinoderms such as sea urchins, and corals. The shells and skeletons produced from calcification have important functions for the physiology and ecology of the organisms that create them.

Marine life

Marine life, or sea life or ocean life, is the plants, animals and other organisms that live in the salt water of the sea or ocean, or the brackish water of coastal estuaries. At a fundamental level, marine life affects the nature of the planet. Marine organisms produce oxygen and sequester carbon. Shorelines are in part shaped and protected by marine life, and some marine organisms even help create new land. The term marine comes from the Latin mare, meaning sea or ocean.

Most life forms evolved initially in marine habitats. By volume, oceans provide about 90 percent of the living space on the planet. The earliest vertebrates appeared in the form of fish, which live exclusively in water. Some of these evolved into amphibians which spend portions of their lives in water and portions on land. Other fish evolved into land mammals and subsequently returned to the ocean as seals, dolphins or whales. Plant forms such as kelp and algae grow in the water and are the basis for some underwater ecosystems. Plankton forms the general foundation of the ocean food chain, particularly the phytoplankton which are key primary producers.

Marine invertebrates exhibit a wide range of modifications to survive in poorly oxygenated waters, including breathing tubes as in mollusc siphons. Fish have gills instead of lungs, although some species of fish, such as the lungfish, have both. Marine mammals, such as dolphins, whales, otters, and seals need to surface periodically to breathe air.

A total of 230,000 documented marine species exist with some two million marine species yet to be documented. Marine species range in size from the microscopic, including phytoplankton which can be as small as 0.02 micrometres, to huge cetaceans (whales, dolphins and porpoises), including the blue whale – the largest known animal reaching 33 metres (108 ft) in length. Marine microorganisms, including protists, bacteria and viruses, constitute about 70% of the total marine biomass.

Paleontology in Oregon

Paleontology in Oregon refers to paleontological research occurring within or conducted by people from the U.S. state of Oregon. Oregon's geologic record extends back approximately 400 million years ago to the Devonian period, before which time the state's landmass was likely submerged under water. Sediment records show that Oregon remained mostly submerged until the Paleocene period. The state's earliest fossil record includes plants, corals, and conodonts. Oregon was covered by seaways and volcanic islands during the Mesozoic era. Fossils from this period include marine plants, invertebrates, ichthyosaurs, pterosaurs, and traces such as invertebrate burrows. During the Cenozoic, Oregon's climate gradually cooled and eventually yielded the environments now found in the state. The era's fossils include marine and terrestrial plants, invertebrates, fish, amphibians, turtles, birds, mammals, and traces such as eggs and animal tracks.

Oregon has a long tradition of paleontological research. Local Native Americans devised myths to explain fossils. By the mid-19th century local fossils had come to the attention of formally trained scientists, and modern research has produced data on climate change and extinction.

The Oligocene dawn redwood Metasequoia occidentalis is the Oregon state fossil.

Pelagic sediment

Pelagic sediment or pelagite is a fine-grained sediment that accumulates as the result of the settling of particles to the floor of the open ocean, far from land. These particles consist primarily of either the microscopic, calcareous or siliceous shells of phytoplankton or zooplankton; clay-size siliciclastic sediment; or some mixture of these. Trace amounts of meteoric dust and variable amounts of volcanic ash also occur within pelagic sediments.

Based upon the composition of the ooze, there are three main types of pelagic sediments: siliceous oozes, calcareous oozes, and red clays.The composition of pelagic sediments is controlled by three main factors. The first factor is the distance from major landmasses, which affects their dilution by terrigenous, or land-derived, sediment. The second factor is water depth, which affects the preservation of both siliceous and calcareous biogenic particles as they settle to the ocean bottom. The final factor is ocean fertility, which controls the amount of biogenic particles produced in surface waters.

Pleurochrysis carterae

Pleurochrysis carterae is a marine species of unicellular coccolithophorid algae that has the ability to calcify subcellularly. They produce calcified scales, known as coccoliths, which are deposited on the surface of the cell resulting in the formation of a coccosphere. Pleurochrysis carterae produce heterococcoliths which are composed of crystal units of variable shapes and sizes.

Rock Chalk, Jayhawk

"Rock Chalk, Jayhawk" (a.k.a. the "Rock Chalk" chant) is a chant used at University of Kansas Jayhawks sporting events. The chant is made up of the phrase "Rock chalk, Jayhawk, KU".

Ruhpolding Formation

The Ruhpolding Formation is a sedimentary formation of the Northern Calcareous Alps deposited during the Upper Jurassic. The open marine radiolarite is very rich in silica.

Syracosphaera azureaplaneta

Syracosphaera azureaplaneta is a species of coccolithophore. This oceanic phytoplankton is not common, but is widely distributed and is known to occur in all the major seas, from tropical to sub-arctic regions. It is named after the BBC TV documentary series, The Blue Planet.

Tuffeau stone

Tuffeau stone — in French, simply tuffeau or tufeau — is a local limestone of the Loire Valley of France. It is characterized as a chalky or sandy, fine-grained limestone, white to yellowish-cream in appearance, and micaceous (containing some white flakes of mica, or muscovite). The soft stone is extracted from numerous quarries and has made a major mark on the architectural landscape of the Loire and its tributaries — especially the valley's world-famous chateaux.

Zenith Plateau

The Zenith Plateau is a large bathymetric high in the Indian Ocean, located about 450 kilometres (280 mi) west-northwest of the Wallaby Plateau, 1,400 kilometres (870 mi) west-northwest of Carnarvon, Western Australia, and 1,700 kilometres (1,100 mi) north-west of Perth, Western Australia. The summit of the Zenith Plateau lies 1,960 meters (6,430 ft) below sea level and its base is at about 5,000 meters (16,000 ft) below sea level. It is about 300 kilometres (190 mi) long and 200 kilometres (120 mi) wide. In the east, the Zenith Plateau is separated from the Wallaby (Cuvier) Plateau by a 100–150 kilometres (62–93 mi) wide, north to northeast-trending bathymetric trough. The Zenith Plateau lies outside of the Australian Exclusive Economic Zone.As discussed by Amos and Beaman, the bathymetry of the Zenith Plateau is very poorly mapped. Precise ocean floor depth data from bathymetric surveys, which used modern acoustic echosounders, across this undersea plateau are lacking. Transects across it by older, less precise singlebeam echosounder are few and insufficient to provide bathymetric data of significant detail. The bulk of the mapping is based upon coarse interpretation of satellite altimetry data in which the ocean floor bathymetry is inferred from measured variations in the elevation of the overlying sea surface.

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