Emiliania huxleyi
Encyclopedia
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, commonly referred to as 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 alkenone
s, 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 temperature
s.
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. It's coccolith
s 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 coccolith
s 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 the inspiration for James Lovelock
's Gaia hypothesis
which claims that living organisms somehow may be able to self regulate their own conditions of chemistry and climate at a state favourable for life.
Coccolithophore
Coccolithophores are single-celled algae, protists, and phytoplankton belonging to the division of haptophytes. They are distinguished by special calcium carbonate plates of uncertain function called coccoliths , which are important microfossils...
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
Algal bloom
An algal bloom is a rapid increase or accumulation in the population of algae in an aquatic system. Algal blooms may occur in freshwater as well as marine environments. Typically, only one or a small number of phytoplankton species are involved, and some blooms may be recognized by discoloration...
it forms in nutrient depleted waters after the reformation of the summer thermocline
Thermocline
A thermocline is a thin but distinct layer in a large body of fluid , in which temperature changes more rapidly with depth than it does in the layers above or below...
. Like other coccolithophores, E. huxleyi is a single-celled phytoplankton
Phytoplankton
Phytoplankton are the autotrophic component of the plankton community. The name comes from the Greek words φυτόν , meaning "plant", and πλαγκτός , meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye...
covered with uniquely ornamented calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...
disks, commonly referred to as 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 alkenone
Alkenone
Alkenones are highly resistant organic compounds produced by phytoplankton of the class Prymnesiophyceae.The exact function of the alkenones remains under debate....
s, can be found in marine sediments long after other soft parts of the organisms have decomposed. Alkenones are most commonly used by earth scientists
Earth science
Earth science is an all-embracing term for the sciences related to the planet Earth. It is arguably a special case in planetary science, the Earth being the only known life-bearing planet. There are both reductionist and holistic approaches to Earth sciences...
as a means to estimate past sea surface temperature
Sea surface temperature
Sea surface temperature is the water temperature close to the oceans surface. The exact meaning of surface varies according to the measurement method used, but it is between and below the sea surface. Air masses in the Earth's atmosphere are highly modified by sea surface temperatures within a...
s.
Basic Facts
E. huxleyi was named after Thomas HuxleyThomas Huxley
Thomas Henry Huxley PC FRS was an English biologist, known as "Darwin's Bulldog" for his advocacy of Charles Darwin's theory of evolution....
and Cesare Emiliani
Cesare Emiliani
Cesare Emiliani was an Italian-American scientist, considered one of the greatest geologists and micropaleontologists of the 20th century and the founder of paleoceanography, developing the timescale of marine isotope stages, which despite modifications remains in very wide use today.He...
, 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. It's coccolith
Coccolith
Coccoliths are individual plates of calcium carbonate formed by coccolithophores which are arranged around them in a coccosphere.- Formation and composition :...
s 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 coccolith
Coccolith
Coccoliths are individual plates of calcium carbonate formed by coccolithophores which are arranged around them in a coccosphere.- Formation and composition :...
s makes E. huxleyi blooms
Algal bloom
An algal bloom is a rapid increase or accumulation in the population of algae in an aquatic system. Algal blooms may occur in freshwater as well as marine environments. Typically, only one or a small number of phytoplankton species are involved, and some blooms may be recognized by discoloration...
easily visible from space. Satellite
Earth observation satellite
Earth observation satellites are satellites specifically designed to observe Earth from orbit, similar to reconnaissance satellites but intended for non-military uses such as environmental monitoring, meteorology, map making etc....
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 the inspiration for James Lovelock
James Lovelock
James Lovelock, CH, CBE, FRS is an independent scientist, environmentalist and futurologist who lives in Devon, England. He is best known for proposing the Gaia hypothesis, which postulates that the biosphere is a self-regulating entity with the capacity to keep our planet healthy by controlling...
's Gaia hypothesis
Gaia hypothesis
The Gaia hypothesis, also known as Gaia theory or Gaia principle, proposes that all organisms and their inorganic surroundings on Earth are closely integrated to form a single and self-regulating complex system, maintaining the conditions for life on the planet.The scientific investigation of the...
which claims that living organisms somehow may be able to self regulate their own conditions of chemistry and climate at a state favourable for life.
Abundance and Distribution
E. huxleyi is by far the most abundant coccolithophore found in the Earth's oceans, and is considered ubiquitous, occurring everywhere except the polar regions. During massive blooms (which can cover >100,000 square kilometers), EHUX cell concentrations can outnumber those of all other species in the region combined, accounting for 75% or more of the total number of photosynthetic plankton in the area. EHUX blooms regionally act as an important source of calcium carbonate and dimethyl sulfide, the massive production of which can have a significant impact not only on the properties of the surface mixed layer, but also on global climate (Balch et al., 1991). The blooms can can be identified through satellite imagery because of the large amount of light back-scattered from the water column, which provides a method to assess their biogeochemical importance on both basin and global scales. These blooms are prevalent in the Norwegian fjords, causing satellites to pick up "white waters", which describes the reflectance of the blooms picked up by satellites. This is due to the mass of coccoliths reflecting the incoming sunlight back out of the water, allowing the extent of EHUX blooms to be distinguished in fine detail.Ocean Heat Retention
Scattering stimulated by EHUX blooms not only cause more heat and light to be pushed back up into the atmosphere than usual, but also cause more of the remaining heat to be trapped closer to the ocean surface. This is problematic because it is the surface water that exchanges heat with the atmosphere, and EHUX blooms may tend to make the overall temperature of the water column dramatically cooler over longer time periods. However, the importance of this effect, whether positive or negative, is currently being researched and has not yet been established.Contribution to the Greenhouse Effect
Coccolithophore growth, like all phytoplankton growth, turns carbon dioxide into organic matter, thus reducing atmospheric CO2. Given the three forms of dissolved carbon in seawater (CO2, HCO3 and CO3), amounts of the total carbon present in each form is determined by the alkalinity and water temperature of the ocean. However, coccolithophores like EHUX are unique in that they also take up bicarbonate, which they use to form their calcium carbonate shells. These cells removing bicarbonate to form coccoliths can disturb the seawater carbon-system, which causes a re-arrangement in how much carbon is in each dissolved form. This re-arrangement can cause changes in ocean alkalinity, which indirectly causes more of the dissolved carbon to be pushed into the CO2 form. The total effect of this process is that the blooms produce more dissolved CO2 in the water, which directly causes an increase in the rate of global climate change.See also
- CLAW hypothesisCLAW hypothesisThe CLAW hypothesis proposes a feedback loop that operates between ocean ecosystems and the Earth's climate. The hypothesis specifically proposes that particular phytoplankton that produce dimethyl sulfide are responsive to variations in climate forcing, and that these responses lead to a negative...
- CoccolithophoreCoccolithophoreCoccolithophores are single-celled algae, protists, and phytoplankton belonging to the division of haptophytes. They are distinguished by special calcium carbonate plates of uncertain function called coccoliths , which are important microfossils...
- Dimethyl sulfideDimethyl sulfideDimethyl sulfide or methylthiomethane is an organosulfur compound with the formula 2S. Dimethyl sulfide is a water-insoluble flammable liquid that boils at and has a characteristic disagreeable odor. It is a component of the smell produced from cooking of certain vegetables, notably maize,...
- DimethylsulfoniopropionateDimethylsulfoniopropionateDimethylsulfoniopropionate , is an organosulfur compound with the formula 2S+CH2CH2COO−. This zwitterionic metabolite found in marine phytoplankton, seaweeds, and some species of terrestrial and aquatic vascular plants...
- Emiliania huxleyi virus 86 a giant marine virus that infects Emiliania huxleyi
- Ocean acidificationOcean acidificationOcean acidification is the name given to the ongoing decrease in the pH and increase in acidity of the Earth's oceans, caused by the uptake of anthropogenic carbon dioxide from the atmosphere....