Emiliania huxleyi Home Page

Welcome to the home page for "Ehux"

Introduction to Emiliania huxleyi (Ehux)

What links country-sized patches of bright turquoise water in the oceans, CO2 concentrations in the atmosphere, and the white cliffs of Dover? The answer is an armour-plated, photosynthesising single-celled creature, so small that it is invisible to the naked eye and is barely discernible under a light microscope. With it's beautiful appearance and its planetary importance, Emiliania huxleyi is a source of interest for all those looking to understand how life and its environment interact.

Picture courtesy of Jess Gorick (copyright held).

Phytoplankton: Emiliania huxleyi is one of 5000 or so different species of phytoplankton - freely drifting, photosynthesising microscopic organisms that live in the upper, sunlit layers of the ocean. Phytoplankton are the oceanic equivalents of terrestrial plants, forming the basis of virtually all marine food webs. The total phytoplankton biomass outweighs that of all the marine animals (zooplankton, fish, whales) put together, and phytoplankton productivity is one of the primary forces in regulating our planetary climate - for instance via impacts on atmospheric carbon dioxide levels which are tightly linked to the oceanic concentrations.

Coccolithophores: The peculiar, and beautiful, armoured appearance of the Ehux cells is due to their possession of calcium carbonate platelets ( coccoliths) used to cover the exterior of the cell. We don't yet know exactly why the cells secrete these small shields around themselves, although many hypotheses have been put forward. Coccolith-bearing phytoplankton species, of which Ehux is just one, are called coccolithophores.

Occurrence: Ehux is by far the most abundant of the coccolithophores on a global basis, and is extremely widespread, occurring in all except the polar oceans. When water conditions are favourable, it has the capacity to occur in massive blooms, sometimes > 100,000 square kilometres (the size of England) in extent. During these blooms the numbers of Ehux cells usually outnumber those of all other species combined, frequently accounting for 80 or 90% or more of the total number of phytoplankton cells in the water. The cells are accompanied by even larger numbers of coccoliths; many of them attached to the cells but also many floating separately in the water. The freely floating coccoliths are thought to arise due to over-production of coccoliths leading to the synthesis of more than can be securely held on the cell surface. Other possible causes are death of the cell after which the empty coccospheres disintegrate, and asexual cell division after which the coccosphere must presumably break open to let out one or both of the two inhabitants. Ehux may well be unique amongst the coccolithophores in its generation of so many free coccoliths.

Why the interest in Emiliania huxleyi?

History: Partly of course because of the exquisite beauty of the coccolith-laden cells (pictures), which, because of their small size, have only been appreciated since electron microscopes were developed in the early 1950's. Before that the Ehux cells and coccoliths were only apparent as faint smudges under light microscopes. Thomas Henry Huxley ("Darwin's bulldog") was one of the first to examine sea-bottom mud and to detect coccoliths within it, and the first to use the term "coccolith". In turn the species Emiliania huxleyi is named after him. Ehux is also interesting because its blooms produce a marked change in the appearance of the water, turning it a milky turquoise colour during intense blooms. These blooms are particularly prevalent in Norwegian fjords such as the Oslo fjord, discolouring the water and perturbing the environment for other organisms, and affecting bathing conditions. The cause of the "white waters" pictured above (click here for more) occasionally seen in the oceans was for a long time a mystery (quote), until coccolithophores such as Ehux were discovered as the culprits.

White waters: We now understand further that these white waters are brought about by the coccoliths (not the organic cells themselves) which act like minute (smaller than pinhead-sized) mirrors suspended in the water. En masse they cause a significant amount of the incoming sunlight to be reflected back out of the water. Water containing large amounts of coccoliths is optically similar to water if sackloads of glitter or sequins were to be added to it. This property of the blooms makes Ehux uniquely accessible to scientific investigation - the reflectance from the blooms can be picked up by satellites in space, allowing the extent of the blooms of this single species to be distinguished in fine detail. The presence of chlorophyll in the water can be detected by satellite, but this does not tell us which individual phytoplankton species or set of species is responsible. In contrast, the presence of coccoliths can be detected separately, delineating precisely the extent of a coccolithophore bloom:
[satellite pictures of blooms]
[space shuttle pictures of blooms]

Picture courtesy of Glynn Gorick (copyright held).

Global aspects

Distribution: These satellite pictures give us a special insight into the world-wide biogeography of this species, and a groundbreaking study has analysed CZCS satellite images from all over the globe to give us an idea of the global distribution of Ehux.

Biogeochemistry: A final reason for the interest in Ehux is its global significance. The coccolith bloom areas are highly reflective, causing more light and heat to be reflected back out to space rather than heating the ocean. The construction of huge numbers of coccoliths from calcium and carbon, and their subsequent sinking to the ocean floor, also perturbs the ocean carbon system and eventually makes a difference to the amount of CO2 that can be stored in the atmosphere to contribute to the CO2 greenhouse effect. As well as exerting an impact on climate change, the long-term flux of coccoliths to the ocean floor goes to form chalk and limestone rocks - for instance the white cliffs of Dover are in large part made up of coccoliths that fell to the sea bed many millions of years ago. You are probably standing over many metres of coccolith-composed rocks as you read this.

Links to specific topics:

Vital Statistics

Cellular description

Life cycle




Optical effects

Biogeochemical impacts

Geological context & evolutionary origins

Grim future for Ehux?

Bibliographies of Ehux research

Global Emiliania Modelling (GEM) initiative



Toby Tyrrell : T.Tyrrell@noc.soton.ac.uk