Emiliania huxleyi

Emiliania huxleyi is a species of unicellular, eukaryotic phytoplankton, (also known as a coccolithophore), and is found in nearly all oceanic ecosystems outside of polar regions.^[8] Emiliania huxleyi is the most common coccolithophore.^[4,5] Named after Thomas Henry Huxley, Emiliania huxleyi, (also abbreviated Ehux) plays an important role in all ecosystems in which it is found.

Classification

Domain: Eukaryota

(unranked): Haptophyta

Class: Prymnesiophyceae

Order: Isochrysidales

Family: Noelaerhabdaceae

Genus: Emiliania

Species: E. huxleyi

Scientific interest in Ehux

An E. huxleyi bloom viewed from space. Photo courtesy of NASA.

Emiliania huxleyi is tremendously successful at converting inorganic carbon into products used in photosynthesis and biomineralization.^[7] E. huxleyi, like many other phytoplankton, is very important to the ecosystems it inhabits. Blooms of Ehux can be seen as large turquoise patches in the water through satellite imagery, covering hundreds of thousands of square meters of ocean.^[7] A study of E. huxleyi populations in 2014 discovered a poleward migration path by the phytoplankton.^[8] This indicates that, over time, conditions near the poles have become more favorable for Ehux survival.

Some possible explanations for the migration pattern could be decreasing pH near the equator due to ocean acidification and generally rising oceanwater temperature.^[3,5] This migration will have effects on both the ecosystems they leave behind and the new ecosystems they settle into at the more northern/southern latitude destination.

Ehux is made up of unique plates that are called coccoliths, consisting of calcium carbonate (Ca CO₃). Therefore the formation of Ehux's coccoliths release CO₂, acting as a carbon source. However, they can also act as a carbon sink when they photosynthesize and take away CO₂. Because of this, Ehux has can have an effect on the global climate.^[2] Ehux blooms can also block out sunlight to the ocean below them. They also affect the sulfur cycle because they produce DSMP (dimethylsulfonioproprionate) which creates dimethyl sulfide (DMS) clouds.^[1]

E. huxleyi Viruses (EhVs)

The purple marks the virus on the Ehux's coccoliths.^[1]

Coccolithoviruses have been affecting Ehux for about 7,000 years now.^[1] The virus enters Ehux through the cell membrane by membrane fusion and replicates its RNA polymerase genes in the cytoplasm, alters the lipids of Ehux, and ultimately ruptures the cell and kills it.^[4] When Ehux blooms begin to collapse from viruses killing it, calcium carbonate falls to the sediments at the ocean floor. It has also been found that the remaining Ehux skeletons still contain the virus's DNA that can persist for a long time.^[1] Some suggest that the coccoliths of the Ehux provides a barrier that can limit virus infection. Loose coccoliths in the water have also prevented infection of viruses in other Ehux populations because the free virion bind to the loose coccolith and stops infection of further hosts.^[4]

Role in cloud formation

After abundant Ehux blooms die-off from viruses infecting them, they either fall to sediments at the ocean floor or they can be sent into the atmosphere from being swept up by ocean waves. When this happens, Ehux contributes to cloud formation by providing the surface area for water vapor to create droplets that accumulate and produce clouds.^[6]

References

[1] Ehux: The Little Eukaryote with a Big History. (n.d.). . https://schaechter.asmblog.org/schaechter/2012/08/ehux-the-little-eukaryote-with-a-big-history.html.

[2] Emiliania huxleyi Annotation Consortium, B. A. Read, J. Kegel, M. J. Klute, A. Kuo, S. C. Lefebvre, F. Maumus, C. Mayer, J. Miller, A. Monier, A. Salamov, J. Young, M. Aguilar, J.-M. Claverie, S. Frickenhaus, K. Gonzalez, E. K. Herman, Y.-C. Lin, J. Napier, H. Ogata, A. F. Sarno, J. Shmutz, D. Schroeder, C. de Vargas, F. Verret, P. von Dassow, K. Valentin, Y. Van de Peer, G. Wheeler, J. B. Dacks, C. F. Delwiche, S. T. Dyhrman, G. Glöckner, U. John, T. Richards, A. Z. Worden, X. Zhang, and I. V. Grigoriev. 2013. Pan genome of the phytoplankton Emiliania underpins its global distribution. Nature 499:209–213.

[3] Gerald Langer, G. Nehrke, Ian Probert, J. Ly, P. Ziveri. Strain-specific responses of Emiliania huxleyi to changing seawater carbonate chemistry . Biogeosciences, European Geosciences Union, 2009, 6 (11), pp.2637-2646. <10.5194/bg-6-2637-2009>. <hal-01258266>

[4] Haunost, M., U. Riebesell, and L. T. Bach. 2020. The Calcium Carbonate Shell of Emiliania huxleyi Provides Limited Protection Against Viral Infection. Frontiers in Marine Science 7.

[5] Hay, W.W.; Mohler, H.P.; Roth, P.H.; Schmidt, R.R.; Boudreaux, J.E. (1967), "Calcareous nannoplankton zonation of the Cenozoic of the Gulf Coast and Caribbean-Antillean area, and transoceanic correlation", Transactions of the Gulf Coast Association of Geological Societies, 17: 428–480.

[6] PerkinsAug. 15, S., 2018, and 11:15 Am. 2018, August 15. This alga may be seeding the world’s skies with clouds. https://www.sciencemag.org/news/2018/08/alga-may-be-seeding-world-s-skies-clouds.

[7] Read, Betsy A., et al. “Pan Genome of the Phytoplankton Emiliania Underpins Its Global Distribution.” Nature, vol. 499, no. 7457, Dec. 2013, pp. 209–213., doi:10.1038/nature12221.

[8] Winter, Amos, et al. “Poleward Expansion of the Coccolithophore Emiliania Huxleyi.” Journal of Plankton Research, vol. 36, no. 2, 2013, pp. 316–325., doi:10.1093/plankt/fbt110.