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New theory for the cause of Earth's mass extinctions: lack of essential selenium


Throughout the past 600 million years earth has been hit with five mass extinction events that devastated life on Earth. The dinosaurs were probably wiped out 66 million years ago by a massive meteor falling on modern-day Mexico, while the end-Permian extinction, which wiped out 90 per cent of species 252 million years ago, was probably the result of massive volcanoes in Siberia.

graph showing the apparent percentage (not the absolute number) of marine animal genera becoming extinct during any given time interval. Labels denote the "big five" events
Figure: Apparent percentage (not the absolute number) of
marine animal genera becoming extinct during any given
time interval. Labels denote the "big five" events

There is still debate about the causes of all mass extinctions and it may be necessary to consider combinations of causes. The most often discussed causes include, enhanced volcanic activities, global climate change, asteroid impact and anoxic events in which the middle and even the upper layers of the ocean become deficient or totally lacking in oxygen.

The new study:
An australian group of researchers now have shown that a depletion of trace elements in the oceans could be another major factor in the end of the Ordovician event and two other major extinktion events. Trace elements such as zinc, copper, cobalt, manganese and selenium, in particular, are required for life in doses that have a very specific tolerance range. The researchers investigated the concentration of trace elements in sedimentary pyrite by using laser ablation coupled to inductively coupled plqasma-mass spectrometry (LA-ICPMS).

Selenium requirements as well as toxic levels for phytoplankton, molluscs, fish and many plants and animals have been studies and are very well known. Researchers previously found that a global peak in selenium is linked to periods of high productivity; conversely, a lack of access to selenium would cause fatal deficiencies across a wide range of organisms. By looking through a large dataset of trace elements content in sedimentary rocks from the sea floor throughout the history of the world, the researchers matched extreme, global drops in selenium to one to two parts per million (ppm) with three of the planet’s mass extinction events: the end-Ordovician (443 million years ago), the Late Devonian (359 million years ago), and the end-Triassic (201 million years ago).

The supply of essential trace elements that begin the food chains for all life in the oceans is driven by plate tectonics. The uplift of mountains at plate margins causes erosion of crustal surfaces enabling trace elements to wash into rivers and end up in the seas. When erosion is prolonged and tectonics is slow, the supply of these essential elements slows down, and depletion of certain elements begins. Only activation of Earth’s engine, to drive more mountain building, seems to set the cycle back to normal again.

The researchers admit that their hypothesis is calling for further refinement from additional data, not only from pyrite samples filling in temporal gaps in their database, but also on minimal Se and other essential TE requirements across a wider range of living organisms to develop and test models of ecosystem collapse under times of severe TE oceanic depletion.

The original studies

John A. Long, Ross R. Large, Michael S.Y. Lee, Michael J. Benton, Leonid V. Danyushevsky, Luis M. Chiappe, Jacqueline A. Halpin, David Cantrill, Bernd Lottermoser, Severe selenium depletion in the Phanerozoic oceans as a factor in three global mass extinction events, Gondwana Res., 17 Oct. 2015. DOI: 10.1016/j.gr.2015.10.001

Analytical instrumentation:

New Wave Research, Inc. - UP213 deep-UV YAG Laser Ablation System
New Wave Research, Inc. - UP1903 Solid State Laser Ablation System
Agilent Technologies 7500 a ICP-MS
Agilent Technologies 7700 s ICP-MS

 Related Studies (newest first)

R.R. Large, J.A. Halpin, E. Lounejeva, L.V. Danyushevsky, V.V. Maslennikov, B.G. Lottermoser, P.J. Sack, P.W. Haines, J.A. Long, C. Makoundi, Selenium and cobalt in sedimentary pyrite reveal Phanerozoic cycles of Earth's oxygenation, Gondwana Research (2015). DOI: 10.1016/j.gr.2015.06.004

E.E. Stüeken, R. Buick, A. Bekker, D. Catling, J. Foriel, B.M. Guy, L.C. Kah, H.G. Machel, I.P. Montañez, S.W. Poulton, The evolution of the global selenium cycle: Secular trends in Se isotopes and abundances, Geochim. Cosmochim. Acta, 162 (2015) 109–125. DOI: /10.1016/j.gca.2015.04.033

Eva E. Stüeken, Julien Foriel, Roger Buick, Shane D. Schoepfer, Selenium isotope ratios, redox changes and biological productivity across the end-Permian mass extinction, Chem. Geol., 410 (2015) 28–39. DOI: 10.1016/j.chemgeo.2015.05.021

Ross R. Large, Jacqueline A. Halpin, Elena Lounejeva, Leonid V. Danyushevsky, Valeriy V. Maslennikov, Daniel Gregory, Patrick J. Sack, Peter W. Haines, John A. Long, Charles Makoundi, Aleksandr S. Stepanov, Cycles of nutrient trace elements in the Phanerozoic ocean, Gondwana Res.,  28/4 (2015) 1282–1293. doi:10.1016/j.gr.2015.06.004

Ross R. Large, Jacqueline A. Halpin, Leonid V. Danyushevsky, Valeriy V. Maslennikov, Stuart W. Bull, John A. Long, Daniel D. Gregory, Elena Lounejeva, Timothy W. Lyons, Patrick J. Sack, Peter J. McGoldrick, Clive R. Calver, Trace element content of sedimentary pyrite as a new proxy for deep-time ocean–atmosphere evolution, Earth and Planetary Science Letters, 389 (2014) 209–220. DOI: 10.1016/j.epsl.2013.12.020

Kristen Mitchell, Paul R.D. Mason, Philippe Van Cappellen, Thomas M. Johnson, Benjamin C. Gill, Jeremy D. Owens, Julia Diaz, Ellery D. Ingall, Gert-Jan Reichart, Timothy W. Lyons, Selenium as paleo-oceanographic proxy: A first assessment, Geochim. Cosmochim. Acta, 89 (2012) 302–317. DOI: 10.1016/j.gca.2012.03.038

A. Diener, T. Neumann, U. Kramar, D. Schild, Structure of selenium incorporated in pyrite and mackinawite as determined by XAFS analyses, J. Contam. Hydrol., 133 (2012) 30–39. DOI:10.1016/j.jconhyd.2012.03.003

Y. Nakaguchi, Y. Mitsuhashi, K. Kitahata, A. Fujita, A. Sumiyoshi, Y. Kawai, Selenium speciation in the eastern tropical and subtropical South Pacific Ocean, Sci. Technol., 21 (2008) 25–33

F. Fordyce, Selenium geochemistry and health, Ambio, 36 (2007) 94–97. DOI: 10.1579/0044-7447(2007)36[94:SGAH]2.0.CO;2

G.A. Cutter, K.W. Bruland, The marine biogeochemistry of selenium: a re-evaluation, Limnol. Oceanogr., 29 (1984) 1179–1192. DOI: 10.4319/lo.1984.29.6.1179

A. Shrift, A selenium cycle in nature ?, Nature, 201 (1964) 1304-1305. DOI: 10.1038/2011304a0

Related EVISA Resources

Link Database: Selenium and Animal Health
Link Database: Selenium and Plant Health
Link Database: Environmental cycling of selenium
Brief summary: ICP-MS: A versatile detection system for speciation analysis

Related information:

Early Earth Central: Extinction events
National Geographic: Mass extinctions
Wikipedia: Extinction events

Related EVISA News
February 3, 2014: Natural wetlands contribute significantly to elemental cycling by volatilization
August 9, 2011: New selenium metabolites found in human serum
June 19, 2010: A new Selenium-containing compound, Selenoneine, found as the predominant Se-species in the blood of Bluefin Tuna 
April 30, 2010: High Accumulation of Selenium in Wheat Grains
July 20, 2009: Researchers Reveal Selenium's Metabolism In Life-Giving Amino Acids
October 16, 2005: New light on human selenium metabolism 
March 8, 2005: Selenoprotein P is required for normal sperm development

last time modified: November 12, 2015


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