Researchers from Flinders University in South Australia and the University of Tasmania recently published their third paper in a series that explores the link between critically low levels of selenium deposits in the ocean floor and three out of five mass extinction events that occurred during the Ordovician, Devonian and Triassic periods.
“Basically, we have a new theory for these three major events because the data shows that during these times the oceans were depleted in these necessary trace elements that all life needs to survive,” said lead analyst and Paleontology professor John Long from Flinders University.
Along with trace elements such as zinc, copper, cobalt and manganese, selenium in particular is required for life in doses that have a very specific tolerance range.
The detailed seafloor analysis of more than 2,500 samples of sediment taken from around the world shows the level of selenium dropped to 1-2 parts per million at or near the end of the Ordovician, Devonian and Triassic Periods.
A baseline measure of today's selenium levels found in pyrite rock taken from the seafloor off Venezuela, was 132 parts per million.
“With further analysis of the rock samples covering the past 3.5 billion years, we might have one of the best explanations for other extinction events, and when life started to return,” said Long.
Research has shown what causes selenium levels to fluctuate is the tectonic movement of continents, causing erosion and trace elements to flow into the ocean.
During quiet periods with less tectonic activity, erosion can reach a point where not enough trace elements flow into the oceans, and they start to get depleted.
Professor Large led the collection of data using new laser technology to measure the selenium concentrations in marine pyrites from the ocean floor.
“Too much selenium is toxic for life and too little retards life, giving us a narrow window of opportunity where life can flourish,” said University of Tasmania Geology professor Ross Large.
While tectonic events such as earthquakes, volcanic eruptions and climate change including ice ages have caused mass extinctions, scientists can now examine the effects of trace element selenium in the timing of these cycles.
In humans, selenium plays a critical role in getting rid of anti-oxidants in the body and is important for the immune system.
Some of the big viral outbreaks such as Ebola, AIDS, SARS Avian Flu (H1N1) have been linked with selenium deficiency in large parts of China and Africa.
Professor Long said, “the implications are vital for understanding our plant's future.
“Without adequate supplies of trace element nutrients in our seas, life can go extinct.
“Our next step will be to fill in the data with more samples across those extinction boundaries to see if we can test our theory even further and find out the precise timing of those events.”
The study was published in Gondwana Research this week.Jump to next article