Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Hydrogen sulfide, not carbon dioxide, may have caused largest mass extinction

04.11.2003


While most scientists agree that a meteor strike killed the dinosaurs, the cause of the largest mass extinction in Earth’s history, 251 million years ago, is still unknown, according to geologists.



"During the end-Permian extinction 95 percent of all species on Earth became extinct, compared to only 75 percent during the KT when the dinosaurs disappeared," says Dr. Lee R. Kump, professor of geosciences. "The end-Permian is puzzling. There is no convincing smoking gun, no compelling evidence of an asteroid impact."

Researchers have shown that the deep oceans were anoxic, lacking oxygen, in the late Permian and research shows that the continental shelf areas in the end-Permian were also anoxic. One explanation is that sea level rose so that the anoxic deep water was covering the shelf. Another possibility is that the surface ocean and deep ocean mixed, bringing anoxic waters to the surface.


Decomposition of organisms in the deep ocean could have caused an overabundance of carbon dioxide, which is lethal to many oceanic organisms and land-based animals.

"However, we find mass extinction on land to be an unlikely consequence of carbon dioxide levels of only seven times the preindustrial level," Kump told attendees today (Nov. 3) at the annual meeting of the Geological Society of America in Seattle. "Plants, in general, love carbon dioxide, so it is difficult to think of carbon dioxide as a good kill mechanism."

On the other hand, hydrogen sulfide gas, produced in the oceans through sulfate decomposition by sulfur bacteria, can easily kill both terrestrial and oceanic plants and animals.

Humans can smell hydrogen sulfide gas, the smell of rotten cabbage, in the parts per trillion range. In the deeps of the Black Sea today, hydrogen sulfide exists at about 34 part per million. This is a toxic brew in which any aerobic, oxygen-needing, organism would die. For the Black Sea, the hydrogen sulfide stays in the depths because our rich oxygen atmosphere mixes in the top layer of water and controls the diffusion of hydrogen sulfide upwards.

In the end-Permian, as the levels of atmospheric oxygen fell and the levels of hydrogen sulfide and carbon dioxide rose, the upper levels of the oceans could have become rich in hydrogen sulfide catastrophically. This would kill most of the oceanic plants and animals. The hydrogen sulfide dispersing in the atmosphere would kill most terrestrial life.

Kump and colleagues, Alexander Pavlov, University of Colorado; Michael Arthur, professor of geosciences, Penn State; Anthony Riccardi, graduate student, Penn State; and Yashuhiro Kato, University of Tokyo, are looking at sediments from the end-Permian found in Japan.

"We are looking for biomarkers, indications of photosynthetic sulfur bacteria," says Kump. "These photo autotrophic organisms live in places where there is no oxygen, but still some sunlight. They would have been in their hay day in the end-Permian." Finding biomarkers of green sulfur bacteria would provide evidence for hydrogen sulfide as the cause of the mass extinctions.

So, what of the 5 percent of the species on Earth that survived? Kump suggests that the mixing of the deep ocean layers and the upper layer was not uniform and that refugia, places where oxygen still existed, remained, both in the oceans and on land.

A’ndrea Elyse Messer | EurekAlert!
Further information:
http://www.psu.edu/

More articles from Earth Sciences:

nachricht How is climate change affecting fauna in the Arctic?
22.05.2017 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

nachricht Sea level as a metronome of Earth's history
19.05.2017 | Université de Genève

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

Im Focus: Using graphene to create quantum bits

In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.

In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...

Im Focus: Bacteria harness the lotus effect to protect themselves

Biofilms: Researchers find the causes of water-repelling properties

Dental plaque and the viscous brown slime in drainpipes are two familiar examples of bacterial biofilms. Removing such bacterial depositions from surfaces is...

Im Focus: Hydrogen Bonds Directly Detected for the First Time

For the first time, scientists have succeeded in studying the strength of hydrogen bonds in a single molecule using an atomic force microscope. Researchers from the University of Basel’s Swiss Nanoscience Institute network have reported the results in the journal Science Advances.

Hydrogen is the most common element in the universe and is an integral part of almost all organic compounds. Molecules and sections of macromolecules are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

Innovation 4.0: Shaping a humane fourth industrial revolution

17.05.2017 | Event News

Media accreditation opens for historic year at European Health Forum Gastein

16.05.2017 | Event News

 
Latest News

New approach to revolutionize the production of molecular hydrogen

22.05.2017 | Materials Sciences

Scientists enlist engineered protein to battle the MERS virus

22.05.2017 | Life Sciences

Experts explain origins of topographic relief on Earth, Mars and Titan

22.05.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>