Oxygen Catastrophe
Encyclopedia
The Great Oxygenation Event (GOE), also called the Oxygen Catastrophe or Oxygen Crisis or Great Oxidation, was the biologically
induced appearance of free oxygen (O2) in Earth's atmosphere. This major environmental change happened around 2.4 billion years ago.
Photosynthesis
was producing oxygen both before and after the GOE. The difference was that before the GOE, organic matter and dissolved iron chemically captured any free oxygen. The GOE was the point when these minerals became saturated and could not capture any more oxygen. The excess free oxygen started to accumulate in the atmosphere.
The rising oxygen levels may have wiped out a huge portion of the Earth's anaerobic
inhabitants at the time. Cyanobacteria, by producing oxygen, were essentially responsible for what was likely the largest extinction event in Earth's history. Additionally the free oxygen combined with atmospheric methane, triggering the Huronian glaciation, possibly the longest snowball Earth
episode ever.
The amount of oxygen
in the atmosphere has fluctuated ever since.
in Minnesota. Oxygen only began to persist in the atmosphere in small quantities shortly (~50 million years) before the start of the GOE. Without a draw-down, oxygen could accumulate very rapidly: for example, at today's rates of photosynthesis (which are admittedly much greater than those in the plant-free Precambrian), modern atmospheric O2 levels could be produced in around 2,000 years.
Another theory is an interpretation of the supposed oxygen indicator, mass-independent fractionation
of sulfur isotopes, used in previous studies, and that oxygen producers did not evolve until right before the major rise in atmospheric oxygen concentration. This theory would eliminate the need to explain a lag in time between the evolution of oxyphotosynthetic microbes and the rise in free oxygen.
Either way, the oxygen did eventually accumulate in the atmosphere, with two major consequences. First, it oxidized atmospheric methane (a strong greenhouse gas
) to carbon dioxide (a weaker one) and water, triggering the Huronian glaciation. The latter may have been a full-blown, and possibly the longest ever, snowball Earth
episode, lasting 300-400 million years. Second, the increased oxygen levels provided a new opportunity for biological diversification
, as well as tremendous changes in the nature of chemical interactions between rocks
, sand
, clay
, and other geological substrates and the Earth's air, oceans, and other surface waters. Despite natural recycling of organic matter
, life had remained energetically limited until the widespread availability of oxygen. This breakthrough in metabolic evolution greatly increased the free energy
supply to living organisms, having a truly global environmental impact; mitochondria evolved after the GOE.
. Evidence for this phenomenon is found in older rocks that contain massive banded iron formation
s that were apparently laid down as this iron and oxygen first combined; most of the planet's commercial iron ore is in these deposits. But these chemical phenomena do not seem to account for the lag completely.
, which was also a big trap for molecular oxygen, because oxygen readily oxidizes methane to carbon dioxide
(CO2) and water in the presence of UV radiation
. Modern methanogens require nickel as an enzyme cofactor
. As the Earth's crust cooled, the supply of nickel from volcanoes was reduced and less methane was produced allowing oxygen to dominate the atmosphere. From 2.7 to 2.4 billion years ago, the levels of nickel deposited declined steadily; it was originally 400 times today's levels.
, to explain the 300-million-year lag comes from a mathematical model of the atmosphere which recognizes that UV shielding decreases the rate of methane oxidation once oxygen levels are sufficient to support the formation of an ozone layer
. This explanation proposes a system with two steady state
s, one with lower (0.02%) atmospheric oxygen content, and the other with higher (21% or more) oxygen content. The Great Oxidation can then be understood as a switch between lower and upper stable steady states.
of sulfur dioxide, which causes MIF). This change from MIF to MDF of sulfur isotopes also may have been caused by an increase in glacial weathering, or the homogenization of the marine sulfur pool as a result of an increased thermal gradient during the Huronian glaciation period.
s on Earth. It is estimated that this event alone was directly responsible for more than 2,500 new minerals of the total of about 4,500 minerals found on Earth. Most of these new minerals were hydrated, oxidized forms of minerals formed due to dynamic mantle
and crust
processes after the Great Oxygenation event.
Biota
Biota may refer to:* Biota , the plant and animal life of a region* Biota , a superdomain in taxonomy* Biota , an evergreen coniferous tree, Platycladus orientalis* Biota , an avant-prog band from Colorado, USA...
induced appearance of free oxygen (O2) in Earth's atmosphere. This major environmental change happened around 2.4 billion years ago.
Photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
was producing oxygen both before and after the GOE. The difference was that before the GOE, organic matter and dissolved iron chemically captured any free oxygen. The GOE was the point when these minerals became saturated and could not capture any more oxygen. The excess free oxygen started to accumulate in the atmosphere.
The rising oxygen levels may have wiped out a huge portion of the Earth's anaerobic
Anaerobic
Anaerobic is a word which literally means without oxygen, as opposed to aerobic.In wastewater treatment the absence of oxygen is indicated as anoxic; and anaerobic is used to indicate the absence of a common electron acceptor such as nitrate, sulfate or oxygen.Anaerobic may refer to:*Anaerobic...
inhabitants at the time. Cyanobacteria, by producing oxygen, were essentially responsible for what was likely the largest extinction event in Earth's history. Additionally the free oxygen combined with atmospheric methane, triggering the Huronian glaciation, possibly the longest snowball Earth
Snowball Earth
The Snowball Earth hypothesis posits that the Earth's surface became entirely or nearly entirely frozen at least once, some time earlier than 650 Ma . Proponents of the hypothesis argue that it best explains sedimentary deposits generally regarded as of glacial origin at tropical...
episode ever.
The amount of oxygen
Geological history of oxygen
Before photosynthesis evolved, Earth's atmosphere had no free oxygen . Oxygen was first produced by photosynthetic prokaryotic organisms that emitted O2 as a waste product. These organisms lived long before the first build-up of oxygen in the atmosphere, perhaps as early as...
in the atmosphere has fluctuated ever since.
Timing
The most widely accepted chronology of the Great Oxygenation Event suggests that oxygen was first produced by photosynthetic organisms (prokaryotic, then eukaryotic) that emitted oxygen as a waste product. These organisms lived long before the GOE, perhaps as early as . The oxygen they produced would have quickly been removed from the atmosphere by the weathering of reduced minerals, most notably iron. This 'mass rusting' led to the deposition of banded-iron formations, shown for example in sedimentsAnimikie Group
The Animikie Group is a geologic group composed of sedimentary and metasedimentary rock, having been originally deposited between 2,500 and 1,800 million years ago within the Animikie Basin. This group of formations are geographically divided into the Gunflint Range, the Mesabi and Vermilion...
in Minnesota. Oxygen only began to persist in the atmosphere in small quantities shortly (~50 million years) before the start of the GOE. Without a draw-down, oxygen could accumulate very rapidly: for example, at today's rates of photosynthesis (which are admittedly much greater than those in the plant-free Precambrian), modern atmospheric O2 levels could be produced in around 2,000 years.
Another theory is an interpretation of the supposed oxygen indicator, mass-independent fractionation
Mass-independent fractionation
Mass-independent fractionation refers to any chemical or physical process that acts to separate isotopes, where the amount of separation does not scale in proportion with the difference in the masses of the isotopes...
of sulfur isotopes, used in previous studies, and that oxygen producers did not evolve until right before the major rise in atmospheric oxygen concentration. This theory would eliminate the need to explain a lag in time between the evolution of oxyphotosynthetic microbes and the rise in free oxygen.
Either way, the oxygen did eventually accumulate in the atmosphere, with two major consequences. First, it oxidized atmospheric methane (a strong greenhouse gas
Greenhouse gas
A greenhouse gas is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone...
) to carbon dioxide (a weaker one) and water, triggering the Huronian glaciation. The latter may have been a full-blown, and possibly the longest ever, snowball Earth
Snowball Earth
The Snowball Earth hypothesis posits that the Earth's surface became entirely or nearly entirely frozen at least once, some time earlier than 650 Ma . Proponents of the hypothesis argue that it best explains sedimentary deposits generally regarded as of glacial origin at tropical...
episode, lasting 300-400 million years. Second, the increased oxygen levels provided a new opportunity for biological diversification
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
, as well as tremendous changes in the nature of chemical interactions between rocks
Rock (geology)
In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...
, sand
Sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...
, clay
Clay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...
, and other geological substrates and the Earth's air, oceans, and other surface waters. Despite natural recycling of organic matter
Organic matter
Organic matter is matter that has come from a once-living organism; is capable of decay, or the product of decay; or is composed of organic compounds...
, life had remained energetically limited until the widespread availability of oxygen. This breakthrough in metabolic evolution greatly increased the free energy
Thermodynamic free energy
The thermodynamic free energy is the amount of work that a thermodynamic system can perform. The concept is useful in the thermodynamics of chemical or thermal processes in engineering and science. The free energy is the internal energy of a system less the amount of energy that cannot be used to...
supply to living organisms, having a truly global environmental impact; mitochondria evolved after the GOE.
Time lag theory
The lag (which may have been as long as 900 million years) was between the time oxygen production from photosynthetic organisms started and the time of the oxygen catastrophe's geologically rapid increase in atmospheric oxygen (about 2.5–2.4 billion years ago). There are a number of hypotheses to explain this time lag:Tectonic trigger
One phenomenon that explains this lag is that the oxygen increase had to await tectonically driven changes in the Earth's 'anatomy', including the appearance of shelf seas where reduced organic carbon could reach the sediments and be buried. Also, the newly produced oxygen was first consumed in various chemical reactions in the oceans, primarily with ironIron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
. Evidence for this phenomenon is found in older rocks that contain massive banded iron formation
Banded iron formation
Banded iron formations are distinctive units of sedimentary rock that are almost always of Precambrian age. A typical BIF consists of repeated, thin layers of iron oxides, either magnetite or hematite , alternating with bands of iron-poor shale and chert...
s that were apparently laid down as this iron and oxygen first combined; most of the planet's commercial iron ore is in these deposits. But these chemical phenomena do not seem to account for the lag completely.
Nickel famine
Chemosynthetic organisms were a source of methaneMethane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...
, which was also a big trap for molecular oxygen, because oxygen readily oxidizes methane to carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
(CO2) and water in the presence of UV radiation
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
. Modern methanogens require nickel as an enzyme cofactor
Cofactor (biochemistry)
A cofactor is a non-protein chemical compound that is bound to a protein and is required for the protein's biological activity. These proteins are commonly enzymes, and cofactors can be considered "helper molecules" that assist in biochemical transformations....
. As the Earth's crust cooled, the supply of nickel from volcanoes was reduced and less methane was produced allowing oxygen to dominate the atmosphere. From 2.7 to 2.4 billion years ago, the levels of nickel deposited declined steadily; it was originally 400 times today's levels.
Bistability
A 2006 theory, called bistabilityBistability
Bistability is a fundamental phenomenon in nature. Something that is bistable can be resting in either of two states. These rest states need not be symmetric with respect to stored energy...
, to explain the 300-million-year lag comes from a mathematical model of the atmosphere which recognizes that UV shielding decreases the rate of methane oxidation once oxygen levels are sufficient to support the formation of an ozone layer
Ozone layer
The ozone layer is a layer in Earth's atmosphere which contains relatively high concentrations of ozone . This layer absorbs 97–99% of the Sun's high frequency ultraviolet light, which is potentially damaging to the life forms on Earth...
. This explanation proposes a system with two steady state
Steady state
A system in a steady state has numerous properties that are unchanging in time. This implies that for any property p of the system, the partial derivative with respect to time is zero:...
s, one with lower (0.02%) atmospheric oxygen content, and the other with higher (21% or more) oxygen content. The Great Oxidation can then be understood as a switch between lower and upper stable steady states.
Late evolution of oxy-photosynthesis theory
There is a possibility that the oxygen indicator was misinterpreted. During the proposed time of the lag in the previous theory, there was change from mass-independently fractionated (MIF) sulfur to mass-dependently (MDF) fractionated sulfur in sediments. This was assumed to be a result of the appearance of oxygen in the atmosphere (since oxygen would have prevented the photolysisPhotodissociation
Photodissociation, photolysis, or photodecomposition is a chemical reaction in which a chemical compound is broken down by photons. It is defined as the interaction of one or more photons with one target molecule....
of sulfur dioxide, which causes MIF). This change from MIF to MDF of sulfur isotopes also may have been caused by an increase in glacial weathering, or the homogenization of the marine sulfur pool as a result of an increased thermal gradient during the Huronian glaciation period.
Role in mineral diversification
Recent research has shown that the Great Oxygenation Event triggered an explosive growth in the diversity of mineralMineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
s on Earth. It is estimated that this event alone was directly responsible for more than 2,500 new minerals of the total of about 4,500 minerals found on Earth. Most of these new minerals were hydrated, oxidized forms of minerals formed due to dynamic mantle
Mantle (geology)
The mantle is a part of a terrestrial planet or other rocky body large enough to have differentiation by density. The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers. The mantle is a highly viscous layer between the crust and the outer core....
and crust
Crust (geology)
In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle...
processes after the Great Oxygenation event.
See also
- Banded iron formationBanded iron formationBanded iron formations are distinctive units of sedimentary rock that are almost always of Precambrian age. A typical BIF consists of repeated, thin layers of iron oxides, either magnetite or hematite , alternating with bands of iron-poor shale and chert...
- Evolution of dietary antioxidants
- Geological history of oxygenGeological history of oxygenBefore photosynthesis evolved, Earth's atmosphere had no free oxygen . Oxygen was first produced by photosynthetic prokaryotic organisms that emitted O2 as a waste product. These organisms lived long before the first build-up of oxygen in the atmosphere, perhaps as early as...
- IodideIodideAn iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. This page is for the iodide ion and its salts. For information on organoiodides, see organohalides. In everyday life, iodide is most commonly encountered as a component of iodized salt,...
- Medea hypothesisMedea HypothesisThe Medea Hypothesis is a term coined by paleontologist Peter Ward for the anti-Gaian hypothesis that multicellular life, understood as a superorganism, is suicidal; in this view microbial-triggered mass extinctions are attempts to return the Earth to the microbial dominated state it has been for...
- Pasteur pointPasteur pointThe Pasteur point is a level of oxygen above which aerobic microorganisms and facultative anaerobes adapt from anaerobic respiration to aerobic respiration. It is also used to mark the level of oxygen in the early atmosphere of the Earth that is believed to have led to major evolutionary changes...
- Huronian glaciation
External links
- First breath: Earth's billion-year struggle for oxygen New Scientist, #2746, 5 February 2010 by Nick Lane. http://ptc-cam.blogspot.com/2010/02/first-breath-earths-billion-year.html