Geological history of oxygen

<h2 id="before-the-great-oxidation-event">Before the Great Oxidation Event</h2>
Main article: <a href="/facts/Prebiotic_atmosphere/HqbMkAza">Prebiotic atmosphere</a>
<a href="/facts/Photosynthetic/TMV7w693">Photosynthetic</a> <a href="/facts/Prokaryotic/oYyvaDDH">prokaryotic</a> <a href="/facts/Organism/j8JkL09u">organisms</a> that produced O2 as a <a href="/facts/Byproduct/qDosnqoD">byproduct</a> lived long before the first build-up of free oxygen in the atmosphere,<a class="footnote-ref" id="fnref:4" href="#fn:4">4</a> perhaps as early as 3.5 billion years ago. The oxygen <a href="/facts/Cyanobacteria/S8bKxIU9">cyanobacteria</a> produced would have been rapidly removed from the oceans by weathering of reducing minerals, most notably <a href="/facts/Ferrous_iron/TCxvdjfW">ferrous iron</a>.<a class="footnote-ref" id="fnref:5" href="#fn:5">5</a> This rusting led to the deposition of the <a href="/facts/Oxidize/Pyd5RVcj">oxidized</a> <a href="/facts/Ferric/TMrSskIt">ferric</a> <a href="/facts/Iron_oxide/KDo8hLWn">iron oxide</a> on the ocean floor, forming <a href="/facts/Banded_iron_formations/b1eA2yAk">banded iron formations</a>. Thus, the oceans rusted and turned red. Oxygen only began to persist in the atmosphere in small quantities about 50 million years before the start of the <a href="/facts/Great_Oxygenation_Event/LmTyM8jT">Great Oxygenation Event</a>.<a class="footnote-ref" id="fnref:6" href="#fn:6">6</a>

<h2 id="effects-on-life">Effects on life</h2>

Further information: <a href="/facts/Symbiogenesis/2gHlgj4j">Symbiogenesis</a>
Early fluctuations in oxygen concentration had little direct effect on life, with <a href="/facts/Mass_extinction/HloJubtR">mass extinctions</a> not observed until around the start of the <a href="/facts/Cambrian/jIfzKtod">Cambrian</a> period, <a href="https://geoltime.github.io/?Ma=538.8">538.8</a> million years ago.<a class="footnote-ref" id="fnref:7" href="#fn:7">7</a> The presence of O2 provided life with new opportunities. Aerobic metabolism is more efficient than anaerobic pathways, and the presence of oxygen created new possibilities for life to explore.<a class="footnote-ref" id="fnref:8" href="#fn:8">8</a><a class="footnote-ref" id="fnref:9" href="#fn:9">9</a> Since the start of the <a href="/facts/Cambrian/jIfzKtod">Cambrian</a> period, atmospheric oxygen concentrations have fluctuated between 15% and 35% of atmospheric volume.<a class="footnote-ref" id="fnref:10" href="#fn:10">10</a> 430-million-year-old fossilized charcoal produced by wildfires show that the atmospheric oxygen levels in the Silurian must have been equivalent to, or possibly above, present day levels.<a class="footnote-ref" id="fnref:11" href="#fn:11">11</a> The maximum of 35% was reached towards the end of the <a href="/facts/Carboniferous/BRKlkYyd">Carboniferous</a> period (about 300 million years ago), a peak which may have contributed to the large size of various <a href="/facts/Arthropods/JKJLTFzp">arthropods</a>, including insects, millipedes and scorpions.<a class="footnote-ref" id="fnref:12" href="#fn:12">12</a> Whilst human activities, such as the burning of <a href="/facts/Fossil_fuel/BPgxAqB7">fossil fuels</a>, affect relative carbon dioxide concentrations, their effect on the much larger concentration of oxygen is less significant.<a class="footnote-ref" id="fnref:13" href="#fn:13">13</a>
The <a href="/facts/Great_Oxygenation_Event/LmTyM8jT">Great Oxygenation Event</a> had the first major effect on the course of <a href="/facts/Evolution/Hj0qAaBk">evolution</a>. Due to the rapid buildup of oxygen in the atmosphere, the mostly <a href="/facts/Anaerobe/bhQnlqCq">anaerobic</a> <a href="/facts/Microbial/pysJYcE2">microbial</a> <a href="/facts/Biosphere/P1ltA4sb">biosphere</a> that existed during the <a href="/facts/Archean_eon/PHt8Sm8n">Archean eon</a> was devastated, and only the <a href="/facts/Aerobe/a629EQD7">aerobes</a> that had <a href="/facts/Antioxidant/4TG4MQ83">antioxidant</a> capabilities to neutralize oxygen thrived out in the open.<a class="footnote-ref" id="fnref:14" href="#fn:14">14</a> This then led to <a href="/facts/Symbiosis/MrBArRGa">symbiosis</a> of anaerobic and aerobic organisms, who metabolically complemented each other, and eventually led to <a href="/facts/Endosymbiosis/eWvSS8ID">endosymbiosis</a> and the evolution of <a href="/facts/Eukaryote/SkwyPLMA">eukaryotes</a> during the <a href="/facts/Proterozoic_eon/sSGXxqUU">Proterozoic eon</a>, who were now actually reliant on <a href="/facts/Aerobic_respiration/kb6gpsvL">aerobic respiration</a> to survive. After the <a href="/facts/Huronian_glaciation/SxGpeQ1p">Huronian glaciation</a> came to an end, the Earth entered a long period of geological and climatic stability known as the <a href="/facts/Boring_Billion/k7VDsVpu">Boring Billion</a>. However, this long period was noticeably <a href="/facts/Euxinic/YIGE4GSS">euxinic</a>, meaning oxygen was scarce and the ocean and atmosphere were significantly <a href="/facts/Sulfidic/uTqH9R9P">sulfidic</a>, and that evolution then was likely comparatively slow and quite conservative.
The Boring Billion ended during the <a href="/facts/Neoproterozoic_period/89NsnsM1">Neoproterozoic period</a> with a significant increase in photosynthetic activities, causing oxygen levels to rise 10- to 20-fold to about one-tenth of the modern level. This rise in oxygen concentration, known as the <a href="/facts/Neoproterozoic_oxygenation_event/St3FvUDf">Neoproterozoic oxygenation event</a> or "Second Great Oxygenation Event", was likely caused by the evolution of <a href="/facts/Nitrogen_fixation/TeLoBpWS">nitrogen fixation</a> in <a href="/facts/Cyanobacteria/S8bKxIU9">cyanobacteria</a> and the rise of eukaryotic photoautotrophs (<a href="/facts/Green_algae/3NlQ6pKF">green</a> and <a href="/facts/Red_algae/jCeIc7Kq">red algae</a>), and often cited as a possible contributor to later large-scale <a href="/facts/Evolutionary_radiation/DDc0R6GS">evolutionary radiations</a> such as the <a href="/facts/Avalon_explosion/YCLcTMsW">Avalon explosion</a> and the <a href="/facts/Cambrian_explosion/Wg29M7PN">Cambrian explosion</a>, which not only trended in larger<a class="footnote-ref" id="fnref:15" href="#fn:15">15</a> but also more robust and <a href="/facts/Motile/Df5BECHL">motile</a> <a href="/facts/Multicellular_organism/rk8QBF7o">multicellular organisms</a>. The climatic changes associated with rising oxygen also produced cycles of <a href="/facts/Glaciation/alIAm38r">glaciation</a> and <a href="/facts/Extinction_event/HloJubtR">extinction events</a>,<a class="footnote-ref" id="fnref:16" href="#fn:16">16</a> each of which created <a href="/facts/Disturbance_(ecology)/0y85hFeB">disturbances</a> that sped up <a href="/facts/Ecological_succession/4LbHrU2s">ecological turnovers</a>. During the <a href="/facts/Silurian/1qx4epPg">Silurian</a> and <a href="/facts/Devonian/nWgakqzk">Devonian</a> periods, the <a href="/facts/Silurian-Devonian_Terrestrial_Revolution/9j04Jlmv">colonization and proliferation on land</a> by early <a href="/facts/Plant/X5BMDMvS">plants</a> (which evolved from freshwater green algae) further increased the atmospheric oxygen concentration, leading to the historic peak during the Carboniferous period.
Data show an increase in biovolume soon after oxygenation events by more than 100-fold and a moderate correlation between atmospheric oxygen and maximum body size later in the geological record.<a class="footnote-ref" id="fnref:17" href="#fn:17">17</a> The large size of many arthropods in the <a href="/facts/Carboniferous_period/BRKlkYyd">Carboniferous period</a>, when the oxygen concentration in the atmosphere reached 35%, has been attributed to the limiting role of diffusion in these organisms' metabolism.<a class="footnote-ref" id="fnref:18" href="#fn:18">18</a> But <a href="/facts/J.B.S._Haldane/sywPNzfh">J.B.S. Haldane</a>'s essay <a href="/facts/On_Being_the_Right_Size/xtthLCcE">On Being the Right Size</a><a class="footnote-ref" id="fnref:19" href="#fn:19">19</a> points out that it would only apply to insects. However, the biological basis for this correlation is not firm, and many lines of evidence show that oxygen concentration is not size-limiting in modern insects.<a class="footnote-ref" id="fnref:20" href="#fn:20">20</a> Ecological constraints can better explain the diminutive size of post-Carboniferous dragonflies – for instance, the appearance of flying competitors such as <a href="/facts/Pterosaur/YNQwa1ru">pterosaurs</a>, birds, and bats.<a class="footnote-ref" id="fnref:21" href="#fn:21">21</a> 
Rising oxygen concentrations have been cited as one of several drivers for evolutionary diversification, although the physiological arguments behind such arguments are questionable, and a consistent pattern between oxygen concentrations and the rate of evolution is not clearly evident.<a class="footnote-ref" id="fnref:22" href="#fn:22">22</a> The most celebrated link between oxygen and evolution occurred at the end of the last of the <a href="/facts/Snowball_Earth/A9yP3khz">Snowball Earth</a> glaciations, where complex multicellular life is first found in the fossil record. Under low oxygen concentrations and before the evolution of <a href="/facts/Nitrogen_fixation/TeLoBpWS">nitrogen fixation</a>, biologically-available nitrogen compounds were in limited supply,<a class="footnote-ref" id="fnref:23" href="#fn:23">23</a> and periodic "nitrogen crises" could render the ocean inhospitable to life.<a class="footnote-ref" id="fnref:24" href="#fn:24">24</a> Significant concentrations of oxygen were just one of the prerequisites for the evolution of complex life.<a class="footnote-ref" id="fnref:25" href="#fn:25">25</a> Models based on uniformitarian principles (i.e. extrapolating present-day ocean dynamics into deep time) suggest that such a concentration was only reached immediately before <a href="/facts/Metazoa/4b8J33nd">metazoa</a> first appeared in the fossil record.<a class="footnote-ref" id="fnref:26" href="#fn:26">26</a> Further, anoxic or otherwise chemically "inhospitable" oceanic conditions that resemble those supposed to inhibit macroscopic life re-occurred at intervals through the early Cambrian, and also in the late Cretaceous – with no apparent effect on lifeforms at these times.<a class="footnote-ref" id="fnref:27" href="#fn:27">27</a> This might suggest that the geochemical signatures found in ocean sediments reflect the atmosphere in a different way before the Cambrian – perhaps as a result of the fundamentally different mode of <a href="/facts/Nutrient_cycling/S57nuGbQ">nutrient cycling</a> in the absence of planktivory.<a class="footnote-ref" id="fnref:28" href="#fn:28">28</a><a class="footnote-ref" id="fnref:29" href="#fn:29">29</a>
An oxygen-rich atmosphere can release phosphorus and iron from rock, by weathering, and these elements then become available for sustenance of new species whose metabolisms require these elements as oxides.<a class="footnote-ref" id="fnref:30" href="#fn:30">30</a>

<h2 id="nutrient-cycling-changes-as-oxygen-levels-rose">Nutrient Cycling Changes as Oxygen Levels Rose</h2>
The coupling between oxygen levels and nutrient cycling has been a critical factor in shaping Earth's biosphere. Oxygen plays a central role in the oxidation of minerals during weathering. Weathering of the contienents which releases nutrients such as phosphorus and iron into rivers and oceans. Phosphorus, is an essential element for ATP, DNA, and membranes. This makes its bioavailability a limiting factor for primary productivity of ecosystems. When oxygen levels increase, weathering rates are also seen to rise. Which likely expand the nutrient base of marine ecosystems. As a result, this enables higher production and supports more complex food webs. In marine environments, oxygen also regulates the redox cycling of nitrogen. In anoxic conditions, denitrification processes dominate, which convert bioavailable nitrogen (nitrate and ammonium) back into inert N₂ gas. This removes it from the biosphere. As oxygen concentrations rose, nitrification became more prevalent, converting ammonia into nitrate and nitrite, more stable and accessible forms for primary producers. This shift helped stabilize nitrogen availability, which can limit biological expansion if depleted.
The emergence of planktivory, microorganisms feeding on plankton, was another historic turning point in nutrient cycling. Prior to the evolution of complex grazing organisms, nutrient regeneration occurred mainly through microbial remineralization, which was a much slower process. With the rise of planktivores and active predation in the water column during the Cambrian, nutrient cycling accelerated and became more efficient. The led to tighter biological feedback loops and higher rates of primary production. In addition, the shift toward higher rates of primariy production is inferred to have influenced isotopic signatures in marines sediments.The co-evolution of oxygenation and nutrient cycling created a feedback system that enabled both the expansion of biomass and the diversification of life. Rising oxygen not only enabled more complex metabolisms but also transformed the nutrient landscape. The relationship was not coalescent, however. Many disruptions, such as climate shifts, caused a temporary deconstruction of the nutrient-oxygen dynamic in marine systems. 

Disruptions led to eriods of environmental instability, such as during Snowball Earth events. The Late Devonian, or Ocean Anoxic Events demonstrate how fragile the oxygen-nutrient balance can be. During these intervals, rapid climate change or massive volcanic activity altered ocean circulation and chemistry. This caused widespread deoxygenation and led to declines in biodiversity and primary productivity. Widespread oxygention from sudden shifts in global climate caused key nutrients to become locked in sediments or lost within inefficient nutrient recycling. These periods demonstrate that while oxygenation was essential to biological expansion, it also made the biosphere more sensitive to disruption. The resilience of nutrient cycling systems, particularly through microbial buffering and evolving trophic interactions, helped restore the oxygentation of the global climate. Over time, this restored nutrient cycling and was able to increase levels of biodiversity again.
<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Great_Oxidation_Event/LmTyM8jT">Great Oxidation Event</a></li>
<li><a href="/facts/Neoproterozoic_oxygenation_event/St3FvUDf">Neoproterozoic oxygenation event</a></li>
<li><a href="/facts/Silurian-Devonian_Terrestrial_Revolution/9j04Jlmv">Silurian-Devonian Terrestrial Revolution</a></li></ul>

<h2 id="external-links">External links</h2>
<ul><li>Lane, Nick (5 February 2010). <a href="https://www.newscientist.com/article/mg20527461.100-first-breath-earths-billionyear-struggle-for-oxygen.html">"First breath: Earth's billion-year struggle for oxygen"</a>. New Scientist. No. 2746.(subscription required)</li>
<li>Zimmer, Carl (3 October 2013). <a href="https://www.nytimes.com/2013/10/03/science/earths-oxygen-a-mystery-easy-to-take-for-granted.html?_r=0&pagewanted=print">"The mystery of Earth's oxygen"</a>. <a href="/facts/The_New_York_Times/T9marWVX">The New York Times</a>.</li>
<li>Ward, Peter D. (2006). Out of Thin Air; dinosaurs, birds, and Earth's ancient atmosphere. Joseph Henry Press. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 0-309-10061-5.; <a href="https://www.newscientist.com/article/mg19225780-124-review-out-of-thin-air-by-peter-ward/">"Review of Out of Thin Air by Peter Ward"</a>. New Scientist.</li></ul>

<h2 id="references">References</h2>

<ol>
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<li id="fn:2">Stone, Jordan; Edgar, John O.; Gould, Jamie A.; Telling, Jon (2022-08-08). "Tectonically-driven oxidant production in the hot biosphere". Nature Communications. 13 (1): 4529. Bibcode:2022NatCo..13.4529S. doi:10.1038/s41467-022-32129-y. ISSN 2041-1723. PMC 9360021. PMID 35941147. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9360021" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9360021</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></li>
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<li id="fn:11">Earliest record of wildfires provides insights into Earth's past vegetation and oxygen levels <a href="https://phys.org/news/2022-06-earliest-wildfires-insights-earth-vegetation.html" target="_blank">https://phys.org/news/2022-06-earliest-wildfires-insights-earth-vegetation.html</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></li>
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<li id="fn:19">Haldane, J.B.S., On being the right size, paragraph 7 <a href="#fnref:19" class="footnote-back-ref">↩</a></li>
<li id="fn:20">Butterfield, N. J. (2009). "Oxygen, animals and oceanic ventilation: An alternative view". Geobiology. 7 (1): 1–7. Bibcode:2009Gbio....7....1B. doi:10.1111/j.1472-4669.2009.00188.x. PMID 19200141. S2CID 31074331. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:20" class="footnote-back-ref">↩</a></li>
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<li id="fn:24">Butterfield, N. J. (2009). "Oxygen, animals and oceanic ventilation: An alternative view". Geobiology. 7 (1): 1–7. Bibcode:2009Gbio....7....1B. doi:10.1111/j.1472-4669.2009.00188.x. PMID 19200141. S2CID 31074331. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:24" class="footnote-back-ref">↩</a></li>
<li id="fn:25">Butterfield, N. J. (2009). "Oxygen, animals and oceanic ventilation: An alternative view". Geobiology. 7 (1): 1–7. Bibcode:2009Gbio....7....1B. doi:10.1111/j.1472-4669.2009.00188.x. PMID 19200141. S2CID 31074331. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:25" class="footnote-back-ref">↩</a></li>
<li id="fn:26">Butterfield, N. J. (2009). "Oxygen, animals and oceanic ventilation: An alternative view". Geobiology. 7 (1): 1–7. Bibcode:2009Gbio....7....1B. doi:10.1111/j.1472-4669.2009.00188.x. PMID 19200141. S2CID 31074331. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:26" class="footnote-back-ref">↩</a></li>
<li id="fn:27">Butterfield, N. J. (2009). "Oxygen, animals and oceanic ventilation: An alternative view". Geobiology. 7 (1): 1–7. Bibcode:2009Gbio....7....1B. doi:10.1111/j.1472-4669.2009.00188.x. PMID 19200141. S2CID 31074331. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:27" class="footnote-back-ref">↩</a></li>
<li id="fn:28">Butterfield, N. J. (2007). "Macroevolution and macroecology through deep time". Palaeontology. 50 (1): 41–55. Bibcode:2007Palgy..50...41B. doi:10.1111/j.1475-4983.2006.00613.x. S2CID 59436643. <a href="https://doi.org/10.1111%2Fj.1475-4983.2006.00613.x" target="_blank">https://doi.org/10.1111%2Fj.1475-4983.2006.00613.x</a> <a href="#fnref:28" class="footnote-back-ref">↩</a></li>
<li id="fn:29">Butterfield, N. J. (2009). "Oxygen, animals and oceanic ventilation: An alternative view". Geobiology. 7 (1): 1–7. Bibcode:2009Gbio....7....1B. doi:10.1111/j.1472-4669.2009.00188.x. PMID 19200141. S2CID 31074331. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:29" class="footnote-back-ref">↩</a></li>
<li id="fn:30">Zimmer, Carl (3 October 2013). "Earth's Oxygen: A Mystery Easy to Take for Granted". New York Times. Retrieved 3 October 2013. <a href="/wiki/Carl_Zimmer" target="_blank">/wiki/Carl_Zimmer</a> <a href="#fnref:30" class="footnote-back-ref">↩</a></li>
</ol>

Geological history of oxygen open-in-new

Geological history of oxygen