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=== Terrestrial runoff to the ocean ===
[[File:Terrestrial carbon escaping from inland waters.jpg|thumb|upright=2| {{center|'''How carbon moves from inland waters to the ocean'''}} Carbon dioxide exchange, photosynthetic production and respiration of terrestrial vegetation, rock weathering, and sedimentation occur in terrestrial ecosystems. Carbon transports to the ocean through the land-river-estuary continuum in the form of organic carbon and inorganic carbon. Carbon exchange at the air-water interface, transportation, transformation and sedimentation occur in oceanic ecosystems..<ref name="Gao2022">{{cite journal |
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=== Carbon in the core ===
Although the presence of carbon in the Earth's core is well-constrained, recent studies suggest large inventories of carbon could be stored in this region.{{Clarify|reason=confusing sentence for non-scientists|date=November 2020}} [[S-wave|Shear (S) waves]] moving through the inner core travel at about fifty percent of the velocity expected for most iron-rich alloys.<ref>{{Cite web|url=https://deepcarbon.net/feature/does-earths-core-host-deep-carbon-reservoir|title=Does Earth's Core Host a Deep Carbon Reservoir? |website=Deep Carbon Observatory |access-date=2019-03-09|archive-date=27 July 2020|archive-url=https://web.archive.org/web/20200727092747/https://deepcarbon.net/feature/does-earths-core-host-deep-carbon-reservoir|url-status=dead}}{{rs|date=July 2024}}</ref> Because the core's composition is believed to be an alloy of crystalline iron and a small amount of nickel, this seismic anomaly indicates the presence of light elements, including carbon, in the core. In fact, studies using [[diamond anvil cell]]s to replicate the conditions in the Earth's core indicate that [[Cementite|iron carbide]] (Fe<sub>7</sub>C<sub>3</sub>) matches the inner core's wave speed and density. Therefore, the iron carbide model could serve as an evidence that the core holds as much as 67% of the Earth's carbon.<ref>{{cite journal |last1=Chen |first1=Bin |last2=Li |first2=Zeyu |last3=Zhang |first3=Dongzhou |last4=Liu |first4=Jiachao |last5=Hu |first5=Michael Y. |last6=Zhao |first6=Jiyong |last7=Bi |first7=Wenli |last8=Alp |first8=E. Ercan |last9=Xiao |first9=Yuming |last10=Chow |first10=Paul |last11=Li |first11=Jie |title=Hidden carbon in Earth's inner core revealed by shear softening in dense {{chem|Fe|7|C|3}} |journal=Proceedings of the National Academy of Sciences |date=16 December 2014 |volume=111 |issue=50 |pages=17755–17758 |doi=10.1073/pnas.1411154111 |pmid=25453077 |pmc=4273394 |bibcode=2014PNAS..11117755C |doi-access=free }}</ref> Furthermore, another study found that in the pressure and temperature condition of the Earth's inner core, carbon dissolved in iron and formed a stable phase with the same Fe<sub>7</sub>C<sub>3</sub> composition—albeit with a different structure from the one previously mentioned.<ref>{{cite journal |last1=Prescher |first1=C. |last2=Dubrovinsky |first2=L. |last3=Bykova |first3=E. |last4=Kupenko |first4=I. |last5=Glazyrin |first5=K. |last6=Kantor |first6=A. |last7=McCammon |first7=C. |last8=Mookherjee |first8=M. |last9=Nakajima |first9=Y. |last10=Miyajima |first10=N. |last11=Sinmyo |first11=R. |last12=Cerantola |first12=V. |last13=Dubrovinskaia |first13=N. |last14=Prakapenka |first14=V. |last15=Rüffer |first15=R. |last16=Chumakov |first16=A. |last17=Hanfland |first17=M. |title=High Poisson's ratio of Earth's inner core explained by carbon alloying |journal=Nature Geoscience |date=March 2015 |volume=8 |issue=3 |pages=220–223 |doi=10.1038/ngeo2370 |bibcode=2015NatGe...8..220P }}</ref> In summary, although the amount of carbon potentially stored in the Earth's core is not known, recent studies indicate that the presence of iron carbides can explain some of the geophysical observations.<ref>{{
==Viruses as regulators==
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