Editing Biogeochemical cycle (section)

==Overview==
[[File:Generalized biogeochemical cycle.jpg|thumb|upright=1.2| Generalized biogeochemical cycle<ref name=Moses2012 />]]
[[File:The Nitrogen Cycle (1).png|thumb|upright=1.2| Simplified version of the nitrogen cycle]]

Energy flows directionally through ecosystems, entering as sunlight (or inorganic molecules for [[chemoautotroph]]s) and leaving as heat during the many transfers between [[trophic level]]s. However, the matter that makes up living organisms is conserved and recycled. The six most common elements associated with organic molecules — carbon, nitrogen, hydrogen, oxygen, phosphorus, and sulfur — take a variety of chemical forms and may exist for long periods in the atmosphere, on land, in water, or beneath the Earth's surface. Geologic processes, such as [[weathering]], [[erosion]], [[water drainage]], and the [[subduction]] of the [[continental plate]]s, all play a role in this recycling of materials. Because [[geology]] and [[chemistry]] have major roles in the study of this process, the recycling of inorganic matter between living organisms and their environment is called a biogeochemical cycle.<ref name=OpenStax>[https://cnx.org/contents/ZdFkREJc@7/Biogeochemical-Cycles Biogeochemical Cycles] {{Webarchive|url=https://web.archive.org/web/20210927040316/https://cnx.org/contents/ZdFkREJc@7/Biogeochemical-Cycles |date=2021-09-27 }}, ''OpenStax'', 9 May 2019. [[File:CC-BY icon.svg|50px]] Material was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License] {{Webarchive|url=https://web.archive.org/web/20171016050101/https://creativecommons.org/licenses/by/4.0/ |date=2017-10-16 }}.</ref>

The six aforementioned elements are used by organisms in a variety of ways. Hydrogen and oxygen are found in water and [[organic molecule]]s, both of which are essential to life. Carbon is found in all organic molecules, whereas nitrogen is an important component of [[nucleic acid]]s and [[protein]]s. Phosphorus is used to make nucleic acids and the [[phospholipid]]s that comprise [[biological membrane]]s. Sulfur is critical to the three-dimensional shape of proteins. The cycling of these elements is interconnected. For example, the movement of water is critical for leaching sulfur and phosphorus into rivers which can then flow into oceans. Minerals cycle through the biosphere between the biotic and abiotic components and from one organism to another.<ref name=Fisher2019>Fisher M. R. (Ed.) (2019) ''Environmental Biology'', [https://openoregon.pressbooks.pub/envirobiology/chapter/3-2-biogeochemical-cycles/ 3.2 Biogeochemical Cycles] {{Webarchive|url=https://web.archive.org/web/20210927040314/https://openoregon.pressbooks.pub/envirobiology/chapter/3-2-biogeochemical-cycles/ |date=2021-09-27 }}, OpenStax. [[File:CC-BY icon.svg|50px]] Material was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License] {{Webarchive|url=https://web.archive.org/web/20171016050101/https://creativecommons.org/licenses/by/4.0/ |date=2017-10-16 }}.</ref>

Ecological systems ([[ecosystem]]s) have many biogeochemical cycles operating as a part of the system, for example, the water cycle, the carbon cycle, the nitrogen cycle, etc. All chemical elements occurring in organisms are part of biogeochemical cycles. In addition to being a part of living organisms, these chemical elements also cycle through abiotic factors of ecosystems such as water ([[hydrosphere]]), land ([[lithosphere]]), and/or the air ([[atmosphere]]).<ref name="enviroliteracy.org">{{cite web|title=Biogeochemical Cycles|url=http://www.enviroliteracy.org/subcategory.php/198.html|publisher=The Environmental Literacy Council|access-date=20 November 2017|archive-date=30 April 2015|archive-url=https://web.archive.org/web/20150430133927/http://enviroliteracy.org/subcategory.php/198.html|url-status=live}}</ref>

The living factors of the planet can be referred to collectively as the [[biosphere]]. All the nutrients — such as [[carbon]], [[nitrogen]], [[oxygen]], [[phosphorus]], and [[sulfur]] — used in ecosystems by living organisms are a part of a ''closed system''; therefore, these chemicals are recycled instead of being lost and replenished constantly such as in an open system.<ref name="enviroliteracy.org"/>

The major parts of the biosphere are connected by the flow of chemical elements and compounds in biogeochemical cycles. In many of these cycles, the [[biota (ecology)|biota]] plays an important role. Matter from the Earth's interior is released by volcanoes. The atmosphere exchanges some compounds and elements rapidly with the biota and oceans. Exchanges of materials between rocks, soils, and the oceans are generally slower by comparison.<ref name=Moses2012>Moses, M. (2012) [http://editors.eol.org/eoearth/wiki/biogeochemical_cycles Biogeochemical cycles] {{Webarchive|url=https://web.archive.org/web/20211122221017/https://editors.eol.org/eoearth/wiki/Biogeochemical_cycles |date=2021-11-22 }}. ''[[Encyclopedia of Earth]]''.</ref>

The flow of energy in an ecosystem is an ''open system''; the Sun constantly gives the planet energy in the form of light while it is eventually used and lost in the form of heat throughout the [[trophic level]]s of a food web.  Carbon is used to make carbohydrates, fats, and proteins, the major sources of [[food energy]].  These compounds are oxidized to release carbon dioxide, which can be captured by plants to make organic compounds.  The [[chemical reaction]] is powered by the light energy of sunshine.

Sunlight is required to combine carbon with hydrogen and oxygen into an energy source, but ecosystems in the [[deep sea]], where no sunlight can penetrate, obtain energy from sulfur. [[Hydrogen sulfide]] near [[hydrothermal vent]]s can be utilized by organisms such as the [[giant tube worm]].  In the [[sulfur cycle]], sulfur can be forever recycled as a source of energy.  Energy can be released through the [[oxidation]] and [[redox|reduction]] of sulfur compounds (e.g., oxidizing elemental sulfur to [[sulfite]] and then to [[sulfate]]).

<gallery mode="packed" heights="170px">
File:BIOGEOCHEMICAL CYCLING OF ELEMENTS.svg| Examples of major biogeochemical processes
File:WhalePump.jpg|The oceanic [[whale pump]] showing how whales cycle nutrients through the ocean [[water column]]
File:Global carbon cycle.webp|The implications of shifts in the [[global carbon cycle]] due to human activity are concerning scientists.<ref>Avelar, S., van der Voort, T.S. and Eglinton, T.I. (2017) "Relevance of carbon stocks of marine sediments for national greenhouse gas inventories of maritime nations". ''Carbon balance and management'', '''12'''(1): 10.{{doi|10.1186/s13021-017-0077-x}}. [[File:CC-BY icon.svg|50px]] Material was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License]. {{Webarchive|url=https://web.archive.org/web/20171016050101/https://creativecommons.org/licenses/by/4.0/ |date=2017-10-16 }}.</ref>
</gallery>

Although the Earth constantly receives energy from the Sun, its chemical composition is essentially fixed, as the additional matter is only occasionally added by meteorites. Because this chemical composition is not replenished like energy, all processes that depend on these chemicals must be recycled. These cycles include both the living biosphere and the nonliving [[lithosphere]], [[atmosphere]], and [[hydrosphere]].

Biogeochemical cycles can be contrasted with [[geochemical cycle]]s. The latter deals only with [[Earth's crust|crustal]] and subcrustal reservoirs even though some process from both overlap.