Editing Biogeochemical cycle (section)

{{Short description|Chemical transfer pathway between Earth's biological and non-biological parts}}
{{biogeochemical cycle sidebar}}

A '''biogeochemical cycle''', or more generally a '''cycle of matter''',<ref>{{Cite web |title=CK12-Foundation |url=https://flexbooks.ck12.org/cbook/ck-12-college-human-biology-flexbook-2.0/section/24.7/primary/lesson/cycles-of-matter-chumbio/ |access-date=2022-03-21 |website=flexbooks.ck12.org}}</ref> is the movement and transformation of chemical elements and compounds between living organisms, the atmosphere, and the Earth's crust. Major biogeochemical cycles include the [[carbon cycle]], the [[nitrogen cycle]] and the [[water cycle]]. In each cycle, the chemical element or molecule is transformed and cycled by living organisms and through various geological forms and reservoirs, including the atmosphere, the soil and the oceans. It can be thought of as the pathway by which a [[chemical substance]] [[Wiktionary:cycle|cycles]] (is turned over or moves through) the [[Biotic components|biotic compartment]] and the [[Abiotic|abiotic compartments]] of [[Earth]]. The biotic compartment is the [[biosphere]] and the abiotic compartments are the [[atmosphere]], [[lithosphere]] and [[hydrosphere]].

For example, in the carbon cycle, atmospheric [[carbon dioxide]] is absorbed by plants through [[photosynthesis]], which converts it into [[organic compound]]s that are used by organisms for energy and growth. [[Carbon]] is then released back into the atmosphere through [[Photorespiration|respiration]] and [[decomposition]]. Additionally, carbon is stored in [[fossil fuel]]s and is released into the atmosphere through human activities such as burning [[fossil fuels]]. In the nitrogen cycle, atmospheric [[nitrogen gas]] is converted by plants into usable forms such as [[ammonia]] and [[nitrate]]s through the process of [[nitrogen fixation]]. These compounds can be used by other organisms, and nitrogen is returned to the atmosphere through [[denitrification]] and other processes. In the water cycle, the [[Water#Properties|universal solvent]] water evaporates from land and oceans to form clouds in the atmosphere, and then [[Precipitation|precipitates]] back to different parts of the planet. Precipitation can [[seep]] into the ground and become part of groundwater systems used by plants and other organisms, or can [[Surface runoff|runoff the surface]] to form lakes and rivers. Subterranean water can then seep into the ocean along with [[river discharge]]s, rich with [[dissolved organic matter|dissolved]] and [[particulate organic matter]] and other nutrients.

There are biogeochemical cycles for many other elements, such as for [[oxygen cycle|oxygen]], [[hydrogen cycle|hydrogen]], [[phosphorus cycle|phosphorus]], [[calcium cycle|calcium]], [[iron cycle|iron]], [[sulfur cycle|sulfur]], [[mercury cycle|mercury]] and [[selenium cycle|selenium]]. There are also cycles for molecules, such as [[water cycle|water]] and [[silica cycle|silica]]. In addition there are macroscopic cycles such as the [[rock cycle]], and human-induced cycles for synthetic compounds such as for [[polychlorinated biphenyl]]s (PCBs). In some cycles there are geological reservoirs where substances can remain or be [[:Wiktionary:sequestered|sequestered]] for long periods of time.

Biogeochemical cycles involve the interaction of biological, geological, and chemical processes. Biological processes include the influence of [[microorganism]]s, which are critical drivers of biogeochemical cycling. Microorganisms have the ability to carry out wide ranges of [[metabolic process]]es essential for the cycling of nutrients ([[Nutrient|macronutrients]] and [[Micronutrient|micronutrients]]) and chemicals throughout global ecosystems. Without microorganisms many of these processes would not occur, with significant impact on the functioning of land and ocean ecosystems and the planet's biogeochemical cycles as a whole. Changes to cycles can impact human health. The cycles are interconnected and play important roles regulating climate, supporting the growth of [[plant]]s, [[phytoplankton]] and other organisms, and maintaining the health of ecosystems generally. Human activities such as burning fossil fuels and using large amounts of fertilizer can disrupt cycles, contributing to climate change, pollution, and other environmental problems.
{{TOC limit|2}}