page_title: Iron cycle
hierarchical_section_title: Iron cycle
caption_attribution_description: English: Diagram of the biogeochemical iron cycle showing reservoirs and fluxes
context_page_description: The iron cycle is the biogeochemical cycle of iron through the atmosphere, hydrosphere, biosphere and lithosphere. While Fe is highly abundant in the Earth's crust, it is less common in oxygenated surface waters. Iron is a key micronutrient in primary productivity, and a limiting nutrient in the Southern ocean, eastern equatorial Pacific, and the subarctic Pacific referred to as High-Nutrient, Low-Chlorophyll regions of the ocean.
  Iron exists in a range of oxidation states from -2 to +7; however, on Earth it is predominantly in its +2 or +3 redox state and is a primary redox-active metal on Earth. The cycling of iron between its +2 and +3 oxidation states is referred to as the iron cycle. This process can be entirely abiotic or facilitated by microorganisms, especially iron-oxidizing bacteria. The abiotic processes include the rusting of iron-bearing metals, where Fe²⁺ is abiotically oxidized to Fe³⁺ in the presence of oxygen, and the reduction of Fe³⁺ to Fe²⁺ by iron-sulfide minerals. The biological cycling of Fe²⁺ is done by iron oxidizing and reducing microbes.
  Iron is an essential micronutrient for almost every life form.
context_section_description: The iron cycle (Fe) is the biogeochemical cycle of iron through the atmosphere, hydrosphere, biosphere and lithosphere. While Fe is highly abundant in the Earth's crust, it is less common in oxygenated surface waters. Iron is a key micronutrient in primary productivity, and a limiting nutrient in the Southern ocean, eastern equatorial Pacific, and the subarctic Pacific referred to as High-Nutrient, Low-Chlorophyll (HNLC) regions of the ocean.
  Iron exists in a range of oxidation states from -2 to +7; however, on Earth it is predominantly in its +2 or +3 redox state and is a primary redox-active metal on Earth. The cycling of iron between its +2 and +3 oxidation states is referred to as the iron cycle. This process can be entirely abiotic or facilitated by microorganisms, especially iron-oxidizing bacteria. The abiotic processes include the rusting of iron-bearing metals, where Fe²⁺ is abiotically oxidized to Fe³⁺  in the presence of oxygen, and the reduction of Fe³⁺ to Fe²⁺ by iron-sulfide minerals. The biological cycling of Fe²⁺ is done by iron oxidizing and reducing microbes.
  Iron is an essential micronutrient for almost every life form. It is a key component of hemoglobin, important to nitrogen fixation as part of the Nitrogenase enzyme family, and as part of the iron-sulfur core of ferredoxin it facilitates electron transport in chloroplasts, eukaryotic mitochondria, and bacteria. Due to the high reactivity of Fe²⁺ with oxygen and low solubility of Fe³⁺, iron is a limiting nutrient in most regions of the world.
caption: Biogeochemical iron cycle: Iron circulates through the atmosphere, lithosphere, and oceans. Labeled arrows show flux in Tg of iron per year.[1][2][3][4] Iron in the ocean cycles between plankton, aggregated particulates (non-bioavailable iron), and dissolved (bioavailable iron), and becomes sediments through burial.[1][5][6] Hydrothermal vents release ferrous iron to the ocean[7] in addition to oceanic iron inputs from land sources. Iron reaches the atmosphere through volcanism,[8] aeolian wind,[9] and some via combustion by humans. In the Anthropocene, iron is removed from mines in the crust and a portion re-deposited in waste repositories.[4][6]
exif: {}