Iron Cycle

The iron cycle is the biogeochemical cycle through which iron moves among Earth atmosphere, hydrosphere, biosphere, and lithosphere. Although iron is one of the most abundant elements in the crust, it is relatively scarce in oxygenated surface waters, and as an essential micronutrient it limits primary productivity in specific ocean regions known as High Nutrient, Low Chlorophyll areas, including the Southern Ocean and parts of the Pacific. On Earth iron occurs mainly in the plus two or plus three oxidation state, and the cycle proper is the conversion between these states, whether through abiotic processes such as rusting or through the activity of iron oxidizing bacteria. Iron is essential to life as a component of hemoglobin and as a participant in nitrogen fixation and cellular electron transport, and because ferrous iron reacts readily with oxygen while ferric iron is poorly soluble, its availability limits productivity across much of the globe. Human activity, chiefly industrial emissions and combustion, has roughly doubled the concentration of soluble iron in the oceans compared with pre-industrial levels. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/