Editing Iron (section)

===Marine systems===
Iron plays an essential role in marine systems and can act as a limiting nutrient for planktonic activity.<ref>{{cite journal | last1 = Morel | first1 = F.M.M. | last2 = Hudson | first2 = R.J.M. | last3 = Price | first3 = N.M. | year = 1991 | title = Limitation of productivity by trace metals in the sea | url = | journal = Limnology and Oceanography | volume = 36 | issue = 8| pages = 1742–1755 | doi = 10.4319/lo.1991.36.8.1742 | bibcode = 1991LimOc..36.1742M }}</ref> Because of this, too much of a decrease in iron may lead to a decrease in growth rates in phytoplanktonic organisms such as diatoms.<ref>{{cite journal | last1 = Brezezinski | first1 = M.A. | last2 = Baines | first2 = S.B. | last3 = Balch | first3 = W.M. | last4 = Beucher | first4 = C.P. | last5 = Chai | first5 = F. | last6 = Dugdale | first6 = R.C. | last7 = Krause | first7 = J.W. | last8 = Landry | first8 = M.R. | last9 = Marchi | first9 = A. | last10 = Measures | first10 = C.I. | last11 = Nelson | first11 = D.M. | last12 = Parker | first12 = A.E. | last13 = Poulton | first13 = A.J. | last14 = Selph | first14 = K.E. | last15 = Strutton | first15 = P.G. | last16 = Taylor | first16 = A.G. | last17 = Twining | first17 = B.S. | year = 2011 | title = Co-limitation of diatoms by iron and silicic acid in the equatorial Pacific | url = | journal = Deep-Sea Research Part II: Topical Studies in Oceanography | volume = 58 | issue = 3–4| pages = 493–511 | doi = 10.1016/j.dsr2.2010.08.005 | bibcode = 2011DSRII..58..493B }}</ref> Iron can also be oxidized by marine microbes under conditions that are high in iron and low in oxygen.<ref>{{cite journal | last1 = Field | first1 = E. K. | last2 = Kato | first2 = S. | last3 = Findlay | first3 = A. J. | last4 = MacDonald | first4 = D. J. | last5 = Chiu | first5 = B. K. | last6 = Luther | first6 = G. W. | last7 = Chan | first7 = C. S. | year = 2016 | title = Planktonic marine iron oxidizers drive iron mineralization under low-oxygen conditions | url = | journal = Geobiology | volume = 14 | issue = 5| pages = 499–508 | doi = 10.1111/gbi.12189 | pmid = 27384464 | bibcode = 2016Gbio...14..499F }}</ref>

Iron can enter marine systems through adjoining rivers and directly from the atmosphere. Once iron enters the ocean, it can be distributed throughout the water column through ocean mixing and through recycling on the cellular level.<ref>{{cite journal | last1 = Wells | first1 = M.L. | last2 = Price | first2 = N.M. | last3 = Bruland | first3 = K.W. | year = 1995 | title = Iron chemistry in seawater and its relationship to phytoplankton: a workshop report | url = | journal = Marine Chemistry | volume = 48 | issue = 2| pages = 157–182 | doi = 10.1016/0304-4203(94)00055-I | bibcode = 1995MarCh..48..157W }}</ref> In the arctic, sea ice plays a major role in the store and distribution of iron in the ocean, depleting oceanic iron as it freezes in the winter and releasing it back into the water when thawing occurs in the summer.<ref>{{cite journal | last1 = Lannuzel | first1 = D. | last2 = Vancoppenolle | first2 = M. | last3 = van der Merwe | first3 = P. | last4 = de Jong | first4 = J. | last5 = Meiners | first5 = K.M. | last6 = Grotti | first6 = M. | last7 = Nishioska | first7 = J. | last8 = Schoemann | year = 2016 | title = Iron in sea ice: Review and new insights | url = | journal = Elementa: Science of the Anthropocene | volume = 4 | issue = | page = 000130 | doi = 10.12952/journal.elementa.000130 | bibcode = 2016EleSA...4.0130L }}</ref> The iron cycle can fluctuate the forms of iron from aqueous to particle forms altering the availability of iron to primary producers.<ref>{{cite journal | last1 = Raiswell | first1 = R | year = 2011 | title = Iron Transport from the Continents to the Open Ocean: The Aging–Rejuvenation Cycle | url = | journal = Elements | volume = 7 | issue = 2| pages = 101–106 | doi = 10.2113/gselements.7.2.101 | bibcode = 2011Eleme...7..101R }}</ref> Increased light and warmth increases the amount of iron that is in forms that are usable by primary producers.<ref>{{cite journal | last1 = Tagliabue | first1 = A. | last2 = Bopp | first2 = L. | last3 = Aumont | first3 = O. | last4 = Arrigo | first4 = K.R. | year = 2009 | title = Influence of light and temperature on the marine iron cycle: From theoretical to global modeling | url = https://hal.science/hal-00413634/file/2008GB003214.pdf| journal = Global Biogeochemical Cycles | volume =  23| issue = 2| page =  | doi = 10.1029/2008GB003214 | bibcode = 2009GBioC..23.2017T }}</ref>