Editing Diatom (section)

===Carbon cycle===
The diagram depicts some mechanisms by which marine diatoms contribute to the [[biological carbon pump]] and influence the [[ocean carbon cycle]]. The anthropogenic CO<sub>2</sub> emission to the atmosphere (mainly generated by fossil fuel burning and deforestation) is nearly 11 [[gigatonne]] carbon (GtC) per year, of which almost 2.5 GtC is taken up by the surface ocean. In surface seawater ([[pH]] 8.1–8.4), [[bicarbonate]] ({{chem|H|C|O|3|-}}) and [[carbonate]] ions ({{chem|CO|3|2-}}) constitute nearly 90 and <10% of [[dissolved inorganic carbon]] (DIC) respectively, while dissolved CO<sub>2</sub> (CO<sub>2</sub> aqueous) contributes <1%. Despite this low level of CO<sub>2</sub> in the ocean and its slow [[diffusion rate]] in water, diatoms fix 10–20 GtC annually via photosynthesis thanks to their [[carbon dioxide concentrating mechanism]]s, allowing them to sustain [[marine food chain]]s. In addition, 0.1–1% of this organic material produced in the [[euphotic zone|euphotic layer]] sinks down as particles, thus transferring the surface carbon toward the deep ocean and [[Carbon sequestration|sequestering atmospheric CO<sub>2</sub>]] for thousands of years or longer. The remaining [[organic matter]] is [[Remineralisation|remineralized]] through respiration. Thus, diatoms are one of the main players in this biological carbon pump, which is arguably the most important biological mechanism in the Earth System allowing CO<sub>2</sub> to be removed from the [[carbon cycle]] for very long period.<ref name="Friedlingstein etal 2020">{{cite journal | last1=Friedlingstein | first1=Pierre | last2=O'Sullivan | first2=Michael | last3=Jones | first3=Matthew W. | last4=Andrew | first4=Robbie M. | last5=Hauck | first5=Judith | last6=Olsen | first6=Are | last7=Peters | first7=Glen P. | last8=Peters | first8=Wouter | last9=Pongratz | first9=Julia | last10=Sitch | first10=Stephen | last11=Le Quéré | first11=Corinne | last12=Canadell | first12=Josep G. | last13=Ciais | first13=Philippe | last14=Jackson | first14=Robert B. | last15=Alin | first15=Simone | last16=Aragão | first16=Luiz E. O. C. | last17=Arneth | first17=Almut | last18=Arora | first18=Vivek | last19=Bates | first19=Nicholas R. | last20=Becker | first20=Meike | last21=Benoit-Cattin | first21=Alice | last22=Bittig | first22=Henry C. | last23=Bopp | first23=Laurent | last24=Bultan | first24=Selma | last25=Chandra | first25=Naveen | last26=Chevallier | first26=Frédéric | last27=Chini | first27=Louise P. | last28=Evans | first28=Wiley | last29=Florentie | first29=Liesbeth | last30=Forster | first30=Piers M. | last31=Gasser | first31=Thomas | last32=Gehlen | first32=Marion | last33=Gilfillan | first33=Dennis | last34=Gkritzalis | first34=Thanos | last35=Gregor | first35=Luke | last36=Gruber | first36=Nicolas | last37=Harris | first37=Ian | last38=Hartung | first38=Kerstin | last39=Haverd | first39=Vanessa | last40=Houghton | first40=Richard A. | last41=Ilyina | first41=Tatiana | last42=Jain | first42=Atul K. | last43=Joetzjer | first43=Emilie | last44=Kadono | first44=Koji | last45=Kato | first45=Etsushi | last46=Kitidis | first46=Vassilis | last47=Korsbakken | first47=Jan Ivar | last48=Landschützer | first48=Peter | last49=Lefèvre | first49=Nathalie | last50=Lenton | first50=Andrew | last51=Lienert | first51=Sebastian | last52=Liu | first52=Zhu | last53=Lombardozzi | first53=Danica | last54=Marland | first54=Gregg | last55=Metzl | first55=Nicolas | last56=Munro | first56=David R. | last57=Nabel | first57=Julia E. M. S. | last58=Nakaoka | first58=Shin-Ichiro | last59=Niwa | first59=Yosuke | last60=O'Brien | first60=Kevin | last61=Ono | first61=Tsuneo | last62=Palmer | first62=Paul I. | last63=Pierrot | first63=Denis | last64=Poulter | first64=Benjamin | last65=Resplandy | first65=Laure | last66=Robertson | first66=Eddy | last67=Rödenbeck | first67=Christian | last68=Schwinger | first68=Jörg | last69=Séférian | first69=Roland | last70=Skjelvan | first70=Ingunn | last71=Smith | first71=Adam J. P. | last72=Sutton | first72=Adrienne J. | last73=Tanhua | first73=Toste | last74=Tans | first74=Pieter P. | last75=Tian | first75=Hanqin | last76=Tilbrook | first76=Bronte | last77=van der Werf | first77=Guido | last78=Vuichard | first78=Nicolas | last79=Walker | first79=Anthony P. | last80=Wanninkhof | first80=Rik | last81=Watson | first81=Andrew J. | last82=Willis | first82=David | last83=Wiltshire | first83=Andrew J. | last84=Yuan | first84=Wenping | last85=Yue | first85=Xu | last86=Zaehle | first86=Sönke | title=Global Carbon Budget 2020 | journal=Earth System Science Data | publisher=Copernicus GmbH | volume=12 | issue=4 | date=2020-12-11 | issn=1866-3516 | doi=10.5194/essd-12-3269-2020 | pages=3269–3340| bibcode=2020ESSD...12.3269F | display-authors=4| doi-access=free | hdl=10871/126892 | hdl-access=free }}</ref><ref name="Karlusich 2021" />

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File:Urea cycle in a diatom.jpg|alt=Mitochondrial urea cycle in a generic diatom cell and the potential fates of urea cycle intermediates| Mitochondrial urea cycle in a generic diatom cell and the potential fates of urea cycle intermediates{{hsp}}<ref name=Glibert2015>{{cite journal | last1=Glibert | first1=Patricia M. | last2=Wilkerson | first2=Frances P. | last3=Dugdale | first3=Richard C. | last4=Raven | first4=John A. | last5=Dupont | first5=Christopher L. | last6=Leavitt | first6=Peter R. | last7=Parker | first7=Alexander E. | last8=Burkholder | first8=JoAnn M. | last9=Kana | first9=Todd M. | display-authors = 6 | title=Pluses and minuses of ammonium and nitrate uptake and assimilation by phytoplankton and implications for productivity and community composition, with emphasis on nitrogen-enriched conditions | journal=Limnology and Oceanography | publisher=Wiley | volume=61 | issue=1 | date=2015-10-11 | issn=0024-3590 | doi=10.1002/lno.10203 | pages=165–197| s2cid=16561857 }} [[File:CC-BY icon.svg|50px]] Modified 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].</ref>
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