Editing Coccolithophore (section)

=== Uses ===
Coccoliths are the main component of [[Chalk Group|the Chalk]], a Late Cretaceous rock formation which outcrops widely in southern England and forms the [[White Cliffs of Dover]], and of other similar rocks in many other parts of the world.<ref name="hup.harvard.edu"/> At the present day sedimented coccoliths are a major component of the [[Pelagic sediment#Oozes|calcareous oozes]] that cover up to 35% of the ocean floor and is kilometres thick in places.<ref name=deVargas2007 />  Because of their abundance and wide geographic ranges, the coccoliths which make up the layers of this ooze and the chalky sediment formed as it is compacted serve as valuable [[microfossils]].
[[File:Calcification and energetic costs of a coccolithophore cell.jpg|thumb|right|360px|Energetic costs of coccolithophore calcification.<ref name=Monteiro2016 /> Energetic costs reported as a percentage of total [[photosynthetic]] budget.]]

[[Calcification]], the biological production of [[calcium carbonate]] (CaCO<sub>3</sub>), is a key process in the [[marine carbon cycle]]. Coccolithophores are the major planktonic group responsible for pelagic CaCO<sub>3</sub> production.<ref>{{cite journal |doi = 10.1016/j.pocean.2017.10.007|title = Coccolithophore growth and calcification in a changing ocean|year = 2017|last1 = Krumhardt|first1 = Kristen M.|last2 = Lovenduski|first2 = Nicole S.|last3 = Iglesias-Rodriguez|first3 = M. Debora|last4 = Kleypas|first4 = Joan A.|author-link4=Joan Kleypas|journal = Progress in Oceanography|volume = 159|pages = 276–295| bibcode=2017PrOce.159..276K |doi-access = free}}</ref><ref>{{cite journal |doi = 10.5194/essd-10-1859-2018|title = A global compilation of coccolithophore calcification rates|year = 2018|last1 = Daniels|first1 = Chris J.|last2 = Poulton|first2 = Alex J.|last3 = Balch|first3 = William M.|last4 = Marañón|first4 = Emilio|last5 = Adey|first5 = Tim|last6 = Bowler|first6 = Bruce C.|last7 = Cermeño|first7 = Pedro|last8 = Charalampopoulou|first8 = Anastasia|last9 = Crawford|first9 = David W.|last10 = Drapeau|first10 = Dave|last11 = Feng|first11 = Yuanyuan|last12 = Fernández|first12 = Ana|last13 = Fernández|first13 = Emilio|last14 = Fragoso|first14 = Glaucia M.|last15 = González|first15 = Natalia|last16 = Graziano|first16 = Lisa M.|last17 = Heslop|first17 = Rachel|last18 = Holligan|first18 = Patrick M.|last19 = Hopkins|first19 = Jason|last20 = Huete-Ortega|first20 = María|last21 = Hutchins|first21 = David A.|last22 = Lam|first22 = Phoebe J.|last23 = Lipsen|first23 = Michael S.|last24 = López-Sandoval|first24 = Daffne C.|last25 = Loucaides|first25 = Socratis|last26 = Marchetti|first26 = Adrian|last27 = Mayers|first27 = Kyle M. J.|last28 = Rees|first28 = Andrew P.|last29 = Sobrino|first29 = Cristina|last30 = Tynan|first30 = Eithne|journal = Earth System Science Data|volume = 10|issue = 4|pages = 1859–1876| bibcode=2018ESSD...10.1859D |display-authors = 29|doi-access = free}} [[File:CC-BY icon.svg|50px]] 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> The diagram on the right shows the energetic costs of coccolithophore calcification:

: (A) Transport processes include the transport into the cell from the surrounding seawater of primary calcification substrates [[Ca2+|Ca<sub>2+</sub>]] and [[HCO3-|HCO<sub>3</sub><sup>−</sup>]] (black arrows) and the removal of the end product H<sup>+</sup> from the cell (gray arrow). The transport of Ca<sub>2+</sub> through the [[cytoplasm]] to the CV is the dominant cost associated with calcification.<ref name=Monteiro2016 />

: (B) [[Metabolic process]]es include the synthesis of CAPs (gray rectangles) by the [[Golgi complex]] (white rectangles) that regulate the [[nucleation]] and geometry of CaCO<sub>3</sub> crystals. The completed coccolith (gray plate) is a complex structure of intricately arranged CAPs and CaCO<sub>3</sub> crystals.<ref name=Monteiro2016 />

: (C) Mechanical and structural processes account for the secretion of the completed coccoliths that are transported from their original position adjacent to the nucleus to the cell periphery, where they are transferred to the surface of the cell. The costs associated with these processes are likely to be comparable to organic-scale [[exocytosis]] in noncalcifying [[haptophyte]] algae.<ref name=Monteiro2016 />

{{clear}}

[[File:Benefits of calcification in coccolithophores.jpg|thumb|left|500px|Benefits of coccolithophore calcification<ref name=Monteiro2016 />]]

The diagram on the left shows the benefits of coccolithophore calcification. (A) Accelerated photosynthesis includes CCM (1) and enhanced light uptake via scattering of scarce photons for deep-dwelling species (2). (B) Protection from photodamage includes sunshade protection from ultraviolet (UV) light and photosynthetic active radiation (PAR) (1) and energy dissipation under high-light conditions (2). (C) Armor protection includes protection against viral/bacterial infections (1) and grazing by selective (2) and nonselective (3) grazers.<ref name=Monteiro2016 />

The degree by which calcification can adapt to [[ocean acidification]] is presently unknown. Cell physiological examinations found the essential [[Efflux (microbiology)|H<sup>+</sup> efflux]] (stemming from the use of HCO<sub>3</sub><sup>−</sup> for intra-cellular calcification) to become more costly with ongoing ocean acidification as the electrochemical H<sup>+</sup> inside-out gradient is reduced and passive proton outflow impeded.<ref name="A Voltage-Gated H+ Channel Underlyi">{{cite journal |doi = 10.1371/journal.pbio.1001085|title = A Voltage-Gated H<sup>+</sup> Channel Underlying pH Homeostasis in Calcifying Coccolithophores|year = 2011|last1 = Taylor|first1 = Alison R.|last2 = Chrachri|first2 = Abdul|last3 = Wheeler|first3 = Glen|last4 = Goddard|first4 = Helen|last5 = Brownlee|first5 = Colin|journal = PLOS Biology|volume = 9|issue = 6|pages = e1001085|pmid = 21713028|pmc = 3119654 | doi-access=free }}</ref> Adapted cells would have to activate [[proton channel]]s more frequently, adjust their [[membrane potential]], and/or lower their internal [[pH]].<ref>{{cite journal |doi = 10.1016/j.tplants.2012.06.009|title = Proton channels in algae: Reasons to be excited|year = 2012|last1 = Taylor|first1 = Alison R.|last2 = Brownlee|first2 = Colin|last3 = Wheeler|first3 = Glen L.|journal = Trends in Plant Science|volume = 17|issue = 11|pages = 675–684|pmid = 22819465}}</ref> Reduced intra-cellular pH would severely affect the entire cellular machinery and require other processes (e.g. [[photosynthesis]]) to co-adapt in order to keep H<sup>+</sup> efflux alive.<ref>{{cite journal |doi = 10.1098/rstb.2013.0049|title = Emiliania huxleyi increases calcification but not expression of calcification-related genes in long-term exposure to elevated temperature and p CO 2|year = 2013|last1 = Benner|first1 = Ina|last2 = Diner|first2 = Rachel E.|last3 = Lefebvre|first3 = Stephane C.|last4 = Li|first4 = Dian|last5 = Komada|first5 = Tomoko|last6 = Carpenter|first6 = Edward J.|last7 = Stillman|first7 = Jonathon H.|journal = Philosophical Transactions of the Royal Society B: Biological Sciences|volume = 368|issue = 1627|pmid = 23980248|pmc = 3758179}}</ref><ref>{{cite journal |doi = 10.1026/1612-5010/a000109|title = Das physische Selbstkonzept, die individuell präferierte Bezugsnormorientierung und die Zielorientierung bei Grundschulkindern der zweiten und vierten Jahrgangsstufe|year = 2014|last1 = Lohbeck|first1 = Annette|last2 = Tietjens|first2 = Maike|last3 = Bund|first3 = Andreas|journal = Zeitschrift für Sportpsychologie|volume = 21|pages = 1–12}}</ref> The obligatory H<sup>+</sup> efflux associated with calcification may therefore pose a fundamental constraint on adaptation which may potentially explain why "calcification crisis" were possible during long-lasting (thousands of years) CO<sub>2</sub> perturbation events<ref name="Nannofossil carbonate fluxes during">{{cite journal |doi = 10.1029/2003PA000884|title = Nannofossil carbonate fluxes during the Early Cretaceous: Phytoplankton response to nutrification episodes, atmospheric CO2, and anoxia|year = 2004|last1 = Erba|first1 = Elisabetta|last2 = Tremolada|first2 = Fabrizio|journal = Paleoceanography|volume = 19|issue = 1|pages = n/a|bibcode = 2004PalOc..19.1008E|doi-access = free}}</ref><ref name="The first 150 million years history">{{cite journal |doi = 10.1016/j.palaeo.2005.09.013|title = The first 150 million years history of calcareous nannoplankton: Biosphere–geosphere interactions|year = 2006|last1 = Erba|first1 = Elisabetta|journal = Palaeogeography, Palaeoclimatology, Palaeoecology|volume = 232|issue = 2–4|pages = 237–250|bibcode = 2006PPP...232..237E}}</ref> even though evolutionary adaption to changing [[carbonate]] chemistry conditions is possible within one year.<ref name="Nannofossil carbonate fluxes during"/><ref name="The first 150 million years history"/> Unraveling these fundamental constraints and the limits of adaptation should be a focus in future coccolithophore studies because knowing them is the key information required to understand to what extent the calcification response to carbonate chemistry perturbations can be compensated by evolution.<ref name=Bach2015 />

Silicate- or cellulose-armored functional groups such as [[diatom]]s and [[dinoflagellate]]s do not need to sustain the calcification-related H<sup>+</sup> efflux. Thus, they probably do not need to adapt in order to keep costs for the production of structural elements low. On the contrary, dinoflagellates (except for calcifying species;<ref>{{cite journal |doi = 10.1371/journal.pone.0065987|title = Ocean Acidification Reduces Growth and Calcification in a Marine Dinoflagellate|year = 2013|last1 = Van De Waal|first1 = Dedmer B.|last2 = John|first2 = Uwe|last3 = Ziveri|first3 = Patrizia|last4 = Reichart|first4 = Gert-Jan|last5 = Hoins|first5 = Mirja|last6 = Sluijs|first6 = Appy|last7 = Rost|first7 = Björn|journal = PLOS ONE|volume = 8|issue = 6|pages = e65987|pmid = 23776586|pmc = 3679017|bibcode = 2013PLoSO...865987V| doi-access=free }}</ref> with generally inefficient CO<sub>2</sub>-fixing [[RuBisCO|RuBisCO enzymes]]<ref>{{cite journal |doi = 10.4319/lo.2000.45.3.0744|title = Evolutionary and ecological perspectives on carbon acquisition in phytoplankton|year = 2000|last1 = Tortell|first1 = Philippe D.|journal = Limnology and Oceanography|volume = 45|issue = 3|pages = 744–750|bibcode = 2000LimOc..45..744T|doi-access = free}}</ref> may even profit from chemical changes since photosynthetic [[carbon fixation]] as their source of structural elements in the form of cellulose should be facilitated by the ocean acidification-associated CO<sub>2</sub> fertilization.<ref>{{cite journal |doi = 10.1016/j.hal.2007.05.006|title = A comparison of future increased CO2 and temperature effects on sympatric Heterosigma akashiwo and Prorocentrum minimum|year = 2008|last1 = Fu|first1 = Fei-Xue|last2 = Zhang|first2 = Yaohong|last3 = Warner|first3 = Mark E.|last4 = Feng|first4 = Yuanyuan|last5 = Sun|first5 = Jun|last6 = Hutchins|first6 = David A.|journal = Harmful Algae|volume = 7|pages = 76–90}}</ref><ref>{{cite journal |doi = 10.1146/annurev-marine-120709-142720|title = Carbon Concentrating Mechanisms in Eukaryotic Marine Phytoplankton|year = 2011|last1 = Reinfelder|first1 = John R.|journal = Annual Review of Marine Science|volume = 3|pages = 291–315|pmid = 21329207|bibcode = 2011ARMS....3..291R}}</ref> Under the assumption that any form of shell/exoskeleton protects phytoplankton against predation<ref name="Evolution of Primary Producers in t"/> non-calcareous armors may be the preferable solution to realize protection in a future ocean.<ref name=Bach2015 />

[[File:Energetic effort for armor construction in shell-forming phytoplankton.jpg|thumb|upright=2|right|Representation of comparative energetic effort for armor construction in three major shell-forming phytoplankton taxa as a function of [[carbonate]] chemistry conditions<ref name=Bach2015 />]]

The diagram on the right is a representation of how the comparative energetic effort for armor construction in diatoms, dinoflagellates and coccolithophores appear to operate. The [[frustule]] (diatom shell) seems to be the most inexpensive armor under all circumstances because diatoms typically outcompete all other groups when silicate is available. The coccosphere is relatively inexpensive under sufficient [CO<sub>2</sub>], high [HCO<sub>3</sub><sup>−</sup>], and low [H<sup>+</sup>] because the substrate is saturating and protons are easily released into seawater.<ref name="A Voltage-Gated H+ Channel Underlyi"/> In contrast, the construction of [[Dinoflagellate#Morphology|thecal]] elements, which are organic ([[cellulose]]) plates that constitute the dinoflagellate shell, should rather be favored at high H<sup>+</sup> concentrations because these usually coincide with high [CO<sub>2</sub>]. Under these conditions dinoflagellates could down-regulate the energy-consuming operation of carbon concentrating mechanisms to fuel the production of organic source material for their shell. Therefore, a shift in carbonate chemistry conditions toward high [CO<sub>2</sub>] may promote their competitiveness relative to coccolithophores. However, such a hypothetical gain in competitiveness due to altered carbonate chemistry conditions would not automatically lead to dinoflagellate dominance because a huge number of factors other than carbonate chemistry have an influence on [[species composition]] as well.<ref name=Bach2015>{{cite journal |doi = 10.1016/j.pocean.2015.04.012|title = A unifying concept of coccolithophore sensitivity to changing carbonate chemistry embedded in an ecological framework|year = 2015|last1 = Bach|first1 = Lennart Thomas|last2 = Riebesell|first2 = Ulf|last3 = Gutowska|first3 = Magdalena A.|last4 = Federwisch|first4 = Luisa|last5 = Schulz|first5 = Kai Georg|journal = Progress in Oceanography|volume = 135|pages = 125–138|bibcode = 2015PrOce.135..125B|doi-access = free}} [[File:CC-BY icon.svg|50px]] 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><ref>{{Cite Q|Q52718666|author1=Xu, K. |author2=Hutchins, D.|author3=Gao, K.|doi-access=free}}</ref>