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{{Use British English|date=August 2021}}
{{Use dmy dates|date=August 2021}}
[[File:Oceanic Food Web.jpg|thumb|upright=
{{marine life sidebar}}▼
The '''biological pump''' (or '''ocean carbon biological pump''' or '''marine biological carbon pump''') is the ocean's biologically driven [[Carbon sequestration|sequestration of carbon]] from the atmosphere and land runoff to the ocean interior and [[seafloor sediments]].<ref name=Sigman2006>Sigman DM & GH Haug. 2006. The biological pump in the past. In: Treatise on Geochemistry; vol. 6, (ed.). [[Pergamon Press]], pp. 491-528</ref> In other words, it is a biologically mediated
Budget calculations of the biological carbon pump are based on the ratio between [[Marine sediment|sedimentation]] (carbon export to the ocean floor) and [[remineralization]] (release of carbon to the atmosphere).
The biological pump is not so much the result of a single process, but rather the sum of a number of processes each of which can influence biological pumping. Overall, the pump transfers about
==Overview==
▲{{marine life sidebar}}
[[File:Components of the biological pump 2018.jpg|thumb|upright=1.203| {{center|'''Pump processes vary with depth'''}} Photic zone: 0–100 m; Mesopelagic: 100–1000 m; Bathypelagic: 1000 to abyssal depths. Below 1000 m depth carbon is considered removed from the atmosphere for at least 100 years. Scavenging: DOC incorporation within sinking particles.<ref name=Boscolo-Galazzo2018>{{cite journal |doi = 10.1016/j.gloplacha.2018.08.017|title = Temperature dependency of metabolic rates in the upper ocean: A positive feedback to global climate change?|year = 2018|last1 = Boscolo-Galazzo|first1 = F.|last2 = Crichton|first2 = K.A.|last3 = Barker|first3 = S.|last4 = Pearson|first4 = P.N.|journal = Global and Planetary Change|volume = 170|pages = 201–212|bibcode = 2018GPC...170..201B|doi-access = free}} [[File:CC-BY icon.svg|50px]] Modified text 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 element [[carbon]] plays a central role in climate and life on Earth. It is capable of moving among and between the [[geosphere]], [[cryosphere]], [[atmosphere]], [[biosphere]] and [[hydrosphere]]. This flow of carbon is referred to as the Earth's [[carbon cycle]]. It is also intimately linked to the cycling of other elements and compounds. The ocean plays a fundamental role in Earth's carbon cycle, helping to regulate atmospheric CO<sub>2</sub> concentration. The biological pump is a set of processes that transfer [[organic carbon]] from the surface to the deep ocean, and is at the heart of the [[ocean carbon cycle]].<ref name=Brewin2021 />
The biological pump depends on the fraction of primary produced [[organic matter]] that survives degradation in the [[euphotic zone]] and that is exported from surface water to the ocean interior, where it is [[Biomineralization|mineralized]] to [[inorganic carbon]], with the result that carbon is transported against the gradient of [[dissolved inorganic carbon]] (DIC) from the surface to the deep ocean. This transfer occurs through physical mixing and transport of dissolved and [[particulate organic carbon]] (POC), [[Diel vertical migration|vertical migrations]] of organisms ([[zooplankton]], [[fish]]) and through gravitational settling of particulate organic carbon.<ref name=Volk1885>{{cite book |doi = 10.1029/GM032p0099|chapter = Ocean Carbon Pumps: Analysis of Relative Strengths and Efficiencies in Ocean-Driven Atmospheric CO2 Changes|title = The Carbon Cycle and Atmospheric CO2 : Natural Variations Archean to Present|series = Geophysical Monograph Series|year = 2013|last1 = Volk|first1 = Tyler|last2 = Hoffert|first2 = Martin I.|pages = 99–110|isbn = 9781118664322}}</ref><ref name=Sarmiento2013>{{Cite book|url=https://books.google.com/books?id=QWUeAAAAQBAJ&q=%22Ocean+Biogeochemical+Dynamics%22|title = Ocean Biogeochemical Dynamics|isbn = 9781400849079|last1 = Sarmiento|first1 = Jorge L.|date = 17 July 2013|page = 526| publisher=Princeton University Press }}</ref>{{rp|526}}<ref name=Middelburg2019>{{cite book |doi = 10.1007/978-3-030-10822-9_3|chapter = The Return from Organic to Inorganic Carbon|title = Marine Carbon Biogeochemistry|series = SpringerBriefs in Earth System Sciences|year = 2019|last1 = Middelburg|first1 = Jack J.|pages = 37–56|isbn = 978-3-030-10821-2|s2cid = 104330175}} [[File:CC-BY icon.svg|50px]] Modified text 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 biological pump can be divided into three distinct phases, the first of which is the production of fixed carbon by planktonic [[phototrophs]] in the [[euphotic]] (sunlit) surface region of the ocean. In these surface waters, [[phytoplankton]] use [[carbon dioxide]] (CO<sub>2</sub>), [[nitrogen]] (N), [[phosphorus]] (P), and other trace elements ([[barium]], [[iron]], [[zinc]], etc.) during photosynthesis to make [[carbohydrates]], [[lipids]], and [[proteins]]. Some plankton, (e.g. [[coccolithophores]] and [[foraminifera]]) combine calcium (Ca) and dissolved carbonates ([[carbonic acid]] and [[bicarbonate]]) to form a calcium carbonate (CaCO<sub>3</sub>) protective coating.<ref name=DeLaRocha2014>{{cite book |doi = 10.1016/B978-0-08-095975-7.00604-5|chapter = The Biological Pump|title = Treatise on Geochemistry|year = 2014|last1 = de la Rocha|first1 = C.L.|last2 = Passow|first2 = U.|pages = 93–122|isbn = 9780080983004}}</ref>
Once this carbon is fixed into soft or hard tissue, the organisms either stay in the euphotic zone to be recycled as part of the regenerative [[nutrient cycle]] or once they die, continue to the second phase of the biological pump and begin to sink to the ocean floor. The sinking particles will often form aggregates as they sink, greatly increasing the sinking rate. It is this aggregation that gives particles a better chance of escaping predation and decomposition in the water column and eventually making it to the sea floor.<ref name=DeLaRocha2014 />▼
▲[[File:Components of the biological pump 2018.jpg|thumb|upright=1.203| {{center|'''Pump processes vary with depth'''}}
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The fixed carbon that is decomposed by bacteria either on the way down or once on the sea floor then enters the final phase of the pump and is remineralized to be used again in [[primary production]]. The particles that escape these processes entirely are sequestered in the sediment and may remain there for millions of years. It is this [[Carbon sequestration|sequestered carbon]] that is responsible for ultimately lowering atmospheric CO<sub>2</sub>.<ref name=DeLaRocha2014 />▼
{{carbon cycle|pump}}
▲Once this carbon is fixed into soft or hard tissue, the organisms either stay in the euphotic zone to be recycled as part of the regenerative [[nutrient cycle]] or once they die, continue to the second phase of the biological pump and begin to sink to the ocean floor. The sinking particles will often form aggregates as they sink, which greatly
▲{{clear left}}
▲The fixed carbon that is decomposed by bacteria either on the way down or once on the sea floor then enters the final phase of the pump and is remineralized to be used again in [[primary production]]. The particles that escape these processes entirely are sequestered in the sediment and may remain there for millions of years. It is this [[Carbon sequestration|sequestered carbon]] that is responsible for ultimately lowering atmospheric CO<sub>2</sub>.<ref name=DeLaRocha2014 />
The biological pump is responsible for transforming [[dissolved inorganic carbon]] (DIC) into organic biomass and pumping it in [[particulate organic carbon|particulate]] or dissolved form into the deep ocean. Inorganic nutrients and carbon dioxide are fixed during photosynthesis by phytoplankton, which both release [[dissolved organic matter]] (DOM) and are consumed by herbivorous zooplankton. Larger zooplankton - such as [[copepod]]s - [[egest]] [[fecal pellet]]s which can be reingested and sink or collect with other organic detritus into larger, more-rapidly-sinking aggregates. DOM is partially consumed by bacteria (black dots) and respired; the remaining [[refractory DOM]] is [[advected]] and mixed into the deep sea. DOM and aggregates exported into the deep water are consumed and respired, thus returning organic carbon into the enormous deep ocean reservoir of DIC. About 1% of the particles leaving the surface ocean reach the seabed and are consumed, respired, or buried in the sediments. There, carbon is stored for millions of years. The net effect of these processes is to remove carbon in organic form from the surface and return it to DIC at greater depths, maintaining the surface-to-deep ocean gradient of DIC. [[Thermohaline circulation]] returns deep-ocean DIC to the atmosphere on millennial timescales.<ref name=Ducklow2001 />
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[[File:Size and classification of marine particles.png|thumb|upright=2|right| {{center|'''Size and classification of marine particles<ref>Monroy, P., Hernández-García, E., Rossi, V. and López, C. (2017) "Modeling the dynamical sinking of biogenic particles in oceanic flow". ''Nonlinear Processes in Geophysics'', '''24'''(2): 293–305. {{doi|10.5194/npg-24-293-2017}}. [[File:CC-BY icon.svg|50px]] Modified text was copied from this source, which is available under a [https://creativecommons.org/licenses/by/3.0/ Creative Commons Attribution 3.0 International License].</ref>'''<br /><small>Adapted from Simon et al., 2002.<ref>Simon, M., Grossart, H., Schweitzer, B. and [[Helle Ploug|Ploug, H.]] (2002) "Microbial ecology of organic aggregates in aquatic ecosystems". ''Aquatic microbial ecology'', '''28''': 175–211. {{doi|10.3354/ame028175}}.</ref></small>}}]]
The first step in the biological pump is the synthesis of both organic and inorganic carbon compounds by phytoplankton in the uppermost, sunlit layers of the ocean.<ref name="Sigman&Hain2012">{{cite journal |title=The Biological Productivity of the Ocean |journal=Nature Education Knowledge |year=2012 |last1=Sigman |first1=D.M. |last2=Hain |first2=M.P. |volume=3 |issue=6 |pages=1–16 |url=https://earth-system-biogeochemistry.net/wp-content/uploads/2021/05/Sigman_and_Hain_2012_NatureEdu.pdf |access-date=2015-06-01 |quote=The value of NEP [Net Ecosystem Production] depends on the boundaries defined for the ecosystem. If one considers the sunlit surface ocean down to the 1% light level (the
CO<sub>2</sub> + H<sub>2</sub>O + light → CH<sub>2</sub>O + O<sub>2</sub>
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In addition to carbon, organic matter found in phytoplankton is composed of nitrogen, phosphorus and various [[trace metals]]. The ratio of carbon to nitrogen and phosphorus varies from place to place,<ref>{{cite journal |last1=Martiny |first1=Adam C. |last2=Pham |first2=Chau T. A. |last3=Primeau |first3=Francois W. |last4=Vrugt |first4=Jasper A. |last5=Moore |first5=J. Keith |last6=Levin |first6=Simon A. |last7=Lomas |first7=Michael W. |title=Strong latitudinal patterns in the elemental ratios of marine plankton and organic matter |journal=Nature Geoscience |date=April 2013 |volume=6 |issue=4 |pages=279–283 |doi=10.1038/NGEO1757|bibcode=2013NatGe...6..279M |s2cid=5677709 |url=http://www.escholarship.org/uc/item/68n582hp }}</ref> but has an average ratio near 106C:16N:1P, known as the [[Redfield ratio]]. Trace metals such as magnesium, cadmium, iron, calcium, barium and copper are orders of magnitude less prevalent in phytoplankton organic material, but necessary for certain metabolic processes and therefore can be limiting nutrients in photosynthesis due to their lower abundance in the water column.<ref name=DeLaRocha2014 />
Oceanic primary production accounts for about half of the carbon fixation carried out on Earth. Approximately 50–60 [[Petagram|Pg]] of carbon are fixed by marine phytoplankton each year despite the fact that they
==Forms of carbon==
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[[File:Fate of DOM in the ocean.png|thumb|upright=2|right| {{center|'''The fate of DOM in the ocean'''}}]]
[[File:Particulate inorganic carbon budget for Hudson Bay.jpg|thumb|upright=2|right| {{center|Particulate inorganic carbon budget for Hudson Bay}} Black arrows represent DIC produced by PIC dissolution. Grey lines represent terrestrial PIC.<ref>{{cite journal |doi = 10.1016/j.pocean.2020.102319|title = Effect of terrestrial organic matter on ocean acidification and CO2 flux in an Arctic shelf sea|year = 2020|last1 = Capelle|first1 = David W.|last2 = Kuzyk|first2 = Zou Zou A.|last3 = Papakyriakou|first3 = Tim|last4 = Guéguen|first4 = Céline|last5 = Miller|first5 = Lisa A.|last6 = MacDonald|first6 = Robie W.|journal = Progress in Oceanography|volume = 185|page = 102319|bibcode = 2020PrOce.18502319C|doi-access = free|hdl = 1993/34767|hdl-access = free}} [[File:CC-BY icon.svg|50px]] Modified text 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> {{space|20}} <small>Units are Tg C y<sup>−1</sup></small>]]
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===Ocean carbon pools===
The marine biological pump depends on a number of key pools, components and processes that influence its functioning. There are four main pools of carbon in the ocean.<ref name=Brewin2021>{{cite journal | last1=Brewin | first1=Robert J.W. | last2=Sathyendranath | first2=Shubha |author-link2=Shubha Sathyendranath| last3=Platt | first3=Trevor | last4=Bouman | first4=Heather | last5=Ciavatta | first5=Stefano | last6=Dall'Olmo | first6=Giorgio | last7=Dingle | first7=James | last8=Groom | first8=Steve | last9=Jönsson | first9=Bror | last10=Kostadinov | first10=Tihomir S. | last11=Kulk | first11=Gemma | last12=Laine | first12=Marko | last13=Martínez-Vicente | first13=Victor | last14=Psarra | first14=Stella | last15=Raitsos | first15=Dionysios E. | last16=Richardson | first16=Katherine | last17=Rio | first17=Marie-Hélène | last18=Rousseaux | first18=Cécile S. | last19=Salisbury | first19=Joe | last20=Shutler | first20=Jamie D. | last21=Walker | first21=Peter | title=Sensing the ocean biological carbon pump from space: A review of capabilities, concepts, research gaps and future developments | journal=Earth-Science Reviews | publisher=Elsevier BV | volume=217 | year=2021 | issn=0012-8252 | doi=10.1016/j.earscirev.2021.103604 | page=103604| bibcode=2021ESRv..21703604B | s2cid=233682755 |display-authors = 4| hdl=10871/125469 | hdl-access=free }} [[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>
* [[Dissolved inorganic carbon]] (DIC) is the largest pool. It constitutes around 38,000 [[Petagram|Pg]] C{{hsp}}<ref>{{cite journal | last=Hedges | first=John I. | title=Global biogeochemical cycles: progress and problems | journal=Marine Chemistry | publisher=Elsevier BV | volume=39 | issue=1–3 | year=1992 | issn=0304-4203 | doi=10.1016/0304-4203(92)90096-s | pages=67–93| bibcode=1992MarCh..39...67H }}</ref> and includes dissolved carbon dioxide (CO<sub>2</sub>), [[bicarbonate]] ({{chem|HCO|3|-}}), [[carbonate]] ({{chem|CO|3|2-}}), and [[carbonic acid]] ({{chem2|H2CO3|auto=on}}). The equilibrium between carbonic acid and carbonate determines the [[pH]] of the seawater. Carbon dioxide dissolves easily in water and its solubility is inversely related to temperature. Dissolved CO<sub>2</sub> is taken up in the process of photosynthesis, and can reduce the partial pressure of CO<sub>2</sub> in the seawater, favouring drawdown from the atmosphere. The reverse process respiration, releases CO<sub>2</sub> back into the water, can increase partial pressure of CO<sub>2</sub> in the seawater, favouring release back to the atmosphere. The formation of [[calcium carbonate]] by organisms such as [[coccolithophore]]s has the effect of releasing CO<sub>2</sub> into the water.<ref>{{cite book | last1=Zeebe | first1=Richard E. | last2=Wolf-Gladrow | first2=Dieter A. | title=CO2 in seawater : equilibrium, kinetics, isotopes | page=65 | publication-place=Amsterdam | date=2001 | isbn=978-0-08-052922-6 | oclc=246683387}}</ref><ref>{{cite book | last1=Rost | first1=Björn | last2=Riebesell | first2=Ulf
* [[Dissolved organic carbon]] (DOC) is the next largest pool at around 662 Pg C.<ref name=Hansell2013a>{{cite journal | last1=Hansell | first1=Dennis A. | last2=Carlson | first2=Craig A. | title=Localized refractory dissolved organic carbon sinks in the deep ocean | journal=Global Biogeochemical Cycles | publisher=American Geophysical Union (AGU) | volume=27 | issue=3 | date=2013-08-12 | issn=0886-6236 | doi=10.1002/gbc.20067 | pages=705–710| s2cid=17175370 }}</ref> DOC can be classified according to its reactivity as refractory, semi-labile or labile. The labile pool constitutes around 0.2 Pg C, is bioavailable, and has a high production rate (~ 15−25 Pg C y<sup>−1</sup>).<ref name=Hansell2013b>{{cite journal | last=Hansell | first=Dennis A. | title=Recalcitrant Dissolved Organic Carbon Fractions | journal=Annual Review of Marine Science | publisher=Annual Reviews | volume=5 | issue=1 | date=2013-01-03 | issn=1941-1405 | doi=10.1146/annurev-marine-120710-100757 | pages=421–445| pmid=22881353 }}</ref> The refractory component is the biggest pool (~642 Pg C ± 32;<ref name=Hansell2013a /> but has a very low turnover rate (0.043 Pg C y<sup>−1</sup>).<ref name=Hansell2013b /> The turnover time for [[refractory DOC]] is thought to be greater than 1000 years.<ref>{{cite journal | last1=Williams | first1=Peter M. | last2=Druffel | first2=Ellen R. M. | title=Radiocarbon in dissolved organic matter in the central North Pacific Ocean | journal=Nature | publisher=Springer Science and Business Media LLC | volume=330 | issue=6145 | year=1987 | issn=0028-0836 | doi=10.1038/330246a0 | pages=246–248| bibcode=1987Natur.330..246W | s2cid=4329024 | url=https://escholarship.org/uc/item/8d1379dw }}</ref><ref>{{cite journal | last1=Druffel | first1=E. R. M. | last2=Griffin | first2=S. | last3=Coppola | first3=A. I. | last4=Walker | first4=B. D. | title=Radiocarbon in dissolved organic carbon of the Atlantic Ocean | journal=Geophysical Research Letters | publisher=American Geophysical Union (AGU) | volume=43 | issue=10 | date=2016-05-28 | issn=0094-8276 | doi=10.1002/2016gl068746 | pages=5279–5286| bibcode=2016GeoRL..43.5279D | s2cid=56069589 | doi-access=free }}</ref><ref name=Brewin2021 />
* [[Particulate organic carbon]] (POC) constitutes around 2.3 Pg C,<ref>{{cite journal | last1=Stramska | first1=Malgorzata | last2=Cieszyńska | first2=Agata | title=Ocean colour estimates of particulate organic carbon reservoirs in the global ocean – revisited | journal=International Journal of Remote Sensing | publisher=Informa UK Limited | volume=36 | issue=14 | date=2015-07-18 | issn=0143-1161 | doi=10.1080/01431161.2015.1049380 | pages=3675–3700| bibcode=2015IJRS...36.3675S | s2cid=128524215 }}</ref><ref>Wickland, D.E., Plummer, S. and Nakajima, M. (October 2013). "CEOS strategy for carbon observations from space". In: ''International Conference Towards a Global Carbon Observing System: Progresses and Challenges'', '''1''':. 2.</ref> and is relatively small compared with DIC and DOC. Though small in size, this pool is highly dynamic, having the highest turnover rate of any organic carbon pool on the planet.<ref>{{cite book | last=Sarmiento | first=Jorge L. | title=Ocean Biogeochemical Dynamics | publisher=Princeton University Press | date=2006-01-01 | isbn=978-1-4008-4907-9 | doi=10.1515/9781400849079}}</ref> Driven by [[Ocean primary production|primary production]], it produces around 50 Pg C y<sup>−1</sup> globally.<ref>{{cite journal | last1=Longhurst | first1=Alan | last2=Sathyendranath | first2=Shubha | last3=Platt | first3=Trevor | last4=Caverhill | first4=Carla | title=An estimate of global primary production in the ocean from satellite radiometer data | journal=Journal of Plankton Research | publisher=Oxford University Press (OUP) | volume=17 | issue=6 | year=1995 | issn=0142-7873 | doi=10.1093/plankt/17.6.1245 | pages=1245–1271}}</ref><ref>{{cite book | last1=Sathyendranath | first1=S. | last2=Platt | first2=T. | last3=Brewin | first3=Robert J.W. | last4=Jackson | first4=Thomas | title=Encyclopedia of Ocean Sciences | chapter=Primary Production Distribution | publisher=Elsevier | year=2019 | pages=635–640 | doi=10.1016/b978-0-12-409548-9.04304-9| isbn=9780128130827 }}</ref><ref>{{cite journal | last1=Kulk | first1=Gemma | last2=Platt | first2=Trevor | last3=Dingle | first3=James | last4=Jackson | first4=Thomas | last5=Jönsson | first5=Bror | last6=Bouman | first6=Heather | last7=Babin | first7=Marcel | last8=Brewin | first8=Robert | last9=Doblin | first9=Martina | last10=Estrada | first10=Marta | last11=Figueiras | first11=Francisco | last12=Furuya | first12=Ken | last13=González-Benítez | first13=Natalia | last14=Gudfinnsson | first14=Hafsteinn | last15=Gudmundsson | first15=Kristinn | last16=Huang | first16=Bangqin | last17=Isada | first17=Tomonori | last18=Kovač | first18=Žarko | last19=Lutz | first19=Vivian | last20=Marañón | first20=Emilio | last21=Raman | first21=Mini | last22=Richardson | first22=Katherine | last23=Rozema | first23=Patrick | last24=Poll | first24=Willem | last25=Segura | first25=Valeria | last26=Tilstone | first26=Gavin | last27=Uitz | first27=Julia | last28=Dongen-Vogels | first28=Virginie | last29=Yoshikawa | first29=Takashi | last30=Sathyendranath | first30=Shubha | title=Primary Production, an Index of Climate Change in the Ocean: Satellite-Based Estimates over Two Decades | journal=Remote Sensing | publisher=MDPI AG | volume=12 | issue=5 | date=2020-03-03 | issn=2072-4292 | doi=10.3390/rs12050826 | page=826| bibcode=2020RemS...12..826K |display-authors = 4| doi-access=free | hdl=11336/128979 | hdl-access=free }}</ref> It can be separated into living (e.g. [[phytoplankton]], [[zooplankton]], [[bacteria]]) and non-living (e.g. [[detritus]]) material. Of these, the phytoplankton carbon is particularly important, because of its role in [[marine primary production]], and also because it serves as the food resource for all the larger organisms in the [[Pelagic zone|pelagic ecosystem]].<ref name=Brewin2021 />
* [[Particulate inorganic carbon]] (PIC) is the smallest of the pools at around 0.03 Pg C.<ref>{{cite journal | last1=Hopkins | first1=Jason | last2=Henson | first2=Stephanie A. | last3=Poulton | first3=Alex J. | last4=Balch | first4=William M. | title=Regional Characteristics of the Temporal Variability in the Global Particulate Inorganic Carbon Inventory | journal=Global Biogeochemical Cycles | publisher=American Geophysical Union (AGU) | volume=33 | issue=11 | year=2019 | issn=0886-6236 | doi=10.1029/2019gb006300 | pages=1328–1338| bibcode=2019GBioC..33.1328H | s2cid=210342576 | doi-access=free }}</ref> It is present in the form of calcium carbonate (CaCO<sub>3</sub>) in particulate form, and impacts the carbonate system and pH of the seawater. Estimates for PIC production are in the region of 0.8–1.4 Pg C y<sup>−1</sup>, with at least 65% of it being dissolved in the upper [[water column]], the rest contributing to deep sediments.<ref name=Feely2004>{{cite journal | last1=Feely | first1=Richard A. | last2=Sabine | first2=Christopher L. | last3=Lee | first3=Kitack | last4=Berelson | first4=Will | last5=Kleypas | first5=Joanie | last6=Fabry | first6=Victoria J. | last7=Millero | first7=Frank J. | title=Impact of Anthropogenic CO 2 on the CaCO 3 System in the Oceans | journal=Science | publisher=American Association for the Advancement of Science (AAAS) | volume=305 | issue=5682 | date=2004-07-16 | issn=0036-8075 | doi=10.1126/science.1097329 | pages=362–366| pmid=15256664 | bibcode=2004Sci...305..362F | s2cid=31054160 }}</ref> Coccolithophores and [[foraminifera]] are estimated to be the dominant sources of PIC in the [[open ocean]].<ref>{{cite journal | last=Schiebel | first=Ralf | title=Planktic foraminiferal sedimentation and the marine calcite budget | journal=Global Biogeochemical Cycles | publisher=American Geophysical Union (AGU) | volume=16 | issue=4 | date=2002-10-24 | issn=0886-6236 | doi=10.1029/2001gb001459 | pages=3–1–3–21| bibcode=2002GBioC..16.1065S | s2cid=128737252 }}</ref><ref name=Feely2004 /> The PIC pool is of particular importance due to its role in the ocean carbonate system, and in facilitating the export of carbon to the deep ocean through the [[carbonate pump]], whereby PIC is exported out of the [[photic zone]] and deposited in the [[Marine sediment|bottom sediments]].<ref>{{cite journal | last1=Riebesell | first1=Ulf | last2=Zondervan | first2=Ingrid | last3=Rost | first3=Björn | last4=Tortell | first4=Philippe D. | last5=Zeebe | first5=Richard E. | last6=Morel | first6=François M. M. | title=Reduced calcification of marine plankton in response to increased atmospheric CO2 | journal=Nature | publisher=Springer Science and Business Media LLC | volume=407 | issue=6802 | year=2000 | issn=0028-0836 | doi=10.1038/35030078 | pages=364–367| pmid=11014189 | bibcode=2000Natur.407..364R | s2cid=4426501 | url=https://epic.awi.de/id/eprint/3784/1/Rie2000a.pdf }}</ref><ref name=Brewin2021 />
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Ca<sup>2+</sup> + 2HCO<sub>3</sub><sup>−</sup> → CaCO<sub>3</sub> + CO<sub>2</sub> + H<sub>2</sub>O
While this process does manage to fix a large amount of carbon, two units of [[alkalinity]] are sequestered for every unit of sequestered carbon.<ref name=Hain2014/><ref name="Hain et al 2010">{{cite journal|last1=Hain|first1=M.P.|last2=Sigman|first2=D.M.|last3=Haug|first3=G.H.|year=2010|title=Carbon dioxide effects of Antarctic stratification, North Atlantic Intermediate Water formation, and subantarctic nutrient drawdown during the last ice age: Diagnosis and synthesis in a geochemical box model|journal=Global Biogeochemical Cycles|volume=24|issue=4|pages=1–19|doi=10.1029/2010GB003790|bibcode=2010GBioC..24.4023H|doi-access=
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===Carbonate pump===
The carbonate pump is sometimes referred to as the
Ca<sup>2+</sup> + 2 HCO<sub>3</sub><sup>−</sup> → CaCO<sub>3</sub> + CO<sub>2</sub> + H<sub>2</sub>O
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[[File:Processes in the biological pump.webp|thumb|upright=2.2|right| {{center|'''Processes in the biological pump''' <ref name=Cavan2019 />}}{{space|8}}<small>Carbon fluxes in white boxes are in Gt C yr<sup>−1</sup> and carbon masses in dark boxes are in Gt C</small>]]
In the diagram on the right, phytoplankton convert CO<sub>2</sub>, which has dissolved from the atmosphere into the surface oceans (90 Gt yr<sup>−1</sup>), into [[particulate organic carbon]] (POC) during [[Marine primary production|primary production]] (~ 50 Gt C yr<sup>−1</sup>). Phytoplankton are then consumed by [[copepod]]s, [[krill]] and other small zooplankton grazers, which in turn are preyed upon by higher [[trophic level]]s. Any unconsumed phytoplankton form aggregates, and along with zooplankton faecal pellets, sink rapidly and are exported out of the [[mixed layer]] (< 12 Gt C yr<sup>−1</sup> 14). Krill, copepods, zooplankton and microbes intercept phytoplankton in the surface ocean and sinking detrital particles at depth, consuming and respiring this POC to CO<sub>2</sub> ([[dissolved inorganic carbon]], DIC), such that only a small proportion of surface-produced carbon sinks to the deep ocean (i.e., depths > 1000 m). As krill and smaller zooplankton feed, they also physically fragment particles into small, slower- or non-sinking pieces (via sloppy feeding, [[coprorhexy]] if fragmenting faeces),<ref>{{cite journal |doi = 10.1007/BF01313152|title = What happens to zooplankton faecal pellets? Implications for material flux|year = 1990|last1 = Lampitt|first1 = R. S.|last2 = Noji|first2 = T.|last3 = von Bodungen|first3 = B.|journal = Marine Biology|volume = 104| issue=1 |pages = 15–23| bibcode=1990MarBi.104...15L |s2cid = 86523326}}</ref> retarding POC export. This releases [[dissolved organic carbon]] (DOC) either directly from cells or indirectly via bacterial solubilisation (yellow circle around DOC). Bacteria can then [[remineralise]] the DOC to DIC (CO<sub>2</sub>, microbial gardening).<ref name=Cavan2019>Cavan, E.L., Belcher, A., Atkinson, A., Hill, S.L., Kawaguchi, S., McCormack, S., Meyer, B., Nicol, S., Ratnarajah, L., Schmidt, K. and Steinberg, D.K. (2019) "The importance of Antarctic krill in biogeochemical cycles". ''Nature communications'', '''10'''(1): 1–13. {{doi|10.1038/s41467-019-12668-7}}. [[File:CC-BY icon.svg|50px]] Modified text 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 biological carbon pump is one of the chief determinants of the vertical distribution of carbon in the oceans and therefore of the surface partial pressure of CO<sub>2</sub> governing air-sea CO<sub>2</sub> exchange.<ref>{{cite journal |doi = 10.5670/oceanog.2009.48|title = Autonomous Observations of the Ocean Biological Carbon Pump|year = 2009|last1 = Bishop|first1 = James|journal = Oceanography|volume = 22|issue = 2|pages = 182–193|doi-access = free}}</ref> It comprises phytoplankton cells, their consumers and the bacteria that assimilate their waste and plays a central role in the global carbon cycle by delivering carbon from the atmosphere to the deep sea, where it is concentrated and sequestered for centuries.<ref name=Chisholm1995 /> Photosynthesis by phytoplankton lowers the partial pressure of CO<sub>2</sub> in the upper ocean, thereby facilitating the absorption of CO<sub>2</sub> from the atmosphere by generating a steeper CO<sub>2</sub> gradient.<ref>{{cite journal |doi = 10.1126/science.290.5490.291|title = The Global Carbon Cycle: A Test of Our Knowledge of Earth as a System|year = 2000|last1 = Falkowski|first1 = P.|last2 = Scholes|first2 = R. J.|last3 = Boyle|first3 = E.|last4 = Canadell|first4 = J.|last5 = Canfield|first5 = D.|last6 = Elser|first6 = J.|last7 = Gruber|first7 = N.|last8 = Hibbard|first8 = K.|last9 = Högberg|first9 = P.|last10 = Linder|first10 = S.|last11 = MacKenzie|first11 = F. T.|last12 = Moore b|first12 = 3rd|last13 = Pedersen|first13 = T.|last14 = Rosenthal|first14 = Y.|last15 = Seitzinger|first15 = S.|last16 = Smetacek|first16 = V.|last17 = Steffen|first17 = W.|journal = Science|volume = 290|issue = 5490|pages = 291–296|pmid = 11030643|bibcode = 2000Sci...290..291F}}</ref> It also results in the formation of [[particulate organic carbon]] (POC) in the euphotic layer of the [[epipelagic zone]] (0–200 m depth). The POC is processed by microbes, zooplankton and their consumers into fecal pellets, organic aggregates (
===Marine snow===
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{{biomineralization sidebar}}
Observations have shown that fluxes of ballast minerals (calcium carbonate, opal, and lithogenic material) and organic carbon fluxes are closely correlated in the [[bathypelagic zone]]s of the ocean.<ref name=Iversen2010 /> A large fraction of particulate organic matter occurs in the form of marine snow aggregates (>0.5 mm) composed of phytoplankton, detritus, inorganic mineral grains, and fecal pellets in the ocean.<ref>{{cite journal |doi = 10.1016/0079-6611(88)90053-5|title = Characteristics, dynamics and significance of marine snow|year = 1988|last1 = Alldredge|first1 = Alice L.|last2 = Silver|first2 = Mary W.|journal = Progress in Oceanography|volume = 20|issue = 1|pages = 41–82|bibcode = 1988PrOce..20...41A}}</ref> Formation and sinking of these aggregates drive the biological carbon pump via export and sedimentation of organic matter from the surface mixed layer to the deep ocean and sediments. The fraction of organic matter that leaves the upper mixed layer of the ocean is, among other factors, determined by the sinking velocity and microbial [[remineralisation]] rate of these aggregates. Recent observations have shown that the fluxes of ballast minerals (calcium carbonate, opal, and lithogenic material) and the organic carbon fluxes are closely correlated in the bathypelagic zones of the ocean. This has led to the hypothesis that organic carbon export is determined by the presence of ballast minerals within settling aggregates.<ref name=Armstrong2002>{{cite journal |doi = 10.1016/S0967-0645(01)00101-1|title = A new, mechanistic model for organic carbon fluxes in the ocean based on the quantitative association of POC with ballast minerals|year = 2001|last1 = Armstrong|first1 = Robert A.|last2 = Lee|first2 = Cindy|last3 = Hedges|first3 = John I.|last4 = Honjo|first4 = Susumu|last5 = Wakeham|first5 = Stuart G.|journal = Deep Sea Research Part II: Topical Studies in Oceanography|volume = 49|issue = 1–3|pages = 219–236|bibcode = 2001DSRII..49..219A}}</ref><ref name=Francois2002>{{cite journal |doi = 10.1029/2001GB001722|title = Factors controlling the flux of organic carbon to the bathypelagic zone of the ocean|year = 2002|last1 = Francois|first1 = Roger|last2 = Honjo|first2 = Susumu|last3 = Krishfield|first3 = Richard|last4 = Manganini|first4 = Steve|journal = Global Biogeochemical Cycles|volume = 16|issue = 4|pages = 34-1-34-20|bibcode = 2002GBioC..16.1087F| s2cid=128876389 |doi-access = free}}</ref><ref name=Klaas2002>{{cite journal |doi = 10.1029/2001GB001765|title = Association of sinking organic matter with various types of mineral ballast in the deep sea: Implications for the rain ratio|year = 2002|last1 = Klaas|first1 = Christine|last2 = Archer|first2 = David E.|journal = Global Biogeochemical Cycles|volume = 16|issue = 4|pages = 63-1-63-14|bibcode = 2002GBioC..16.1116K|doi-access = free}}</ref><ref name=Iversen2010>{{cite journal |doi = 10.5194/bgd-7-3335-2010|title = Ballast minerals and the sinking carbon flux in the ocean: Carbon-specific respiration rates and sinking velocities of macroscopic organic aggregates (Marine snow)|last1 = Iversen|first1 = M. H.|last2 = Ploug|first2 = H.|doi-access = free}} [[File:CC-BY icon.svg|50px]] Modified text was copied from this source, which is available under a [https://creativecommons.org/licenses/by/3.0/ Creative Commons Attribution 3.0 International License].</ref>
Mineral ballasting is associated with about 60% of the flux of particulate organic carbon (POC) in the high-latitude North Atlantic, and with about 40% of the flux in the Southern Ocean.<ref>{{cite journal |doi = 10.1002/2014GL061678|title = Where is mineral ballast important for surface export of particulate organic carbon in the ocean?|year = 2014|last1 = Le Moigne|first1 = Frédéric A. C.|last2 = Pabortsava|first2 = Katsiaryna|last3 = Marcinko|first3 = Charlotte L. J.|last4 = Martin|first4 = Patrick|last5 = Sanders|first5 = Richard J.|journal = Geophysical Research Letters|volume = 41|issue = 23|pages = 8460–8468|pmid = 26074644|pmc = 4459180|bibcode = 2014GeoRL..41.8460L}}</ref> Strong correlations exist also in the deep ocean between the presence of ballast minerals and the flux of POC. This suggests ballast minerals enhance POC flux by increasing the sink rate of ballasted aggregates. Ballast minerals could additionally provide aggregated organic matter some protection from degradation.<ref>{{cite journal |doi = 10.1016/j.marchem.2015.04.009|title = Ballasting effects of smectite on aggregate formation and export from a natural plankton community|year = 2015|last1 = Iversen|first1 = Morten H.|last2 = Robert|first2 = Maya L.|journal = Marine Chemistry|volume = 175|pages = 18–27| bibcode=2015MarCh.175...18I }}</ref>
It has been proposed that organic carbon is better preserved in sinking particles due to increased aggregate density and sinking velocity when ballast minerals are present and/or via protection of the organic matter due to quantitative association to ballast minerals.<ref name=Armstrong2002 /><ref name=Francois2002 /><ref name=Klaas2002 /> In 2002, Klaas and Archer observed that about 83% of the global particulate organic carbon (POC) fluxes were associated with [[carbonate]], and suggested carbonate was a more efficient ballast mineral as compared to opal and terrigenous material. They hypothesized that the higher density of calcium carbonate compared to that of opal and the higher abundance of calcium carbonate relative to terrigenous material might be the reason for the efficient ballasting by calcium carbonate. However, the direct effects of ballast minerals on sinking velocity and degradation rates in sinking aggregates are still unclear.<ref name=Klaas2002 /><ref name=Iversen2010 />
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====Remineralisation====
[[Remineralisation]] refers to the breakdown or transformation of [[organic matter]] (those molecules derived from a biological source) into its simplest [[Inorganic compound|inorganic]] forms. These transformations form a crucial link within [[ecosystem]]s as they are responsible for liberating the energy stored in [[Organic compound|organic molecules]] and recycling matter within the system to be reused as [[nutrient]]s by other [[organism]]s.<ref name=Sarmiento2013 /> What fraction does escape remineralisation varies depending on the location. For example, in the North Sea, values of carbon deposition are ~1% of primary production<ref>{{cite journal |last1=Thomas |first1=Helmuth |last2=Bozec |first2=Yann |last3=Elkalay |first3=Khalid |last4=Baar |first4=Hein J. W. de |date=14 May 2004 |title=Enhanced Open Ocean Storage of CO2 from Shelf Sea Pumping |journal=Science |language=en |volume=304 |issue=5673 |pages=1005–1008 |doi=10.1126/science.1095491 |issn=0036-8075 |pmid=15143279 |bibcode=2004Sci...304.1005T|hdl=11370/e821600e-4560-49e8-aeec-18eeb17549e3 |s2cid=129790522 |url=https://pure.rug.nl/ws/files/9825939/2004ScienceThomas.pdf |hdl-access=free }}</ref> while that value is <0.5% in the open oceans on average.<ref>{{cite book |last=De La Rocha |first=C. L. |title=Treatise on Geochemistry |date=2006 |chapter=The Biological Pump
For most areas of the ocean, the highest rates of carbon remineralisation occur at depths between {{convert|100|-|1200|m|ft|abbr=on}} in the water column, decreasing down to about {{convert|1,200
===Key role of phytoplankton===
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{{biogeochemical cycle sidebar|marine}}
Marine phytoplankton perform half of all photosynthesis on Earth{{hsp}}<ref name="The role of temperature, cellular q">{{cite journal |doi = 10.1016/j.limno.2008.06.002|title = The role of temperature, cellular quota and nutrient concentrations for photosynthesis, growth and light–dark acclimation in phytoplankton|year = 2008|last1 = Baumert|first1 = Helmut Z.|last2 = Petzoldt|first2 = Thomas|journal = Limnologica|volume = 38|issue = 3–4|pages = 313–326|doi-access =
Marine ecosystems are a major sink for atmospheric CO<sub>2</sub> and take up similar amount of CO<sub>2</sub> as terrestrial ecosystems, currently accounting for the removal of nearly one third of anthropogenic CO<sub>2</sub> emissions from the atmosphere.<ref name="Häder2014" /><ref name=Li2012 /> The net transfer of CO<sub>2</sub> from the atmosphere to the oceans and then [[Marine sediment|sediments]], is mainly a direct consequence of the combined effect of the solubility and the biological pump.<ref name="Hülse2017">{{cite journal |doi = 10.1016/j.earscirev.2017.06.004|title = Understanding the causes and consequences of past marine carbon cycling variability through models|year = 2017|last1 = Hülse|first1 = Dominik|last2 = Arndt|first2 = Sandra|last3 = Wilson|first3 = Jamie D.|last4 = Munhoven|first4 = Guy|last5 = Ridgwell|first5 = Andy|journal = Earth-Science Reviews|volume = 171|pages = 349–382|bibcode = 2017ESRv..171..349H| hdl=1983/7035f071-71c5-48a5-91f6-a8286e386d21 |url = https://research-information.bris.ac.uk/ws/files/134880543/BioPumpInEMICS.pdf}}</ref> While the [[solubility pump]] serves to concentrate [[dissolved inorganic carbon]] (CO<sub>2</sub> plus bicarbonate and carbonate ions) in the deep oceans, the biological carbon pump (a key natural process and a major component of the global carbon cycle that regulates atmospheric CO<sub>2</sub> levels) transfers both organic and inorganic carbon fixed by [[Marine primary production|primary producers]] (phytoplankton) in the [[euphotic zone]] to the ocean interior and subsequently to the underlying sediments.<ref name="Hülse2017" /><ref name=Chisholm1995>{{cite journal |doi = 10.1029/95RG00743|title = The iron hypothesis: Basic research meets environmental policy|year = 1995|last1 = Chisholm|first1 = Sallie W.|journal = Reviews of Geophysics|volume = 33|issue = S2|pages = 1277–1286|bibcode = 1995RvGeo..33S1277C}}</ref> Thus, the biological pump takes carbon out of contact with the atmosphere for several thousand years or longer and maintains atmospheric CO<sub>2</sub> at significantly lower levels than would be the case if it did not exist.<ref>{{cite journal |doi = 10.1038/nmicrobiol.2017.58|title = Microorganisms and ocean global change|year = 2017|last1 = Hutchins|first1 = David A.|last2 = Fu|first2 = Feixue|journal = Nature Microbiology|volume = 2|issue = 6|page = 17058|pmid = 28540925|s2cid = 23357501}}</ref> An ocean without a biological pump, which transfers roughly 11 [[Gigatonne|Gt]] C yr<sup>−1</sup> into the ocean's interior, would result in atmospheric CO<sub>2</sub> levels ~400 ppm higher than present day.<ref>{{cite journal |doi = 10.1016/j.pocean.2014.05.005|title = The Biological Carbon Pump in the North Atlantic|year = 2014|last1 = Sanders|first1 = Richard|last2 = Henson|first2 = Stephanie A.|last3 = Koski|first3 = Marja|last4 = de la Rocha|first4 = Christina L.|last5 = Painter|first5 = Stuart C.|last6 = Poulton|first6 = Alex J.|last7 = Riley|first7 = Jennifer|last8 = Salihoglu|first8 = Baris|last9 = Visser|first9 = Andre|last10 = Yool|first10 = Andrew|last11 = Bellerby|first11 = Richard|last12 = Martin|first12 = Adrian P.|journal = Progress in Oceanography|volume = 129|pages = 200–218|bibcode = 2014PrOce.129..200S}}</ref><ref>{{cite journal |doi = 10.3389/fmars.2015.00077|title = Toward quantifying the response of the oceans' biological pump to climate change|year = 2015|last1 = Boyd|first1 = Philip W.|journal = Frontiers in Marine Science|volume = 2|s2cid = 16787695|doi-access = free}}</ref><ref name=Basu2018 />
Passow and Carlson defined sedimentation out of the surface layer (at approximately 100 m depth) as the "export flux" and that out of the [[mesopelagic zone]] (at approximately 1000 m depth) as the "sequestration flux".<ref name=Passow2012 /> Once carbon is transported below the mesopelagic zone, it remains in the deep sea for 100 years or longer, hence the term
In 2001, Hugh et al. expressed the efficiency of the biological pump as the amount of carbon exported from the surface layer (export production) divided by the total amount produced by photosynthesis (overall production).<ref name=Ducklow2001 /> Modelling studies by Buesseler and Boyd revealed that the overall transfer efficiency of the biological pump is determined by a combination of factors: seasonality;<ref name=Buesseler2009 /> the composition of phytoplankton species; the fragmentation of particles by zooplankton; and the solubilization of particles by microbes. In addition, the efficiency of the biological pump is also dependent on the aggregation and disaggregation of organic-rich aggregates and interaction between POC aggregates and suspended
[[File:Cyanothece sp. ATCC 51142 cell.jpg|thumb| The nitrogen fixing cyanobacteria ''[[Cyanothece]]'' sp. ATCC 51142]]
The composition of the phytoplankton community in the euphotic zone largely determines the quantity and quality of organic matter that sinks to depth.<ref name=Herndl2013>{{cite journal |doi = 10.1038/ngeo1921|title = Microbial control of the dark end of the biological pump|year = 2013|last1 = Herndl|first1 = Gerhard J.|last2 = Reinthaler|first2 = Thomas|journal = Nature Geoscience|volume = 6|issue = 9|pages = 718–724|pmid = 24707320|pmc = 3972885|bibcode = 2013NatGe...6..718H}}</ref> The main functional groups of marine phytoplankton that contribute to export production include [[nitrogen fixation|nitrogen fixers]] ([[diazotrophic]] [[cyanobacteria]]), [[silicifier]]s (diatoms) and [[calcifier]]s (coccolithophores). Each of these phytoplankton groups differ in the size and composition of their cell walls and coverings, which influence their sinking velocities.<ref name=Collins2013>{{cite journal |doi = 10.1111/eva.12120|title = Evolutionary potential of marine phytoplankton under ocean acidification|year = 2014|last1 = Collins|first1 = Sinéad|last2 = Rost|first2 = Björn|last3 = Rynearson|first3 = Tatiana A.|author-link3=Tatiana Rynearson|journal = Evolutionary Applications|volume = 7|issue = 1|pages = 140–155|pmid = 24454553|pmc = 3894903| bibcode=2014EvApp...7..140C }}</ref> For example, autotrophic picoplankton (0.2–2
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| image2 = Copepod faecal pellet production in the deep ocean.png
| alt2 =
| caption2 = {{center|'''Mesopelagic fecal pellet production'''}} On the left above, intact fecal pellets reach the deep ocean via vertical migration of zooplankton, whereas on the right fecal pellets at depth result from in situ repackaging of sinking detritus by deep-dwelling zooplankton. Actual mechanisms are likely to include both scenarios.<ref name=Belcher2017>{{cite journal |doi = 10.5194/bg-14-1511-2017|title = Copepod faecal pellet transfer through the meso- and bathypelagic layers in the Southern Ocean in spring|year = 2017|last1 = Belcher|first1 = Anna|last2 = Manno|first2 = Clara|last3 = Ward|first3 = Peter|last4 = Henson|first4 = Stephanie A.|last5 = Sanders|first5 = Richard|last6 = Tarling|first6 = Geraint A.|journal = Biogeosciences|volume = 14|issue = 6|pages = 1511–1525|bibcode = 2017BGeo...14.1511B | doi-access=free }} [[File:CC-BY icon.svg|50px]] Modified text was copied from this source, which is available under a [https://creativecommons.org/licenses/by/3.0/ Creative Commons Attribution 3.0 International License].</ref>
}}
[[File:Morphology of copepod faecal pellets.png|thumb|upright=2.1| {{center|'''Morphology of zooplankton fecal pellets{{hsp}}<ref name=Belcher2017 />'''<br />Collected from [[marine snow]] catchers (a–c) and [[sediment trap]]s (d–f).<br />Morphological classes: (a, d) round, (b, e) cylindrical, and (c, f) ovoid.<br /><small>Scale bar {{=}} 0.5 mm</small>}}]]
In addition to linking primary producers to higher trophic levels in marine food webs, zooplankton also play an important role as
Excretion and sloppy feeding (the physical breakdown of food source) make up 80% and 20% of crustacean zooplankton-mediated DOM release respectively.<ref name=Saba2011>{{cite journal |doi = 10.1016/j.jembe.2011.04.013|title = The relative importance of sloppy feeding, excretion, and fecal pellet leaching in the release of dissolved carbon and nitrogen by Acartia tonsa copepods|year = 2011|last1 = Saba|first1 = Grace K.|last2 = Steinberg|first2 = Deborah K.|last3 = Bronk|first3 = Deborah A.|journal = Journal of Experimental Marine Biology and Ecology|volume = 404|issue = 1–2|pages = 47–56| bibcode=2011JEMBE.404...47S }}</ref> In the same study, fecal pellet leaching was found to be an insignificant contributor. For protozoan grazers, DOM is released primarily through excretion and egestion and gelatinous zooplankton can also release DOM through the production of mucus. Leaching of fecal pellets can extend from hours to days after initial egestion and its effects can vary depending on food concentration and quality.<ref name=Thor2003>{{cite journal |doi = 10.3354/ame033279|title = Fate of organic carbon released from decomposing copepod fecal pellets in relation to bacterial production and ectoenzymatic activity|year = 2003|last1 = Thor|first1 = P.|last2 = Dam|first2 = HG|last3 = Rogers|first3 = DR|journal = Aquatic Microbial Ecology|volume = 33|pages = 279–288|doi-access = free}}</ref><ref name=Carlso2014>{{Cite book|url=https://books.google.com/books?id=7iKOAwAAQBAJ&q=%22Biogeochemistry+of+marine+dissolved+organic+matter%22|title=Biogeochemistry of Marine Dissolved Organic Matter|isbn=9780124071537|last1=Hansell|first1=Dennis A.|last2=Carlson|first2=Craig A.|date=2 October 2014|publisher=Academic Press }}</ref> Various factors can affect how much DOM is released from zooplankton individuals or populations.
====Fecal pellets====
The fecal pellets of zooplankton can be important vehicles for the transfer of particulate organic carbon (POC) to the deep ocean, often making large contributions to the carbon sequestration. The size distribution of the copepod community indicates high numbers of small fecal pellets are produced in the [[epipelagic]]. However, small fecal pellets are rare in the deeper layers, suggesting they are not transferred efficiently to depth. This means small fecal pellets make only minor contributions to fecal pellet fluxes in the meso- and bathypelagic, particularly in terms of carbon. In a study is focussed on the [[Scotia Sea]], which contains some of the most productive regions in the Southern Ocean, the dominant fecal pellets in the upper [[mesopelagic]] were cylindrical and elliptical, while [[ovoid]] fecal pellets were dominant in the [[bathypelagic]]. The change in fecal pellet morphology, as well as size distribution, points to the repacking of surface fecal pellets in the mesopelagic and in situ production in the lower meso- and bathypelagic, which may be augmented by inputs of fecal pellets via zooplankton [[Diel vertical migration|vertical migrations]]. This suggests the flux of carbon to the deeper layers within the Southern Ocean is strongly modulated by meso- and bathypelagic zooplankton, meaning that the community structure in these zones has a major impact on the efficiency of the fecal pellet transfer to ocean depths.<ref name=Belcher2017 />
[[Absorption efficiency]] (AE) is the proportion of food absorbed by plankton that determines how available the consumed organic materials are in meeting the required physiological demands.<ref name=Steinberg12017 /> Depending on the feeding rate and prey composition, variations in AE may lead to variations in fecal pellet production, and thus regulates how much organic material is recycled back to the marine environment. Low feeding rates typically lead to high AE and small, dense pellets, while high feeding rates typically lead to low AE and larger pellets with more organic content. Another contributing factor to DOM release is respiration rate. Physical factors such as oxygen availability, pH, and light conditions may affect overall oxygen consumption and how much carbon is loss from zooplankton in the form of respired CO<sub>2</sub>. The relative sizes of zooplankton and prey also mediate how much carbon is released via sloppy feeding. Smaller prey are ingested whole, whereas larger prey may be fed on more
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====Jelly fall====
[[File:Gelatinous zooplankton biological pump.png|thumb|upright=2| {{center|'''Gelatinous zooplankton biological pump'''}} How [[jelly carbon]] fits in the biological pump. A schematic representation of the biological pump and the biogeochemical processes that remove elements from the surface ocean by sinking biogenic particles including jelly carbon.<ref name=Lebrato2019>{{cite journal |title = Sinking of Gelatinous Zooplankton Biomass Increases Deep Carbon Transfer Efficiency Globally|year = 2019|doi = 10.1029/2019GB006265|last1 = Lebrato|first1 = Mario|last2 = Pahlow|first2 = Markus|last3 = Frost|first3 = Jessica R.|last4 = Küter|first4 = Marie|last5 = Jesus Mendes|first5 = Pedro|last6 = Molinero|first6 =
{{see also|Jelly falls}}
[[Jelly-falls]] are marine [[Carbon cycle|carbon cycling]] events whereby [[gelatinous zooplankton]], primarily [[cnidaria]]ns, sink to the seafloor and enhance carbon and nitrogen fluxes via rapidly sinking [[particulate organic matter]].<ref name="Lebrato et al. 2012">{{Cite journal |last1=Lebrato |first1=Mario |last2=Pitt |first2=Kylie A. |last3=Sweetman |first3=Andrew K. |last4=Jones |first4=Daniel O. B. |last5=Cartes |first5=Joan E. |last6=Oschlies |first6=Andreas |last7=Condon |first7=Robert H. |last8=Molinero |first8=Juan Carlos |last9=Adler |first9=Laetitia |name-list-style=amp |date=2012 |title=Jelly-falls historic and recent observations: a review to drive future research directions |journal=Hydrobiologia |volume=690 |issue=1 |pages=227–245 |doi=10.1007/s10750-012-1046-8|s2cid=15428213 |url=https://zenodo.org/record/3442888 }}</ref> These events provide nutrition to [[Benthic zone|benthic]] [[megafauna]] and [[bacteria]].<ref>{{Cite journal |last1=Lebrato |first1=M. |last2=Jones |first2=D. O. B. |name-list-style=amp |date=2009 |title=Mass deposition event of ''Pyrosoma atlanticum'' carcasses off Ivory Coast (West Africa) |journal=Limnology and Oceanography |volume=54 |issue=4 |pages=1197–1209 |doi=10.4319/lo.2009.54.4.1197|bibcode=2009LimOc..54.1197L |url=http://oceanrep.geomar.de/3017/1/1197.pdf |doi-access=free }}</ref><ref name="Sweetman and Chapman 2011">{{Cite journal |last1=Sweetman |first1=Andrew K. |last2=Chapman |first2=Annelise |name-list-style=amp |date=2011 |title=First observations of jelly-falls at the seafloor in a deep-sea fjord |journal=Deep Sea Research Part I: Oceanographic Research Papers |volume=58 |issue=12 |pages=1206–1211 |doi=10.1016/j.dsr.2011.08.006|bibcode=2011DSRI...58.1206S }}</ref> Jelly-falls have been implicated as a major
[[File:Jellyfish swarm.jpg|thumb|upright=1.3|left| Jellyfish are easy to capture and digest and may be more important as carbon sinks than was previously thought.<ref name=Hays2018>{{cite journal |doi = 10.1016/j.tree.2018.09.001|title = A Paradigm Shift in the Trophic Importance of Jellyfish?|year = 2018|last1 = Hays|first1 = Graeme C.|last2 = Doyle|first2 = Thomas K.|last3 = Houghton|first3 = Jonathan D.R.|journal = Trends in Ecology & Evolution|volume = 33|issue = 11|pages = 874–884|pmid = 30245075| bibcode=2018TEcoE..33..874H |s2cid = 52336522|url = https://pure.qub.ac.uk/en/publications/a-paradigm-shift-in-the-trophic-importance-of-jellyfish(6158fa15-32f8-4167-9574-dbc08266b588).html|author1-link = Graeme Hays}}</ref>]]
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Without vertical migration the biological pump wouldn't be nearly as efficient. Organisms migrate up to feed at night so when they migrate back to depth during the day they defecate large sinking fecal pellets. Whilst some larger fecal pellets can sink quite fast, the speed that organisms move back to depth is still faster. At night organisms are in the top 100 metres of the water column, but during the day they move down to between 800 and 1000 metres. If organisms were to defecate at the surface it would take the fecal pellets days to reach the depth that they reach in a matter of hours. Therefore, by releasing fecal pellets at depth they have almost 1000 metres less to travel to get to the deep ocean. This is something known as [[active transport]]. The organisms are playing a more active role in moving organic matter down to depths. Because a large majority of the deep sea, especially marine microbes, depends on nutrients falling down, the quicker they can reach the ocean floor the better.<ref name=Steinberg2002 />
[[Zooplankton]] and [[salps]] play a large role in the active transport of fecal pellets. 15–50% of zooplankton biomass is estimated to migrate, accounting for the transport of 5–45% of particulate organic nitrogen to depth.<ref name=Steinberg2002 /> Salps are large gelatinous plankton that can vertically migrate 800 metres and eat large amounts of food at the surface. They have a very long gut retention time, so fecal pellets usually are released at maximum depth. Salps are also known for having some of the largest fecal pellets. Because of this they have a very fast sinking rate, small [[detritus]] particles are known to aggregate on them. This makes them sink that much faster. So while currently there is still much research being done on why organisms vertically migrate, it is clear that vertical migration plays a large role in the active transport of dissolved organic matter to depth.<ref name="Wiebe, P.H">{{cite journal | last=Wiebe | first=P.H |author2=L.P. Madin |author3=L.R. Haury |author4=G.R. Harbison |author5=L.M. Philbin |year=1979 | title=Diel Vertical Migration by Salpa aspera and its potential for large-scale particulate organic matter transport to the deep-sea | journal=Marine Biology | volume=53 | pages=249–255 | doi=10.1007/BF00952433 | issue=3| bibcode=1979MarBi..53..249W | s2cid=85127670 }}</ref>
====Lipid pump====
{{main|Lipid pump}}
The lipid pump sequesters [[carbon]] from the ocean's surface to deeper waters via [[lipid]]s associated with [[overwintering]] vertically migratory [[zooplankton]]. Lipids are a class of [[hydrocarbon]] rich, [[nitrogen]] and [[phosphorus]] deficient compounds essential for cellular structures. The lipid associated carbon enters the [[Deep sea|deep ocean]] as carbon dioxide produced by [[Respiration (physiology)|respiration]] of lipid reserves and as organic matter from the mortality of zooplankton. Compared to the more general biological pump, the lipid pump also results in a lipid shunt, where other [[nutrient]]s like nitrogen and phosphorus that are consumed in excess must be [[Excretion|excreted]] back to the surface environment, and thus are not removed from the surface mixed layer of the ocean.<ref name=":1">{{Cite journal|last1=Jónasdóttir|first1=Sigrún Huld|last2=Visser|first2=André W.|last3=Richardson|first3=Katherine|last4=Heath|first4=Michael R.|date=2015-09-29|title=Seasonal copepod lipid pump promotes carbon sequestration in the deep North Atlantic|journal=Proceedings of the National Academy of Sciences|language=en|volume=112|issue=39|pages=12122–12126|doi=10.1073/pnas.1512110112|issn=0027-8424|pmc=4593097|pmid=26338976|doi-access=free}}</ref> This means that the carbon transported by the lipid pump does not limit the availability of essential nutrients in the ocean surface. [[Carbon sequestration]] via the lipid pump is therefore decoupled from nutrient removal, allowing carbon uptake by oceanic primary production to continue. In the Biological Pump, nutrient removal is always coupled to carbon sequestration; primary production is limited as carbon and nutrients are transported to depth together in the form of organic matter.<ref name=":1" /> The contribution of the lipid pump to the sequestering of carbon in the deeper waters of the ocean can be substantial: the carbon transported below 1,000 metres (3,300 ft) by [[copepod]]s of the genus ''[[Calanus]]'' in the [[Arctic Ocean]] almost equals that transported below the same depth annually by [[Particulate organic matter|particulate organic carbon]] (POC) in this region.<ref name=":2">{{Cite journal|last=Visser|first=Andre|date=2 March 2017|title=Calanus hyperboreus and the lipid pump|url=https://aslopubs.onlinelibrary.wiley.com/doi/full/10.1002/lno.10492|journal=Limnology and Oceanography|volume=62|issue=3|pages=1155–1165|doi=10.1002/lno.10492|bibcode=2017LimOc..62.1155V|s2cid=51989153 }}</ref> A significant fraction of this transported carbon would not return to the surface due to respiration and mortality. Research is ongoing to more precisely estimate the amount that remains at depth.<ref name=":1" /><ref name=":2" /><ref name=":3">{{Cite journal|last1=Steinberg|first1=Deborah K.|last2=Landry|first2=Michael R.|date=2017-01-03|title=Zooplankton and the Ocean Carbon Cycle|url=https://www.annualreviews.org/doi/10.1146/annurev-marine-010814-015924|journal=Annual Review of Marine Science|volume=9|issue=1|pages=413–444|doi=10.1146/annurev-marine-010814-015924|pmid=27814033|bibcode=2017ARMS....9..413S|issn=1941-1405}}</ref> The export rate of the lipid pump may vary from 1–9.3 g C m<sup>−2</sup> y<sup>−1</sup> across temperate and subpolar regions containing seasonally-migrating zooplankton.<ref name=":3" /> The role of zooplankton, and particularly copepods, in the [[food web]] is crucial to the survival of higher [[trophic level]] organisms whose primary source of [[nutrition]] is copepods. With warming oceans and increasing melting of [[ice cap]]s due to [[climate change]], the organisms associated with the lipid pump may be affected, thus influencing the survival of many commercially important [[fish]] and [[Endangered species|endangered]] [[marine mammal]]s.<ref>{{Cite journal|last1=Parent|first1=Genevieve J.|last2=Plourde|first2=Stephane|last3=Turgeon|first3=Julie|date=2011-11-01|title=Overlapping size ranges of Calanus spp. off the Canadian Arctic and Atlantic Coasts: impact on species' abundances
===Bioluminescent shunt===
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[[Luminous bacteria]] in light organ symbioses are successively acquired by host (squid, fish) from the seawater while they are juveniles, then regularly released into the ocean.<ref name=Tanet2020>{{cite journal |doi = 10.5194/bg-17-3757-2020|title = Reviews and syntheses: Bacterial bioluminescence – ecology and impact in the biological carbon pump|year = 2020|last1 = Tanet|first1 = Lisa|last2 = Martini|first2 = Séverine|last3 = Casalot|first3 = Laurie|last4 = Tamburini|first4 = Christian|journal = Biogeosciences|volume = 17|issue = 14|pages = 3757–3778|bibcode = 2020BGeo...17.3757T|doi-access = free}} [[File:CC-BY icon.svg|50px]] Modified text 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>
In the diagram on the right, depending on the light organ position, luminous bacteria are released from their guts into [[fecal pellet]]s or directly into the seawater (step 1). Motile luminous bacteria colonize organic matter sinking along the [[water column]]. Bioluminescent bacteria colonising fecal pellets and particles influence zooplankton consumption rates. Such visual markers increase detection (
[[Filter feeder]]s also aggregate sinking organic matter without particular visual detection and selection of luminous matter. [[Diel vertical migration|Diel (and seasonal) vertical migrators]] feeding on luminous food metabolize and release glowing fecal pellets from the surface to the mesopelagic zone (step 4). This implies bioluminescent bacteria dispersion at large spatial scales, for zooplankton or even some fish actively swimming long distances. Luminous bacteria attached to particles sink down to the seafloor, and sediment can be resuspended by oceanographic physical conditions (step 5) and consumed by epi-benthic organisms. Instruments are (a) plankton net, (b) fish net, (c) [[Niskin bottle|Niskin water sampler]], (d) bathyphotometer, (e) [[sediment trap]]s, (f) [[autonomous underwater vehicle]]s, (g) [[photomultiplier]] module, (h) astrophysics optical modules [[ANTARES (telescope)|ANTARES]] and (i–j) [[remotely operated vehicle]]s.<ref name=Tanet2020 />
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Effects of different water temperatures on organic carbon export and remineralization: more carbon is sequestered when temperature is colder compared to when is warmer.<ref name=Boscolo-Galazzo2018 />]]{{see also|Effects of climate change on oceans}}
Changes in land use, the [[combustion]] of [[fossil fuel]]s, and the production of [[cement]] have led to an increase in CO<sub>2</sub> concentration in the atmosphere. At present, about one third (approximately 2 Pg C y<sup>−1</sup> = 2 × 10<sup>15</sup> grams of carbon per year)<ref name="tak02">{{cite journal|doi=10.1016/S0967-0645(02)00003-6 |title=Global sea–air CO2 flux based on climatological surface ocean pCO2, and seasonal biological and temperature effects |year=2002 |last1=Takahashi |first1=Taro |last2=Sutherland |first2=Stewart C. |last3=Sweeney |first3=Colm |last4=Poisson |first4=Alain |last5=Metzl |first5=Nicolas |last6=Tilbrook |first6=Bronte |last7=Bates |first7=Nicolas |last8=Wanninkhof |first8=Rik |last9=Feely |first9=Richard A. |last10=Sabine |first10=Christopher |last11=Olafsson |first11=Jon |last12=Nojiri |first12=Yukihiro |journal=Deep Sea Research Part II: Topical Studies in Oceanography |volume=49 |issue=9–10 |pages=1601–1622 |bibcode=2002DSRII..49.1601T }}</ref><ref name="orr97">Orr, J. C., E. Maier-Reimer, U. Mikolajewicz, P. Monfray, J. L. Sarmiento, J. R. Toggweiler, N. K. Taylor, J. Palmer, N. Gruber, C. L. Sabine, C. Le Quéré, R. M. Key and J. Boutin (2001). Estimates of anthropogenic carbon uptake from four three-dimensional global ocean models. ''Global Biogeochem. Cycles'' '''15''', 43–60.</ref>{{Unreliable source?|date=May 2021|reason=rather old sources}} of anthropogenic emissions of CO<sub>2</sub> may be entering the ocean, but this is quite uncertain.<ref>{{Cite web|title=Study reveals uncertainty in how much carbon the ocean absorbs over time|url=https://news.mit.edu/2021/how-much-carbon-ocean-absorbs-0405|access-date=2021-05-07|website=MIT News {{!}} Massachusetts Institute of Technology|date=5 April 2021 |language=en}}</ref> Some research suggests that a link between elevated CO<sub>2</sub> and marine primary production exists.<ref>Riebesell, U., Schulz, K.G., Bellerby, R.G.J., Botros, M., Fritsche, P., Meyerhöfer, M., Neill, C., Nondal, G., Oschlies, A., Wohlers, J. and Zöllner, E. (2007). [http://www.nature.com/nature/journal/v450/n7169/abs/nature06267.html Enhanced biological carbon consumption in a high CO<sub>2</sub> ocean.] ''[[Nature (journal)|Nature]]'' '''450''', 545–548.</ref>
[[File:Arctic carbon fluxes influenced by sea ice decline and permafrost thaw.webp|thumb|upright=2.0| {{center|Arctic carbon fluxes influenced by sea ice decline<br />and permafrost thaw{{hsp}}<ref name=Parmentier2017>{{cite journal |doi = 10.1007/s13280-016-0872-8|title = A synthesis of the arctic terrestrial and marine carbon cycles under pressure from a dwindling cryosphere|year = 2017|last1 = Parmentier|first1 = Frans-Jan W.|last2 = Christensen|first2 = Torben R.|last3 = Rysgaard|first3 = Søren|last4 = Bendtsen|first4 = Jørgen|last5 = Glud|first5 = Ronnie N.|last6 = Else|first6 = Brent|last7 = Van Huissteden|first7 = Jacobus|last8 = Sachs|first8 = Torsten|last9 = Vonk|first9 = Jorien E.|last10 = Sejr|first10 = Mikael K.|journal = Ambio|volume = 46|issue = Suppl 1|pages = 53–69|pmid = 28116680|pmc = 5258664| bibcode=2017Ambio..46S..53P }} [[File:CC-BY icon.svg|50px]] Modified text 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 name=Parmentier2013>{{cite journal |doi = 10.1038/nclimate1784|title = The impact of lower sea-ice extent on Arctic greenhouse-gas exchange|year = 2013|last1 = Parmentier|first1 = Frans-Jan W.|last2 = Christensen|first2 = Torben R.|last3 = Sørensen|first3 = Lise Lotte|last4 = Rysgaard|first4 = Søren|last5 = McGuire|first5 = A. David|last6 = Miller|first6 = Paul A.|last7 = Walker|first7 = Donald A.|journal = Nature Climate Change|volume = 3|issue = 3|pages = 195–202|bibcode = 2013NatCC...3..195P}}</ref>}}]]
[[File:WOA05 GLODAP invt aco2 AYool.png|thumb|upright=2.0| Global estimate of the vertically integrated anthropogenic [[dissolved inorganic carbon]] (DIC) in the ocean in recent times (1990s)]]
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==Monitoring==
[[File:Monitoring the ocean biological carbon pump.jpg|thumb|upright=2|{{center|'''Monitoring the ocean biological carbon pump'''{{hsp}}<ref name=Brewin2021 /> Pools, fluxes and processes that form the ocean biological carbon pump, and current methods used to monitor them. Bold black text and thick black arrows represent the key export pathways and interactions with other domains (land and atmosphere). Global stocks of the different carbon pools in the ocean are given in the box on the left; the four major kinds of pools – [[Dissolved inorganic carbon|DIC]], [[Dissolved organic carbon|DOC]], [[Particulate organic carbon|POC]] and [[Particulate inorganic carbon|PIC]] – are given in different colours.}}
{{center|<small>This figure has been inspired by, and builds on, two earlier figures, one from the [[CEOS]] carbon from space report{{hsp}}<ref>{{cite journal | last1=Siegel | first1=David A. | last2=Buesseler | first2=Ken O. | last3=Behrenfeld | first3=Michael J. | last4=Benitez-Nelson | first4=Claudia R. | last5=Boss | first5=Emmanuel | last6=Brzezinski | first6=Mark A. | last7=Burd | first7=Adrian | last8=Carlson | first8=Craig A. | last9=D'Asaro | first9=Eric A. | last10=Doney | first10=Scott C. | last11=Perry | first11=Mary J. | last12=Stanley | first12=Rachel H. R. | last13=Steinberg | first13=Deborah K. | title=Prediction of the Export and Fate of Global Ocean Net Primary Production: The EXPORTS Science Plan | journal=Frontiers in Marine Science | publisher=Frontiers Media SA | volume=3 | date=2016-03-08 | issn=2296-7745 | doi=10.3389/fmars.2016.00022| doi-access=free }}</ref> and the other from the NASA EXPORTS plan.<ref>[[Committee on Earth Observation Satellites]] (2014) "CEOS strategy for carbon observations from space". Response to the [[Group on Earth Observations]] (GEO) carbon strategy. Printed in Japan by JAXA and I&A Corporation.</ref></small>}}]]
{{see also|Remote sensing (oceanography)}}
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==References==
{{reflist}}
{{microorganisms}}
{{DEFAULTSORT:Biological Pump}}
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