Biological pump: Difference between revisions

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 10.2 [[gigatonne]]s of carbon every year into the ocean's interior and a total of 1300 gigatonnes carbon over an average 127 years.<ref>{{cite journal |last1=Nowicki |first1=Michael |last2=DeVries |first2=Tim |last3=Siegel |first3=David A. |title=Quantifying the Carbon Export and Sequestration Pathways of the Ocean's Biological Carbon Pump |journal=Global Biogeochemical Cycles |date=March 2022 |volume=36 |issue=3 |doi=10.1029/2021GB007083|bibcode=2022GBioC..3607083N |s2cid=246458736 }}</ref> This takes carbon out of contact with the atmosphere for several thousand years or longer. An ocean without a biological pump would result in atmospheric carbon dioxide levels about 400 [[Parts per million|ppm]] higher than the present day.

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}} [[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 (CO₂), [[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 CO₂ is taken up in the process of photosynthesis, and can reduce the partial pressure of CO₂ in the seawater, favouring drawdown from the atmosphere. The reverse process respiration, releases CO₂ back into the water, can increase partial pressure of CO₂ 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 CO₂ 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 | title=Coccolithophores | chapter=Coccolithophores and the biological pump: responses to environmental changes | publisher=Springer Berlin Heidelberg | publication-place=Berlin, Heidelberg | year=2004 | isbn=978-3-642-06016-8 | doi=10.1007/978-3-662-06278-4_5}}</ref><ref>{{cite journal | last=Zeebe | first=Richard E. | title=History of Seawater Carbonate Chemistry, Atmospheric CO2, and Ocean Acidification | journal=Annual Review of Earth and Planetary Sciences | publisher=Annual Reviews | volume=40 | issue=1 | date=2012-05-30 | issn=0084-6597 | doi=10.1146/annurev-earth-042711-105521 | pages=141–165| bibcode=2012AREPS..40..141Z }}</ref><ref name=Brewin2021 />

* [[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⁻¹).<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⁻¹).<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 }}</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⁻¹ 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 }}</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 }}</ref> It is present in the form of calcium carbonate (CaCO₃) 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⁻¹, 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 />

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>

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 = free}}</ref> and directly influence global biogeochemical cycles and the climate, yet how they will respond to future global change is unknown. Carbon dioxide is one of the principal drivers of global change and has been identified as one of the major challenges in the 21st century.<ref>{{cite journal |doi = 10.1016/j.ijggc.2012.07.010|title = Current status and challenges on microalgae-based carbon capture|year = 2012|last1 = Lam|first1 = Man Kee|last2 = Lee|first2 = Keat Teong|last3 = Mohamed|first3 = Abdul Rahman|journal = International Journal of Greenhouse Gas Control|volume = 10|pages = 456–469| bibcode=2012IJGGC..10..456L }}</ref> Carbon dioxide (CO₂) generated during anthropogenic activities such as deforestation and burning of fossil fuels for energy generation rapidly dissolves in the surface ocean and lowers seawater pH, while CO₂ remaining in the atmosphere increases global temperatures and leads to increased [[Ocean stratification|ocean thermal stratification]]. While CO₂ concentration in the atmosphere is estimated to be about 270 [[Parts per million|ppm]] before the industrial revolution, it has currently increased to about 400 ppm{{hsp}}<ref name="Häder2014">{{cite journal |doi = 10.1039/C3PP50418B|title = Productivity of aquatic primary producers under global climate change|year = 2014|last1 = Häder|first1 = Donat-P.|last2 = Villafañe|first2 = Virginia E.|last3 = Helbling|first3 = E. Walter|journal = Photochem. Photobiol. Sci.|volume = 13|issue = 10|pages = 1370–1392|pmid = 25191675}}</ref> and is expected to reach 800–1000 ppm by the end of this century according to the "business as usual" CO₂ emission scenario.<ref name=Li2012>{{cite journal |doi = 10.1371/journal.pone.0051590|title = Interactive Effects of Ocean Acidification and Nitrogen-Limitation on the Diatom Phaeodactylum tricornutum|year = 2012|last1 = Li|first1 = Wei|last2 = Gao|first2 = Kunshan|last3 = Beardall|first3 = John|journal = PLOS ONE|volume = 7|issue = 12|pages = e51590|pmid = 23236517|pmc = 3517544|bibcode = 2012PLoSO...751590L|doi-access = free}}</ref><ref name=Basu2018 />

Marine ecosystems are a major sink for atmospheric CO₂ and take up similar amount of CO₂ as terrestrial ecosystems, currently accounting for the removal of nearly one third of anthropogenic CO₂ emissions from the atmosphere.<ref name="Häder2014" /><ref name=Li2012 /> The net transfer of CO₂ 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]] (CO₂ 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 CO₂ 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 CO₂ 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⁻¹ into the ocean's interior, would result in atmospheric CO₂ 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 />