Editing Plankton (section)

== Ecological significance ==

===Food chain===
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{{see also|marine food web}}

As well as representing the lower levels of a [[food chain]] that supports commercially important [[Fishery|fisheries]], plankton [[ecosystem]]s play a role in the [[biogeochemical cycle]]s of many important [[chemical element]]s, including the ocean's [[carbon cycle]].<ref>{{cite journal |last= Falkowski |first=Paul G. |year=1994 |url= ftp://marine.calpoly.edu/Needles/SPRING%2009/papers/2-Falkowski.pdf |title=The role of phytoplankton photosynthesis in global biogeochemical cycles |journal=Photosynthesis Research |volume=39 |issue=3 |pages=235–258 |doi= 10.1007/BF00014586 |pmid=24311124 |bibcode=1994PhoRe..39..235F |s2cid=12129871 }}{{dead link|date=December 2017 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> Fish larvae mainly eat zooplankton, which in turn eat phytoplankton<ref name="sciencedirect.com">{{Cite journal |last1=James |first1=Alex |last2=Pitchford |first2=Jonathan W. |last3=Brindley |first3=John |date=2003-02-01 |title=The relationship between plankton blooms, the hatching of fish larvae, and recruitment |url=https://www.sciencedirect.com/science/article/pii/S0304380002003113 |journal=Ecological Modelling |language=en |volume=160 |issue=1 |pages=77–90 |doi=10.1016/S0304-3800(02)00311-3 |bibcode=2003EcMod.160...77J |issn=0304-3800}}</ref>

===Carbon cycle===
{{see also|ocean carbon cycle|biological pump}}

Primarily by grazing on phytoplankton, zooplankton provide [[carbon]] to the planktic [[foodweb]], either [[Cellular respiration|respiring]] it to provide [[metabolism|metabolic]] energy, or upon death as [[Biomass (ecology)|biomass]] or [[detritus]]. Organic material tends to be [[density|denser]] than [[seawater]], so it sinks into open ocean ecosystems away from the coastlines, transporting carbon along with it. This process, called the [[biological pump]], is one reason that oceans constitute the largest [[carbon sink]] on [[Earth science|Earth]]. However, it has been shown to be influenced by increments of temperature.<ref>{{cite journal |last1= Sarmento |first1= H. |last2= Montoya |first2= JM. |last3= Vázquez-Domínguez |first3= E. |last4= Vaqué |first4= D.|last5= Gasol |first5= JM. |year= 2010 |title= Warming effects on marine microbial food web processes: how far can we go when it comes to predictions? |pmc= 2880134 |journal= Philosophical Transactions of the Royal Society B: Biological Sciences |volume= 365 |issue=1549 |pages= 2137–2149 |doi= 10.1098/rstb.2010.0045 |pmid= 20513721 }}</ref><ref>{{cite journal |last1= Vázquez-Domínguez |first1= E. |last2= Vaqué |first2= D. |last3= Gasol |first3= JM. |year=2007 |title= Ocean warming enhances respiration and carbon demand of coastal microbial plankton. |journal= Global Change Biology |volume= 13 |issue=7 |pages= 1327–1334 |doi= 10.1111/j.1365-2486.2007.01377.x |bibcode= 2007GCBio..13.1327V |hdl= 10261/15731 |s2cid= 8721854 |hdl-access= free }}</ref><ref>{{cite journal |last1= Vázquez-Domínguez |first1= E. |last2= Vaqué |first2= D. |last3= Gasol |first3= JM. |year= 2012 |title= Temperature effects on the heterotrophic bacteria, heterotrophic nanoflagellates, and microbial top predators of NW Mediterranean. |journal= Aquatic Microbial Ecology |volume= 67 |issue=2 |pages= 107–121 |doi= 10.3354/ame01583 |doi-access= free |hdl= 10261/95626 |hdl-access= free }}</ref><ref>{{cite journal |last1= Mazuecos |first1= E. |last2= Arístegui |first2=J. |last3= Vázquez-Domínguez |first3= E. |last4= Ortega-Retuerta |first4= E. |last5= Gasol |first5= JM. |last6= Reche |first6= I. |year=2012 |title= Temperature control of microbial respiration and growth efficiency in the mesopelagic zone of the South Atlantic and Indian Oceans. |journal= Deep Sea Research Part I: Oceanographic Research Papers  |volume= 95 |issue=2 |pages= 131–138 |doi= 10.3354/ame01583 |doi-access= free |hdl= 10261/95626 |hdl-access= free }}</ref> In 2019, a study indicated that at ongoing rates of [[Ocean acidification|seawater acidification]], Antarctic phytoplanktons could become smaller and less effective at storing carbon before the end of the century.<ref>{{Cite web|url=https://phys.org/news/2019-08-acid-oceans-plankton-fueling-faster.html|title=Acid oceans are shrinking plankton, fueling faster climate change|last1=Petrou|first1=Katherina|last2=Nielsen|first2=Daniel|date=2019-08-27|website=phys.org|language=en-us|access-date=2019-09-07}}</ref>

It might be possible to increase the ocean's uptake of [[Carbon dioxide#In the Earth.27s atmosphere|carbon dioxide]] ({{chem|C|O|2}}) generated through [[Human impact on the environment|human activities]] by increasing plankton production through [[iron fertilization]] – introducing amounts of [[iron]] into the ocean. However, this technique may not be practical at a large scale. Ocean [[Anoxic sea water|oxygen depletion]] and resultant [[methanogen|methane production]] (caused by the excess production [[remineralisation|remineralising]] at depth) is one potential drawback.<ref>{{Cite journal   
| last1 = Chisholm |first1 = S.W. | year=2001   
| title = Dis-crediting ocean fertilization
| journal= Science | volume=294 | issue= 5541
| pages= 309–310 |doi= 10.1126/science.1065349
| pmid = 11598285
| last2 = Falkowski | first2 = PG   
| last3 = Cullen | first3 = JJ
|s2cid = 130687109 | display-authors = 1   
}}</ref><ref>{{Cite journal
 |last         = Aumont
 |first        = O.
 |author2      = Bopp, L.
 |year         = 2006
 |title        = Globalizing results from ocean ''in situ'' iron fertilization studies
 |journal      = Global Biogeochemical Cycles
 |volume       = 20
 |issue        = 2
 |doi          = 10.1029/2005GB002591
 |page         = GB2017
 |bibcode      = 2006GBioC..20.2017A
 |doi-access   = free
 }}</ref>

===Oxygen production===
{{see also|oxygen cycle}}

[[Phytoplankton]] absorb energy from the Sun and nutrients from the water to produce their own nourishment or energy. In the process of [[photosynthesis]], phytoplankton release molecular [[oxygen]] ({{chem|O|2}}) into the water as a waste byproduct. It is estimated that about 50% of the world's oxygen is produced via phytoplankton photosynthesis.<ref name="NalGeo">{{cite news |last=Roach |first=John |url= http://news.nationalgeographic.com/news/2004/06/0607_040607_phytoplankton.html |archive-url= https://web.archive.org/web/20040608065449/http://news.nationalgeographic.com/news/2004/06/0607_040607_phytoplankton.html |url-status= dead |archive-date= June 8, 2004 |title=Source of Half Earth's Oxygen Gets Little Credit |work=National Geographic News |date=June 7, 2004 |access-date=2016-04-04 }}</ref> The rest is produced via photosynthesis on land by [[plant]]s.<ref name="NalGeo"/> Furthermore, phytoplankton photosynthesis has controlled the atmospheric [[Carbon dioxide in Earth's atmosphere|{{chem|C|O|2}}]]/[[Oxygen#Build-up in the atmosphere|{{chem|O|2}}]] balance since the early [[Precambrian]] Eon.<ref name="Tappan">{{cite journal |title=Primary production, isotopes, extinctions and the atmosphere |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |date=April 1968 |last=Tappan |first=Helen |volume=4 |issue=3 |pages=187–210 |doi=10.1016/0031-0182(68)90047-3 |bibcode= 1968PPP.....4..187T }}</ref>

===Absorption efficiency===
{{see also|biological pump}}

The ''absorption efficiency'' (AE) of plankton is the proportion of food absorbed by the plankton that determines how available the consumed organic materials are in meeting the required physiological demands.<ref name=Steinberg12017>{{cite journal |doi = 10.1146/annurev-marine-010814-015924|title = Zooplankton and the Ocean Carbon Cycle|year = 2017|last1 = Steinberg|first1 = Deborah K.|last2 = Landry|first2 = Michael R.|journal = Annual Review of Marine Science|volume = 9|pages = 413–444|pmid = 27814033|bibcode = 2017ARMS....9..413S}}</ref> Depending on the feeding rate and prey composition, variations in absorption efficiency 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 absorption efficiency and small, dense pellets, while high feeding rates typically lead to low absorption efficiency and larger pellets with more organic content. Another contributing factor to [[dissolved organic matter]] (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 {{CO2}}. 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 "sloppily", that is more biomatter is released through inefficient consumption.<ref name="Møller2005">{{cite journal |doi = 10.1093/plankt/fbh147|title = Sloppy feeding in marine copepods: Prey-size-dependent production of dissolved organic carbon|year = 2004|last1 = Moller|first1 = E. F.|journal = Journal of Plankton Research|volume = 27|pages = 27–35|doi-access = free}}</ref><ref name="Møller2007">{{cite journal |doi = 10.4319/lo.2007.52.1.0079|title = Production of dissolved organic carbon by sloppy feeding in the copepods Acartia tonsa, Centropages typicus, and Temora longicornis|year = 2007|last1 = Møller|first1 = Eva Friis|journal = Limnology and Oceanography|volume = 52|issue = 1|pages = 79–84|bibcode = 2007LimOc..52...79M|doi-access = free}}</ref> There is also evidence that diet composition can impact nutrient release, with carnivorous diets releasing more [[dissolved organic carbon]] (DOC) and ammonium than omnivorous diets.<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>