Editing Zooplankton (section)

=== Sloppy feeding and release of DOM ===
{{see also|Zooplankton grazing}}
[[File:Sloppy feeding by zooplankton.jpg|thumb|right|upright=1.3| {{center|'''Sloppy feeding by zooplankton'''<br />DOC {{=}} [[dissolved organic carbon]]<br />POC {{=}} [[particulate organic carbon]]<br /><small>Adapted from Møller et al. (2005),<ref name="Møller2003">{{cite journal |doi = 10.3354/meps262185|title = Production of DOC by ''Calanus finmarchicus'', ''C. Glacialis'' and ''C. Hyperboreus'' through sloppy feeding and leakage from fecal pellets|year = 2003|last1 = Møller|first1 = EF|last2 = Thor|first2 = P.|last3 = Nielsen|first3 = TG|journal = Marine Ecology Progress Series|volume = 262|pages = 185–191|bibcode = 2003MEPS..262..185M|doi-access = free}}</ref><br />Saba et al. (2009)<ref name=Saba2009>{{cite journal |doi = 10.3354/meps08070|title = Effects of diet on release of dissolved organic and inorganic nutrients by the copepod ''Acartia tonsa''|year = 2009|last1 = Saba|first1 = GK|last2 = Steinberg|first2 = DK|last3 = Bronk|first3 = DA|journal = Marine Ecology Progress Series|volume = 386|pages = 147–161|bibcode = 2009MEPS..386..147S|doi-access = free}}</ref> and Steinberg et al. (2017).<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></small>}}]]

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. 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 "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 />

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 | header            = Comparison of zooplankton-mediated carbon cycles{{hsp}}<ref name=Halfter2020>{{cite journal |doi = 10.3389/fmars.2020.567917|title = The Role of Zooplankton in Establishing Carbon Export Regimes in the Southern Ocean – A Comparison of Two Representative Case Studies in the Subantarctic Region|year = 2020|last1 = Halfter|first1 = Svenja|last2 = Cavan|first2 = Emma L.|last3 = Swadling|first3 = Kerrie M.|last4 = Eriksen|first4 = Ruth S.|last5 = Boyd|first5 = Philip W.|journal = Frontiers in Marine Science|volume = 7|s2cid = 222003883|doi-access = free}} [[File:CC-BY icon.svg|50px]] Material was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License].</ref>
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 | footer            = <small>Grazing and fragmentation of particles at both sites increases nutrient recycling in the upper water column</small>
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 | image1    = Zooplankton-mediated carbon cycle 1.jpg
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 | caption1  = {{center|'''Kerguelen Plateau'''<br />[[Iron fertilization|Naturally iron-fertilized]]}} On the [[Kerguelen Plateau]] in summer, high iron levels lead to high [[chlorophyll a]] as a proxy for algae biomass at the surface. The diverse zooplankton community feeds on the sinking particle flux and acts as a gate-keeper to the deeper ocean by ingesting and fragmenting sinking particles and, consequently, significantly reducing the export flux out of the [[epipelagic]]. The main export particles are [[diatom]] resting spores, which bypass the intense grazing pressure, followed by fecal pellets.<ref name=Halfter2020 />
 | image2    = Zooplankton-mediated carbon cycle 2.jpg
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 | caption2  = {{center|'''Southern Ocean waters'''<br />[[High-nutrient, low-chlorophyll regions|High nutrient, low chlorophyll]]}} In [[Southern Ocean]] waters in summer, iron levels are relatively low and support a more diverse phytoplankton community, but with lower biomass, which, in turn, affects zooplankton community composition and biomass. The grazing pressure during summer is focused mostly on [[picoplankton]], which leaves large particles for export.<ref name=Halfter2020 />
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