Editing Zooplankton (section)

===Mixotrophs===
{{see also|Mixotroph|Mixotrophic dinoflagellate}}

A [[mixotroph]] is an organism that can use a mix of different [[Primary nutritional groups|sources of energy and carbon]], instead of having a single trophic mode on the continuum from complete [[autotrophy]] at one end to [[heterotrophy]] at the other. It is estimated that mixotrophs comprise more than half of all microscopic plankton.<ref>{{Cite web |last=Collins |first=Richard |date=2016-11-14 |title=Beware the mixotrophs – they can destroy entire ecosystems 'in a matter of hours' |url=https://www.irishexaminer.com/opinion/columnists/arid-20430358.html |website=Irish Examiner |language=en}}</ref> There are two types of eukaryotic mixotrophs: those with their own [[chloroplast]]s, and those with [[endosymbiont]]s—and others that acquire them through [[kleptoplasty]] or by enslaving the entire phototrophic cell.<ref>{{Cite web |last=University |first=Swansea |title=Microscopic body snatchers infest our oceans |url=https://phys.org/news/2017-08-microscopic-body-snatchers-infest-oceans.html |website=phys.org |language=en}}</ref>

The distinction between plants and animals often breaks down in very small organisms. Possible combinations are [[phototroph|photo-]] and [[chemotroph]]y, [[lithotroph|litho-]] and [[organotroph]]y, [[autotroph|auto-]] and [[heterotroph]]y or other combinations of these. Mixotrophs can be either [[eukaryote|eukaryotic]] or [[prokaryote|prokaryotic]].<ref name='Eiler'>{{cite journal |author=Eiler A |title=Evidence for the Ubiquity of Mixotrophic Bacteria in the Upper Ocean: Implications and Consequences |journal=Appl Environ Microbiol |volume=72 |issue=12 |pages=7431–7 |date=December 2006 |pmid=17028233 |doi=10.1128/AEM.01559-06 |pmc=1694265 |bibcode=2006ApEnM..72.7431E }}</ref> They can take advantage of different environmental conditions.<ref>{{cite journal |vauthors=Katechakis A, Stibor H |title=The mixotroph ''Ochromonas tuberculata'' may invade and suppress specialist phago- and phototroph plankton communities depending on nutrient conditions |journal=Oecologia |volume=148 |issue=4 |pages=692–701 |date=July 2006 |pmid=16568278 |doi=10.1007/s00442-006-0413-4 |bibcode=2006Oecol.148..692K |s2cid=22837754 }}</ref>

Many marine microzooplankton are mixotrophic, which means they could also be classified as phytoplankton. Recent studies of marine microzooplankton found 30–45% of the ciliate abundance was mixotrophic, and up to 65% of the amoeboid, foram and radiolarian [[Biomass (ecology)|biomass]] was mixotrophic.<ref name=Leles2017>{{cite journal | last1 = Leles | first1 = S.G. | last2 = Mitra | first2 = A. | last3 = Flynn | first3 = K.J. | last4 = Stoecker | first4 = D.K. | last5 = Hansen | first5 = P.J. | last6 = Calbet | first6 = A. | last7 = McManus | first7 = G.B. | last8 = Sanders | first8 = R.W. | last9 = Caron | first9 = D.A. | last10 = Not | first10 = F. | last11 = Hallegraeff | first11 = G.M. | year = 2017 | title = Oceanic protists with different forms of acquired phototrophy display contrasting biogeographies and abundance | journal = Proceedings of the Royal Society B: Biological Sciences | volume = 284 | issue = 1860| page = 20170664 | doi = 10.1098/rspb.2017.0664 | pmid = 28768886 | pmc = 5563798 }}</ref>

{|class="wikitable"
! colspan=7 |{{centre|Mixotrophic zooplankton that combine phototrophy and heterotrophy – table based on Stoecker et al., 2017 <ref  name=Stoecker2017>{{cite journal | last1 = Stoecker | first1 = D.K. | last2 = Hansen | first2 = P.J. | last3 = Caron | first3 = D.A. | last4 = Mitra | first4 = A. | year = 2017 | title = Mixotrophy in the marine plankton | url = http://pdfs.semanticscholar.org/8492/ec7724a468af240e014aa539a8865568473d.pdf | archive-url = https://web.archive.org/web/20190227180157/http://pdfs.semanticscholar.org/8492/ec7724a468af240e014aa539a8865568473d.pdf | url-status = dead | archive-date = 2019-02-27 | journal = Annual Review of Marine Science | volume = 9 | pages = 311–335 | doi = 10.1146/annurev-marine-010816-060617 | pmid = 27483121 | bibcode = 2017ARMS....9..311S | s2cid = 25579538 }}</ref>}}
|-
! colspan=2 | Description
! colspan=2 | Example
! Further examples
|-
| colspan=5 | Called '''''nonconstitutive mixotrophs''''' by Mitra et al., 2016.<ref name=Mitra2016>{{cite journal | last1 = Mitra | first1 = A | last2 = Flynn | first2 = KJ | last3 = Tillmann | first3 = U | last4 = Raven | first4 = J | last5 = Caron | first5 = D | display-authors = etal | year = 2016 | title = Defining planktonic protist functional groups on mechanisms for energy and nutrient acquisition; incorporation of diverse mixotrophic strategies | journal = Protist | volume = 167 | issue = 2| pages = 106–20 | doi = 10.1016/j.protis.2016.01.003 | pmid = 26927496 | doi-access = free | hdl = 10261/131722 | hdl-access = free }}</ref> Zooplankton that are photosynthetic: microzooplankton or metazoan zooplankton that acquire phototrophy through chloroplast retention<sup>a</sup> or maintenance of algal endosymbionts.
|-
| Generalists  
| Protists that retain chloroplasts and rarely other organelles from many algal taxa
| [[File:Halteria.jpg|100px]]
| 
| Most [[oligotrich]] ciliates that retain plastids<sup>a</sup>
|-
| rowspan=2 | Specialists
| 1. Protists that retain chloroplasts and sometimes other organelles from one algal species or very closely related algal species
| [[File:Dinophysis acuminata.jpg|100px]]
| ''[[Dinophysis acuminata]]''
|  ''[[Dinophysis]]'' spp.<br />''[[Myrionecta rubra]]''
|-
| 2. Protists or zooplankton with algal endosymbionts of only one algal species or very closely related algal species
| [[File:Noctiluca scintillans varias.jpg|100px]]
| ''[[Noctiluca scintillans]]''
|  [[wiktionary:metazooplankton|Metazooplankton]] with algal [[endosymbiont]]s<br />Most mixotrophic [[Rhizaria]] ([[Acantharea]], [[Polycystinea]], and [[Foraminifera]])<br />Green ''[[Noctiluca scintillans]]''
|-
| colspan=7 style="text-align:center;" | <small><sup>a</sup>Chloroplast (or plastid) retention = sequestration = enslavement. Some plastid-retaining species also retain other organelles and prey cytoplasm.</small>
|}

''Phaeocystis'' species are endosymbionts to [[Acantharea|acantharian]] radiolarians.<ref name=":4">{{cite journal |last1=Decelle |first1=Johan |last2=Simó |first2=Rafel |last3=Galí |first3=Martí |last4=Vargas |first4=Colomban de |last5=Colin |first5=Sébastien |last6=Desdevises |first6=Yves |last7=Bittner |first7=Lucie |last8=Probert |first8=Ian |last9=Not |first9=Fabrice |date=2012-10-30 |title=An original mode of symbiosis in open ocean plankton |journal=Proceedings of the National Academy of Sciences |language=en |volume=109 |issue=44 |pages=18000–18005 |doi=10.1073/pnas.1212303109 |issn=0027-8424 |pmid=23071304 |pmc=3497740 |bibcode=2012PNAS..10918000D |doi-access=free}}</ref><ref name=":5">{{Cite journal |last1=Mars Brisbin |first1=Margaret |last2=Grossmann |first2=Mary M. |last3=Mesrop |first3=Lisa Y. |last4=Mitarai |first4=Satoshi |date=2018 |title=Intra-host Symbiont Diversity and Extended Symbiont Maintenance in Photosymbiotic Acantharea (Clade F) |journal=Frontiers in Microbiology |language=en |volume=9 |pages=1998 |doi=10.3389/fmicb.2018.01998 |pmid=30210473 |pmc=6120437 |issn=1664-302X |doi-access=free}}</ref> ''[[Phaeocystis]]'' is an important algal genus found as part of the marine [[phytoplankton]] around the world. It has a [[Polymorphism (biology)|polymorphic]] life cycle, ranging from free-living cells to large colonies.<ref name=":0">{{Cite journal|title = Phaeocystis blooms in the global ocean and their controlling mechanisms: a review|journal = Journal of Sea Research|date = 2005-01-01|pages = 43–66|volume = 53|series = Iron Resources and Oceanic Nutrients – Advancement of Global Environmental Simulations|issue = 1–2|doi = 10.1016/j.seares.2004.01.008|first1 = Véronique|last1 = Schoemann|first2 = Sylvie|last2 = Becquevort|first3 = Jacqueline|last3 = Stefels|first4 = Véronique|last4 = Rousseau|first5 = Christiane|last5 = Lancelot|citeseerx = 10.1.1.319.9563|bibcode = 2005JSR....53...43S}}</ref> It has the ability to form floating colonies, where hundreds of cells are embedded in a gel matrix, which can increase massively in size during [[Algal bloom|blooms]].<ref>{{cite web |url=http://www.phaeocystis.org/ |title=Welcome to the Phaeocystis antarctica genome sequencing project homepage |access-date=2020-08-23 |archive-date=2015-11-20 |archive-url=https://web.archive.org/web/20151120043948/http://www.phaeocystis.org/ |url-status=dead }}</ref> As a result, ''Phaeocystis'' is an important contributor to the marine [[Carbon cycle|carbon]]<ref>{{cite journal |title=Rapid and early export of Phaeocystis antarctica blooms in the Ross Sea, Antarctica <!--http://www.nature.com/doifinder/10.1038/35007061-->|journal = Nature|pages = 595–598|volume = 404|issue = 6778|doi = 10.1038/35007061|pmid = 10766240|first1 = G. R.|last1 = DiTullio|first2 = J. M.|last2 = Grebmeier|author-link2=Jacqueline M. Grebmeier|first3 = K. R.|last3 = Arrigo|first4 = M. P.|last4 = Lizotte|first5 = D. H.|last5 = Robinson|first6 = A.|last6 = Leventer|first7 = J. P.|last7 = Barry|first8 = M. L.|last8 = VanWoert|first9 = R. B.|last9 = Dunbar|year = 2000|bibcode = 2000Natur.404..595D|s2cid = 4409009}}</ref> and [[sulfur cycle]]s.<ref>{{Cite journal|title = DMSP-lyase activity in a spring phytoplankton bloom off the Dutch coast, related to Phaeocystis sp. abundance|journal = Marine Ecology Progress Series|date = 1995-07-20|pages = 235–243|volume = 123|doi = 10.3354/meps123235|first1 = Stefels|last1 = J|first2 = Dijkhuizen|last2 = L|first3 = Gieskes|last3 = WWC|url = https://pure.rug.nl/ws/files/62552225/DMSP_lyase_activity_in_a_spring_phytoplankton_bloom_off_the_Dutch_coast.pdf|bibcode = 1995MEPS..123..235S|doi-access = free}}</ref>

<gallery caption="Mixoplankton" mode="packed" heights="144px" style="float:left;">
File:Tintinnid ciliate Favella.jpg|[[Tintinnid]] ciliate ''Favella''
File:Euglena mutabilis - 400x - 1 (10388739803) (cropped).jpg|''[[Euglena|Euglena mutabilis]]'', a photosynthetic [[flagellate]]
File:Stichotricha secunda - 400x (14974779356).jpg|[[Zoochlorellae]] (green) living inside the [[ciliate]] ''Stichotricha secunda''
File:Dinophysis acuta.jpg| The dinoflagellate ''Dinophysis acuta''
</gallery>

{{multiple image
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 | header            = Mixotrophic radiolarians
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 | image1    = Phaeocystis symbionts within an acantharian host.png
 | alt1      = 
 | caption1  = [[Acantharian]] radiolarian hosts ''[[Phaeocystis]]'' symbionts
 | width2    = 200
 | image2    = Ecomare - schuimalg strand (7037-schuimalg-phaeocystis-ogb).jpg
 | alt2      = 
 | caption2  = White ''Phaeocystis'' algal foam washing up on a beach
}}

{{clear}}

A number of forams are mixotrophic. These have unicellular [[algae]] as [[endosymbiont]]s, from diverse lineages such as the [[green algae]], [[red algae]], [[golden algae]], [[diatom]]s, and [[dinoflagellate]]s.<ref name=Hemleben/> Mixotrophic foraminifers are particularly common in nutrient-poor oceanic waters.<ref>{{Cite book |last=Marshall |first=K. C. |url=https://books.google.com/books?id=QvvlBwAAQBAJ&dq=%22The+symbiont-bearing+foraminifera+are+particularly+common+in+nutrient-poor+oceanic+waters%22&pg=PA22 |title=Advances in Microbial Ecology |date=2013-11-11 |publisher=Springer Science & Business Media |isbn=978-1-4684-7612-5 |language=en}}</ref> Some forams are [[kleptoplasty|kleptoplastic]], retaining [[chloroplast]]s from ingested algae to conduct [[photosynthesis]].<ref>{{Cite journal|title = Benthic Foraminifera of dysoxic sediments: chloroplast sequestration and functional morphology|year = 1999|last= Bernhard|first=J. M.|author2=Bowser, S.M.|journal = Earth-Science Reviews|volume = 46|issue = 1|pages = 149–165|doi = 10.1016/S0012-8252(99)00017-3|bibcode=1999ESRv...46..149B}}</ref>

By trophic orientation, dinoflagellates are all over the place. Some dinoflagellates are known to be [[photosynthesis|photosynthetic]], but a large fraction of these are in fact [[mixotrophy|mixotrophic]], combining photosynthesis with ingestion of prey ([[phagotrophy]]).<ref>{{Cite journal | last1 = Stoecker | first1 = D. K. | title = Mixotrophy among Dinoflagellates | doi = 10.1111/j.1550-7408.1999.tb04619.x | journal = The Journal of Eukaryotic Microbiology | volume = 46 | issue = 4 | pages = 397–401 | year = 1999 | s2cid = 83885629 | name-list-style = vanc}}</ref> Some species are [[endosymbiont]]s of marine animals and other protists, and play an important part in the biology of [[coral reef]]s. Others predate other protozoa, and a few forms are parasitic. Many dinoflagellates are [[mixotrophic]] and could also be classified as phytoplankton. The toxic dinoflagellate ''[[Dinophysis acuta]]'' acquire chloroplasts from its prey. "It cannot catch the cryptophytes by itself, and instead relies on ingesting ciliates such as the red ''[[Myrionecta rubra]]'', which sequester their chloroplasts from a specific cryptophyte clade (Geminigera/Plagioselmis/Teleaulax)".<ref  name=Stoecker2017 />