View source for Earth:Phytoplankton

{{short description| Autotrophic members of the plankton ecosystem }}
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'''Phytoplankton''' ({{IPAc-en|ˌ|f|aɪ|t|oʊ|ˈ|p|l|æ|ŋ|k|t|ə|n}}) are the autotrophic (self-feeding) components of the [[Earth:Plankton|plankton]] community and a key part of oceans, seas and freshwater basin [[Earth:Aquatic ecosystem|ecosystem]]s. The name comes from the [[Social:Greek language|Greek]] words φυτόν (''phyton''), meaning "[[Biology:Plant|plant]]", and πλαγκτός (''planktos''), meaning "wanderer" or "drifter".<ref>{{cite book 
 | last = Thurman
 | first = H. V.
 | year = 2007
 | title = Introductory Oceanography
 | publisher = Academic Internet Publishers
 | location =
 | isbn = 978-1-4288-3314-2
 }} </ref> Most phytoplankton are too small to be individually seen with the [[Astronomy:Naked eye|unaided eye]]. However, when present in high enough numbers, some varieties may be noticeable as colored patches on the water surface due to the presence of [[Biology:Chlorophyll|chlorophyll]] within their cells and accessory pigments (such as [[Biology:Phycobiliprotein|phycobiliprotein]]s or [[Chemistry:Xanthophyll|xanthophyll]]s) in some species. About 1% of the global [[Earth:Biomass (ecology)|biomass]] is due to phytoplankton.<ref>{{cite journal | vauthors = Bidle KD, Falkowski PG | title = death in planktonic, photosynthetic microorganisms | journal = Nature Reviews. Microbiology | volume = 2 | issue = 8 | pages = 643–655 | date = August 2004 | pmid = 15263899 | doi = 10.1038/nrmicro956 }}</ref>

== Types ==
[[File:Diatoms through the microscope.jpg|thumb|300px|right|[[Biology:Diatom|Diatom]]s are one of the most common types of phytoplankton.]]

Phytoplankton are [[Earth:Photosynthesis|photosynthesizing]] microscopic biotic organisms that inhabit the upper sunlit layer of almost all oceans and bodies of fresh water on Earth. They are agents for [[Biology:Marine primary production|primary production]], the creation of organic compounds from [[Chemistry:Carbon dioxide|carbon dioxide]] dissolved in the water, a process that sustains the aquatic [[Biology:Food web|food web]].<ref>{{cite web|last=Ghosal; Rogers; Wray|first=S.; M.; A.|title=The Effects of Turbulence on Phytoplankton|url=https://ntrs.nasa.gov/search.jsp?R=20040171754&qs=Ntx%3Dmode%2520matchany%26Ntk%3DTitle%26Ns%3DLoaded-Date|work=Aerospace Technology Enterprise|publisher=NTRS|accessdate=16 June 2011}}</ref>

Phytoplankton are extremely diverse, varying from photosynthesising bacteria (cyanobacteria), to plant-like diatoms, to armour-plated coccolithophores.<ref>Lindsey, R., Scott, M. and Simmon, R. (2010) [https://earthobservatory.nasa.gov/features/Phytoplankton "What are phytoplankton"]. ''NASA Earth Observatory''.</ref>

[[File:Phytoplankton types.jpg|left|thumb|600px|{{spaces|4}}
[[Biology:Cyanobacteria|cyanobacteria]]{{spaces|16}}
[[Biology:Diatom|diatom]]{{spaces|18}}
[[Biology:Dinoflagellate|dinoflagellate]]{{spaces|16}}
[[Biology:Green algae|green algae]]{{spaces|10}}
[[Biology:Coccolithophore|coccolithophore]]
{{center|Some phytoplankton types (not to scale)}}]]

{{clear}}

== Ecology ==
[[File:Cycling of marine phytoplankton.png|thumb|upright=1.7| Cycling of marine phytoplankton. Phytoplankton live in the [[Earth:Photic zone|photic zone]] of the ocean, where photosynthesis is possible. During photosynthesis, they assimilate carbon dioxide and release oxygen. If solar radiation is too high, phytoplankton may fall victim to photodegradation. For growth, phytoplankton cells depend on nutrients, which enter the ocean by rivers, continental weathering, and glacial ice meltwater on the poles. Phytoplankton release dissolved organic carbon (DOC) into the ocean. Since phytoplankton are the basis of marine food webs, they serve as prey for zooplankton, fish larvae and other heterotrophic organisms. They can also be degraded by bacteria or by viral lysis. Although some phytoplankton cells, such as dinoflagellates, are able to migrate vertically, they are still incapable of actively moving against currents, so they slowly sink and ultimately fertilize the seafloor with dead cells and detritus.<ref>Käse L, Geuer JK. (2018) [https://link.springer.com/chapter/10.1007/978-3-319-93284-2_5 "Phytoplankton responses to marine climate change–an introduction"].  In Jungblut S., Liebich V., Bode M. (Eds) ''YOUMARES 8–Oceans Across Boundaries: Learning from each other'', pages 55–72, Springer. {{doi|10.1007/978-3-319-93284-2_5}}.  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>]]

Phytoplankton obtain [[Physics:Energy|energy]] through the [[Biology:Biological process|process]] of [[Earth:Photosynthesis|photosynthesis]] and must therefore live in the well-lit surface layer (termed the [[Earth:Photic zone|euphotic zone]]) of an [[Earth:Ocean|ocean]], [[Earth:Sea|sea]], [[Earth:Lake|lake]], or other body of water. Phytoplankton account for about half of all [[Earth:Photosynthesis|photosynthetic activity]] on Earth.<ref>{{cite journal |author1=Michael J. Behrenfeld  |display-authors=0|title=Biospheric primary production during an ENSO transition |journal=Science |date=2001-03-30 |volume=291 |issue=5513 |pages=2594–7 |doi=10.1126/science.1055071 |pmid=11283369 |url=https://escholarship.org/content/qt51z7z4n6/qt51z7z4n6.pdf?t=nuq67b |bibcode=2001Sci...291.2594B}}</ref><ref>[http://www.nasa.gov/topics/earth/features/modis_fluorescence.html "NASA Satellite Detects Red Glow to Map Global Ocean Plant Health"] [[Organization:NASA|NASA]], 28 May 2009.</ref><ref>{{Cite web |url=http://www.nasa.gov/centers/goddard/news/topstory/chlorophyll.html |title=Satellite Sees Ocean Plants Increase, Coasts Greening |accessdate=9 June 2014 |publisher=[[Organization:NASA|NASA]] |date=2 March 2005}}</ref> Their cumulative energy fixation in [[Chemistry:Carbon compounds|carbon compounds]] ([[Earth:Primary production|primary production]]) is the basis for the vast majority of oceanic and also many freshwater [[Biology:Food web|food web]]s ([[Earth:Chemosynthesis|chemosynthesis]] is a notable exception).

While almost all phytoplankton [[Biology:Species|species]] are [[Biology:Obligate|obligate]] photoautotrophs, there are some that are mixotrophic and other, non-pigmented [[Biology:Species|species]] that are actually [[Biology:Heterotroph|heterotroph]]ic (the latter are often viewed as [[Earth:Zooplankton|zooplankton]]). Of these, the best known are [[Biology:Dinoflagellate|dinoflagellate]] [[Biology:Genus|genera]] such as ''[[Biology:Noctiluca|Noctiluca]]'' and ''[[Biology:Dinophyceae|Dinophysis]]'', that obtain [[Chemistry:Organic matter|organic]] [[Chemistry:Carbon|carbon]] by [[Biology:Ingestion|ingesting]] other organisms or detrital material.

Phytoplankton are crucially dependent on minerals. These are primarily macronutrients such as [[Chemistry:Nitrate|nitrate]], [[Chemistry:Phosphate|phosphate]] or [[Chemistry:Silicic acid|silicic acid]], whose availability is governed by the balance between the so-called [[Biology:Biological pump|biological pump]] and [[Earth:Upwelling|upwelling]] of deep, nutrient-rich waters. Phytoplankton nutrient composition drives and is driven by the [[Redfield ratio]] of macronutrients generally available throughout the surface oceans. However, across large regions of the [[Earth:World Ocean|World Ocean]] such as the [[Earth:Southern Ocean|Southern Ocean]], phytoplankton are also limited by the lack of the micronutrient [[Chemistry:Iron|iron]]. This has led to some scientists advocating [[Earth:Iron fertilization|iron fertilization]] as a means to counteract the accumulation of human-produced carbon dioxide (CO<sub>2</sub>) in the [[Astronomy:Atmosphere|atmosphere]].<ref name=richtel07>{{Cite news | first = M. | last = Richtel | title = Recruiting Plankton to Fight Global Warming | newspaper = New York Times  | date = 1 May 2007 | url = https://www.nytimes.com/2007/05/01/business/01plankton.html }}</ref> Large-scale experiments have added iron (usually as salts such as iron sulphate) to the oceans to promote phytoplankton growth and draw atmospheric CO<sub>2</sub> into the ocean. However, controversy about manipulating the ecosystem and the efficiency of iron fertilization has slowed such experiments.<ref>{{cite journal |last1=Monastersky |first1=Richard |title=Iron versus the Greenhouse: Oceanographers Cautiously Explore a Global Warming Therapy |journal=Science News |volume=148 |issue=14 |year=1995 |pages=220–1 |doi=10.2307/4018225|jstor=4018225 }}</ref>

Phytoplankton depend on B Vitamins for survival. Areas in the ocean have been identified as having a major lack of some B Vitamins, and correspondingly, phytoplankton.<ref>{{cite web |url=https://www.sciencedaily.com/releases/2012/07/120723162613.htm |title=Existence of vitamin 'deserts' in the ocean confirmed|work=ScienceDaily|first=Sergio|last=Sañudo-Wilhelmy|date=2012-06-23}}</ref>

The effects of [[Social:Anthropogeny|anthropogenic]] warming on the global population of phytoplankton is an area of active research. Changes in the vertical stratification of the water column, the rate of temperature-dependent biological reactions, and the atmospheric supply of nutrients are expected to have important effects on future phytoplankton productivity.<ref name="ReferenceA">{{cite journal|last1=Henson|first1=S. A.|last2=Sarmiento|first2=J. L.|last3=Dunne|first3=J. P.|last4=Bopp|first4=L.|last5=Lima|first5=I.|last6=Doney|first6=S. C.|last7=John|first7=J.|last8=Beaulieu|first8=C.|year=2010|title=Detection of anthropogenic climate change in satellite records of ocean chlorophyll and productivity|journal=Biogeosciences|volume=7|issue=2|pages=621–40|doi=10.5194/bg-7-621-2010|bibcode=2010BGeo....7..621H|doi-access=free}}</ref><ref name="ReferenceB">{{cite journal|last1=Steinacher|first1=M.|last2=Joos|first2=F.|last3=Frölicher|first3=T. L.|last4=Bopp|first4=L.|last5=Cadule|first5=P.|last6=Cocco|first6=V.|last7=Doney|first7=S. C.|last8=Gehlen|first8=M.|last9=Lindsay|first9=K.|year=2010|title=Projected 21st century decrease in marine productivity: a multi-model analysis|journal=Biogeosciences|volume=7|issue=3|pages=979–1005|doi=10.5194/bg-7-979-2010|last10=Moore|first10=J. K.|last11=Schneider|first11=B.|last12=Segschneider|first12=J.|doi-access=free}}</ref>

The effects of anthropogenic ocean acidification on phytoplankton growth and community structure has also received considerable attention. Phytoplankton such as coccolithophores contain calcium carbonate cell walls that are sensitive to ocean acidification. Because of their short generation times, evidence suggests some phytoplankton can adapt to changes in pH induced by increased carbon dioxide on rapid time-scales (months to years).<ref>{{Cite journal|last=Collins|first=Sinéad|last2=Rost|first2=Björn|last3=Rynearson|first3=Tatiana A.|date=2013-11-25|title=Evolutionary potential of marine phytoplankton under ocean acidification|journal=Evolutionary Applications|language=en|volume=7|issue=1|pages=140–155|doi=10.1111/eva.12120|issn=1752-4571|pmc=3894903|pmid=24454553}}</ref><ref>{{Cite journal|last=Lohbeck|first=Kai T.|last2=Riebesell|first2=Ulf|last3=Reusch|first3=Thorsten B. H.|date=2012-04-08|title=Adaptive evolution of a key phytoplankton species to ocean acidification|journal=Nature Geoscience|language=En|volume=5|issue=5|pages=346–351|doi=10.1038/ngeo1441|issn=1752-0894|bibcode=2012NatGe...5..346L}}</ref>

Phytoplankton serve as the base of the aquatic food web, providing an essential ecological function for all aquatic life. Under future conditions of anthropogenic warming and ocean acidification, changes in phytoplankton mortality may be significant.{{citation needed|date=January 2019}}{{elucidate|date=January 2019}}  One of the many food chains in the ocean – remarkable due to the small number of links – is that of phytoplankton sustaining [[Biology:Krill|krill]] (a [[Biology:Crustacean|crustacean]] similar to a tiny shrimp), which in turn sustain baleen whales.

==Diversity==
{{multiple image
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 | image1    = Spring Bloom Colors the Pacific Near Hokkaido.jpg
 | alt1      = 
 | caption1  = When two currents collide (here the [[Earth:Oyashio Current|Oyashio]] and [[Earth:Kuroshio Current|Kuroshio]] currents) they create eddies. Phytoplankton concentrates along the boundaries of the eddies, tracing the motion of the water.
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 | caption2  = [[Biology:Algal bloom|Algal bloom]] off south west England. 
}}
The term phytoplankton encompasses all photoautotrophic microorganisms in aquatic [[Biology:Food web|food web]]s. However, unlike terrestrial communities, where most autotrophs are plants, phytoplankton are a diverse group, incorporating protistan [[Biology:Eukaryote|eukaryote]]s and both [[Biology:Bacteria|eubacterial]] and archaebacterial [[Biology:Prokaryote|prokaryote]]s. There are about 5,000 known species of marine phytoplankton.<ref name="Hallegraeff 03">{{cite book|title=Manual on Harmful Marine Microalgae|last=Hallegraeff|first=G.M.|publisher=Unesco|year=2003|isbn=978-92-3-103871-6|editor-last1=Hallegraeff|editor-first1=Gustaaf M.|pages=25–49|chapter=Harmful algal blooms: a global overview|editor-last2=Anderson|editor-first2=Donald Mark|editor-last3=Cembella|editor-first3=Allan D.|editor-last4=Enevoldsen|editor-first4=Henrik O.|chapter-url=http://unesdoc.unesco.org/images/0013/001317/131711e.pdf}}</ref> How such diversity [[Biology:Evolution|evolved]] despite scarce resources (restricting [[Biology:Niche differentiation|niche differentiation]]) is unclear.<ref>{{cite journal|last1=Hutchinson|first1=G. E.|year=1961|title=The Paradox of the Plankton|journal=The American Naturalist|volume=95|issue=882|pages=137–45|doi=10.1086/282171|url=https://semanticscholar.org/paper/9d96fe6144d3436fff25e617a25d774e8c39f5b5}}</ref>

In terms of numbers, the most important groups of phytoplankton include the [[Biology:Diatom|diatom]]s, [[Biology:Cyanobacteria|cyanobacteria]] and [[Biology:Dinoflagellate|dinoflagellate]]s, although many other groups of [[Biology:Algae|algae]] are represented. One group, the [[Biology:Coccolithophore|coccolithophorids]], is responsible (in part) for the release of significant amounts of [[Chemistry:Dimethyl sulfide|dimethyl sulfide]] (DMS) into the atmosphere. DMS is [[Chemistry:Redox|oxidized]] to form sulfate which, in areas where ambient [[Chemistry:Aerosol|aerosol]] particle concentrations are low, can contribute to the population of [[Physics:Cloud condensation nuclei|cloud condensation nuclei]], mostly leading to increased cloud cover and cloud [[Earth:Albedo|albedo]] according to the so-called [[Astronomy:CLAW hypothesis|CLAW Hypothesis]].<ref name="Oceanicphytoplankton">{{cite journal|last1=Charlson|first1=Robert J.|last2=Lovelock|first2=James E.|last3=Andreae|first3=Meinrat O.|last4=Warren|first4=Stephen G.|year=1987|title=Oceanic phytoplankton, atmospheric sulphur, cloud albedo and climate|journal=Nature|volume=326|issue=6114|pages=655–61|bibcode=1987Natur.326..655C|doi=10.1038/326655a0}}</ref><ref>{{cite journal|last1=Quinn|first1=P. K.|last2=Bates|first2=T. S.|year=2011|title=The case against climate regulation via oceanic phytoplankton sulphur emissions|journal=Nature|volume=480|issue=7375|pages=51–6|bibcode=2011Natur.480...51Q|doi=10.1038/nature10580|pmid=22129724|url=https://zenodo.org/record/1233319}}</ref> Different types of phytoplankton support different [[Earth:Trophic level|trophic level]]s within varying ecosystems.  In [[Biology:Oligotroph|oligotroph]]ic oceanic regions such as the Sargasso Sea or the South Pacific Gyre, phytoplankton is dominated by the small sized cells, called [[Biology:Photosynthetic picoplankton|picoplankton]] and nanoplankton (also referred to as picoflagellates and nanoflagellates), mostly composed of [[Biology:Cyanobacteria|cyanobacteria]] (''[[Biology:Prochlorococcus|Prochlorococcus]]'', ''[[Biology:Synechococcus|Synechococcus]]'') and picoeucaryotes such as ''[[Biology:Micromonas|Micromonas]]''.  Within more productive ecosystems, dominated by [[Earth:Upwelling|upwelling]] or high terrestrial inputs, larger [[Biology:Dinoflagellate|dinoflagellate]]s are the more dominant phytoplankton and reflect a larger portion of the [[Earth:Biomass (ecology)|biomass]].<ref>{{cite journal|last1=Calbet|first1=A.|year=2008|title=The trophic roles of microzooplankton in marine systems|journal=ICES Journal of Marine Science|volume=65|issue=3|pages=325–31|doi=10.1093/icesjms/fsn013|doi-access=free}}</ref>

== Growth strategy ==
In the early twentieth century, Alfred C. Redfield found the similarity of the phytoplankton's elemental composition to the major dissolved nutrients in the deep ocean.<ref>{{cite book |last1=Redfield |first1=Alfred C. |year=1934 |chapter=On the Proportions of Organic Derivatives in Sea Water and their Relation to the Composition of Plankton |pages=176–92 |editor1-last=Johnstone |editor1-first=James |editor2-last=Daniel |editor2-first=Richard Jellicoe |title=James Johnstone Memorial Volume |location=Liverpool |publisher=University Press of Liverpool |oclc=13993674 }}</ref> Redfield proposed that the ratio of carbon to nitrogen to phosphorus (106:16:1) in the ocean was controlled by the phytoplankton's requirements, as phytoplankton subsequently release nitrogen and phosphorus as they are remineralized. This so-called “[[Redfield ratio]]” in describing [[Chemistry:Stoichiometry|stoichiometry]] of phytoplankton and seawater has become a fundamental principle to understand marine ecology, biogeochemistry and phytoplankton evolution.<ref name="Arrigo K.R 2005">{{cite journal |last1=Arrigo |first1=Kevin R. |title=Marine microorganisms and global nutrient cycles |journal=Nature |volume=437 |issue=7057 |pages=349–55 |year=2005 |pmid=16163345 |doi=10.1038/nature04159 |bibcode=2005Natur.437..349A }}</ref> However, the Redfield ratio is not a universal value and it may diverge due to the changes in exogenous nutrient delivery<ref>{{cite journal |last1=Fanning |first1=Kent A. |title=Influence of atmospheric pollution on nutrient limitation in the ocean |journal=Nature |volume=339 |issue=6224 |year=1989 |pages=460–63 |bibcode=1989Natur.339..460F |doi=10.1038/339460a0 }}</ref> and microbial metabolisms in the ocean, such as [[Biology:Nitrogen fixation|nitrogen fixation]], [[Biology:Denitrification|denitrification]] and [[Biology:Anammox|anammox]].

The dynamic stoichiometry shown in unicellular algae reflects their capability to store nutrients in an internal pool, shift between enzymes with various nutrient requirements and alter osmolyte composition.<ref>{{cite book |first1=Robert Warner |last1=Sterner |first2=James J. |last2=Elser |year=2002 |title=Ecological Stoichiometry: The Biology of Elements from Molecules to the Biosphere |publisher=Princeton University Press |isbn=978-0-691-07491-7 }}{{page needed|date=February 2016}}</ref><ref>{{cite journal |last1=Klausmeier |first1=Christopher A. |last2=Litchman |first2=Elena |last3=Levin |first3=Simon A. |title=Phytoplankton growth and stoichiometry under multiple nutrient limitation |journal=Limnology and Oceanography |volume=49 |issue=4 Part 2 |year=2004 |pages=1463–70 |doi=10.4319/lo.2004.49.4_part_2.1463 |bibcode=2004LimOc..49.1463K |url=https://semanticscholar.org/paper/2bae015161ae88edde1dbbe919da66da092ec6e6 }}</ref> Different cellular components have their own unique stoichiometry characteristics,<ref name="Arrigo K.R 2005"/> for instance, resource (light or nutrients) acquisition machinery such as proteins and chlorophyll contain a high concentration of nitrogen but low in phosphorus. Meanwhile, growth machinery such as ribosomal RNA contains high nitrogen and phosphorus concentrations.

Based on allocation of resources, phytoplankton is classified into three different growth strategies, namely survivalist, bloomer<ref>{{cite journal |last1=Klausmeier |first1=Christopher A. |last2=Litchman |first2=Elena |last3=Daufresne |first3=Tanguy |last4=Levin |first4=Simon A. |title=Optimal nitrogen-to-phosphorus stoichiometry of phytoplankton |journal=Nature |volume=429 |issue=6988 |pages=171–4 |year=2004 |pmid=15141209 |bibcode=2004Natur.429..171K |doi=10.1038/nature02454 }}</ref> and generalist. Survivalist phytoplankton has a high ratio of N:P (>30) and contains an abundance of resource-acquisition machinery to sustain growth under scarce resources. Bloomer phytoplankton has a low N:P ratio (<10), contains a high proportion of growth machinery, and is adapted to exponential growth. Generalist phytoplankton has similar N:P to the Redfield ratio and contain relatively equal resource-acquisition and growth machinery.

==Variability of ocean blooms==
[[File:Competing scientific hypothesis of plankton variability.png|alt=|thumb|upright=1.7| {{center|'''Competing hypothesis of plankton variability <ref name=Behrenfeld2018 />'''<br /><small>Figure adapted from Behrenfeld & Boss 2014.<ref>{{Cite journal|last=Behrenfeld|first=Michael J.|last2=Boss|first2=Emmanuel S.|date=2014-01-03|title=Resurrecting the Ecological Underpinnings of Ocean Plankton Blooms|journal=Annual Review of Marine Science|volume=6|issue=1|pages=167–194|doi=10.1146/annurev-marine-052913-021325|pmid=24079309|issn=1941-1405|bibcode=2014ARMS....6..167B|url=https://semanticscholar.org/paper/828341c531b33444999cef773814d5249b633258}}</ref><br />Courtesy of NAAMES, Langley Research Center, NASA <ref>[https://naames.larc.nasa.gov/science-objectives.html NAAMES: Science - Objectives] Langley Research Center, NASA, Updated: 6 June 2020. Retrieved: 15 June 2020.</ref></small>}}]]

The NAAMES study was a five-year scientific research program conducted between 2015 and 2019 by scientists from [[Organization:Oregon State University|Oregon State University]] and [[Organization:NASA|NASA]] to investigated aspects of phytoplankton dynamics in ocean ecosystems, and how such dynamics influence atmospheric aerosols, clouds, and climate (NAAMES stands for the North Atlantic Aerosols and Marine Ecosystems Study). The study focused on the sub-arctic region of the North Atlantic Ocean, which is the site of one of Earth's largest recurring phytoplankton blooms. The long history of research in this location, as well as relative ease of accessibility, made the North Atlantic an ideal location to test prevailing scientific hypotheses<ref name=Behrenfeld2018>Behrenfeld, M.J. and Boss, E.S. (2018) "Student's tutorial on bloom hypotheses in the context of phytoplankton annual cycles". ''Global change biology'', '''24'''(1): 55–77. {{doi|10.1111/gcb.13858}}.</ref> in an effort to better understand the role of phytoplankton aerosol emissions on Earth's energy budget.<ref name=Behrenfeld2019>{{Cite journal|last=Behrenfeld|first=Michael J.|last2=Moore|first2=Richard H.|last3=Hostetler|first3=Chris A.|last4=Graff|first4=Jason|last5=Gaube|first5=Peter|last6=Russell|first6=Lynn M.|last7=Chen|first7=Gao|last8=Doney|first8=Scott C.|last9=Giovannoni|first9=Stephen|last10=Liu|first10=Hongyu|last11=Proctor|first11=Christopher|date=2019-03-22|title=The North Atlantic Aerosol and Marine Ecosystem Study (NAAMES): Science Motive and Mission Overview|journal=Frontiers in Marine Science|volume=6|pages=122|doi=10.3389/fmars.2019.00122|issn=2296-7745|doi-access=free}}</ref>

NAAMES was designed to target specific phases of the annual phytoplankton cycle: minimum, climax and the intermediary decreasing and increasing biomass, in order to resolve debates on the timing of bloom formations and the patterns driving annual bloom re-creation.<ref name=Behrenfeld2019 /> The NAAMES project also investigated the quantity, size, and composition of aerosols generated by [[Earth:Primary production|primary production]] in order to understand how  phytoplankton bloom cycles affect cloud formations and climate.<ref name=Engel2017>{{Cite journal|last=Engel|first=Anja|last2=Bange|first2=Hermann W.|last3=Cunliffe|first3=Michael|last4=Burrows|first4=Susannah M.|last5=Friedrichs|first5=Gernot|last6=Galgani|first6=Luisa|last7=Herrmann|first7=Hartmut|last8=Hertkorn|first8=Norbert|last9=Johnson|first9=Martin|last10=Liss|first10=Peter S.|last11=Quinn|first11=Patricia K.|date=2017-05-30|title=The Ocean's Vital Skin: Toward an Integrated Understanding of the Sea Surface Microlayer|journal=Frontiers in Marine Science|volume=4|doi=10.3389/fmars.2017.00165|issn=2296-7745|doi-access=free}}</ref>

== Is global phytoplankton on the decline? ==
[[File:Plankton satellite image.jpg|thumb|upright=1.7| World concentrations of surface ocean chlorophyll as viewed by satellite during the northern spring, averaged from 1998 to 2004. Chlorophyll is a marker for the distribution and abundance of phytoplankton.]]
[[File:Upwelling image1.jpg|thumb|upright=1.7| This map by NOAA shows coastal areas where upwelling occurs. Nutrients that accompany upwelling can enhance phytoplankton abundance]]

A 2010 study published in ''Nature'' reported that marine phytoplankton had declined substantially in the world's oceans over the past century. Phytoplankton concentrations in surface waters were estimated to have decreased by about 40% since 1950, at a rate of around 1% per year, possibly in response to [[Earth:Effects of global warming on oceans|ocean warming]].<ref>{{cite journal |last1=Boyce |first1=Daniel G. |last2=Lewis |first2=Marlon R. |last3=Worm |first3=Boris |title=Global phytoplankton decline over the past century |journal=Nature |volume=466 |issue=7306 |pages=591–6 |year=2010 |pmid=20671703 |doi=10.1038/nature09268 |bibcode=2010Natur.466..591B }}</ref><ref>{{cite journal |last1=Schiermeier |first1=Quirin |title=Ocean greenery under warming stress |journal=Nature |year=2010 |doi=10.1038/news.2010.379 }}</ref> The study generated debate among scientists and led to several communications and criticisms, also published in ''Nature''.<ref>{{cite journal |last1=Mackas |first1=David L. |title=Does blending of chlorophyll data bias temporal trend? |journal=Nature |volume=472 |issue=7342 |pages=E4–5; discussion E8–9 |year=2011 |pmid=21490623 |doi=10.1038/nature09951 |bibcode=2011Natur.472E...4M }}</ref><ref name=pmid21490624>{{cite journal |last1=Rykaczewski |first1=Ryan R. |last2=Dunne |first2=John P. |title=A measured look at ocean chlorophyll trends |journal=Nature |volume=472 |issue=7342 |pages=E5–6; discussion E8–9 |year=2011 |pmid=21490624 |doi=10.1038/nature09952 |bibcode=2011Natur.472E...5R |url=https://zenodo.org/record/1233315 }}</ref><ref name=pmid21490624/><ref>{{cite journal |last1=McQuatters-Gollop |first1=Abigail |last2=Reid |first2=Philip C. |last3=Edwards |first3=Martin |last4=Burkill |first4=Peter H. |last5=Castellani |first5=Claudia |last6=Batten |first6=Sonia |last7=Gieskes |first7=Winfried |last8=Beare |first8=Doug |last9=Bidigare |first9=Robert R. |last10=Head |first10=Erica |last11=Johnson |first11=Rod |last12=Kahru |first12=Mati |last13=Koslow |first13=J. Anthony |last14=Pena |first14=Angelica |title=Is there a decline in marine phytoplankton? |journal=Nature |volume=472 |issue=7342 |pages=E6–7; discussion E8–9 |year=2011 |pmid=21490625 |doi=10.1038/nature09950 |bibcode=2011Natur.472E...6M }}</ref> In a 2014 follow-up study, the authors used a larger database of measurements and revised their analysis methods to account for several of the published criticisms, but ultimately reached similar conclusions to the original ''Nature'' study.<ref>{{cite journal |last1=Boyce |first1=Daniel G. |last2=Dowd |first2=Michael |last3=Lewis |first3=Marlon R. |last4=Worm |first4=Boris |title=Estimating global chlorophyll changes over the past century |journal=Progress in Oceanography |volume=122 |year=2014 |pages=163–73 |doi=10.1016/j.pocean.2014.01.004 |bibcode=2014PrOce.122..163B }}</ref> These studies and the need to understand the phytoplankon in the ocean led to the creation of the Secchi Disk Citizen Science study in 2013.<ref>{{cite web|url=http://www.secchidisk.org|title=Secchi Disk Study|publisher=}}</ref> The Secchi Disk study is a global study of phytoplankton conducted by seafarers (sailors, anglers, divers) involving a [[Earth:Secchi disk|Secchi Disk]] and a smartphone app.

Estimates of oceanic phytoplankton change are highly variable. One global ocean primary productivity study found a net increase in phytoplankton, as judged from measured [[Biology:Chlorophyll|chlorophyll]], when comparing observations in 1998–2002 to those conducted during a prior mission in 1979–1986.<ref>{{cite journal |last1=Antoine |first1=David |title=Bridging ocean color observations of the 1980s and 2000s in search of long-term trends |journal=Journal of Geophysical Research |volume=110 |issue=C6 |pages=C06009 |year=2005 |doi=10.1029/2004JC002620 |bibcode=2005JGRC..110.6009A }}</ref> Chlorophyll are photosynthetic pigments that are often used as an indicator of phytoplankton biomass. However, using the same database of measurements, other studies concluded that both chlorophyll and primary production had declined over this same time interval.<ref>{{cite journal |last1=Gregg |first1=Watson W. |last2=Conkright |first2=Margarita E. |last3=Ginoux |first3=Paul |last4=O'Reilly |first4=John E. |last5=Casey |first5=Nancy W. |title=Ocean primary production and climate: Global decadal changes |journal=Geophysical Research Letters |volume=30 |issue=15 |year=2003 |pages= 1809|doi=10.1029/2003GL016889 |bibcode=2003GeoRL..30.1809G |url=https://semanticscholar.org/paper/8577d71ddfb6f6885995050f84073a7eee37a530 }}</ref><ref>{{cite journal |last1=Gregg |first1=Watson W. |last2=Conkright |first2=Margarita E. |title=Decadal changes in global ocean chlorophyll |journal=Geophysical Research Letters |volume=29 |issue=15 |year=2002 |pages= 20–1–20–4|doi=10.1029/2002GL014689 |bibcode=2002GeoRL..29.1730G |hdl=2060/20010067778 |hdl-access=free }}</ref> The airborne fraction of CO<sub>2</sub> from human emissions, the percentage neither sequestered by photosynthetic life on land and sea nor absorbed in the oceans abiotically, has been almost constant over the past century, and that suggests a moderate upper limit on how much a component of the [[Earth:Carbon cycle|carbon cycle]] as large as phytoplankton have declined.<ref>{{cite journal |last1=Knorr |first1=Wolfgang |title=Is the airborne fraction of anthropogenic CO2emissions increasing? |journal=Geophysical Research Letters |volume=36 |issue=21 |pages=L21710 |year=2009 |doi=10.1029/2009GL040613 |bibcode=2009GeoRL..3621710K }}</ref> In the northeast Atlantic, where a relatively long chlorophyll data series is available, and the site of the [[Biology:Continuous Plankton Recorder|Continuous Plankton Recorder]] (CPR) survey, a net increase was found from 1948 to 2002.<ref>{{cite journal |last1=Raitsos |first1=Dionysios E. |title=Extending the SeaWiFS chlorophyll data set back 50 years in the northeast Atlantic |journal=Geophysical Research Letters |volume=32 |issue=6 |pages=L06603 |year=2005 |doi=10.1029/2005GL022484 |bibcode=2005GeoRL..32.6603R }}</ref> During 1998–2005, global ocean net primary productivity rose in 1998, followed by a decline during the rest of that period, yielding a small net increase.<ref>{{cite journal |last1=Behrenfeld |first1=Michael J. |last2=O’Malley |first2=Robert T. |last3=Siegel |first3=David A. |last4=McClain |first4=Charles R. |last5=Sarmiento |first5=Jorge L. |last6=Feldman |first6=Gene C. |last7=Milligan |first7=Allen J. |last8=Falkowski |first8=Paul G. |last9=Letelier |first9=Ricardo M. |last10=Boss |first10=Emmanuel S. |title=Climate-driven trends in contemporary ocean productivity |journal=Nature |volume=444 |issue=7120 |pages=752–5 |year=2006 |pmid=17151666 |doi=10.1038/nature05317 |bibcode=2006Natur.444..752B }}</ref> Using six climate model simulations, a large multi-university study of ocean ecosystems predicted "a global increase in primary production of 0.7% at the low end to 8.1% at the high end," by 2050 although with "very large regional differences" including "a contraction of the highly productive marginal sea ice biome by 42% in the Northern Hemisphere and 17% in the Southern Hemisphere."<ref>{{cite journal |last1=Sarmiento |first1=J. L. |last2=Slater |first2=R. |last3=Barber |first3=R. |last4=Bopp |first4=L. |last5=Doney |first5=S. C. |last6=Hirst |first6=A. C. |last7=Kleypas |first7=J. |last8=Matear |first8=R. |last9=Mikolajewicz |first9=U. |last10=Monfray |first10=P. |last11=Soldatov |first11=V. |last12=Spall |first12=S. A. |last13=Stouffer |first13=R. |title=Response of ocean ecosystems to climate warming |journal=Global Biogeochemical Cycles |volume=18 |issue=3 |pages=n/a |year=2004 |doi=10.1029/2003GB002134 |bibcode=2004GBioC..18.3003S |hdl=1912/3392 |hdl-access=free }}</ref> A more recent multi-model study estimated that primary production would decline by 2-20% by 2100 A.D.<ref name="ReferenceB"/> Despite substantial variation in both the magnitude and spatial pattern of change, the majority of published studies predict that phytoplankton biomass and/or primary production will decline over the next century.<ref name="ReferenceA"/><ref>{{cite journal |last1=Hofmann |first1=M |last2=Worm |first2=B |last3=Rahmstorf |first3=S |last4=Schellnhuber |first4=H J |title=Declining ocean chlorophyll under unabated anthropogenic CO2emissions |journal=Environmental Research Letters |volume=6 |issue=3 |year=2011 |doi=10.1088/1748-9326/6/3/034035 |pages=034035|bibcode=2011ERL.....6c4035H |doi-access=free }}</ref><ref>{{cite journal |last1=Boyd |first1=Philip W. |last2=Doney |first2=Scott C. |title=Modelling regional responses by marine pelagic ecosystems to global climate change |journal=Geophysical Research Letters |volume=29 |issue=16 |year=2002 |doi=10.1029/2001GL014130 | bibcode=2002GeoRL..29.1806B |pages=53–1–53–4|url=https://semanticscholar.org/paper/a793b94df63c7fa84f958ff90c70c98add1f3ae1 }}</ref><ref>{{cite journal |last1=Beaulieu |first1=C. |last2=Henson |first2=S. A. |last3=Sarmiento |first3=Jorge L. |last4=Dunne |first4=J. P. |last5=Doney |first5=S. C. |last6=Rykaczewski |first6=R. R. |last7=Bopp |first7=L. |title=Factors challenging our ability to detect long-term trends in ocean chlorophyll |journal=Biogeosciences |volume=10 |issue=4 |year=2013 |pages=2711–24 |doi=10.5194/bg-10-2711-2013 |bibcode=2013BGeo...10.2711B |url=http://darchive.mblwhoilibrary.org/bitstream/1912/6027/1/bg-10-2711-2013.pdf }}</ref><ref>{{cite journal |last1=Mace |first1=Georgina M. |last2=Mora |first2=Camilo |last3=Wei |first3=Chih-Lin |last4=Rollo |first4=Audrey |last5=Amaro |first5=Teresa |last6=Baco |first6=Amy R. |last7=Billett |first7=David |last8=Bopp |first8=Laurent |last9=Chen |first9=Qi |last10=Collier |first10=Mark |last11=Danovaro |first11=Roberto |last12=Gooday |first12=Andrew J. |last13=Grupe |first13=Benjamin M. |last14=Halloran |first14=Paul R. |last15=Ingels |first15=Jeroen |last16=Jones |first16=Daniel O. B. |last17=Levin |first17=Lisa A. |last18=Nakano |first18=Hideyuki |last19=Norling |first19=Karl |last20=Ramirez-Llodra |first20=Eva |last21=Rex |first21=Michael |last22=Ruhl |first22=Henry A. |last23=Smith |first23=Craig R. |last24=Sweetman |first24=Andrew K. |last25=Thurber |first25=Andrew R. |last26=Tjiputra |first26=Jerry F. |last27=Usseglio |first27=Paolo |last28=Watling |first28=Les |last29=Wu |first29=Tongwen |last30=Yasuhara |first30=Moriaki |title=Biotic and Human Vulnerability to Projected Changes in Ocean Biogeochemistry over the 21st Century |journal=PLOS Biology |volume=11 |issue=10 |year=2013 |pages=e1001682 |pmid=24143135 |pmc=3797030 |doi=10.1371/journal.pbio.1001682 }}</ref><ref>{{cite journal |last1=Taucher |first1=J. |last2=Oschlies |first2=A. |title=Can we predict the direction of marine primary production change under global warming? |journal=Geophysical Research Letters |volume=38 |issue=2 |pages=n/a |year=2011 |doi=10.1029/2010GL045934 |bibcode=2011GeoRL..38.2603T |url=http://oceanrep.geomar.de/11545/1/2010GL045934.pdf }}</ref><ref>{{cite journal |last1=Bopp |first1=Laurent |last2=Monfray |first2=Patrick |last3=Aumont |first3=Olivier |last4=Dufresne |first4=Jean-Louis |last5=Le Treut |first5=Hervé |last6=Madec |first6=Gurvan |last7=Terray |first7=Laurent |last8=Orr |first8=James C. |title=Potential impact of climate change on marine export production |journal=Global Biogeochemical Cycles |volume=15 |issue=1 |year=2001 |pages=81–99 |doi=10.1029/1999GB001256 |bibcode=2001GBioC..15...81B |url=https://semanticscholar.org/paper/25569a9b12bdc21407f3e73f4cc6499d87b6d440 }}</ref><ref>{{cite journal |last1=Cermeno |first1=P. |last2=Dutkiewicz |first2=S. |last3=Harris |first3=R. P. |last4=Follows |first4=M. |last5=Schofield |first5=O. |last6=Falkowski |first6=P. G. |title=The role of nutricline depth in regulating the ocean carbon cycle |journal=Proceedings of the National Academy of Sciences |volume=105 |issue=51 |pages=20344–9 |year=2008 |pmid=19075222 |jstor=25465827 |doi=10.1073/pnas.0811302106 |bibcode=2008PNAS..10520344C |pmc=2603260}}</ref><ref>{{cite journal |last1=Cox |first1=Peter M. |last2=Betts |first2=Richard A. |last3=Jones |first3=Chris D. |last4=Spall |first4=Steven A. |last5=Totterdell |first5=Ian J. |title=Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model |journal=Nature |volume=408 |issue=6809 |pages=184–7 |year=2000 |pmid=11089968 |doi=10.1038/35041539 |bibcode=2000Natur.408..184C }}</ref>

== Aquaculture ==
{{main|Biology:Algaculture}}
Phytoplankton are a key food item in both aquaculture and mariculture. Both utilize phytoplankton as food for the animals being farmed. In mariculture, the phytoplankton is naturally occurring and is introduced into enclosures with the normal circulation of seawater. In aquaculture, phytoplankton must be obtained and introduced directly. The plankton can either be collected from a body of water or cultured, though the former method is seldom used. Phytoplankton is used as a foodstock for the production of rotifers,<ref name=mcvey>McVey, James P., Nai-Hsien Chao, and Cheng-Sheng Lee. CRC Handbook of Mariculture Vol. 1 : Crustacean Aquaculture. New York: C R C P LLC, 1993.{{page needed|date=February 2016}}</ref> which are in turn used to feed other organisms. Phytoplankton is also used to feed many varieties of aquacultured molluscs, including [[Chemistry:Pearl|pearl]] oysters and [[Biology:Giant clam|giant clam]]s. A 2018 study estimated the nutritional value of natural phytoplankton in terms of carbohydrate, protein and lipid across the world ocean using ocean-colour data from satellites,<ref name=sroy>{{cite journal|last1=Roy|first1=Shovonlal|title=Distributions of phytoplankton carbohydrate, protein and lipid in the world oceans from satellite ocean colour|journal=The ISME Journal|volume=12|issue=6|pages=1457–1472|date=12 February 2018|doi=10.1038/s41396-018-0054-8|pmid=29434313|pmc=5955997|language=En|issn=1751-7370}}</ref> and found the calorific value of phytoplankton to vary considerably across different oceanic regions and between different time of the year.<ref name=sroy/><ref>{{cite news|title=Nutrition study reveals instability in world's most important fishing regions|url=https://phys.org/news/2018-02-nutrition-reveals-instability-world-important.html}}</ref>

The production of phytoplankton under artificial conditions is itself a form of aquaculture. Phytoplankton is cultured for a variety of purposes, including foodstock for other aquacultured organisms,<ref name=mcvey/> a nutritional supplement for captive invertebrates in aquaria. Culture sizes range from small-scale laboratory cultures of less than 1L to several tens of thousands of liters for commercial aquaculture.<ref name=mcvey/> Regardless of the size of the culture, certain conditions must be provided for efficient growth of plankton. The majority of cultured plankton is marine, and [[Earth:Seawater|seawater]] of a [[Physics:Specific gravity|specific gravity]] of 1.010 to 1.026 may be used as a culture medium. This water must be [[Biology:Sterilization (microbiology)|sterilized]], usually by either high temperatures in an [[Organization:Autoclave|autoclave]] or by exposure to ultraviolet radiation, to prevent biological [[Chemistry:Contamination|contamination]] of the culture. Various fertilizers are added to the culture medium to facilitate the growth of plankton. A culture must be aerated or agitated in some way to keep plankton suspended, as well as to provide dissolved [[Chemistry:Carbon dioxide|carbon dioxide]] for [[Earth:Photosynthesis|photosynthesis]]. In addition to constant aeration, most cultures are manually mixed or stirred on a regular basis. Light must be provided for the growth of phytoplankton. The colour temperature of illumination should be approximately 6,500 K, but values from 4,000 K to upwards of 20,000 K have been used successfully. The duration of light exposure should be approximately 16 hours daily; this is the most efficient artificial day length.<ref name=mcvey/>
{{clear}}

== See also ==
{{div col}}
* {{annotated link|Biology:Algae}}
* {{annotated link|Biology:Algaculture}}
* {{annotated link|Biology:AlgaeBase}}
* {{annotated link|Biology:Bacterioplankton}}
* {{annotated link|Biology:Biological pump}}
* {{annotated link|Astronomy:CLAW hypothesis}}
* {{annotated link|Biology:Cyanobacteria}}
* {{annotated link|Biology:Freshwater phytoplankton}}
* {{annotated link|Earth:Iron fertilization}}
* {{annotated link|Biology:Ocean acidification}}
* {{annotated link|Paradox of the plankton}}
* {{annotated link|Biology:Photosynthetic picoplankton}}
* {{annotated link|Earth:Plankton}}
* {{annotated link|Biology:Whiting event}}
* {{annotated link|Earth:Zooplankton}}
* {{annotated link|Earth:Thin layers (oceanography)}}
* {{annotated link|Earth:Harmful algal bloom}}
{{div col end}}

== References ==
{{Reflist}}

== Further reading ==
*{{cite book |last1=Greeson |first1=Phillip E. |year=1982 |title=An annotated key to the identification of commonly occurring and dominant genera of Algae observed in the Phytoplankton of the United States |location=Washington, D.C. |publisher=United States Government Printing Office |url=https://pubs.er.usgs.gov/publication/wsp2079 |isbn=978-0-607-68844-3 }}
*{{cite book |last1=Kirby |first1=Richard R. |year=2010 |title=Ocean Drifters: A Secret World Beneath the Waves |publisher=Studio Cactus  |isbn=978-1-904239-10-9 }}
*{{cite journal |last1=Martin |first1=Ronald |last2=Quigg |first2=Antonietta |title=Tiny Plants That Once Ruled the Seas |journal=Scientific American |volume=308 |issue=6 |year=2013 |pages=40–5 |pmid=23729069 |doi=10.1038/scientificamerican0613-40 |bibcode=2013SciAm.308f..40M }}

== External links ==
* [http://www.secchidisk.org Secchi Disk and Secchi app], a citizen science project to study the phytoplankton
* [http://vimeo.com/84872751/ Ocean Drifters], a short film narrated by David Attenborough about the varied roles of plankton
* [http://www.planktonchronicles.org/en Plankton Chronicles], a short documentary films & photos
* [https://web.archive.org/web/20150214081038/http://saga.pmel.noaa.gov/review/dms_climate.html DMS and Climate], NOAA
* [http://planktonnet.awi.de/ Plankton*Net], images of planktonic species

{{plankton|state=expanded}}
{{aquatic ecosystem topics|expanded=none}}


[[Category:Aquatic ecology]]
[[Category:Biological oceanography]]
[[Category:Planktology]]
[[Category:Climate change]]

{{Sourceattribution|Phytoplankton|1}}