Phytoplankton 50557 225164954 2008-07-12T06:21:30Z Plumbago 125900 Revert : word "class" has taxonomic connotations inappropriate here; restore text about size and visibility ("invisible" confuses things IMHO) [[Image:phytopla.gif|thumb|right|150px|Diagrams of some typical phytoplankton]] '''Phytoplankton''' are the [[autotroph]]ic component of [[plankton]]. The name comes from the [[Greek language|Greek]] terms, ''phyton'' or "[[plant]]" and πλαγκτος ("planktos"), meaning "wanderer" or "drifter".<ref>{{cite book | last = Thurman | first = H. V. | year = 1997 | title = Introductory Oceanography | publisher = Prentice Hall College | location = New Jersey, USA | ISBN = 0132620723 }}</ref> Most phytoplankton are too small to be individually seen with the [[naked eye|unaided eye]]. However, when present in high enough numbers, they may appear as a green discoloration of the water due to the presence of [[chlorophyll]] within their cells (although the actual color may vary with the species of phytoplankton present due to varying levels of chlorophyll or the presence of accessory pigments such as [[phycobiliprotein]]s, [[xanthophyll]]s, etc.). ==Ecology== [[Image:Phytoplankton SoAtlantic 20060215.jpg|thumb|right|150px|[[Algal bloom|Phytoplankton bloom]] in the South Atlantic (February 15, 2006) seen from space]] Phytoplankton obtain energy through a process called [[photosynthesis]] and must therefore live in the well-lit surface layer (termed the [[Photic zone|euphotic zone]]) of an [[ocean]], [[sea]], [[lake]], or other body of water. Through photosynthesis, phytoplankton are responsible for much of the [[oxygen]] present in the [[Earth's atmosphere]] &ndash; half of the total amount produced by all plant life.<ref>[http://earthobservatory.nasa.gov/Newsroom/NasaNews/2005/2005030218443.html NASA Earth Observatory - Satellite sees ocean plants increate]</ref> Their cumulative energy fixation in carbon compounds ([[primary production]]) is the basis for the vast majority of oceanic and also many [[freshwater]] [[food web]]s ([[chemosynthesis]] is a notable exception). As a side note, one of the more remarkable [[food chain]]s in the ocean &ndash; remarkable because of the small number of links &ndash; is that of phytoplankton fed on by [[krill]] (a type of shrimp) fed on by [[baleen]] [[whale]]s. Phytoplankton are also crucially dependent on minerals. These are primarily [[macronutrient (ecology)|macronutrients]] such as [[nitrate]], [[phosphate]] or [[silicic acid]], whose availability is governed by the balance between the so-called [[biological pump]] and [[upwelling]] of deep, nutrient-rich waters. However, across large regions of the [[World Ocean]] such as the [[Southern Ocean]], phytoplankton are also limited by the lack of the [[micronutrient]] [[iron]]. This has led to some scientists advocating [[iron fertilization]] as a means to counteract the accumulation of human-produced carbon dioxide (CO<sub>2</sub>) in the [[atmosphere]]<ref>{{Citation | first = M. | last = Richtel | title = Recruiting Plankton to Fight Global Warming | newspaper = New York Times | year = 2007 | date = May 1, 2007 | url = http://www.nytimes.com/2007/05/01/business/01plankton.html?ref=science}}</ref>. While almost all phytoplankton species are obligate [[photoautotroph]]s, there are some that are [[mixotrophic]] and other, non-pigmented species that are actually [[heterotroph]]ic (the latter are often viewed as [[zooplankton]]). Of these, the best known are [[dinoflagellate]] [[genus|genera]] such as ''[[Noctiluca]]'' and ''[[Dinophyceae|Dinophysis]]'', that obtain organic carbon by [[ingestion|ingesting]] other organisms or [[detritus (biology)|detrital]] material. [[Image:Diatoms through the microscope.jpg|thumb|right|150px|Diatoms]] [[Image:Ceratium hirundinella.jpg|thumb|right|150px|Dinoflagellate]] The term phytoplankton encompasses all photoautotrophic microorganisms in aquatic [[food web]]s. Phytoplankton serve as the base of the aquatic food web, providing an essential ecological function for all aquatic life. However, unlike terrestrial [[communities]], where most autotrophs are [[plants]], phytoplankton are a diverse group, incorporating [[protista]]n [[eukaryote]]s and both [[Bacteria|eubacterial]] and [[archaebacteria]]l [[prokaryote]]s. There are about 5,000 species of marine phytoplankton.<ref name="Hallegraeff 03">Hallegraeff, G.M. (2003). Harmful algal blooms: a global overview. ''in'' Hallegraeff, G.M., Andewrson, D.M. and Cembella, A.D. (eds) 2003. ''Manual on Harmful Marine Microalgae.'' UNESCO, Paris</ref> There is uncertainty in how such diversity has evolved in an environment where competition for only a few resources would suggest limited potential for [[niche differentiation]].<ref> {{cite journal |author=G.E. Hutchinson |year=1961 |title=The paradox of the plankton |journal=Am. Nat. |volume=95 |pages=137–145 | doi = 10.1086/282171 <!--Retrieved from CrossRef by DOI bot--> }}</ref> In terms of numbers, the most important groups of phytoplankton include the [[diatom]]s, [[cyanobacteria]] and [[dinoflagellate]]s, although many other groups of [[alga]]e are represented. One group, the [[coccolithophore|coccolithophorids]], is responsible (in part) for the release of significant amounts of [[dimethyl sulfide]] (DMS) into the [[Earth's atmosphere|atmosphere]]. DMS is converted to sulfate and these sulfate molecules act as [[cloud condensation nuclei]], increasing general cloud cover. In [[oligotrophic]] oceanic regions such as the [[Sargasso Sea]] or the [[Pacific Ocean|South Pacific]] [[gyre]], phytoplankton is dominated by the small sized cells, called [[Photosynthetic picoplankton|picoplankton]], mostly composed of [[cyanobacteria]] (''[[Prochlorococcus]]'', ''[[Synechococcus]]'') and picoeucaryotes such as ''[[Micromonas]]''. ==References== <references /> ==See also== * [[Algae]] * [[Algae culture]] * [[Bacterioplankton]] * [[Biological pump]] * [[Iron fertilization]] * [[Microalgae]] * [[Microphyte]] * [[Ocean acidification]] * [[Photosynthetic picoplankton]] * [[Plankton]] * [[Zooplankton]] ==External links== * [http://saga.pmel.noaa.gov/review/dms_climate.html NOAA, DMS and Climate] * [http://planktonnet.sb-roscoff.fr/index.php Plankton*Net] : Images of planktonic species [[Category:Aquatic ecology]] [[Category:Biological oceanography]] [[Category:Planktology]] [[bg:Фитопланктон]] [[cs:Fytoplankton]] [[da:Planteplankton]] [[de:Phytoplankton]] [[et:Fütoplankton]] [[es:Fitoplancton]] [[fr:Phytoplancton]] [[gd:Luibhean-luaisgein]] [[gl:Fitoplancto]] [[hr:Fitoplankton]] [[id:Fitoplankton]] [[it:Fitoplancton]] [[he:פיטופלנקטון]] [[nl:Fytoplankton]] [[ja:植物プランクトン]] [[nn:Planteplankton]] [[pl:Fitoplankton]] [[pt:Fitoplâncton]] [[ro:Fitoplancton]] [[sv:Fytoplankton]] [[uk:Фітопланктон]] [[zh:浮游植物]]