Editing Plankton (section)

== Distribution ==
[[File:Plankton satellite image.jpg|thumb|400px|right| {{center|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.}}]]

Apart from aeroplankton, plankton inhabits oceans, seas, lakes and ponds. Local abundance varies horizontally, vertically and seasonally. The primary cause of this variability is the availability of light. All plankton ecosystems are driven by the input of solar energy (but see [[chemosynthesis]]), confining [[primary production]] to surface waters, and to geographical regions and seasons having abundant light.

A secondary variable is nutrient availability. Although large areas of the [[tropics|tropical]] and [[sub-tropical]] oceans have abundant light, they experience relatively low primary production because they offer limited nutrients such as [[nitrate]], [[phosphate]] and [[silicate]]. This results from large-scale [[ocean current|ocean circulation]] and water column [[Ocean stratification|stratification]]. In such regions, primary production usually occurs at greater depth, although at a reduced level (because of reduced light).

Despite significant [[macronutrient]] concentrations, some ocean regions are unproductive (so-called [[HNLC|HNLC regions]]).<ref>{{Cite journal   
| last = Martin | first = J.H. 
| author2=Fitzwater, S.E. | year=1988
| title = Iron-deficiency limits phytoplankton growth in the Northeast Pacific Subarctic
| journal= Nature | volume=331 | pages=341–343
| doi= 10.1038/331341a0 | issue=6154
| bibcode=1988Natur.331..341M
| s2cid = 4325562 
}}</ref> The [[micronutrient]] [[iron]] is deficient in these regions, and [[iron fertilization|adding it]] can lead to the formation of phytoplankton [[algal bloom]]s.<ref>{{Cite journal   
| last1 = Boyd | first1 = P.W. | year=2000   
| title = A mesoscale phytoplankton bloom in the polar Southern Ocean stimulated by fertilization   
| journal=Nature | volume=407 | pages=695–702   
| doi = 10.1038/35037500 | pmid = 11048709   
| last2 = Watson | first2 = AJ   
| last3 = Law | first3 = CS   
| last4 = Abraham | first4 = ER   
| last5 = Trull | first5 = T   
| last6 = Murdoch | first6 = R   
| last7 = Bakker | first7 = DC   
| last8 = Bowie | first8 = AR   
| last9 = Buesseler | first9 = KO   
| issue = 6805 
| display-authors = 1   | bibcode = 2000Natur.407..695B 
| s2cid = 4368261 }}</ref> Iron primarily reaches the ocean through the deposition of dust on the sea surface. Paradoxically, oceanic areas adjacent to unproductive, [[arid]] land thus typically have abundant phytoplankton (e.g., the eastern [[Atlantic Ocean]], where [[trade winds]] bring dust from the [[Sahara Desert]] in north [[Africa]]).

While plankton are most abundant in surface waters, they live throughout the water column. At depths where no primary production occurs, [[zooplankton]] and [[bacterioplankton]] instead consume organic material sinking from more productive surface waters above. This flux of sinking material, so-called [[marine snow]], can be especially high following the termination of [[spring bloom]]s.

The local distribution of plankton can be affected by wind-driven [[Langmuir circulation]] and the [[Langmuir circulation#Biological effects|biological effects]] of this physical process.