Page protected with pending changes
Source: Wikipedia, the free encyclopedia.

fish eggs
, crab larvae, worm larvae).

Plankton are the diverse collection of

bivalves, fish, and baleen whales

Marine plankton include

estuaries. Freshwater plankton are similar to marine plankton, but are found in lakes and rivers. Mostly plankton just drift where currents take them, though some, like jellyfish
, swim slowly but not fast enough to generally gain control from the influence of currents.

Although plankton are usually thought of as inhabiting water, there are also airborne versions that live part of their lives drifting in the atmosphere. These

plant spores, pollen and wind-scattered seeds. They may also include microorganisms swept into the air from terrestrial dust storms and oceanic plankton swept into the air by sea spray

Though many planktonic species are microscopic in size, plankton includes organisms over a wide range of sizes, including large organisms such as jellyfish.[5] This is because plankton are defined by their ecological niche and level of motility rather than by any phylogenetic or taxonomic classification. The "plankton" category differentiates these organisms from those that float on the water's surface, called neuston, those that can swim against a current, called nekton, and those that live on the deep sea floor, called benthos.


Plankton (organisms that drift with water currents) can be contrasted with nekton (organisms that swim against water currents), neuston (organisms that live at the ocean surface) and benthos (organisms that live at the ocean floor).

The name plankton was coined by German marine biologist Victor Hensen in 1887 from shortening the word halyplankton from Greek ᾰ̔́λς háls "sea" and πλανάω planáō to "drift" or "wander".[6]: 1  While some forms are capable of independent movement and can swim hundreds of meters vertically in a single day (a behavior called diel vertical migration), their horizontal position is primarily determined by the surrounding water movement, and plankton typically flow with ocean currents. This is in contrast to nekton organisms, such as fish, squid and marine mammals, which can swim against the ambient flow and control their position in the environment.

Within the plankton, holoplankton spend their entire life cycle as plankton (e.g. most algae, copepods, salps, and some jellyfish). By contrast, meroplankton are only planktic for part of their lives (usually the larval stage), and then graduate to either a nektic (swimming) or benthic (sea floor) existence. Examples of meroplankton include the larvae of sea urchins, starfish, crustaceans, marine worms, and most fish.[7]

The amount and distribution of plankton depends on available nutrients, the state of water and a large amount of other plankton.[8]

The study of plankton is termed planktology and a planktonic individual is referred to as a plankter.[9] The adjective planktonic is widely used in both the scientific and popular literature, and is a generally accepted term. However, from the standpoint of prescriptive grammar, the less-commonly used planktic is more strictly the correct adjective. When deriving English words from their Greek or Latin roots, the gender-specific ending (in this case, "-on" which indicates the word is neuter) is normally dropped, using only the root of the word in the derivation.[10]

Trophic groups

Plankton are primarily divided into broad functional (or trophic level) groups:


  • Mixotrophs. Plankton have traditionally been categorized as producer, consumer, and recycler groups, but some plankton are able to benefit from more than just one trophic level. In this mixed trophic strategy—known as mixotrophy—organisms act as both producers and consumers, either at the same time or switching between modes of nutrition in response to ambient conditions. This makes it possible to use photosynthesis for growth when nutrients and light are abundant, but switching to eat phytoplankton, zooplankton, or each other when growing conditions are poor. Mixotrophs are divided into two groups; constitutive mixotrophs, CMs, which are able to perform photosynthesis on their own, and non-constitutive mixotrophs, NCMs, which use phagocytosis to engulf phototrophic prey that are either kept alive inside the host cell, which benefit from its photosynthesis, or they digest their prey except for the plastids, which continues to perform photosynthesis (kleptoplasty).[14]

Recognition of the importance of mixotrophy as an ecological strategy is increasing,[15] as well as the wider role this may play in marine biogeochemistry.[16] Studies have shown that mixotrophs are much more important for marine ecology than previously assumed and comprise more than half of all microscopic plankton.[17][18] Their presence acts as a buffer that prevents the collapse of ecosystems during times with little to no light.[19]

Size groups

multicellular organisms with different sizes, shapes, feeding strategies, ecological functions, life cycle characteristics, and environmental sensitivities.[20]
Courtesy of Christian Sardet/CNRS/Tara expeditions

Plankton are also often described in terms of size. Usually the following divisions are used: [21]

Group Size range
Megaplankton > 20 cm
Cephalopoda; Amphipoda
Macroplankton 2→20 cm
Cephalopoda; Janthina and Recluzia (two genera of gastropods); Amphipoda
Mesoplankton 0.2→20 mm
Microplankton 20→200 μm large
metazoans – Crustacea (copepod
Nanoplankton 2→20 μm small
Picoplankton 0.2→2 μm small
bacteria; Chrysophyta
Femtoplankton < 0.2 μm
marine viruses

However, some of these terms may be used with very different boundaries, especially on the larger end. The existence and importance of nano- and even smaller plankton was only discovered during the 1980s, but they are thought to make up the largest proportion of all plankton in number and diversity.

The microplankton and smaller groups are microorganisms and operate at low Reynolds numbers, where the viscosity of water is more important than its mass or inertia. [22]

  • Plankton sizes by taxonomic groups [23]
    Plankton sizes by taxonomic groups[23]

Habitat groups

Marine plankton

Marine plankton includes marine bacteria and archaea, algae, protozoa and drifting or floating animals that inhabit the saltwater of oceans and the brackish waters of estuaries.

Freshwater plankton

Freshwater plankton are similar to marine plankton, but are found inland in the freshwaters of lakes and rivers.


analogue to oceanic plankton. Most of the living things that make up aeroplankton are very small to microscopic in size, and many can be difficult to identify because of their tiny size. Scientists can collect them for study in traps and sweep nets from aircraft, kites or balloons.[24] Aeroplankton is made up of numerous microbes, including viruses, about 1000 different species of bacteria, around 40,000 varieties of fungi, and hundreds of species of protists, algae, mosses and liverworts that live some part of their life cycle as aeroplankton, often as spores, pollen, and wind-scattered seeds
. Additionally, peripatetic microorganisms are swept into the air from terrestrial dust storms, and an even larger amount of airborne marine microorganisms are propelled high into the atmosphere in sea spray. Aeroplankton deposits hundreds of millions of airborne viruses and tens of millions of bacteria every day on every square meter around the planet.


microbes can be transported long distances to coastal regions. If they hit land they can have an effect on animal, vegetation and human health.[28] Marine aerosols that contain viruses can travel hundreds of kilometers from their source and remain in liquid form as long as the humidity is high enough (over 70%).[29][30][31] These aerosols are able to remain suspended in the atmosphere for about 31 days.[32] Evidence suggests that bacteria can remain viable after being transported inland through aerosols. Some reached as far as 200 meters at 30 meters above sea level.[33] The process which transfers this material to the atmosphere causes further enrichment in both bacteria and viruses in comparison to either the SML or sub-surface waters (up to three orders of magnitude in some locations).[33]


Many animals live in terrestrial environments by thriving in transient often microscopic bodies of water and moisture, these include rotifers and gastrotrichs which lay resilient eggs capable of surviving years in dry environments, and some of which can go dormant themselves. Nematodes are usually microscopic with this lifestyle. Water bears, despite only having lifespans of a few months, famously can enter suspended animation during dry or hostile conditions and survive for decades. This allows them to be ubiquitous in terrestrial environments despite needing water to grow and reproduce. Many microscopic crustacean groups like copepods and amphipods (of which sandhoppers are members) and seed shrimp are known to go dormant when dry and live in transient bodies of water too[34]

Other groups

Gelatinous zooplankton

Jellyfish are gelatinous zooplankton.[35]

Arthropoda, contain gelatinous species, but many of those odd species live in the open ocean and the deep sea and are less available to the casual ocean observer.[38]


Salmon egg hatching into a sac fry. In a few days, the sac fry will absorb the yolk sac and start feeding on smaller plankton.

planktonic, meaning they cannot swim effectively under their own power, but must drift with the ocean currents. Fish eggs cannot swim at all, and are unambiguously planktonic. Early stage larvae swim poorly, but later stage larvae swim better and cease to be planktonic as they grow into juveniles. Fish larvae are part of the zooplankton that eat smaller plankton, while fish eggs carry their food supply. Both eggs and larvae are themselves eaten by larger animals.[39][40] Fish can produce high numbers of eggs which are often released into the open water column. Fish eggs typically have a diameter of about 1 millimetre (0.039 in). The newly hatched young of oviparous fish are called larvae. They are usually poorly formed, carry a large yolk sac (for nourishment), and are very different in appearance from juvenile and adult specimens. The larval period in oviparous fish is relatively short (usually only several weeks), and larvae rapidly grow and change appearance and structure (a process termed metamorphosis) to become juveniles. During this transition larvae must switch from their yolk sac to feeding on zooplankton prey, a process which depends on typically inadequate zooplankton density, starving many larvae. In time fish larvae become able to swim against currents, at which point they cease to be plankton and become juvenile fish


Tomopteris, a holoplanktic bioluminescence polychaete worm[41]

gastropod mollusk species. Holoplankton dwell in the pelagic zone as opposed to the benthic zone.[42] Holoplankton include both phytoplankton and zooplankton and vary in size. The most common plankton are protists.[43]


Larva stage of a spiny lobster

seafloor. The larval stages of benthic invertebrates make up a significant proportion of planktonic communities.[45] The planktonic larval stage is particularly crucial to many benthic invertebrates in order to disperse their young. Depending on the particular species and the environmental conditions, larval or juvenile-stage meroplankton may remain in the pelagic zone for durations ranging from hours to months.[34]


Portuguese Man o' War, which are buoyant. Pseudoplankton are often found in the guts of filtering zooplankters.[46]


Tychoplankton are organisms, such as free-living or attached benthic organisms and other non-planktonic organisms, that are carried into the plankton through a disturbance of their benthic habitat, or by winds and currents.[47] This can occur by direct turbulence or by disruption of the substrate and subsequent entrainment in the water column.[47][48] Tychoplankton are, therefore, a primary subdivision for sorting planktonic organisms by duration of lifecycle spent in the plankton, as neither their entire lives nor particular reproductive portions are confined to planktonic existence.[49] Tychoplankton are sometimes called accidental plankton.

Mineralized plankton


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

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 circulation and water column stratification
. In such regions, primary production usually occurs at greater depth, although at a reduced level (because of reduced light).

Despite significant


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 blooms.

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

Ecological significance

Food chain

External videos
video icon The Secret Life of Plankton - YouTube

Aside from representing the bottom few levels of a food chain that supports commercially important fisheries, plankton ecosystems play a role in the biogeochemical cycles of many important chemical elements, including the ocean's carbon cycle.[52] Fish larvae mainly eat zooplankton, which in turn eat phytoplankton[53]

Carbon cycle

Primarily by grazing on phytoplankton, zooplankton provide

foodweb, either respiring it to provide metabolic energy, or upon death as biomass or detritus. Organic material tends to be denser than seawater, so it sinks into open ocean ecosystems away from the coastlines, transporting carbon along with it. This process, called the biological pump, is one reason that oceans constitute the largest carbon sink on Earth. However, it has been shown to be influenced by increments of temperature.[54][55][56][57] In 2019, a study indicated that at ongoing rates of seawater acidification, Antarctic phytoplanktons could become smaller and less effective at storing carbon before the end of the century.[58]

It might be possible to increase the ocean's uptake of

oxygen depletion and resultant methane production (caused by the excess production remineralising at depth) is one potential drawback.[59][60]

Oxygen production

Phytoplankton absorb energy from the Sun and nutrients from the water to produce their own nourishment or energy. In the process of photosynthesis, phytoplankton release molecular oxygen (O
) into the water as a waste byproduct. It is estimated that about 50% of the world's oxygen is produced via phytoplankton photosynthesis.[61] The rest is produced via photosynthesis on land by plants.[61] Furthermore, phytoplankton photosynthesis has controlled the atmospheric CO
balance since the early Precambrian Eon.[62]

Absorption efficiency

The absorption efficiency (AE) of plankton is the proportion of food absorbed by the plankton that determines how available the consumed organic materials are in meeting the required physiological demands.

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.[64][65] 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.[66]

Biomass variability

The growth of phytoplankton populations is dependent on light levels and nutrient availability. The chief factor limiting growth varies from region to region in the world's oceans. On a broad scale, growth of phytoplankton in the oligotrophic tropical and subtropical gyres is generally limited by nutrient supply, while light often limits phytoplankton growth in subarctic gyres. Environmental variability at multiple scales influences the nutrient and light available for phytoplankton, and as these organisms form the base of the marine food web, this variability in phytoplankton growth influences higher trophic levels. For example, at interannual scales phytoplankton levels temporarily plummet during

El Niño periods, influencing populations of zooplankton, fishes, sea birds, and marine mammals

The effects of 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 impacts on future phytoplankton productivity.[67] Additionally, changes in the mortality of phytoplankton due to rates of zooplankton grazing may be significant.

Marine phytoplankton cycling throughout water column
Amphipod with curved exoskeleton and two long and two short antennae

Plankton diversity

Planktonic relationships

Fish & plankton

Zooplankton are the initial prey item for almost all

fish larvae as they switch from their yolk sacs to external feeding. Fish rely on the density and distribution of zooplankton to match that of new larvae, which can otherwise starve. Natural factors (e.g., current variations, temperature changes) and man-made factors (e.g. river dams, ocean acidification
, rising temperatures) can strongly affect zooplankton, which can in turn strongly affect larval survival, and therefore breeding success.

It's been shown that plankton can be patchy in marine environments where there aren't significant fish populations and additionally, where fish are abundant, zooplankton dynamics are influenced by the fish predation rate in their environment. Depending on the predation rate, they could express regular or chaotic behavior.[69]

A negative effect that fish larvae can have on planktonic algal blooms is that the larvae will prolong the blooming event by diminishing available zooplankton numbers; this in turn permits excessive phytoplankton growth allowing the bloom to flourish .[53]

The importance of both phytoplankton and zooplankton is also well-recognized in extensive and semi-intensive pond fish farming. Plankton population-based pond management strategies for fish rearing have been practiced by traditional fish farmers for decades, illustrating the importance of plankton even in man-made environments.

Whales & plankton

Of all animal fecal matter, it is whale feces that is the 'trophy' in terms of increasing nutrient availability. Phytoplankton are the powerhouse of open ocean primary production and they can acquire many nutrients from whale feces.[70] In the marine food web, phytoplankton are at the base of the food web and are consumed by zooplankton & krill, which are preyed upon by larger and larger marine organisms, including whales, so it can be said that whale poop fuels the entire food web.

Humans & plankton

Plankton have many direct and indirect effects on humans.

Around 70% of the oxygen in the atmosphere is produced in the oceans from phytoplankton performing photosynthesis, meaning that the majority of the oxygen available for us and other organisms that respire aerobically is produced by plankton.[71]

Plankton also make up the base of the marine food web, providing food for all the trophic levels above. Recent studies have analyzed the marine food web to see if the system runs on a

top-down or bottom-up approach. Essentially, this research is focused on understanding whether changes in the food web are driven by nutrients at the bottom of the food web or predators at the top. The general conclusion is that the bottom-up approach seemed to be more predictive of food web behavior.[72]
This indicates that plankton have more sway in determining the success of the primary consumer species that prey on them than do the secondary consumers that prey on the primary consumers.

In some cases, plankton act as an intermediate host for deadly parasites in humans. One such case is that of cholera, an infection caused by several strains of Vibrio cholerae. These species have been shown to have a symbiotic relationship with chitinous zooplankton species like copepods. These bacteria benefit not only from the food provided by the chiton from the zooplankton, but also from the protection from acidic environments. Once the copepods have been ingested by a human host, the chitinous exterior protects the bacteria from the stomach acids in the stomach and proceed to the intestines. Once there, the bacteria bind with the surface of the small intestine and the host will start developing symptoms, including extreme diarrhea, within five days.[73]

See also


  1. .
  2. .
  3. ^ "plankter". American Heritage Dictionary. Houghton Mifflin Harcourt Publishing Company. Archived from the original on 9 November 2018. Retrieved 9 November 2018.
  4. .
  5. ^ Dolan, John (November 2012). "Microzooplankton: the microscopic (micro) animals (zoo) of the plankton" (PDF). Institut océanographique. Archived from the original (PDF) on 4 March 2016. Retrieved 16 January 2014.
  6. ^ Hansen, Victor (1887). "Uber die Bestimmung des Plankton's oder des im Meere treibenden Materials an Pflanzen und Thieren" [On the determination of the plankton or the material floating in the sea on plants and animals]. Fünfter Bericht der Kommission zur Wissenschaftlichen Untersuchung der Deutschen Meere (in German). 12 (12–16). Berlin, Germany: Paul Parey: 1-108 – via Biodiversity Heritage Library.
  7. .
  8. . Retrieved 2 April 2018.
  9. ^ "Plankter – marine biology". Encyclopædia Britannica.
  10. S2CID 131283465
  11. .
  12. .
  13. ^ "Plankton". Resource Library. National Geographic. Retrieved 13 September 2019.
  14. .
  15. .
  16. .
  17. ^ "Mixing It Up in the Web of Life". The Scientist Magazine.
  18. ^ "Uncovered: the mysterious killer triffids that dominate life in our oceans". 3 November 2016.
  19. ^ "Catastrophic Darkness". Astrobiology Magazine. Archived from the original on 2015-09-26. Retrieved 2019-11-27.
  20. .
  21. .
  22. .
  23. .
  24. ^ A. C. Hardy and P. S. Milne (1938) Studies in the Distribution of Insects by Aerial Currents. Journal of Animal Ecology, 7(2):199-229
  25. OCLC 34933503
  26. ^ Blanchard, D.C., 1983. The production, distribution and bacterial enrichment of the sea-salt aerosol. In: Liss, P.S., Slinn, W.G.N. ŽEds.., Air–Sea Exchange of Gases and Particles. D. Reidel Publishing Co., Dordrecht, Netherlands, pp. 407-444.
  27. ^ Wallace Jr., G.T., Duce, R.A., 1978. Transport of particulate organic matter by bubbles in marine waters. Limnol. Oceanogr. 23 Ž6., 1155–1167.
  28. ^ WHO, 1998. Draft guidelines for safe recreational water environments: coastal and fresh waters, draft for consultation. World Health Organization, Geneva, EOSrDRAFTr98 14, pp. 207–299.
  29. ^ Klassen, R. D., & Roberge, P. R. (1999). Aerosol transport modeling as an aid to understanding atmospheric corrosivity patterns. Materials & Design, 20, 159–168.
  30. ^ Moorthy, K. K., Satheesh, S. K., & Krishna Murthy, B.V. (1998). Characteristics ofspectral optical depths and size distributions of aerosols over tropical oceanic regions. Journal of Atmospheric and Solar–Terrestrial Physics, 60, 981–992.
  31. ^ Chow, J. C., Watson, J. G., Green, M. C., Lowenthal, D. H., Bates, B., Oslund, W., & Torre, G. (2000). Cross-border transport and spatial variability of suspended particles in Mexicali and California's Imperial Valley. Atmospheric Environment, 34, 1833–1843.
  32. ^ Aller, J., Kuznetsova, M., Jahns, C., Kemp, P. (2005) The sea surface microlayer as a source of viral and bacterial enrichment in marine aerosols. Journal of aerosol science. Vol. 36, pp. 801-812.
  33. ^ a b Marks, R., Kruczalak, K., Jankowska, K., & Michalska, M. (2001). Bacteria and fungi in air over the GulfofGdansk and Baltic sea. Journal of Aerosol Science, 32, 237–250.
  34. ^ .
  35. .
  36. ^ Lalli, C.M. & Parsons, T.R. (2001) Biological Oceanography. Butterworth-Heinemann.
  37. ^ Johnsen, S. (2000) Transparent Animals. Scientific American 282: 62-71.
  38. ^ Nouvian, C. (2007) The Deep. University of Chicago Press.
  39. ^ What are Ichthyoplankton? Southwest Fisheries Science Center, NOAA. Modified 3 September 2007. Retrieved 22 July 2011.
  40. .
  41. ^ Harvey, Edmund Newton (1952). Bioluminescence. Academic Press.
  42. ^ Anderson, Genny. "Marine Plankton". Marine Science. Retrieved 2012-04-04.
  43. ^ Talks, Ted. "Zooplankton". Marine Life/Marine Invertebrates. Archived from the original on 2017-12-07. Retrieved 2012-04-04.
  44. ^ "Plankton". Britannica. Retrieved 2020-06-13.
  45. S2CID 199638114
  46. .
  47. ^ .
  48. .
  49. on 2013-01-20.
  50. .
  51. .
  52. ]
  53. ^ .
  54. .
  55. .
  56. .
  57. .
  58. ^ Petrou, Katherina; Nielsen, Daniel (2019-08-27). "Acid oceans are shrinking plankton, fueling faster climate change". Retrieved 2019-09-07.
  59. S2CID 130687109
  60. .
  61. ^ a b Roach, John (June 7, 2004). "Source of Half Earth's Oxygen Gets Little Credit". National Geographic News. Archived from the original on June 8, 2004. Retrieved 2016-04-04.
  62. .
  63. .
  64. .
  65. .
  66. .
  67. .
  68. ^ Michael Le Page (March 2019). "Animal with an anus that comes and goes could reveal how ours evolved". New Scientist.
  69. PMID 11497628
  70. ^ "whale poop and phytoplankton, fighting climate change". IFAW. Retrieved 2022-03-29.
  71. S2CID 8637912
  72. .
  73. .

Further reading

External links