This is an accepted version of this page Plankton are the diverse collection of organisms that drift in water (or air) but are unable to actively propel themselves against currents (or wind).

[3] In the ocean, they provide a crucial source of food to many small and large aquatic organisms, such as bivalves, fish, and baleen whales.

Marine plankton include bacteria, archaea, algae, protozoa, microscopic fungi,[4] and drifting or floating animals that inhabit the saltwater of oceans and the brackish waters of estuaries.

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.

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.

[10] Plankton are primarily divided into broad functional (or trophic level) groups: 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.

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.

Aeroplankton are tiny lifeforms that float and drift in the air, carried by the current of the wind; they are the atmospheric analogue to oceanic plankton.

[25][26] These materials can be transferred from the sea-surface to the atmosphere in the form of wind-generated aqueous aerosols due to their high vapour tension and a process known as volatilisation.

[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%).

[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).

Water bears, despite only having lifespans of a few months, famously can enter suspended animation during dry or hostile conditions and survive for decades.

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.

Holoplankton can be contrasted with meroplankton, which are planktic organisms that spend part of their life cycle in the benthic zone.

Examples of holoplankton include some diatoms, radiolarians, some dinoflagellates, foraminifera, amphipods, krill, copepods, and salps, as well as some gastropod mollusk species.

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.

By themselves these animals cannot float, which contrasts them with true planktonic organisms, such as Velella and the Portuguese Man o' War, which are buoyant.

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.

Although large areas of the 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.

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

Organic material tends to be denser than seawater, so it sinks into open ocean ecosystems away from the coastlines, transporting carbon along with it.

[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.

For example, at interannual scales phytoplankton levels temporarily plummet during El Niño periods, influencing populations of zooplankton, fishes, sea birds, and marine mammals.

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.

Natural factors (e.g., current variations, temperature changes) and man-made factors (e.g. river dams, ocean acidification, rising temperatures) can strongly affect zooplankton populations, which can in turn strongly affect fish larval survival, and therefore breeding success.

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.