Plankton - SpeedyLook encyclopedia

Productivity

It depends on the availability in nutrients (the lack of iron seems for example a limiting factor), of the presence of Toxique S in water, of the temperature of water and for the phytoplankton of the quantity of light and its quality. The productivity, related to the biomass, is higher in cool water, generally denser and rich in nutrients. In spite of an increase in productivity in north, around the poles, and in spite of some spectacular bloom S buildings, the planktonique activity seems in reduction with planetary scales of 1999 with 2006.
The plankton is at the base many trophic networks.

Types of plankton

the vegetable plankton, or Phytoplankton (of the Greek φυτόν / phutón or “Plant”), is built starting from biogenic salts. Except for the nanoplancton and the picoplancton, it is primarily present in the surface layers of the sea (from 0 to 15 meters of depth), where it achieves its Photosynthèse. I.e. it absorbs Rock salt and carbon dioxide to reject oxygen under the effect of the light.

the animal plankton, or Zooplancton (of the Greek ζῷον / zõio or “Animal”), nourishes living matter, certain species being Herbivore S and others carnivorous. It goes up the night towards surface to nourish Phytoplancton and goes down again during the day towards deeper water. He thus escapes predatory and saves energy because the temperature is less high. This movement of the zooplancton, which contributes to the mixing of water and of the layers of varied temperatures or variously oxygenated daily or nychthemeral vertical migration is called - a nycthémère, of the Greek νυκτ- / nukt- , night, and ἡμέρα/ will hêméra , day, indicates one 24 hours duration. Certain predatory of the plankton these movements follow. On certain littorals, and urbanized banks, it is possible that certain species of zooplancton can be affected by the luminous Pollution.

the Nanoplancton (20-2 µm) and the Picoplancton (2-0,2 µm), and Femtoplancton, or the virioplancton (marine viruses primarily) more recently discovered, constitute a share still badly known of the marine Biodiversité. These categories of size include many species which seem to be able to live with great depth where the luminous intensity is extremely low. Some of these species seem to have very slow rates/rhythms of reproduction as one exceptionally long lifespan (characteristic which one also finds at more complex organizations of the great depths, of which certain fish of deep seas).

The plankton indicating a the unit of different organizations, it is incorrect to say “a plankton”: one should specify about which organization (Taxon) one speaks.

Plankton and food chain

The plankton is the first link of the marine food chains. The Phytoplancton is eaten by the Zooplancton and a multitude of marine organizations. They will be the prey small predatory themselves driven out by the large predatory ones. Certain large animals like the Whale and the Basking shark nourish Zooplancton directly. In fresh water and more still in brackish water, the phytoplankton is one of the principal bases of the food chains.

In water particularly turbides, charged with sandy particles or vases in suspension, particular types of plankton appear, which colonize the suspended particles, allowing a biomass raised in spite of the fact that turbidity does not allow the penetration of the sun. This water is generally subjected to an agitation and or important currents which them oxygènent.
A particular case is that of the muddy Bouchon Estuaire S, which is driven at the rate/rhythm of the Marée S and the fresh water surges. It is used of nursery or protection and zone of nourrissage with alevins of certain species. It can also concentrate certain pollution. The " pluie" or " neige" what constitutes the corpses or excrements of let us zooplanctons which go down passively towards sea-beds has a great importance for the food of the species of deep seas and for the biogeochemical cycles.

Certain planktonique species can produce Toxine S powerful (of which botulinic), which can be concentrated in the Food chain by the shells, organizations filterers or certain fish. These same organizations also can and to in addition concentrate Toxique S modified and/or bioaccumulés by the plankton such methylated mercury, of which the quantity tends to increase regularly at predatory fish and Cétacé S, in a very alarming way for health of the human consumers and the marine ecosystems.

Under certain conditions (high contributions of nutrients, generally of the organic matters, nitrates or phosphates), a " excès" of plankton led to a situation of Eutrophication, even of Dystrophisation, i.e. of specific or durable death of the majority of the watery organizations. UNO identified a hundred dead zones (Dead zone) of which in the Baltic. In these zones, eutrophication can be combined with other types of Pollution or disturbance.

Plankton and nécromasse

The plankton is at the origin of a considerable biomass, but also of a Nécromasse which constitutes a big part of certain sediments (the chalk is nécromasse it fossil of marine plankton). The sedimentation of nécromasse planktonique is one of the planetary carbon well, but also one of the ways which allowed the detoxication of the oceans primitive too rich in certain salts, of calcium in particular, to allow a complex life on the models that we know.

Plankton and climate

The plankton intervenes in the cycle of carbon, via photosynthesis, but also while emitting after their death of the sulfur molecules which contribute to the nucleation of the water drops, i.e. to the formation of the clouds and the rains.
It should be noted that the planktonique biomass can be much more important in cool water, even under the icecap, that in tropical warm water, if they are distant from sources of oligoéléments such as the volcanic contributions of the coral atolls. The phenomena of Upwelling and endo-upwellings are at the origin of the distribution of the masses of planktons which condition the species of the higher trophic networks. The climatic modifications, by affecting the marine currents and the temperature of water (and thus its passive content oxygen) could modify the distribution and the nature of the masses of plankton and thus of the fishing resources. Important modifications are observed since nearly one century, but the share of the impacts of surpêche and pollution (nitrates, pesticides, heavy metals, turbidity, thermal pollution.) in these phenomena is still difficult to determine. The plankton would pump today approximately a third of CO2 anthropic, that is to say as much as all the terrestrial plants and the watery plants, the last third being that which is responsible for the increase in gases with greenhouse effect in the atmosphere.

Threats on the plankton?

According to Michael Behrenfeld published by the Natural newspaper (December 7th, 2006), the satellite imagery, which makes it possible for example to evaluate the quantity of chlorophyl in water, shows that approximately 60% seas of 1998 to 1999 had a level of planktonique activity very low, because of the phenomenon El Niño, before recovering with Niña then to fall regularly: from 1999 to 2005 (during 6 years). The planktonique activity strongly and regularly fell, the losing ocean - on average, and each year - a capacity for absorption of 190 million tons (MT) of carbon compared to the previous year. If this tendency were to be confirmed in the years to come, climate warming could be accelerated. They are indeed approximately 695 MT de CO2, that is to say more than the total of the annual emissions of France, which do not have - in 6 years - summer absorptive in the tropical and equatorial zones, following the retreat of the planktonique activity.

The warming is the possible cause most often quoted, because of the " stratification" water that it generates, which implies the least gone up nutritive salts for the plankton. The moving part of the plankton contributing itself to the formation of the clouds, and the mixture of the thermal layers and of different density, this cycle could car-discuss, the more so as the fish, which also contribute to the mixture of the surfacings are also less and less numerous, whereas the dead marine zones are in increase.

Scott Doney, also in the nature magazine, specifies that, in same time, the productivity increased with the high latitudes because of the warming of surface water, but without being able to make up the deficit of the tropical zone, productivity gain being limited and relating to a much lower volume of water. It is necessary to add this effect to those of the Acidification of the oceans, with those of their overexploitation whose impacts are badly included/understood, to those of the bleaching or of died of the corals, and to those of eutrophication and of the abnormal Turbidité of the Estuaire S and of vast marine zones. The marine plankton could be put at evil before 2050, even before 2030 in the Antarctic Ocean. At sea North, since 1961, the share of the warm water plankton does not cease growing compared to that of the cool water plankton.

Important regressions of phytoplankton seem to be already occurred, in particular approximately 55 million years ago, at one period precisely characterized by an increase in the gas rates with greenhouse effect (of unknown factors cause).

Sizes

The plankton is often classified according to its size, dependant on the type of filter used to collect it.

Megaplancton: 20-200 cm (ex: grosses jellyfish S, colonies of Salpe S)
Macroplancton: 2-20 cm
Mesoplancton: 0,2 mm2 cm (visible with the naked eye)
Microplancton: 20-200 μm (filter in fabric)
Nanoplancton: 2-20 μm (coffee filter)
Picoplancton: 0,2-2 μm (Bacterium S and eucaryotes)
Femtoplancton: <0,2 μm (primarily of the Virus)

The nanoplancton and the lower sizes were only discovered in the years 1980. The largest planktonique organization is the jellyfish Chrysaora. It measures 1 m diameter and 6 m length.

Anecdote

In 1952, a young doctor crossed the Atlantic while feeding exclusively from fish, plankton, sea water and rainwater. Alain Bombard wanted to prove that one can survive a long time on an inflatable dinghy of less than five meters with for only resources the products of the sea and the sky.

In the film green Sun , the plankton is the base of the alimentaion.

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