Plankton - what kind of natural phenomenon is this? This is not the name of individual creatures, but a group of hydrobiont organisms drifting in the water column. In the traditional classification, all the inhabitants of the oceans, rivers and lakes of land are divided into three groups: nekton, benthos and plankton. The first are fish, squid, amphibians and other animals that actively move. An attached lifestyle is led by benthos (sponges, worms, mollusks, and others).

Plankton - what is it?

Translated from Greek name passively moving organisms in the water means "wandering", "soaring". Plankton are living creatures that do not have active means of movement or use them to a limited extent. By belonging to plankton in the sea and fresh water bodies, it is divided into 3 main types: bacterial, phyto- and zooplankton. These organisms inhabit all water bodies: from large fresh and marine to small puddles.

Representatives of phytoplankton - algae and cyanobacteria themselves produce organic substances. They need light to support photosynthesis. Zooplankton are protozoa, crustaceans, coelenterates, eggs, larvae that feed on other small organisms.

There is another classification that does not take into account the method of nutrition, but the size of the organisms. According to this system, groups are distinguished, starting with nannoplankton (viruses) and ending with megaplankton. The most common on the planet are the smallest creatures (about 2 microns). The existence of this group became known only in the 1980s. Megaplankton includes jellyfish, cephalopods, ctenophores and others. aquatic life, whose body is more than 2 cm in length.

Why doesn't plankton drown?

The body density of some organisms in the World Ocean is close in value to the specific gravity of water. Plankton are something very light, floating freely in their habitat. Those living beings, whose body density is greater than one, are kept in a suspended state by their own motor activity.

We list the structural features of plankton that allow them to exist in the surface layer of water:

  • microscopic or small sizes;
  • flat body shape;
  • tissue saturation with water (up to 98%);
  • secretion of abundant mucus on the surface of the body;
  • gas vacuoles;
  • fatty inclusions;
  • outgrowths, needles, hairs, bristles on the surface of the body;
  • a small amount in the tissues of heavy chemical elements.

Each species does not have all, but 2-3 devices from the list. There is another feature that allows unicellular algae not to drown - association in colonies. An amazing ability of some hovering organisms is the change in density depending on the temperature of the water. In a cold environment specific gravity body increases, and in warm - decreases, which prevents immersion.

Phyto- and bacterioplankton

The group of organisms, which makes up about 90% of the total, includes green marine plankton and inhabitants. These are volvox, dinophytes, euglenoids, cryptophytes, cyanides, green bacteria. They contain the pigment chlorophyll in their bodies. land plants. Phytoplankton absorb carbon dioxide dissolved in water, use photosynthesis to produce nutrients. Some representatives can fix nitrogen, hydrogen sulfide.

Favorable conditions for the growth and reproduction of phytoplankton:

  • water rich in carbon dioxide;
  • sunlight;
  • the presence of mineral elements;
  • moderate temperature and salinity of water;
  • slight depth.

Sometimes there is a sharp increase in phytoplankton or "bloom" of water. In the ocean, a similar phenomenon is observed over a vast area covering hundreds of square kilometers. Big environmental problem is the "bloom" of fresh water consumed for household and drinking purposes. Some representatives of phytoplankton emit toxins that are dangerous for fish and humans.

Zooplankton

Animal plankton - what is it? An important component of any aquatic ecosystem. Without this group of organisms, many inhabitants of the oceans, seas, rivers and lakes would not receive the necessary nutrition. Some representatives of zooplankton have organs of movement, not using them to move long distances. Outgrowths, bristles, needles, tentacles are needed by such organisms for swimming in the adjacent volume of water and vertically.

Wide distribution horizontally is provided by the movement "by the will of the waves" and currents. Thus, larvae of crustaceans, echinoderms, and fish eggs are present in plankton for less than two months. During this period of time, they are carried hundreds of kilometers away from their original habitat. Zooplankton contains the larval stages of sponges, sea anemones, worms, mollusks, crabs, lobsters and starfish. Numerous representatives of the group are crustaceans and krill, whose life almost entirely depends on the availability of food - diatoms.

Who eats plankton?

In the food chain, each organism is important; without it, the whole cannot exist. Small and bacteria are involved in photosynthesis, are producers of organic substances. Animal forms of organisms drifting in the water are the main consumers of the smallest algae and bacteria. Zooplankton serve as a link between bacteria, algae and large inhabitants reservoirs.

Tiny crustaceans, krill and pteropods feed on many fish, shellfish, some birds, and even the decline in plankton numbers threatens the well-being of the entire ecosystem of the oceans. Scientists are studying this problem in connection with climate changes on the planet that affect the temperature, salinity and transparency of water - the habitat of plankton.

plankton

Dictionary of medical terms

plankton (Greek planktos wandering)

a set of animal and plant organisms inhabiting the water column and passively carried by the current; characterizes the pollution of the reservoir.

Explanatory dictionary of the Russian language. D.N. Ushakov

plankton

plankton, m. (from the Greek plagktos - wandering) (biol.). Plant and animal organisms that live in the seas and rivers and move only by the force of the flow of water. plant plankton. Animal plankton. The Papaninites discovered plankton at the northernmost latitudes near the pole.

Explanatory dictionary of the Russian language. S.I. Ozhegov, N.Yu. Shvedova.

plankton

A, m. (special). The totality of animal and plant organisms that live in the water column and are carried by the force of the current.

adj. planktonic, th, th.

New explanatory and derivational dictionary of the Russian language, T. F. Efremova.

plankton

m. The accumulation of the smallest plant and animal organisms living in the seas, rivers, lakes and moving almost exclusively by the force of the flow of water.

Encyclopedic Dictionary, 1998

plankton

PLANKTON (from the Greek. planktos - wandering) a set of organisms that live in the water column and are unable to resist the transfer by the current. Plankton is made up of many bacteria, diatoms and some other algae (phytoplankton), protozoa, some coelenterates, molluscs, crustaceans, tunicates, fish eggs and larvae, and larvae of many invertebrate animals (zooplankton). Plankton directly or through the intermediate links of food chains serves as food for all other animals living in water bodies. See also Pelagic organisms.

Plankton

(from the Greek planktós ≈ wandering), a set of organisms that inhabit the water column of continental and marine reservoirs and are not able to resist the transfer by currents. P.'s composition includes both plants - phytoplankton (including bacterioplankton) and animals - zooplankton. P. is contrasted with the population of the bottom - benthos and actively swimming animals - nekton. Unlike the latter, P.'s organisms are not capable of independent movement or their mobility is limited. IN fresh waters A distinction is made between the lake plankton, which is limnoplankton, and the river plankton, which is potamoplankton.

Plant photosynthetic planktonic organisms need sunshine and inhabit surface water, mainly to a depth of 50≈100 m. Bacteria and zooplankton inhabit the entire water column to the maximum depths. Marine phytoplankton consists mainly of diatoms, peridine and coccolithophorids; in fresh waters - from diatoms, blue-green and some groups of green algae. In freshwater zooplankton, copepods and cladocerans and rotifers are the most numerous; in the marine ≈ crustaceans dominate (mainly copepods, as well as mysids, euphausians, shrimps, etc.), protozoans (radiolaria, foraminifera, ciliates tintinnida), intestinal cavities (jellyfish, siphonophores, ctenophores), winged mollusks, tunicates (appendicularians, salps , kegs, pyrosomes), eggs and larvae of fish, larvae of various invertebrates, including many benthic. The species diversity of P. is greatest in the tropical waters of the ocean.

The sizes of P. organisms vary from a few microns to several meters. Therefore, they usually distinguish between: nannoplankton (bacteria, the smallest unicellular algae), microplankton (most algae, protozoa, rotifers, many larvae), mesoplankton (copepods and cladocerans, and other animals less 1 cm), macroplankton (many mysids, shrimp, jellyfish, and other relatively large animals) and megaloplankton, which include a few of the largest planktonic animals (for example, the comb jelly venus belt up to 1.5 m long, the cyanide jellyfish with a diameter of up to 2 m with tentacles up to 30 m, colonies of pyrosomes up to 30 m long and more than 1 m in diameter, etc.). However, the boundaries of these size groups are not generally accepted. Many P. organisms have developed devices that facilitate soaring in water: reducing the specific mass of the body (gas and fat inclusions, water saturation and gelatinization of tissues, thinning and porosity of the skeleton) and increasing its specific surface area (complex, often highly branched outgrowths, flattened body) .

Phytoplankton organisms are the main producers of organic matter in water bodies, due to which most aquatic animals live. In shallow coastal waters organic matter it is also produced by benthic plants - phytobenthos. The abundance of phytoplankton in various parts water bodies depends on the amount of nutrients necessary for it in the surface layers. Limiting in this respect mainly phosphates, nitrogen compounds, and for some organisms (diatoms, siliceous) and silicon compounds. Behind long history ocean, these substances accumulated in large quantities in its depths, mainly as a result of the decomposition and mineralization of organic particles settling from the upper layers. Therefore, the abundant development of phytoplankton occurs in areas of deep water rise (for example, in the area of ​​the junction warm waters Gulf Stream and northern cold currents, in the zone of equatorial divergence of waters, in areas of negative winds near the coast, etc.). Since small plankton animals feed on phytoplankton, serving as food for larger ones, the areas of the greatest development of phytoplankton are also characterized by an abundance of zooplankton and nekton. Much less and only local importance in the enrichment of surface waters with nutrients is the river runoff. The development of phytoplankton also depends on the intensity of illumination, which in cold and temperate waters causes seasonality in the development of P. In winter, despite the abundance of nutrients carried into the surface layers as a result of winter mixing of waters, phytoplankton is scarce due to lack of light. Spring begins fast development phyto-, and after him, zooplankton. As phytoplankton use nutrients, and also as a result of eating them by animals, the amount of phytoplankton decreases again. In the tropics, the composition and quantity of P. are more or less constant throughout the year. The abundant development of phytoplankton leads to the so-called. flowering of water, changing its color and reducing transparency. When some peridinas bloom, toxic substances are released into the water, which can cause mass death planktonic and nektonic animals.

The biomass of P. varies in different water bodies and their regions, as well as in different seasons. In the surface layer of the ocean, the biomass of phytoplankton usually varies from a few mg to several g/m3, zooplankton (mesoplankton) ≈ from tens of mg to 1 g/m3 or more. With depth P. becomes less various and its quantity quickly decreases. In the World Ocean, poor marine areas predominate in area over rich ones. The poorest regions of P. are the central tropical regions on both sides of the equatorial zone; the richest are the coastal regions of temperate and subtropical latitudes. The annual production of phytoplankton in the World Ocean is 550 billion tons (according to the Soviet oceanologist V. G. Bogorov), which is almost 10 times higher than the total production of the entire animal population of the ocean.

Many planktonic animals make regular vertical migrations with an amplitude of hundreds of meters, sometimes more than 1 km, which contribute to the transfer of food resources from the surface layers rich in them to the depths and to provide food for deep-sea P. Due to the ability to migrate, the vertical zonality of P. is less pronounced than that of benthos ( see Marine fauna). Many planktonic organisms have the ability to glow (bioluminescence). Some can serve as indicators of the degree of pollution of the reservoir, tk. are sensitive to pollution to varying degrees.

P. directly or through intermediate links in food chains serves as a source of nutrition for many game animals: squid, fish, whales, etc. Of the planktonic organisms, some crustaceans (shrimps, mysids) serve as objects of fishing. IN last years All greater value acquires the fishery of Antarctic crustaceans - euphausiids (krill), sometimes forming huge aggregations (up to 15 kg / m3). The development of methods for using and catching marine P. is promising, because. its reserves are many times greater than the reserves of all marine organisms that have been harvested so far.

Lit .: Zenkevich L. A., Fauna and biological productivity of the sea, vol. 1≈2, M., 1947≈51; Life of fresh waters of the USSR, vol. 1≈3, M.≈ L., 1940≈50; Bogorov V. G., Ocean productivity, in the book: Basic problems of oceanology, M., 1968; Biology of the Pacific Ocean. Plankton, M., 1967 ( Pacific Ocean, v. 7, book. 1); Vinogradov M. E., Vertical distribution of oceanic zooplankton, M., 1968; Beklemishev K.V., Ecology and biogeography of the pelagial, M., 1969; Kiselev I. A., Plankton of the seas and continental reservoirs, vol. 1, L., 1969.

G. M. Belyaev.

Wikipedia

Plankton

(Hyperia macrocephala)

Plankton (disambiguation)

  • Plankton- heterogeneous, mostly small organisms, freely drifting in the water column and not able to resist the flow.
  • Office plankton is a modern slang expression used to refer to "white-collar" - small office workers.
  • Sheldon Plankton is a character from the animated series SpongeBob SquarePants.

Examples of the use of the word plankton in the literature.

I went to Buenaventura and got a job on a ship, a Chinese assembler plankton.

Buildings of corals and calcareous algae, continuous films for thousands of kilometers plankton ocean, Sargasso Sea, taiga of Western Siberia or Hylaea tropical Africa provide such examples.

And the tunas themselves were chasing cephalopods, and the cephalopods were chasing a flock of silvery sardines, which in turn set their sights on microscopic organisms of the ocean plankton.

There, one above the other, giant Medusa hang and deadly goads penetrate the water to the very bottom - the smallest plankton won't seep through the wall.

Although, by the way, I myself am not averse to sipping some plankton otherwise, yesterday, under the guise of a delicacy, mossy nostrils of an elk were sold to us and forced to fill it all with strawberry liqueur.

And I slowly passed through the quivering thin film from a sunny oceanic noon to a light green, heavily infused with plankton, heated near-surface layer.

It is divided into two main groups: the zoo plankton, consisting of animal microorganisms and fish eggs, and on phyto plankton, or vegetable plankton made up of tiny algae.

We both in the Indian and in the Atlantic did sample analyzes plankton, and it turned out that the ascorbic acid in it - the cat cried.

But Valery nevertheless spoke: - Once I was preparing an article by a foreigner that a blooming plankton kills animals.

You just had to soak it up like a fish plankton and then don't let it leak again.

We were going to do this with the help of a device that hydrobiologists usually used to collect plankton.

During the last expedition, hydrobiologists gave us a whole mug plankton presented.

How not to tune in philosophically when plankton and the stars are the same, and the world is the same as it was long before the human eye saw it, and billions of busy fingers began to transform it.

To determine the nature and extent of the damage caused fisheries as a result of pollution of the reservoir, to establish the causes and circumstances of the death of fish and plankton, determining the prospects for the restoration of food organisms in the reservoir, an ichthyological examination is assigned.

Sometimes, throwing a large piece of cloth overboard and dragging it behind the ship, they managed to catch a little plankton, but eating it is like chewing coarse sand, bitter and unpleasant in taste.

Eggs and larvae of fish, larvae of various invertebrates (zooplankton). Plankton, directly or through intermediate links in the food chain, is food for most other aquatic animals.

The term plankton was first coined by the German oceanographer Victor Hensen in the late 1880s.

Classification

Depending on the way of life, plankton is divided into:

  • holoplankton - all life cycle spends in the form of plankton;
  • meroplankton - existing in the form of plankton only part of life, for example, sea ​​worms, fish.

Plankton is made up of many bacteria, diatoms and some other algae (phytoplankton), protozoa, some coelenterates, molluscs, crustaceans, tunicates, fish eggs and larvae, and larvae of many invertebrate animals (zooplankton). Plankton directly or through intermediate links of food chains serves as food for other animals living in water bodies (except for phytoplankton, benthic macrophytes and microalgae can also be the first link in food chains). Plankton is a mass of plants and animals, most of which are microscopic in size. Many of them are capable of independent active movement, but they do not swim well enough to resist currents, so planktonic organisms move along with water masses. Planktonic organisms are found at any depth, but near-surface, well-lit water layers are richest in them, where they form floating "forage grounds" for larger animals. Plant photosynthetic planktonic organisms need sunlight and inhabit surface waters, mainly to a depth of 50-100 m - the so-called euphotic layer. Bacteria and zooplankton inhabit the entire water column to the maximum depths. Marine phytoplankton consists mainly of diatoms, peridine and coccolithophorids; in fresh waters - from diatoms, blue-green and some groups of green algae. In freshwater zooplankton, copepods and cladocerans and rotifers are the most numerous; in the marine crustaceans dominate (mainly copepods, as well as mysids, euphausiae, shrimp, etc.), protozoa are numerous (radiolaria, foraminifera, ciliates tintinnida), intestinal cavities (jellyfish, siphonophores, ctenophores), winged molluscs, tunicates (appendicularians, salps, kegs, pyrosomes), fish eggs, larvae of various invertebrates, including many benthic. The species diversity of plankton is greatest in the tropical waters of the ocean.

There are several classifications of plankton depending on their size. The most common is the following:

  • megaplankton (0.2 - 2 m) - jellyfish
  • macroplankton (0.02 - 0.20 m) - many mysids, shrimps, jellyfish and other relatively large animals
  • mesoplankton (0.0002 - 0.02 m) - copepods and cladocerans and other animals less than 2 cm
  • microplankton (20 - 200 microns) - most algae, protozoa, rotifers, many larvae
  • nanoplankton (2 - 20 microns) - small unicellular algae, some large bacteria
  • picoplankton (0.2-2 microns) - bacteria, the smallest unicellular algae.
  • femtoplankton (<0,2 мкм) - океанические вирусы.

According to modern data, picoplankton provides the largest production in ocean waters. Eukaryotic algae recently discovered in its composition (for example, prasinophyte genera Osteococcus) are the smallest eukaryotes.

Zooplankton is the most numerous group of aquatic organisms of great ecological and economic importance. It consumes organic matter formed in water bodies and brought from outside, is responsible for the self-purification of water bodies and watercourses, forms the basis of nutrition for most fish species, and finally, plankton serves as an excellent indicator for assessing water quality.

Studies of zooplankton organisms help determine the pollution of water bodies and determine the ecological features of a particular area. Any aquatic ecosystem, being in balance with environmental factors, has a complex system of mobile biological connections that are disturbed under the influence of anthropogenic factors. First of all, the influence of anthropogenic factors, and pollution in particular, affects the species composition of aquatic communities and the ratio of the abundance of their constituent species.

see also


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Synonyms:
  • Nifak
  • american bantam

See what "Plankton" is in other dictionaries:

    PLANKTON- (from the Greek planktos wandering), a set of organisms that inhabit the water column of continental and sea. bodies of water and not able to withstand the transfer of currents. P.'s composition includes phyto, bacterio, and zooplankton. In fresh waters, lake P ... Biological encyclopedic dictionary

    PLANKTON- PLANKTON, plankton, husband. (from Greek plagktos wandering) (biol.). Plant and animal organisms that live in the seas and rivers and move only by the force of the flow of water. plant plankton. Animal plankton. Papaninites discovered plankton on ... ... Dictionary Ushakov

    PLANKTON- Pelagic animal and plant population of any marine or freshwater. basin, considered together as a biologically integral phenomenon, opposed to the population of the bottom. Dictionary of foreign words included in the Russian language. ... ... Dictionary of foreign words of the Russian language

    Plankton- (from Greek planktós wandering) - a set of organisms of plant and animal origin that live in the water column and are not able to resist the flow. Such organisms can be bacteria, diatoms and some others ... ... Oil and gas microencyclopedia

    PLANKTON- (from the Greek planktos wandering) a set of organisms that live in the water column and are unable to resist the transfer by the current. Plankton is made up of many bacteria, diatoms and some other algae (phytoplankton), protozoa, some ... ... Big encyclopedic Dictionary

    plankton- a, m. plancton m. gr. plankton wandering. An accumulation of small plant and animal organisms living in the seas, rivers, lakes and moving almost exclusively by the force of the flow of water. ALS 1. Plankton reproduces especially rapidly those ... ... Historical Dictionary of Gallicisms of the Russian Language

    PLANKTON- PLANKTON, a term originally introduced by Hensen (Hensen, 1887) to refer to the living population of the waters of the seas. Currently, plankton is called a set of organisms that inhabit the water of any reservoir and conduct the entire biological cycle ... ... Big Medical Encyclopedia

    plankton- A community of organisms consisting of plants and animals suspended in the water column and drifting with its currents. [GOST 30813 2002] plankton Small organisms that move passively in water by waves and currents and do not have the ability to actively ... ... Technical Translator's Handbook

    PLANKTON- PLANKTON, a set of organisms that live in the water column and are unable to withstand the transfer of currents. As a rule, these are very small or microscopic organisms. There are two main types: PHYTOPLANKTON, which includes drifting ... ... Scientific and technical encyclopedic dictionary

    PLANKTON- PLANKTON, ah, husband. (specialist.). The totality of animal and plant organisms that live in the water column and are carried by the force of the current. | adj. plankton, oh, oh. Explanatory dictionary of Ozhegov. S.I. Ozhegov, N.Yu. Shvedova. 1949 1992 ... Explanatory dictionary of Ozhegov

The word "plankton" comes from the Greek planktos which means " wandering". This is not accidental - plankton really cannot resist the action of the current, unlike its closest "colleague" - nekton. However, one should not speak of plankton as a static mass of microscopic organisms. Although plankton is mostly composed of tiny crustaceans, diatoms, fish and plant larvae, it also contains quite large representatives, such as small jellyfish. Some life forms can move hundreds of meters vertically during the day. This phenomenon is called diurnal vertical migration».

Plankton is divided into several groups:

  1. Phytoplankton. The word comes from the Greek phyton, which translates as " plant". It consists of small algae floating at the very surface of the water, where there is a lot of sunlight necessary for photosynthesis.
  2. Zooplankton. From zoo- animal. Consists of protozoa and multicellular animals such as crustaceans. Zooplankton feed on phytoplankton.
  3. bacterioplankton. Consists of bacteria and archaea that are involved in the process of remineralization, i.e. transformation of organic forms into inorganic.

Thus, this classification divides all plankton into three large groups: producers (phytoplankton), consumers (zooplankton) and utilizers (bacterioplankton).

There is another classification that divides plankton according to the size of animal forms, starting with viruses ( nannoplankton) and ending megaplankton consisting of large (more than 2 cm) jellyfish, cephalopods, ctenophores, etc. The most common on our planet is nannoplankton, consisting of animals smaller than 2 microns. The discovery of the existence of this species of plankton occurred quite recently, in the 1980s.


Plankton is distributed throughout the world's oceans. The main condition for its formation is a sufficient amount of sunlight and the presence of organic nutrients in the water - nitrates and phosphates. And often the determining factor is the second. So, in tropical and subtropical waters, there is quite a lot of light throughout the year, but a small amount of organic compounds causes a low content of plankton in the water.

The importance of plankton in the world's oceans cannot be overestimated. It plays the role of a feeder for most fish at a young age. Currents collect plankton in the so-called feeding grounds, where cetaceans graze, as well as whale sharks. Some whales even make seasonal migrations following plankton fields.

Small plants on the surface of the water are involved in photosynthesis, and are an important element of the entire oxygen cycle system on the planet. The volume of phytoplankton in the world's oceans is enormous, so you should not write it off, assuming that only terrestrial plants emit oxygen. Plankton is also the largest source of carbon on Earth. The fact is that using it as food, animals convert plankton into a biological mass, which then settles on the seabed, because. heavier than water. This process is known in scientific circles as " biological pump».

The importance of studying plankton is emphasized by the fact that science has even singled out a separate section in biology that deals with its study - planktonology.

Plankton, which means “wandering” in Greek, is a collection of marine organisms that swim in the waters and are not able to resist currents. Most of the members of this collection are very tiny plants - diatoms and some other types of algae, bacteria, protozoa, crustaceans, coelenterates and mollusks, eggs and fish larvae, invertebrate larvae. However, quite large objects are also found among passively swimming ones - huge seaweeds, giant jellyfish and even some fish, for example, a moon fish, whose weight reaches two tons, but which prefers not to move, applying muscle effort, but to soar in water column or on the surface. Previously, such large representatives of flora and fauna were classified as a separate category - macroplankton.

Plankton is of great importance for marine life, as it serves as food for most animal species, directly or through links in the food chain.

Classification

There are several classifications of organisms that make up plankton. Scientists divide its inhabitants depending on the species. So, there are zooplankton and ichthyoplankton. Phytoplankton refers to that part of free-swimming organisms that is capable of photosynthesis. These are diatoms, dinoflagellates and other unicellular algae, as well as cyanobacteria. It is the excessive reproduction of phytoplankton that causes the phenomenon of water bloom.

Zooplankton is a collection of animals unable to resist the current. This includes heterotrophic protists, small crustaceans. The main part of the diet of zooplankton is phytoplankton, as well as their smaller counterparts. There is a special kind of zooplankton - ichthyoplankton. It includes eggs and larvae of fish, as well as the fish themselves, swimming exclusively at the behest of the current.

Plankton are divided into holoplankton and meroplankton based on their lifestyle. Members of the first class spend their entire lives soaring through the waters. Meroplankton includes those organisms for which such an image is only an intermediate stage. These are the larvae and eggs of fish and multicellular invertebrates, as well as representatives of some algae. As they grow, the meroplankton either settles to the bottom and begins to lead a benthic lifestyle, or starts active swimming.