What is plankton and where does it live. Plankton is something light, floating freely in the water? Did you like the material? subscribe to our email newsletter

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, among passive swimmers there are also quite large objects- huge seaweeds, giant jellyfish and even some fish, for example, a moon fish, whose weight reaches two tons, but which at the same time prefers not to move, applying muscle effort, but to soar in the 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.

Plankton consists of organisms that live freely in the water column and are not able to counteract their own movements. aquatic environment(currents, convection currents, etc.) due to the absence or relatively underdevelopment they have organs of motion. Systematically, plankton is divided into plant plankton, or phytoplankton, and animal plankton, or zooplankton.

The composition of plankton includes, on the one hand, holoplanktic organisms, which spend their entire life, including also the period of development, out of contact with a solid substrate, and on the other hand, meroplanktic organisms that spend a certain period of their lives at the bottom of reservoirs. The latter include, for example, planktic larvae of worms, echinoderms, mollusks, crustaceans and other marine bottom animals, hydroid jellyfish budding from polyps, as well as many organisms living in the coastal region, cysts and resting eggs of which for further development sink to the bottom.

Depending on the size of organisms, plankton is divided into the following groups.

1. Ultraplankton (bacteria) - the size of organisms does not exceed a few microns, the lower limit is beyond visibility.

2. Nannoplankton, or dwarf plankton (the smallest lower plants and protozoa), - the size of organisms is measured in microns and tens of microns; due to their negligible size, nannoplankton organisms pass through the thickest silk gas, can only be studied using centrifugation or chamber method, therefore this group of organisms is also called centrifugal or chamber plankton.

3. Microplankton ( main part phytoplankton, as well as ciliates, rotifers, small crustaceans, etc.) - the size of organisms is measured in tenths and hundredths of a millimeter; It is caught by planktic nets of thick silken gas or by sedimentation, therefore it is also called net, or sedimentary, plankton.

4. Mesoplancon ( major representatives phytoplankton, the main part of the zooplankton of the seas) - the size of organisms is measured in millimeters; caught by planktic nets of rare silken gas - net plankton.

5. Macroplankton ( higher crayfish, jellyfish, pelagic worms, etc.) - the size of organisms is measured in centimeters, found exclusively in the seas; caught in large planktic nets.

6. Megaloplankton (many scyphoid jellyfish, large siphonophores, etc.) - the size of organisms is measured in tens of centimeters; found exclusively in the seas.

A distinctive feature of planktic organisms - their ability to be suspended in water - leaves a certain imprint on their structure.

I most often heard about plankton in programs about nature. Whales feed on plankton, plankton swims in the water... Naturally, I was more interested in the whales themselves.

Plankton itself interested me after one of the episodes of the old animated series "Magic School Bus". The heroes shrank down and in the magic bus studied all sorts of interesting places. The depths of the ocean too. Here in this series, plankton was shown closer and it turned out that it was not so boring after all.

Plankton: what is it and why

If you think about it, being called plankton is pretty insulting.

Plankton- This common name for many small organisms. Like vegetable ( phytoplankton) and animals ( zooplankton).

Individually, they are of little interest to anyone, but together they form an impressive size. biomass who plays essential role in an ecosystem, mainly because it is the most important link in food chain.

Remove the plankton and the whole ecosystem will fall apart.

Plankton lives in both fresh and salt water.

Plankton include:

• protozoa;
• seaweed;
• shellfish;
• crustaceans;
• fish eggs and larvae.

The fate of plankton is unenviable: it passively goes with the flow, becoming someone's dinner along the way.

More often plankton composition very diverse, but there are exceptions. small crustaceans brine shrimp live in waters so salty that they are often their only inhabitants.

For lovers of visual experiments, I can suggest going to a pet store and buying a kit for growing these crustaceans. Newborn brine shrimp (they are called nauplii) look like a cluster of reddish dots, but under microscope they can be seen better. Their fate, like that of any plankton, is sad - they are bred to feed small aquarium fish and fry.

Who eats plankton

Yes, everything, to be honest. Even Bigger plankton eats smaller plankton. Also, various types of plankton become excellent food for fish.

aquarium fish By the way, they also eat plankton with great pleasure.

Or the whales. How can such huge animals eat such a trifle as plankton? Very simple. Baleen whales have lobes in their mouths that serve as a sieve to separate water and plankton. These records are known as "whalebone".

Incredible, but in a completely ordinary grocery store you can meet the plankton yourself. It will be called "krill".

Krill- these are rather large (by the standards of plankton) crustaceans. Delicious stuff, let me tell you.

Plankton

Plankton is made up of a wide variety of organisms. Some of them are larval forms of benthic species, in others the life cycle takes place entirely in the water column, away from a solid substrate. Part of the plankton is represented unicellular algae capable of photosynthesis, i.e. converting carbon dioxide and water into simple sugars and free oxygen. Because photosynthesis requires light, most of these organisms are found in top layer water.

Planktonic algae belong to several large taxonomic groups, the main of which are diatoms (diatoms) and dinoflagellates. The cells of the first are covered with a silica shell. In some places, there are so many diatoms that their dead remains, settling to the bottom, form special diatom silts, which over millions of years have turned into thick layers of rock - diatomite.

Phytoplankton

Diatoms, dinoflagellates and other planktonic algae together make up phytoplankton. Like other organisms capable of converting inorganic substances into organic, i.e. in their own food, they are called autotrophs, which means "self-feeding" in Greek. Together with other autotrophs, such as land plants, they combine to form environmental group producers, since they are the first link in various food chains.

Algal bloom. In many seas, especially in temperate climate zone, in certain seasons, usually in winter, the water is enriched with mineral salts necessary for the reproduction of phytoplankton. When the water warms up in spring, microscopic algae begin to rapidly divide, explosively increasing their numbers, and the sea becomes cloudy, and sometimes even turns into an unusual color. This phenomenon is called an algal bloom. Usually, it declines and stops as the reserves of the necessary salts are depleted: phytoplankton organisms in the mass die and are eaten by zooplankton until a temporary population equilibrium is established again.

Red tides. Usually, algal blooms are accompanied by an increase in the number of zooplankton, which, feeding on phytoplankton, restrains to a certain extent the growth of its mass. However, at times it increases so rapidly that the process gets out of control. This is especially often observed during the rapid reproduction of one of the species of dinoflagellates. Sea water near the coast, it takes on the color and texture of tomato soup - hence the name "red tide". The main thing is that the "blooming" algae contains a toxin that is dangerous for many fish and shellfish. Red tides in Florida, Africa and other regions led to the death of many hundreds of thousands of these animals.

Shellfish poisoning. Some types of phytoplankton contain nerve poison. bivalves, in particular mussels, feed on phytoplankton, therefore, in certain seasons, usually in the warm months, they also eat huge amounts of “blooming” toxic algae, accumulating their poison in their tissues without visible harm to themselves. However, eating such shellfish can cause severe poisoning.

Productivity. Phytoplankton actively breeds mainly in coastal waters, and the farther from the coast, the lower its productivity. That is why in the open ocean, especially in the tropics, the water is very clear and blue, and off the coast, especially in temperate zone, often yellowish, greenish or brown.

A sharp increase in the concentration of mineral salts dissolved in water, necessary for the development of phytoplankton, is associated with currents that raise these substances from the bottom layers or carry them out of estuaries, where many remains of dead organisms mineralized by bacteria accumulate. In some parts of the ocean there are so-called. rises of water, or upwellings, are peculiar currents carrying cold water rich in nutrients (biogenic) elements ocean water from great depths to shallow coastal waters. Upwelling zones are associated with high productivity of phyto- and zooplankton, therefore they attract a large number of fish.

Zooplankton

The continuously dividing planktonic algae are eaten with no less intensity by zooplankton, which maintains their numbers at an approximately constant level. Planktonic animals include mainly tiny crustaceans, jellyfish and the larvae of thousands of other marine animal species. Most taxonomic types of invertebrates are represented in zooplankton.

Bioindicators. Like benthic animals, zooplankton forms can exist only at certain levels of temperature, salinity, illumination, and water velocity. The requirements of some of them to environmental conditions are so specific that the presence of these organisms can be used to judge the features marine environment generally. Such organisms are commonly referred to as bioindicators.

Although most zooplanktonic forms are able to move actively to some extent, in general these animals drift passively with the current. However, many of them make daily vertical migrations, sometimes over distances of up to several hundred meters, in response to diurnal changes in illumination. Some species are adapted to life in the near-surface layer, where the illumination changes cyclically, while others prefer the more or less constant twilight that is found in daytime at great depths.

Deep-water scattering layer. Many planktonic animals form dense aggregations at medium depths. Such accumulations were first detected by instruments for measuring depth - echo sounders: the sound waves sent by them, obviously not reaching the bottom, were scattered by some kind of obstacle. Hence the term arose - deep-water scattering layer (DSL). Its presence indicates that large numbers of organisms can live far from phytoplankton producers.

Zooplankton, following phytoplankton, concentrates in nutrient-rich coastal upwelling zones. The increased abundance of marine animals here is undoubtedly a consequence of active breeding algae.

Nekton

Nekton - a group of actively swimming organisms that can resist the force of the current and move considerable distances. N. includes fish, squid, cetaceans, pinnipeds, water snakes, turtles, penguins. Nektonic animals are characterized by a streamlined body shape and well-developed organs of movement. N. is opposed to plankton; An intermediate position between them is occupied by micronekton, represented by animals capable of limited active movements: juveniles and small species of fish and squid, large shrimps, euphausian crustaceans, etc.

Representatives of the nekton group live in the water column and are able to move regardless of the current. These include the water mite. In general, all water mites are distinguished by a beautiful, often variegated or bright color. The body of water mites is shortened, not segmented, the head, chest and abdomen are fused together. At the marginal edge of the head end, eyes arranged in pairs are placed, enclosed in chitinous capsules. The legs of water mites are swimming, covered with numerous hairs.

Zooplankton (animal plankton) are small organisms that are often at the mercy of ocean currents, but, unlike phytoplankton, are not capable of.

Peculiarities

The term zooplankton is not a taxonomic term, but characterizes the way of life of some animals that move due to the flow of water. Zooplankton are either too small to resist the current, or large (as is the case for many jellyfish) but lack the organs to swim freely. In addition, there are organisms that are plankton only at a certain stage of their development. life cycle.

The word plankton comes from the Greek word planktos meaning "wandering" or "wandering". The word zooplankton includes Greek word zoion meaning "animal".

Types of zooplankton

It is believed that there are over 30,000 species of zooplankton. It can live in fresh or salt water all over the world, including oceans, seas, rivers, lakes, etc.

Types of zooplankton

Zooplankton can be classified by size or body length. Some terms that are used for zooplankton include:

• Microplankton - organisms 20-200 µm in size - this includes some copepods and other zooplankton.
• Mesoplankton - organisms 200 µm-2 mm in size, including crustacean larvae.
• Macroplankton - organisms 2-20 mm in size, which include euphausians (for example, krill - important source food for many organisms, including baleen whales).
• Micronekton - organisms 20-200 mm in size. Examples include some euphausians and cephalopods.
• Megaplankton - planktonic organisms larger than 200 mm, including salps.
• Holoplankton - Organisms that are planktonic throughout their lives - such as copepods.
• Meroplankton - organisms that have a planktonic life cycle stage, but grow out of it at some point, for example, fish and.

What do zooplankton eat?

Zooplankton and food chains

Zooplankton are usually found in the second trophic level, which starts with phytoplankton. In turn, phytoplankton are eaten by zooplankton, which are eaten by small fish and even giant whales.