What is plankton

plankton under the microscope

Living beings eat by following a food chain that is based on different levels in which organisms are the ones that eat and others are the ones that are eaten. The base of the link in the marine food chain is plankton. Many people don't know what is plankton nor its importance. It is the beginning of the food chain and is made up of very small organisms capable of photosynthesis. Its main function is to serve as food for many marine living beings. Therefore, it is of great importance for the development of ecosystems and marine life.

In this article we are going to tell you what plankton is, its importance and its characteristics.

What is plankton

microscopic plankton

Plankton is a group of creatures that float in the movement of ocean currents. The word plankton means wanderer or vagabond. This group of creatures is very diverse, diverse and has habitats for both fresh water and sea water. In some places, they can reach concentrations of up to billions of people and increase in colder oceans. In some static systems, such as lakes, ponds or containers with still water, we can also find plankton.

Depending on your diet and type of form, there are different types of plankton. We will divide between them:

  • Phytoplankton: It is a plant plankton whose activities are very similar to those of plants because they obtain energy and organic matter through photosynthesis. It can live in the layer of water that transmits light, that is, in the part of the sea or water where it receives direct sunlight. It can exist at a depth of about 200 meters, where the amount of sunlight is less and less. This phytoplankton is composed mainly of cyanobacteria, diatoms, and dinoflagellates.
  • Zooplankton: it is a zooplankton that feeds on phytoplankton and other organisms of the same group. It is mainly made up of crustaceans, jellyfish, fish larvae, and other smaller creatures. These creatures can be distinguished according to the time of life. There are some organisms that are part of plankton throughout its life cycle and are called holoplanktons. On the other hand, those that are only part of zooplankton during a period of time in their life (usually when it is their larval stage) are known by the name of meroplankton.
  • Plankton bacteria: It is the type of plankton formed by bacterial communities. Its main function is to break down waste and play an important role in the biogeochemical cycle of carbon, nitrogen, oxygen, phosphorus and other elements. It is also ingested through the food chain.
  • Planktonic viruses: they are aquatic viruses. They are mainly composed of bacteriophage viruses and some eukaryotic algae. Its main function is to remineralize nutrients in the biogeochemical cycle and form part of the nutrient chain.

Types of plankton


Most plankton organisms are microscopic in size. This makes it impossible to see with the naked eye. The average size of these organisms is between 60 microns and a millimeter. The different types of plankton that can exist in water are as follows:

  • Ultraplankton: They measure about 5 microns. They are the smallest microorganisms, including bacteria and small flagellates. Flagellates are those creatures that have flagella.
  • Nanoplankton: They measure between 5 and 60 meters and are formed by unicellular microalgae, such as small diatoms and coccolithophores.
  • Microplankton: They are larger, reaching between 60 microns and 1 mm. Here we find some unicellular microalgae, mollusk larvae and copepods.
  • Medium plankton: the human eye can see creatures of this size. It measures between 1 and 5 mm and is made up of fish larvae.
  • Large plankton: between 5 mm and 10 cm in size. Here came sargassum, salps and jellyfish.
  • Giant plankton: creatures over 10 cm in size. We have jellyfish here.

All organisms that exist in plankton have different types of bodies and respond to the needs of the environment in which they live. One of these bodily needs is the buoyancy or viscosity of the water. For them, the marine environment is viscous and it is necessary to overcome resistance to move in the water.

There are many strategies and adaptive measures to promote floating water can increase the chance of survival. Increasing the body surface area, adding fat droplets to the cytoplasm, shelling, shedding and other structures are different strategies and adaptations to be able to survive in different marine and freshwater environments. There are other creatures that have good swimming ability, thanks to flagella and other locomotive appendages, as is the case with copepods.

The viscosity of water changes with temperature. Although we do not show ourselves with the naked eye, microbes do notice it. In warmer waters, the viscosity of the water is lower. This affects the buoyancy of the individual. For this reason, diatoms have formed a cyclomorphosis, which is the ability to form different body shapes in summer and winter to adapt to changes in the viscosity of water with temperature.

Importance for life

nano aquarium plants

People always say that plankton is an important element of any marine habitat. Its importance lies in the food chain. The food web between producers, consumers and decomposers is established in the biome. Phytoplankton can convert solar energy into energy that can be used by consumers and decomposers.

Phytoplankton is consumed by zooplankton, which in turn is consumed by carnivores and omnivores. These are predators of other creatures and the decomposers ingest the carrion. This is how the entire food chain is formed in aquatic habitats.

Phytoplankton absorb a large amount of carbon dioxide through photosynthesis and contribute almost 50% of the oxygen we breathe into the atmosphere. The dead plankton produces a layer of sediment, once fossilized, it produces the much desired oil.

As you can see, sometimes the most important thing is very small in size. In this case, plankton is the basis of the marine habitat's diet. I hope that with this information you can learn more about what plankton is, its characteristics and its importance.

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