UNICELLULAR ALGAE: what are they, characteristics, types and examples

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Within the extensive classification of organisms, algae constitute, without a doubt, one of the most curious and surprising groups. Different cellular organizations, as well as different types of nutrition and type of life characterize the numerous species of algae that fill the planet's aquatic ecosystems with life and color. Specifically, unicellular algae have aroused the interest of scientists and experts for years, given their importance in the ecological relationships of marine and freshwater ecosystems, as well as in their important role as primary producers as part of the well-known phytoplankton.

To learn more about these organisms, continue reading this Green Ecologist article on what are unicellular algae, characteristics, types and examples.

What are single-celled algae

Also known as microalgae, unicellular algae constitute the largest group of algae that exist on the planet today (followed by multicellular algae or macroalgae). As its name suggests, the Single-celled algae are single-celled organisms, that is, they are made up of single cell, of the eukaryotic or prokaryotic type, being therefore necessary to have a microscope to be able to visualize them.

These amazing organisms grouped within the Protista Kingdom, are one of the main links in the trophic and ecological chains within the aquatic and humid-terrestrial ecosystems in which they inhabit, since, being photosynthetic autotrophic organisms, constitute the primary producer base for many interspecific and intraspecific relationships.

In the next sections we will see in detail more characteristics of the surprising unicellular algae, as well as many examples to get to know them better. Also, if you want to learn more about What are unicellular organisms, we recommend this other article.

Single-celled algae: characteristics

Now that we know what this type of algae is, let's see in this section many of the main characteristics of unicellular algae:

Forms and organization of single-celled algae

Single-celled algae have very varied forms of life: some are free-living and float wandering in the aquatic ecosystems in which they inhabit, while others live fixed on the seabed, sometimes even embedded in rocks or located on animals or other algae. larger.

In addition, they are capable of organizing themselves into colonies of the same or different species to survive, as well as forming underwater meadows; while other species instead live independently.

Single-celled algae pigments

The pigments that allow single-celled algae to carry out photosynthesis are of several types: chlorophylls (a, b and c), beta carotenes, phycobilins and xanthophylls. These cellular photosynthetic pigments are responsible for giving the algae green, reddish, brown or even bluish colors.

Where do single-celled algae live?

For their survival, unicellular algae need to have certain physical-chemical characteristics in their environment, such as a certain temperature and composition of the water. They are capable of growing and developing both in fresh and salt water aquatic ecosystems, as well as in lotic ecosystems and lentic ecosystems and even in humid terrestrial ecosystems.

Unicellular algae associations

Like any organism, unicellular algae also develop associations or relationships with other organisms, these being positive (symbiosis) or negative (parasitism). Thus, it is possible to find unicellular algae in symbiosis with fungi (mainly lichens and mycorrhizae), as well as with marine mollusks, amphibians, anemones and corals.

Feeding of single-celled algae

Generally, unicellular algae follow strictly autotrophic nutrition (through photosynthesis), although some species feed in a heterotrophic way through the consumption of other microorganisms. Other species are even capable of developing mixotrophy and alternating both types of nutrition according to environmental conditions and the presence of nutrients that surround them.

How is the reproduction of unicellular algae

According to favorable or unfavorable environmental conditions, unicellular algae are capable of reproducing following sexual or asexual reproduction, respectively. In this way, when they reproduce more quickly and easily asexually, they do so through the mechanism of binary fission (bipartition) or multiple fission, giving rise to new individuals with identical genetic material as that of the parent alga.

Types of unicellular algae and their classification

The current classification of unicellular algae is based on morphological and genetic characters that allow establishing the taxonomy of single-celled algae. In the following list we will see what are unicellular algae called according to the group in which they are within their taxonomy or biological classification of unicellular algae:

  • Diatoms (Bacillariophyceae).
  • Brown algae (Chrysophytas).
  • Blue-green algae (Cyanophytas).
  • Dinoflagellates (Dinophytas).

Learn more about the Classification of algae with this other post from Green Ecologist.

Examples of single-celled algae

In the following list we present some examples of single-celled algae species that fill the planet's aquatic ecosystems with life, grouped according to the classification seen above:


  • Actinella brasilliensis lewis
  • Amphipleura kutzing
  • Achnanthes bory
  • Anphora ovalis
  • Asterionella hassall

Brown algae

  • Synura spp.
  • Stephanophyxis palmeriana
  • Rhizosolenia calcaravis

Blue green algae

  • Rivularia bullata
  • Chroococcus turgidus
  • Anabaena spp.
  • Oscillatoria spp
  • Chlamydomonas spp.


  • Ceratium furca
  • Gymnodinium catenatum
  • Peridinium depresum
  • Pyrodinium bahamense
  • Symbiodinium microadriaticum
  • Noctiluca scintillans

Differences between unicellular and multicellular algae

The main difference between unicellular algae and multicellular algae is based on their cellular structure, being made up of one and multiple cells, respectively. Directly related to algae structure Regarding their cells, the size between both types of algae is also very uneven, being the unicellular microscopic organisms, while the multicellular algae they reach more than one meter in length, like the famous Laminaria digitata and sargassum (genus Sargassum).

If you want to read more articles similar to Unicellular algae: what are they, characteristics, types and examples, we recommend that you enter our Biodiversity category.

  • Alder, V. A. (2014) Marine protists. Félix de Azara Natural History Foundation, Argentina, pp: 354.
  • Delgado, M. & Fortuño, J.M. (1991) Atlas of the phytoplankton of the Mediterranean Sea. Scientia Marina Magazine, Volume 55 (1), pp: 120-133.
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