Unicellular algae: what are they, characteristics, types and examples

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 indicates, unicellular algae are unicellular organisms , that is, they are made up of a single cell , of the eukaryotic or prokaryotic type, therefore it is 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 , they constitute the base of primary producers. 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.

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

Forms and organization of single-celled algae

Unicellular 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 in 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 unicellular 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.

The current classification of unicellular algae is based on morphological and genetic characters that allow the taxonomy of unicellular algae to be established . In the following list we will see how unicellular algae are 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 ( Cianophytas ).
• Dinoflagellates ( Dinophytas ).

Learn more about Algae Classification with this other AgroCorrn post.

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

Diatoms

• 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.

Dinoflagellates

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

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