Types of Algae

Algae are green autotrophic organisms that belong to the Kingdom Plantae and Kingdom Protista both. Strange, right?

Some species of algae are similar to plants and thus placed in Kingdom Plantae. On the contrary, some possess more protists-like characteristics, placing them in Kingdom Protista.

There are over 30,000 species of algae, estimated to be up to 1 million.

Some of the types of algae are unicellular, while some are multicellular. Unicellular Chlorophyta algae belong to the Kingdom Protista. Alternatively, red algae (Rhodophyta), brown algae (Phaeophyta), and multicellular green algae are a part of the kingdom Plantae.

F.E Fritsch categorized Algae into 11 classes in his book “Structure and reproduction of algae.” They are classified based on their modes of reproduction, locomotion, pigmentation, food storage, and thallus structures. One of the major differences between plants and algae in Protista is their cell type (unicellular or multicellular).

Here’s everything you need to know about the 11 types of algae:

Green Algae (Chlorophyceae)

Green algae are single-celled, colonial, filamentous, or tubular. There are over 7000 species of green algae. Most of them live in freshwater, while you may find some in marine water. Chlorophyceae are typically dark green in color. Yet, they may have a yellowish-green or light green color as well.

This algae species is autotroph and performs photosynthesis due to the presence of xanthophylls, chlorophyll, and carotenes. Their cell wall is composed of pectin and chitin. Green algae have double-membrane bound organelles like mitochondria with flat cristae. They reproduce through sexual and asexual reproduction. Sexual reproduction is oogamous, anisogamous, or isogamous. On the other hand, some give rise to zoospores with a single flagellum.

Brown Algae (Phaeophyceae)

Phaeophyceae are marine water algae with no unicellular forms. There are over 2000 brown algae species known so far. They are brown in color due to the presence of xanthophyll or fucoxanthin (brown-colored pigments). Brown algae also contain chlorophyll a, c and carotenoids.

The cell wall of brown algae is made of pectose, cellulose, and algin. Algin is a complex polysaccharide reserved in the algal cell wall to protect them from desiccation and freezing. They reserve food in the form of mannitol and laminarin. Some brown algae, like the Macrocystis, maybe as big as 60 meters.

Red Algae (Rhodophyceae)

Rhodophyceae is a gorgeous algae type with a beautiful red color. There are over 5000 species living in marine and freshwater bodies. They are photoautotrophs with a few species feeding on other red algae. Red algae are the deepest growing algae in the sea.

Their cell wall comprises pectin, cellulose, carrageenan, agar, and funori. Rhodophyceae appear deep red due to the presence of excess phycoerythrin. However, they give a green look in shallow water. This property of changing colors is called chromatic adaptation. These algae reserve their food as floridean starch. They reproduce asexually, sexually, and vegetatively. Sexual reproduction is oogamous, whereas asexual reproduction involves spore formation.

Blue-Green Algae (Cyanophyceae)

Blue-green algae are unicellular, multicellular, or colonial organisms with prokaryotic nuclei. They are found everywhere. Their cell wall is composed of cellulose or pectin. Cyanophyceae contains double-membrane bound structures like mitochondria and chloroplasts. They get their blue color because of phycocyanin. Other pigments include chlorophyll a, xanthophylls, β-carotene, and phycobilin.

Blue-green algae are immotile and reproduce through asexual reproduction. They store food in the form of myxophycean or cyanophycean starch. Cyanophyceae often shows false branching along with special cells known as heterocysts.

Yellow-Green Algae (Xanthophyceae)

Yellow-green algae is a unicellular algae type with only 450 to 650 species. They are typically freshwater organisms, yet some prefer wet soil environments and salt water. Their cell wall is made of silica and cellulose. These algae have a different color than green algae due to the absence of some pigments. This algal group contains chlorophyll a and e, xanthophylls, and β-carotene. Xanthophyceae have one or two flagella at the anterior for locomotion. They reproduce asexually. Sexual reproduction is isogamous and not much common.

Golden Algae (Chrysophyceae)

Chrysophyceae are also unicellular algae. But, there are over 12,000 species of golden algae. Most are found in freshwater, whereas you may find some in salt water. Their cell wall comprises silica and pectin, contrary to Xanthophyceae. These algae possess chlorophyll a, xanthophylls, and P-carotene. They also reproduce asexually like most unicellular algae. However, they store their food in fat instead of carbohydrates. They may have one tinsel-type, or two (one whiplash and one tinsel) flagella.

There are six further types of Chrysophyceae; amoeboid, filamentous, coccoid, capsid, parenchymatous and plasmodial.

Diatoms (Bacillariophyceae)

Diatoms are freshwater, marine water, and terrestrial algae with about 12,000 to 15,000 species. They are unicellular or colonial. Their cell wall is also composed of silica and pectin. Bacillariophyceae contains chlorophyll a, chlorophyll c, β-carotene, and xanthophylls.

They reserve their food in the form of fat. They usually utilize sexual reproduction to multiply. Diatoms appear drum-shaped under microbiology microscopes. They may appear in chains sometimes.

Cryptophyceae

Cryptophyceae are unicellular algae with only about 200 known species. They are easily found in marine water and freshwater. Their cell wall is cellulose. They also reserve their food as starch-like many other types of algae. They reproduce through asexual reproduction and rarely by isogamous sexual reproduction. Cryptophyceae have two unequal flagella for locomotion. They appear red and comma-shaped when observed under a microscope. Most college students have these microscopes to observe unicellular species, but it is important to get an electron microscope to view algae in detail.

Dinophyceae

Dinophyceae are also unicellular organisms living in marine water mostly. They are also present in freshwater. They contain xanthophyll, chlorophyll a, chlorophyll c, and β-carotene. They store their food in the form of fat or starch. Dinophyceae rarely propagate through isogamous sexual reproduction.

Euglenineae

Euglenineae are colonial or unicellular microscopic organisms. They do not contain a cell wall. Euglenineae contain chlorophyll a, b, xanthophyll, and β-carotenes. These algae reserve their food as fat or starch. They do not exhibit sexual reproduction and contain naked ciliated reproductive organs. Euglenineae may contain one or more tinsel-type flagella for motility.

Chloromonadineae

Chloromonadineae is another unicellular type of Algae with a bright green color. They contain an excess amount of xanthophylls. Chloromonadineae are only found in freshwater bodies. They store their food as fat. They use two flagella for motility.

The Bottom Line

Algae are not distinctly divided into one group. Instead, they belong to Protista or Plantae according to their specifications. There are 11 major types of algae including red algae, green algae, blue-green algae, brown algae, etc. Most of them live in freshwater, while some prefer marine water. The different pigments give them specific colors. Some reserve their food as fats, whereas others reserve it in the form of starch. Algae typically use flagella for motility.