What is the Difference Between Red Brown and Green Algae

The main difference between red brown and green algae is that red algae contain chlorophyll a, chlorophyll d, and phycoerythrin, while brown algae contain chlorophyll a, chlorophyll c, and fucoxanthin and green algae contain chlorophyll a, chlorophyll b, and xanthophylls. Furthermore, red and brown algae are mainly marine while green algae are chiefly freshwater species.

Red algae (Rhodophyta), brown algae (Phaeophyta), and green algae (Chlorophyta) are the three groups of algae classified under the kingdom Protista.

Key Areas Covered

1. What are Red Algae
     – Definition, Characteristics, Importance
2. What are Brown Algae
     – Definition, Characteristics, Importance
3. What are Green Algae
     – Definition, Characteristics, Importance
4. What are the Similarities Between Red Brown and Green Algae
     – Outline of Common Features
5. What is the Difference Between Red Brown and Green Algae
     – Comparison of Key Differences

Key Terms

Brown Algae, Chlorophylls, Fucoxanthin, Green Algae, Phycobilins, Red Algae

What are Red Algae

Red algae or Rhodophyta are one of the three types of seaweeds with brilliant red color. This red color is due to the presence of phycoerythrin, a type of photosynthetic pigment. In addition, red algae contain chlorophyll a, chlorophyll d, β-carotene, and phycocyanin. Moreover, red algae can grow in the deeper sea in contrast to brown and green algae. It is due to their ability to absorb blue light.

Figure 1: Red Algae

Also, a group of red algae known as coralline algae is important in the formation of coral reefs. Furthermore, red algae are used in some of the Asian cuisines as food additives.

What are Brown Algae

Brown algae or Phaeophyta (‘dusky plants’) are the largest types of seaweeds. They have a characteristic brown to yellow color due to the presence of a unique combination of photosynthetic pigments including chlorophyll a, chlorophyll c, fucoxanthin, β-carotene, and xanthophylls. Generally, brown algae are exclusively marine and found in the temperate and arctic waters.

Figure 2: Brown Algae

Significantly, brown algae develop a root-like structure called holdfast, anchoring the plant to the substrate. Also, brown algae form a giant kelp forest near the California coat and floating kelp beds in the Sargasso Sea.

What Are Green Algae

Green algae or Chlorophyta are the green color algae in both freshwater and marine habitats. In addition, some of the green algae live in the moist soil. The three types of cellular organization patterns in green algae are unicellular, colonial or multicellular.

Figure 3: Green Algae

Generally, the unicellular forms of green algae including Chlamydomonas contain flagella for their motility. Volvox and Hydrodictyon are the colonial forms of green algae. Some green algae such as Chlorella are non-motile.

Similarities Between Red Brown and Green Algae

• Red, brown, and green algae are the three types of algae mainly classified based on the type of photosynthetic pigments present in them.
• Different combinations of photosynthetic pigments give a unique color to each type of algae.
• However, all types of algae contain chlorophyll a and β-carotene.
• Also, all three belong to the kingdom Protista. They are aquatic, photosynthetic eukaryotes.
• Furthermore, their cell wall contains cellulose.
• Marine algae are mainly considered as seaweed.

Difference Between Red Brown and Green Algae

Definition

Red algae refer to a large group of algae that includes many seaweeds that are mainly red in color while brown algae refer to a large group of algae that are typically olive brown or greenish in color, including many seaweeds. Green algae, on the other hand, refer to photosynthetic algae which contain chlorophyll and store starch in discrete chloroplasts. Thus, this is the basic difference between red brown and green algae.

Classification

Red algae are classified under Rhodophyta, and brown algae are classified under Phaeophyta while green algae are classified under Chlorophyta. Hence, this is one important difference between red brown and green algae.

Type of Photosynthetic Pigments

Furthermore, the type of photosynthetic pigments is the main difference between red brown and green algae. Red algae contain chlorophyll a, chlorophyll d, and phycobilins, while brown algae contain chlorophyll a, chlorophyll c, fucoxanthin, and xanthophylls while green algae contain chlorophyll a, chlorophyll b, and xanthophylls.

Habitat

Another difference between red brown and green algae is that the red algae mainly live in marine habitats, and brown algae exclusively live in marine habitats while green algae mainly live in freshwater.

Unicellular or Multicellular

Moreover, their cellular structure is also a major difference between red brown and green algae. Red algae are mainly multicellular; brown algae are exclusively multicellular; unicellular species are more prominent in green algae.

Nature of Thylakoids

Besides, the thylakoids of red algae are unstacked while three thylakoids are stacked in brown algae. Green algae, on the other hand, contain thylakoid stacks of 2-20.

Motility

Both red and brown algae are sessile while green algae are motile and contain flagella.

Motility of Sperms

Motility of sperms is also a difference between red brown and green algae. Red algae do not produce motile stages during their life cycle, but brown algae produce motile sperms while green algae produce motile sperms with multiple flagella.

Food Reservation

While red algae reserve food in the form of floridean starch, brown algae reserve food in the form of laminarin; green algae reserve food in the form of starch.

Cell wall

The cell wall of red algae is composed of cellulose and sulfated phycocolloids. Moreover, the cell wall of brown algae is composed of cellulose and non-sulfated phycocolloids while the cell wall of green algae is composed of cellulose. Hence, this is another difference between red brown and green algae.

Examples

Some examples of red algae are Irish moss, coralline algae, dulse (Palmaria palmata), etc. Some examples of brown algae are kelp, rockweed (Fucus), Sargassum, etc. while some examples of green algae are sea lettuce (Ulva sp.), which is commonly found in tidal pools, and Codium sp., etc.

Conclusion

Red algae are the red color algae mainly live in marine habitats. They contain chlorophyll a, chlorophyll d, and phycobilins. They store food in the form of floridean starch. On the other hand, brown algae are the brown color algae exclusively found in marine habitats. They contain chlorophyll a, chlorophyll c, fucoxanthin, and xanthophylls as photosynthetic pigments. They reserve food in the form of laminarin. Both red and brown algae are mainly multicellular. In comparison, green algae are the green color algae that mainly live in freshwater. They contain chlorophyll a, chlorophyll b, and xanthophylls. Starch is the main form of food stored by green algae. Therefore, the main difference between red brown and green algae is the type of photosynthetic pigments present, habitat, cellular organization, and the form of food storage.

References:

1. Kennedy, Jennifer. “What Are the 3 Types of Sea Weed (Marine Algae)?” ThoughtCo, ThoughtCo, 13 Sept. 2017, Available Here.

Image Courtesy:

1. “green-moss-nature-outdoor-texture-2798160” By oranfireblade (Pixabay License) via pixabay
2. “Red algae” By Ed Bierman – [1] (CC BY 2.0) via Commons Wikimedia  
3. “seaweed-baltic-sea-coast-beach-sea-1614647” By KRiemer (Pixabay License) via pixabay