Difference Between Algae and Microalgae

Main Difference – Algae vs Microalgae

Algae and microalgae are photosynthetic organisms that serve as an excellent food source in aquatic ecosystems. Algae can be categorized into microalgae and macroalgae. Microalgae are called phytoplankton and macroalgae are called seaweeds. Algae are responsible for the release of oxygen to the atmosphere during photosynthesis. Macroalgae are largely used in saltwater aquariums as a food source and a natural filter, removing nitrogenous wastes. The main difference between algae and microalgae is that algae are simple, autotrophic organisms, consisting of a huge diversity among them whereas microalgae are the microscopic type of algae.

Key Areas Covered

1. What are Algae
      – Definition, Types, Features
2. What are Microalgae
      – Definition, Types, Features
3. What are the Similarities Between Algae and Microalgae
      – Outline of Common Features
4. What is the Difference Between Algae and Microalgae
      – Comparison of Key Differences

Key Terms: Autotrophs, Brown Algae (Phaeophyta), Diatoms, Dinoflagellates, Green Algae (Chlorophyta), Macroalgae, Microalgae, Red Algae (Rhodophyta), Seaweeds, Thallus

What are Algae

Algae are a simple, non-flowering, aquatic organisms, consisting of many single-celled forms and seaweeds. However, algae do not consist of true stems, root, leaves, and a vascular system. Since algae have a huge diversity, they can be found everywhere on earth. Algae play a major role in aquatic food chains by acting as primary producers. Around 70% of the oxygen in the atmosphere is produced by algae. Algae can grow in water resources such as sea, brackish, and waste water systems. The reproduction of algae occurs both sexually and asexually. Two types of algae can be identified; microalgae and macroalgae. The large-celled, autotrophic algae are referred to as macroalgae. Macroalgae are commonly called as seaweeds. They are very important sources in aquatic ecosystems as they serve as great food sources for herbivorous animals. In addition, macroalgae serve as natural filers by reducing the levels of nitrites/nitrates and phosphates from the water. This is why macroalgal filters are popular among saltwater aquariums.

Figure 1: Red algae on a bleached coral

The root-like structure of the macroalgae is called the holdfast, and this provides support to the plant body. Macroalgae consist of blades, corresponding to leaves of a true plant. The frond is a collection of blades. The plant body of macroalgae is called the thallus. The float of macroalgal thallus is assisted by air-bladders. At the center of the frond, a mid rib is present in some macroalgae. Based on the type of photosynthetic pigments present, three type of macroalage can be identified as green algae (Chlorophyta), red algae (Rhodophyta), and brown algae (Phaeophyta).

What are Microalgae

The unicellular microscopic algae are referred to as microalgae. Microalgae are also commonly called as phytoplankton. Many microalgae are autotrophs, which use photosynthesis to produce food. Some heterotrophic microalgae can grow in the dark by utilizing sugars. A few microalgae grow by combining both nutritional modes and they are called mixotrophic algae.

Figure 2: Microalgae

Diatoms and dinoflagellates are the two types of microalgae. Diatoms can be spheres, triangles, elliptical or stars. A silica shell serves as the cell wall of diatom cells, protecting the cells. Many dinoflagellates comprise two flagella for their movement through water. Both diatoms and dinoflagellates comprise oils in their cells, helping them to swim. Both diatoms and dinoflagellates can grow very quickly and cause algal blooms. Both types of algae may cause food poisoning in humans. The microalgae are shown in figure 2.

Similarities Between Microalgae and Macroalgae

Both algae and microalgae show large diversity on earth.
Both algae and microalgae serve as excellent food sources in aquatic ecosystems.
They produce most of the oxygen in the atmosphere during photosynthesis.
Both algae and microalgae serve as natural filters of phosphates and nitrogenous wastes.

Definition

Algae: Algae are simple, non-flowering, aquatic organisms, consisting of a large assemblage of single-celled forms and seaweeds.

Microalgae: The unicellular microscopic algae are referred to as microalgae.

Other Names

Algae: Algae are photosynthetic aquatic organisms.

Microalgae: Microalgae are commonly called as phytoplankton.

Number of Cells

Algae: Algae can be either unicellular or multicellular.

Microalgae: Microalage are unicellular organisms.

Types

Algae: Microalgae and macroalgae are the two main types of algae.

Microalgae: Diatoms and Dinoflagellates are two types of microalgae.

Conclusion

Algae and microalgae are excellent aquatic food sources. They also serve as natural filters of nitrogenous wastes. The two types of algae are microalgae and macroalgae. Microalgae are unicellular organisms where as macroalgae are multicellular organisms with simply differentiated body parts. Thus, the main difference between algae and microalgae is the level of classification.

Reference:

1. “Algae Basics.” All About Algae. N.p., n.d. Web. Available here. 25 July 2017.
2. “Macroalgae.” Doctors Foster and Smith. N.p., n.d. Web. Available here. 26 July 2017.

Image Courtesy:

1. “Red Algae on bleached coral” By Johnmartindavies – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “CSIRO ScienceImage 7604 Microalgae” By CSIRO (CC BY 3.0) via Commons Wikimedia