Difference Between Algae and Seaweed (With Table)

Micro-organisms are available in large-scale diversity at the global level. It can combat the exceptional chemical and context background. Abundant of microorganisms are in primeval places in undersea ecosystems, by capturing the sun’s stamina through photosynthesis and with their performance in decomposition, dispensing of the minerals stored in organic tissue.

Autotrophic creatures are labeled as “Algae”. “Micro-organism” is the term used to be defined as the organisms that carry out photosynthesis. The cyano-bacteria are termed as algae. They vary in size from small (microscopic) to large groups (macrophytes).

Algae and seaweed are well-defined and contrasting relation of aquatic entities that are both photosynthetic. Both of them are eukaryotes that come under the kingdom of “Protista”. Their cell walls are incorporated with cellulose. By the process of diffusion, both of them excerpts nutrients from the water.

Algae vs Seaweed

The main difference between algae and seaweed is that algae are a giant, manifold category of photosynthetic eukaryotic plants, spanning from unicellular Micro-algae to Macro-algae. But, seaweed is defined as the macroalgae that are macroscopic in nature, multicellular in structure, and has marine habitation.

Algae are found eminently in water bodies, while seaweed grows in shallow marine waters, which is of 100 m depth. Moreover, both of them play a crucial role in ecosystems as primary and essential producers.

Comparison Table Between Algae and Seaweed

Parameters of Comparison




Chlorophyll consisting of organisms present in
Aquatic habitats like the sea, marine water
and freshwater bodies

Similar to a plant structure that binds
oneself to other rigid and impenetrable
substances in Aquatic habitat.

Comprises of

About 3,20,500 breeds/species

About 10000 breeds/species

Bestows as

Prime producers in Aquatic food chain

Crucial breeding ground for fisheries and
marine varieties.

Type of habitation

In sea, marine and freshwater habitation

Only in marine habitation

Type of plant

Either heterotrophic or autotrophic

Completely Autotrophic

Found as

Free-floating or beneath the water

Beneath the water


Either Macroscopic or microscopic

Particularly macroscopic

Type of micro-organisms

Both multi-cellular and unicellular

Solely multi-cellular

Grows eminently in

Deep and Shallow water

Shallow marine waters (below 100m)

Example of species

Unicellular ‘Micro-algae’ like Diatoms and
Chlorella to ‘Macro-algae’ like Large brown algae


What is Algae?

Algae are one of the most basic or paramount organisms of the world, comes under the kingdom of “Protista”. Algae are said to be both prokaryotic as well as eukaryotic organisms. Their structure can be defined as unicellular or multicellular. They can be macroscopic and microscopic in nature.

They can live in any aquatic environment, which can be freshwater, marine, and even in brackish water. All the Algae bodies are photosynthetic and autotrophic, with a few heterotrophs as well.

They conjointly produce an ample amount of energy by photosynthesis because of the presence of Chlorophyll in them. There are abundant species of their type in the world. Additionally, they produce a huge value of about 70% of the earth’s atmospheric oxygen. They have very simple cellular structures.

There are totally three divisions of algae are:

  1. Chlorophyta (commonly known as “Green Algae”)
  2. Rhodophyta (generally known as “Red Algae”)
  3. Phaeophyta ( frequently known as “Brown Algae”)

All of the above usually vary because of the amalgamation of photosynthetic pigments endowed in the plant bodies. The Green algae are a diversiform class of algae that has chlorophyll, xanthophylls, and beta-carotene.

Although, phycoerythrin is an important type of photosynthetic pigment present in Rhodophyta. On the other hand, the two key pigments found in Phaeophyta are chlorophyll and fucoxanthin.