Difference Between Kelp and Seaweed

Kelp vs Seaweed

The importance of kelp and seaweed is great, and the differences between those are interesting. It would be important to understand this distinction, as many of the kelp and seaweed species have elevated values in the lifestyles of people with their usages viz. as a food, due to the high nutrient contents. Size, diversity, distribution… etc are some of the factors that vary between kelp and seaweed. However, kelp includes into the group of seaweeds, and this article intends to discuss the differences between kelp and other seaweeds.


Kelps are large seaweeds belong to the Order: Laminariales of the Class: Phaeophyceae (brown algae). Kelp includes in 30 different genera among 1800 species of brown algae. Kelps are found in shallow seawater and grow as forests known as kelp forests. Kelp can grow in cold waters where the temperatures range from 6 – 140C. Additionally, kelps prefer waters with high nutrient contents. Body of most kelp species, aka thallus, consists of flat leaf-like structures called blades those originated from the stem-like parts called stipes. Holdfast anchors the whole body of kelp by attaching to the substrate, which could be either a rock or coral. There are pneumatocysts, gas-filled bladders, in blades to provide buoyancy to kelp. These giant seaweeds can grow at an extremely higher rate that reaches more than 50 centimetres per day. There is a good demand for kelp, as those are rich with nutrients, especially Iodine. For an example, soda ash is produced by burning kelps. Moreover, alginate is a carbohydrate extracted from kelps, which is useful as a thickening agent of ice cream, toothpaste, and many other products.


Seaweeds are primitive sea plants belong to algae family. However, there is no particular definition for the term seaweed, as there is no one common ancestor to seaweeds, meaning it is a paraphyletic group. The necessary adjectives to describe seaweeds would be macroscopic, multi-cellular, benthic, and marine algae. There are three types of seaweeds known as red, brown, and green with more than 10,000 species. However, red algae show the highest diversity with over 6,000 species, and green has the least with about 1,200 species. They can grow in many types of seawaters from ice-cold poles to warmer equator, as long as there is sufficient sunlight for photosynthesis. All the seaweeds have almost the same structure of thallus as described in kelps. Seaweeds have been useful for humans in many ways viz. food, medicine, fertilizer, and industrial products, as those are rich in vitamins and other nutrients. Carrageenan, agar, and many other gelatinous products come from seaweeds.

What is the difference between Kelp and Seaweed?

· Kelp is a type of seaweed classified under brown algae, while seaweeds are a collection of many multi-cellular, macroscopic, benthic, and marine algae.

· There are more than 10,000 species of seaweeds, while the diversity of kelp is much lower to that number.

· The kelp has a common ancestor, but not for all the seaweeds.

· Thallus size of kelps is always gigantic, while it could be either small or large in seaweeds.

· Seaweeds have a larger distribution range than kelps.

· The growth rate of kelp is much higher than many other types of seaweeds.