Difference Between Seaweed and Algae

Seaweed vs Algae

These are two interesting groups of organisms, or “plants” inhabiting aquatic ecosystems. Seaweeds include into a portion of algae, and that describes the relationship between these two. However, there are both similarities and differences between seaweeds and algae despite their inconsistency in classification, especially seaweeds. This article intends to discuss the characteristics of these two groups and emphasize the differences between them.

What is Seaweed?

Seaweeds necessarily inhabit the seawaters, and those are primitive plants belonging 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. In fact, it is a colloquial term used to describe a certain group of plants with distinctive properties. 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. Red algae is the group with the highest diversity containing over 6,000 species, and green has the least diversity 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 Algae?

Algae include one of the most primitive organisms on the Earth, with fossils evidences dating back to more than three billion years. Earlier, algae included both prokaryotic and eukaryotic organisms, but now only the eukaryotes are included in the classification. They also do not have a common ancestor. They could be either unicellular or multi-cellular in their structure, and accordingly microscopic as well as macroscopic. They inhabit any aquatic ecosystem including freshwater, saltwater, and brackish water. Almost all the algal species are photosynthetic and show autotrophy. Algae collectively produce the largest amount of energy through photosynthesis. However, they are very simple in cellular structures including the gigantic kelps, without many complex organs (leaves, roots… etc) as in terrestrial plants. This is an extremely diverse group with an unthinkable number of species. According to the US National Herbarium, there are 320,500 collected specimens, but there is no correct estimation on the number of algal species in the world.