Where Does Seaweed Get its Color?

What colors?

Bursts of green, red and vermilion, orange and brown. It is a characteristic that defines the three main types of seaweeds: the chlorophytes (greens), rhodophytes (red) and ochrophytes (brown).

The first to use this characteristic to class seaweeds was a botanist named William Henry Harvey, pioneer of the field of phycology (the science of seaweeds). With careful observation of the spores of the algae under his 18th century microscope, he noticed that they were always green, pink or brown. His method, a colorful reflection of evolutionary history, is still applicable today.

What are the cause of these differences?

Mainly, they are the result of type-specific pigments found in the plastids (where photosynthesis takes place in seaweed cells).

• Green seaweeds, like plants, get their color from the presence of chlorophyll. Their phylum, Chlorophyta, takes its name from it.
• Red seaweeds, have characteristic accessory pigments than chrlorophyll, notably phycobiliproteins. The two main types are phycoerythrin (red) and phycocyanin (blue). The combination of the two results in a wide spectrum of colors, from deep red to electric blue.
• Brown seaweeds get their color from another type of pigment, carotenoids. Among them, fucoxanthin is the most common. Other molecules, notably phlorotannins, similar to the tannins in wine, can influence their color as well.

Besides their aesthetics, the different pigments are also well known for their biological effects. These include great antioxidant capacity, anti-inflammatory effects, stimulating the immune system and many more. It is just one of the many reasons our research focuses on seaweed in cosmetics. A good example that you can find in your Laboratoires de Biarritz products is Alga-Gorria®, an antioxidant from the red seaweed Gelidium sesquipedale.

If you see some neat seaweed, share it with us on our Pinterest «Seaweed» board! ?