Three of a kind, the colours of seaweeds!


Seaweeds can be split into three main types. In no particular order, they are simply, red, green and brown. These three types are all found on the seashores of Northern Europe as well as throughout the world. I have much interest in the brown seaweed’s, these include the bladder wracks that I’m sure everyone who lives in temperate climes has seen on a trip to the beach.

Brown Algae (Phaeophyceae)

Fucus spiralis, also known as spiral wrack.The brown algae (Phaeophyceae) appear brown due to the presence of a pigment called Fucoxanthin. This masks the natural green of chlorophyll by reflecting yellow light. Brown algae are all multicellular forms which vary in size from the enormous giant kelps of Macrocystis to the absolutely tiny Punctaria latifolia which rarely exceeds 4 cm in size.

They are exclusively marine and don’t tolerate higher temperatures. This restricts their distribution to temperate or colder climates. They are intertidal or upper subtidal except for the giant kelp which can grow up to 50 m long at a rate of as much as 1 metre per day! Brown seaweeds are very important in industry, with many brown seaweeds being harvested for use in the food, cosmetic, pharmaceutical, textile and agricultural industries.

Red Algae (Rhodophyceae)

Chondrus chrispus.The red algae (Rhodophyceae) contain more marine species than the green and brown combined! With around 3800 currently identified species in total. The red pigmentation allows these species to inhabit greater depths than the greens and browns which are restricted to around 50-60 metres, some species of red algae have been reported at depths of almost 200 m! At depths such as this, away from the volatile coast the water is much calmer and the reds tend to be more delicate. They are also much smaller than the browns and also don’t tolerate fresh water but can exist at higher temperatures.

Green Algae (Chlorophyceae)

Ulva lactuca.The green algae (Chlorophyceae) are truly green. They have no pigments to mask the chlorophyll so they appear a vivid green. This is a very diverse group that ranges from microscopic single cells to large membranous, tubular and bushy specimens. Some occur in freshwater and the most common marine dwelling species can tolerate both brackish conditions and the influx of organic pollutants, so their presence can indicate nutrient outflow.