Rachel Lambert: forager, author, guide

The Amazing Bushy Rainbow Wrack Seaweed

Can you see those bright iridescent tips of the Bushy Rainbow Wrack seaweed below?

Maybe you've seen this seaweed in a rock pool in Cornwall and couldn't believe your eyes?! This photo was taken by a friend of mine who was stunned by this shining seaweed. So far, I haven't had a camera with me (rare, I know, in today's world) when I've found myself staring, in a mini state of ecstasy, into a rock pool at this seaweed.

Cystoseira tamariscifolia

Seaweeds are awesome, I never tire or bore of them. They confuse me (they are both simple and complex), amaze me, feed me and allow me to breathe (quite literally as seaweeds produce oxygen). Aah, seaweeds.

Why does the Bushy Rainbow Wrack shine?

Cystoseira tamariscifolia Cystoseira tamariscifolia

One of my seaweed tutors told me that seaweeds are all about sex. I know what she means; seaweeds are hell-bent on reproduction and survival, sometimes having multiple ways of reproducing themselves. Another of their survival tactics is making sure they get enough light in order to photosynthesis.

That's the practical reason that the Bushy Rainbow Wrack seaweed has iridescent tips; to control light. Seaweeds have a lot to contend with, and previously I've written about how and why seaweeds can survive the snow and frost. Their environment is constantly changing in terms of temperature, light, speed and water. Think about it for a moment - a hot sunny day, those seaweeds could be almost cooking in rock pools, and hours later they are submerged in sea water with reduced access to light and dealing with anything from calm, lapping waves to gale force storms. Adaption is the name of the game in order for seaweeds to thrive

It seems that the Bushy Rainbow Wrack seaweed's ability to attract and dispel light helps protect it when underwater or when over-exposed to light. With it's crystal structure it reflects sunlight to give the appearance of glowing, and will actually increase or decrease it's seeming glow depending on how much light there is. Wow. There is so much about seaweeds we still don't know.

Cystoseira tamariscifolia i

So, perhaps you're wondering whether the Bushy Rainbow Wrack is edible?
A reasonable question to ask a forager. The answer is yes, and, there are nutritional and health benefits too, but not  necessarily for humans. If you want a tasty, nutritious seaweed I would teach you other ones first.

I offer thorough courses in seaweed foraging throughout the year which are constantly being updated as my knowledge grows and is integrated into my foraging practice. You are welcome to join a seaweed foraging course and come and explore the wonderful, edible world of seaweeds, to walk, look, nibble and learn with me.

Bushy Rainbow Wrack Cystoseira tamariscifolia 


Science Advances, April 2018

Thank you also to Barry and Sue Petitt for the extra photos.

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