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Seaweed - the source of oxygen and many fine jokes

Updated: Feb 26

Walking the South West Coast Path, I was embarrassed when I realised how little I knew about seaweed, so I’ve done a bit of research and this is what I’ve unearthed:

  • The British Isles are globally important for seaweeds because we have so many – over 650, in fact.

  • Seaweeds are not weeds! They are like the forests of the oceans, providing food and shelter for thousands of animals, including some of the fish that our commercial fisheries rely on.

  • Climate change is already affecting seaweeds. Sea surface temperatures have increased by 2 degrees centigrade over the last 40 years. This means that cold water seaweeds are beginning to move north, and warm water seaweeds are heading our way.

  • Some seaweeds have chalky skeletons. There is some concern that the acidification of the ocean, caused by the increasing levels of carbon dioxide in the air, could corrode these.

  • Non-native seaweeds have been living here for some time but are increasing more rapidly than in the past. We don’t yet know what impact this is having on our shores.

  • Kelp (a type of seaweed) can grow up to two feet a day, a process that uses a lot of carbon dioxide. Bits of the plants float out to sea and ultimately sink, trapping carbon in the seabed.

  • In the same way that trees release oxygen as they grow, so does seaweed. Ocean-based plants (including seaweed) are thought to produce more than half of the oxygen we breathe.

  • Some seaweeds are edible, for example nori, which we see wrapped around sushi, and laver, the main ingredient of laverbread in Wales.

  • Seaweed is also used as a fertilizer, animal feed, fish feed, fuel, ingredient in cosmetics, and for aquaculture and wastewater treatment (including the removal of heavy metals from water).

  • One of the funniest jokes ever involves seaweed:


Thank you to the Natural History Museum and Marine Conservation Society’s Big Seaweed Search, Harvard student Sylvia Hurlimann and the UN Food and Agriculture Organisation for helping to enlighten me.

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