Bladder wrack

Bladder wrack

Bladder wrack ©Kirsten Smith

Bladder wrack

Scientific name: Fucus vesiculosus
This brown seaweed lives in the mid shore and looks a bit like bubble wrap with the distinctive air bladders that give it its name.

Species information


Length: 15-100cm

Conservation status


When to see

January to December


Probably the seaweed most associated with the seashore, Bladder wrack is a common wrack seaweed which grows between the high and low water marks on rocky shores. Bladder wrack has round air bladders which allow the seaweed to float upright underwater, this helps them exhange gases and absorb nutrients when submerged. It forms dense beds on the mid shore, often together with Egg Wrack. It provides a shelter for many creatures and is a food source for others, including the Flat periwinkle.

How to identify

Bladder wrack is an olive-brown 'wrack' seaweed. It can be recognised by its strap-like, branching fronds that have air-filled 'bladders' along their length (often appearing in pairs either side of the pronounced mid-rib). The edges are not serrated.


Common on rocky shores all around our coasts.

Did you know?

Bladder wrack was once used as a source of iodine to treat goitres. Nowadays, you're more likely to find it in your anti-ageing cream as research has found that it has anti-ageing properties!

How people can help

Bladder wrack and other species of seaweed provide food and shelter for all kinds of shore creatures from grazing molluscs to tiny fish. When rockpooling, be careful to leave everything as you found it - replace any seaweed you move out of the way, put back any crabs or fish and ensure not to scrape anything off its rocky home. If you want to learn more about our rockpool life, Wildlife Trusts around the UK run rockpool safaris and offer Shoresearch training - teaching you to survey your local rocky shore. The data collected is then used to protect our coasts and seas through better management or through the designation of Marine Protected Areas. The Wildlife Trusts are working with sea users, scientists, politicians and local people towards a vision of 'Living Seas', where marine wildlife thrives. Do your bit for our Living Seas by supporting your local Wildlife Trust or checking out our Action Pages.