Sea lettuce (Ulva lactuca)
|Also known as:||green laver|
|Size||Length: typically up to 100 mm, but may reach 300mm or more (2)|
Not threatened (3).
Sea lettuce is a common green seaweed with a broad translucent frond (3) that is just 2 cell layers thick (2). This seaweed has a rather ‘crumpled’ appearance and is reminiscent of a lettuce leaf, hence the common name (4). The frond is typically bright green or dark green in colour with paler margins that are often white (2). It attaches to the substratum with a small disc-like holdfast, but in sheltered areas it may detach and live as large free-floating masses (2).
This common species is ubiquitous around the British coastline (4) save for very exposed rocky shores (3). It is found almost worldwide (4).
Found on all levels of the shore. It can tolerate brackish water and is also found in estuaries (3). It can also survive as a free-floating mass in sheltered waters (2).
In some parts of the world this seaweed is eaten as ‘green laver’ (3). It is also sold as a medicine in China (4).
This species is not threatened.
For more on this species see: Pizzolla, P. F. (2003) Ulva lactuca. Sea lettuce. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme. [On-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 27/11/2003]. Available on-line at:
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- Brackish: slightly salty water.
National Biodiversity Network Species Dictionary (September 2003)
- Fish, J.D. & Fish, S. (1989) A student’s guide to the seashore. Unwin Hyman Ltd., London
Pizzolla, P. F. (2003) Ulva lactuca. Sea lettuce. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme. [On-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 27/11/2003]. Available on-line at
- Gibson, R., Hextall, B. & Rogers, A. (2001) Photographic Guide to the Sea & Shore Life of Britain and North-west Europe. Oxford University Press, Oxford.