information on the biology of species and the ecology of habitats found around the coasts and seas of the British Isles

Rainbow wrack (Cystoseira tamariscifolia)

Distribution data supplied by the Ocean Biogeographic Information System (OBIS). To interrogate UK data visit the NBN Atlas.



Cystoseira tamariscifolia is a bushy seaweed, up to 60 cm in length but usually 30-45 cm. It has a cylindrical frond and branches irregularly. The reproductive bodies on the end of branches are long, oval and spiny. Small air bladders are usually found below the reproductive bodies. Cystoseira tamariscifolia is olive green in colour, almost black when dry. When the plant is seen underwater it has a blue-green iridescence.

Recorded distribution in Britain and Ireland

A southern species recorded in southwest Britain, recorded around the coast of Ireland predominantly in the west and although recorded from the Hebrides, rare in the north.

Global distribution

Found in the north east Atlantic, Mediterranean and southeast Atlantic.


Found in rockpools and on the lower shore. Grows on both rocky shores and gravelly flats.

Depth range


Identifying features

  • Blue-green iridescence underwater.
  • Almost black when dry.
  • Rough texture, bushy appearance.

Additional information

May be confused with other species of Cystoseira but can be distinguished by the characteristic blue-green iridescence when the plant is underwater.

Listed by

- none -

Further information sources

Search on:


  1. Fish, J.D. & Fish, S., 1996. A student's guide to the seashore. Cambridge: Cambridge University Press.

  2. Gibson, R., Hextall, B. & Rogers, A., 2001. Photographic guide to the sea and seashore life of Britain and north-west Europe. Oxford: Oxford University Press.

  3. Guiry, M.D. & Nic Dhonncha, E., 2002. AlgaeBase. World Wide Web electronic publication,

  4. Hardy, F.G. & Guiry, M.D., 2003. A check-list and atlas of the seaweeds of Britain and Ireland. London: British Phycological Society

  5. Hayward, P., Nelson-Smith, T. & Shields, C. 1996. Collins pocket guide. Sea shore of Britain and northern Europe. London: HarperCollins.

  6. Howson, C.M. & Picton, B.E., 1997. The species directory of the marine fauna and flora of the British Isles and surrounding seas. Belfast: Ulster Museum. [Ulster Museum publication, no. 276.]

  7. JNCC (Joint Nature Conservation Committee), 1999. Marine Environment Resource Mapping And Information Database (MERMAID): Marine Nature Conservation Review Survey Database. [on-line]

  8. National Biodiversity Network (NBN) Atlas website. Available from:  Accessed 01 April 2017

  9. Stewart, W.D.P., 1962. Occurrence of Cystoseira tamariscifolia (Huds.) Papenf. On the West Coast of Scotland. Nature, 195, 402-403.


This review can be cited as:

Ager, O.E.D. 2008. Cystoseira tamariscifolia Rainbow wrack. In Tyler-Walters H. and Hiscock K. (eds) Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 21-02-2018]. Available from:

Last Updated: 29/05/2008