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

A red seaweed (Plocamium cartilagineum)

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



A bright scarlet seaweed up to 30 cm in length with branching fronds. The branching occurs alternately along the fronds and becomes more frequent towards the tips. The general appearance of these seaweeds can greatly vary from very compact and closely branched to a much broader appearance with widely separated branching. The tips are incurving and ultimate branching occurs only to one side, giving a distinctive feathery or comb-like appearance.

Recorded distribution in Britain and Ireland

Widely distributed around Britain and Ireland.

Global distribution

NE Atlantic, Mediterranean, Pacific, Indian Ocean, Australasian Antarctica


Grows on rocks in shallow water and as an epiphyte on other seaweeds e.g. on the stipe of Laminaria hyperborea.

Depth range


Identifying features

  • Bright scarlet branching fronds.
  • Branching frequency increasing towards tips, which are incurving giving a feathery or comb-like appearance.
  • Branching on tips to one side only.

Additional information

The variety Plocamium cartilagineum uncinatum displays reflexed rather than incurved branching at tips but is less common in British Isles and more frequent in Mediterranean.

Listed by

- none -

Further information sources

Search on:


  1. Campbell, A.C., 1982. The Hamlyn guide to the flora and fauna of the Mediterranean Sea. London: Hamlyn.

  2. Dixon, P.S. & Irvine, L.M., 1977. Seaweeds of the British Isles. Volume 1 Rhodophyta. Part 1 Introduction, Nemaliales, Gigartinales. London: British Museum (Natural History) London.

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


This review can be cited as:

Smirthwaite, J. 2006. Plocamium cartilagineum A red seaweed. 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 25-09-2018]. Available from:

Last Updated: 07/11/2006