A brown seaweed (Carpomitra costata)

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



A brown algae with many branched, dorso-ventrally flattened, slightly elliptical thalli, arising from a small stipe and a fibrous holdfast. Fronds up to 25 cm long and 1-3 mm wide, and light to olive brown in colour. Blades quite firm and cartilaginous with a distinct midrib. Tips of fronds with tufts of 'hair'. Specialised structures bearing reproductive organs (receptacles) are formed from extending midrib tissue and are conical or cylindrical and colourless.

Recorded distribution in Britain and Ireland

Carpomitra costata is a southern species found in the southern UK and the Channel Islands and recorded as far north as the Isle of Man, Donegal, Coll Island and St Kilda.

Global distribution

No information found.


Carpomitra costata is epilithic on bedrock and boulders and can be found from the sublittoral to depths of up to 37 m.

Depth range


Identifying features

  • Blades branch pseudo-dichotomously, sometimes tri-radiately or alternately.
  • Apex obtuse or truncated, often with young, projecting, cylindrical terminal branches.

Additional information

The tufts at the extremity of the frond are conspicuous and highly characteristic.

Listed by

- none -


  1. Fletcher, R.L., 1987. Seaweeds of the British Isles vol. 3. Fucophyceae (Phaeophyceae) Part 1. London: British Museum (Natural History).

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

  3. Hiscock, K., Southward, A., Tittley, I., Jory, A. & Hawkins, S., 2001. The impact of climate change on subtidal and intertidal benthic species in Scotland. Scottish National Heritage Research, Survey and Monitoring Report , no. 182., Edinburgh: Scottish National Heritage

  4. Hiscock, S., 1979. A field key to the British brown seaweeds (Phaeophyta). Field Studies, 5, 1- 44.

  5. 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.]


  1. Centre for Environmental Data and Recording, 2018. Ulster Museum Marine Surveys of Northern Ireland Coastal Waters. Occurrence dataset https://www.nmni.com/CEDaR/CEDaR-Centre-for-Environmental-Data-and-Recording.aspx accessed via NBNAtlas.org on 2018-09-25.

  2. NBN (National Biodiversity Network) Atlas. Available from: https://www.nbnatlas.org.

  3. OBIS (Ocean Biodiversity Information System),  2024. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. www.iobis.org. Accessed: 2024-06-16

  4. Royal Botanic Garden Edinburgh, 2018. Royal Botanic Garden Edinburgh Herbarium (E). Occurrence dataset: https://doi.org/10.15468/ypoair accessed via GBIF.org on 2018-10-02.


This review can be cited as:

Skewes, M. 2008. Carpomitra costata A brown seaweed. In Tyler-Walters H. and Hiscock K. Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 16-06-2024]. Available from: https://www.marlin.ac.uk/species/detail/1621

Last Updated: 17/04/2008