A green seaweed (Urospora wormskioldii)

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



Filaments are simple, tapering towards the base and up to 10 cm long. It forms a very fine felt-like covering that varies in colour from dark green to purple and adheres closely to damp, shady surfaces. In good years this 'felt' is dark and conspicuous but in others barely detectable. Growth varies seasonally and is maximum in the early months of the year.

Recorded distribution in Britain and Ireland

Isolated records from the Shetland Islands, east and south coasts of England, Northern Ireland, the Firth of Clyde and the outer Hebrides.

Global distribution

Uncommon around the British Isles. Distributed around Europe and also the Pacific Coast of North America and the Canadian Arctic South.


The filamentous phase occurs on rocks in the intertidal and on submerged rocks and wood surfaces. The Codiolum-like phase, forms, soft dark green turfs over large areas on the upper shore where it may be wetted at every tide or left exposed for several days at a time.

Depth range


Identifying features

  • This species exhibits three different types of thallus depending on environmental conditions.
  • Varies from green to purple in colour.
  • Large cell size (0.1-0.5 mm).

Additional information

The large cell size of this species distinguishes it from other Ulothrix and Urospora species. The three varieties of thallus include, filamentous; dwarf filamentous and unicellular Codiolum-like.

Listed by

- none -


  1. Burrows, E.M., 1991. Seaweeds of the British Isles. Volume 2. Chlorophyta. 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. 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.]

  4. Lewis, J.R., 1964. The Ecology of Rocky Shores. London: English Universities Press.

  5. Morton, O., 1994. Marine Algae of Northern Ireland Belfast: Ulster Museum [Ulster Museum Publication, no. 271]


  1. Kent Wildlife Trust, 2018. Biological survey of the intertidal chalk reefs between Folkestone Warren and Kingsdown, Kent 2009-2011. Occurrence dataset: https://www.kentwildlifetrust.org.uk/ accessed via NBNAtlas.org on 2018-10-01.

  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


This review can be cited as:

Carter, M.C. 2003. Urospora wormskioldii A green 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/1931

Last Updated: 17/07/2003