Silky thread weed (Derbesia marina)

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



Derbesia marina is a small whispy green seaweed that forms soft, bright green, filamentous tufts. The filaments may reach up to 3 cm in height. The filaments are usually laterally branched and arise from a basal creeping system which penetrates the substrate. Filaments lack cross walls except at the bases of the branches.

Recorded distribution in Britain and Ireland

Found throughout British and Irish coasts, although more common off western Scotland and south-west Britain and Ireland.

Global distribution



Derbesia marina is a subtidal species usually found down to depths of 20 m attached to sponges, shells and other algae, often where the water flow is rapid.

Depth range


Identifying features

  • Bright green filamentous tufts.
  • Laterally branched filaments.
  • Up to 3 cm in height.
  • Chloroplasts are flat and circular.

Additional information

The gametophyte life stage of this species is known as Halicystis ovalis and is club-like, spherical or with small bladders. It is attached to the substratum by slender rhizoids (Burrows, 1991).

Listed by

- none -


  1. Burrows, E.M., 1991. Seaweeds of the British Isles. Volume 2. Chlorophyta. London: British Museum (Natural History).

  2. Dickinson, C.I., 1963. British seaweeds. London & Frome: Butler & Tanner Ltd.

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

  4. 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. Fenwick, 2018. Aphotomarine. Occurrence dataset Accessed via on 2018-10-01

  2. National Trust, 2017. National Trust Species Records. Occurrence dataset: accessed via on 2018-10-01.

  3. NBN (National Biodiversity Network) Atlas. Available from:

  4. OBIS (Ocean Biodiversity Information System),  2024. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. Accessed: 2024-06-12

  5. Royal Botanic Garden Edinburgh, 2018. Royal Botanic Garden Edinburgh Herbarium (E). Occurrence dataset: accessed via on 2018-10-02.


This review can be cited as:

Barnes, M.K.S. 2008. Derbesia marina Silky thread weed. 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 12-06-2024]. Available from:

Last Updated: 02/06/2008