Biodiversity & Conservation

Polyides rotundus and/or Furcellaria lumbricalis on reduced salinity infralittoral rock



Image Anon. - A turf of Polyides rotundus, Furcellaria lumbricalis and filamentous brown algae. Image width ca 1m.
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Distribution map

IR.SIR.Lag.PolFur recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

  • EC_Habitats

Marine natural heritage importance

Listed under EC Habitats Directive
National importance Rare
Habitat Directive feature (Annex 1) Reefs

Biotope importance

The dense algal turf probably provides shelter and foraging areas for fish, including gobies, wrasse and pipefish, and may provide nesting sites for the sticklebacks, Spinachia spinachia and Gasterosteus aculeatus.


No evidence of exploitation of the biotope in Britain and Ireland was found. However, the flora of the biotope contains species which are commercially harvested elsewhere in the world, e.g. Furcellaria lumbricalis in Denmark and Chondrus crispus in Canada, and is therefore potentially at risk from exploitation.

Extraction of Furcellaria lumbricalis was reviewed by Guiry & Blunden (1991). Commercial beds of Furcellaria lumbricalis occur in Denmark where the algae are harvested with purpose built trawl nets, whereas in the rest of Europe, the biomass is not sufficient for harvesting. In Denmark, harvesting reached its highest level of 31,000 t p.a. in 1962, but over-exploitation has led to a fall in production and the current harvest is about 10,000 t p.a. Christensen (1971) (cited in Bird et al., 1991) and Plinski & Florczyk (1984) noted that over-exploitation of Furcellaria lumbricalis has resulted in severe depletion of stocks. A sustainable harvest of Furcellaria lumbricalis occurs in Canada on the shores of the Gulf of St Lawrence where the harvest is sustainable as dredging and raking are prohibited and only storm cast plants may be gathered.

Additional information icon Additional information

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This review can be cited as follows:

Rayment, W.J. 2001. Polyides rotundus and/or Furcellaria lumbricalis on reduced salinity infralittoral rock. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 01/12/2015]. Available from: <>