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

Species indicative of sensitivity

To assess the sensitivity of the biotope, the sensitivity of component species is reviewed. Those species that are considered to be particularly indicative of the sensitivity of the biotope, and for which research has been undertaken in detail are shown below (see selection criteria). The biology of other component species of the biotope is also taken into account wherever information is known to the researcher.

Community Importance Species name Common Name
Important characterizing Furcellaria lumbricalis A red seaweed
Important characterizing Polyides rotundus A red seaweed
Important other Clavelina lepadiformis Light bulb sea squirt
Important other Ciona intestinalis A sea squirt


Furcellaria lumbricalis is one of the algal species which defines the biotope. Loss of the species would result in loss of the biotope but would not result in changes in the community as there are other species in the biotope, for example Polyides rotundus, which fulfil a similar role. The epifaunal and epiphytic communities associated with Furcellaria lumbricalis would be lost along with the species but are also capable of attaching to other algal species or to bedrock where it is available, so would rapidly recolonize. Furcellaria lumbricalis is therefore assessed as "important characterizing" but not "key". It is likely that the sensitivity assessments for Furcellaria lumbricalis would also apply reasonably accurately to the very similar Polyides rotundus. For this reason, it has not been considered necessary to assess each of the 2 algal species separately and only Furcellaria lumbricalis has been used in the biotope sensitivity assessments.
The ascidians, Clavelina lepadiformis and Ciona intestinalis, are not important for the viability of the characterizing species but should be considered when assessing the sensitivity of the community and hence are categorized as "important other".

Additional information

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 30/11/2015]. Available from: <>