Biodiversity & Conservation

Fucus serratus, sponges and ascidians on tide-swept lower eulittoral rock


<i>%Fucus serratus%</i>, sponges and ascidians on tide-swept lower eulittoral rock
Distribution map

LR.HLR.FT.FserT recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

  • UK_BAP

For a list of 2004 characterising species please see the JNCC website.

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
Key Structuring Fucus serratus Toothed wrack
Important characterizing Ascidiella scabra A sea squirt
Important characterizing Halichondria panicea Breadcrumb sponge
Important other Chondrus crispus Carrageen
Important other Dynamena pumila A hydroid
Important other Alcyonidium gelatinosum A bryozoan
Important other Pomatoceros triqueter A tubeworm
Important other Patella vulgata Common limpet


Fucus serratus forms a canopy within this biotope that provides protection from desiccation for the various underlying foliose red seaweeds in addition to providing a substratum for a diverse range of epifauna. It plays an important structural role and its removal would lead to the loss of the biotope. Of the two phyla that give the biotope this name, the ascidian Ascidiella scabra and sponge Halichondria panicea are most frequently associated with this biotope and have been listed as important characterizing species. The hydroid Dynamena pumila, the bryozoan Alcyonidium gelatinosum and the tubeworm Spirorbis spirorbis has been included as other important species as they are the most common representatives (in this biotope) of the diverse range of suspension feeders. These three species were also found to be the most prominent of 91 taxa found on 65 Fucus serratus plants in Strangford Lough, Northern Ireland (Boaden et al., 1975). Although the false Irish moss Mastocarpus stellatus was the red seaweed found most often in records of this biotope, more information was available on Chondrus crispus, to which it is thought to be very similar, and this has been used to indicate sensitivity of the red seaweeds likely to be found under the Fucus serratus canopy.

Additional information

The MNCR recorded 393 species in 56 records of this biotope, although not all of the species occurred in all records of the biotope (JNCC, 1999).

This review can be cited as follows:

Marshall, C.E. 2005. Fucus serratus, sponges and ascidians on tide-swept lower eulittoral 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: <>