Biodiversity & Conservation

Styela gelatinosa and other solitary ascidians on very sheltered deep circalittoral muddy sediment


<i>%Styela gelatinosa%</i> and other solitary ascidians on very sheltered deep circalittoral muddy sediment
Distribution map

SS.SMu.OMu.StyPse 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.

Species found especially in this biotope

  • Styela gelatinosa

Rare of scarce species associated with this biotope

Community Importance Species name Common Name
Important other Ascidiella scabra A sea squirt
Important characterizing Styela gelatinosa A sea squirt
Key structural Pseudamussium septemradiatum A scallop
Important other Abra alba A bivalve mollusc
Important other Metridium senile Plumose anemone


The biotope is visually dominated by large solitary ascidians of which Ascidiella scabra is the most abundant and represents sensitivity of that group as an important characterizing species. However, the extent to which sensitivity of Styela gelatinosa is represented by Ascidiella scabra is uncertain and no relevant information has been found on Styela gelatinosa. Pseudamussium septemradiatum is a small scallop that has limited information available to assess sensitivity but probably shares characteristics of reproduction and larval biology with other more researched scallops (Pecten maximus, Aequipecten opercularis) used in assessing likely sensitivity. Pseudamussium septemradiatum shells provide an important hard substratum for other species to settle and so is key structural. Abra alba, although only recorded as occasional, is used to represent burrowing bivalve species. Because of the low number of species (17) recorded in the biotope, information on species recorded as rare is also taken account of especially for Asterias rubens, Ciona intestinalis, Metridium senile and Sabella pavonina. The community was sampled remotely so that the abundance of large organisms (which occur in lower densities than smaller ones) such as Asterias rubens and Metridium senile may be higher than suggested.

Additional information

The MNCR recorded 17 species in the single record of this biotope (JNCC, 1999).

This review can be cited as follows:

Hiscock, K. 2002. Styela gelatinosa and other solitary ascidians on very sheltered deep circalittoral muddy sediment. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 28/11/2015]. Available from: <>