Biodiversity & Conservation

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.

• Cordylophora caspia
• Electra crustulenta

Cordylophora caspia is the dominant species in this biotope, and if lost would result in loss of the biotope. Electra crustulenta is a characteristic species that probably competes for space with Cordylophora caspia. In the absence of a full key information for Electra crustulenta, Electra pilosa has been used to represent its sensitivity except its estuarine habitat preferences. Balanus crenatus is probably another competitor for space and has therefore, been included as an important structural species.

This biotope is represented by only two records from the Tamar estuary, Plymouth, Devon (Hiscock & Moore, 1986; Connor et al., 1997; JNCC, 1999; Moore et al., 1999). The biotope description only includes the species listed above and is very impoverished: in one record the biotope consisted of Cordylophora caspia alone (Hiscock & Moore, 1986). However, the biotope probably supports a species of meiofauna and microfauna/flora that were not recorded in the original survey. Also survey conditions should be taken into account, as the original survey was carried out by diving in the highly turbid waters of the upper Tamar estuary.