A Perspective on Biogenic Reefs and SACs

The distribution of major examples of biogenic reefs is given by species in Table 3 and Figure 2, both within cSACs and pSACs, and elsewhere.

No currently proposed SACs were selected specifically on the basis that they contain biogenic reefs. However, biogenic reefs are ‘sub-features’ of other Annex I features such as ‘reefs’, ‘estuaries’ or ‘large shallow inlets and bays’. In some cases biogenic reefs are specifically mentioned as reasons why a site is a particularly good example of an Annex 1 habitat e.g. Mytilus in Morecambe Bay, Modiolus in Strangford Lough, Lleyn Peninsula and the Sarnau and Loch Maddy; Sabellaria alveolata in the Solway Firth and Morecambe Bay.

There are candidate SACs selected on the basis of the presence of ‘reefs’ which do have substantial areas of Modiolus reef (Lochs Duich, Long and Alsh, Lleyn Peninsula and the Sarnau), Sabellaria alveolata reef (Lleyn Peninsula and the Sarnau); and probably Sabellaria spinulosa reef (Lleyn Peninsula and the Sarnau; possibly Berwickshire and the North Northumberland coast) and Mytilus reef (Berwickshire and the North Northumberland coast) (Table 3 and Figure 1).

It is worth noting that an SAC cannot be designated on the basis of an intertidal reef area unless there is also contiguous subtidal reef interest (Brown et al., 1997). In the case of Mytilus and Sabellaria alveolata reefs, which are usually intertidal but may also occur in the shallow subtidal, they are very likely to occur as interest features of SACs designated as ‘estuaries’, ‘large shallow inlets and bays’, or even ‘mud and sand flats not covered by sea water’ or ‘sandbanks which are slightly covered by sea water at all times’, (see Table 3 and Figure 1). Sabellaria alveolata and Mytilus edulis also occur within the Cardigan Bay cSAC, designated on the presence of bottlenose dolphins, Tursiops truncatus. The Wash and North Norfolk Coast cSAC almost certainly has Sabellaria spinulosa reefs which are probably best regarded as an interest feature under ‘large shallow inlets and bays’ (Table 3 and Figure 1). Modiolus forms an interest feature of ‘large shallow inlets and bays’ in Loch Maddy and Strangford Lough.

Serpulid reefs have an extremely limited distribution within the UK (presently known only from one, or possibly two, Scottish sea lochs) and none occur within cSACs or pSACs.

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