This report focuses on ‘Biogenic Reefs’ as part of the UK Marine SAC Project task 1.1 which is reviewing the sensitivity of selected benthic biotope complexes. There are a number of organisms in British coastal areas which can form substantial and often quite solid aggregations (‘Biogenic Reefs’) in areas which would otherwise be composed predominantly of sediments, or on boulders and rocks in sandy areas. The most important of these in inshore areas are Sabellaria alveolata, S. spinulosa, Mytilus edulis, Modiolus modiolus and Serpula vermicularis.

Biogenic reefs were chosen as a target group for study because collectively they encompass a wide range of attributes and environmental requirements, and have a number of significant ecological, economic and scientific values. Biogenic reefs can have a number of important effects on the physical (and probably chemical) environment: they often stabilise sands, gravels and stones; the shells or tubes of the organisms themselves provide hard substrata for attachment of sessile organisms; they may provide a diversity of crevices, surfaces and sediments for colonisation; and accumulated faeces, pseudofaeces and other sediments may be an important source of food for other organisms. For these reasons many biogenic reefs have a very rich associated fauna and flora, which at least in terms of macrofauna is often much richer and more diverse than in surrounding areas. Moreover, Mytilus is particularly important both as a fishery and as a source of food for birds.

The audience for this report is typically marine resource managers working at site level. Therefore, this report summarises existing knowledge of biogenic reefs with particular emphasis on achieving a greater understanding of the ecological dynamics and sensitivity of this biotope complex, through the following:

Definition of Biogenic Reefs

Description of Key Species and Physical Characteristics

Links to MNCR Biotope Classification

Relevant Conservation Initiatives

References