Plan no. 23 Sabellaria alveolata Reefs

Sabellaria alveolata reefs comprise tightly packed honeycomb-like masses of tubes constructed by this small polychaete worm.  The reefs can be up to 50cm thick, forming sheets, hummocks or massive formations, usually in the lower intertidal, or less frequently higher on the shore or in the shallow subtidal.  S. alveolata requires a hard substratum (from bedrock to pebbles) on which to build its tube, and suspended sand grains lifted into the water column in strong or moderate wave conditions. Cover by a reef in any one area may vary greatly over a number of years, but long-term reefs tend to be found on the same shores.

Individual worms typically live three to five years, but reefs can persist longer with further settlement onto existing colonies. Established reefs can increase local biodiversity, by providing a solid habitat for many species, and by restricting drainage on shores, creating rockpools.  S. alveolata reefs are on the northern extremity of their range in the UK, and are reported to be found only in the south and west coasts, between Lyme Bay and the Solway Firth, with notable reefs in the Severn Estuary and Morecambe Bay.  However, the species has been recorded in Kent in the Marine Nature Conservation Review and found in the shallow subtidal in Kent around 1980.

Its continued presence in Kent needs to be determined.  There is evidence of a significant contraction in range on the south coast in the 20 years prior to 1984, for unknown reasons.  

• Sabellaria alveolata reefs are at the northern end of their range in Britain and are affected by extremely cold winters, after which they may die back for many years, particularly at higher shore levels.  Prevalence of less severe winters could favour development or persistence of reefs.  
• S. alveolata can tolerate burial for days or weeks, but will be killed by prolonged burial.  
• Reefs typically occur in areas with large-scale changes in the amount of sand, but they may be vulnerable to accumulations or losses of sand as a result of shoreline development or management.  
• Sea level rise and potential loss of suitable intertidal or shallow subtidal habitats through movement of the intertidal zone, alterations in character of intertidal habitats, and loss of intertidal habitats from coastal squeeze.
• Damage from beaching of small craft, and trampling damage, particularly on popular tourist beaches.
• Extraction of worms for angling bait has been recorded.
• Competition for space with Mytilus edulis, especially on boulder scars. The factors influencing this are not well understood. Heavy settlement of mussels on reefs is thought to cause short-term destabilisation.
• S. alveolata has very variable recruitment, for reasons not well understood.  Lack of larval supply and wave exposure are thought to be important factors in the general absence of reefs in various locations.

• Intertidal protection for S. alveolata is possible through SSSI designation. S. alveolata reefs are also sub-features of non-reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive, and are present in certain UK Special Areas of Conservation (SACs), though many reefs lie outside protected areas.
• Discharges to the sea are controlled by a number of EC Directives, including: Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, Bathing Waters, and the forthcoming Water Framework Directive. OSPAR and North Sea Conference declarations provide powers to regulate discharges to the sea, and have targets and quality standards for marine waters.  UK legislation includes standards covering metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients.
• There is currently very little research on S. alveolata in Britain. The UK Marine SAC project commissioned a report summarising the dynamics and sensitivity of biogenic reefs, including S. alveolata.
• Aerial photographs have been used by the conservation agencies to map intertidal S. alveolata reefs.  
• The MNCR database holds information on the occurrence of S. alveolata around the UK coast, including about 10 sites around the Kent coast, but the continued existence of these needs to be determined.

1. To determine the existence, location and extent of Sabellaria alveolata reefs around the Kent coast.
2. To maintain the distribution and quality of any S. alveolata reefs found around the Kent coast.
3. To encourage/contribute to national BAP research initiatives to determine the habitat conditions required for re-establishment of S. alveolata reefs.

The relevant UK Habitat Action Plans:

• Sabellaria alveolata reefs
• Sabellaria spinulosa reefs
• Littoral & sublittoral chalk

This should be read in conjunction with the following Kent Habitat Action Plans:

• Littoral & sublittoral chalk
• Marine
• Maritime cliff & slope
• Sabellaria spinulosa reefs