UK biodiversity action plan for maerl

BIOMAERL programme

A biodiversity action plan for maerl as a habitat is being prepared by S. Scott, and is currently in draft stage. The action plan notes that three of the statutory Marine Nature Reserves in Britain, Skomer in Wales, Lundy in England and Strangford Lough in Northern Ireland, contain maerl (although none have particularly well-developed beds). It also notes the potential value of SSSI legislation in protecting maerl. Although most maerl beds cannot normally be included within SSSI designations in England and Wales where the lower limit of SSSI designation is usually mean low water, in Scotland, the planning boundary is normally the mean low water of spring tides, which could include maerl where it occurs in the subtidal fringe. This happens at a few sites, for instance at Taynish on the shores of Loch Sween, Argyll, where the SSSI boundary (but not the NNR boundary) extends to mean low water of spring tidcs and includes the high marine interest in the rapids. However at best SSSI designation can only afford limited protection to a very small proportion of total maerl populations. Proposed actions include:

• Listing maerl beds under Annex 1 of the Habitats Directive, both in their own right and as a specific component of sealoch systems.
• Pressing for the addition of Lithothamnion glaciale to Annex V of the Habitats Directive.
• Ensuring that planning applications for structures such as roads and aquaculture installations are compatible with the conservation requirements of maerl beds.
• Completing surveys of the extent, quality and composition of UK maerl bed communities.
• Listing further sites for eventual classification as SACs to ensure the full range of maerl bed and associated community types and ecological conditions is represented in the network of protected sites.
• Including provision for the maintenance of the extent and health of maerl bed communities in management plans for SACs where these include maerl beds.
• Taking account of the conservation requirements for maerl bed communities in the development and implementation of coastal zone management plans and ensuring that they are not managed in isolation from other habitats and communities in these areas.

The EU MAST-funding BIOMAERL programme, co-ordinated by Prof. P.G. Moore, Millport, is a 3-year collaborative programme between laboratories in UK, Spain, France and Malta, and began in February 1996. Pairs of maerl grounds have been identified for study by participants in the Clyde Sea area (Scotland), Galicia (Spairl), Brittany (France), Alicante (Spain) and Malta. Each pair represents a ground that has been impacted anthropogenically and a relatively pristine control ground. In Scotland, Alicante and Malta, impacts to maerl habitats derive mainly from the use of towed demersal fishing gears. In the Ria de Vigo (Galicia), the major impacts derive from organic matter falling from moored rafts used in the culture of the edible mussel. In the Bay of Brest (Brittany), maerl beds are also affected by high nutrient and sediment loadings due to eutrophication. Another pair of sites in Brittany (in the Glenan archipelago) are being compared to assess the impact of maerl extraction practices.

The BIOMAERL programme, when complete, will provide the first biogeographical inventory of macrofaunal and floral species in European seas, including identification of key species, their population structure and an analysis of their functional significance in this ecosystem. Assessment of the different anthropogenic threats to this biodiversity experienced over the range of sites considered will generate recommendations as to the most effective management strategies for this sensitive habitat.

The BIOMAERL team propose that one way to advance maerl conservation is the establishment of an Environmental Quality Standard for European maerl grounds which is capable of containing, and integrating, all the pertinent structural and functional aspects of the habitat revealed by their studies. They suggest that this might be achievable by allocating a point score to each of the following indicators: edaphic complexity (sediment stratification), basic energy resources (% organic matter, % epifauna/infauna, % macrodetritivores), complex trophic interactions (% predators, % microdetritivores). A summated score would then represent the overall biodiversity status of a particular maerl bed. Such an index would be capable of being monitored over time to provide a check on environmental change, especially any deterioration. It would also supply a mappable, objectively-derived descriptor that, by virtue of being independent of species composition, would be capable of direct comparison at a pan-European scale.

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