Distribution and status of rocky littoral habitats

Rocky shores are an abundant feature of the coastline of the UK, especially on western coasts where exposed bedrock predominates on the coast. While the substratum of most vertically-orientated shores is composed entirely of continuous bedrock, many less steeply shelving shores have more broken rock forms, such as large boulders and isolated reefs. In many places rocky substrata are interspersed with particulate substrata, from cobbles through pebbles to gravel, sand and mud. The presence of mobile particulates, especially sand and shingle, can have a severe scouring effect on sessile forms on rocky substrata and consequent effects on community structure. Rock type has relatively little direct effect on the organisms which live in rocky areas, except where the rock type is extremely friable or porous, such as chalk. The major influence of the geological formation on rocky shore communities is indirectly expressed through the topography of the substratum. Bed form may be set by the susceptibility of the rock to erosion, the angle of sedimentary strata, and the interplay of these factors with the geography of each local region (wave exposure etc.).

Unlike sedimentary (dune systems) or biogenic structures (salt marshes, maerl beds), the existence of rocky littoral reefs in the U.K. is not under threat. Anthropogenic effects such as coastal development or climate change may temporarily alter the rocky substrata but will not significantly alter the area available for colonisation. However, certain types of rocky shores are rare in the UK. These include sheltered limestone and upper estuarine bedrock shores. The scarcity of these shore types means they are potentially vulnerable to localised impacts.

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