Biodiversity & Conservation

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Sheltered and very sheltered mid eulittoral pebbles and cobbles lying on sediment are typically characterized by Fucus vesiculosus. SLR.FvesX is usually subject to some variability in salinity from riverine input or, in more marine conditions, the habitat consists predominantly of smaller stones which are too unstable for Ascophyllum nodosum to colonise to any great extent (compare with SLR.AscX). This biotope typically differs from SLR.Fves in having a less dense canopy and reduced richness of epifaunal species, presumably as a result of the increased siltation, variable salinity and lack of stable substrata. In addition, the sediment between patches of hard substrata often contains the lugworm Arenicola marina, cockles Cerastoderma edule or the ragworm Hediste diversicolor. Littorinids, particularly Littorina littorea, commonly graze on the algae. Ephemeral algae such as Ulva spp. are often present, especially on any more mobile pebbles during the summer. Limpets are less common than in SLR.AscX, because of the limited availability of larger rocks. (Information taken from the Marine Biotope Classification for Britain and Ireland, Version 97.06: Connor et al., 1997a, b).

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