Vegetation on Rocky Shores at Some North Irish Sea Sites

SUMMARY The intertidal vegetation of Hilbre Island, Merseyside, is compared with that of seven unpolluted localities on the Isle of Man and with that of New Brighton, Merseyside, which is grossly polluted. The Hilbre and New Brighton samples may be assigned either to the littoral fringe or to the eulittoral zone but not to the sublittoral fringe as defined by Lewis (1961). The Hilbre samples are floristically intermediate between those from New Brighton and the Isle of Man. This intermediate character is also apparent in species diversity, life-form composition, biomass and dominance. These features, together with historical evidence, illustrate the process of degradationl which the Hilbre vegetation has undergone throughout this century, and suggest possible future trends.