The Mode of Occurrence of the Universal Intertidal Zones in Great Britain

Abstract

The Laminarlans generally provide an adequate upper limit to the infralittoral fringe in British waters. The upper limit of the midlittoral zone, normally indicated by barnacles, varies con-siderably in position relative to other species because two barnacles of overlapping geographical range are involved. Alternative methods of delimiting zones by reference to other organisms or to tidal levels are considered unsuitable. The evidence available suggests that while the major intertidal zones are of world-wide occurrence and can be identified by the same types of organisms, the detailed vertical relationships of corresponding species vary from shore to shore.