The Littoral Zone on Rocky Shores: A Biological or Physical Entity?

Abstract

Ther terminology of the zonation of rocky shores was originally based upon physical factors; i.e., the intertidal region, the splash zone, etc. The limits of communities, however, do not correspond consistently with any of these physical factors. Therefore a biological classification is proposed. The region of grey and orange lichens usually above the highest tides (but in places and at times subject to immersion) is not truly marine. It is proposed that this be called the maritime zone (or perhaps the supralittoral). The littorinid -Verrucaria - Myxophyceae community, usually above extreme high water slack, but influenced by splash and spray, is the littoral fringe. It is considered to be marine, because it contains species from lower regions, but few from above. Below this lies the eulittoral (or littoral) zone. As a rule, all of this is exposed by the tides, and is dominated by organisms of strictly marine ancestry. The sublittoral zone begins with the Laminaria (or some other comparable) community. Depending upon local conditions, it may lie below extreme low water slack, or it may occupy a considerable portion of the intertidal region. There may be a sublittoral fringe at its upper edge, but this is not a universal feature.