Littoral communities and zonation on rocky shores in the Bay of Fundy, Canada: an area of high tidal range

The Bay of Fundy, on the east coast of Canada, has a maximum tidal range slightly higher than that of the Bristol Channel and similar environmental conditions, but a more extreme climate. However, the littoral community, despite the common presence of many species, differs greatly. Fundy shores show universal domination by Ascopkyllum nodosum under all exposure conditions and its biomass is very high. Funis vesiculosus is common but its distribution is unrelated to exposure. Fucoid algae normally cover all but a few percent of the midlittoral. As a consequence of this intertidal primary primary productivity is very high and a protected sub-canopy environment very extensive. The standard littoral zones do show a typical pattern but respond only slightly to exposure. Many typical and important species show constant zonation under alt exposure conditions. Typical of this group are A. nodosum and the other fucoid algae. Although the high tidal range does reduce the effect of wave action, this factor alone does not explain the results since they are not repeated in the Bristol Channel. Differences in the suite of herbivores, particularly the absence of Patella species in Fundy, is considered to be an equally important causative factor. Also significant is the modifying effect of the heavy algal canopy itself. Clearance experiments have shown that dominance by A. nodosum is not restored within 10 years and that herbivory, especially by littorinids and limpets, does play a critical role in succession.