B. Vertical Zonation
From this regional survey it is apparent that on the rocky shores of the Hauraki Gulf there exist several clearly defined types of community complex, each associated with a certain kind of substrate. These will now be discussed, and compared with published reports from Piha and the Poor Knights Islands.
In Figures 7-11 the writer has attempted to summarise the principal features of five representative coastlines in the Gulf. Each block diagram has been constructed in the first instance from a recorded traverse; but the symbols for the dominant or abundant organisms are arranged to indicate the most conspicuous features of that type of coast as a whole. Such a presentation is felt to be of greater value at this juncture than an exact replica of the zonation sequence at one restricted site of observation. The stations selected were:
Station 3 (Howick), an extremely sheltered Waitemata Sandstone shore, transitional between rock, sand and mud.
Station 5 (St. Leonards Point, one mile north of Narrow Neck); moderately sheltered Waitemata Sandstone, where tilted ledges form the shore.
Station 28 (Fletchers Bay), a greywacke coast in moderate wave exposure.
Station 29 (Sugar Loaf Rocks), a breccia substrate comprising a high level wave-cut platform and exposed to extreme wave action.
Station 24 (Ti Titoki Flat, Little Barrier), a contrasting shore composed of loose boulders, and affected by moderate or strong waves and currents.