The vertical distribution of plants and animals on the shore is rarely, if ever, random. On most shores, as the tide recedes, conspicuous bands appear on the shore as a result of the color of the organisms dominating a particular level roughly parallel to the water line (Figure 2.1). In other places, while the bands or zones are less conspicuous and less readily distinguishable, they are rarely, if ever, completely absent. Stephenson and Stephenson (1949; 1972) and Southward (1958) and Lewis (1955; 1961; 1964) have summarized much of the earlier information on zonation

distribution patterns of intertidal organisms, and have shown that such zones are of universal occurrence on rocky shores, although their tidal level and width is dependent on a number of factors, of which exposure to wave action is the most important. More recent reviews of zonation patterns are to be found in Knox (1960; 1963a; 1975), Newell (1979), Lobban et al. (1985), Peres (1982a,b), Norton (1985), and Russell (1991).