Intertidal Distribution Patterns

Patterns of distribution occur when different organisms able to withstand different degrees of stress are found living in areas along the shore that suit their particular needs.

The upper limit of an organism's distribution on the shore depends largely on its degree of tolerance of the physical environment. However, the lower limits of distributions are usually affected by interactions with other animals and plants such as competition and predation.

Between these two extremes, many habitat features are important determinants of the distribution patterns of intertidal plants and animals.

Vertical distribution

Because all of these distribution-affecting elements can vary so much, it is unusual to find patterns of distribution which are clearly delineated. Intertidal ecology texts now point out that the often referred to concept of "zonation" is actually an extremely oversimplified representation of observed patterns, particularly on gently sloping or undulating intertidal areas such as those found in well-studied Australian locations, including Barwon Heads.

Generally, the greater the slope of the shore and the lesser the variation in the surface form of the rock, the more clearly delineated the distribution pattern will be. On a flat or gently sloping shore line, distribution patterns will often be less distinct from one end of the shore to the other. This said, there are certainly locations within rocky shore sites which support greater numbers of one species than others. It is the ecologist's (and the students') task to construct and test hypotheses relating to the patterns of distribution that result.	Rockpool
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