Rocky Shore plants and animals show both vertical and horizontal zonation in response to their physical and biological environment.
Vertical Zonation
‘Seaweed Zonation’ looks at one example of the phenomenon of ‘vertical zonation’ on the rocky shore, but the article could just as easily have been written about barnacles or winkles. The common factor here is that the rocky shore provides a complex series of challenges to living things – in clearly defined vertical zones. The top of the shore is almost terrestrial while the bottom is almost completely marine – between these extremes there is a whole series of ‘strips’, each with its own marine/terrestrial balance. These zones can be described with reference to tidal phenomena or by referring to the organisms that live there – for example we can either talk of the ‘splash zone’ or the ‘Chthamalus stellatus zone’.
Horizontal Zonation
As we move along the shore horizontally we can move from sheltered bays to exposed headlands. The effects of this exposure to increased wave action will have a dramatic influence on the types of plants and animals that can survive. Very exposed rocky shores are often dominated by barnacles which cement themselves very firmly to the rock, while sheltered shores have a dense algal cover which makes life very difficult for the filter-feeding barnacles. In between these two extremes the balance of plants/grazers – predator/prey – will depend on other factors such as slope, aspect (which direction the shore faces) and of course vertical height above low water.
An experienced marine biologist will be able to tell much about a shore simply by observing the organisms that live there and it will often be possible to say that a particular shore experiences very strong wave action – even on the calmest of days.
