... large boulders and loose cobbles such as the area above.

Observe the patches of blue-green algae on the surfaces of the boulders in the upper area. Brown algae and barnacles are visible on the cobbles in the lower area, closer to water.

Patterns of zonation vary from region to region along the coastline. The zones can vary in the type of organism that lives there season to season and even rock to rock as a result of differences in wave action, topography, predation, and competition for space.