Herbivores, such as limpets and periwinkles, browse on seaweed and either large plants or minute species of rocks.
Intertidal organisms are also dependent on the sea for their reproduction.
These organisms must shed their eggs or larvae into the sea, where the larvae may drift around in the ocean currents for weeks or months as plankton before they finally settle down to grow into adults, whether free-living or attached to hard surfaces such as rocks. There is a wide range of intertidal habitats, each of which is divided into separate zones based on the influence of the tide. Hard bottoms, rocky shores At the highest, most exposed section of the intertidal shore, in areas generally wetted only by extreme high tides or by spray, is a zone known as the 'littoral fringe'. At the limit of the high tides, in a zone known as the 'upper eulittoral' zone, small barnacles dominate. Below this zone, in the 'mid eulittorial', where surf conditions are strong, larger barnacles dominate along with the limpets.