Intertidal Zonation

Abstract

The intertidal zone experiences considerable fluctuations in moisture and temperature between high tide when it is submerged under the sea and low tide when it is exposed to air and sun. It is also the place where ocean waves collide with the land, introducing an along-shore gradient of wave force and moisture between wave-exposed headlands and wave-sheltered bays. Despite these extreme conditions, the intertidal zone features an abundance of organisms that are adapted for survival in various niches of this harsh environment. On rocky shores, high densities of sessile or sedentary organisms form characteristic horizontal bands that show remarkable similarities around the world. This pronounced intertidal zonation pattern has inspired generations of naturalists and scientist to untangle the underlying ecological processes and mechanisms. Rocky shores have consequently served a role as outdoor laboratories in which seminal ecological theories were forged and tested through a wealth of field experiments. Other intertidal habitats such as sandy beaches are also subjected to stratified environmental conditions and display biotic zonation patterns resembling those on rocky shores, although less obvious to the eye. Hence, intertidal zonation both of rocky shores and sandy beaches will be described in this article.