Temperate coastal waters are mixed by waves and convection, maintaining adequate availability of nutrients.
There are also a variety of other challenges such as temperature fluctuations due to tidal flow (resulting in exposure), changes in salinity and various ranges of illumination.
Devised in 1961 by W. J. Ballantine, then at the zoology department of Queen Mary University of London, London, U.K., the scale is based on the observation that where shoreline species are concerned "Different species growing on rocky shores require different degrees of protection from certain aspects of the physical environment, of which wave action is often the most important."
Tidal movements of water creates zonation patterns along rocky shores from high to low-tide.
Garbage such as plastics and metals being left behind by people is also a problem among many rocky coastlines that attract tourists.