Clean, healthy rocky shores are typically colonized by a diversity of plants and invertebrates, both of marine and terrestrial origin. Key species are often zoned vertically according, for example, to tolerance of desiccation. This zonation gives rocky shores a distinctive, banded appearance at low tide.
Shore zonation (26K JPEG image) is particularly vivid along
the red rocky shores of the Dale Peninsula, where the tanker went aground. A dark
belt of brown seaweeds, a white belt of barnacles and a black belt of lichens dominate the
lower, middle and upper shore levels respectively.
A variety of molluscs such as limpets and winkles are usually present, grazing the cover of algae and invertebrates.
The flora and fauna of rock pools on the shore are often particularly diverse. Permanent submergence allows species intolerant of desiccation to live within pools on the shore.
Various coastal birds feed on rocky shores at low tide. At high tide, their place is taken by coastal fish.
Rocky shores vary in their sensitivity to oil pollution. Survivorship of shore life on wave-exposed shores is likely to be higher than that upon sheltered rocky shores.
During the early weeks of the Sea Empress oil spill, some oiled, wave-exposed shores close to the scene of the grounding improved substantially through self-cleaning, with most of the oil dispersed and a high level of apparent survival of shore life. The same was not true, however, for sheltered, heavily oiled shores, where mass-mortalities of limpets and other species were recorded and where encrusted oil residues were particularly persistent.
During the following summer 'green flushes' developed on badly affected shores - the mass kill of herbivorous molluscs allowed carpets of green seaweeds to flourish.
Dead limpets
accumulated in a rock pool
School of Biological
Sciences | University of Wales Swansea
Authors: Peter Dyrynda, Rob Symberlist
Contributor: Peter Hayward
Contact: P.Dyrynda@swansea.ac.uk
Update: 8 February 1998