Rocky shore ecology

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 against desiccation. This zonation gives rocky shores a distinctive banded appearance at low tide.

Shore zonation (27k JPEG image) is particularly vivid along the red rocky shores of the Dale Peninsula, where the Sea Empress 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.

The biologically rich shores of South-West Wales have been studied by generations of school-children and students who have attended courses at Field Centres and Universities within the region. In fact, the overall ecology of the region is much better understood than has been the case for other areas affected by major oil spills. The substantial body of baseline information that already exists for South-West Wales has proved invaluable in the context of impact-related monitoring work.

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.

In the case of some wave-exposed oiled shores close to the scene of the grounding, substantial improvements were evident during the early weeks of the incident, with most of the oil dispersed and a high level of survivorship of shore life.

Dead limpets accumulating in a rock pool (19k JPEG image)

The same was not true, however, for heavily oiled sheltered shores, where mass mortalities of limpets and other species were observed, and where much oil persisted for months rather than weeks.

University of Wales Swansea School of Biological Sciences Home Page

Authors: Peter Dyrynda, Rob Symberlist
Contributor: Peter Hayward
Contact: P.Dyrynda@swansea.ac.uk
Update: 22/1/98

© 1996-2000 P.E.J.Dyrynda and R.C.Symberlist. All rights reserved