The stability of some rocky shore communities under natural
This review describes several causes of natural changes in rocky shore communities. All
communities show some degree of temporal variability and many rocky shore communities show
a good deal of natural fluctuations. The abundance of limpets, barnacles and Fucus
plants may be relatively constant over a large area of shore. However, in a smaller area
of that shore, an aggregation of limpets might be replaced by a patch of barnacles and
then of Fucus plants over the course of a few years.
Connell and Sousa (1983 suggest that communities should be thought of in terms of their
persistence within stochastically defined bounds. In other words, how long will an
assemblage of species coexist, given the natural variability in their populations and will
they continue to coexist after a natural perturbation? Clearly these questions are scale
dependent; the area of interest should be defined before they are asked.
Chapter I describes the MNCR biotope classification scheme which
describes areas according to a mixture of community and habitat characteristics. This
scheme allows a characterisation of the shore at any instant. Any single description of
the status of a community, however, cannot account for the temporal and spatial variation
characteristic of natural ecosystems. These characteristics must be recognised and
accounted for if management and conservation of rocky shores is to be effective.
Ultimately, a well designed monitoring programme will be the best way to understand the
spatial and temporal dynamic features of any given shore community.
The MNCR biotope scheme is likely
to be widely used in the conservation and management
of marine SACs. The appendix
gives a qualitative assessment of the likely stability
and persistence of the communities represented by
the MNCR intertidal reef biotopes (full descriptions
of each type are given in Connor et al., 1997).
Interpretation of the results of single surveys
couched in the terms of the biotope scheme must
take account of the likely permanence (or transience)
of each biotope. CAPITALS denote emphatic statements
about the likely stability can be made.