The MNCR biotope classification
The Marine Nature Conservation Review (MNCR) has developed a system of classification
of shallow-water benthic marine communities based on surveys of a very wide range of
subtidal and intertidal sites and the relevant literature. The MNCR biotope scheme (Connor
et al, 1997) allows the classification of areas according to a combination of
biological and habitat characteristics. Biotope maps are being produced for areas of
The hierarchical structure of the scheme is designed for classifying areas of seabed
based on their physical and biological characteristics (Connor et al., 1997).
Larger-scale differences among shores, including intertidal reefs, are effectively
represented at the highest level of division by the 28 habitat complexes. Biological
communities thereon are recognisable in the 60 biotope complexes into which these habitat
complexes are subdivided. Further subdivision of these complexes results in the biotopes
themselves (see summary table for biotopes of relevance to rocky shores).
Some rocky shore communities are highly variable
in space and time (mussel-barnacle mosaics, Lewis,
1976, Fucus-barnacle mosaics, Hartnoll and
Hawkins, 1985; Hawkins et al., 1992) while
others are very stable (beds of Ascophyllum
spp.; barnacle-limpet communities on verticals).
In consequence classification of rocky shores according
to the biotope scheme from a single site visit should
be attempted with caution. Many of the biotopes
listed in the scheme may represent stages on continua
in either space or time (see table
for biotopes of relevance to rocky shores).
As an aid to the rapid assessment of shores the biotope classification has value for
early management decisions. Broader application must account for the known limitations.
Many communities on intertidal bedrock, and especially on unstable boulder shores, may
suffer high levels of physical disturbance. Biological communities in such habitats may
reflect successional stages towards a climax rarely achieved. Topographically
heterogeneous shores may contain a mosaic of interspersed community types, leading to
major problems of classification to a single biotope. Finally, a single biotope class for
a shore community may mask information on individual species with potentially important
consequences for conservation. Disappearance of sensitive species, such as the dogwhelk Nucella
lapillus in areas of high levels of tributyltin, may not result in a change in biotope