Terminology: the terms biotope, habitat and community

A biotope is defined as the combination of an abiotic habitat and its associated community of species. It can be defined at a variety of scales (with related corresponding degrees of similarity) and should be a regularly occurring association to justify its inclusion within a classification system.
 
A habitat is taken to encompass the substratum (rock, sediment or biogenic reefs such as mussels), its topography and the particular conditions of wave exposure, salinity, tidal currents and other water quality characteristics (e.g. turbidity and oxygenation) which contribute to the overall nature of a place on the shore or seabed.
 
The term community is used here to mean an association of species which has particular species, at certain densities, in common.
 
Although communities are influenced by biological interactions (e.g. predation, recruitment processes) and by interference from certain human activities, their overall character is very strongly determined by the nature of the surrounding abiotic conditions. This consistent relationship between the biotic and abiotic elements is fundamental to the structure of the classification system. Types can be defined at a variety of scales, enabling the development of a hierarchical classification of types. The degree of similarity varies depending upon the scale considered, with more broadly defined types (e.g. sheltered rocky shores) having a lower level of similarity compared with more finely defined types (e.g. a lower shore sheltered rocky biotope).
 
Whilst the term habitat, as used here, is its more accepted scientific meaning, the term is more widely used, for instance in the EC Habitats Directive, to also include the community of species living in the habitat; the common use of the term is, therefore, synonymous with the term biotope.