The habitat scale in characterising the marine environment

The marine environment can be described or characterised at a number of different scales, ranging from ocean-level processes through to those that occur at species and genetic level (Connor et al. 2002). The scales of relevance here are marine landscapes, habitats and species; their inter-relationship can be expressed as follows:

  • Species provide the globally accepted original classification of biological diversity, with well-established rules of taxonomy to distinguish between different types. Their classification is arranged in a hierarchy of genera, families, orders, classes and phyla.
  • Habitats comprise suites of species (communities or assemblages) that consistently occur together, but which are derived from different parts of the taxonomic hierarchy (e.g. kelps, molluscs and fish in a kelp forest habitat). Their classification can also be structured in a hierarchy (biotopes, biotope complexes, broad habitats), reflecting degrees of similarity.
  • Marine Landscapes comprise suites of habitats that consistently occur together, but which are often derived from different parts of the habitat classification hierarchy (e.g. saltmarsh, intertidal mudflats, rocky shores and subtidal mussel beds in an estuary).
The approach to classification or characterisation at each scale differs, each adopting differing factors to suit the requirements at that scale. Whilst the classification (taxonomy) of species, and to a lesser degree habitats, is now well established the seascapes concept and their characterisation is a more recent approach to characterisation of the marine environment (Laffoley et al. 2000, Day & Roff 2000). The marine landscape concept was applied to the seabed and water column of the Irish Sea as part of the Irish Sea Pilot project.