Singapure

Nature of the marine environment
The habitat scale in characterizing the marine environment
The marine environment can be described or characterized 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-relationshipcan 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 occurtogether, 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 fromdifferent 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 establishedthe 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.
 
Environmental influences at the habitat scale
Each species tends to live within a certainenvironment; that is, it has a preference for a combination of environmental factors (a niche), such as the substratum, temperature, salinity and hydrodynamic conditions that it is able to live within. The tolerance to different environmental conditions varies between species; it can be rather broad for some very common species but much more tightly defined for others. The niche occupied by a species mayvary both temporally and spatially and is influenced not only by its physiological requirements and tolerance to change but also by the interactions between species, i.e. competition and predator-prey relationships.
 
In any particular place on the shore or seabed, a suite of species will occur, each adapted to the particular environmental conditions of that place, such as the conditions of anintertidal mudflat. Where such a suite of species occurs in other locations under similar environmental conditions, it can be defined as a community (or association or assemblage) of species which is occurring within a particular habitat type. The collective term biotope is now in common usage to encompass both of these biotic and abiotic elements.
 
Shore and seabed habitats are colonisedprimarily by seaweeds (on the shore and in shallow water) and by marine invertebrates from a wide range of phyla. Lichens (in the splash zone), higher plants (especially in saltmarshes) and fish contribute to a lesser degree. In contrast to terrestrial habitats, it is commonplace for marine habitats to be characterised, i.e. dominated, by animals rather than plants, and for the substratum to provide themain structure to the habitat (rather than plants such as in a forest).
 
Only a proportion of habitats have obvious dominant species (e.g. kelp forests, mussel beds, maerl beds). Many, particularly in deeper water, support a mosaic of species, none of which is particularly dominant, which may exhibit a degree of patchiness over the seashore or seabed and, in some cases, vary markedly with...