In each of these biotope complexes, a particular set of environmental (physico-chemical) conditions create the biological communities on which, in turn, are dependent populations of predators. The dominant factors, termed the ‘environmental master factors’, can be summarised as: temperature, light, salinity, situation (including stability, exposure to air and desiccation and, by extension, depth regime), oxygen content, nutrients, currents (wind-driven, freshwater-driven and residual) and tides, and the nature of the bottom substratum (formation type adapted from Jones, 1950 and Erwin, 1983).

Each of these environmental master factors is important in providing the conditions and niches within which the biota can develop. The primary physical features of the hydrographic regime (tides, waves, residual currents) together with the underlying physiography and geology will create the conditions for a given type of substratum to develop. Once the sediment type has been established, it will create conditions for colonisation by organisms. If the integrity and health of the sediment is maintained then the biological colonisation will also be created and maintained. Hence it is highly important to have a good understanding of the environmental and other physical features in order to understand and interpret the features of the biota.

This chapter summarises the nature of the physical environment in which these biotope complexes exist and outlines the common and distinctive environmental attributes which are important in defining the characteristic features of that biotope complex. The sensitivity aspects of the gross physical determinants of climate, temperature and salinity are discussed elsewhere. The importance of climate and temperature regimes dictates the biogeographic zones (see Hiscock, 1998a) and has been used to determine large scale separation of assemblages (e.g. Glemarec, 1973). The more variable parameter freshwater inputs both within estuaries and over intertidal areas will create zonation.

Spatial Extent

Hydrophysical Regime

Vertical Elevation

Substratum

References