Fig. 4

Schematic representation of how abiotic stresses change along the elevational gradient present at sedimentary shores for species of aquatic and terrestrial origin (see also Bertness 2007). Because of tidal curves (spring tidal amplitude schematised by solid line; neap tide by dashed line), the inundation period and frequency vary along the elevational gradient. Combined with the requirements for species with a more aquatic or terrestrial physiology, stresses differ along the elevational gradient (see numbers 1, 2 and 3). Habitat modification by ecosystem engineers may mitigate the stresses occurring along these gradients (e.g. by attenuating hydrodynamic energy from waves; Bruno 2000). In areas where abiotic stresses become smaller, biotic stresses will increase in importance (Bertness 2007)