Shorelines are exposed to the effects of oil more than any other part of the marine environment. However, much of the flora and fauna on the shore are inherently resilient, since they must be able to tolerate the tidal cycle as well as periodic exposure to pounding waves, drying winds, extremes of temperature, variations in salinity through rainfall and other severe stresses. This tolerance also gives manyshoreline organisms the ability to withstand and recover from spill effects. Rocky and sandy shores
Exposure to the scouring effects of wave action and tidal currents means that rocky and sandy shores are the most resilient to the effects of a spill (Figure 7). This scouring also usually enables natural and rapid self cleaning to take place. A typical example of an impact on rocky shores in temperate climates is the temporary loss of the common limpet (Patella vulgata), a keystone species of marine snail. ’Keystone’ species are plants or animals that exert a controlling influence on the ecosystem that is disproportionate to their biomass, and their removal is likely to lead to a dramatic change to that ecosystem. Limpets grazing on micro-algae on rock surfaces limit algal growth and settlement of other fauna. Their loss typically leads to a rapid growth of opportunistic green algae (Figure 7 inset). Over time this algal growth is displaced by other algal species and as space becomes available for limpets to re-colonise the rock surface, the ecological balance is gradually restored. On tropical and sub-tropical sandy shores, ghost crabs (Ocypode sp.) occupy a similar environmental niche as limpets and high mortality rates are a common feature of shoreline oiling. Despite this, within weeks of shorelines becoming clean, the crabs often re-colonise the