In a coastal space never permanently covered by saltwater but repeatedly splashed by waves, salinity is a key abiotic factor in the supralittoral zone. Depending on wave activity and the amount of splashing, supralittoral zones can be exposed to different amounts of saltwater, resulting in different amounts of salinity in the soil or sand. Of course, high concentrations of salt can discourage even the sparse vegetable cover characteristic of the supralittoral zone, while lower salinity levels can allow more plant species to take root in the area.
All supralittoral zones tend to have relatively high levels of humidity and soil moisture, as could be expected in a coastal zone. Supralittoral zones in areas with low seasonal tides and calmer surf, however, can be exposed to less water and have less soil moisture, keeping species like barnacles that need high levels of moisture from taking hold in the area. Naturally, high levels of moisture tend to promote the various species of amphibian and crustaceans that thrive under such conditions.
Temperature is a significant abiotic factor in most ecosystems and the supralittoral zone is no exception. As with other ecosystems, temperature determines the kinds of plants and animals that can survive in the average temperature ranges. Low temperatures, for instance, favor organisms that thrive in cold conditions while high temperatures advantage the development of species adapted to heat. In the case of the supralittoral zone, moreover, temperature is determined both by air and water temperature, both factors making up the thermal conditions of the ecosystem to which organisms are exposed.
In the supralittoral zone, geology and climate combine to make up unique physical conditions in the area. Given the highly chaotic nature of an ecosystem where conditions consistently change -- from daily tides to seasonal storm surges -- the abiotic physical parameters of the ecosystem like the strength of tides or the presence of wind and rain play an important role in determining what life thrives in the area and under what conditions. A shallow bay, for instance, is likely to have faster storm surges and tides, just as climate conditions like the occurrence of tropical storms have a significant impact on water and wind currents. The combination of these forces shapes the physical parameters in the supralittoral zone to which life must adapt.