| Habitat factor |
Range of conditions |
| Salinity |
Full, Variable, Reduced / low Salinity in pools and
crevices in the littoral zone can vary considerably with evaporation and dilution by rain.
|
| Wave exposure |
Sheltered, Very sheltered, Extremely sheltered The
structure of ecological communities on rocky shores is affected by a horizontal gradient
of exposure to wave action, from sheltered bays to exposed headlands. The degree of wave
action on a particular shore is determined by the aspect of prevailing winds coupled with
the ‘fetch’: the distance over which winds blow. Exposure to wave action affects
the distribution of species, according to their tolerances. With decreasing exposure the
risk of dislodgement and physical damage decreases, resulting in a greater preponderance
of fragile species. Morphological differences can be observed between members of the same
species from wave-exposed and sheltered sites. For example, dogwhelks from wave-exposed
shores have thinner shells with larger apertures than those from sheltered shores. |
| Substratum |
Bedrock; boulders; cobbles; pebbles; mixed substrata on sand
and mud. Hard rocks provide a more secure anchorage for large plants and animals such as
fucoids and limpets. Sheltered rocky shores can consist mainly of bedrock or they may be a
mixture of bedrock and boulders, cobbles or pebbles intermixed with sediment.. |
| Height band |
Strandline, Upper shore, Mid shore, Lower shore |
| Zone |
Eulittoral |
| Temperature |
At the interface between land and water, species spend part
of their time immersed in the sea and part of their time in contact with the air, with a
vertical gradient of emersion up the shore. Air temperatures commonly fluctuate by 10 to
20oC in a 24-hour period whereas sea temperatures usually fluctuate by less
than 10oC in a year. Intertidal areas are also exposed to the rigors of
sunlight at low water especially when low water spring tides occur around midday. |
| Tidal range |
Tidal ranges from 0.5 m to 12 m in the British Isles. Greater
tidal ranges result in more extensive littoral zones. |
| Desiccation |
In temperate zones, the risk of desiccation due to heat and
low humidity is highly significant. The ability of species to tolerate desiccation will
effect community structure, as will wave exposure, which can modify the extent of the
vertical gradient. The elevation in the zonation pattern observed on exposed shores will
not be found on sheltered shores, as ‘wave splash’ will be minimum. |
| Slope/shore topography |
Rock type influences the slope and topographical complexity
of the shore, and slope determines the area available for littoral species. Barnacles and
limpets are successful on steep shores, while mussels and seaweeds are more common on
gently- sloping or horizontal shores. |
