Foreshore

From Wikipedia, the free encyclopedia

The foreshore, also called the intertidal or littoral zone, is that part of a beach that is exposed by the low tides and submerged by high tides. This area can include many different types of habitats, including steep rocky cliffs, sandy beaches or vast mudflats. The area can be a narrow strip, as in Pacific islands that have only a narrow tidal range, or can include many meters of shoreline where shallow beach slope interacts with high tidal excursion.

[edit] Zonation

The intertidal region can be divided into several zones, primarily for classifying where organisms live.

At the very lowest level, the low intertidal merges into the shallow subtidal. This area is only exposed to the air during the lowest of low tides, and is primarily marine.

The mid intertidal is regularly exposed and submerged by average tides.

The high intertidal is only covered by the highest of the high tides, and spends much of its time as terrestrial habitat. This region merges into the swash zone, the region which is above the highest still-tide level, but which receives wave splash. On shores exposed to heavy wave action, the intertida zone will be influenced by waves, as the spray from breaking waves will extend the intertidal region above the high tide line.

Depending on the substratum and topography of the shore, different features may be noticed. On rocky shores, tide pools can be formed at low tide when water is trapped in hollows. Under certain conditions such as those at Morecambe Bay, quicksand can be formed.

[edit] Ecology

The intertidal region is an important model systems for the study of ecology, especially on wave-swept rocky shores. The region contains a high diversity of species, and the different zones caused by the physics of the tides causes species ranges to be compressed into very narrow bands. This makes it relatively simple to study species across their entire cross-shore range, something that can be extremely difficult in, for instance, terrestrial habitats that can stretch thousands of kilometers. Communities on wave-swept shores also have high turnover due to disturbance, so it is possible to watch ecological succession over years rather than decades.

Since the foreshore is alternately covered by the sea and exposed to the air, organisms living in this environment must have adaptions for both wet and dry conditions. Hazards include being smashed or carried away by rough waves, exposure to dangerously high temperatures, and desiccation. Typical inhabitants include sea anemones, barnacles, chitons, crabs, isopods, limpets, mussels, starfish, snails and whelks.

[edit] Legal issues

As with the dry sand part of a beach, legal and political disputes can arise over the ownership and use of the foreshore. One recent example is the New Zealand foreshore and seabed controversy. In legal discussions the foreshore is often referred to as the wet-sand area. For privately owned beaches in the United States, some states such as Massachusetts use the low water mark as the dividing line between the property of the State and that of the beach owner while others such as California use the high water mark. In the UK the foreshore is generally deemed to be owned by the Crown although there are notable exceptions especially what are termed several fisheries which can be historic deeds to title dating back to King John's time or earlier.