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The Seashore

Rocky Shore Trail
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The upper shore (exposed shores)

upper and middle shore of an exposed shore

A view of the upper and middle shore of an exposed shore (B.E.S.3). Note the dark patches of Lichina pygmaea and the white barnacles.

For our purposes we are taking this zone as the bit of the shore between the highest tides (extreme high water spring tides (EHWS)) and the mean height of neap tides (MHWN). Do remember that we are using these heights as a convenience, the organisms on the shore may not understand this. They may therefore have the temerity to survive where we say they shouldn't.


Lichens are still much in evidence on the upper shore. They are a symbiotic association between a fungus and an alga. The fungus possesses thick cell walls to reduce water loss and can store water (up to 3 times its own weight) as well as food produced by the algae. Lichens can be thought of as terrestrial organisms that are tolerating being immersed in seawater. Fewer kinds of lichen survive on the upper shore than in the splash zone. The most obvious is the black tar lichen (Verrucaria maura) which occurs as a distinctive black band along the top of the shore. People who have not visited Dale Fort or this web-site have been known to mistake it for black oil. In truth it does not look like most peoples conception of a living organism, people are often astonished to find out that it's a living thing. Seaweeds find the drier, brighter, wave exposed environment very difficult to cope with and you will find few, if any of them on the upper parts of exposed shores. Large surface areas will be a no-no if you want to stay attached to the rock. Instead of seaweed look out for another lichen: Lichina pygmaea is a bit weird and looks like a fine, fuzzy mat found in small patches amongst the barnacles. Amongst the Lichina you can find a small community of very small organisms like the pseudo-scorpion and a bivalve, Lasaea.

Marine animals that can cope with desiccation and wave action begin to appear on the upper shore. Rough and small periwinkles (Littorina saxatilis agg. and Melarhaphe neritoides) are small snails that graze on the algae and lichens. They avoid drying out by having shells and by numerous other ingenious means. Barnacles are shelled crustaceans (like lobsters and crabs) which filter their food from the water and are found in this zone. On very exposed shores with more or less continuous splash and spray some species of barnacles can survive high up in the upper shore. Animals in this zone have to be able to withstand desiccation and most of them do this most obviously by possession of a shell. There are lots of other interesting ways of coping with the stresses of this zone that you can find out about by clicking on the hyperlinks.

Compare this zone (upper shore) with one on sheltered shores.

Table of Zones - click to go


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