All shores are influenced by the twice daily tidal cycle. Extreme low
and high tides occur around the spring and autumn equinoxes.
The seashore
divides into a series of horizontal zones with different plants and animals
living there depending on the length of time each area is left uncovered. Zonation is best observed on a rocky shore.
Oarweeds or kelp grow in shallow waters offshore. Look for eiders feeding on
mussel beds.
Look for plants such as sea pink, moss campion, scurvy grass, sea mayweed
and lichens on the rocky foreshore. Shetland wrens often creep mouse-like
amongst the rocks.
The lower shore is only uncovered on low spring tides. Look for delicate
organisms which cannot withstand prolonged exposure such as scale worms, sea
spiders, starfish, brittlestars, seasquirts and sponges. Shallow water fish
such as butterfish and five-bearded rockling shelter under stones.
Most colonies of seabirds breed on sandstone sea cliffs which weather into a
series of suitable nesting ledges and crevices. These are occupied by
fulmars, ganntes, puffins, guillemots, razorbills, kittiwakes and shags.
Ravens and hooded crows also nest here. Safe from grazing animals and
enriched by salt spray and guano many cliffs have 'hanging gardens' which
may include sea pink, roseroot, sea campion and moss campion.
Most of the permanent inhabitants of a sandy beach, such as bivalve
molluscs, lugworms and ragworms, live buried beneath the sand. Look for the
shells of common species such as cockles, trough shells, sand gapers, carpet
shells, razor shells, striped venus and thin tellins.
Rock pools may contain small jellyfish, sea anemonies, hermit crabs, sea
urchins and sea slugs, Use a clear-bottomed container for viewing the
inhabitants.
Shingle beaches are the most barren of all shorelines - the continually
moving pebbles prevent colonisation by plants or animals.
The strand line accumulates cast-up seaweeds and other debris which harbour
tiny crustaceans and kelp-fly larvae and is a favourite hunting ground for
birds such as the turnstone, rock pipit and starling.
Only a few species such as the small periwinkle and the sea slater can
survive on the upper shore, the area above the average high tide level.
Shingle ridges above the average high tide level accumulate organic matter
and are colonised by plants such as orache, sea sandwort, sea campion,
silverweed, sea mayweed and goose grass. A rare species found at a few sites
is the purple-flowered oysterplant.
The middle shore, the area between the high and low tide levels, is exposed
and submerged regularly and is dominated by the brown seaweeds known as
wracks. Species such as shore crab, periwinkles, dog whelks, barnacles,
limpets, sea anemonies and edible mussels are adapted to survive in this
changing environment. When the tide recedes they avoid predation and drying
out by retreating beneath stones and seaweed, remaining in rock pools or
clamping tight to the rocks.Look for a black encrustation on the rocks - not oil but a black lichen, Verrucaria maura.
Turn over small rocks and stones to expose seashore life. Many attach
themselves to the underside of the rock as well as sheltering beneath.
