Strandline - secrets of the seashore
The seashore strandline forms at the top of the beach. It is made up of natural and man-made objects cast up by the waves and left behind by the receding tide.The strandline can tell us many things about life off the Sussex coast. It can provide clues to the animals that live there, what they look like, the type of eggs they lay and sometimes even how they died. Marine and land animals may scavenge on the strandline, and the decaying debris blown up the beach may eventually become soil to support shingle plants.
Top ten strandline objects
The cuttlefish is a relative of both the octopus and the garden snail. The cuttlefish bone, one of the most familiar strandline objects is infact an internal shell. The bone is made up of tiny chambers which can be filled with a mixture of gas and water so that the cuttlefish remains buoyant. Cuttlefish die after mating; only living 1-2 years, which is why so many 'cuttlefish bones' are found on the beach. These may be eaten by scavengers such as carrion crow.
Dogfish egg case
Dogfish eggs cases can be identified by the tendrils at each corner. These tendrils are used to attach the egg cases to seaweeds or similar objects. Many fish lay thousands of eggs in the hope that a few will survive to maturity. While dogfish only lay about 22 eggs, the baby dogfish will grow protected inside the case for 9 months before they hatch. The new hatched dogfish measure about 10 cm .
Common whelk shells are one of the largest gastropod (snail-like) shells found on the strandline which may reach 110 mm in height. These whelks are part scavenger part carnivorous. They sometimes attack bivalve molluscs by using the edge of their shell to force open the two halves of the bivalve's shell. A broken whelk shell reveals how the animal's body fits within the curled chamber.
Although the sea-mat called hornwrack resembles dried seaweed it is actually a bryozoan colony of tiny animals called zooids. The zooid resembles a tiny sea anemone each living within tiny rectangular compartments on the hornwrack. Zooids have tentacles that are covered in hairs which pull microscopic creatures into their mouth. The colony can grow up to 200 mm in height, but is usually smaller.
Whelk egg cases are also commonly found on the strandline. The egg mass is made up of many smaller capsules with over 1000 eggs. Only a small percentage will hatch, the others will become food for the hatchlings. Large masses are often the result of 2 or more females. Whelk egg mass is also known as 'sea wash balls' because early sailors used them for washing.
Sponges may be round, flat or upright with slender branches like this variety. Sponges are filter feeding animals. Hair-like structures inside the sponge create a water current which draws water, plankton and particles of food into the body through small openings. The water then flows out the larger, more visible holes. This sponge grows attached to solid objects and can reach 30 cm tall.
Spider crab shell
One of the largest crab shells found on the strandline comes from the spider crab. The crab may have been attached and eaten by a predator or cast off its shell as a natural part of growing. As a defence against predators, spider crabs decorate their spiny shells with seaweed and other debris to blend in with their surroundings. This shell-like part of a crab's armour is called the carapace.
The inhabitants of most sea shells usually crawl, burrow in sand or stick themselves to rocks. Surprisingly, the scallop can actually swim to escape predators, such as starfish, by rapidly opening and closing their shells. The rest of the time they lie in a depression in the sand. Scallops are fished commercially around Britain.
Oysters were once of great commercial importance to Sussex until they were over-fished back in Victorian times. Young oysters settle on the seabed and attach themselves to the substrate by secreting cement produced by the byssus gland at the base of the foot. This cements the left hand shell valve to the substrate. Oysters filter tiny particles of food from the water.
Slipper limpets feed on tiny particles of food in the water. They often live in chains, females at the bottom and smaller males at the top. If the females die, the next male will change sex. Although the slipper limpet is now one of the most common shells on the strandline it originally came from North America. When the native oyster was over-fished in Victorian times, stocks were replenished from North America and the slipper limpet came with them as a hitch hiker.
Shingle plants can survive the harsh conditions of an exposed coastline because of special adaptations. These include waxy leaves that prevent moisture loss due to the drying effects of sun and wind. These also protect them against the salty sea spray. Many have a long tap root to reach freshwater deep beneath the shingle and can survive on the infertile soil trapped between the stones. Woody stems help prevent damage by the shingle. On exposed beaches specimens of some plants avoid the elements by staying small. Others grow as a carpet over the shingle.
The attractive Vipers Bugloss flowers between June and September. It thrives on dry grassland, chalk and roadsides as well on shingle beaches.
Stone crop is a mat forming succulent plant that can store water in its fleshy leaves. It can be found growing on shingle, chalk and stone walls.
Houndstongue is named because the leaves resemble a hound's outstretched tongue. It has spiky seed heads that attach to animal's fur and human clothing helping their dispersal.
Yellow Horned Poppy
The horn-shaped seed pods give the Yellow horned poppy its name. It bears bright yellow flowers from June to October
Sea Kale, also known as sea cabbage is one of the largest shingle plants. Sea Kale was once prized as a vegetable and is still cultivated today.
Sea Pea is one of the more rare shingle plants. It grown near the ground and can form large mats.
Gorse Valerian Kale
Gorse Valerian Kale is one of the first 'pioneer' colonisers of a shingle beach. Gorse and Red Valerian grow on the upper reaches of the shore.
Woody Nightshade is common in hedgerows, where it climbs other plants, on shingle beaches it grows low to the ground. Flowers in June to September, followed by red 'poisonous' berries.
Teasel grows on roadsides, wasteland and at the top of shingle beaches. It is best known for its distinctive spiky flower heads.
In nature nothing is wasted, not even the dead and decaying remains of seaweeds and sea animals such as fish, crabs and starfish. Gulls are natural scavengers (like the vulture of Africa): they have an important role to play in cleaning up animal remains.
There is also an army of smaller animals that continue the cleaning process, crabs, tiny crustaceans and even beach flies and bacteria that finish the job. Land animals also scavenge on these animal remains. Carrion crow, pigeons, foxes, mice and rats also scavenge on this debris.
Sussex beaches are mostly shingle with varying amounts of sand uncovered by the tide. Sand and shingle are made of eroded rocky cliffs and broken seashells.
The coastline of east Sussex is largely chalky cliffs created millions of years ago when Sussex was underneath the sea. Not far beneath the sand and shingle is a large platform of chalk that continues out to sea, exposed in places forming chalk reefs.