Calvin Jones Writing & Photography
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Writing -- Beach life

The following feature appears in Issue 3 of The Countryman Companion in April 2004 -- a quarterly collection of countryside related writing published by The Countryman, one of the world's oldest and most respected countryside magazines.

Beach Life
A typical sandy beach

One of the great things about living on an island is the incredible accessibility of our coastline. According to the Ordnance Survey Britain has a staggering 11,072 miles of it, and nobody lives more than 70 miles from the sea.

It is little wonder that so many of us harbour fond memories of the seaside and that visiting the beach is almost de-rigueur for some once the weather starts to improve. But while we are enjoying the sunshine and sea air, beneath our feet the beach's permanent residents are busy going about their lives. For them the beach is anything but relaxing!

Take a close look at a handful of sand and you will notice it is made up of many different types and sizes of particle. The main constituent of the sand around the coastline of the British Isles is silica fragments with some silt, clay and substances like shell fragments, diatoms and calcareous algae mixed in. The relative size and composition of the sand grains has a massive impact on the type, diversity and density of life that a beach can support.

Waves have a massive influence on the make-up of a beach as they pound against the shore. This wave action is the primary factor that determines the stability of the sand, the size of the grains deposited there, the beach's gradient, its drainage properties, its oxygen availability and its organic content.

In general the more exposed the beach the more pronounced the effects of the wave action, resulting in correspondingly coarser and less stable sand, a steeper gradient to the beach and less organic material - but that oversimplifies things. The consistency of the sand also varies both up and down a beach and along its length. Factors such as the wavelength and height of different wave types as they converge along the shore, the angle at which they strike, the shape and composition of the seabed and the influence of adjacent land-masses all have an impact on the make-up of a beach.

Add to this the twice-daily fluctuations introduced by the ebb and flow of every tide and three different groups of predators (land predators, like waders and other birds, that come in to feed when the tide is out; marine predators, like fish, that come in with the tide; and of course the constant threat of predators living in the sand itself) and you begin to see that life beside the seaside is no picnic.

Because the wind and waves are constantly shifting the surface layer of sand beaches offer scant purchase to would be colonisers. The surface layer of the beach is also exposed to extreme fluctuations in temperature, salinity and to the drying effects of the sun and the wind when the tide is out. The only really viable option is to burrow under the surface where conditions, while still difficult, are at least a little more stable.

A phenomenon known as capillary action draws water up into the tiny spaces between the grains of sand and serves to keep water levels under the beach significantly higher than sea level. Sheltered beaches in particular, with their smaller sand grains, tend to have better water-retaining properties than more exposed ones, and also contain more organic matter, a recipe that provides ideal conditions for a surprising array of life.

Plants generally do not like beaches. Rocks or large stones embedded in the sand can offer stable enough anchors for seaweed like the sea bootlace (Chorda filum) to take hold. This in turn offers a foothold for other species, like the epiphytic Litosiphon pusillus, which grows directly on the fronds of the larger algae. During very low tides on sheltered shores beds of eel-grass (Zostera marina) are sometimes exposed, while high on the beach terrestrial plants like the dune-forming marram grass (Ammophilia arenaria), the sand sedge (Carex arenaria) and the sea mayweed (Tripleurospermum maritimum) are found.

Out on the sand itself the constantly moving surface tends to keep larger plants at bay, and microscopic algae living in the water-filled spaces between the sand grains are the only marine plants to occupy the beach itself. Microscopic animals also inhabit these tiny pockets of water. They tend to be flattened or threadlike forms, and include some of the smallest known species from most invertebrate groups. These minuscule beach dwellers often exist in huge numbers, but go largely unnoticed because of their small size.

Around the strand line it is common to find sand hoppers like Talitrus saltator and Orchestia gammarella. If disturbed these small crustaceans propel themselves remarkable distances with an energetic flick of their specially adapted tails. Living so high on the shore these creatures are immersed in seawater relatively infrequently, and have therefore evolved a way of extracting oxygen from the air. They emerge from shallow burrows at night to scavenge among the rotting weed left behind by the tide.

Out on the open beach things look pretty barren at first, but closer inspection will usually reveal signs of a thriving community underfoot. Tiny tracks, holes or depressions in the sand, casts, water spurts and small protruding tubes all betray the presence of buried creatures.

Burrowing is practically compulsory here, and it is hardly surprising that worms figure prominently. On more sheltered shores the ragworm Nereis diversicolour is abundant from the mid-shore down. These fast moving, free-living worms are active hunters and use their strong, pincer-like jaws to catch and grip other worms, small crustaceans and just about anything else they can seize. They are sometimes seen crawling on the sand's surface, but usually burrow in search of their prey.

In contrast the lugworm (Arenicola marina), which is responsible for the familiar spaghetti-like casts on the lower shore, leads a relatively sedentary life. It is a sediment feeder that lives in a permanent "U" shaped burrow. The head end of the U is full of sand. When submerged the worm actively pumps water through the burrow from the tail end forward across its gills to replenish its oxygen supply. The water is forced through the sand at the head end of the burrow, which effectively serves as a filter and traps any food particles suspended in the water. The worm then ingests the sand and digests the edible matter before voiding the indigestible sand as a cast at the tail end of the burrow.

Several species of worm found on our shores build protective tubes to live in. A narrow tube of sand protruding from the beach on the lower shore and sporting a fringe of sandy branches is likely to be the home of the sand mason (Lanice conchilega). The fringe of branches serves to protect the delicate tentacles that the worm uses to collect food when submerged. Although you only ever see about 4cm of the tube sticking up out of the sand it can be anything up to 30cm long.

Molluscs - particularly bivalves - are also well represented on our sandy shores. Bivalves have two flattened shells (or valves) held together by a hinge-like ligament. The group includes familiar edible species like mussels, cockles, oysters and scallops. Burrowing bivalves use their powerful muscular foot to loosen the sand, anchor themselves and pull themselves below the surface.

They are predominantly filter feeders, and when buried under the sand need access to the seawater above both to feed and to replenish their oxygen supply. They do this by extending two tube-like siphons to the surface of the sand - one to draw water in (the inhalant siphon), and one to let water back out (the exhalant siphon).

The common cockle (Cerastoderma edule) is a burrowing bivalve that lives buried 2 to 3cm below the surface of the sand. It is often collected and, after filtering in clean seawater for a few hours, can be eaten. Another unmistakeable bivalve is the curved razorshell (Ensis ensis) which is forced to venture close to the surface of the sand to feed because of its short, fused siphon. The razorshell compensates for this forced proximity to the surface with a remarkable burrowing ability that allows it to disappear deep into the sand at the first sign of trouble. This speed-burrowing makes it difficult to unearth live specimens, but the presence of this unmistakeable bivalve is often betrayed by empty shells washed up on the beach.

Crustaceans of the sandy shore include the sand-hoppers already mentioned and sand-shrimps (Gammarus spp.) often found under stones low on the shore. Opposum shrimps, or mysids, like the ghost shrimp (Schistomysis spiritus), are small, transparent shrimp-like crustaceans found at the edge of the sea or in pools left behind by the receding tide. The edible shrimp (Crangon crangon), is also found here, where it lies buried in the sand by day with only the tips of its antennae visible.

The shore crab (Carcinus maenas) is the most widespread crab on any British shore, including the beach. When the tide is out it burrows under the sand, emerging once submerged to scavenge for carrion, although it will take live prey if the opportunity presents itself. Lacking the protective carapace of its more familiar relative the common hermit crab (Pagurus bernhardus) takes up residence in an empty mollusc shell for protection, moving into progressively larger accommodation as it grows. Sometimes found on the sand of the lower shore or in sandy pools it is frequently joined in its shell by the small ragworm Nereis fucata, while both the anemone Calliactis parasitica and the hydroid Hydractinea echinata sometimes hitch a free ride on the outside of the shell. Crabs are messy eaters and these hitch-hikers benefit from scraps of food whenever the crab feeds.

A slight imprint in the sand close to low water may betray the presence of the sand star or burrowing starfish (Astropecten irregularis), which lives buried just below the surface. It feeds on worms, bivalves and crabs, swallowing them whole and ejecting the indigestible parts some time later. Another echinoderm, the sand brittlestar is easily recognised with its distinct central disc and five long arms. It leaves a mark like a birds foot on the surface of the sand where it lies buried just below the surface low on the shore. Sea urchins are also represented here: heart urchins are heart shaped with soft, backward-pointing spines in place of the erect, rigid spines of their rocky-shore counterparts. They live buried up to 10cm deep in the sand of the lower shore.

Sea anemones are perhaps among the last creatures you would expect to find buried in the sand but there are some burrowing species, two of which, Peachia hastata and Halcampa chrysanthellum, occasionally occur at low water on very sheltered shores.

As well as providing a permanent home for residents, beaches are an important resource for visiting species as well. They offer sheltered, food rich nursery grounds for many flatfish species, including plaice (Pleuronectes platessa), flounder (Platichthys flesus) and sole (Solea solea). Small flatfish are common near the waters edge and in sandy pools.

Wading birds take advantage of the wealth of invertebrate life on offer and regularly fly in to feed on the rich pickings. Along with estuarine mudflats British beaches form a vital network of feeding grounds for many migratory bird species.

Rocky shore animals like the edible mussel (Mytilus edulis) and the acorn barnacle (Semibalanus balanoides) often blanket rocks on the periphery of sandy shores, and familiar seaweed like wracks (Fucus spp.) and kelps (Laminaria spp.) quickly take hold wherever conditions are suitable. These colonisers in turn attract other species to settle and it is not uncommon to find thriving rocky shore communities alongside, and occasionally right in the middle of a sandy beach.

While beaches may not immediately spring to mind when we think of coastal wildlife they are far from the barren expanses of sand they can at first appear. So the next time you are sitting on a beach and grow weary of basking in the oh-so-fickle British sunshine, get up and explore… you might be surprised by what you find.

All text and images copyright © 2004, Calvin Jones, all rights reserved.