Starfish enterprise
In our coastal waters life is ruled by the moon rather than the sun. Julian Hector goes in search of a brittlestar.
There is nothing quite like messing about on the low shore of an ebbing spring tide. Definitely a clumsy giant to a world occupied by life much more suited to the slippery terrain. And the joy of turning over a rock and finding something alive and slithery!
This is a world dominated by the lunar cycle. A tidal rhythm of ebb and floe that brings with it change every six hours. It's at low tide especially when the life which lurks, slithers, swims, creeps and walks can be exposed to dehydrating temperatures, battered by wave surge, stressed by too much or too little salt. And it is in this transient terrestrial world that hunters are also the hunted, it's dog-eat-dog.
A harsh environment
Yes, the inter-tidal zone is one of the harshest natural environments on earth. Limpets and barnacles are locked down tight on the rocks to protect their delicate body from desiccation. Top shells, winkles and whelks drift towards the shady surfaces of the rocks. Crabs and fish cower in the shallow pools and in the cool dark thicket under the weed, out of sight. But their reward for tolerating this physiological roller coaster ride is to get a twice-daily replenishment of food, light, water and oxygen. They win the elixir of life.
Limestone rocks, south and westerly location - the Gower is a Mecca for marine wildlife
Oxwich Bay on the Gower Peninsular of Wales is a large moon-shaped beach of golden sand fringed on each side with a rugged limestone rocky shore. Being westerly and of limestone and relatively sheltered makes Oxwich a Mecca for wildlife. And at low tide the wave eroded and animal encrusted rocks, atopped with locks of green, red and brown seaweeds are exposed. This was my destination, together with a marine naturalist to make a radio programme about starfish.
Ancient foragers
The scene in front of me triggered my ancestral memory. One hundred thousand years ago our likely ancestors were foraging on the low shore of Klaus's river mouth in South Africa. The archaeological evidence is there. Relic middens of food waste from hunter gathering on the shore: the shells of turban shells, top shells, whelks, mussels and winkles together with stone tools.
These piles of discarded shells are evidence of the productivity of the low shore and shows that the wildlife of low tide provided those early people with their protein for hundreds of years. At Oxwich Bay, on that day in April, silhouetted by the sunlight, people manoeuvred expertly between and over the rocks. Foraging I wondered? Their gaze was down and with intent and each with a bucket.
Some of the Asterias were monstrous in size with arms as fat as an ice cream cone.
As we approached the rocks from the sandy bay, orange-topped five-armed starfish were abundant. Asterias rubens is the common star fish and the one we're all most familiar with. Some individuals could fit in the palm of my hand, others about the size of my hand. And the odd monster, with arms fatter than an ice cream cone and lines of conspicuous writhing suckers on the underside. But much as we'd like to talk about the common starfish, it was others of the two hundred or so species that inhabit north Atlantic waters we wanted to find. And to do that we had to peep under rocks.
In search of a brittlestar
One rock, ten rocks, forty rocks. Thirty minutes, one hour later. Wet feet, wet trousers, fingers torn on the rocks and blooded. The joy of gently lifting rocks and placing them down again was ebbing as fast as the tide was now flowing. We failed to turn up starfish. There were other things though; the odd rock goby, a butter fish - so slippery! - velvet swimming crabs leaning back on their haunches and snapping their claws violently in the air. And there were many small edible crabs, but no starfish. We were looking for brittlestars whose tentacle like arms can move sinuously because they are controlled by muscles, not hydraulics as in the tube feet of Asterias.
As the tide began to floe so the rocks we were looking under began to sit in water. The rock pools became a continuum with the sea and the seaweed swished back and forth with the surge. It was soon to be out of bounds to us.
Rocked pools
We don't eat brittle stars so perhaps they were collateral damage
Julian Hector
My guide muttered the words "the stones have been turned too much", he was disappointed there were fewer starfish species than normal. "The bio-diversity has gone". He was surprised and exasperated. The other beach goers with their lurid coloured buckets wandered past us ahead of the tide. Their buckets had soft-shelled crabs in them, crabs in the process of growing a new shell having released their old one ahead of a growth spurt. These shellfish were destined for shops and restaurants for a national, even global market.
We don't eat brittlestars so perhaps they were collateral damage as their rock hideaway was turned over in search of crabs. Or they have just got out so they don't die out, one of the fundamental rules of ecology.
I wonder what else followed them.
Listen to The Living World: Starfish broadcast Sunday 7 June 2009, Radio 4.
Published 5 June 2009
Julian Hector
