The wonder of rockpools by author Adam Nicolson
After making three small rock pools in the intertidal zone of a small bay in the Sound of Mull just to ‘see what happened’, writer Adam Nicolson was amazed by the life which colonised his new habitats
After I had been given permission by the people at Crown Estate Scotland, which owns about half of the foreshore of Scotland, I set about making three small rock pools in the intertidal zone of a small bay on the Sound of Mull. ‘What for?’ everyone asked, as I laboured with my pickaxe and wrecking bars, or transported the bags of special nontoxic concrete to the sites around the perimeter of a large bay.
At the most basic level, the idea was to see what would happen. In a place whose geology meant that no proper rock pools ever formed, how would the life of the sea react to these three new pools? Each would be at the beginning quite naked, exactly as the words say – a rock pool, a dish of rock on the shoreline, as if it were part of the earth before life had come to clothe it. And then, slowly, the sea would bring life to that dish, to make it a living thing. The pools would be an invitation to life, an act, as I learned to call it, of bio-receptivity, even bioreciprocity, an enrichment of the habitat, not a subtraction from it.
And so, more than a long two years ago, I began, each pool different: the first dug into the Jurassic layers high up the shore at the head of the bay; the second made by damming the exit from a hollow about the size of small swimming pool, which once blocked would hold the tide; the third made by building a circular concrete wall far down the tide, only exposed to the air at the lowest of low waters.
After the first pool filled, nothing happened for a day or two. This was early in the spring of 2019, and the shore seemed almost lifeless. Then one night in a full moon, when the tide was low, I went down with a torch to look and there, among the rocks that had not seen a living creature for the last 200 million years, was a fleet of little glass prawns, Palaemon elegans, scooting about like aerial taxis in a universe scarcely deeper than themselves.
The great American biologist Stephen Jay Gould once wrote that, “Hardly a natural historian has failed to locate his chief delight in the lovely puzzles… of actual organisms in real places”. These prawns became the first of my lovely puzzles, and for days I tried to unravel their nature, reading as much about them as I could.
It is a curious thing that, until you know to look for something, it is difficult to see it. You only see what you have learned to see. And so now, slowly unravelling the lovely puzzles, I saw how the big (almost certainly female) prawns hung hidden in the best of protected places, dominant and powerful, while the others (probably male) restlessly searched the pool for food; how they hurled themselves into the darkest corners if any sudden movement even of a shadow was made.
Most of their lives they manoeuvre through the pool with the little swimmerets beneath their body, but that sudden escape is made with a rapid thrash of their tail muscle, something which biologists have patiently discovered is provided with its own high-voltage response nerves, jackknifing it away from danger. And the move is dazzlingly fast: from five to 15-thousandths of a second elapsing between the stimulus being given and the big abdominal muscles contracting into the escape flex.
That change of scale and focus is what coloured the whole experience of looking very, very closely at the pools. They turned into microoceans, full of their own microdramas, micro-tussles and microcatastrophes. Winkles appeared in the first pool and then in the second some huge green shore crabs, the big russet-jointed males holding in their arms (the biologists call it the ‘pre-copulatory embrace’) the little females, kept there until the female softens, ready to shed her shell, and in that soft condition is manoeuvred carefully under the male to allow them to mate. I would never have imagined a crab capable of such delicacy until I had witnessed these careful amatory operations.
But these pools are no gardens of pre-lapsarian bliss. I collected some very common beadlet sea anemones from the second pool, they can be carefully peeled away from the rocks without harm, and placed them in my table-top aquarium without realising that I had gathered two different clones, one with a blue foot, one with a red foot. To my horror I watched as a red foot, confronted with this unexpected neighbour, suddenly raised itself to double its normal height, exposing its crown of pale poison cells, the acrorhagi, and plunged them down into the body of the blue foot, which, desperately wounded, detached itself from the rock and allowed itself to be floated away in the currents of the aquarium filter. After blue foot had floated away, red foot bent over and carefully deposited on the site blue foot had vacated one of its own tiny tentaclewaving clones, its territory expanded, its world enlarged.
The third pool was the best, almost at the bottom of the intertidal zone, just above the first of the kelp. I finished its wall in the winter and very early spring of last year, then left it for months in the first lockdown, like a pie slowly cooking in a very watery oven. I only got back there on a perfect summer’s morning, the tide slipping easily out across the weeds of the upper shore.
Already, multiple life forms had taken up residence in it and over the weeks of the summer I made a map of what was there. It varied all the time. The weeds, the sponges, the limpets and tiny, newly seeded barnacles were all fixed and remained constant but other animal life came in on one tide and left on the next. Sometimes the pool was nearly bereft of creatures; at others it met me with spectacular surprises. I arrived one
They turned into microoceans, full of their own micro-dramas, microtussles and microcatastrophes
day to find a starfish sprawled in the one-foot depths of the central channel, its arms looking as sugarcrusty as an Eccles cake, covered in the tiny self-cleaning organs, the pedicellariae, with which it picks away any weed or creature that tries to colonise its surface. Then, on one unforgettable day, the common sea star spread its 12 pink and white tuftencrusted limbs across the sunlit edges of the shallows, as brilliant as if it were newly made, just as careful as its cousin in cleaning its own body, so that it looked more like a dish of strawberries and cream that had arrived from Mars than a thing of the Scottish seas, or a coral reef steadily on the move, as huge and deliberate as the giant tracked vehicles that transport rockets to the launch pad at Cape Canaveral, a bi-colour garden, the prettiest of dresses, a tooth-brush from paradise, a radiant morning gleaming in the shallows. It was there for one tide only and never returned.
I had never felt so happy at having made something, perhaps because I hadn’t made this at all. The pool, like the others, was making itself, a selfcreating fragment, a self-enriching thing, and in that way a model of the growth of life itself. In the world at large, a huge diminution is underway. In the seas and on the shores around Scotland damage has been done and will continue to be done. But here, in the smallest of gestures, something was perhaps turning the other way.