Marine predators never fail to recognise food, no matter how it's packaged, whether finned or footed, shelled or slimy. The female herring lays a million eggs to ensure that at least two survive to maturity and keep the species going. Almost every organism is destined to be devoured. Such deaths are the currency of life.
At first, Jack [biologist and diving pioneer, Professor Jack Kitching OBE] and John [his colleague, Dr John Ebling] believed that the distribution of marine creatures was explicable in terms of factors such as tides and waves, but gradually they changed their minds, and it was this that was to make their work famous.
They began to realise that interactions between the organisms themselves were at the heart of what was happening, and that certain key predators or competitors exercised an overwhelmingly important influence over the entire community. Their research switched to a search for such key organisms.
Long before I came to the lough they noticed that the common mussel was abundant only on the most surf-battered shores and in the calmest corners of the lough. Surely it could inhabit many of the sites in between - so why wasn't it there? To find out, they transplanted mussels to intermediate shores and, within two days, they had been consumed by marauding crabs and starfish. For the first time, the team fully appreciated the difference between what distribution was possible and what was permitted by other creatures.
The sea slithers with fearsome predators. Once a mussel is embraced by a starfish, it is lost. Starfish use hydraulics instead of muscles, and in a tug of war they never tire. They can drag open any shell and, as soon as it gapes, the starfish throws out its stomach like a white shroud and dissolves the victim alive in acid. If a starfish wanders into a pool, the resident urchins soon "smell" it and stampede to the other end, for they know what is in store. I rest my hand in the pool and the starfish folds itself around me. It senses I am meat.
The shore is the home of quiet murders. Sea anemones only masquerade as harmless flowers. Each tentacle is laden with ten thousand hypodermics loaded with poison waiting to paralyse the unwary. The tentacles of the snakelocks anemone stick to my finger, held by its barbs, but unable to breach the skin. There is safety in size. If we were small, the shore would be a terrifying place and our first seaside holiday would be our last.
Several projects confirmed the importance of predators. On the exposed coast at Carrigathorna, for example, the shells of the dog whelk were thin-walled and wide-"mouthed", whereas in sheltered sites they were sturdy with small "mouths". A "nutcracker" device showed that the sheltered shore types were more than twice as difficult to smash. This seemed to me the wrong way round, surely they needed to be tougher where the surf would pound them. Not so, for even the more delicate form could withstand an occasional tumble around the rocks when dislodged by waves, and the large aperture of the shell allowed it to have a larger "foot" to fix securely to the substratum. When the small- mouthed forms were transplanted to Carrigathorna most were lost within a week. But why were the sheltered water inhabitants so heavily armoured? It was because crabs, which shun surf-washed shores because they would be washed away, grew big in calmer sites and, although easily capable of smashing the flimsier-shelled whelks, they had a hard time with the tougher ones. Even so, the whelks sometimes retreated up the shore to risk death from desiccation or rain rather than be eaten alive. Again, predators were calling the shots.
The work at Lough Ine became a hunt for other examples of biological control. By manipulating nature - adding or subtracting predators or competitors and following the repercussions - they were able to identify those key species that controlled the success or failure of the others. Organisms were moved to areas of greater or lesser risk. The number of predators or grazers was adjusted by hand or excluded with cages (although at night, mischievous otters sometimes unscrewed the lids and stole the contents). Jack and John discovered not just who was eating what, but also how big a predator needed to be to devour prey of various sizes. Small juvenile animals were more vulnerable, but might evade capture beneath the adults or in the hidden corners of the habitat. Most important of all, they revealed that a cascade of consequences followed from changes in the abundance of a single species.
Long ago it had been observed that if the leg of a dead frog was stimulated with an electric current, the muscle contracted, and this provided a way to study how muscles work. What Jack and John developed was a means to goad living communities into revealing how they operated. Their pioneering approach showed that ecological experiments could be carried out in the sea. An entirely new natural laboratory had been discovered, one that avoided the artificiality of laboratory-bound experiments, which were the mainstay of the rest of biology. Their first publications on the predation of mussels (in 1959) and the importance of urchin grazing (in 1961) had ushered marine ecology into the experimental age and their techniques allowed ecologists worldwide to use shoredwelling organisms as test beds for ecological theories of how communities developed and were maintained.
Identifying the most influential species was also vital if we were to predict what would happen to coastal communities should the oceans warm, or an oil spill kill off the limpets, or a new sewage outfall coat the rocks with silt.
Thanks to my studies at Lough Ine, I too now embraced the significance of biological interactions between organisms and learned how to unravel them. I became a workman who had found his tools, and my PhD thesis would reflect this change in approach; the first half was about the distribution patterns of Saccorhiza in relation to factors such as temperature, light and water flow, but I decided that for the remainder I would examine the most important creatures that lived on or around the plant and how they could overwhelm or exclude it. I had begun my explorations on the effects of competition, and how grazers select their food, something that would last me a lifetime.
The most important grazer in the lough was the purple sea urchin. This is a Mediterranean species that reaches its northern limit in Ireland. On the soft limestone shores of the west coast it lives in flask-shaped depressions in the rock. It crawls in when young and gradually enlarges the "flask" without widening the mouth, so that pretty soon it is trapped and, unable to browse, has to rely on scraps of seaweed drifting in and getting caught on its spines. Here in the lough it just crawled around between and on top of the rocks, chomping the algae. It was conspicuous in the shallows during the day, but hid beneath the rocks before its enemy, the spiny starfish, came out to play at night.
The urchins controlled the distribution of their food and therefore determined the character of the shallow underwater communities in the lough. In places the rocks were bereft of seaweed, where herbivorous urchins were abundant - but when Jack and John removed the urchins a lush vegetation of soft, succulent algae arose. When the animals were replaced they formed themselves into groups, eating their way outwards in expanding circles, leaving bare rock behind. It was the first evidence that urchins were the "cows" of the sea floor. Now we know of many places where there are "urchin barrens" underwater, because no seaweeds can survive the grazing pressure.
I was puzzled why Saccorhiza, which was so abundant in the Rapids, was absent from inside the lough itself. Were grazing urchins responsible? I set out to test whether they would eat Saccorhiza and offered pieces of the seaweed to urchins in submerged cages. I was dismayed to find they didn't eat the algal swatches, but wore them as hats instead. So I supplied them with oyster shell fedoras, and then they tucked into the plants. Were they really more fashion conscious than hungry? I offered the urchins a choice of two different seaweeds and they invariably scoffed Saccorhiza in preference to the other, a kelp that did occur naturally in the lough. I tasted them too, but preferred the other one - so the urchins were clearly discriminating, but not discerning.
The urchins living in the lough rarely left home, especially in the afternoon, without donning a shell, a leaf or, for special occasions, a tuft of algae. In the evening they rarely bothered. No one knows whether these decorations are parasols against the sun's glare in the shallows or camouflage to disrupt their outline as seen from above by potential predators such as birds. Hats are, of course, no disguise against their main enemy, crabs, but if there were no benefits to be had, why would they waste time fiddling with millinery instead of gliding off bare-spiked to browse and build up their gonads, to ensure that there would be more urchins next year?
Urchins had long been one of the most abundant creatures in the lough. If you stepped in the shallows, you were lucky not to get skewered in the foot. The brittle points break off in the skin and the wound festers if you don't get them out. I suffered for days after being spiked, until I realised that spines still lingered in the rubber bootees of my diving suit. Only when I put them on and my weight compressed the soles did a fakir's mattress emerge.
We had taken the urchins for granted, but this summer they were almost gone. Our census showed that the number in the southern basin of the lough had fallen from 35,000 a few years before to just 3,000. In their absence, Saccorhiza had not invaded the lough, but Codium had flourished and now painted a bright green swathe throughout the shallows - except, inexplicably, in what had long been called Codium Bay. I showed that the urchins ate the weed and destroyed far more than they consumed, by nibbling through the base so that the whole plant was detached and lost. A sea slug also eats Codium, but absorbs rather than digests its packets of chlorophyll, moves them to just under its skin and becomes a photosynthetic animal; it utilises the "food" that continues to be produced by the captive chlorophyll.
But what had caused the urchin decline? The urchin populations in Bantry Bay, just along the coast, had gone to French dinner tables, but there was no suggestion that they had been harvested from Lough Ine. Jack suspected crabs might be involved, so we set crab traps. When lecturing on this work a few years later, I accidentally called them trab craps, and found that once reversed, the words refuse to go back. As a result, the lecture went exceptionally well.
We baited the traps with Kit-e-Kat cat food and, after opening a dozen cans, the students turned decidedly fishy. The aroma drifts down the years; I can smell it still.
The number of crabs had increased tenfold over the last couple of years. Probably the mild winters had allowed them to stay in the shallows eating urchins instead of retiring into the depths as they usually did. But could even the aggressive devil crab destroy urchins on a sufficient scale? To find out, we moved a thousand urchins into an urchin-free area beside the Glannafeen laboratory. That night I dived over the site and found a battlefield with dead urchins everywhere. Crabs are assassins in pie crusts. The big ones can smash an urchin with a single blow, but the little ones have to juggle, turning the urchin over so they could insert their claw into the soft tissue around its mouth, then twisting it round and can-opening it. These deeds are so dirty that they are only perpetrated under cover of darkness. In a single night, eighty per cent of the transplants had perished. But why do crabs bother with urchins, which contain less edible tissue than almost any other creature?