Profitable Wonders
James Le Fanu
We are forever awestruck by the scale, and ambition, of monumental engineering projects, past and present – the pyramids at Giza, the Great Wall of China, the Suez and Panama canals dividing continents, and the massive Hoover and Aswan dams across the Colorado and Nile rivers.
Still none can compare to the endeavours of the tens of billions of minuscule invertebrate creatures, the corals. Over millennia, they have built in limestone the largest durable structures on earth – fantastical, teeming subaquatic cities stretching for thousands of miles along the coasts of Australia, the South-east Asian archipelago and the Caribbean.
These coral reefs occupy less than one per cent of the ocean floor yet are home to a quarter of all forms of maritime life, thousands of diverse species of fish, molluscs, lobsters, shrimps, turtles, starfish and many, many more.
The coral’s mode of construction of this ‘most biodiverse ecosystem on the planet’ was first comprehensively described by Frederic Wood Jones, a British naturalist and son of a Hackney builder. His first appointment, after he had qualified at the London Hospital, was as medical officer on the remote, sparsely inhabited Cocos (Keeling) Islands, then a British protectorate in the middle of the Indian Ocean. It had been ‘ruled’ benignly by three successive generations of an eccentric Scottish family, one of whose daughters he would eventually marry.
‘Most of my days were spent wading across the reefs or sailing a boat on the lagoon,’ he recalled in his classic work Coral and Atolls (1910). ‘The beauty of the clear water and the breaking surf on the barrier made these expeditions a perpetual delight.’
The young corals begin life as freefloating, translucent, pear-shaped larvae – each the diameter of a pinhead – before settling on a stony surface. Once affixed, they differentiate, forming six tentacles surrounding a mouth, opening into a single sac-like internal cavity.
The tentacles come armed with stinging harpoon-like nematocysts for capturing the passing plankton on which the corals feed, excreting the waste products of digestion back out through the mouth.
The coral’s subsequent growth and development is predicated on one of the most profound (in its consequences) symbiotic relationships in nature.
Early on, the young coral traps chlorophyll-containing algae which it incorporates into the tissue of its tentacles. These algae make use of the carbon dioxide, nitrates and phosphates produced by the coral’s metabolism. And, in return, the chlorophyll within their cells, activated by the sunlight passing through the translucent water, generates – through the process of photosynthesis – oxygen, glucose and amino acids. These provide the coral with the energy and chemicals necessary to secrete the limestone that forms its protective, cup-like residence.
The young coral, once established, buds off numerous further polyps, creating over time a colony of cloned replicas of itself. Each is ensconced within its own limestone niche. Nonetheless, the colony acts synchronously, emerging and retracting in response to external stimuli, collectively reacting to any damage by the secretion of yet more limestone.
Despite having no nervous system, corals, Wood Jones noted, are ‘an impressionable and responsive class of animals, resourceful when faced by the demands of their changing surroundings’. The defining feature of the sub-aquatic cities they build is their pristine, breathtaking beauty – a panoply of extravagant forms and brilliant coloration unparalleled in our terrestrial world.
Each of the 700 species of coral has, astonishingly, its own distinctive architectural style: yellow and cylindrically branched (the staghorn corals), greenish-blue, domed and fissured (the brain corals), flat, table-like corals interspersed with slender, upstanding minarets (the pillar corals), gold star corals, flowery coronation corals, mushroom, and fan and bubble corals.
Through this wonderland flit shoals of fish more variegated than seems possible – butterfly fish, angel fish, surgeonfish and cardinal and parrot fish. The variants of each species exhaust the full possibilities and more of design and colour: striped – some horizontally, others vertically or diagonally – hatched or stippled in vivid and boldly contrasted hues of blue, green, purple, red and gold.
Since Wood Jones’s pioneering observations, we have learnt vastly more of the attributes and behaviour of the numerous marine inhabitants of these ocean kingdoms and the web of interconnections that sustain them. Still, in his words, ‘the strange and fantastic efforts of nature’ that underpin their pristine beauty remain as elusive as ever.