ANOTHER LIFE:I GREW UP in a landscape carved almost entirely from chalk. At the eastern fringe of Brighton, on the Sussex coast, white cliffs reared up at the bottom of the street. Behind us rose the first curve of the Downs, its crest still a chalky rubble of wartime ploughing. I scaled the cliffs to pick clove-scented stocks growing wild in the cracks, fished prawns in chalky runnels of the lower shore and brought home big, wave-rolled chunks of chalk to carve with my father's chisels.
All this rose to mind with last week's photographs from space of great turquoise swirls in the ocean west of Ireland – a milky bloom of plant plankton (phytoplankton) of the species Emiliana huxleyi.Such blooms are not unusual in early summer, as nutrients rising from the seabed feed phenomenal reproduction of single-celled algae, the primary "grass" of the ocean's food-chain. When conditions are right, the special gleam of Emiliana can develop simultaneously across 100,000sq km of sea – yet each individual cell is no more than some four thousandths of a millimetre in diameter.
There are thousands of species of phytoplankton, but what gives Emiliana its sequin-like sparkle is the cell’s secretion of chalky platelets (coccoliths), a beautifully intricate armour revealed by the electron microscope. The function of these little sun-reflecting shields of calcium carbonate is unknown – perhaps as filters against ultra-violet rays, or help in buoyancy. But collectively, drifting to the ocean floor, and raised in geological upheavals, their substance helped to build up the strata of chalk that band the cliffs of Antrim and built the snowy ramparts of the white cliffs of Dover – and those at the bottom of my street.
Thomas Henry Huxley, Darwin's pugnacious champion, was the 19th-century biologist recognised in Emiliana huxleyi,having studied the deep mud dredged up in explorations for transatlantic cable-laying and finding coccoliths – his word – composing so much of it. "A great chapter of the history of the world is written in the chalk," he wrote; and now its living organisms are under study for another great chapter, that of anthropogenic climate-change.
Emiliana has its own website, soes.soton.ac.uk/staff/tt/, at which “Ehux” (some call it Emily) is discussed by marine scientists in enthusiastic, and not overly technical, detail, with pictures and maps. This shining star among organisms so vital to ocean life, not to mention the future of human comfort – deserves the widest audience.
In comments on the photographs of the Emiliana bloom, Joe Silke of the the Marine Institute saw it as a particular sign of ocean health, as the plankton’s photosynthesis generates oxygen both in the sea and for the atmosphere. But its climatic significance is even wider.
The shimmering armour that makes the blooms of coccolithophores so obvious reflects light and heat back out into space rather than warming the ocean. One satellite study found an annual area of blooms covering 1.4 million sq km. And the algae’s mass manufacture of coccoliths from calcium and carbon adds to the ocean’s seabed store of carbon and affects the amount of CO2 held in the atmosphere.
Along with other phytoplankton, Emiliana produces the gaseous compound dimethylsulphide (DMS). Some of this, after the cells die or are eaten by the tiny animals of zooplankton, rises up from the sea in aerosol particles. These become nuclei for droplets of water condensation that make clouds. Their whiteness (albedo), as we are learning, also helps the planet to reflect sunlight back into space. Blooms of Emiliana in the northeast Atlantic have produced concentrations of DMS up to 10 times higher than in the surrounding waters.
Such important actions of phytoplankton in taking carbon out of the atmosphere and otherwise regulating climate have encouraged experiments in promoting blooms by fertilising tracts of ocean with the trace element iron. It could work, but, like so many strategies proposed for “geoengineering”, takes science into unknown hazards.
This spring brought proof from Canada that iron enrichment sharply increases the chances of producing blooms of highly toxic plankton species, such as those constantly monitored by our Marine Institute for their threat to aquaculture and coastal ecosystems. The build-up of man-made CO2 could menace Emiliana itself. What normally erases a bloom of the cells, along with consumption by zooplankton, is attack by the ocean’s teeming viruses and bacteria. But, like all marine organisms drawing on calcium for their structures – everything from crabs and winkles to coral reefs – coccolithophores are at hazard from the progressive acidification of the sea.
“It is by the population of the chalk sea,” wrote Thomas Huxley in 1868, “that the ancient and the modern inhabitants of the world are most completely connected.” This early support for evolutionary theory carries even more resonance today.
Eye on nature
I live on an estate about 20 minutes’ walk from the Slaney River. Recently a mother duck with three young ones arrived on the green in front of the house.
We gave them bread and water, and now they come every morning and evening. Sometimes mother duck comes on her own and quacks at the door for bread.
Marie Carroll, Enniscorthy, Co Wexford
What is the cause of lameness in older robins and blackbirds, which I notice occasionally? At present I have a cock blackbird with a swollen heel.
Rosemary Carr, Cashel, Co Galway
These conditions are usually caused by dietary imbalance or deficiency, particularly in some trace elements and the vitamin B range.
In a silage meadow with a lot of weeds, I see a small butterfly, about an inch across, with mainly orange wings that are black around the base, and with black freckles on the orange part.
Picia Harvey-Kelly, Killucan, Co Westmeath
It is the small copper butterfly.
I used to get great satisfaction from spotting bullfinches in the 1950s and 1960s, but I haven’t seen one for many years. Are they now very rare?
Con Shanahan, Kilkerley, Co Louth
They are still quite common, and are found in woods, orchards and mature gardens.
Michael Viney welcomes observations at Thallabawn, Carrowniskey PO, Westport, Co Mayo. E-mail: viney@anu.ie. Please include a postal address.
