ANOTHER LIFE:THE LAST TOMATO plants and bean-vines have been carried away to the compost bin, giving me a clear view down the polytunnel, if one somewhat dimmed here and there by a glaze of green algae. Sponging it off to restore the full flood of light is a regular autumn chore for tunnel gardeners, but a summer made for moulds and slimes encouraged the algae's cellular spread on both sides of the plastic.
The rainy season also brought letters from readers baffled by the sudden appearance, after heavy showers, of dollops of glossy, greeny-brown “seaweed” on the gravel or soil around their houses.
“It looks,” wrote Ann Ryan from Wexford, “as if it’s fallen from the sky.” Her mystification rang back three centuries to Dryden: “The shooting stars end all in purple jellies,” he wrote, “and chaos is at hand.” The chaos bit may seem unusually apposite just now, but “fallen star” and “star jelly” were among old folk-names for the substance, and, as a 19th-century Inishowen stargazer told a folklorist: “I watched it fall and there was nothing there but a lump of cowld starch.”
Alerted to the latest puzzle, an inspector friend from the Met Office was taken aback to begin noticing “that stuff, all over the place” on his travels around Co Galway. He asked a Teagasc man in Athenry, who ventured that it might be a type of frog spawn.
Its true nature was identified by Prof Mike Guiry of NUI Galway, a European authority on the whole algal family, from the skin of freshwater cells on my polytunnel to the great, tough fronds of kelp in the sea. The “star jelly” was a species of blue-green algae, Nostoc commune, that forms chains of cells in a gelatinous mass. It can spring up, apparently from nowhere, on gravel paths, and persist for decades (the cells of one Nostoc species, kept in dry storage for 70 years but then moistened, leaped into filamental life).
Dr Guiry has photographed Nostoc at a number of places in Galway, as may be seen at his encyclopedic website, algaebase.org
“It does no harm,” was his assurance, “and a lot of people who see it probably think it’s dog poo.”
The species can also take on some unexpected shapes.
Once, on an Arctic expedition to East Greenland, I was baffled to find what looked like large green grapes, floating in a bunch beneath the surface of a shallow tundra lake. Without knowing it then, I was looking at Nostoc commune formed into globular colonies.
In the mountains of Peru, these little green balls have been a regular part of the local food, tosssed into stews for centuries. Along with Nostoc commune, another Nostoc species, known as “black moss”, that grows in filamental mats in the arid steppes of west China, has also been a traditional food delicacy, now in huge commercial demand. And in the general world of “health” foods, various forms of blue-green algae, “properly harvested from pristine lakes” are marketed as nutritious, vitamin-rich superfoods that kept the Aztecs fits and strong.
But blue-green algae – cyanobacteria to scientists – can have another, less benevolent, side. Multiplying as algal blooms on our midland lakes, they can carry toxins fatal to swimming dogs and even harmful to humans. Chinese and Scottish scientists, testing samples of Nostoc from different freshwater and marine habitats across the world (including blooms on northern Irish lakes) have found them carrying a toxic amino acid with links to brain diseases such as Parkinson’s and Alzheimer’s.
Without cyanobacteria, however, we probably wouldn’t be here. Blue-green species very like them go back three billion years to the start of life on Earth, concentrating in scummy glazes like the ones I’m now sponging off my tunnel. Most of them were single-celled, lacking even a nucleus, and a few were strung together in filaments. As they developed photosynthesis, taking energy from the sun, they gave off oxygen, thus helping to change the atmosphere to support higher plants and animals, including, eventually, ourselves.
In today’s world the seas’ algal blooms soak up massive amounts of CO2, prompting widely criticised and futile attempts to create more plant plankton by dumping iron into nutrient-poor stretches of the ocean.
At the same time, producing diesel from the oils in freshwater algae has become the hottest bet in “green” biofuels, attracting massive investment from oil giants such as ExxonMobil.
In Ireland, too, Bord na Móna is considering using its cutaway bogs as lagoons to grow algae in water warmed by waste heat. Much work is going on around the world to breed – or engineer – strains of algae for a higher oil content, and to work out whether these are best floated on open ponds, or grown on plastic sheets in closed environments.
As I sponge away in my tunnel, I can say that the latter works pretty well.
EYE ON NATURE
As I was about to uproot a ragwort plant recently I noticed that it was host to some caterpillars. I never suspected that something lived on it.
Sean McNelis, Carrig, Co Donegal
Ragwort is the plant food for the caterpillar of the beautiful blue, red and pink cinnabar moth.
Recently we saw a seal in a cave on a beach in Wicklow. Its partner was waiting anxiously in the sea outside. Was it sick or about to deliver its baby seal?
Lasara (4), Muireann (5), Caoileann (7), Art (9) and Rionagh (12) Lynch, Blackrock, Co Dublin
It was probably a grey seal that you saw. She was ashore to deliver a baby seal and a male seal was waiting in the sea to mate with her after the birth.
Bracken has become an abomination on the Wicklow hills. To my dismay I see it inching higher each year. It can even subdue brambles, and they are, in their own right, a tough coloniser of ground. Within three years it can swallow a whole hillside of purple heather, which has lovely flowers, delicious fruit and is a metropolis of insect and bird life. But nobody seems interested in removing bracken.
David Nolan, Santry, Dublin 9
Michael Viney welcomes observations at Thallabawn, Carrowniskey PO, West- port, Co Mayo. E-mail: viney@anu.ie. Include a postal address.
