Each year, on 14 April, Japanese seaweed farmers gatheron a headland overlooking the Ariake Sea, a deep notch carved out of the southern island of Kyushu. Many of the farmers make their living in the waters below, others travel from coastal towns and villages elsewhere in Japan. They come to celebrate the life of a woman who lived and worked in Manchester, in the industrial north of England. Kathleen Drew had no connection with Japan, exceptforone thingan enthusiasm for seaweed, and in particular a silky, reddish weed called Porphyra. In Japan, people wrapped rice in it and ate it. In Manchester, Drew studied it. She would never know that people in a country she had nevervisited knew her name and held a festival in her honour. But when she discovered Porphym鈥檚 best-kept secret, she saved manyJapanese families from destitution and sowed the seeds of a great industry.
IN THE little villages along the shores of the Ariake Sea, fishermen had harvested the seaweed they called nori for longer than anyone could remember. Dried into paper-thin sheets, the glistening alga was a traditional delicacy. Demand outstripped supply, so the fishermen could sell all they collected. But nori was one of nature鈥檚 more unpredictable harvests. The first delicate ribbons appeared around October 鈥� as if from nowhere. By December, the silky fronds were ripe for picking. By spring, the fronds began to wither away, and by summer the seaweed had vanished. Some years it didn鈥檛 appear at all. In the good years, the villagers fished in summer, gathered nori in winter, and flourished. When the nori failed, they struggled to feed their families.
Nori has been a part of Japanese culture for at least 1500 years. By the 8th century it was a prized dish, but one that was so rare and costly only the noblest households could afford it. Then, in the 17th century, a few enterprising fishermen began to cultivate the weed in sheltered bays and inlets. Their methods were crude but they worked.
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Certain spots around the coast were known as good nori places, where the weed sprouted from the rocks, from jetties and pilings 鈥� in fact, from any submerged surface in the shallows. In early autumn, nori growers would take some bamboo sticks and ram them into the mud close to the shore. A few days later, they pulled up their poles, replanted them in water near their own villages, and waited. Sure enough, the poles were soon festooned with nori. By winter, the crop was ready to collect and spread out to dry. Cultivation increased output in the good years, but it didn鈥檛 make the harvest any more certain. Some years the weed still failed to appear.
By the early 20th century, marine biologists in Japan were desperately trying to solve the great nori mystery. Where did the seaweed go in summer? And why did it sometimes fail to reappear? If they could fill in the missing months in the life of Porphyra, they might be able to remove the uncertainty from nori cultivation.
Porphyra is a member of one of the most ancient groups of plants, the rhodophytes or red algae 鈥� organisms with a complicated life history. The alga grows from spores that settle onto any firm surface in shallow water, including bamboo poles. But no one knew where those spores came from. Although mature nori fronds produce spores of their own, they are not the same, and like the fronds themselves, they vanished in the summer.
In 1948, disaster struck Kyushu. Typhoons destroyed many fishing boats. The pearl oysters were killed by chemicals draining into the sea from the paddy fields. And the nori crop failed. With no boats, no oysters and no prospect of any nori, many of the men from the fishing villages headed off to the island鈥檚 coal mines to look for work. They had no reason to suspect their fortunes were about to change.
Halfway round the world, in a lab at the University of Manchester, botanist Kathleen Drew was wrapping up her study of purple laver, another species of Porphyra. Laver grows on rocky coasts around the British Isles and, like nori, it is edible. People living along the shores of the Bristol Channel 鈥� particularly in South Wales 鈥� eat the seaweed, not crisp and dried like the Japanese but boiled to a blackish gloop known as laver bread. Like nori, laver disappeared in summer and reappeared a few months later. After nine years of detective work, Drew had discovered where it went.
As with its Japanese counterpart, the purple fronds of laver produced spores, but these did not sprout new laver plants. Drew was as mystified as everyone else. Year after year, she collected laver spores and tried to persuade them to germinate. Her husband, Henry Wright Baker, professor of engineering at the university, built tidal tanks for her in which she could control temperature and light, and mimic the tides around the Welsh coast. But nothing she did would persuade the spores to sprout.
Drew decided to try a different tactic. Perhaps the spores only sprouted if they settled on something hard, where an emerging plantlet could get a firm roothold. Drew filled a flask with seawater, added some laver spores, and dropped in a carefully sterilised piece of oyster shell. Then the strangest thing happened. Out of the spores emerged not tiny leafy laver germlings but slender crimson threads. The threads began to burrow their way into the shell, and once inside grew into a network of fine, red filaments. The same thing happened whether she threw in an oyster, an old cockle shell or even a piece of discarded eggshell. After a few months the red threads turned, and their tips began to emerge from the surface of the shell. There they sprouted little pink tufts that produced spores of their own.
This organism was nothing like laver. In fact, marine botanists knew it as another species entirely, one they called Conchocelis rosea. Drew now knew that Conchocelis was just a phase in the laver鈥檚 life. And if that was so, then the 鈥渃onchospores鈥� escaping from the tiny pink tufts should grow into new leafy laver plants. They did.
In 1949, Drew鈥檚 revelation appeared in Nature. At last there was an explanation for the years when laver, and nori, went missing. Stormy weather interrupted the supply of conchospores, either by flinging Conchocelis-infested shells high up the shore or dragging them far out to sea.
The news soon reached Japan. At Kyushu University in Fukuoka, marine botanist Sokichi Segawa was astonished. It seemed so improbable. But if Drew was right, and all Porphyra were like laver, then it might be possible to culture the spores artificially and so guarantee a good nori harvest. First he repeated Drew鈥檚 experiments with nori: the result was the same. Then he went to see a man who could put the discovery to good use.
Fusao Ota, a marine biologist at the local fisheries research laboratory at Kumamoto, knew well the difficulties and hardships the nori farmers faced. When they were in trouble, they knocked on his door. Yet there was little he could do for them. Now, perhaps, he could change that. By 1953, Ota had perfected a method of artificially seeding nets with nori, a breakthrough that paved the way for the mass production of today.
Ota鈥檚 method was simple but effective. He stirred mature nori fronds in a vat of seawater so that they released their spores, then tipped the suspension into tanks containing oyster shells, leftovers from the cultivated-pearl industry. When the shells sprouted pink tufts, he stirred the water again to shake out the conchospores. Into this mixture, he dangled ropes and then strung them between poles in the shallow water near the lab. Nori fronds quickly sprang from the ropes. The nori growers were back in business.
Today, nori cultivation is the world鈥檚 most profitable form of aquaculture, a business worth a billion dollars a year. Growers work in collectives, taking their nets to be 鈥渟eeded鈥� at government-run centres where spores are cultured in huge tanks, safe from the vagaries of nature. At the end of each season, the growers return with some of their finest fronds to provide spores for the next season.
Drew never found out that her botanical detective work had saved Japan鈥檚 seaweed industry: she died in 1957 at the age of 56. But the nori growers knew how much they owed her. On 14 April 1963, they unveiled a polished granite memorial bearing the likeness of the woman they called the Mother of the Sea. And they have been back to pay their respects 鈥� and bring offerings of seaweed 鈥� every year since.