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Fertilising the sea with iron filings dramatically accelerates the growth of plant plankton, which absorb large amounts of greenhouse gases, an experiment in the Southern Ocean has shown.
Researchers who had spent the month spreading filings over Antarctic waters 2,500 miles southwest of New Zealand returned to Wellington yesterday enthusiastic about the results.
Rob Murdoch, of the New Zealand National Institute of Water and Atmospheric Research, said: "Not only did the numbers of phytoplankton bloom extensively but they were responsible for absorption of a significantly greater amount of carbon dioxide during the study period compared with the seas outside the area," he said. "The plankton in the growing patch also produced significant quantities of gases known to be important in cloud formation."
The aim of the research was to see whether the filings would replenish stocks of plankton, which form the foundation of the ocean food chain, and to discover whether the microscopic plants captured excess carbon dioxide from the atmosphere and contributed to cloud build-up.
The late John Martin, an American oceanographer, theorised in 1995 that phytoplankton needed iron in order to take nitrogen and phosphate from seawater, just as farm crops need trace minerals such as zinc and manganese.
Subsequent experiments showed that half a ton of iron filings triggered 30-fold to 40-fold increases in plankton stocks over areas of up to 193 square miles. This resulted in up to 9,000 tons of carbon dioxide being "locked up", and a three-fold increase in dimethyl sulphide particles, which have a key role in cloud formation.
Scientists believe that if the fertilisation could be done on a large enough scale in the Southern Ocean it could reduce the concentration of carbon dioxide in the Earth's atmosphere by between 6 per cent and 21 per cent, significantly cooling the planet.
Which headline best matches the content and meaning of the article?
Global warming caused by plankton reduction
Iron filings used to grow plankton
New Zealand research team investigate plankton growth
Plankton could help to reverse global warming