Iron fertilizer can help prompt algae blooms, which absorb carbon dioxide and bury it on the ocean floor for centuries, a new study reports.
Dumping iron in the seas can help transfer carbon from the atmosphere and bury it on the ocean floor for centuries, helping to fight climate change, according to a study released on Wednesday.
The report, by an international team of experts, provided a boost for the disputed use of such ocean fertilisation for combating global warming. But it failed to answer questions over possible damage to marine life.
When dumped into the ocean, the iron can spur growth of tiny plants that carry heat-trapping carbon to the ocean floor when they die, the study said.
Scientists dumped seven tonnes of iron sulphate, a vital nutrient for marine plants, into the Southern Ocean in 2004. At least half of the heat-trapping carbon in the resulting bloom of diatoms, a type of algae, sank below 1,000 metres (3,300 ft).
"Iron-fertilised diatom blooms may sequester carbon for timescales of centuries in ocean bottom water and for longer in the sediments," the team from more than a dozen nations wrote in the journal Nature.
Burying carbon in the oceans would help the fight against climate change, caused by a build-up of carbon dioxide in the atmosphere that scientists say is raising temperatures and causing more floods, mudslides, droughts and higher sea levels.
The study was the first convincing evidence that carbon, absorbed by algae, can sink to the ocean bed. One doubt about ocean fertilisation has been whether the carbon stays in the upper ocean layers, where it can mix back into the air.
A dozen previous studies have shown that iron dust can help provoke blooms of algae but were inconclusive about whether it sank.
Large-scale experiments with ocean fertilisation using iron are currently banned by the international London Convention on dumping at sea because of fears about side-effects.
"I am hoping that these results will show how useful these experiments are," lead author Victor Smetacek of the Alfred Wegener Institute in Germany told Reuters.