Ocean fix for climate change finds tentative support

Marine life steers clear of waters poisoned with carbon dioxide

Marine organisms can sense and avoid high concentrations of carbon dioxide, according to a study of a seafloor vent off the coast of Hawaii. The result provides tentative support for plans to tackle climate change by dumping carbon dioxide in the ocean.

Researchers have long been concerned that adding high concentrations of CO₂ to the ocean might cause serious damage to local marine life — some studies have shown that it can kill marine organisms such as nematodes (see Nature 430, 391; 200410.1038/430391b). Environmentalists have blocked some plans to conduct further tests, fearing that even small injections of CO₂ might open the door to larger tests or industrial projects.

So the researchers turned instead to studying a natural plume of CO₂ that bubbles up from a subsea volcano called Loihi, near Hawaii. They wanted to assess fears that adding CO₂ to the ocean might create a ‘mortality sink’ — a spot where marine organisms die, attracting scavenging creatures that would in turn be killed.

But this kind of death trap is unlikely to occur, says Jeffrey Summers, a physicist with the Office of Fossil Energy at the US energy department in Washington DC. Summers and colleagues set cages baited with mackerel close to the Loihi plume and at various distances from the CO₂. The bait away from the plume was eaten in less than 24 hours, whereas the bait over the vent remained untouched for more than a week.

Eric Vetter, a marine biologist at Hawaii Pacific University who worked with Summers on the project, thinks animals are avoiding the cages because they can sense the high CO₂ levels. “The results are promising,” he says.

The study, scheduled to be presented on 6 September at the 7th International Conference on Greenhouse Gas Control Technologies in Vancouver, Canada, also suggests that sea creatures can recover from short blasts of CO₂. Summers' team dragged cages of amphipods — shrimp-like creatures — over the vent. The animals seemed to be anaesthetized by the gas within 10 minutes, but became active again around half an hour after being removed from the plume.

Vetter stresses that the work is “very preliminary”, and adds that much more data are needed before conclusions can be drawn about the wisdom of dumping CO₂ in the sea.