FINDINGS


Increased emissions of carbon dioxide affect more than the atmosphere. Much of the gas is absorbed by the oceans, causing them to become more acidic.

Recent research has looked at the impact of the acidification on corals and other small calcifying organisms. But increasing CO2 - coupled with gradual warming of the oceans - may have other effects, and may affect bigger creatures, because there will be less oxygen at the surface and deep oxygen-poor zones will expand vertically.

A study in The Proceedings of the National Academy of Sciences looks at the potential effects on one of those bigger creatures, the Humboldt squid, which can be two meters long and weigh more than 45 kilograms. Rui Rosa and Brad A.Seibel of the University of Rhode Island put squid in a flow-through respirometer that allowed measurements of metabolism while concentrations of gases in the water were changed.

Near the surface, these creatures demand a lot of oxygen, partly because they are always on the hunt for fish and their respiratory and propulsion systems are of limited efficiency. They migrate at night to deeper, oxygen-poor waters, where they can recover.

The researchers found that under conditions of elevated CO2 similar to those forecast for surface waters for the end of the century, the squids’ metabolic and activity rates slowed significantly. So it is a good bet that these squid will become more lethargic, less adept at hunting prey and less able to avoid predators.

The researchers say warming waters will mean that the oxygen-poor zones the squid inhabit at night will be shallower. The net effect is a big squeeze of squid habitat, with potential effects for their prey and their predators.

HENRY FOUNTAIN