Increasing CO2 in oceans will make it harder for deep-sea animals to "breathe"

Washington, April 18 (ANI): A new study has suggested that increasing carbon dioxide (CO2) and decreasing oxygen in the oceans will make it harder for deep-sea animals to "breathe".

The study, by marine chemists at Monterey Bay Aquarium Research Institute (MBARI), US, suggests that low-oxygen "dead zones" in the ocean could expand significantly over the next century.

These predictions are based on the fact that, as more and more carbon dioxide dissolves from the atmosphere into the ocean, marine animals will need more oxygen to survive.

Concentrations of carbon dioxide are increasing rapidly in the Earth's atmosphere, primarily because of human activities.

About one third of the CO2 that humans produce by burning fossil fuels is being absorbed by the world's oceans, gradually causing seawater to become more acidic.

However, such "ocean acidification" is not the only way that CO2 can harm marine animals.

In a "Perspective" published in the journal Science, Peter Brewer and Edward Peltzer combine published data on rising levels of carbon dioxide and declining levels of oxygen in the ocean in a set of new and thermodynamically rigorous calculations.

They show that increases in carbon dioxide can make marine animals more susceptible to low concentrations of oxygen, and thus exacerbate the effects of low-oxygen "dead zones" in the ocean.

Brewer and Peltzer's calculations also show that the partial pressure of dissolved carbon dioxide gas (pCO2) in low-oxygen zones will rise much higher than previously thought.

This could have significant consequences for marine life in these zones.

High concentrations of CO2 make it harder for marine animals to respire (to extract oxygen from seawater). This, in turn, makes it harder for these animals to find food, avoid predators, and reproduce.

Low concentrations of oxygen can have similar effects.

Currently, deep-sea life is threatened by a combination of increasing CO2 and decreasing oxygen concentrations.

The amount of dissolved CO2 is increasing because the oceans are taking up more and more carbon dioxide from the atmosphere.

At the same time, ocean surface waters are warming and becoming more stable, which allows less oxygen to be carried from the surface down into the depths.

According to Brewer, "Animals facing declining oxygen levels and rising CO2 levels will suffer in much the same way that humans in a damaged submarine would suffer, once the concentrations of these gasses reach critical levels."

"Our work helps define those critical levels for marine animals, and will enable the emerging risk to be quantified and mapped," he said. (ANI)