Ocean Acidification - Cause for Alarm and Action

Corals and other marine organisms, specifically those with shells and skeletons, are most at risk from ocean acidification. (Photo: D. Calma/IAEA)

"Ocean acidification is one of the most important issues facing us today. It's a new phenomenon, but an undeniable phenomenon," says Wendy Watson-Wright, Assistant Director General and Executive Secretary of the UNESCO Intergovernmental Oceanographic Commission (IOC).

"And given the possible impacts that it could have on just about everything living in the ocean, it is very, very important."

Ocean acidification occurs as oceans absorb the rising quantities of carbon dioxide in the atmosphere. When dissolved, the carbon dioxide forms carbonic acid, creating a more acidic environment, which can threaten marine ecosystems.

In response to the international scientific community's call for more coordinated research and action, the IAEA has created the Ocean Acidification International Coordination Centre, which will be launched this summer. The Centre is based at the Environment Laboratories of the IAEA in Monaco, and is supported by several IAEA Member States. It will be established under the IAEA Peaceful Uses Initiative project.

The Ocean Acidification International Coordination Centre will serve the scientific community, policymakers, schools, media, and the general public.

Ocean Acidification's Devastating Effects

"Fundamentally, ocean acidification is modifying water's chemistry, which can possibly have devastating effects on all organisms living in the marine environment. This is especially true if one considers the combined effects with other stressing factors such as water temperature increase and oxygen depletion," says Michel Warnau, one of the IAEA's lead scientists on the issue of ocean acidification.

"If you change one thing in an environment, there can be many repercussions throughout the ecosystem and its food webs. So this issue can ultimately affect how much food is available, as well as the biodiversity of our seas," he says.

Corals and other marine organisms, specifically those with shells and skeletons, are at particular risk. That's because these marine organisms use calcium carbonate to develop their skeletons. This is normally done in pH balanced seawater. Severely changing the acidity/alkalinity of seawater disrupts this delicate dance.

"Acidification affects the carbonate equilibrium in seawater, thereby affecting all the organisms relying on carbonate to develop their skeletons. And this could have huge repercussions, especially when affected species are habitat builders, like tropical corals," says Warnau.

Nuclear applications are especially precise in determining the inclusion of Calcium-45 in the skeletons of organisms. This helps scientists determine the organisms' capacity to grow under ocean acidification conditions.

Change One Thing

Sarah Cooley from the Woods Hole Oceanographic Institution in the United States says, "All these organisms (molluscs or shellfish and corals) are at the lower level of the food chain. And as they are affected, their predators will also be affected."

Moaz Fine, from the Interuniversity Institute of Marine Sciences in Israel, says corals' ability to cope with the stress of ocean acidification varies. "Some corals are doing worse than others. And this gives some hope that maybe some species will survive longer. On the other hand, when we look at the reef or coral associates (like bacteria and fungi) that live inside coral and give them their energy, all these associates are changing under ocean acidification conditions."

The extent of these changes is difficult to measure because there are hundreds of organisms living with corals. "And when they change we cannot assess or estimate how that will affect the health of the coral. And if it does change the health of the coral it might eventually compromise the physiology, as well as the whole reef ecosystem," says Fine.

Laura Parker at the University of Western Sydney in Australia studies ocean acidification's effects on oysters. "Oysters are suffering reduced growth and increased abnormality, and also reduced survival when they're exposed to ocean acidification. It's also taking them longer to develop. So when you get oysters to actually eat, it takes them longer to get to an acceptable size."

Philip Munday at James Cook University in Australia, has been studying the impact ocean acidification might have on fish.

"Larvae use smell to find their way home from the plankton to the reefs. When they get there, they use smell to avoid being eaten by predators; and to discriminate between their parents and non-relatives. We're finding that fish who have been treated with elevated levels of carbon dioxide (mimicking what might happen in the oceans by the end of this century), lose their ability to differentiate between these ecologically important smells," says Munday.

"We're concerned by this kind of behaviour and we need to do a lot more work to understand how this could affect fish populations as well as predators."

While Some Species Suffer, Other, Less Desirable Ones Flourish...

Weed-like marine species (sea grasses) are quite happy in places where there is variable pH. And when they're introduced into ecosystems where there's CO2 in the water, they thrive while other species die out.

Jason Hall-Spencer, from the University of Plymouth in the UK observes the ocean bed near submarine volcanic carbon vents to study what might happen to the oceans in the future as more carbon dioxide gets into the atmosphere.

"Worldwide these weed-like species are causing ecosystem disruption all over the place," says Hall-Spencer. "There's a concern that we might be opening the door to the prevalence of these organisms by increasing CO2 in the atmosphere."

Uncertain Outcomes

The scientists all agree that ocean acidification will have a dramatic impact on some species. But the big picture of long-term consequences is still elusive.

"The inability to predict processes at this stage is the biggest threat. It's very hard to manage natural resources when you don't know what you're dealing with," says Fine from the Interuniversity Institute of Marine Sciences in Israel.

Seeing the Big Picture

The IAEA is one of the organisations hoping to bring ocean acidification research to the level where the big picture will become clearer to scientists, politicians and global populations.

The IAEA, through its Environment Laboratories in Monaco, is using radiotracers to track the effects of acidification on ocean chemistry and marine life. Marine radioisotopes provide a powerful tool both to help diagnose problems in ocean models and to help orient future model development. To support international efforts to mitigate ocean acidification, the IAEA partnered with IOC-UNESCO and others to draft the 2008 Monaco Declaration, which calls for substantial reductions in CO2 emissions to avoid widespread damage to marine ecosystems caused by ocean acidification. The IAEA is an active member of UN Oceans.

"The possible impact of ocean acidification should not just be a cause for alarm, but a cause for action," says Rodelio Subade, Director of the Institute for Fisheries Policy and Development Studies College of Fisheries and Ocean Sciences in the Philippines.

Last update: 11 November 2014