Over the past decade, ocean acidification has started to receive recognition outside science, though primarily as another weapon in the 'carbon dioxide' culture war on the modern world, similar to methane being discussed this year.

Politics aside, it is a vital area for study and a new article outlines three major challenges to understanding the real issues and effects: It needs to expand from single to multiple drivers, from single species to communities and ecosystems, and from evaluating acclimation to understanding adaptation.  

For the scientific community, it is obvious that ocean acidification does not occur in isolation. Rising temperatures, loss of oxygen, eutrophication, pollution and other drivers happen simultaneously and interact to influence the development of marine organisms and communities. It is when dealing with publicity by advocacy groups, the media and policy makers that 'magic bullet' thinking has to be clarified. 

"The effects can be additive, synergistic or antagonistic and it is generally not possible to extrapolate from single- to multiple-driver responses," explains Ulf Riebesell, professor for Biological Oceanography at GEOMAR Helmholtz Centre for Ocean Research Kiel. "But with an increasing number of parameters, experiments become increasingly challenging in terms of time, space and costs. Also, it becomes ever more difficult to compare and verify results of similar studies."

More scientific literature will make it less likely that groups will violate international law and just engage in their own real-world experiments without being called out by others in science, as happened with the LOHAFEX debacle in 2009, with German scientists using a loophole to get sanction from the German government to create a potential disaster after it had happened.

With more ocean acidification, many calcifying organisms such as corals, mussels or snails will find it more and more difficult to build their shells and skeletons. The extra energy needed for calcification will be lacking for other biological processes, such as growth or reproduction. 

As shown in laboratory experiments, evolutionary adaptation to ocean acidification is possible. The larger the population size of a species and the shorter its generation time is, the higher the chances are that it can adapt to new environmental conditions through selection or mutation. But can adaptation keep up with the fast changes we are experiencing today? Are the organisms able to maintain their functions within the changing ecosystem?

To make further significant progress in the future, ocean acidification research has to integrate the knowledge gained in its three diverging branches - addressing multiple stress factors, competitive and trophic interactions, and adaptation through evolution. "This requires an interdisciplinary effort, for example through long-term experiments that examine the effects of multiple drivers over many generations at the community level.

"Experiments have to be tightly integrated with field studies and model simulations," says Riebesell. "A key factor in this process will be that funding opportunities are opened up for large-scale integrative projects, long-term monitoring and international collaborations."