Ocean Acidification Poses Threat to Wide Range of Animal Life, Study Shows

As the ocean continues to grow more acidic, many marine animals will face negative consequences, though to varying degrees due to differences in bodily functions, according to a new study published in the journal Nature Climate Change.

According to the researchers, the world's oceans are responsible for absorbing more than a quarter of the carbon dioxide emitted through human activity, thus acting as a stabilizing force for the Earth's global temperatures. However, such storage is not limitless nor without its consequences.

As carbon dioxide dissolves in water, carbonic acid is formed, causing the pH value of the oceans to drop. This process, known as ocean acidification, has long been reported to affect ocean biota, though to what degree has not always been clear, according to biologists at the Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research who, in order to gain an overall view of it effects, surveyed a wide range of studies on the subject.

In all, the researchers examined 167 studies with data regarding over 150 species given a wide range of carbon dioxide concentrations. In particular, the research focused on changes in metabolism, growth, calcification or behavior.

The results, according to the scientists, were ominous.

"Our study showed that all animal groups we considered are affected negatively by higher carbon dioxide concentrations,"  co-author Astrid Wittmann said. This was especially true, the studies showed, in the case of corals, echinoderms and molluscs, which reacted most sensitively to a drop in pH value. Crustaceans such as the Atlantic spider crab or edible crab, on the other hand, would only be impact under scenarios of higher concentrations of carbon dioxide, they found.

The reason for this, the scientists explain, lies in the animals' varying physical abilities. Fish, for example, are active, and thus able to balance a drop in the pH value in their blood much more handedly than corals, which spend their entire life in one place, unable to to compensate for any rise in carbon dioxide levels.

Though, the researchers point out, animals' sensitivity to ocean acidification may increase in the case of rising sea temperatures.

Conducted in the framework of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), the new study is, according to its authors, designed to offer an overview of the current level of scientific knowledge on ocean acidification.

"For us," co-author Hans-Otto Pörtner said, "it was important not only to present the research results of recent years but to assess which impacts climate change will have on species."