Acidification
About a quarter of the world’s annual carbon dioxide emissions are absorbed by its oceans, which offsets the amount of carbon dioxide absorbed within the atmosphere. Climate change and its impacts are thus mitigated significantly. However the price for this stabilization is high: due to this uptake of carbon dioxide, the basic pH of the oceans is being shifted towards neutral, with an increased amount of hydrogen ions and a decrease in carbonate ions. This poses a threat to many ecosystems and organisms, as both coral reefs and shell-forming organisms need carbonate ions to build and maintain their skeletons and shells. With these changes in ocean chemistry, calcification is becoming increasingly difficult. Acidification also has a negative impact on fish, and appears to impair the olfactory sense in larval clownfish, making it difficult for them to find a suitable reef habitat. In one experiment on the effects of this acidification, it was found that they can even be attracted to stimuli they normally avoid. These are just a few examples of how marine organisms suffer from these changes. Acidification is likely to accelerate even further during the next decades, and the more acidic the oceans become, the less carbon dioxide they can absorb. The video portrays both the liveliness of a reef ecosystem, as well as the dying process.
Sources: United Nations Department of Economic and Social Affairs: Sustainable Development Goals Report 2022, Cambridge 2022.
Munday, Philip, et al., “Ocean acidification impairs olfactory discrimination and homing ability of a marine fish”, in Proceedings of the National Academy of Sciences, vol. 106, issue. 6, (2008): 1848-1852.