What is Ocean Acidification?
Ocean Acidification is the term that is given to the process of oceans becoming more acidic, i.e. their pH is decreasing. It is still a relatively new field of research but there is a growing understanding of the threats that it poses. It is thought that the main cause is the addition of carbon dioxide to the oceans from anthropogenic sources such as the burning of fossil fuels [1]. Oceans act as a ‘sink’, i.e. they absorb carbon dioxide, as do plants and vegetation. Therefore, climate change would actually be a lot worse in terms of the greenhouse effect if oceans did not act in this way [1]. However, while this saves the atmosphere from some of the adverse effects of increasing levels of carbon dioxide, it has an adverse effect on the oceans themselves.
Carbonic Acid is formed when carbon dioxide dissolves in sea water and the acid acts to decrease the pH level of the oceans [1]. It is thought that the pH level of the ocean has already decreased by about 30% from a more alkaline state and it is argued that if the current rate of ocean acidification continues, by 2100 ocean acidity will increase by 150% [1].
Seawater has a natural pH of around 8.1 (0.1 lower than pre-industrial times), however the Intergovernmental Panel on Climate Change (IPCC) predicts that levels could fall as low as pH 7.8 by the end of the century [2].
Implications
The changes described above will inevitably cause adverse effects in the ecosystems of the oceans. One of the more understood implications is the reduced ability of organisms such as crustations to form shells or skeletons [1]. To form their shells or skeletons they need calcium carbonate which is alkaline, but with increasing acidity in the oceans this will reduce.
It is also thought that Coral Reefs will be severely affected by this phenomenon as the increasing acidity will inhibit their ability to form their hard protective surfaces correctly [2]. Findings from research carried out by scientists at the ‘natural laboratory’ in seas off Papua New Guinea indicate that corals will be some of the more severely hit species, with few types able to grow at pH7.8 [2]. The findings even suggest that coral will not grow at all in carbon dioxide rich seas [2]. The ‘natural laboratory’ was set up to mimic the conditions that would exist if carbon dioxide levels continue as they are [2].
The BCC has also published a study, which found that Clownfish appear to lose their hearing in more acidic seawater conditions [3]. The study found that in levels of acidity that are expected by the end of the century, the fish did not respond to the sounds of predators [3]. Sounds are also important for mating, pack hunting and foraging and these will all be affected by the fish’s ability to hear [3]. While the scientists found no apparent physical damage to the fish’s ears, there was some indication that there could be damage to the nerves or that fish are stressed by the higher acidity and behave differently [3].
Overall, there is still much uncertainty about the effects and causes of ocean acidification, but it is clear that there are adverse effects. Time will tell the true effects of increasing carbon dioxide on the oceans but arguably it is time that we do not have and therefore warnings as to the effects should be well observed and taken on board before it is too late.
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References
[1] UK Ocean Acidification Research Program (2011) [Online]. Available from: http://www.oceanacidification.org.uk/
[2] BBC News (2011) [Online] Available from: http://www.bbc.co.uk/news/science-environment-13569442
[3] BBC News (2011) [Online] Available from: http://www.bbc.co.uk/news/science-environment-13605113
