Anna Harris blogs on Ocean Acidification

Ocean Acidification

While global warming is currently an extremely high-profile topic, some other consequences of our civilisation’s large CO2 emissions remain comparatively lesser known. One of these such consequences is ocean acidification: the continuing decrease in the pH levels of our planet’s seas and oceans. The world’s oceans make up 71% of its surface and contain 97% of its water in total, so what are the implications of it getting more acidic?

Firstly, the reason why ocean acidification is occurring is due to carbon dioxide. The Earth’s oceans are an important part of the carbon cycle, as it is estimated that they absorb nearly a third of all global carbon emissions. Since, in recent history, our global carbon emissions have increased, more and more CO2 is being taken in by the oceans. This decreases the pH of their naturally slightly alkaline conditions to acidic by increasing the concentration of H+ ions present, as well as reducing the concentration of carbonate ions. While the overall amount of CO2 in the atmosphere may be reduced by ocean absorption, and therefore the heat trapped in the atmosphere is also reduced, this has negative effects for ocean life, and as a knock-on effect, all life.

The speed at which our CO2 emissions have increased, and therefore the speed at which the pH of the oceans decrease, is cause for concern because the time that organisms and ecosystems have to adapt to the new environment is reduced: there is not enough time for them to overcome the changes in order to survive. Scientists have noted that the new conditions can affect the shells of scallops, crabs, and lobsters (as they involve the use of carbonate ions); confuse the senses of some fish, making prey act like predators and predators like prey; and bleach and kill coral reefs.

The detrimental changes to marine life affect food webs and underwater ecosystems. This has a direct effect on communities who rely on certain organisms as a source of income. Certain coastal regions and communities in Alaska, for instance have been pinpointed as areas and groups seriously at risk as a result of ocean acidification. This is due to the fact that their surrounding oceans are already naturally high in carbon dioxide and therefore more greatly vulnerable to acidification, and many Alaskan native communities rely on their fisheries for income- for example, Bering Sea crab fisheries and salmon fisheries. Another example of a food web forced into change by ocean acidification in Alaska begins with scallops, whose population is reduced as a result of a lack of carbonate ions available that are needed for their shells. Scallops are eaten by walruses, but if their population decreases the walruses face losing their source of food. This forces them to turn to other sources of food that they wouldn’t choose naturally, such as eating seals. To link this back to the effects of ocean acidification on communities, walruses eating seals is believed to be a bad omen for some native groups. It is these native groups thought to feel the effects of ocean acidification most greatly, and organisations such as the NOAA (National Oceanic and Atmospheric Administration) in America seek to unite these native communities with governmental and industry groups in order to overcome and adapt to the threat that ocean acidification poses to way of life.

Ocean acidification has been called the “evil twin” to global warming/ climate change, and they share a solution: reducing global carbon emissions. While certain communities face the challenge of adapting immediately to survive the affects of ocean acidification, the long term remedy to this environmental crisis relies on international cooperation in order to reduce our use of fossil fuels and help our planet become healthier, on land and in the sea.

Anna Harris