Dr Helen Findlay gathering water samples with a Niskin bottle
If you want to understand how ocean acidification might impact some marine creatures you need to do two things. First go to the seaside and find a seashell. Then go to a shop and buy a fizzy drink, any brand will do. Put the seashell in the fizzy drink and leave it for a few days. You will see that it is starts to dissolve away.
A similar process is happening in the oceans today. Carbon dioxide in the atmosphere is being absorbed into the ocean. When carbon dioxide dissolves in water it forms carbonic acid. Fizzy drinks are carbonated – they have carbon dioxide bubbled into them and this makes them acidic. Carbon dioxide is taken up into cold waters more rapidly and so the process of ocean acidification affects the coldest seas, such as the Arctic Ocean, the most.
Sampling bottles
On the pH scale the oceans are actually basic – the current average pH level of the oceans is about 8.2 (compared to freshwater which is pH 7). By continually adding more carbon dioxide, and increasing the amount of hydrogen ions, the ocean is becoming more acidic – the pH level is dropping. The pH level will continue to decrease into the future as long as carbon dioxide keeps being absorbed by the oceans.
Since the beginning of the Industrial Revolution, there has been already been a 0.1 drop in pH level. Models predict that the pH level will continue to lower (become more acid) to 7.8 in the next 100 years and to 7.4 in 300 years.
This may seem like a small amount but the impact can be quite large. All organisms need to regulate their internal pH and marine creatures are no exception. The difference is that many marine organisms are more dependent on the ocean to act as a pH regulator. It is also important for those organisms that have shells made of calcium carbonate – they find it difficult to maintain their shells, which start to dissolve as the pH decreases (just like in a fizzy drink, only much slower).
The Arctic acts as a bellwether for acid levels in our seas and their impact on the marine ecosystem. Acidification is thought to happen here faster than anywhere else but there is still a lot we don’t understand about how the sea ice and associated processes affect how carbon dioxide is taken up into the Arctic Ocean. The research being carried out here at the Catlin Arctic Survey Ice Base is trying to find out more about the transfer of carbon dioxide through sea ice, what this means in terms of ocean acidification and how acidification, or changes in these processes, might affect the organisms that live in and under the sea ice.
Dr Helen Findlay and Dr Victoria Hill
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