There’s little doubt that increasing carbon dioxide (CO2) emissions through human industry contribute to the changing of the Earth’s climate. Excess CO2 is absorbed by our ocean’s, changing their chemical composition and driving more blustery ocean winds that force deeper areas of sea water, which are naturally more acidic, to mix with shallower layers. The net outcome is ocean acidification, which can affect resident sea creatures. In particular, levels of aragonite, a naturally ocurring form of calcium carbonate used by plankton, fish and shellfish to build their skeletons and shells, drop severely in acidic sea water, making it difficult for organic calcification to proceed.
One species that incorporates aragonite into its shell is the sea butterfly, Limacina helicina antarctica, seen on the right. This creature lives in the Antarctic Ocean, has a lifespan of around 2 years and grows to be around 1 cm in diameter. As part of the British Antarctic Survey, researcher’s analysed how the sea butterfly was affected by ocean acidification in a test area located in the Scotia Sea. Specimens plucked from particular geographical quadrants where ocean winds caused more deep water upwelling and greater acidification exhibited substantial shell damage and dissolution (see image left; the top is a shell from a section with normal acidity levels, while the bottom is a shell from an acidic section). Furthermore, shells only had to bathe in such water for eight days to show significant signs of dissolution. While this doesn’t necessarily kill the little beasties, it does mean they are more vulnerable to attacks by hungry predator’s, and are more susceptible to infections, since they are in a weakened state.
Thus, as the acidic areas of the ocean continue to expand, populations of aragonite-shelled organisms will likely diminish and further affect global climate flux.
Bednaršek, N., Tarling, G., Bakker, D., Fielding, S., Jones, E., Venables, H., Ward, P., Kuzirian, A., Lézé, B., Feely, R., & Murphy, E. (2012). Extensive dissolution of live pteropods in the Southern Ocean Nature Geoscience, 5 (12), 881-885 DOI: 10.1038/ngeo1635