Study Considers Impacts of Ocean Acidification on Pteropods (Sea Snails)

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Ocean Acidification Study Findings

Eroded sea snail shells – due to ocean acidification? Image: credit NOAA

The BAS/NOAA/UEA study is the first to examine the impacts of ocean acidification on sea creatures in place, rather than in a laboratory.

Co-author Dr Geraint Tarling told Decoded Science, “we validate a large number of laboratory experiments showing that pteropods, which build their shells out of aragonite, are vulnerable to the early effects of ocean acidification.

Focusing on an area of upwelling (where winds cause divergence of surface waters, allowing colder water to rise to the surface) the team studied the shells of pteropods.

Aragonite is a more-easily eroded form of calcium carbonate; and in one location the researchers discovered evidence of increasing erosion of those shells at 200m depth, much shallower levels than expected.

Implications of the Research

The researchers attributed their findings to a combination of upwelling of cold water and the increasing acidification of the oceans; they highlighted two key implications. Firstly, although the pteropods were not necessarily killed by the increased erosion, they were left vulnerable, increasing the risk of population collapse. Secondly, the increase in erosion has the potential to reduce the amount of carbon being sequestered (removed from the current cycles) by deposition on the sea bed.

As aragonite is more easily soluble than calcite it will be more quickly affected by increasing acidification. But, as Dr Tarling notes, this is potentially only the beginning of the story. “As carbonate ion concentrations are driven even lower, calcite-shelled organisms will be affected in turn,” he told Decoded Science.  “The latest models predict that widespread aragonite under-saturation will occur in the Southern Ocean surface waters in winter by 2050. Calcite under-saturation will take 50 years more to arrive.

Climate Change and Ocean Acidity

Although this is just a single study, the researchers believe that it raises key questions about the future impacts of ocean acidification. “Most models consider that further acidification is inevitable, so this study is showing that responses in marine organisms such as pteropods will also be inevitable,” said Dr. Tarling. “How other species will cope with the loss of one of their main competitors or prey sources is something we are only starting to consider.”

Sources

Bednarsek, N. et al. Extensive dissolution of live pteropods in the Southern Ocean(2012). Nature Geoscience. Accessed November 25, 2012.

Forster, P. et al Changes in Atmospheric Constituents and in Radiative Forcing. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change . (2007). Cambridge University Press. Accessed November 25, 2012.

NOAA. Trends in atmospheric carbon dioxide. Accessed 24 November 2012

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