The problem of Ocean Acidification

Ocean acidification (OA) is caused by the increasing partial pressure of carbon dioxide (a weak acid) in sea surface waters. Since the industrial revolution, oceans have absorbed 560 billion tones of CO2, increasing acidity by 30% and depreciating the pH of surface waters from 8.2 to 8.07. Models project an ocean pH of 7.8 by the end of the century, this would mean that corals and all organisms that calcify a shell would be severely at risk. The pH of the oceans has naturally fluctuated over time, however we are currently acidifying the oceans at 50 times the rate of interglacial periods during the last million years. The problem with the mass OA signature is that it foretells a long recovery period which could even extend after greenhouse gases are reduced in the atmosphere. This could put our entire oceanic food chain, that helps sustain us, in considerable jeopardy.

A complication to the ocean acidification problem is that the pollutant copper is likely to increase with the predicted pH change, this means that copper toxicity to marine organisms is likely to increase. A recent study has found that copper toxicity and OA reduced larval survival of the polychaete Arenicola marina (large marine worms that live in intertidal sediments) by 24% compared to single ocean acidification and copper exposures. Sperm motility was also negatively affected by the additive effects of the two pressures. These findings demonstrate that OA will likely increase the toxicity of copper to marine organisms which could have great consequences to our marine ecosystems.

References

Schnoor, J. L. (2014) Ocean Acidification: the other problem, Environ. Sci. Technol., Vol. 48 (18), pp 10529–10530

Campbell, A. L., Mangan, S., Ellis, R. P., Lewis, C. (2014) Ocean Acidification Increases Copper Toxicity to the Early Life History Stages of the Polychaete Arenicola marina in Artificial Seawater, Environ. Sci. Technol., Vol. 48(16), pp 9745–9753

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