Ocean Acidification: Eating Away at Life in the Southern Ocean
Key Points:
Ocean acidification is occurring as a result of carbon dioxide emissions from industrial activity dissolving into the oceans, and involves a fundamental change in the chemistry of the global oceans.
Perhaps the greatest challenge it presents to marine life that make their shells of calcium carbonate (chalk) is that it can make seawater so corrosive that their shells/skeletons begin to dissolve.
Bednarsek (2012) examined the shells of pteropods (sea butterflies) captured live from waters around Antarctica and found that, in low pH seawater, the shells of the creatures exhibited marked corrosion.
The presence of such highly corrosive water near the surface around Antarctica is a window into the future. Ocean acidification there will grow worse in time given current CO2 emission trends, and will pose a significant threat to the Antarctic marine ecosystem because the pteropod is a keystone species of the local food web.
Figure 2 - Although excluding the Polar regions and focused on coral reefs, this image displays the surface ocean aragonite saturation state estimated (modelled) for the pre-industrial (287ppm CO2), present (400 ppm), and two future scenarios based upon continued fossil fuel use. It gives some idea of the wholescale changes in ocean chemistry.From Ricke (2013).
As Predicted, Ocean Acidification is Bad
Not only do the results of Bednarsek (2012) validate the harmful consequences of aragonite undersaturation on pteropods observed in CO2-manipulated lab experiments, but they also underscore the fact that ocean acidification is happening today right under our noses. This is not some distant, abstract, threat to be palmed off onto future generations to deal with, this is something that can only (realistically) be minimised by reducing fossil fuel use now, or soon.
Indeed, despite the fact that not all marine calcifiers are directly harmed by acidification and we don't know exactly how bad this might turn out, enough key species are threatened (coral reefs for example) that business-as-usual fossil fuel use poses a significant threat to our way of life. The oceans have seen an increase in acidification of close to 30% since pre-industral times, and are probably now on course to acidify faster than they have in the last 300 million years (Caldeira & Wickett [2003], Honisch [2012], Zeebe [2012]). Given that emerging research is linking previous slower rates of ocean acidification with some of the major extinction events in Earth's history (Kump [2009], Payne & Clapham [2012],Hinjosa [2012]), now might be a good time to get serious about ocean acidification. Better late than never.
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Unprecedented ocean acidification from greenhouse gases putting Canadian waters at risk, says report
Canada’s Atlantic waters may be “particularly vulnerable” to increased carbon dioxide emissions in the atmosphere that are causing “unprecedented” acidification of the planet’s oceans, says a report by scientists at the Department of Fisheries and Oceans.
Quoting from numerous scientific publications, the government report, posted on a website without a formal announcement or news release, noted that the world’s oceans have absorbed a significant amount of carbon dioxide emissions from the atmosphere since the industrial revolution, with profound effects on marine ecosystems that could damage the Canadian economy.
The report, which focused on the Scotian Shelf region of Atlantic Canada, says that “adaptive measures coupled with a reduction in carbon dioxide emissions to the atmosphere will have to be pursued to protect ecosystems and human livelihoods against this phenomenon,” since it is not easy to reverse ocean acidification and its effects.
http://coinatlantic.ca/docs/ocean-acidification.pdf