Ocean Acidification Will Make Climate Change Worse

[n2doc]

By Bryan Walsh

Given that they cover 70% of the Earth’s surface—and provide about 90% of the planet’s habitable space by volume—the oceans tend to get short shrift when it comes to climate change. The leaked draft of the forthcoming coming new report from the Intergovernmental Panel on Climate Change highlighted the atmospheric warming we’re likely to see, the rate of ice loss in the Arctic and the unprecedented (at least within the last 22,000 years) rate of increase of concentrations of greenhouse gases like carbon dioxide and methane. But when it came to the oceans, press reports only focused on how warming would cause sea levels to rise, severely inconveniencing those of us who live on land.

Some of that ignorance is due to the out of sight, out of mind nature of the underwater world—a place human beings have only seen about 5% of. But it has more to do with the relative paucity of data on how climate change might impact the ocean. It’s not that scientists don’t think it matters—the reaction of the oceans to increased levels of CO2 will have an enormous effect on how global warming impacts the rest of us—it’s that there’s still a fair amount of uncertainty around the subject.


But here’s one thing they do know: oceans are absorbing a large portion of the CO2 emitted into the atmosphere—in fact, oceans are the largest single carbon sink in the world, dwarfing the absorbing abilities of the Amazon rainforest. But the more CO2 the oceans absorb, the more acidic they become on a relative scale, because some of the carbon reacts within the water to form carbonic acid. This is a slow-moving process—it’s not as if the oceans are suddenly going to become made of hydrochloric acid. But as two new studies published yesterday in the journal Nature Climate Change shows, acidification will make the oceans much less hospitable to many forms of marine life—and acidification may actually to serve to amplify overall warming.

The first study, by the German researchers Astrid Wittmann and Hans-O. Portner, is a meta-analysis looking at the specific effects rising acid levels are likely to have on specific categories of ocean life: corals, echinoderms, molluscs, crustaceans and fishes. Every category is projected to respond poorly to acidification, which isn’t that surprising—pH, which describes the relative acidity of a material, is about as basic a function of the underlying chemistry of life as you can get. (Lower pH indicates more acidity.) Rapid changes—and the ocean is acidifying rapidly, at least on a geological time scale—will be difficult for many species to adapt to.



Read more: http://science.time.com/2013/08/26/ocean-acidification-will-make-climate-change-worse/

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1. Scientists analyse the extent of ocean acidification

http://www.awi.de/en/news/press_releases/detail/item/scientists_analyse_the_extent_of_ocean_acidification/?cHash=0e993a4bd58402ffb904554908337ea3

[font face=Serif]25. August 2013:[font size=5]Scientists analyse the extent of ocean acidification[/font]

[font size=4]Bremerhaven, 22 August 2013. Ocean acidification could change the ecosystems of our seas even by the end of this century. Biologists at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), have therefore assessed the extent of this ominous change for the first time. In a new study they compiled and analysed all available data on the reaction of marine animals to ocean acidification. The scientists found that whilst the majority of animal species investigated are affected by ocean acidification, the respective impacts are very specific. The AWI-researchers present their results as an Advance Online Publication on Sunday 25 August 2013 in Nature Climate Change.[/font]

[font size=3]The oceans absorb more than a quarter of anthropogenic carbon dioxide emitted to the atmosphere. They form a natural store without which the Earth would now be a good deal warmer. But their storage capacities are limited and the absorption of carbon dioxide is not without consequence. Carbon dioxide dissolves in water, forms carbonic acid and causes the pH value of the oceans to drop – which affects many sea dwellers. In recent years much research has therefore been conducted on how individual species react to the carbon dioxide enrichment and the acidifying water. So far the overall extent of these changes on marine animals has been largely unknown.

In order to gain an initial overview, Dr. Astrid Wittmann and Prof. Hans-Otto Pörtner from the Alfred Wegener Institute, Helmholtz-Centre for Polar and Marine Research (AWI), surveyed all studies so far conducted which dealt with the consequences of ocean acidification for marine species from five animal taxa: corals, crustaceans, molluscs, vertebrates such as fishes and echinoderms such as starfish und sea urchins. By the end they had compiled a total of 167 studies with the data from over 150 different species. In order to classify these results they used emission scenarios for carbon dioxide on which the world climate report is also based. These scenarios allow to forecast the impacts of different carbon dioxide concentrations in the atmosphere far into the future.

The results of this new assessment are clear. “Our study showed that all animal groups we considered are affected negatively by higher carbon dioxide concentrations. Corals, echinoderms and molluscs above all react very sensitively to a decline in the pH value”, says Dr. Astrid Wittmann. Some echinoderms such as brittle stars have lower prospects of survival in carbon dioxide values predicted for the year 2100. By contrast, only higher concentrations of carbon dioxide would appear to have an impact on crustaceans such as the Atlantic spider crab or edible crab. However, the sensitivity of the animals to a declining pH value may increase if the sea temperature rises simultaneously.

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http://dx.doi.org/10.1038/nclimate1982