November 2013: Ocean acidification may increase by a staggering 170 percent by 2100 says an international report led by the International Geosphere-Biosphere Programme, and marine ecosystems and biodiversity are likely to irreversibly change as a result with far-reaching consequences. The legacy of historical fossil fuel emissions on ocean acidification will be felt for centuries.
One of the lead authors Ulf Riebesell of GEOMAR Helmholtz Centre for Ocean Research Kiel said: "What we can now say with high levels of confidence about ocean acidification sends a clear message. Globally we have to be prepared for significant economic and ecosystem service losses. But we also know that reducing the rate of carbon dioxide emissions will slow acidification. It was emphasised by the experts that if society continues on the current high emissions trajectory, cold water coral reefs may become unsustainable and tropical coral reef erosion is likely to outpace reef building this century.
However, significant emissions reductions to meet the two-degree target by 2100 could ensure that half of surface waters presently occupied by tropical coral reefs remain favourable for their growth.
Fellow author Wendy Broadgate, Deputy Director at the International Geosphere-Biosphere Programme, said: "Emissions reductions may protect some reefs and marine organisms but we know that the ocean is subject to many other stresses such as warming, deoxygenation, pollution and overfishing. Warming and deoxygenation are also caused by rising carbon dioxide emissions, underlining the importance of reducing fossil fuel emissions. Reducing other stressors such as pollution and overfishing, and the introduction of large scale marine protected areas, may help build some resilience to ocean acidification."
A tipping point in ocean acidification is happening off the US west coast. Pteropods are critical to the ocean's carbon cycle, specifically its ability to sequester CO2. These tiny snails build shells which include carbon, and when they die the shells fall to sediments below, to be buried. And they're food for the fish you eat.
with signs that shells are dissolving.
Biologists have found the first evidence that acidity of continental shelf waters off the U.S. West Coast is dissolving the shells of tiny free-swimming marine snails, called pteropods, which provide food for pink salmon, mackerel and herring,...
"Our findings are the first evidence that a large fraction of the West Coast pteropod population is being affected by ocean acidification," said Nina Bednarsek, Ph.D., of NOAA's Pacific Marine Environmental Laboratory in Seattle ... These nearshore waters provide essential habitat to a great diversity of marine species, including many economically important fish that support coastal economies and provide us with food."
"We did not expect to see pteropods being affected to this extent in our coastal region for several decades," said William Peterson, Ph.D., an oceanographer at NOAA's Northwest Fisheries Science Center... [emphasis mine]
New research indicates that we're acidifying our oceans ten times faster than during the PETM extinction.
During the Paleocene-Eocene Thermal Maximum (PETM), "surface ocean acidity increased by about 100 percent in a few thousand years or more". In the past 150 years we've already decreased the pH by 25%.
Some 56 million years ago, a massive pulse of carbon dioxide into the atmosphere sent global temperatures soaring. In the oceans, carbonate sediments dissolved, some organisms went extinct and others evolved. Now, for the first time, scientists have quantified the extent of surface acidification from those ancient days, and the news is not good: the oceans are on track to acidify at least as much as they did then, only at a much faster rate.
In a study published in the latest issue of Paleoceanography, the scientists estimate that surface ocean acidity increased by about 100 percent in a few thousand years or more, and stayed that way for the next 70,000 years. The study is the first to use the chemical composition of fossils to reconstruct surface ocean acidity at the Paleocene-Eocene Thermal Maximum (PETM), a period of intense warming on land and throughout the oceans due to high CO2. In the last 150 years or so, the pH of the oceans has dropped substantially, from 8.2 to 8.1—equivalent to a 25 percent increase in acidity. By the end of the century, ocean pH is projected to fall another 0.3 pH units, to 7.8. While the researchers found a comparable pH drop during the PETM—0.3 units—the shift happened over a few thousand years.
"If we continue on the emissions path we are on right now, acidification of the surface ocean will be way more dramatic than during the PETM." Ocean acidification in the modern ocean may already be affecting some marine life, as shown by the partly dissolved shell of this ... pteropod, caught off the Pacific Northwest. [emphasis mine]