Some of the consequences of ocean acidification appear obvious: The shells of mollusks, for instance, could dissolve as the pH of ocean water drops thanks to the ocean pulling out some of the excess carbon dioxide humans put into the atmosphere. But what about more subtle effects of seawater growing more acidic?
In the Proceedings of the National Academy of Sciences this week, researchers set up an experiment to see whether the growing acidity of the ocean could disrupt the marine cycle of nitrogen, which provides key nutrients for plant life. Indeed it can, J. Michael Beman’s team found, and that’s another potentially dangerous side effect of the ocean as a carbon sink.
The authors of the study examined a specific step in the marine nitrogen cycle, called nitrification, in which microorganisms convert one form of nitrogen, ammonium, into nitrate, a form plants and other marine microorganisms require to survive. Previous research studies on experimentally acidified freshwater … in the laboratory have suggested that reduced pH slows nitrification, and one study in coastal ocean waters showed that large pH decreases did the same. [Scientific American]
So Beman sought to test the ocean by gathering samples of seawater from locations around the world and adding CO2 to simulate what will be happening to the oceans in the coming decades. Just decreasing the pH from 8.1 to 8.0 resulted in about 20 percent less nitrate creation, the team wrote. In their experiments that lowered pH between .05 and .14, the nitrate production dropped between 8 and 38 percent.
World carbon emissions fell by 1.3 percent in 2009, most likely due to the global recession, says a report from the Global Carbon Project published today in Nature Geoscience. Emissions were originally expected to drop further (about 3 percent, as estimated from the expected drop of world GDP), but China and India’s surging economies and increasing carbon output countered the decreases elsewhere.
The largest decreases occurred in Europe, Japan and North America: 6.9% in the United States, 8.6% in the U.K., 7% in Germany, 11.8% in Japan and 8.4% in Russia. The study notes that some emerging economies recorded substantial increases in their total emissions, including 8% in China and 6.2% in India. [USA Today]
There is some good news from the report. It seems the atmospheric CO2 concentrations didn’t jump as much as they were expected to, which means the world’s carbon sinks were performing better.
While emissions did not fall much, the amount of CO2 in the atmosphere increased by just 3.4 gigatonnes – one of the smallest rises in the last decade. Friedlingstein says the land and marine sinks performed better in 2009, because the La Niña conditions in the Pacific meant the tropics were wetter, allowing plants to grow more and store away more carbon. [New Scientist]