The acidity is caused by the gradual buildup of carbon dioxide (CO2) in the atmosphere, dissolving into the oceans. Scientists fear it could be lethal for animals with chalky skeletons which make up more than a third of the planet’s marine life.
“Recent research into corals using boron isotopes indicates the ocean has become about one third of a pH unit more acid over the past fifty years. This is still early days for the research, and the trend is not uniform, but it certainly looks as if marine acidity is building up,” says Professor Malcolm McCulloch of CoECRS and the Australian National University.
“It appears this acidification is now taking place over decades, rather than centuries as originally predicted. It is happening even faster in the cooler waters of the Southern Ocean than in the tropics. It is starting to look like a very serious issue.”
Corals and plankton with chalky skeletons are at the base of the marine food web. They rely on sea water saturated with calcium carbonate to form their skeletons. However, as acidity intensifies, the saturation declines, making it harder for the animals to form their skeletal structures (calcify).
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Of course this is a very serious problem. The reason the ocean is becoming more acid is simple, the partial pressures of gases try to be at equilibrium between the ocean and the atmosphere, so as atmospheric CO2 goes up, much of it is getting dissolved into the oceans. In fact if the oceans were not so efficient as a carbon sink, the CO2 in the atmosphere might be twice as high! This poses a threat to calcareous animals including coral reefs which everyone loves. But another devastating impact is on a phytoplankton group known as coccolithophores, which secrete a calcium carbonate test, or shell. In this way they act as a double whammy for the carbon pump. Not only do they use CO2 to make cellular material, they also uses it for an outer coat. They are very important for the sequestration of carbon, and the loss of these phytoplankton could be devastating as well. Look them up for more info.