Ocean Acidification

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Acidification in our Oceans

Oceanography
April 2, 2013

What is Ocean Acidification? “Ocean Acidification, is the worldwide reduction in the pH of seawater as a consequence of the absorption of large amounts of carbon dioxide (CO2) by the oceans.” (Britannica). Ocean acidification is largely the result of loading Earth’s atmosphere with large quantities of CO2, produced by vehicles and industrial and agricultural processes. Since the beginning of the Industrial Revolution about 1750, roughly one-third to one-half of the CO2 released into Earth’s atmosphere by human activities has been absorbed by the oceans. During that time period, scientists have estimated, the average pH of seawater declined from 8.19 to 8.05, which corresponds to a 30 percent increase in acidity. (Britannica).

Henry’s Law states “the weight of a gas dissolved by a liquid is proportional to the pressure of the gas upon the liquid” (Brittanica). In the preindustrial age the ocean released excess Carbon Dioxide to orchestrate the balance of the CO2 in the atmosphere with the CO2 in the ocean. Though we have dramatically increased our CO2 emissions, Henry’s Law still holds true. The difference is that now instead of the ocean releasing excess CO2, the ocean is absorbing CO2. At one point in time we thought this was great news. It worked wonderfully to soak up a lot of the greenhouse gases we were spewing out from our plants and automobiles and keep them from eating away at the atmosphere that protects us. We thought it was so great, in fact, that along with Germany and Japan we even considered capturing CO2, liquefying it, and pumping it into the ocean to make it disappear forever. It only took a couple experiments to realize that was not a good idea. As infinite as our deep blues seem, they can only absorb so much CO2 before it becomes a problem. “We found that mere absorption of CO2 from the atmosphere into the ocean was enough to harm marine creatures,” says Ken Caldeira, a chemical oceanographer now at the Carnegie Institution of Washington in Stanford, California.

When carbon dioxide gas dissolves into seawater, it makes the water more acidic. At the same time, the increasing concentration of dissolved carbon dioxide reduces the concentration of dissolved calcium carbonate that is available for marine life.

These two combined effects are a serious problem for small shelled creatures called pteropods. The decrease in the amount of carbonate ions that they use to make their shells means their shells will be weaker and will make them more susceptible to predators. Furthermore, the more acidic water erodes away the pteropods’ already small, weak shell. If you are like the majority of the population, you will probably ask “What does this mean to me and why should I care?”

After acidification has destabilized one species or ecosystem, the damage could ripple up and down the food chain. Especially worrisome is the fact that the shelled plankton under threat are efficient at storing CO2. When the creatures that eat the plankton die, their shells and organic remains fall to the ocean floor, sequestering carbon in the deep water and sediments. “Cold-water plankton are powerful allies in preventing atmospheric CO2 from climbing higher than it already is,” says David Hutchins, a biological oceanographer at the University of Southern California in Los Angeles. Therefore, their rapid decline could quickly turn the planet hotter. “Currently the ocean is a sink for CO2, that is, it takes in more CO2 from the atmosphere than it releases,” Hutchins explains. “But a warming and acidifying ocean could become a net source of CO2.” In other words, the world’s seas could begin releasing an increasing amount of the gas into the atmosphere, just like we are doing with our cars and power plants every day.

The most commonly known effect of the acidification of the ocean is the “bleaching” of the coral reefs. “Today’s reefs are as much as 5,000...
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