Climate Change: Ocean Acidification

What Is Ocean Acidification?

Ocean acidification refers to the decrease in the pH of the ocean due to an uptake of atmospheric carbon dioxide (CO2). With the increase in CO2 emissions since the industrial revolution, there has also been an increase in ocean acidification. "Average ocean pH has already declined by 0.1 units since pre-industrial times and...ocean pH is predicted to decline another 0.3–0.4 units by 2100" (Dixson 2010).

How Does An Increase In CO2 Lead to Acidification?

Remember back to basic chemistry and imagine what might happen if the partial pressure of a gas is increased while the partial pressure within a body of water is unchanged. To reach equilibrium, the body of water will take up enough gas to equalize the partial pressures across the gradient. Much the same, the ocean began to take up more CO2 as anthropogenic influences caused the partial pressure of CO2 within the atmosphere to increase. Some of the absorbed CO2 reacts with water to form carbonic acid, which can dissociate into bicarbonate and hydrogen ions. This increases the amount of H+ in the ocean or, in other terms, it decreases the pH (Ocean Acidification PMEL, Ocean Acidification NRDC).

(http://www.pmel.noaa.gov/co2/files/pmel-oa-imageee_med.jpg)

What Happens if the Ocean is More Acidic?

Ocean acidification can have major consequences for broad categories of organisms. The most pressing concern is that increased acidification can negatively affect organisms that rely on calcification to build their physical frameworks. Organisms like corals, pteropods, shellfish and certain types of algae require proper calcification or else they will have reduced or weakened structures. Additionally, reduced pH can reduce the effectiveness of sensory systems of some fish.