Carbon dioxide causes global warming, but it also is the reason behind another problem: ocean acidification. The ocean absorbs carbon dioxide that would otherwise contribute to global warming, but it’s not all good news. This additional CO2 changes water’s chemistry, making it more acidic, which will vastly alter marine life in the next several decades and force extinction of many species.

This problem has only been on scientists’ radar for the past five or so years, and much of the public remains unaware. Every day, approximately 22 million tons of carbon dioxide from the atmosphere is absorbed into ocean waters. Since the Industrial Revolution, humans have increased ocean acidity by 30 percent, and it’s expected to double by the end of the century.

Many marine organisms — from corals to mollusks, such as the above Limacina helicina — collect calcium ions and carbonate ions to form their shells and exoskeletons, but growing acidity of the water has greatly decreased the abundance of this molecule and with it the ability to calcify shells. In addition, acidic waters can dissolve these creatures’ existing shells. Waters off Southern California are already acidic enough to dissolve shells, and it’s expected that most waters will reach this point within a few decades. This rapid change will not leave enough time for most, if any, species to adapt.

Part of Tyrrhenean Sea off the coast of Italy provides an example of how acidity will affect waters by 2100. The sea features volcanic vents that produce a great amount of CO2, and now essentially all that can survive in the deepest waters are jellyfish, sea grass and algae. Even barnacles, which are very hardy, are unable to survive in some parts of the sea.

The full impact of acidification remains unclear, but scientists theorize it will result in extinction of many species, beginning with the smallest, weakest creatures and working up the food chain. In addition, acidification will likely affect ocean sound absorption and allow more sunlight into the water, which could harm phytoplankton.

Main photo credit: Russ Hopcroft, University of Alaska, Fairbanks/NOAA

Video credit: Natural Resources Defense Council

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