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LITMUS TEST Look at the ocean today. It probably looks the same as it did when you were a kid but as the old adage warns looks can be deceiving. You start to get some clues from our shorelines with evidence of erosion from higher tides. However it is beneath the surface within the shells of shellfish that a different story is unfolding ocean acidification. Since the industrial revolution the oceans pH has decreased from 8.2 to 8.1. The number 8.1 doesnt seem much dierent from 8.2. Not on a linear scale. But the dierence between a pH of 8.2 and a pH of 8.1 is quite signicant. pH a measure of the acidity of a liquid is measured on a log scale ranging from 0 acidic to 14 alkaline. Through a century of combusting fossil fuels we have managed to raise our oceans acidity by 26. Although ocean acidication has only become an important research topic in the last 20 years the basic chemistry to illustrate the phenomenon was well estab- lished over a century ago. When the concentration of CO2 the primary greenhouse gas from burning fossil fuels increases in the atmosphere CO2 is absorbed by the ocean at a predictable rate. Since the dawn of the industrial age oceans have absorbed about one-third of the CO2 that humans have emitted into the atmosphere. Climate change would be happening much faster without this help from the oceans. That the oceans provide this ecosystem service might be a good thing for humans but not for marine organ- isms. When carbon dioxide CO2 is absorbed by the ocean it reacts with water H2O to form carbonic acid H2CO3. Carbonic acid then breaks down and forms bicarbonate HCO3 - and hydrogen ion H . The addi- tion of hydrogen ions is what makes something more acidic. So putting more CO2 into the atmosphere leads to a higher concentration of H in the ocean and thus a lower pH score and a more acidic ocean. For marine organisms with shells or structures made of calcite e.g. clams mussels crabs lobsters corals this is a troubling chemical equation. Figure 1 Three photos of a clam taken after differing exposures to acidic mud. The first photo was taken while the clam was being reared in a controlled hatchery the second photo was after the clam spent one week in an acidic mud flat and the last photo was taken after the clam spent two weeks in the acidic mud flat. All of the photos were taken under the same magnifi- cation. Clam shows growth and obvious corrosion. Photos from Mike Doan Research Associate Friends of Casco Bay. Pre-deployment One week deployment Two week deployment HOW WERE CHANGING THE CHEMISTRY OF OUR OCEANS by John Hagan and Liza LePage WINTER 2014 MANOMET PARTNERSHIPS 7