Ocean Acidification, Life in an Acid Bath ELF Activity: Biosphere 4B As part of NOAA Environmental Literacy Grant #NA09SEC to the University of Nebraska–Lincoln's, ANDRILL Science Management Office. This material is based on work supported by an Environmental Literacy Grant from the National Oceanic and Atmospheric Administration's Office of Education (NA0909SEC ) and prior work supported by the National Science Foundation under Grants ANT and ESI Any opinions, findings, and conclusions or recommendations expressed in these materials are those of the authors and do not necessarily reflect the views of the NOAA or the NSF.

When carbon dioxide dissolves in water, it combines with the water molecule to form the bicarbonate ion. This acts as an acid which lowers the pH of the water.

It has been estimated that from 1751 to 1994, surface ocean pH has decreased from approximately pH 8.25 to pH This represents an increase approaching 30% in "acidity" in the world's oceans.

Many marine organisms combine the dissolved form of the mineral Calcium (Ca +2 ) and the carbonate ion (CO 3 -2 ) to create a protective covering (CaCO3) for their bodies. We see the results of this chemical reaction in the form of shells and coral reefs. ww.noaa.govww.nps.gov

For other animals the covering is less apparent but no less important. These small or microscopic marine creatures are an important part of the marine food chain; they create calcium shells for protection. Foraminifera Pteropod

Calcium carbonate is the protective body covering of marine organisms which we see as shells and coral reefs. It is also the compound found in ordinary classroom chalk, which is formed from the shells of dead marine animals and is similar to limestone. What do you think would happen to a shell placed in vinegar? Put a piece of chalk in household vinegar to see the effects of an acid on calcium carbonate. Try this in your classroom and see what happens.

When marine organisms die, their shells fall to the bottom of the ocean, carrying the carbon atoms with them. Over time, these sediment layers have provided a ‘reservoir ‘ of solid carbon, thus reducing the amount that is in the atmosphere as carbon dioxide. These cores reveal the difference in the layers, showing that the ocean environment has changed over time.

If you tried the demonstration with chalk and vinegar you saw that calcium carbonate dissolves in an acidic environment. As our oceans become more acidic it will be more difficult for marine organisms to create their shells and body coverings and keep the ones they have.

Coral reefs are created with carbonate compounds which are secreted by the tiny organisms that live in them. In some regions, the oceans have already become more acidic; this may reduce the growth of the coral reefs and dissolve the ones that are already there.

When organisms lose their protective covering they become vulnerable to predators. What do you think will happen to the population of shelled animals if the Earth’s oceans become more acidic? A question to ponder…

This material is based on work supported by an Environmental Literacy Grant from the National Oceanic and Atmospheric Administration’s Office of Education (NA09SEC ) and prior work supported by the National Science Foundation under Grants ANT and ESI Any opinions, findings, and conclusions or recommendations expressed in these materials are those of the authors and do not necessarily reflect the views of the National Oceanic and Atmospheric Administration or the National Science Foundation.