Ocean AcidificationReid Bergsund and Catherine Philbin

Problem Ocean absorbs about

1/3 of excess atmospheric CO2

Carbonate buffer system regulates ocean pH

Lower ocean pH inhibits calcification for organisms with CaCO3 shells

Ocean absorption of atmospheric CO2 is causing the rate of acidification to increase

Healthy Coral Reef

Ocean Chemistry 101—RealClimate

Carbonic acid dissociates and forms bicarbonate (HCO3

-) and carbonate (CO3

2-) and excess hydrogen ions (H+)

An increase in hydrogen ions (H+) results in lowering the pH

Increasing CO2 decreases carbonate ions and inhibits the calcification reaction

Equilibrium reaction for CO2 in water

Calcification reaction

CO2 + CO32- + H2O ⇔ 2HCO3

-

Ca2+ + CO3

2- ⇔ CaCO3

Ocean Acidification Review—Doney, et al (2009)

Understanding impacts of acidification has only been demonstrated in short-term experiments

Many questions surround organisms’ ability to adapt to increasing CO2 levels

Marine ecosystems are delicate and could be significantly affected by changes in the ocean’s chemical composition

Organisms’ responses varied to laboratory ocean acidification

Some Species May Benefit From Ocean Acidification—Iglesias-Rodriguez, et al (2008)

Exponentially grew coccolithophore and bubbled air containing various levels of CO2 through the culture mediums

Coccolithophore calcification and body volume significantly increased with high levels of aqueous CO2

Technical comment questions experimental methods

Question to Keep in Mind How does increased atmospheric CO2 lower

ocean pH? What chemical processes are affected by

increased ocean CO2 uptake? What are the implications of demonstrating

short-term experiments vs. long-term? Historically, how have ocean biota

responded to ocean acidification? How will ocean biota respond to an

unprecedented acceleration in ocean acidification?