Chemistry 101
How Rising Carbon Dioxide Threatens
Acidification diagram.

Higher CO2 reduces a key ingredient in shells.

1. CO2 absorbed by seawater (H2O).

2. CO2 reacts to form carbonic acid; makes water more acidic (more hydrogen atoms).

3. Carbonic acid breaks down into bicarbonate and hydrogen ions (H+). Bicarbonate breaks down into more H+ and carbonate, key to organisms like oysters, clams, corals, and other marine organisms that make shells and skeletons. But as acidity increases, less bicarbonate changes into carbonate.

Higher CO2 causes shells to dissolve.

Calcium carbonate is the main building block in the shells of marine animals. As seawater becomes more acidic, calcium carbonate — and the shells — can dissolve.

Acidification & Oyster Shells in the Chesapeake Bay

In an estuary like the Chesapeake Bay, sources other than the atmosphere — like runoff of excess nutrients — may add additional CO2 to the water, contributing to acidification. Evidence suggests that higher acidity in the Bay could slow the rate of growth in the shells of young oysters, making them thinner and more vulnerable to predators.

For Further Information
NOAA Pacific Marine Environmental Lab. Carbon Program. [website]
The Geological record of ocean acidification. Bärbel Hönisch et al. Science Magazine. March 2, 2012. [website]
Shellfish face uncertain future in high CO2 world: influence of acidification on oyster larvae calcification and growth in estuaries. A.W. Miller, A.C. Reynolds, C. Sobrino, and G.F. Riedel. PLoS ONE 4(5):e5661, 2009.
Biocalcification in the Eastern Oyster (Crassostrea virginica) in relation to long-term trends in Chesapeake Bay pH. George G. Waldbusser, Erin P. Voigt, Heather Bergschneider, Mark A. Green, and Roger I. E. Newell. Estuaries and Coasts 34:221-231, 2011.
Marine calcifiers exhibit mixed responses to CO2-induced ocean acidification. Justin B. Ries, Anne L. Cohen, and Daniel C. McCorkle. Geology 37(12): 1131-1134, December 2009.
Anticipating ocean acidification's economic consequences for commercial fisheries. Sarah R. Cooley and Scott C. Doney. Environmental Research Letters 4:024007, 2009. 8 pp.
Special Issue on the Future of Ocean Biogeochemistry in a High-CO2 World. Oceanography 22(4), December 2009. [website]
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