By Frank J. Dinan
Most of the current concern about the ever-increasing concentration of carbon dioxide in the atmosphere has focused on global climate change. This is a serious problem, but carbon dioxide is also adversely affecting our oceans. Oceans cover 71 percent of the earth’s surface and, while they are unseen by most of us, they are critical to our well-being. The role that carbon dioxide plays in threatening them, however, receives scant attention.
Since the beginning of the Industrial Revolution in the late 18th century, mankind has pumped well over 500 billion tons of carbon dioxide into the atmosphere, raising its concentration there to 400 parts per million (ppm), higher than it has been in recorded history and nearly doubling its pre-industrial era concentration. Today we emit carbon dioxide so rapidly, over 38 billion tons per year according to CBS News, that its concentration may reach 500 ppm during this century.
Carbon dioxide in the atmosphere is in constant contact with ocean surface waters and readily dissolves there, forming carbonic acid. This process removes carbon dioxide from the atmosphere but continually adds acid to the oceans and steadily increases their acidity.
Ocean water is normally weakly basic, but constant reaction with carbonic acid causes it to become more acidic. Recent studies on ice cores show that the oceans’ surface waters are now about 30 percent more acidic than they were in 1800. At current carbon dioxide emission rates, they are certain to significantly increase in acidity.
Increased ocean acidity will have disastrous consequences for marine life, interrupting food chains and harming commercial fishing, but its greatest harm is likely to be done to coral reefs. Reefs are the home and shelter for marine species both great and small almost beyond number. These creatures thrive when the oceans are weakly basic but cannot do so in neutral or acidic waters.
Reefs are built by small marine organisms called calcifiers that capture calcium and carbonate ions from ocean water.
Carbon dioxide-generated carbonic acid reacts with and “gobbles up” calcium ions from acidic waters. Removing these ions prevents the growth of calcifiers and, therefore, of reefs. Australia’s Great Barrier Reef and lesser reefs worldwide are now shrinking and deteriorating in this way.
Unlike the questions surrounding carbon dioxide’s complex role in global warming, ocean acidification involves simple, straightforward chemistry and it is happening now. It has nothing to do with political ideology. Failure to reduce our carbon dioxide emissions is harming our oceans disastrously and will continue to do so until we find the courage to bite the bullet and change.
Frank J. Dinan is emeritus professor in the Chemistry and Biochemistry Department at Canisius College.