In this short video, Hoffman Lab Manager Anna MacPherson demonstrates with simple visuals how CO₂ dissolves into the ocean and lowers its pH. In her first experiment, she mixes an indicator dye — that turns blue when combined with a basic liquid and yellow in an acidic mixture — into ocean water before dropping in a chunk of frozen CO₂ (dry ice).
Right before your eyes, the blue, basic solution quickly turns yellow in an exaggerated albeit analogous representation of the chemical process. In her second experiment, MacPherson drops a piece of chalk — made of 100 percent calcium carbonate, the same substance clams, mussels, and oysters use to make their shells — into a solution of sea water plus acidic vinegar. Unsurprisingly, the chalk quickly disintegrates, paralleling the effect an overly acidic ocean has on its shelled creatures.