If we increase aquaculture and grow more shellfish, won?t the shells help lock up carbon dioxide (like trees)?
The calcification process does take up carbon, but it causes shifts in the carbon system in seawater that result in a lower pH and an increase in CO2 rather than its removal. Many organisms convert bicarbonate to the carbonate they use to build their shells, and this produces hydrogen ions, thus increasing acidification. Most coral reefs, for example, on the time scales we are interested in, are small sources of CO2 to the atmosphere rather than sinks. From an ecosystems point of view, even well-intended aquaculture could cause unintentional harm by altering coastal landscapes, increasing pollution and disease, or releasing genetically altered or foreign species into the environment. Any activity aimed at reducing ocean acidification should be considered in a wider context to avoid replacing one environmental impact with another.
