Ocean Acidification Process

Carbon dioxide (CO2) emissions from burning fossil fuels are making the world’s oceans more acidic. About half of all the CO2 that has been pumped into the atmosphere since the beginning of the industrial era, 250 years ago, has been absorbed by the oceans through natural processes. In the water, CO2 reacts to form carbonic acid, and over the years, the ocean’s acidity has increased by 30 percent because so much of the excess man-made CO2 is being drawn into the water. This increased acidity changes the balance of other carbon-species in the water, including carbonate.

These changes in ocean chemistry may have far-reaching ramifications. Some marine species that use a form of carbonate to build their skeletons and shells, like corals and mollusks, may be harmed because the acid formed in the water consumes this carbonate and makes it less accessible to these organisms. The more CO2 that is absorbed into the ocean, the more limited carbonate supplies will be in the future and the more difficult it will be for corals to sustain themselves.

If CO2 levels in the atmosphere continue to rise, scientists anticipate that some coral reefs could begin to dissolve away within the next 50 years. For other types of species, it is not yet clear how ocean acidification will affect them. Some, like jellyfish or sea grasses may benefit, but others, like the fish that thrive in coral communities, are expected to suffer. What’s clear, however, is that the entire marine ecosystem is expected to change if the ocean’s acidity continues to climb.

Graphic credit: John MacNeill