Some alarming discoveries


When CO2 dissolves in seawater, it forms carbonic acid. The carbonic acid level in the ocean is rising along with the increasing concentration of carbon dioxide in the atmosphere.


Interested in trying an experiment at home or at school to see how CO2 makes carbonic acid? Visit C-MORE's Teachers' Zone

The ocean is Earth’s largest biome. It can be hard to imagine that humans have any impact on the sea at all. But we do.

Increasing carbon dioxide, increasing acid

Since the 1950s, scientists have been taking atmospheric carbon dioxide measurements from the top of Mauna Loa. The data show both an annual cycle (due to varying degrees of photosynthesis over the course of a year) and an overall increase.

Some CO2 comes from natural sources—volcanic activity, organic decay, fires, etc. But humans also release CO2 into the atmosphere when we burn fossil fuels, and some of this atmospheric carbon dioxide dissolves in the ocean. Since October 1988, scientists have been measuring the concentration of CO2 in the sea (along with lots of other things re: ocean biogeochemistry), and have made two important discoveries:

  1. The CO2 concentration is, as expected, rising in the oceans as well as in the atmosphere.
  2. Ocean pH levels are decreasing, indicating the ocean is becoming more acidic.

The threat of an acidic ocean

When carbon dioxide dissolves in water, it forms carbonic acid (CO2 + H2O = H2CO3), which can dissolve calcium carbonate, the mineral that forms the shells and skeletons of many shellfish and corals. This phenomenon is known as ocean acidification. And, because many of them contain calcium carbonate, acidification also threatens the tiny, single-celled ocean creatures that make life on Earth possible.