Since humans discovered the wonders of oil and coal, we’ve been sending a lot of the earth’s carbon stores up into the atmosphere again. As the amount of carbon in the atmosphere has increased, the earth’s oceans have taken in about a third of this carbon.
A recent study from San Francisco State University examines the potential impacts of these changes on tiny but critical ocean organisms: coccolithophores, a type of phytoplankton.
These organisms create calcium carbonate shells, and the relatively heavy shells allow them to sink into the deep ocean. They take with them the carbon that they store in their tissues, sending it to long term storage in the ocean’s carbon sink.
Even though they’re small, the coccolithophores’ ability to sink carbon into the ocean means that they play a vital role in the global carbon cycle.
The World’s Oceans Are Changing
The oceans are good at taking in both carbon dioxide and heat, and this is changing the acidity and temperature of the world’s oceans. Carbon dioxide from the atmosphere dissolves in ocean water, creating carbonic acid. This process makes the ocean more acidic. As the temperatures in the atmosphere rise, the global ocean temperatures will likely rise as well. Just how much the acidity and temperature will change is uncertain, since the earth’s oceans and atmosphere are complex systems, and many factors interact to change the temperature and acidity of the ocean.
Acidic Oceans: How Will Changes Impact Coccolithophores?
Will an increasingly acidic ocean make it harder for tiny ocean organisms to create their calcium carbonate shells? If you put calcium carbonate and an acid together, the acid usually reacts with the calcium carbonate. Decoded Science spoke with Jonathon Stillman, an associate professor of biology at San Francisco State University to discuss this situation. Stillman has been studying the shell formation of coccolithophores, placing them in different scenarios designed to anticipate the conditions in our future oceans.
Temperature, Nutrients, and Acidity Impact Phytoplankton
In the first study, Stillman studied coccolithophores in high and low carbon dioxide environments. He thought that the ones in the high carbon dioxide environment would create weaker shells, and he was right. If he’d stopped there, he might have projected that in the future, higher carbon dioxide levels would lead to thinner shells, which would mean that the coccolithophores would not sink into the ocean as easily.
However, the results of the second experiment were surprising. In this experiment, the research group added the variable of temperature. What would happen if the cells were exposed to the warmer temperatures and higher carbon dioxide concentrations that could occur in future oceans? Intriguingly, instead of struggling to build shells, the coccolithophores grew thicker shells over many hundreds of generations.