Marine algae that turn carbon dissolved in seawater into shell will produce thinner and thinner shells as carbon dioxide levels increase.
Predicting how these algae, an important part of the carbon cycle, will react to rising CO2 levels has always been a puzzle. Now a team including Ros Rickaby from Oxford University’s Department of Earth Sciences, has found strong evidence that as CO2 concentration in seawater increases so calcification decreases and coccolith mass declines.
The new evidence comes from studies of half a million coccoliths from hundreds of seawater samples and ancient marine sediments cores taken from all over the world.
The research shows much greater variations in coccolith mass than previous lab-based studies, as, in the ocean, rising CO2 causes populations of algae to favour smaller, lightly calcified species over heavily calcified ones.
Further work is now needed to understand how the algae will respond to the changing marine environment and what impact a rise in thinner-shelled species will have on our oceans and the planet.