Coccoliths have been found to dissolve when seawater acidifies. Coccoliths are very small shells of calcium carbonate that encapsulate algae.
“The shell falls completely apart when we do experiments in water with a pH value that many researchers believe will be the found in the world oceans in the year 2100 due to the CO2 levels,” researcher Tue Hassenkamn said.
Read more at University of Copenhagen