Ocean acidification: a shell game

PHOTO FROM WALL321.COM

Carbon dioxide from the atmosphere dissolve in the ocean water and combines with calcium to form calcium carbonated, which is needed to form shells. While some shelled marine organism increase their shell building, others partially dissolves in water with high carbon dioxide levels. In such waters, although there is more carbon available for shell formation, organism can only benefit if they can convert it into their shells and at the same time prevent their shells from dissolving in the more acidic water. Studies has found that different organism adapt differently in high carbon dioxide waters. While there is no observable change in shell building for large Caribbean snails, spines of pencil urchins dissolve to stumps in carbon rich waters. Other shell fishes' (oysters, clams and scallops) shell building rate decreases. 

The urchin on the left is gown in carbon dioxide water rich water whereas the the one on the right is gown in normal conditions (it is healthier with normal spines).

PHOTO BY TOM KLEINDINST

However, for certain crustaceans, it was tested that they grew heavier shells in carbon dioxide rich water. These species include American lobster, blue crab and a large prawn. 

American lobster grown in high carbon dioxide waters (right) grew larger and heavier shell as compared to those grown in normal conditions (left)

PHOTO BY JUSTIN RIES

As a result, ocean acidification will cause some species to thrive and benefit over others. The main concern is for species that are unable to adapt well to the change in ocean's acidity.

 " Given the complex relationships that exist among benthic marine organisms", said Ries, " it is difficult to predict how even subtle changes in organisms' abilities to calcify will ultimately work their way through these ecosystems."

-Kate Madin

This blog post is based on the report 'Ocean acidification: a risky shell game'

WHOI, 2010. Ocean acidification: a risky shell game. Oceanus magazine, [Online]. 48 (1), 6-7. Available at: http://www.whoi.edu/cms/files/OceanAcid_68964.pdf [Accessed 23 October 2014].