Shellfish to the Rescue!

Reducing Ocean Acidification by Recycling Bivalve Shells

I love the ocean! When not swimming or surfing, I go beachcombing for shells, coral, and sea glass. While comparing shell collections, I noticed that the shells collected by my mother as a little girl were larger, thicker, stronger and glossy while mine were smaller, thinner, fragile and chalky. I wondered, was it because the shells came from different oceans? Or had something in the oceans changed to cause this?

While reading about oceans and their changing chemistry, I came across anthropogenic CO2 induced ‘Ocean Acidification’ and its effect on calcifiers (creatures that use carbonate and calcium ions dissolved in seawater to construct their shells and skeletons) at the bottom of the marine food chains. Anthropogenic CO2 produced by the burning of fossil fuels is being absorbed by our oceans making them more acidic and reducing the availability of carbonate to marine calcifiers to form their shells and skeletons, disrupting marine food chains and threatening to trigger a chain reaction affecting the health of the planet and all its inhabitants.

Corals and Bivalves (oysters, clams, scallops, and mussels) create their shells from Aragonite. Aragonite is the metastable form (remains unchanged only at small disturbances in temperature and pressure) of calcium carbonate (CaCO3) that is 1.5 times more soluble in seawater than the stable form, Calcite. Clam, scallop, and mussel shells are made up of a combination of Aragonite and Calcite while the oyster shell is mainly made up of Calcite.

I conducted an experiment to study the effect of Ocean Acidification on corals and how it could be set off by recycling bivalve shells post-human consumption. I tested the most common shellfish (oyster, clam, scallop, and mussel) consumed by humans to investigate if recycling bivalve shells, through a Shell Recycling Program, can reduce the corrosive effect of Ocean Acidification on marine calcifiers by decreasing the decalcification of coral skeletons.

I took jars of acidified seawater with a pH of 7.8 (projected for 2100) and added a piece to coral to each. The experimental jars had oyster, clam, scallop and mussel shell powders while the control jars had either limestone power or just plain acidified seawater. I sealed up the jars and left them undisturbed for 60 days to see the effects of acidified seawater on the coral and how the calcium in powdered shell would or wouldn’t neutralize it.

From my experiment, I learned that clam shells were the best at reducing decalcification of the coral followed by scallop, oyster, and mussel shells by helping reduce the acidity of seawater like an antacid neutralizing stomach acid.

Future of life on Earth depends on the health of its oceans as they are its largest ecosystems and life support. It's painful to see so many species of marine life hovering on the brink of extinction. I passionately want to work towards the goal of making our oceans healthy again. I believe, we as a global community can make the right changes and choices to end ocean exploitation, pollution, and acidification before it's too late. I want the future generations to enjoy the beauty, witness the immense biodiversity and marvel at the vastness of our oceans like I do.