How many Tums are in the ocean? – Adam Subhas


A planktic foraminifera, species G. ruber.  This foraminifera is about 0.3 mm across, with spines that extend another 1 mm or so.  Both the shell and the spines are made of calcite, a form of calcium carbonate.  Foraminifera are animals, and must hunt their food.  Here it has caught a shrimp in its spines — a tasty lunch!  Image credit: A. Subhas and S. Oron

Heartburn, or acid reflux, has a common and simple remedy: take antacid tablets, which dissolve in your stomach and neutralize excess acid.  You may be asking yourself: what does this have to do with the ocean?  In fact, the ocean as a system uses antacids in exactly the same way.

Many marine organisms grow calcium carbonate shells, the active ingredient in TUMS.  These shells make up the basis of limestone rocks, and are abundant all over the world, and on the ocean floor.  The white cliffs of dover are made up of the “liths” of tiny algae known as coccolithophores; the pyramids of Giza were built with rocks chock-full of calcifying organisms known as foraminifera.

These rocks all got their start with microorganisms growing in the surface of the ocean, those organisms dying, and their shells settling to the ocean floor. As the world oceans become more acidic due to fossil fuel burning, these shells — the TUMS of the ocean — will dissolve back into seawater to neutralize the excess acid. I study this cycle of calcium carbonate formation and dissolution in the ocean, and how it regulates the ability of the ocean to take up and release CO2.

One fun fact: The ocean holds 60 times more carbon in it than the atmosphere does.  This is because of the large buffering capacity of seawater, which is regulated by the formation and dissolution of calcium carbonate shells in the ocean.  The amount of buffering capacity, or alkalinity, in the ocean, is equivalent to about 200 billion billion dissolved TUMS tablets — yes, that’s right, two times ten to the power of 20 TUMS tablets.  And yet — even with all of that buffering capacity, we are still changing ocean pH by burning fossil fuels.

On this cruise, I am collaborating with my colleague, B.B. Cael, to test how adding alkalinity will affect organisms growing in the open ocean.  Depending on what we find, we will better understand how alkalinity affects the growth of marine organisms and their shells.  With enough research and experimentation, we may be able to add more alkalinity to the ocean to help counteract global warming and ocean acidification.

I am also studying the role the enzyme Carbonic Anhydrase plays in the formation and dissolution of organisms’ shells. This enzyme drastically speeds up reactions crucial for both calcification and calcium carbonate dissolution.  For instance, pteropods grow calcium carbonate shells, but also produce a lot of carbonic anhydrase.  Pteropod shells are abundant in the surface ocean, but dissolve very quickly once the organisms die.  It is possible that carbonic anhydrase is catalyzing this dissolution reaction, and I hope to measure enzyme activity to link its presence to this dissolution reaction.


Volume of the oceans: 1.332 billion cubic km = 1.332e21 cubic dm, dens is 1.025 kg/dm3, alk = 0.0022 eq/kg, mass of caco3 in tums is 0.75g, or 0.015 eq alk per tablet, so we get 2.0e20 tums tablets in the ocean