With increasing carbon dioxide concentrations in the atmosphere, levels are also increasing in the oceans, leading to ocean acidification. In recent years environmental scientists have been dedicating much effort to predict the fate of marine calcifiers, organisms which build their shells from calcium, under future ocean acidification scenarios. A team of European researchers used a range of new technologies to look at the molecules and cells involved in shell production of the Antarctic clam (Laternula elliptica).  Their results identified seven proteins from the lustrous mother of pearl shell layer, including two which were totally unique to this species.

A new study on the Antarctic clam (Laternula elliptica) explored how the animals build their shells to be so strong. The shells, here shown the inside and outside of the clam, consist of calcium carbonate which has to be taken out of the water in form of carbonate ions.
A new study on the Antarctic clam (Laternula elliptica) explored how the animals build their shells to be so strong. The shells, here shown the inside and outside of the clam, consist of calcium carbonate which has to be taken out of the water in form of carbonate ions.

When carbon dioxide dissolves in seawater it makes carbonic acid and the water becomes more acidic. In the past 200 years alone the acidity of our oceans has increased by 30 percent. This leads to a decrease of the available amount of carbonate ions in the water which marine calcifying organisms, such as coral and some plankton, use to form biogenic calcium carbonate as part of their shells. As a consequence these animals find it more difficult to produce stable shells and worse, their structures might become vulnerable to dissolution.

Recently a team of European scientists studied an Antarctic clam (Laternula elliptica). This large clam is found in coastal waters across the Southern Ocean, around the tip of Patagonia and all around the coast of Antarctica. It lives buried in mud in water below 0 °C and is therefore a valuable model to study the mechanisms of biomineralisation in cold water. It is also is a “keystone” species in the Southern Ocean benthic ecosystem.

The world oceans are getting more acidic. Shown here is the estimated change in sea water pH (a measure for acidity) caused by human created carbon dioxide between the 1700s and the 1990s, from the Global Ocean Data Analysis Project (GLODAP) and the World Ocean Atlas. Yellow and orange colours show an increase in acidity. (Picture: Wikipedia, Plumbago)
The world oceans are getting more acidic. Shown here is the estimated change in sea water pH (a measure for acidity) caused by human created carbon dioxide between the 1700s and the 1990s, from the Global Ocean Data Analysis Project (GLODAP) and the World Ocean Atlas. Yellow and orange colours show an increase in acidity. (Picture: Wikipedia, Plumbago)

The in-depth analysis of the cells, proteins and genes that Antarctic clams use to produce their shell, shows that the tools these animals use are very similar to other mollusc species. However, two unique proteins were found, suggesting these animals have special ways to help them carry out such complex bio-engineering at sub-zero temperatures.

Lead author Victoria Sleight from British Antarctic Survey (BAS) says: “We’re really excited by this study because we want to know in detail how shells are made. The ocean is becoming more acidic due to increased atmospheric carbon dioxide dissolving into the sea, so environmental scientists are urgently trying to predict what will happen to life with calcium carbonate skeletons.  In order to do this they need to understand how they are made in the first place.”

There is a remarkable diversity of seafloor fauna below the sea ice in Antarctica. The seafloor is teeming with a diverse and colourful array of fauna: Scallops, urchins, brittlestars, seastars, nemertean worms, sea slugs. Many different kinds of worms, shellfish and crustaceans live also in the seafloor sediments. (Picture: Pixabay, Skeeze)
There is a remarkable diversity of seafloor fauna below the sea ice in Antarctica. The seafloor is teeming with a diverse and colourful array of fauna: Scallops, urchins, brittlestars, seastars, nemertean worms, sea slugs. Many different kinds of worms, shellfish and crustaceans live also in the seafloor sediments. (Picture: Pixabay, Skeeze)

Aquaculture is also one of the fastest growing food production industries in the world, with molluscs making up around 22% by volume of global production, so understanding shell quality and integrity is crucial to this multi-million dollar industry. In addition, shells are also incredibly strong and made from a vastly abundant material – calcium carbonate, so if scientists can understand how molluscs build their shells then innovative new materials could be engineered and produced for society.

The study involved researchers from British Antarctic Survey (BAS) and Heriot Watt University in the UK, together with colleagues from the University of Göttingen in Germany and the Museum National d’Histoire Naturelle in France

The paper An Antarctic molluscan biomineralisation tool-kit by Vicky A. Sleight, Benjamin Marie, Daniel J. Jackson, Elisabeth A. Dyrynda, Arul Marie and Melody S. Clark was published in the journal Scientific Reports.

Source: British Antarctic Survey