Ocean acidification kills coral reefs but helps tiny shellfish make better shells

The carbon dioxide in the air acidifies the oceans, and this acidification is believed to negatively affect shellfish and corals. However, new research suggests that unicellular shellfish can create better shells thanks to the more acidic environment.

Prior to this study, researchers believed that shellfish and corals find it harder to survive, because the process of chalk formation is more difficult in acidic seawater.

Ocean Acidification, Not Detrimental For Shellfish

The research, published Jan. 27, in the journal Nature Communications, was conducted by scientists at the Royal Dutch Institute for Sea Research (NIOZ) and the Japanese Agency of Marine-Earth Science and Technology (JAMSTEC). The team concluded, after having conducted a series of experiments, that the ocean acidification could make the shellfish shells even more vigorous.

The tiny shellfish are formed from one single cell and exist in large numbers in the seawater. However, since the acidity levels of the ocean have inflated by 30 percent since 1750, scientists were concerned about the well-being of these ocean creatures.

“Ongoing ocean acidification is widely reported to reduce the ability of calcifying marine organisms to produce their shells and skeletons. Whereas increased dissolution due to acidification is a largely inorganic process, strong organismal control over biomineralization influences calcification and hence complicates predicting the response of marine calcifyers,” noted the research.

The theory supporting the scientific concern regarding shellfish and their capacity to form their shells under acidic water is based on the chemical interaction of the elements involved in this process. Limestone, which is made of calcium carbonate, will dissolve more easily in acidic water, which implies that less carbonate will be available for shellfish.

As part of the experiments carried out in the study, the foraminifera regulated the acidity at a micro level; the acidity was significantly lower in those parts where shell formation took place compared to the rest of the seawater. Foraminifera produce large quantities of hydrogen ions through their cell walls, which leads to a higher acidity level in the near micro-environment.

“Our physical model for calcification shows the dependence of foraminiferal biomineralization on the various inorganic carbon species present in seawater. We validate the importance of pH regulation on the foraminiferal calcification by application of a V-type H+ ATPase inhibitor, which plays a key role in aragonite production in scleractinian corals,” also noted the research.

Adaptive Mechanism In Sea Organisms Could Speed Up Global Warming

This chemical reaction leads to an increase in the level of carbon dioxide at the expense of the carbonate. When this happens, the organisms immediately absorb the higher concentration of carbon dioxide through their cell walls, creating a lower acidity level on the inner side of the wall. Once this process is complete, the carbon dioxide is turned into carbonate once again, reacting with the existing calcium to form the lime.

“Such an active biochemical regulation mechanism has never been found before,” noted Lennart de Nooijer, NIOZ researcher and shared first author of the research.

According to the scientists, future research could be carried out as an attempt to validate the connection between the formation of carbon dioxide and its consequences on global warming. If most of the organisms can go through the same process as the foraminifera in the research, the concentration of dissolved carbon dioxide in the oceans would grow, which would conflict with the water’s ability to absorb the existing carbon dioxide in the air. Should this hypothesis be confirmed, this adaptive mechanism would speed up global warming.

Livia Rusu, Tech Times, 1 February 2017. Article.

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