Human carbon dioxide emissions have been increasing for centuries, which continues to have increasingly horrific effects on the world. One of the lesser-known effects is how these emissions are actually lowering the pH of the ocean, making it more acidic.
But how does this work?
The oceans are an important carbon sink and dissolve approximately 35% of the carbon dioxide that we emit. This then reacts with the water to produce carbonic acids, which then dissociate (split up) into bicarbonate and hydrogen ions. These H+ ions are responsible for lowering the pH of the oceans.
The key issue here is the effect this has on calcified organisms, for example, corals. When the hydrogen ions react with all the available carbonate ions, they reduce the amount of this crucial building material that these organisms depend on to create and maintain their shells.
Consequently, their shells weaken, and in cases of extreme acidification, they can even dissolve.
For example, there is a small sea snail called a pteropod that is eaten by many different organisms. In a laboratory experiment, pteropod shells were placed in seawater of a pH that is projected for 2100: they dissolved in a month and a half. If this occurs it could have global impacts on the food chain and biodiversity. Ocean acidification, along with rising ocean temperatures, is a prominent cause of mass coral bleaching, which also impacts food chains.
Written by Cara Hardwick
Artwork by Zara Masood
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