What is ocean acidification?
Ocean acidification reduces the amount of carbonate in the sea, affecting organisms whose bodies are made of calcium carbonate (like animals with shells and hard exoskeletons). This includes, Molluscs (sea snails, mussels, octopus) ,Echinoderms (star fish and sea urchins), Crustaceans (crabs, lobsters, plankton and krill) and Corals.
If there isn’t enough carbonate these organisms won’t be able to form properly, which could be really bad news. This is already happening to the Dungeness crab in the Pacific Ocean. Not only are all these animals important in their own right, they are vital in maintaining a healthy ocean ecosystem. Corals create homes for 1 million marine species, and the other organisms (especially krill, plankton and molluscs) make up the base of the marine food web, supporting all life above them, right up to enormous whales.
Let’s break down the chemistry of ocean acidification. pH is measured on spectrum. The lower values (0-6) are acidic, 7 is neutral, and high values (8-12) are alkaline. Seawater currently has a pH of 8.1 making it slightly alkaline. As more carbon is stored in the sea, the pH drops, shifting it towards pH neutrality. When carbon dioxide enters the water, it bonds with water to create carbonic acid. This carbonic acid bonds with carbonate in the water creating bicarbonate. This is what makes the water more acidic and is how levels of naturally-occurring carbonate begin to fall, which is where the problems start.
In our experiment we will create a magic pH indicator which you can use to test the acidity of seawater (or any liquid at home) using the humble red cabbage. So let’s get stuck in!
Written by Juliet Maxted, Zoology graduate and Booth Museum volunteer
Find out more in Climate Conversations a Royal Pavilion & Museums blog series on Climate Change and what we can do about it.