Ocean acidification

  Ocean Acidification Video Script

        A1. - Hello my name is Adam Housego and my colleague, Julien Vauloup and I are going to talk to you today about an emerging problem on our planet: ocean acidification.

        J1. - Yes, that’s right, ocean acidification is one of the major environmental problems on earth at the moment. But what is it you may ask ?

        A2. - Well, ocean acidification is generally referred to as the reduction in the pH of the ocean over an extended period of time caused mainly by the increase of carbon dioxide (CO2) in the atmosphere. It is one of the consequences of living in a world where there is lots of CO2 and it is also now nicknamed as the “evil twin of climate change”.

        J2. - You may also be thinking what is pH, but we’ll explain it for you now. pH is a figure expressing the acidity or the alkalinity of a solution on a logarithmic scale on which 7 is neutral. It symbolizes the hydrogen ion concentration in a solution. Lower values than 7 are more acid and higher values than 7 are more alkaline.

        A3. - The pH is equal to -log[H+] where H is the hydrogen ion concentration in moles per litre. [H+] is equal to 10^-pH. The concept of pH was first introduced by a Danish chemist called Soren Peder Lauritz Sorensen at the Carlsberg Laboratory in 1909.

        J3. - In order to show you how it works, we decided to do an experiment. We started off my measuring the pH of seawater and of salty water in normal conditions thanks to a pH metre. Then, we decided to add CO2 by blowing into a straw into the water containers to see if the acidity of the seawater increased or decreased after blowing CO2 into it.

        A4. -We observed that after we blew into the container for a couple of minutes, the acidity of the water went down slightly. We tried more than once to make sure that is wasn't just a one-off. This shows that the by adding CO2, the pH decreases, the oceans are therefore moving towards a more acidic state and less alkaline state.

        This graph shows us how once the atmospheric carbon dioxide enters the ocean we obtain hydrogen ions and carbonate ions. As we explained earlier, the more hydrogen ions there are the more the pH is low and the more the ocean is acidic. On the contrary, if hydroxyde ions are formed then the solution will be more alkaline.

        - When the CO₂ enters the ocean, it reacts with water and forms this equation: CO₂ (aq) + H₂O ↔ H₂CO₃ (aq). The reaction takes quite a long time but in the end it forms carbonic acid. H₂CO₃ may loose up to two protons through this acid equilibria: H₂CO₃ (aq) ↔ H+ (aq) + HCO₃- (aq). This reaction creates hydrogen ions and biocarbonate ions. Equally, the biocarbonate ions can form carbonate ions and more hydrogen ions through this reaction: HCO₃- (aq) ↔ H+ (aq) + CO₃²- (aq). We can observe that when the CO₂ enters the ocean, there are lots of hydrogen ions that are formed. This means that the ocean is getting more acidic. Ocean pH has already decreased by 30%, this means that if we continue emitting CO₂ at this rate, ocean acidity will increase by 150% by the year 2100.  Around one third of the CO₂ from human activity is released into oceans, seas, lakes and rivers.

        J4. - The rise of the ocean acidity has a big impact on the environment. A number of different species of plants and animals are suffering because of it. For example, when the pH goes below 4,5 out of 14, fish will die because the ocean is far too acidic. Some scientists believe ocean acidification will affect entire ecosystems. That includes one animal that is at the top of the food chain, us humans. Humans rely on the ocean for food and other economic resources. Ocean acidification will in the end not only affect just marine life but also humans. As it reduces the amount of fish and sea creatures in the ocean, there will be less fish on the food market and therefore fish will probably become more expensive.

        A5. - Another impact that CO2 emissions have is bleaching. Yes, that's right, after I watched the BBCs Blue Planet II on the TV that talks about our oceans, one of the many phenomenons I saw was coral bleaching in the oceans. The world famous naturalist David Attenborough explained it in lots of detail.

        He tells us that the present increase in ocean acidity is not just unprecedented in our lifetime; it’s a rare event in the history of our planet. It will change the internal energetic balance of marine creatures. Animals will need to spend more energy controlling their internal pH leaving less energy for feeding, breeding… It also affects the sensory abilities of fishes and makes them behave unnaturally.