Ocean acidifiwhat?

So, welcome to a bumper week of blogging! You may have seen that last week I didn’t manage to post a blog. It was a productive week in other ways, however that is no excuse so I apologise and to make up for it, this week I will be running a whole series of blogs that I am going to dedicate to ocean acidification.

I thought I would start this by running through what ocean acidification and how it is related to climate change.

So, from the name it should come as no surprise that ocean acidification is just that, the ocean becoming more acidic. This is occurring because the ocean absorbs CO₂ from the atmosphere, and since the amount of CO₂ in the atmosphere has increased, so has the amount being absorbed by oceans. According to Ocean Acidification International’s paper on the knowledge base we have about ocean acidification, the ocean absorbs 25% of the CO₂ in the atmosphere.

This paper presents key facts about ocean acidification very clearly, including how the CO₂ entering the ocean actually makes it acidic. The diagram below, featured on page 3 of the paper. I’ve also added the full actual equation below it, for those of you who are more scientifically inclined.

CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃^- ⇌ 2 H⁺ + CO₃^2-

The increase in CO₂ in the atmosphere has caused the ocean’s acidity to increase by 30% (Guinotte and Fabry, 2008; Malakoff, 2012). The graph below, which I found in Doney et al’s influential 2009 paper on ocean acidification, illustrates the relationship perfectly.

The red line which represents atmospheric CO₂ at Mauna Loa (in parts per million) agrees with the brown line which represents partial pressure of CO2 at the ALOHA ocean station in the subtropical North Pacific Ocean. The blue line on the other hand represents surface ocean pH. This clearly shows that as atmospheric levels of CO₂ increase; the pH of the ocean decreases (i.e. becomes more acidic).

So, hopefully now you understand what ocean acidification is and how it is related to CO₂. My next blog will be about the impacts that ocean acidification is having on living organisms in the ocean. To give a lively end to this post, and give you with a taste of what is to come with the next, I really recommend you watch the video below. It’s a brilliantly entertaining short video about the consequences of ocean acidification, and was made by a group of children from Ridgeway School in Plymouth. It may not be deeply scientific, but it is certainly a great attention-grabbing introduction to the problem.