Earth Day 22nd April

​Tomorrow we will mark another Earth Day, and the theme for 2020 is climate action.  As divers, climate change is something we have been asked to participate in noting the effects of.

You will have learned the carbon cycle at some point in school, the ocean acts as a very large carbon sink. But what happens when the carbon is absorbed in to the ocean? Dissolved carbon dioxide in the ocean makes the ocean more acidic! 

Corals grow their skeleton through absorbing calcium carbonate from the sea water and allow it to harden. 

But where have you heard of calcium carbonate before?  It is probably in your medicine cabinet right now. Indigestion medications contain calcium carbonate because it neutralises the acid in your stomach. 

If the ocean is dissolving more carbon dioxide and becoming more acidic, then that means it will be neutralised by the same thing that should be making the coral skeleton.

Why does this matter?  Less coral means less biodiversity in our oceans, and if you read back to last week’s blog article then you know this will have detrimental effects on the food web. 
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How can you show your budding marine scientist?

Humans breath in oxygen and out carbon dioxide, so you can make water more acidic yourself! Show it by using red cabbage indicator:

Making indicator out of red cabbage 

1. Chop up the red cabbage and add hot water. For ¼ cabbage add approximately 400ml water (this doesn’t need to be exact)
2. Leave to soak until the water is purple (if you have a blender you can use this as well)
3. Strain out the solid cabbage so you are left with your purple indicator liquid
4. To cups or glasses, add different household substances (best not test the liquid soap or anything else in short supply!) e.g fizzy drinks, toothpaste, shampoo, vinegar, lemon juice…
5. Add some red cabbage indicator to each substance and record the colour it goes. 
6. Using the chart below decide whether your substances are acid, alkali, or neutral.

​Showing that dissolved carbon dioxide makes water more acidic:
Add some red cabbage indicator to water, it should already be a weaker acid.
Using a bamboo, glass, metal, or paper straw, gently blow bubbles in to the water.
You should see it getting more acidic.
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Want to do another test?
What happens if you put the sample with more carbon dioxide in it into a bag with a plant? 
What happens if you dissolve some salt into the water first?  Even more salt? 
If you have some indigestion tablets, crush them up, how much can you dissolve before it becomes an alkali? Does it matter how long you blew bubbles in to the solution?