It is increasingly well understood and publicised that human-generated carbon dioxide in the atmosphere is having an effect on our climate. However, not all of the CO2 released into the atmosphere stays there. In fact, about a quarter of it is absorbed into our oceans.
Carbon dioxide dissolves in water to form carbonic acid, and while the Earth’s oceans are massive, in the last 200 years the water in our oceans has become 30% more acidic. This represents the largest single change in ocean chemistry in over 50 million years. And the amount of CO2 that can dissolve in water increases with temperature, so combine rising concentrations of carbon dioxide in our oceans with rising sea temperatures and we have a reaction that is threatening the biodiversity of our oceans.
The effects that this changing pH have on sea life are only just being understood. Some organisms such as algae, may actually thrive in conditions of higher acidity. But organisms that rely on calcium carbonate for their shells and structures are already facing problems. One of the first studies of this involved Sea Butterflies – small molluscs with delicate shells. They were placed in sea water and the concentration of CO2 was slowly raised. After 45 days, the shells had mostly dissolved due to the rising carbonic acid levels.
Coral reefs are also particularly sensitive to changes in pH. Branching corals in particular have very fine structures that are weakened by high acidity levels, making them more easily breakable, more susceptible to storm damage and less able to repair and adapt to changing conditions.
Kit list and any templates:
- 10ml syringes: 10ml syringes on Ebay
- Universal indicator: You can use any indicator that will give a noticeable change in colour as acidity increases, but universal indicator gives the best effect
- 2.5L for 52.05 on Phillip Harris
- Bottle of sparkling water: Any supermarket
- Jug of tap water
- Cups/small beakers
- White A4 paper: Or if you have them, white spotting tiles
- Vinyl gloves: Ebay link
- Universal Indicator Scale Sheet – in resources
- Pipette or dropper
- Safety specs/goggles
Download full Activity pack: Ocean Acidification
This activity is part of the ASDC project Our World From Space. Our World From Space is a two-year national STEM programme exploring the relevance of UK space science for the future health and sustainability of our home planet, funded by UK Space Agency in partnership with Natural Environment Research Council (NERC), part of UK Research and Innovation.