Ocean acidification represents a direct chemical change to global ocean chemistry in response to rising levels of atmospheric carbon dioxide (CO2).
Carbon dioxide is responsible for many of today's climate change-related issues. Because CO2 gets blamed for global warming and ocean acidification, this essential gas gets a bad reputation. Remember, plants need CO2 for photosynthesis, so it is a valuable component to our atmosphere. Historically, there has been a balance between CO2 being generated, and CO2 being taken in. The problem now is that CO2 is being created faster than it can be absorbed through natural processes. It is excess carbon dioxide that is the problem.
Ocean acidification occurs when CO2 is absorbed into the water at a high rate. It reacts with water molecules (H2O) to form carbonic acid (H2CO3). This compound then breaks down into a hydrogen ion (H+) and bicarbonate (HCO3-). The presence of all these hydrogen ions is what decreases the pH, or acidifies the ocean. This can be summed up with a nifty chemical equation:
CO2 + H2O -> (H+) + (HCO3-)
The saga does not end here, unfortunately. That carbonate molecule (HCO3-) is going to go on to cause trouble for marine organisms. This will be discussed in unit 2.
- Read pages 3-12 of the pdf Ocean Acidification: Coral Reefs In The Balance. It has good diagrams and graphs of the global carbon cycle.
- Also, check out Stanford University's virtual sea urchin lab for a fun and interactive lesson about atmospheric CO2 levels and also about how CO2 is absorbed by the ocean. http://virtualurchin.stanford.edu/AcidOcean/AcidOcean.htm
- The lab activities pdf has an experiment where you can cause ocean acidification on a small scale in an indivual cup of seawater. It is called "Student Activity 2: Ocean Acidification in a Cup".
Ocean acidification is occurring because excess carbon dioxide (CO2) in the atmosphere is being absorbed at the surface of the ocean at an increasing rate. This excess CO2 results in more hydrogen ions, which increases the acidity of the ocean.
This is a lengthy pdf document of a powerpoint presentation that accompanies a talk by Dr. Dwight Gledhill with the Cooperative Institute of Marine and Atmospheric Science. It is a good resource for background information about ocean acidification because it covers chemistry, carbon cycles, CO2 emmission, and focuses on the impacts of ocean acidification on coral reefs. If you are looking to fully understand these concepts, check this out.
Stanford University's virtual urchin website is a fun and engaging way to educate yourself about Ocean Acidification. The page titled Our Acidifying Ocean features interactive pages about different ocean acidification topics. Some of the pages are designed to help refresh your memory about what acids and bases even are! Other pages have you graph changes to ocean acidity by year or by CO2 emissions. Other topics are: pH, ocean chemistry, calcifying marine organisms, and urchin life cycles.
This pdf resource contains three fantastic classroom lab activities provided by the Ocean Acidification Subcommittee of the Ocean Carbon & Biogeochemistry Program. The first activity is about the pH scale, and how to test solutions to determine whether they are acids or bases. The second activity simulates the chemical process of ocean acidification in a cup using human-generated carbon dioxide! The third activity goes a step further and demonstrates the effects of ocean acidification on seashells using vinegar as the acid.