Acidity, or a high concentration of Hydrogen ions (H+) can be detrimental to living things. Think about the acid in your stomach and what it does to food or battery acid and what it can do to your skin!
The acidity of any substance can be measured in a scale called pH, which goes from 1 to 14. A substance with a pH of 6 or less is considered acidic (has a lot of H+). A substance with a pH of 8 or more is considered basic (has less H+). A substance with a pH is 7 is considered neutral. Our ocean water is usually kept at a basic pH of around 8, our blood, at a more neutral pH of 7.4. A change in our blood pH from 7.4 to 6.8 can be very,very dangerous, and even cause death! The point I am trying to make, is that, generally speaking, any changes in pH may have some serious consequences in the living world.
It is important that you do not get fooled by apparent small size of the pH units (each pH unit increases by 1 from 0-14). Because pH is represented in a logarithmic scale, a change in pH value of one unit represents a change in concentration equivalent to 10X the amount of H+. For example if a substance undergoes a change in pH form 8 to 7 that means that the substance now has ten times more H+ than it used to have. A change from 7 to 6 shows another 10X increase in hydrogen ions. The more H+ a substance has, the more caustic and poisonous it is.
In this virtual lab, you will have the opportunity to learn about what is causing the water in our oceans to acidify (change to a more acidic pH) and the effects that this may potentially have on aquatic life and ocean based food webs.Go to the Virtual Urchin Lab Page on this link. https://depts.washington.edu/vurchin/index.php?view=acidocean
The first part of the tutorial consists of an interactive slide show about ocean acidification. Here, you will learn about the pH scale, ocean chemistry, and the oceanic food web that relies on Calcium. When you are done with the tutorial you should have the answers to the following questions.
- What was the concentration of CO2 in the atmosphere in 1985? What was it in 2005?
- What is the pH of drinking water? What is the pH of Ocean water?
- What is the projected level of CO2 in the ocean in 2050 (36 years from now) under the optimistic scenario? What is the corresponding pH level of the ocean?
- What is the projected level of CO2 in the ocean in 2050 (36 years from now) under the pessimistic scenario? What is the corresponding pH level of the ocean?
After looking at the interactive slide show, you will have a chance to do a virtual lab exercise where you will get to examine the effect of acidification on the development of Sea Urchin larvae. This virtual lab activity is intended to show you what acidity can do to a very important member of the food web in oceans in order to highlight the interconnectedness of all organisms to their environment and to each other.
Perform all the tasks in the virtual lab and answer the following questions: - What is the role of algae in this experiment?
- What does the sea water at pH= 7.7 represent?
- What is the average length of Sea Urchin larval arms at pH= 7.7? What is the average at pH=8.1?
- What is the conclusion of this experiment?