Hi Flyleaf,
I think I’m missing something in your project. What exactly is your hypothesis—that increasing iron concentration in the ocean will stimulate algae growth and photosynthetic activity and therefore increase the amount of carbon dioxide that can be removed from the air? This was the idea of John Martin that he tested in 1989, I think:
http://www.palomar.edu/oceanography/iron.htm
http://en.wikipedia.org/wiki/Iron_fertilization
"Perhaps the most dramatic support for Martin's hypothesis was seen in the aftermath of the 1991 eruption of Mount Pinatubo in the Philippines.[citation needed] Environmental scientist Andrew Watson analyzed global data from that eruption and calculated that it deposited approximately 40,000 tons of iron dust into the oceans worldwide. This single fertilization event generated an easily observed global decline in atmospheric CO
2 and a parallel pulsed increase in oxygen levels."[8]
I read the wiki entry on Iron Fertilization [
http://en.wikipedia.org/wiki/Iron_fertilization]
and it seems to me that there are at least two effects of ocean iron supplementation on marine phytoplankton—increased photosynthesis and increased growth rate. Were you planning to measure both of these processes?
The question, as I see it is how much iron and what form do you need to add to achieve a certain level of carbon sequestration without creating harm from an algal bloom. So, I think you really need to look at the rate of oxygen production as a stand-in for CO2 absorption. You can measure rate of algal growth with the colorimeter.
If you buy the marine algae and growth medium salts from Carolina Biological, you need to find out from them what the concentration and form of iron is.
To make your project more interesting and personal, why don’t you try a variety of forms of iron with different degrees of bioavailability and measure their effects on O2 production and algae growth. In looking up all the different forms of iron you could try, I made a list:
• Fine iron particles
• Ferric sulfate
• Ferrous sulfate
• Nualgi algae supplement*
• Chelated iron [food supplement]
*
http://nualgi.blogspot.com/2009/03/iron ... on-to.html
Maybe you can come up with more ideas for iron sources to test, but try to limit the amounts of non-iron substances that may be included in an iron product, for example an iron-containing food supplement.
The problem with iron compounds is their relative insolubility. Even ferrous, Fe[2+], which is relatively soluble can be oxidized to the less soluble ferric Fe[3+] form. The pH of the water has a large effect on iron solubility, but to make your results relevant to ocean water you should keep the pH around 7.
Here’s some information on the amount of iron normally in sea water and the solubility of various iron compounds in water:
http://www.lenntech.com/periodic/water/ ... -water.htm
I hope this has given you some ideas about choosing the dependent and independent variables to use and designing your experiments. I don’t know what you mean by ‘jelly-balls’ in your second question. Can you explain?
Best wishes,
Sybee