Science Buddies: "Ask an Expert"

Hi i'm doing a science fair project on the effect of oxygenated elements on the daphina magna's heartbeat.
What is the regular heartbeat of daphnia magna?
i did my experiment and i got around 35.
After i put in my oxygenated chemicals, nothing happened. Is that suppose to happen?
i saw no change in their heartbeat.
The elements i used were manganese dioxide,cupric oxide and potassium iodate
please help!

You have an interesting project but some questions must be answered before we can help you? -

What is the hypothesis you are testing
What are you using for oxygenating chemicals
How are you measuring the heart rate

Good luck,

Matthew W. mulanax

Try googling "daphnia oxygen heartbeat," I came up with a couple hits that might help you.

What is the hypothesis you are testing
What are you using for oxygenating chemicals
How are you measuring the heart rate

my hypothesis is that If I put in the element which has most oxygen, then it will increase the living term of the daphnia and increase the plant survival term, and the oxygen level will increase.
my oxygenating chemicals are manganese dioxide
potassium iodate and cupric oxide

i'm measuring the heart rate by looking through the microscope and i counted their heartbeat for 15 sec.

Hmm...are you thinking that in the water, the chemicals will break down and release oxygen into the water? Is this an experimental guide you are following, or something you came up with yourself? I'm no chemist, but I'm not sure it works that way...they may simply dissolve, but retain their molecular makeup. When I looked these compounds up on Wikipedia, I found no indication of breakdown in water:

http://en.wikipedia.org/wiki/Potassium_iodate
http://en.wikipedia.org/wiki/Manganese_dioxide
http://en.wikipedia.org/wiki/Copper(II)_oxide

I like the way you're thinking--it's a clever idea--but I'm just not certain the chemistry going to work quite like you want.

As an alternative, maybe you could bubble oxygen through the water at different rates? Or use different numbers of plants--they release oxygen when they perform photosynthesis.

Here's a site that describes oxygen levels in an aquarium tank, and a little bit about how to control them:
http://www.petplace.com/fish/too-little ... page1.aspx

Or check out this paper, which describes some chemicals that do affect Daphnia heart rate:
http://209.85.173.132/search?q=cache:s5 ... =firefox-a

Hope this helps!

Amber