Subject: Do different oxygen levels in water effect Daphnia and why?

I am currently doing a biolgy project studying the effects of different oxygen 
levels on Daphnia. To carry out my experiment, I will measure the heart rate of 
at leaset 5 daphnia at certain intervals, each 5 daphnia from one of  the six 
different Oxygen levels made up. I need information for my formal write up of 
the experiment and am finding it very difficult to find direct info on how 
oxygen levels effect Daphnia. My hypotheses is that lower levels of oxygen 
increase the heart rate of Daphnia. What happens if the heart rate is 
increased? How do Daphnia take oxygen in and use it? etc. It would also be of 
great help if you know of any similar experiments carried out. Thank you for 
your time. 

Re: Do different oxygen levels in water effect Daphnia and why?