Meeting Abstract
Over the next century, the global temperature could rise by 0.2 to 4.3 degrees C, warming oceans and putting many species at risk. Daphnia magna is a branchiopod crustacean in the order Cladocera and is commonly known as the water flea It lives in ponds and lakes over a wide range of temperatures (19-33 degrees C ). In this experiment, we are testing the upper lethal temperature tolerance of D. magna in cultures by subjecting them to near-lethal temperatures (32 degrees C) for a period of 12 hours using an incubator. This promotes sexual reproduction, then we allow the culture to return to 22 degrees C over a period of an hour and remain so for 34 hours. During this period, the fertilized eggs hatch. The eggs hatch much more slowly in near-lethal temperatures and are far more likely to die quickly after hatching, so a period of rest was necessary to promote growth. During the next cycle of near-lethal temperatures these juvenile D. magna will be exposed to the same near-lethal temperatures. We randomly selected five groups of five D. magna from the original culture and each group was subjected to the same experiment as above. We subjected separate groups of D. magna to varying lengths with one day, three days, five days, one week, and two weeks of this cycle between 32 degrees -22 degrees C. At the end of the experiment, D. magna was tested in water temperatures that had been lethal to the group with no acclimation. Once all D. magna were immotile the temperature was held steady. If all D. magna remained immotile for 30 minutes, the temperature was recorded as the lethal temperature. Over the course of the experiment, we found that the amount of time allowed for acclimation had no effect on the lethal temperature tolerance of the Daphnia magna In the future, we would like to test a much longer period of acclimation to produce a more realistic pressure on the water fleas.
