Before we started our experiment, we knew that there would be a significant amount of error because of human imperfection.  One error that we encountered was the fact that we were counting an actual heart beat, and it is highly likely that we either missed a heart beat or counted too many.  This makes our results not 100% correct. Another error that we ran into was the water.  The room temperature water stayed at room temperature, but the 15º C and 6º C water warmed up due to the fact that the temperature of the room was warmer than the water.  An additional error that we encountered was the daphnia.  The daphnia could not survive in the extremely cold water, and the cold water with alcohol, so we did the tests again with a different daphnia.  This effected our results because when daphnia get close to dying, their heart rates slow down, so if we tested the heart rate of a daphnia that was about to die, then the results would be different than one that had a daphnia that was healthier.


How Hypothermia Relates to Scuba Diving

    Our experiment relates to scuba diving because when one goes scuba diving in any water, there is a risk of becoming hypothermic.  If someone becomes hypothermic and is not treated it immediately, it could kill the hypothermic person.  If one is submerged in extremely cold water, like we did to our daphnia, it will cause the core body temperature and heart rate to drop, and this can lead to death.

When one is using people to count quick-movements with no technology other than a microscope, it is bound not to be 100% accurate. If we had the technology available, a great tool to have would have been some kind of daphnia-heart monitor similar to the kind used on humans, but specified to the small body of a daphnia. We also should have monitored the temperature of the water more closely to make sure the temperature remained the same. This would have helped us end up with more consistent results. Another thing we could have done was changing the temperature of the freezing water from 6º C to a little warmer temperature, such as 10º C. We would have done that because in the extended submersion the low temperature killed the daphnia. One more change that would have helped our experiment would have been using the same daphnia throughout the whole experiment, which would result in a consistent heart beat.

If we Could Re-design our Experiment...

Click on the symbol above to see how we found the percent error

    Originally, we were only going to test the immediate submersion where we put the daphnia into the water and immediately take the daphnia’s heart beat, but as we went on with the experiment, we made some observations from trial to trial. We noticed that that between each trial, the heart rate would go down several beats. We then came up with the “Extended Submersion,” (a modification to the original immediate submersion) in which the daphnia would remain in the beaker of room temperature (20º Cº), cold (15º C) or extremely cold water (6º C) for one minute prior to testing. We hoped this test would show the effects of remaining in cold water for an extensive amount of time rather than just a quick dive. We also tested the daphnia in the different water temperatures with alcohol using the immediate submersion. We did this experiment to test the fact that a person who is wet and intoxicated with alcohol and not properly dressed can become hypothermic in 70º weather.

    With the immediate submersion, we found that the control (room temperature) condition had the highest heart rate. The cold condition gave the daphnia a higher heart rate than the control, and the extremely cold water gave the daphnia the highest heart rate of all the conditions. We made the observation that in the room and extremely cold water temperatures the heart rate decreased throughout the trials. On the other hand, the cold water made the heart rate increase then decrease if you just look at the trials. Because the separate trials of the cold water test gave us intriguing results and due to inconclusive evidence, we decided to test our observation further with the “extended submersion.” Although the separate trials interested us, the averages followed our hypothesis correctly, with an increasing heart beat as the water got colder.

    In the extended submersion condition, we wanted to test our observation further from the immediate heart rate test that there is a difference between being submersed in the water for a short or extended amount of time. Our results proved our observation as an important one, because we found opposite results from the immediate submersion in the extended condition. In the immediate submersion, the colder the water got, the faster the daphnia’s heart beat. However, in the extended submersion, we found that the longer the daphnia was in the colder water, the more the heart beat decreased. Eventually, the daphnia could not stand the cold any longer, and the stage of hypothermia was so extreme that the daphnia died.

    Our final experiment was the alcohol condition, where we followed all the steps of the immediate submersion, but added ethanol alcohol. In this test, we added alcohol, and the colder the water got, the slower the daphnia’s heart rate. These results occurred because alcohol is a depressant, thus lowering the heart rate. Therefore, the statement that a wet, intoxicated person can become hypothermic in much warmer weather is true. As the data shows, the heart rate dropped 42 beats per minute by just adding alcohol to the room temperature water. The cold water with alcohol test dropped the heart rate by 49 beats per minute to the point of death.  The daphnia could not even take the severity of hypothermia at 15º C, where it usually could survive in the 6º C for a short amount of time. To make sure it was the temperature and not the daphnia, we tested the cold water with alcohol on two more daphnia. The first survived one trial, and the other survived two trials, but on the next the water killed it. From this we can conclude that being intoxicated and wet in the cold is the quickest way to get hypothermia.

Results Analysis: