Blog Assignment #5 | Research Project Update

Authors: Azeem Jimoh, Joseph Yau and Jason Hall

In our original Hypothesis,depending on the amount and type of substance put in the biospheres, the daphnia's’ heart rate and survival will change. This had to be changed because as our experiment went on, we experienced mass death, (we didn't,the daphnia did =]). So every day when we went to check on them, no living data points besides our controls could be entered. Eventually because of this our hypothesis changed to “depending on the amount and type of substance the daphnia is exposed to, the heart rate will change.”

When doing our experiment, the substances we had were Ammonium Sulfate (a common chemical in fertilizer) which was substance X, Caffeine which was substance Y and Dawn liquid detergent which was substance Z. Knowing these three items could be harmful to anyone in a high enough dosage, our original plan was to have the biospheres have 1%,2%, and 3% of the water in the jars be the substances tested.

Figure 1: Photo shows The 12 jars and from top to bottom was the control jar, Substance X, Y, and Z. Then from left to right 1% concentration, 2%, and 3% concentration.

What surprised us was when we came back to our daphnia a week later, they were all dead except in our control jars. Although we had a low Percentage we  in each jar relative to the amount of water, that might of been too much for the daphnia, so we decided to lower our usage. In our percentages 1% was 4.5 grams of substance, 2% was 9 grams and 3% was 13.5 grams. We decided to lower this number the number to  1 gram, .5 grams, and .1 gram. When we came back just two days later, we were shocked again to see that most variable jars except the 0.1 gram of Ammonium Sulfate were dead, which contained one lone survivor. It was a larger sized daphnia so that may have been a reason for its survival. From this, we learned that Daphnia are extremely sensitive to their environment and even a slight change from the normal conditions they are used to living in could lead to their unfortunate demise.

After the third day of trials, a trend that was noticed among our group was how much even the slightest amount of change had on the daphnia. As seen from our first two days, when we changed the daphnia’s environment from no external substances in the biosphere to just 0.1 gram of a substance in its biosphere, the results can lead to massive amount of death. This high reactivity to change is proven even more by when we did short-term exposure and monitored the heartbeats, there was a large spike between the resting before heart rates and the after heart rates. For example for 0.1 gram of soap given to the daphnia the average heart rate change(in beats per minute) was a 66 decrease. Although this trend was shown through out our trials, perhaps the way we added the substances could have had an effect which would add for error if that were the case.

In our error analysis, We will most likely discuss the way our biospheres were created as that could have the biggest effect on the Daphnia’s well being. When we were creating our biospheres we had two plants (to start with, we had to use one for our second round of biospheres) and we filled the jar with approximately 450 mL of water. We also added dirt, sand, and soil.

Figure 2: Photo of the average set up of the jars. Picture taken before any extra substances were added

The reason why we review the way we set up the biosphere is that in the last lab period, there is a massive death of the daphnia in one of the control. This actually surprises us a lot since if there is death in our control environment that we did not add any substances we test in, this shows us there is a possibility that there might be other variables that affect the daphnia. Not knowing that, there might be variables that we did not control well in the actual testing biosphere. The following points are some possible errors.

Perhaps this plant could not provide enough oxygen for the daphnia in the jar and in addition to that, the stress from the biosphere’s smaller s use could have played a role in the death that was not entirely from the substance. Another factor we could talk about was our light cycle. We had an 8 hour in direct light and 12 hours in darkness with the remaining 4 hours in lab light. Perhaps this cycle of light and dark was too far off from their natural light exposure which could have cause premature death due to stress from environmental changes.

Moreover, when we did the test in the last lab period, we found out that there is a bit more daphnia in one of our control. After some further research, daphnia will reach the age where they are able to reproduce in 4-10 days depending on the environment they stay. Therefore, there might be a chance that the supply of nutrient from the water and the oxygen from plants becomes a limiting factor when the experiment proceeds.

A question we have for other groups is how well did you project go? For our project, we had to restart three times and even had to switch projects completely. Was it easy? Also if you had a project that involved Daphnia did you notice any severe sensitivity? Let us know!