Daphnia Dose/Response Bioassay
Data Form
Name __________________________
Date __________________________
Chemical tested ___________________________
100% concentration _____________________ mg/L
Length of experiment _____________________ days
Constants (such as temperature and light)
______________________________________
Table 4a. Daphnia
Bioassay Results
|
Concen- tration (%) |
Concen- tration (mg/L) |
# Dead after 1 hour |
# Dead after 24 hours |
# Dead after 48 hours |
Average # Dead after 48 hours |
||||||
|
Control |
|
|
|
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|
|
|
|
|
|
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|
0.001% |
|
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|
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|
|
|
|
|
|
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0.01% |
|
|
|
|
|
|
|
|
|
|
|
|
0.1% |
|
|
|
|
|
|
|
|
|
|
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1% |
|
|
|
|
|
|
|
|
|
|
|
|
10% |
|
|
|
|
|
|
|
|
|
|
|
|
100% |
|
|
|
|
|
|
|
|
|
|
|
Make a bar graph showing the average # dead Daphnia after 48 hours:
Some
questions to consider: (Please answer using full sentences.)
1. Did at least 80% of the Daphnia in the control beakers survive? If not, what would you recommend doing differently next time to
try to get a better survival rate?
2. Did the rate of Daphnia survival respond in a predictable way to
concentration? Describe any trends you
observed.
3. Do any of your data not fit the trends you observed? If so, can you think of any reasons why these data might lie outside the range you would expect?
4. What LC50 would
you estimate for your experiment with Daphnia? LC50 =
___
(If it is impossible to estimate the LC50 from your data, please explain why.)
5. What can you conclude about the toxicity of
the substance you tested? Is this what you expected? Was your hypothesis
supported by the data?
6. Think about whether any of the Daphnia might have died for reasons
other than poisoning by the chemical you tested. What other factors do you think might possibly have killed some
of them?
7. If other students carried out a
dose/response experiment using the same chemical, did their data follow the
same trends as yours?
8. Based on this experiment, would you say Daphnia would provide a useful bioassay
organism for water samples from the environment? Why or why not?
9. If you were going to repeat this experiment, what would you do
differently? How might you improve the experimental design to reduce the
variability of your data or lead to more reliable results?
© NSTA. Cornell Scientific Inquiry
Series. For use with Assessing Toxic Risk, Protocol 4.