Testing Environmental Samples
Bioassays are used for various types of environmental testing, such as mapping contaminated areas at a hazardous waste site or determining the toxicity of wastewater being discharged into a lake or stream.

Using Daphnia bioassays, you can evaluate the toxicity of environmental samples. You might choose to test water from a local pond or stream, or runoff from your school parking lot after a storm. Another possibility is to test sediment from the stream bottom, dust and dirt from the parking lot, or soil from your school yard. Think about places where you would expect to find pollution, and try to come up with a question you could answer using bioassays.

Within any one species, individuals respond differently when exposed to any particular chemical. You can observe this in Daphnia bioassays, when some individuals die at low concentrations while others survive exposure to much stronger doses.

Between species, there are even greater differences in chemical sensitivities. You can test this idea by carrying out bioassays using both Daphnia and lettuce seeds, then comparing the results.