What is a Bioassay?

One way of testing water quality is to measure it chemically, using either simple field test kits or sophisticated laboratory equipment. Using chemical tests you can precisely measure the concentrations of selected compounds, but it is not feasible to test for every compound that might possibly be present. Bioassays, in which test organisms are grown in a sample of water or sediment, provide a means of measuring the combined toxicity of all contaminants present. What bioassays will not do, however, is identify the specific contaminants causing the measured toxicity. Bioassays are used by scientists to test the toxicity of newly developed chemicals such as pesticides or water treatment compounds. They also are used to rate the toxic potential of chemical waste sites and to determine the areas most needing clean-up operations.

To provide a useful measure of toxicity, a bioassay must respond predictably to a range of concentrations of a known compound as well as to complex mixtures of contaminants. It also should be sensitive, rapid, and cost-effective. Many different test organisms are used for aquatic bioassays, ranging from fathead minnows to single-celled algae. Duckweed, a floating aquatic plant, is commonly used. No one organism provides the perfect bioassay; each reacts in its own way, and the choice of which to use depends on what types of contaminants are of interest and for what purpose the bioassay is being conducted.

How are bioassays used in the real world?

Bioassay Techniques:
Lettuce Seed Bioassays
Daphnia Bioassays
Duckweed Bioassays