# Bioassay

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Lead image: Sprouting lettuce seeds, Rasbak, CC BY SA

## What’s a bioassay and how does it work?

A bioassay is a method that uses plants, animals, or other living things to measure the harmful effects of environmental pollution.

This method works by exposing living things to different environmental samples, like soil or water, that vary in how polluted they are. Polluting chemicals in soil or water can affect how that living thing grows or functions. For example, contaminated soil can stunt a plant’s growth (see the image below) or prevent plant seeds from sprouting. So, measuring and comparing growth in living things exposed to different environmental samples can indicate the relative toxicity of the sample.

You can find a good introduction to bioassays with a short list of environmental monitoring studies that have used bioassays at the Environmental Inquiry page from Cornell University.

## DIY bioassay methods

### Lettuce seed bioassay for soil or water

This method uses common lettuce seeds to test for toxicity in soil or water samples. Contaminants in the soil or water can prevent seeds from germinating (sprouting) or slow down root growth.

Image: A lettuce seed bioassay showing longer roots in seeds that sprouted in distilled water (DW) compared to shorter roots in seeds exposed to different concentrations of ethyl acetate, a chemical that negatively affects growth. From Waqas et al. 2013, CC BY

How to use this method:

1. On the Environmental Inquiry page, you’ll find bioassay procedures and worksheets originally developed for high school classrooms.

1. The US EPA Protocols For Short Term Toxicity Screening Of Hazardous Waste Sites document is a more detailed guide providing background information, guidance on sampling and data analysis, and hypothetical case studies, plus procedures.
• Recommended step-by-step protocols for lettuce seed germination (section A.8.6, pg. 84) and lettuce root elongation (section A.8.7, pg. 90). These protocols are more involved and require more equipment than the “Environmental Inquiry” procedure linked above, so maybe less DIY.

• How easy is it to use? Beginner
• How easy is it to make? Beginner
• Cost upfront?
• ~$6 USD for a pack of 1000 seeds (make sure the seeds aren’t advertised as “treated”) • ~$1 USD for a gallon (3.8 L) of distilled water

## Uses for bioassays

• Determining the immediate toxicity of a potentially polluted soil or water sample.
• Evaluating whether remediation of a contaminated site is working (comparing bioassay results before, during, and after remediation).

## Limitations

• Bioassays won’t tell you what specific pollutants are present in an environmental sample.
• A single test organism / bioassay may not respond to all of the polluting chemicals you might be concerned about (Bitton and Koopman 1992, link to book chapter).
• The specific organism responses measured in the bioassay might not always be sensitive enough to indicate contamination. In the lettuce seed bioassay, for example, seed germination after 5 days is a common “endpoint” measurement that’s used to compare different samples. But some researchers have found that this measurement alone doesn’t always indicate toxic effects, and that comparing germination rates daily might be a more sensitive test (Da Silva Júnior et al. 2013, link to paper).

## Wikis

Title Updated Version Views Likes
Soil remediation 2 months ago by laurel_mire 10 179 1
Bioassay 3 months ago by alejobonifacio 7 217 2
Bioindicators 5 months ago by alejobonifacio 5 94 0
Biohacking / DIY Bio over 8 years ago by TedF 2 604 1

## Activities

Activities should include a materials list, costs and a step-by-step guide to construction with photos. Learn what makes a good activity here.