Measuring Toxicity in Aquatic Ecosystems

APESName

Date Period

Measuring Toxicity in Aquatic Ecosystems

Introduction

Environmental Scientists are concerned with the toxicity of commonly used substances. Toxicity refers to the ability of a chemical to cause injury or death, especially by chemical means. Aquatic ecosystems are particularly vulnerable to toxic chemicals. As economic consumers, we can have an impact in helping the environment by choosing products that are less toxic. In this lab we will measure the toxicity of four household cleaning substances: 409 All Purpose Cleaner, vinegar, bleach and Simple Green. Each group will test one cleaner at varying concentrations, and we will use class data for comparative purposes. We will be using a small aquatic organism, brine shrimp to test the toxicity of each of the various cleaning substances. You will design a controlled experiment to test one of the substances and then use class data for comparative purposes. The results of this experiment will be presented in a formal lab report.

Write an Introduction to this lab using the information above as well as your text (Chapter 14) and any necessary internet research. Include definitions and explanations of the following terms: bioassay, median lethal dose, poison, dose- response curve, and threshold. Your Introduction should be 2-3 paragraphs typed.

Complete the Experimental Design worksheet below.

Title/ Purpose: (What are you hoping to learn?)

Hypothesis: (What do you expect to happen?)

Independent Variable (what you will be testing):
Treatments of I.V. (indicate the control treatment):
Number of trials you will conduct for each treatment:
Dependent Variable (your method of measurement/ what you data will be):
Constants (or controls for all treatments):

Materials and Procedure List the materials you will use and write a step-by-step procedure of your experiment. Note: Measurements should be taken after 30 minutes and 24 hours. For the sake of consistency, all groups will use the same concentrations: 0%, 1%, 2%, 5% and 10%. Use additional paper and include in your lab report.

Data / Results

Create a graph to illustrate your data and the data collected by other groups. Use your graph to calculate the median lethal dose LD50 for each of the chemicals. (See page 357). Attach graphs to the Data section of your lab.

Discussion

This is a written summary and analysis of results that should be thorough and detailed. Usually two to four good paragraphs will be appropriate. Answer the questions:

• What does the data tell you? Interpret results by including comparisons (for example, to other scientific research) and speculations.

• Why do you think you obtained these results? Include explanation of possible error or deviation from expected results.
• Attach on a separate sheet of paper.

Conclusion

What is the principle finding or conclusion of the lab activity? This should be a clear evaluation of your hypothesis statement and a summary of your lab findings.

Attach on a separate sheet of paper.

Vocabulary Review

Be certain you know the definitions of the following terms.

Bioassay

median lethal dose (LD50)

poison

dose- response curve

threshold level

linear dose response

non-linear dose response

Data Table:% Mortality of Brine Shrimp in Various Cleaning Solutions- 1 hour Observations

Concentration/
Solution / 0ml Cleaner
50 ml Water
(Control)
[0% Cleaner] / 0.5 ml Cleaner
49.5 ml Water
[1% Cleaner] / 1 ml Cleaner
49 ml Water
[2% Cleaner] / 2.5 ml Cleaner
47.5 ml Water
[5% Cleaner] / 5 ml Cleaner
45 ml Water
[10% Cleaner] / Observations
Exp 1
% mortality