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Aquatic Respiration
Chemistry of Oxygen Solubility
Data Interpretation
Diel Temperature Variation in Lakes
Effect of pH
Effect of Photosynthesis and Respiration on Aquatic Chemistry
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Increased Conductivity
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  Respiration in a Microcosm

Group Names: ____________________________________________________

Date: _______________________

Test kit instructions need to be followed precisely. (A practice test with water of known DO content and pH may be used before you begin the actual testing.)

You will create a microcosm by adding sediment or fish to water in a bottle. If your teacher has provided chemical reagent test kits you will test the DO and pH after 20 to 30 minutes. If you are using meters to measure DO and pH you will sample every five minutes.

Type of microcosm you are analyzing: ______________________________________

Experimental Design
Add 150 ml of water to your microcosm bottle. Enter your prediction for the initial DO and pH measurements into the table below. Reflect on what you know about DO, pH, and water before making your prediction. Test the DO and pH of your water sample before adding the sediments or fish. (If using test kits, slowly pour water from your microcosm into the test kit bottles, or take a sample with a pipette. Try not to splash the water as you are transferring it to the kit bottles.) Record your measurements in the table below. Then add your sediment or fish to the bottle.

Data Collection
Describe the contents of your microcosm

Sediment: describe


– Or –

Minnows: describe and indicate how many


Predict what will be observed in your next measurements.


*Note: A maximum of 30 minutes should be allowed for oxygen and pH changes to develop. This prevents unnecessary minnow mortality.

Test #


Predicted DO

Predicted pH

Measured DO

Measured pH









Data Management and Analysis

  1. How did your microcosms change?






Interpretation of Results

  1. Describe the change and provide a reason for its occurrence.






Reporting Results
Turn in your completed worksheet.

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date last updated: Saturday March 06 2004