Aquatic respiration can have a profound effect on an ecosystem. In this lesson you explore how aquatic respiration affects water chemistry in a laboratory setting. You need to determine which water quality measures to use as indicators of the complex chemical interactions that occur. Then, in the second part of the lesson, you use WOW data to explore the changes in your selected water quality measures that occur in the hypolimnion of a lake during the summer.

Part I - Aquatic Respiration in a Microcosm

Knowledge Base
Participate in the class discussion of events such as aquaria that have been overfed or left untended for prolonged periods of time, or minnow buckets that have been left without fresh water for a prolonged period. Consider what happens. Why do the animals often die in these situations? What water quality measures might relate to the situation? Why might similar situations occur in lakes?

Experimental Design
A lake association curious about the effects of aquatic respiration on its lake has hired you as a consulting biologist. The lake association has asked you to answer the following questions:

• Can you demonstrate how respiration occurs in aquatic organisms?
• Can aquatic respiration be quantified?
• How does aquatic respiration affect water chemistry?

Research the effects that respiration can have on pH, DO, and conductivity (see the RUSS Unit section for more in-depth explanations). Use the WOW page and links. You need to determine which water quality measures to use as indicators of the chemical interactions that occur. The following equipment is available for your use:

1. Water quality testing kits or meters
2. 250 ml bottles with caps
   
   
   • 2-inch minnows
   • samples of sandy sediment
   • samples of organic/mucky sediment
3. Conductivity pens or CO2 testing kits
4. Thermometers

You need to plan and execute an experiment that can be completed in about one hour (one class period) in a laboratory setting to answer the lake association questions. Write out the procedures for your experiment before you begin. Your procedural plan should have enough detail so that someone else could complete the experiment without consulting with you.

Which water quality measures should be used as indicators? What are your predicted results from the experiment?

Data Collection

Describe how you will collect the data you need from your experiment. (Your data collection should include a table for recording data.) Write your description as a protocol (step-by-step directions) that others could follow. Create a table for recording the data from your experiment.

Data Management and Analysis
Summarize the results of your experiment. Include a graph to show your results.

Interpretation of Results
Consider possible explanations for your experimental results.

Reporting Results
You need to make a presentation to the lake association to provide your answers to their questions. Your teacher will specify the format: a written paper, an oral presentation, a poster, or multi-media presentation. Your presentation should include the information you considered during Part I of the lesson and the data collected and analyzed in Part II. Conclude your presentation with the next steps the lake association should take to more fully understand aquatic respiration.

Part II - Aquatic Respiration in a Lake

Water chemistry may change in response to biological activity. In this part of the lesson you investigate how water chemistry changes as a result of respiration.

Knowledge Base
Consider how what you have learned from working with microcosms might apply to a lake environment.

Experimental Design
The lake association is now concerned about water quality in the hypolimnion of its lake during the summer and has hired you again as a consulting biologist. It wants answers to the following questions:

• How does aquatic respiration affect water quality during the summer in the hypolimnion of the lake?
• What causes the changes in water quality measures?

Continue to research your selected water quality measure in the hyplimnion using RUSS data. Consider how respiration drives changes in your measure. What type of changes will reflect respiration? Will the changes show daily or seasonal variation? Why?

Identify the WOW lake you will investigate. Again, be sure to write out the procedures for your research before you begin.

Data Collection
Create a table to organize the data you collected from your lake. Download data for your selected parameter. Consider how to deal with data that you suspect is incorrect due to sampling or technological errors.

Data Management and Analysis
Create a graph that illustrates the changes in the water quality measure you identified.

Interpretation of Results
Based on your data, write a summary of the changes in your identified parameters in the lake's hypolimnion during the summer.

Reporting Results
Your teacher will specify a format for presenting your results to the lake association: a written paper, an oral presentation, a poster, or multi-media presentation. Your presentation should reflect data collected and analyzed in both parts of the lesson. Conclude your presentation with the next steps the lake association should take to more fully understand the dynamics of water quality in their lake.