PART A: SOLUBILITY

Activity Objective: Students will determine the effect of  temperature and salinity on dissolved oxygen and on sources of oxygen in the  water.

Estuary-Net Outcome Connection:

Students will understand water quality and the variables that contribute to water quality.

Students will be able to use the scientific process to test a  hypothesis and will understand how science and the process of science contributes to decision-making.

Students will understand how to use telecommunications and the benefit of telecommunications networking for collaborative  problem-solving.

Assessment: These outcomes can be assessed through observation during the inquires and closing discussions. Each inquiry is designed to test a hypothesis about the variable being studied. When students have completed their inquiries, teams of students prepare a presentation about their inquiry. The presentation includes a statement of their hypothesis, a  demonstration of the experiment (when possible), the results of their experiment, a conclusion (so the results support the hypothesis), and  implications that the results have on estuarine life.

Students should complete a self-assessment at the  conclusion of each inquiry. This assessment can be about how the team interacted, what the students learned about working with others, what the  students learned about water quality or estuarine life, or if the students are achieving the objectives. See below for possible forms. Questions at the end of the assessment should change to be consistent with the objective being studied.

Time Needed: 2-3 class periods.

Materials: See inquiries. Copies of inquiry  procedures.

Procedure:

1. Discuss concept of diffusion.
2. Divide students into investigative teams of at least 3 individuals.
3. Assign, or have students select one of the following questions to  investigate: (All students can work on one question or students can be grouped  to answer all questions.)
1. How is oxygen supplied to estuarine waters through abiotic process?
2. What are the biotic sources of oxygen to the estuary?
3. What is the influence of temperature and salinity on dissolved oxygen?  Identify whether there is a maximum or saturation level of dissolved oxygen.
4. Ask the teams of students to form a hypothesis and test it using the materials provided.
5. Ask the students to demonstrate the experiment they used to test their hypothesis, and present their findings.
6. Idenitfy the implications that these findings have on estuarine life.

The following are possible hypotheses and  experiments:
 

POSSIBLE INQUIRY A:
How is oxygen supplied to estuarine waters through abiotic processes?

Time Needed: One class period.

Materials: Three 10 gallon aquariums, thermometer, fan, hand  mixer.

Hypothesis: Dissolved oxygen in water can increase when water  mixes with the atmosphere.

Procedure:

1. Fill all aquariums with water of the same temperature.
2. Take a sample from each and titrate it for dissolved oxygen.
3. Aquarium #1 sample - leave alone.  Aquarium #2 sample - blow a fan on high at the surface.  Aquarium #3 sample - use hand mixer to stir.
4. Do each activity for five minutes.
5. Retest each for dissolved oxygen.

POSSIBLE INQUIRY B:
What are the biotic sources of oxygen to the estuary?

Time Needed: Two class periods over a 4-day period.

Materials: Diatoms, sun tea jars, thermometer, DO titration kit.

Hypothesis: Aquatic plants release oxygen through  photosynthesis and increase the level of dissolved oxygen in the water.

Procedure:

1. Fill two jars with temperate water - about 21° C.
2. Take a sample from each and titrate for DO. Record.
3. Add diatoms to one jar. Cover both jars. Leave both jars covered in the sun  for 48 hours.
4. Take samples from the tops and bottoms of each jar. Be careful not to  introduce oxygen by mixing while taking samples.
5. Titrate samples for DO. Record and compare.

POSSIBLE INQUIRY C:

What is the influence of temperature and salinity on dissolved oxygen? Identify whether there is a maximum or saturation level of dissolved  oxygen.

Time Needed 2 class periods.

Materials: Six jars with lids, two 1-gallon jugs, plate warmer (not a hot plate), salt, DO titration kit, ice, stirrers,  thermometers.

Hypothesis: Water of different temperatures and salinities absorb oxygen at different rates and contain different amounts of oxygen when 100% saturated.

Procedure:

1. Fill two, 1-gallon jugs with 21° C water.
2. Place enough salt in one to make a 35 ppt solution (add 33 grams of salt to  a one liter container, then add water to make one liter).
3. Place covers on both jugs and shake jugs until the salt solution is mixed. Be sure both are shaken equally hard and long.
4. Fill one jar with salt water and the other with fresh water. Mark them "cold salt" and "cold fresh". Let them sit ten minutes while you fix the other jars.
5. Fill two more jars with 21° C water, one with fresh and one with salt water. Mark them "warm salt" and "warm fresh", let them sit.
6. Fill the last two jars with 21° C water. Mark them "room fresh" and  "room salt".
7. After ten minutes, take a sample of the "cold" jars (the first two) and  titrate for dissolved oxygen. Mark the reading on the jar. Place them in the refrigerator.
8. Repeat the procedure with the "warm" jars. Mark them and place them on a plate warmer.
9. Repeat with the "room" jars, leave them out, but not in the sun.
10. Remove cover on all jars overnight. Repeat the titrations during the next  class period or class the next day.
11. Shake each jar for five minutes, re-sample, shake again, re-sample, keep shaking until the readings remain the same over three samplings. Be sure to  uncap and recap jars between each shaking. Note the varying readings for different temperatures and salinities.

PART B: RELATIONSHIPS

Activity Objective: Students will learn to analyze a dataset  to determine the relationship of DO, salinity, temperature, and depth over time  and space. They will learn to apply their understanding of this relationship to  an estuary and determine impacts these variables have on organisms  there.

Estuary-Net Outcome Connection:

Students will understand the importance of gathering long-term accurate data; will learn how to display the data; and will learn methods of analyzing the data to determine relationships.

Students will be able to use the scientific process to test a  hypothesis and will understand how science and the process of science contributes to decision-making.

Students will understand their connection to and the importance of estuaries, and the impact upland activities have on these systems.

Students will understand how to use telecommunications and the benefit of telecommunications networking for collaborative  problem-solving.

Assessment: Assessment can include the students' reports  which they send to the listserve. Their ability to submit and analyze data to justify their hypotheses about relationships between water quality variables  should demonstrate their further understanding of estuarine ecosystems. Reports sent to the network should be used as an additional assessment of student understanding of Activities A. Analysis of reports received from other sites can  be in written form or as a class activity. An emphasis is placed on making connections and comparisons with other schools. At this time, students are  refining their use of the data analysis software. Use a self-assessment to  determine how well students are achieving this.

Time Needed: 2 class periods (1 computer lab).

Materials: Computer, spreadsheet software or spreadsheets and  graph paper, copy of procedure, datasets.

1. In small teams, draft a prediction of the relationship between DO, temperature, salinity, and tide (depth).
2. Using the System-wide Monitoring data table of your choice, found at CDMO , download the dataset into your data analysis software. Graph the relationship  by month, week or day.
1. DO & temp. & salinity.
2. Depth & temp. & salinity.
3. Depth & DO.
3. In small groups discuss the relationship of tides, salinity, depth and temperature. Summarize the relationship in a hypothesis.
4. Using another System-wide Monitoring dataset from the same location, but at a different time, graph the same relationships as in #2.
5. Compare the results. Is the relationship supported by your hypothesis? If  not refine the results and suggest a rationale for the differences.
6. Open another System-wide Monitoring dataset from the same time but at a  different spot.
7. Graph same relationship as in #2 & #5.
8. Compare results and explain rationale for differences.
9. Compare results with remainder of class. Come to consensus with the class on the reasons for these differences.
10. FTP you ideas in the form of a report to your Watershed Coordinator for  review. The Watershed Coordinator will send reports to collaborating regional sites.
11. When reports are available, compare and discuss.
12. Discuss the implications of your findings on estuarine organisms.

Continue on to the sample of LEVEL I Activity 7 - Share the Data

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