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Ecosystem Measurement Tools
Once students have completed the introduction to the Hudson River and basic aquatic ecosystem science, we can move on to the exciting next step of using the tools that scientists use to understand aquatic ecosystems including the Hudson River. A key measurement tool for aquatic ecosystems is dissolved oxygen, abbreviated DO. By understanding the dynamics of DO, scientists can know how the aquatic animals and plants relate to each other and the chemistry and physical parameters of the water in which they're living. Plants produce oxygen in photosynthesis and both plants and animals use oxygen during respiration. Those plants and animals and the oxygen levels in the water respond to temperature in important ways. This section focuses largely on this very important measure of aquatic ecosystem health and balance: dissolved oxygen.
Lesson 1- Introduction to Dissolved Oxygen
This is a one or two-period lesson that helps students understand the basics of dissolved oxygen. Start with the reading on Dissolved Oxygen. Follow with the lab outlined in the lesson plan using the lab sheet to guide students through the lesson.
Lesson 2- Understanding and Creating Graphs in Excel
This lesson can be done in 1-2 days, or given as homework. It guides students through using Excel, and ends with using Hudson River data to create graphs.
Lesson 3- Inquiry Oxygen
For students who understand photosynthesis and respiration, this lab uses an inquiry approach to have students design an experiment that tests the effects of different variables on dissolved oxygen. If students are not comfortable with the material, you should follow lessons 4-7.
Lesson 4- Dissolved Oxygen and Temperature with Hudson Data
This lesson introduces is a one period lab activity that allows students to discover how temperature affects dissolved oxygen. For homework, students graph data on seasonal changes of dissolved oxygen and temperature in the Hudson River.
Lesson 5- Respiration with Hudson Data
This lesson is a two-period lab activity in which students discover that plants affect dissolved oxygen levels at night. This is followed by a graphing activity that examines dissolved oxygen levels in the Hudson over a 24-hour period.
Lesson 6- Photosynthesis
This lesson consists of 2 alternatives for using light to measure the oxygen levels that change as aquatic plants photosynthesize. The first lesson is a two-period lab activity that should follow the respiration lesson. Students test the increase in dissolved oxygen over a 24-hour period under different light types of light, or different light intensities. The second lesson is an easier alternative to the first lesson. It asks students to check for the presence or absence of oxygen, rather than measuring the actual amount of DO.
Lesson 7- Animals and Dissolved Oxygen
In this lesson, students will learn how animals are affected by decreasing dissolved oxygen levels. This is followed by a discussion of the effects of Indian Point Nuclear Power Plant, along with other sources of thermal pollution along the river. The lesson can be completed either as a teacher-led demonstration or in student groups.
Lesson 8- Photosynthesis and Respiration with Hudson Data
This lesson can be done as a wrap-up activity, or in place of lessons 4 and 5 which teach the concepts of photosynthesis and respiration separately and in more detail. In this lesson, students examine the ways in which plants and animals interact in aquatic environments by creating pond microcosms containing both plants and animals. Students will observe the changes that take place over several days as these plants and animals adjust to their new environment. For homework and to summarize their knowledge on this topic, students look at data from the Hudson River over a five-day period and answer questions about the changes taking place in the dissolved oxygen levels.
Lesson 8A- Aquatic Interactions (this can be used as an alternative for Lesson 7)
This lesson takes 2-3 periods and allows students to conduct a more in-depth investigation of the relationship between respiration and photosynthesis in aquatic environments.
Lesson 9- Dissolved Oxygen and Decomposition
Students set up an experiment to learn about the effects of decaying organic matter on dissolved oxygen. This can be linked to pollution and eutrophication.
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