Gasping for Breath in Hood Canal: Exploring the Dissolved Oxygen Crisis

Ann J. Murkowski, North Seattle Community College


In this collaborative exercise, students watch a short, online video of Washington State Department of Fish and Wildlife (WSDFW) divers documenting an acute low oxygen event that occurred in Hood Canal during the summer of 2006. They then work in groups to apply their understanding of photosynthesis, respiration, and nutrient cycling to develop hypotheses to explain the event. The instructor then provides additional data and allows the group to revisit their model. In an optional follow-up activity, students generate hypotheses about a water source in their immediate environment and use dissolved oxygen probes and water chemistry kits to test their hypotheses.

Learning Goals

Student Learning Outcomes for this Exercise Include:

  • Demonstrate an understanding of photosynthesis and respiration by modeling the effects of eutrophication in Hood Canal.
  • Interpret primary data to draw conclusions about possible causes of chronic and episodic low oxygen events.
  • Apply basic principles of chemistry and physics to model how and why stratification occurs in Hood Canal, and find out what are the biological consequences of this stratification.

Context for Use

This activity is intended to help students in either a major's or non-majors level biology course apply their understanding of photosynthesis and respiration to an interesting, local phenomenon, the anoxic events in Hood Canal. Through the use of an online video, students get to experience the significance of these events and then apply their classroom learning to develop hypotheses to explain the events. The students' inquiry can be guided around just the principles of photosynthesis and respiration, or expanded to include basic chemical principles of solubility and/or large-scale ecological processes such at nitrogen cycling. As described here, this exercise can be used early in an introductory cellular biology course to reinforce photosynthesis and respiration, or later on in either the biology major's series or an introductory course to introduce ecological principles. Students can typically view the video, and complete the group assignment in a single 50 minute period. If more class time is available, the activity can be expanded to include having students read and discuss the analysis of primary data generated by the Hood Canal Dissolved Oxygen Program (HCDOP). Additionally, an instructor could choose to include a field-based laboratory activity in which students use dissolved oxygen meters to test their hypotheses about dissolved oxygen levels in their own environment.

Description and Teaching Materials

The Learning Activities

Part 1: An Introduction to the Dissolved Oxygen Crisis in Hood Canal.
Students watch a short, five minute video, produced by the WSDFW. The narrated video takes the audience below the surface of the water to witness the unusual behaviors and dying animals associated with acute low oxygen events. This video can be found at:

Students then form groups to collaboratively work towards an understanding of these events using a structured worksheet. ("Student Handout 1").

Part 2: Exploring Recent Data Around Dissolved Oxygen in Hood Canal
As written, "Student Handout 1" directs the students to read the recent report " Two mechanisms of low oxygen stress to Hood Canal biota and their associated areas of risk" ("Student Handout 2A"). In this work, Jan Newton provides data on both surface salinity and oxygen levels and clarifies the role that stratification plays in the episodic events in Hood Canal. A list of questions for the students to answer about this work is provided. ("Student Handout 2B").

Part 3: Optional Field Extension 1: Measuring Dissolved Oxygen in Your Watershed
If equipment is available, students may continue their investigation by generating hypotheses to explain how and why dissolved oxygen levels might vary in their own watershed. At North Seattle Community College, Students use Hach dissolved oxygen probes (see coupled with their portable spectrophotometers to measure both dissolved oxygen and a variety of other water quality indicators including phosphate and nitrate. Students then graph the data to look for correlations.

Student Handout 1: Gasping for Breath in Hood Canal- Exploring the Dissolved Oxygen Crisis (Microsoft Word 2007 (.docx) 173kB Oct27 11)
Studnet Handout 2A: Two Mechanisms of Low Oxygen Stress to Hood Canal Biota and Their Associated Areas of Risk (Microsoft Word 2007 (.docx) 214kB Oct27 11)
Student Handout 2B: Gasping for Breath in Hood Canal- Exploring the Dissolved Oxygen Crisis, Part 2 (Microsoft Word 49kB Oct27 11)

Teaching Notes and Tips

In my experience, students have been eager to connect their learning to their immediate environment. They also seem to engage much more quickly with the content because of the dramatic nature of the WSDFW video footage. Combining these two "hooks" has provided me with a powerful mechanism to get my students to really apply their understanding of photosynthesis and respiration to a problem that is suddenly very real to them. As a result, these students demonstrate a much deeper understanding of both processes when I assess their learning in both this activity and on more traditional exams.


Students work collaboratively in groups to capture their learning on a series of worksheets. Their initial brainstorming activities can be used to capture students existing knowledge. These initial ideas can then be compared to the final hypotheses the students generate to assess their understanding of respiration, photosynthesis, and nutrient enrichment. In addition, the hypotheses they generate when asked to examine dissolved oxygen levels can be used to assess their understanding of the key biological processes identified earlier.

References and Resources

A plethora of data on the health of Hood Canal is available through the Hood Canal Dissolved Oxygen Program (HCDOP) at the University of Washington. Much of their data is freely available online ( and provides an excellent resource for both students and faculty. The University of Washington has an excellent scale model of Puget Sound that is available for use (as does the Pacific Science Center). This model allows students to use colored dyes of different densities to better understand how and why water moves in and out of Hood Canal. A variety of local groups, like the Homewaters Project at NSCC, maintain stream maps and water quality data. Students can collaborate with these groups to generate more sophisticated models or hypotheses about dissolved oxygen levels in aquatic systems in their immediate environment.