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Hypoxia

Impacts—Hypoxia

Summary: How are oxygen levels in the ocean changing as a result of climate change? In the waters off the Pacific Northwest of the U.S., seasonal upwelling brings nutrient-dense, oxygen-poor water to the surface, and the strength and duration of upwelling occasionally forms hypoxic (low oxygen) zones in on the sea floor along the outer and middle portions of the continental shelf. Recently, scientists have observed hypoxia (dissolved oxygen concentrations less then 1.4 ml/L) in shallow waters of the inner continental shelf, where low oxygen conditions have not historically occurred. This hypoxia led to the death of many coastal organisms. In this topic guide, students will read about the conditions that lead to coastal hypoxia in the Pacific Northwest, and use online data to determine current dissolved oxygen levels in coastal areas.

Concepts to teach:

Goals:

  1. Oxygen levels in the ocean are changing due to the effects of global climate change
  2. Because of climate change, upwelled waters in the Pacific Northwest have lower pH levels and lower oxygen levels than waters that have upwelled in previous years
  3. Coastal marine organisms are negatively affected by hypoxia
  4. Scientists use a variety of indicators to describe phenomena, identify patterns and make predictions

Standards: NGSS Performance Expectations

  • HS-ESS2-2. Analyze geoscience data to make the claim that one change to Earth’s surface can create feedbacks that cause changes to other Earth systems.

Specific Objectives:
Students will be able to:

  1. Define coastal hypoxia and the conditions that lead to its occurrence
  2. Describe relationships between global climate change, upwelling and hypoxia events off the Pacific Northwest coast
  3. Describe the effects of hypoxia on marine organisms
  4. Use online data to explore near-time or real-time dissolved oxygen levels off the coast

Activity Links and Resources:

  • Review the Upwelling and Ocean Acidification topic guides
  • Readings:
    • Article: C. Welch, 2015 National Geographic article Oceans are losing oxygen
      • Note the distinction between deep-water “oxygen-minimum zones” driven by temperature, and “hypoxic coastal dead zones” like that which occurs in the Gulf of Mexico and is driven by an influx of nitrogen and other nutrients from land. Which process underlies the low-oxygen events in coastal waters off the Pacific Northwest coast?
    • Article: F. Schubert, 2013 article from The Dalles ChronicleOcean dead zones in Oregon
    • PISCO Hypoxia pages—These pages from the Partnership for Interdisciplinary Studies of Coastal Oceans (PISCO) include definitions about hypoxia in the Pacific Northwest, including handouts, videos, research and FAQ
    • NOAA-Northwest Fisheries Science Center pages—See data images that show when and where hypoxic conditions occur in the Pacific Northwest
  • Activity: Use the NANOOS NVS Data Explorer to explore oxygen conditions off the Pacific NW coast right now. Filter for observing stations that measure Dissolved Oxygen (DO).
    • A detailed description of how to use the NVS Data Explorer is included in the Well, Well, Well lesson plan from NANOOS (Gr. 6-12)

Assessment:

  • How does climate change affect oxygen levels in the ocean?
  • What role does upwelling play in coastal hypoxia in the Pacific Northwest?
  • Students compare and contrast the causes of “dead zones” in the Pacific NW to those found in the Gulf of Mexico.
  • Using NVS Data Explorer or other products from NANOOS, what can be said about oxygen conditions in the ocean right now?