Understanding Oceanic and Terrestrial Controls on Dissolved Oxygen Variability in the Coos Bay Estuary (2014-16)

David Sutherland
University of Oregon
Geological Sciences
1272 University of Oregon
Eugene, Oregon 97403
Phone: 541-346-8753

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Co-PIs: Josh Roering, UO; Daniel Gavin, UO

Dissolved oxygen (DO) concentration is a key water quality metric for assessing how well coastal ecosystems function. Sustained low DO levels can harm an ecosystem, resulting in the loss of beneficial ecosystem services, such as healthy habitat for shellfish. In Pacific Northwest estuaries, DO undergoes a large seasonal swing due to wind-driven, summertime upwelling. Upwelling is a naturally occurring cycle which brings nutrient-rich, but oxygen-poor waters from the continental slope to the ocean surface. This naturally occurring exchange stimulates growth of phytoplankton, for example. However, since the beginning of the 21st century, the intensity and occurrence of low DO water on Oregon’s inner shelf has increased. Too much oxygen-poor water, also known as “hypoxia,” can stop growth and production and cause massive die-offs of species.

This shift compels us to ask: what led to the sudden emergence of inner shelf hypoxia on the Oregon coast? How are lowered ocean and estuarine DO levels connected? Does DO in estuaries always reflect oceanic variability? These questions are difficult to answer at the present time. There are numerous other processes that can modulate DO levels in nearshore ecosystems on a wide range of time scales. These processes include the long-term variations induced by ocean-atmosphere circulation that might lead to changing trends in temperature and precipitation (and thus runoff) patterns. In addition, there are terrestrial controls that include the well-documented history of land use change in the watersheds bounding the estuary, such as industrial timber harvesting, splash dams, urbanization, and fire.

Dr. David Sutherland, a researcher from the University of Oregon, hopes to answer some of those questions. This project will elucidate the mechanisms involved in controlling DO in Oregon’s estuaries. The research team will work with local organizations, tribal nations, and state and federal entities to communicate results to the Coos Bay water quality community. And the US EPA will use the resulting data to inform new water quality standards presently under review. A major goal of this work is to raise the profile of water quality research in the local community and to educate the public on why healthy ecosystems are important.

Strategic Plan Focus Areas: Healthy Coastal Ecosystems and Habitats

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