2026 Puget Sound

University of Washington Tacoma

TGEOS 445 - Estuarine Field Studies

Spring 2026

View of Dalco Passage from East Passage aboard the R/V Welander

"Knowledge acquired and stored away in data banks or presented in scattered brochures is not really knowledge. Like the tree that falls in distant Siberia, it makes no sound when there is no one to hear it."

— Joel W. Hedgpeth, 1983

Introduction

Puget Sound is a fjord-type, partially-mixed estuary system located within the Salish Sea on the West Coast of North America. Carved by glaciers, Puget Sound’s intricate coastal morphology and complex bathymetry work together to support the region’s rich and beautiful biodiversity in a variety of habitats ranging from bull kelp forests to mud flats.

From the Pacific Ocean, water enters the Salish Sea through the Strait of Juan de Fuca. At the strait’s eastern reach, Puget Sound extends to the south through Admiralty Inlet and Deception Pass for nearly 100 miles, ending at Budd Inlet in Olympia, WA. To the north, water flows around the San Juan Islands through Haro Strait, the San Juan Channel, and Rosario Strait and into the Strait of Georgia.

The 2026 Estuarine Studies field team collected data in Commencement Bay, Quartermaster Harbor, the San Juan Islands, Colvos Passage, and East Passage in order to profile and analyze the parameters that characterize Puget Sound’s unique estuarine ecosystem.

At all stations, researchers collected discrete samples to assess dissolved oxygen, nutrients, chlorophyll concentration, and phytoplankton abundance and concentration, along with CTD profiles (including data on temperature, salinity, dissolved oxygen, fluorescence, density, and transmissivity). In the San Juans, sampling for pH, zooplankton abundance, and microplastics was also conducted. Sediment size and total organic content was assessed at select stations. Detailed sampling and analysis information can be found on the Methods page of this website.

Map: ESRI ArcGIS Pro - Kendall Burch

Images used with the permission of Northwest Indian Fisheries Commission

Coast Salish people have inhabited and stewarded the lands and waters of this region since time immemorial, including the Lummi, Muckleshoot, Nisqually, Puyallup, Samish, Sauk-Suiattle, Suquamish, Swinomish, Tulalip, and many others. In our learning and research, and in the interpretation and sharing of our observations with the public, we respectfully hope to contribute to the understanding and protection of this ecosystem for generations to come.

The information synthesized by our team will contribute to an ever-growing body of research on trends in the Puget Sound estuary, and may serve as a resource for future students, teachers, and estuary enthusiasts seeking a deeper understanding of what makes the Puget Sound so unique.

Learn more about tribal conservation work and treaty rights

The Puget Lobe of the Cordilleran ice sheet as it would have covered Western Washington 16,000 years ago. By 15,500 years ago, the ice sheet had retreated, carving out the Puget Sound basin as it exists today (Washington Geological Survey 2008).

About Puget Sound

Puget Sound as we know it today was formed over millions of years through a set of complex geological processes including plate tectonics, earthquakes, and volcanic activity. The Puget Sound region is extremely tectonically active, with the majority of activity concentrated beneath the Puget Sound between Olympia and the Southern Whidbey Island Fault (Stanley et al. 1999). This heightened level of activity makes the Puget Sound an area where earthquakes are extremely common.

Additional tectonic activity helped to create the Cascade Mountain Range. This range contains thousands of volcanoes, over 200 of which are considered active, having erupted within the last 10,000 years (O’Hara et al. 2020). Three of these volcanoes, Rainier, Baker, and Glacier Peak, are considered part of the Puget Sound Region. Over a span of millions of years, these volcanoes have erupted and helped to create the sediment deposits upon which the Puget Sound sits today. Glaciers from Mount Rainier also provide freshwater input to the Sound at several points including the Puyallup River in Tacoma. Additionally, glaciers formed during the most recent Ice Age carved out the basins of what would later become the Puget Sound. (Howard and Kaser 2021).

Puget Sound is the second largest estuary in the United States. It is relatively narrow, ranging from 1 to 5 miles in width. The average depth of Puget Sound is 140 m, and its deepest point is 280m deep.

It consists of four main basins: the South Basin, Main Basin, Hood Canal, and Whidbey Basin. Each basin within the sound is defined by the presence of underwater sills, which aid in mixing dense, salty water from the ocean with fresh water that flows down from the Olympic and Cascade Mountains.

Major rivers flowing into and influencing the circulation of Puget Sound include the Dungeness, Duwamish, Elwah, Nisqually, Nooksack, Puyallup, Skagit, Snohomish, and Stillaguamish (Encyclopedia of Puget Sound). North of the San Juan Islands, the Fraser River flows into the Salish Sea, contributing around 50% of the total freshwater present in the system (Canada Water Agency).

Map courtesy of Jennifer Burke/Puget Sound Partnership 2025. Source

Differences in mixing and stratification between partially-mixed and fjord-type estuaries. (Wollast and Duinker 1982)

Circulation and mixing patterns vary throughout the Sound. While it is classified as a fjord in terms of geological origin, the manner in which fresh and salt water circulate through most of Puget Sound is typical of a partially mixed estuary (NOAA 2024).

In this type, vertical stratification is present, meaning that there is a distinct difference in salinity between the upper and lower layers of the water column. However, some measure of mixing does occur at all depths. In a fjord (as classified based on circulation), such as Hood Canal, far less mixing occurs, resulting in more distinct layers within the water column (Strickland 1983).

Puget Sound experiences mixed semidiurnal tides, meaning that each day, there are two high tides and two low tides, each at different heights. The tidal range varies by location and is higher further inland. In Olympia, the range is highest at 14 feet, while the mean tidal range at Admiralty Inlet is no greater than 6 feet (Encyclopedia of Puget Sound).

The Research Team

Spring 2026 Estuaries field team

Top row, from left: Ronnie Sullivan, Audrey Lambert

Bottom row, from left: James Simpson, Kendall Burch, Andy Tarr, Miranda Chatwood, Emily Kreidler, Christiana Smith, Cheryl Greengrove, Hozoji Matheson-Margullis, Hannah Seerden, Cristian Carreno

Not pictured: Sonam Sherpa

The A Team

Hozoji Roseanne Matheson-Margullis, Andy Tarr, Kendall Burch, Miranda Chatwood, Hannah Seerden, Ronnie Sullivan

The B Team

James Simpson, Cristian Carreno, Christiana Smith, Emily Kreidler, Sonam Sherpa, Audrey Lambert

Pictured at Back: Captain Dave Thorseon of the R/V Welander

Acknowledgments

We thank the crew members of the research vessels used throughout the quarter, Captain Dave Thoreson (R/V Welander), Captain Eric Loss (R/V Kittiwake), and Kristy Kull (Marine Tech R/V Kittiwake).

We thank the supporting staff of Friday Harbor Labs.

Thank you to Julie Masura, Kat Barlow, Allison Aasen, Lydia Bader, Mikayla Mays, and Nghi Phan for their support throughout this quarter.