Studying Swinomish Clam GArdens to better Understand Climate Change

Led by Dan Sulak, Swinomish Indian Tribal Community

For the Swinomish Tribe, adapting to climate change is essential for protecting the health and cultural well-being of its people. As with many Coast Salish tribes in the Pacific Northwest, clams are not only a traditional food source but also a cultural keystone species. However, environmental change is increasingly threatening these resources. In recent years, for example, extreme heatwaves have caused mass clam die-offs on culturally-important beaches, where clam populations were already in decline. In response, Swinomish has revived an ancient aquaculture technique known as clam gardening by building the first modern clam garden in the United States. Although ancient clam gardens likely provided temperature refugia, no research has yet examined how newly constructed gardens develop these conditions. This project addresses that gap. We will monitor temperature at the surface and within sediments at both the clam garden and a nearby control beach across all seasons. This study addresses four questions: (1) How do porewater and bottom water temperatures vary over time and space at both sites, and how are these patterns linked to broader water properties such as salinity, dissolved oxygen, or chlorophyll a? (2) At what tidal elevations are lethal or sublethal temperature thresholds for clams exceeded? (3) Does the sediment act as a heat source or sink, and how does this shift seasonally? (4) Are temperature patterns associated with clam abundance?

Full project name: Evaluating temperature refugia and sediment heat transfer at the Swinomish clam garden to address climate change concerns in native communities