The Cobble Beach at Snug Harbor

Aerial photo of Cobble Beach Washington Dept. of Ecology)
Left arrow: sheltered beach.   Right arrow: exposed beach .

Cobble Beach is located just outside Snug Harbor on San Juan Island, Washington. The beach can be accessed by walking around the point from Snug Harbor at low tide. Cobble Beach represents an unusual piece of shoreline for the region, consisting of long stretches of various sized cobble and boulders from the high to the low intertidal.  The beach area can be divided into two distinct regions.  The beach farthest around the corner from the Snug Harbor Marina is exposed to Haro Strait, while the beach closer to the marina is somewhat more sheltered within Mitchell Bay (see aerial photo).

The cobble sizes on the exposed beach range from large rocks greater than 1 m diameter to small pebbles. At the sheltered beach the variation is lower; typical cobble size is about 20 cm. The exposed beach is longer, with a gentler slope. Rocks and red and brown algae characterize the low intertidal region. In contrast, the sheltered beach is shorter, steeper, and muddy in the low intertidal region.  Both beaches are characterized by a barnacle zone higher in the intertidal, which eventually gives way to bare rock with fewer species dwelling underneath.

Drawing of exposed region of Cobble Beach

The distribution of animals along the tidal gradient at these two different areas is the most striking feature of Cobble Beach. Species with a higher thermal and desiccation tolerance are found higher up on the beach, while the animals that require cooler temperatures and increased moisture are found closer to the water line, enabling them to spend more time submerged.  In the following pages, we summarize our findings about the distributions and natural history of invertebrates at the Cobble Beach site.

Data Collection and Summaries
Survey methods

The Common and The Rare: Species of Cobble Beach
Species list

Functional Biology of Cobble Beach Organisms



Team Cobble

Amanda Winans, Laura Windecker, Alyssa Gehman, Heidi W. Weiskel
team cobble