Sea Stars

sea stars
Healthy ochre sea stars (Pisaster ochraceus), California mussels (Mytilus californianus), and starburst anemone (Anthopleura sola) on rocks in a tidepool.

Photo: NPS

While towering redwood trees beckon your eyes upward at Redwood National and State Parks, there are also wonders at your feet. Along 37 miles of park shoreline, a colorful community of sea stars, mussels, crabs, surfgrass and other organisms thrive in the tumultuous rocky intertidal zone between land and sea. Some sea star species, like the ochre sea star (Pisaster ochraceus), play an especially important role in this ecosystem. They are a “keystone species,” a term derived from the importance of the wedge-shaped stone at the apex of a stone arch that prevents all the other stones from toppling. They maintain the diverse mix of species in an intertidal community by eating the California mussel (Mytilus californianus), which would otherwise rapidly coat the surface of the intertidal shoreline and crowd other species out.

An outbreak of Sea Star Wasting Syndrome, however, is devastating populations up and down the western coast of North America.

Sea Star Wasting Syndrome causes tissue decay in sea stars that first appears as white lesions and eventually progresses to body parts breaking off and often death. The cause is still not clearly understood, though evidence points to a bacterial or viral pathogen. This recent outbreak, the largest ever recorded on the West Coast, was detected in 2013 in Washington by researchers in the Multi-Agency Rocky Intertidal Network (MARINe).

More information as well as interactive data from MARINe sites can be found at

The disease has also been documented inside Redwood National and State Parks with the help of the science-based program Klamath-Network Inventory and Monitoring Program. This network was set up by the National Park Service to identify and monitor its vital resources over the long term. This long-term monitoring is tracking the progression of the disease in the park, including possible signs of recovery in the recent surge of juvenile sea stars at some sites.
two sea stars

Photo: David Lohse

Healthy ochre sea star (L) next to a diseased ochre sea star (Pisaster ochraceus) with white lesions (R) at a monitoring site at Redwood National and State Parks.
diseased sea star remains

Photo: NPS

An ochre sea star (Pisaster ochraceus) with lesions (bottom) and the remains of a decimated star after losing all but one arm (top) show different stages of Sea Star Wasting Syndrome.

Last updated: December 7, 2020

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