Sea Star Wasting Syndrome and Kelp Forest Collapse in the Northeast Pacific

by David Greer

Sunflower sea star (Pycnopodia helianthoides). Ink and watercolor, by Susan Taylor. Courtesy of the artist.

During the past decade, an environmental calamity has been gradually unfolding along the shores of North America’s Pacific coast. In what has been described as one of the largest recorded die-offs in history of a marine animal, the giant sunflower sea star (Pycnopodia helianthoides) has almost entirely disappeared from its range extending from Alaska’s Aleutian Islands to Baja California, its population of several billion having largely succumbed to a disease of undetermined cause but heightened and accelerated by a persistent marine heatwave of unprecedented intensity.

Equally tragic has been the collapse of kelp forests overwhelmed by the twin impact of elevated ocean temperatures close to shore and of the explosion of sea urchin populations, unchecked in their voracious grazing of kelp following the virtual extinction of their own primary predator, the sunflower sea star. One of the most productive ecological communities in the world, kelp forests act as nurseries for juvenile fish and other marine life in addition to sequestering carbon absorbed by the ocean. It took only a handful of years for most of the kelp to disappear, replaced by barren stretches of seabed densely carpeted by spiny sea urchins, themselves starving after reducing their main food supply to virtually nothing. When a keystone species abruptly vanishes from an ecosystem, the ripple effects can be far-reaching and catastrophic. Read more »