Putting It To Work: New Study Documents Transboundary Impacts of Sea Star Wasting Disease

A healthy Sunflower Sea Star (Pycnopodia helianthoides), an important predator in the kelp forests of the US and Canadian west coast. Photo by Janna Nichols.
A Sunflower Sea Star that has succumbed to wasting disease. Photo by Janna Nichols.
Green Sea Urchin populations have increased in areas where Sunflower Sea Stars have declined. Photo by Janna Nichols.

Sea star wasting disease has devastated sea star populations on the West coast from Mexico to Alaska. The disease broke out in 2013, causing massive death of several species of sea stars. Infected animals develop lesions that eat away tissue, with limbs dropping off as the animals die. The disease has been linked to a virus, although environmental factors may also be involved.

A new study, published last week in the scientific journal, PLoS ONE, presents an analysis of REEF survey data on several asteroid species collected by divers in the Salish Sea over the last 10 years. The Salish Sea is a Canadian / United States transboundary marine ecosystem, and world-wide hotspot for temperate asteroid species diversity with a high degree of endemism.

The results showed that some species were hit hard, while others increased in number. Populations of Sunflower Sea Star (Pycnopodia helianthoides), an important keystone predator in the region, dropped dramatically after the beginning of the epidemic. Several other sea star species, including the Spiny Pink Star (Pisaster brevispinus) also declined. Numbers of the less-common Leather Star (Dermasterias imbricata) and two species of sea urchin, which are prey for sea stars, increased after 2013.

The virus outbreak continues, and will have lasting effects on the ecosystem. Sunflower Sea Stars have effectively disappeared from the Salish Sea, the study concludes. Likely as a result, numbers of urchins have increased, which in turn will lead to more browsing on kelp. As a result, study co-author, Dr. Joe Gaydos, and his colleagues are currently in discussions with the National Marine Fisheries Service to get the Sunflower Sea Star listed as a “species of concern.”

The paper, titled "Devastating Transboundary Impacts of Sea Star Wasting Disease on Subtidal Asteroids", is available online here. Another study published earlier this year in the journal, PeerJ, used the REEF data to evaluate the potential trophic impacts of the seastar decline, as seen in the increase in sea urchins. That paper is availble here. View the entire list of all scientific publications that have included REEF data and projects at www.REEF.org/db/publications.

Design by Joanne Kidd, development by Ben Weintraub