Sea star wasting disease broke out in 2013, causing large-scale population decline in several species of sea stars along the west coast of North America, from Mexico to Alaska. Previous research on the disease has mainly focused on intertidal populations, and little is known about how the disease impacts sea stars living below the low tide water line.
Joe Gaydos, wildlife veterinarian and chief scientist with the University of California, Davis, School of Veterinary Medicine’s SeaDoc Society, and colleagues investigated the impact of sea star wasting disease on species in the Salish Sea, which straddles the U.S.-Canada border and is home to a diverse number of sea star species. They found dramatic declines in the populations of sunflower sea stars, Pycnopodia helianthoides, along with several other sea star species. To learn more about the study and the significance of its results, I interviewed Gaydos via email.
What prompted you to study science as a career?
JG: I have always been interested in the natural world, wildlife in particular, and loved how much science could teach me about how wild animals live. Science was the perfect fit for me.
What drew you to studying sea stars?
JG: I love to scuba dive and always appreciated the diversity of sea stars we have here in the Salish Sea. I also study diseases of wildlife so when the sea star wasting disease hit, I just had to know which species were affected.
Why do you think more research has been conducted on predation rather than infectious diseases in marine ecosystems?
JG: For a long time, ecologists didn’t really think that wild animals got diseases, so people didn’t study them. Since people figured out that wild animals do get diseases, and that diseases shape ecosystems, scientists have learned loads. Because it is innately more difficult to study things in the ocean than on land, our understanding of marine diseases has lagged behind.
In your study you used long-term data from diver surveys as well as shorter-term sampling from strip-transect surveys. Why did you use both of these methods? What did each method reveal?
JG: We were stoked to be able to use 10 years of rigorously collected volunteer diver data. It allowed us to show that declines caused by the sea star wasting disease outbreak were not just some background population decline, but really connected to the outbreak. The strip transect surveys gave us data on disease prevalence that we couldn’t get from the volunteer dive surveys. It also allowed us to investigate disease impact on a larger number of sea star species.
You found that sunflower sea stars have effectively disappeared from the Salish Sea. Were you surprised by this finding? What effect does their decline have on the ecosystem?
JG: We suspected this based on our own experience. We used to see sunflower stars on 90 percent of dives and could see 10 to 30 per dive. Now seeing one is like seeing a giant pacific octopus. We photograph it, we video it, and then we talk about it when we get back on the boat. This study showed that was happening all over. Sunflower stars are major predators. Having them gone will allow their competitor predators to thrive. It also will allow their prey to increase. We showed increases in red and green urchins here, but I think other prey species will become more abundant too.
What are the next steps for your research, and what impact do you hope it will have?
JG: We and other researchers are already having conversations with National Marine Fisheries Service about sunflower sea star declines. We’re proposing they be listed as a Federal Species of Concern. This will help us keep a better eye on them so we know if we need to be actively working on their recovery or not.
Research Article: Montecino-Latorre D, Eisenlord ME, Turner M, Yoshioka R, Harvell CD, Pattengill-Semmens CV, et al. (2016) Devastating Transboundary Impacts of Sea Star Wasting Disease on Subtidal Asteroids. PLoS ONE 11(10): e0163190. doi:10.1371/journal.pone.0163190
Image Credit: Joseph Gaydos; Janna Nichols