Sea stars continue to waste and die along the US West Coast, and while researchers aren’t yet certain what’s causing the outbreak to spread, they’re beginning to suspect a combination of increased water temperatures that weaken the animals and leave them vulnerable to infection from opportunistic bacteria and parasites.
Dubbed Sea Star Wasting Syndrome (SSWS) the condition emerged in patches nearly a year ago, and by June had become serious enough that scientists convened in Newport to discuss what they were seeing, what was known and what remained to be learned. Since that meeting, the disease has spread both north into Alaska and south to Baja California.
“The expansion up into Alaska is really problematic because the California current comes across the northern part of Vancouver Island and then down, and this has jumped into a whole other current system,” explained Steve Rumrill, a biologist with the Oregon Department of Fish and Wildlife.
Rumrill and his colleague Dr. Tim Miller-Morgan, an aquatic veterinarian with Oregon Sea Grant, have been busy drafting documents that synthesize what is known about the outbreak. They summarized those documents at the recent State of the Coast conference in Florence. The papers underline key issues and research recommendations for continued monitoring, studies about pathology, investigation of ecological impacts, handling of captive animals and outreach programs. Recommendations include creating uniform signage and information displays for the public, and establishing a database for scientists to post observations about the disease in their areas.
The outbreak’s cause remains elusive. While some institutions are documenting what appears to be an infectious trend among stars, pathologists have been unable to find evidence of a specific infectious agent.
“Many of the pathologists are saying that there is no evidence of an infectious agent,” Miller-Morgan said. “That doesn’t mean there isn’t one. But when they are looking at slides, they aren’t seeing any evidence that would traditionally be associated with an infectious process.”
They have found a variety of bacteria and parasites associated with infected stars, however. This supports the leading theory that some initial cause—whether pathogenic or environmental—deteriorates the stars‘ outer layer, exposing them to secondary invaders. Increases in water temperature appear to be a significant factor in the syndrome, but the exact role that plays has yet to be determined.
“We have identified new areas and directions that need more research, and we have added more questions to the pile,” said Miller-Morgan. “The other thing is that there really is an impetus now to get together more regularly.”
On the bright side, field biologists have recently observed relatively large numbers of juvenile sea stars in a wide variety of tidal zones along the west coast.
“It is encouraging that the juvenile sea stars are beginning to emerge,” said Rumrill. “Juveniles have become a prominent component of the remaining populations at several sites, and the mixed groups of tiny and middle-sized stars may be an indicator of multiple recruitment events. However, it is not clear what role these new juveniles will pay in the overall recovery of sea star communities.”
The outbreak is gaining national attention since reports of a similar outbreak on the East Coast. Marine animal health experts from both coasts will meet at an upcoming Fish Health Conference in South Carolina to discuss parallels in the syndrome. Rumrill and Miller-Morgan also plan another West Coast symposium to share what researchers and aquarists are learning about the syndrome and what might be done in response.
For more information, or to assist with a citizen science project, visit the Pacific Rocky Intertidal Monitoring website.