Scientists are calling the decline of sea stars along the west coast the largest wildlife die-off ever recorded.
The conclusion came at a gathering of marine scientists in Seattle last week. Hosted by Seattle Aquarium veterinarian Dr. Lesanna Lahner, the sea star symposium brought together 40 scientists from across the U.S. and Canada to share their knowledge on the mysterious condition known as sea star wasting disease.
Since 2013, sea stars along the west coast have been dying off in huge numbers due to the disease, which causes lesions, breakdown of tissue and the appearance of “melting.”
The mass die-off poses a potentially devastating threat to ecosystems as species such as sea urchins — a common food source for sunflower sea stars — proliferate and consume kelp beds which provide vital habitat for all manner of marine species.
“The purpose of the meeting was to bring together as many folks as possible who have dealt with this problem to share what we know,” said Dr. Martin Haulena, head veterinarian at the Vancouver Aquarium Marine Science Centre.
Among the observations, scientists determined the disease appears to be linked to a virus commonly found among invertebrates as well as commonly found bacteria, but the missing link is whether an environmental trigger is exacerbating the problem.
“There are few times that a pathogen is solely responsible for such a wide-spread die-off,” Haulena said, adding there is likely an environmental factor involved. “We don’t have that smoking gun yet. We have this virus, we have sick sea stars; we don’t have the connection between them yet.”
Making matters more perplexing, not every species of sea star is affected in the same way, Haulena added. “There’s a lot going on here that we don’t understand.”
While some scientists at the symposium suggested the die-off is dire enough to have sea stars added to the endangered species list south of the border, Haulena cautions that approach may be premature.
Already, some sea stars in certain geographic areas are showing signs of recovery, but it’s too early to tell whether that will persist. Meanwhile, Haulena said the die-off may be part of a cyclical event common to sea stars that has previously gone unnoticed by the scientific community. “We have a very short memory in terms of how biological events go,” he said. “It’s only very recently that we started paying attention to sea stars in our own backyard.”
Moving forward, researchers present at the symposium will continue to build networks and share knowledge with the hopes of establishing a framework for collaborative research into the problem. And the Vancouver Aquarium is doing its part. In addition to research showing that densovirus, a virus commonly found in invertebrates, is associated with the condition, a forthcoming paper from Aquarium researchers will shed light on the potential use of antibiotic therapy for sea stars and sea urchins.