For over a decade, sea stars along the coast of the Pacific Northwest have been hit by a mysterious wasting disease that causes their limbs to fall apart and adopt a decaying appearance. Researchers and conservationists have come together to bring back populations and solve the mystery of this rapid liquefying disease.
The disease, officially coined “sea star wasting disease” (SSWD), has affected over 20 species of sea stars from Mexico all the way to Alaska. A massive die-off in 2013 and 2014, which killed billions of sea stars, ignited the depreciation of marine ecosystems, particularly in the South Pacific. For a long time, the cause of this disease was unknown. Only in the past year has it finally been identified as Vibrio pectenicida.
Vibrio is a genus of bacteria that is well known and has greatly impacted shellfish, as well as humans. Vibrio cholerae is the pathogen that causes cholera.
The disproportionate impact on southern areas suggests that warmer waters intensify the effects of sea star wasting disease. A warming climate is a hurdle that the scientific community faces when considering options in fighting this disease.
While they may not look like it, sea stars are incredibly competent apex predators and a keystone species. These opportunistic predators can often be found in intertidal zones, like kelp forests.
Sea stars’ sudden decline means that their prey, sea urchins in particular, were left unchecked. As a result, sea-urchin populations boomed, causing overgrazing and the subsequent loss of kelp forest habitats. Kelp forests are largely made up of bundles of kelp that provide a vibrant and well-protected habitat to over 1000 species, as well as producing a large amount of our oxygen.
The sunflower sea star, a large and predominantly active member of the sea star species with up to 24 limbs, has been especially vulnerable to this disease, with some areas experiencing a 99% decline.
This means that their presence was essentially wiped out from Washington all the way to the northern coast of Mexico, where they are now considered extinct. They are officially a part of the International Union for Conservation of Nature (IUCN)’s critically endangered list.
However, for some mysterious reason, sunflower sea stars in the western tip of Alaska seem to be doing much better, with only a 40% decline.
The Alaska Sea Life Center, in collaboration with the Aquarium of the Pacific, Birch Aquarium at Scripps Institution of Oceanography, California Academy of Sciences and the Sunflower Star Lab, has been working to spawn and reintroduce populations of the sunflower sea star to the wild as part of the SAFE (Saving Animals From Extinction) Sunflower Sea star program. These institutes have been working together to collect reproductive cells from spawning male sunflower sea stars, which are then cryopreserved and used to fertilize eggs from female sunflower sea stars.
The first objective is to “significantly contribute to reintroduction of sunflower sea stars to historical ranges by providing genetically diverse and robust aqua-cultured juveniles.”
Along with this major effort, scientists at the Friday Harbor Laboratories and the US Geological Survey (USGS) Marrowstone Marine Field Station have successfully solved what was causing this cryptic disease.
The pathogen Vibrio pectenicida was identified as a causative agent of the sea star wasting disease epidemic through a series of experiments where healthy sunflower sea stars were exposed to sea star wasting disease, and then further tested by isolating different pathogens.
A pathogen is any organism or agent that causes disease in its host. Now that the pathogen of sea star wasting disease has been identified, scientists can start working on the recovery of sea star populations by screening for the presence of the pathogen in the wild, while conducting experimental research in the lab, which will be crucial to curing and restoring the ecological impact on our sea stars.
Sunflower sea stars are living on the brink of extinction across our western coast. However, active human efforts are being made across the country to prevent another mass extinction that would seriously affect our ecosystem, the success of which would be a major milestone in restoration and ecology sciences.
