The discovery of the cause of sea star wasting disease (SSWD) represents a major breakthrough in understanding one of the most significant marine wildlife epidemics ever documented along the west coast of North America. A decade after the disease began devastating sea star populations from Alaska to Mexico, an international research team identified a strain of the bacterium Vibrio pectenicida as the primary cause of SSWD.
Led by researchers from the Hakai Institute, the University of British Columbia (UBC), and the University of Washington, the study combined field observations, microbiology, and laboratory experiments to identify the pathogen responsible for a disease that has killed billions of sea stars across more than 20 species since 2013.
This discovery provides a critical foundation for understanding sea star recovery, investigating how environmental conditions such as warming oceans influence disease outbreaks, and developing strategies to restore affected marine ecosystems. The findings are especially important for the recovery of the sunflower sea star (Pycnopodia helianthoides), a keystone predator that plays a critical role in maintaining healthy kelp forest ecosystems by controlling sea urchin populations.
Partners
Lead Research Organizations
Hakai Institute
University of British Columbia (UBC)
University of Washington
Research and Funding Partners
The Nature Conservancy
Tula Foundation
U.S. Geological Survey (USGS) Western Fisheries Research Center
Washington Department of Fish and Wildlife
The research brought together marine ecologists, microbiologists, disease specialists, and conservation organizations across Canada and the United States to solve a complex marine disease mystery.
Time Frame
Period | Milestone |
2013 | Sea star wasting disease emerges along the west coast of North America, causing widespread mortality |
2015 | Hakai researchers document impacts of SSWD on sea stars near Calvert Island, British Columbia |
2019–2023 | Multi-year investigation examines potential viral, bacterial, and environmental causes |
2023–2024 | Researchers identify Vibrio pectenicida strain FHCF-3 as the causative pathogen |
2025 | Findings published in Nature Ecology & Evolution |
The discovery followed more than four years of intensive investigation, building on more than a decade of observations and monitoring following the initial outbreak.
Context
Sea star wasting disease is one of the largest marine disease outbreaks ever recorded. Beginning in 2013, the disease caused dramatic declines in sea star populations along the Pacific coast of North America, affecting more than 20 species from Mexico to Alaska.
The impacts were particularly severe for the sunflower sea star, a large predatory species capable of growing up to the size of a bicycle tire and supporting healthy kelp ecosystems by controlling sea urchin populations. More than 90% of sunflower sea stars were lost during the outbreak, resulting in the species being listed as critically endangered by the International Union for Conservation of Nature (IUCN).
The loss of sunflower sea stars has had cascading effects throughout coastal ecosystems. Without this important predator, sea urchin populations can increase, contributing to declines in kelp forests that provide habitat, support fisheries, store carbon, protect coastlines, and hold cultural importance for coastal Indigenous communities.
Identifying the cause of SSWD was challenging because sea stars can display similar symptoms in response to multiple environmental stressors. Through detailed laboratory experiments, researchers were able to isolate Vibrio pectenicida from infected sea stars and demonstrate that exposure to this bacterial strain caused the disease.
Outcomes
The identification of Vibrio pectenicida as the cause of sea star wasting disease provides a critical foundation for understanding, managing, and recovering affected sea star populations. This breakthrough enables researchers to move beyond identifying symptoms toward investigating the environmental conditions that influence disease outbreaks, including the potential role of rising ocean temperatures and climate change.
The research has advanced understanding of the connections between marine disease, biodiversity, and ecosystem resilience. By clarifying the cause of sunflower sea star declines, scientists can now explore recovery strategies including disease resistance research, captive breeding, genetic studies, and targeted reintroduction efforts.
The findings also highlight the broader ecological importance of keystone species. Recovering sunflower sea stars could help restore natural predator-prey relationships, reduce pressure from sea urchin overgrazing, and support the recovery of kelp forests and the many species and communities that depend on them.
Beyond the scientific discovery, the project demonstrated the value of long-term ecological monitoring and collaboration among researchers, conservation organizations, and institutions. The knowledge generated through this work provides a pathway toward restoring resilient coastal ecosystems and improving understanding of how marine species respond to a changing climate.
