Sea Star Wasting Disease
The Pacific coast has witnessed a catastrophic decline in sea star populations since 2013. Over 5 billion sea stars have perished due to a wasting disease that causes rapid deterioration and death. Scientists have now identified the cause, marking a breakthrough in marine ecology and conservation efforts.
Outbreak and Symptoms
The epidemic began in 2013, affecting sea stars from Mexico to Alaska. Infected animals developed white lesions. Their arms twisted and detached. Within days, their bodies turned to mush. The sunflower sea star (Pycnopodia helianthoides) suffered the worst, with 90–94% population loss in five years. California alone lost 99% of its sunflower sea stars.
Identification of the Cause
A recent study identified the bacterium Vibrio pectenicida as the cause. This bacterium was found in high amounts in the coelomic fluid of sick sea stars but absent in healthy ones. Earlier research had missed this by focusing on dead tissue. Vibrio pectenicida is known to infect shellfish and thrives in marine environments.
Ecological Impact
Sea stars are keystone predators controlling sea urchin numbers. Their loss led to sea urchin population explosions. Urchins overgrazed kelp forests, wiping out up to 95% of kelp in northern California. This destroyed habitats and food sources for many marine species and affected fisheries. The die-off is one of the largest marine mortality events recorded.
Recovery Efforts and Challenges
With the cause identified, conservationists can now focus on protecting remaining healthy populations. Captive breeding and reintroduction are being explored. Researchers are investigating natural immunity in some sea stars and potential probiotic treatments. Rising ocean temperatures may worsen outbreaks by boosting Vibrio growth, linking the crisis to climate change.
Habitat and Biology of Sunflower Sea Stars
Sunflower sea stars inhabit intertidal and subtidal zones from Alaska’s Aleutian Islands to northern Baja California. They live up to 435 metres deep on rocky, sandy, and muddy substrates. As broadcast spawners, they require close proximity for fertilisation. Data on their populations is limited, but the disease has caused sequential declines from south to north.
Environmental Stressors and Research Focus
Disease remains the main threat to sunflower sea stars. The role of environmental stressors, especially those linked to human-driven climate change, is not fully understood. These factors are a major focus of ongoing research. Understanding their influence is crucial for future disease management and species recovery.
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