Why in news?
Marine biologists recently identified Vibrio pectenicida, a bacterium, as the agent causing sea star wasting disease (SSWD), which has decimated sunflower sea star populations across the Pacific since 2013.
About the sunflower sea star
- Its scientific name is Pyncnopodia helianthoides. It is one of the largest and fastest‑moving sea stars and can have up to 24 arms.
- Habitat: found in the Pacific Ocean from Alaska to Baja California, dwelling on kelp beds and rocky reefs in temperate coastal waters.
- IUCN status: listed as Critically Endangered due to massive declines from SSWD.
- Key features: can reach about 1 m in diameter; moves at speeds of up to 1 m per minute using thousands of tube feet; possesses 16–24 flexible arms that help it capture prey and evade predators.
- Ecological role: acts as a top predator on sea urchins, clams and other invertebrates, helping maintain kelp forest health.
- Colouration: exhibits vibrant hues—orange, purple, red or brown—that aid camouflage and warning displays.
What is Vibrio pectenicida?
- A pathogenic marine bacterium previously known to affect shellfish. It has now been conclusively linked to sea star wasting disease.
- Researchers found high concentrations of the bacterium in the coelomic fluid (the internal fluid analogous to blood) of dying sea stars.
- The strain FHCF‑3 causes external lesions that quickly progress to twisted arms, tissue decay and death, often turning the animals into a mucus‑like mass within days.
- The bacterium thrives in warmer ocean conditions, suggesting that rising sea temperatures may worsen outbreaks.
Ecological impact
- Keystone species loss: Without sunflower sea stars to control sea urchins, urchin populations explode and overgraze kelp forests.
- Kelp forest collapse: Northern California has lost about 95 % of its kelp cover since 2013, with knock‑on effects on fisheries, biodiversity and coastal protection.
- Cultural and economic damage: Indigenous communities and recreational divers lose a charismatic species, and the loss of kelp reduces carbon sequestration.
Way forward: Monitoring ocean temperatures, managing urchin populations and developing breeding programmes may help restore sunflower sea star numbers. Reducing global greenhouse‑gas emissions will be crucial to control such marine disease outbreaks.
