Mass Death of Sea Stars
For more than a decade, scientists on the Pacific coast of North America were baffled by a mysterious killer that was destroying sea stars. The mass dying, which began in 2013, affected five billion sea stars from Mexico to Alaska and continues to impact over 20 species.
The Culprit
The worst hit was the Sunflower Sea Star, which lost around 90% of its population in the first five years of the outbreak. After scientists followed numerous false leads and red herrings, they are confident that the killer was a bacterium that also infected shellfish. The breakthrough, published in the journal Nature Ecology and Evolution, solves "a long-standing question of a very serious illness in the ocean."
The Cause
Earlier efforts missed the real killer because they looked for the wrong type of virus or examined samples of dead sea stars, which no longer contained the physical fluid that surrounds the organs. However, the most recent study included a careful analysis of this fluid and found the pathogenic bacteria vibrio pectenicida.
Effects on the Ecosystem
The death of sea stars triggered a cascade of effects on coastal ecosystems. Without predators such as Sunflower Sea Stars, which eat almost everything on the sea floor, sea urchin populations exploded. In Northern California, this has led to the destruction of around 95% of sea kelp forests in the past decade – important underwater habitats, which are often described as "rainforests of the ocean."
Conservation Efforts
Scientists hope that their discovery could help save sea stars. The researchers are examining whether they should move the animals or breed them in captivity to later transport them into areas that have lost most of the population. They are also testing whether treatments such as probiotics could increase the immunity of the disease.
Global Action
The governments are meeting in Geneva this week to negotiate a global plastic contract that prevents plastics from disturbing the life of the sea, fishing, and tourism. The British government has called for a "bold and ambitious global agreement" to end plastic pollution by 2040. Marine Minister Emma Hardy said that the UK continues to play a leading role in the process of securing an effective contract that ensures sustainable consumption and production of plastics.
