Kelly Fretwell

Sea Star Wasting Disease

Sunflower Sea Stars are one of the largest and fastest sea stars in the world’s oceans and a decade ago they were a common sight from Mexico to Alaska. Now this once abundant predator is missing from most of its range. The Global population has shrunk by over 90%, a decline that recently earned them the ICUN Red List status of “critically endangered.” 

“So what happened?”

“Beginning in 2013, sea stars were hit hard by an underwater epidemic known as Sea Star Wasting Syndrome: A condition that literally turns them into goop. Sunflower Stars were particularly devastated. The disease killed an estimated 5.75 billion Sunflower Stars, the biggest marine wildlife disease outbreak on record.” – from the Hakai Institute video Sunflower Sea Stars Now Critically Endangered.

According to Kelly Fretwell, from the Hakai Institute, the first people to notice this new disease were divers, but it very quickly spread throughout the West Coast. It has affected at least twenty species, including the iconic Sunflower and Ochre Sea Stars. She describes it as a devastating blow to the ecology, but also a fascinating case study for understanding the role these species play on the coast.

Photo courtesy Hakai Institute

Why Sea Stars are important

“As a result, Hakia researchers have found that the Sunflower Sea Star has a huge impact in keeping sea urchin populations s in check. That keeps kelp forests healthy and intact,” she said.

Speaking as someone raised on the West Coast, Fretwell also enjoys going to the beach, poking around the intertidal region and finding Sea Stars in tide pools.

‘I think the loss of sea stars, due to Sea Star wasting disease, means there has been the loss of that iconic bright purple or bright orange, in the case of the more common Ochre Sea Star species, from the shoreline, From talking to people, this seems to be something that is felt and there is a lot of interest in how sea Stars are doing since the epidemic hit,” she said.

Signs of Sea Star Wasting Disease

The initial signs of the disease are white lesions on the sea star’s tissues, their bodies or arms. Then their tissues start to disintegrate and limbs come off. Eventually, the sea stars body melts away into ‘goop.’

“The disease is by no means gone and the exact cause is still being investigated, but there is definitely a link with warmer waters, Sea Star wasting is found in larger numbers of Sea Stars and progress more rapidly in warmer waters,” said Fretwell.

She added, “Seeing these animals disintegrate in front of you is really quite sad,” said Fretwell.

Hakai has initiated a study to find out where pockets of Sea Stars have survived, how extensive they are and what are their chances of survival.

Sea Star Wasting disease
Sea Star Wasting Disease – courtesy Grat Callegari, Hakai Insitute

The first of three

This is the first in a series of three articles. Those that follow deal with:

  1. A tale of sea stars and oysters from Gorge Harbour, on Cortes Island, and what it means in a larger context.
  2. How the Friends of Cortes Island (FOCI) became Hakai’s first partners in a new citizen scientist sea star monitoring program.

(There are more details in the podcast).

Sea star Wasting Disease
Another view of Sea Star Wasting Disease – Kelly Fretwell photo, Hakai Institute

Links of Interest:

top photo credit: Kelly Fretwell – photo by Koby Michaels, Hakai Institute

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