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Mass Sea Star Deaths Shake Up Marine Food Chain

SFU researchers uncovering effects of one of the largest wildlife die-offs ever recorded.

By Christopher Cheung 28 Jun 2016 | TheTyee.ca

Christopher Cheung is editorial assistant at The Tyee and covers urban issues and migration for other publications as well. Find his Tyee stories here.

The mass death of sea stars on North America's west coast in 2013 was one of the largest events of wildlife mortality ever recorded. And with millions of sea stars dying between Alaska and Mexico's coasts, the status quo of marine food chains has been transformed, scientists have found.

A wasting disease has been killing sea stars. It begins with lesions, followed by body fragmentation, then death. Since 2013, the seabed has been littered with their arms and discs. Researchers have linked some of the deaths to warming sea temperatures due to climate change and a transmissible virus.

"It took literally just a few weeks for some of the most abundant sea stars that we have in Howe Sound -- these are sunflower stars, up to a meter across -- to completely disappear," said Isabelle Côté, a marine ecology professor at Simon Fraser University.

Côté and other SFU researchers found that only one-tenth of sunflower stars in B.C.'s Howe Sound are left.

"There were a lot of questions," said Jessica Schultz, an SFU science masters student. "One of the big ones was: what is this going to mean for the surrounding marine community that sea stars live in?"

The SFU researchers found that green sea urchins, the stars' favourite food, are on the rise now that their predators have vanished. Urchins have since quadrupled in population, and have depleted kelp, their food source, by 80 per cent.

"This is a very clear example of a trophic cascade, which is an ecological domino effect triggered by changes at the end of a food chain," Côté said "It's a stark reminder that everything is connected to everything else."

No solution to the sea star deaths has yet been found.

Check out the full story at SFU's website here.  [Tyee]

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