British Columbia

Sea star die-off led to worrying decline in B.C.'s kelp forest, research reveals

New research is shedding light on how sea stars enrich the B.C. coast — but it took a near-complete population die-off to reach that conclusion.

Central Coast kelp, which provides a key ecosystem, lost density as urchins bloomed

A kelp forest canopy off the B.C. coast. Sea urchins are voracious eaters of kelp and if left unchecked, they can overwhelm existing kelp supply. (Jenn Burt)

New research is shedding light on how sea stars enrich the B.C. coast — but it took a near-complete population die-off to reach that conclusion.

Scientists from Simon Fraser University have concluded sunflower sea stars play a critical role in the health of kelp forests off the B.C. coast.

The sea stars, along with otters, prey on sea urchins, which are voracious kelp eaters. Without the sea stars, urchin populations can explode and eat all the kelp.

"We showed that sea otters feed on large sea urchins, whereas the sunflower sea stars eat the small and medium-sized urchins that otters ignore," researcher Jenn Burt said in a statement.

"We observed kelp density was highest at reefs with both sea otters and sunflower stars."

A group of sea urchins devour kelp on the sea floor. (Jenn Burt)

Kelp forests, researchers say, are extremely productive ecosystems that provide habitat for other species and help remove carbon dioxide from the atmosphere.

In an interview with All Points West guest host Megan Thomas, Burt explained how the observations came after a massive sea star die-off along B.C.'s Central Coast.

The research began in 2013, she said — but in 2015 and 2016, sea star wasting disease swept through the B.C. population and killed 96 per cent of the creatures.

"We were seeing random detached sea arms and piles of sea star melted goo," Burt described.

The devastating loss did show the researchers what the environment would be like without sea stars. Once they began to die, the kelp forests became less resilient and lost 30 per cent of their density, while sea urchin populations increased 300 per cent.

The wasting disease is still out there, Burt says, and the sunflower sea stars are not recovering quickly.

"That means we're missing this key marine predator and it's altering the dynamics of how these ecosystems normally function," she said.

Listen to the full story:

New research is shedding light on how sea stars enrich the B.C. coast - but it took a near-complete population die-off to reach that conclusion. 6:56

With files from CBC Radio One's All Points West

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