Hakai Magazine


No Sea Stars = Mussel Beach

Researcher Monica Moritsch tracks changes in an intertidal neighborhood when its main predator is gone.

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Directed by Adrienne Mason
Produced by Gord More

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Since June 2013, sea stars in the northeast Pacific Ocean have been dying in a most gruesome fashion. Lesions appear, tissues decay, limbs fall off, and death soon follows. Within just a few days the animal appears to have melted away. Scientists have honed in on death by densovirus as the leading suspect in this sea star wasting syndrome. And while it is alarming to watch, the loss of sea stars in the intertidal zone also presents an opportunity for researchers: what happens when you remove a predator like the sea star Pisaster ochraceus from the intertidal ecosystem?

Back in the 1960s, researcher Robert Paine, from the University of Washington, manufactured this scenario by handpicking the sea stars off a stretch of Tatoosh Island, Washington, and from this work articulated the concept of keystone species: a species whose presence or absence makes a marked impact in an ecosystem. But the 2013 outbreak of sea star wasting syndrome gives researchers like Monica Moritsch, a graduate student from the University of California, Santa Cruz, a chance to monitor changes as the sea star populations plummet and then, hopefully, begin to repopulate the intertidal zone. This video shows Moritsch at work near Long Marine Lab, Santa Cruz.