Hungry urchins decimate kelp
Ecosystem off California in disarray after population explosion
NEWPORT (Oregon): Tens of millions of voracious purple sea urchins that have already chomped their way through towering underwater kelp forests in California are spreading north to Oregon, sending the delicate marine ecosystem off the shore into such disarray that other critical species are starving to death.
A recent count found 350 million purple sea urchins on one Oregon reef alone – a more than 10,000% increase since 2014. And in Northern California, 90% of the giant bull kelp forests have been devoured by the urchins, perhaps never to return.
Vast “urchin barrens” – stretches of denuded seafloor dotted with nothing but hundreds of the spiny orbs – have spread to coastal Oregon, where kelp forests were once so thick it was impossible to navigate some areas by boat.
The underwater annihilation is killing off important fisheries for red abalone and red sea urchins and creating such havoc that scientists in California are partnering with a private business to collect the over-abundant purple urchins and “ranch” them in a controlled environment for ultimate sale to a global seafood market.
“We’re in uncharted territory,” said Scott Groth, a shellfish scientist with the Oregon Department of Fish and Wildlife. “You can’t just go out and smash them. There’s too many. I don’t know what we can do.”
The explosion of purple sea urchins is the latest symptom of a Pacific Northwest marine ecosystem that’s out of whack.
Kelp has been struggling because of warmer-than-usual waters in the Pacific Ocean. And, in 2013, a mysterious disease began wiping out tens of millions of starfish, including a species called the sunflower sea star that is the only real predator of the ultra-hardy purple urchin.
Around the same time, the purple urchins had two excellent breeding years – and with no predators, those gametes grew up and are now eating everything in sight.
“I’ve seen some big-scale fluctuations in the populations of sea stars and urchins, but never on this magnitude,” said Steven Rumrill, lead shellfish expert at Oregon’s wildlife agency.
Scientists are not yet sure if climate change is responsible for the sea urchin explosion, but they suspect it plays a role in the cascade of events that allowed the purple urchins to boom. And kelp, already under siege from warming waters, is not as resilient as it once was, said Norah Eddy, an associate director at the Nature Conservancy California’s oceans programme