On the coast of Northern California, two years of unusually warm water temperatures have wreaked havoc with the marine ecosystem. Kelp forests stretching from the Bay Area to the Oregon border have shrunk by more than 90 percent since 2008.
Cynthia Catton, a marine biologist with the California Department of Fish and Wildlife, says the size of a kelp forest varies from year to year, but the recent low levels are unprecedented. “We’re in a new phase,” she says.
Kelp beds play a key role in marine ecology. The fast-growing seaweed forms a habitat for juvenile fish, which hide in its stalks. It’s also a food source for many undersea animals, including abalone and urchins.
Catton says the kelp forests north of the Bay Area were hit by a “perfect storm of large-scale ecosystem stressors.”
It all began in 2013, when a wasting disease nearly wiped out sea star populations along the entire Pacific coast of North America.
Sea stars were sea urchins’ main predator. With sea stars in decline, urchins went on a kelp-eating rampage.
“I have a friend who calls them the goats of the sea,” says Catton. “They form these feeding fronts and they just munch through everywhere they’re walking.”
The next problem: Kelp need cold water. In 2014, oceanographers noticed an unusual warming in the Northern Pacific–even more than could be explained by climate science. For lack of a better term, they called it the “Pacific warm blob.” Then, last year’s El Niño made the water even warmer.
In the last three years, income for urchin divers in Mendocino County has plummeted by 90 percent.
The crisis has led to an alliance between fishermen and regulators. Both groups are concerned about the rapid decline of the kelp forest. Catton says that when they first met last spring, they “didn’t have to spend a lot of time thinking about what’s happening.” Instead, they thought about “what we can do together to solve it.”
Together, they’re experimenting with new methods of restoring the ecosystem.
Getting Rid of Purple Urchins
Jon Holcomb is an old-time urchin diver with the leathery skin of a man who spends a lot of time on his boat. For 42 years, Holcomb has made his living diving for red urchins. Their buttery insides are a delicacy in Japanese restaurants where they show up on menus as uni.
On a recent morning, he motored out to a cove by the town of Mendocino. It’s a test site, where Holcomb and a few other divers volunteered to help biologist Catton with a restoration effort.
Holcomb says when he first started fishing here in the mid-’80s, this area was “a complete mat” of kelp “you couldn’t swim through.”
Now, just a few dark green kelp heads bob in the water. “It’s like a lake,” says Holcomb.
The kelp here has been devoured by purple urchins. Compared to red urchins — the species that Holcomb harvests — they’re smaller, less meaty and not worth fishing for. And they’re voracious eaters of kelp. “Nothing can survive their appetite,” says Holcomb.
Now, many parts of the California coast north of the Bay Area have turned into what scientists call an “urchin barren.” There’s not much life besides a mass of spiny purple creatures carpeting the seafloor.
Paradoxically, these urchins keep reproducing even while they have little to eat. Holcomb calls them “starving animals that don’t die from starvation. They just keep breeding, and there’s more and more of them every year.”
As part of a pilot project with the Department of Fish and Wildlife, Holcomb has been diving underwater to remove masses of purple urchins. He’s hoping that their effort to remove urchin in a few test sites will allow kelp to grow back in the spring.
The challenge is collecting thousands of urchins at a time.
A Homemade Underwater Vacuum Cleaner
Holcomb assembles the device he’s developed for just this purpose. He slaps together 10-foot-long pieces of fiberglass tubing to make a sort of homemade underwater vacuum cleaner.
It’s a modified version of a tool called an airlift, which is used to clear sand and silt from the seafloor. This one is built for purple urchins.
In videos he’s made of his method, the seafloor looks like a minefield of spiky purple creatures. Holcomb puts on his scuba gear and connects the pipes to an air compressor on deck. Then he dives down with the equipment to depths of about 30 feet.
He uses a little metal rake to scrape the urchins off the rocks and into his fiberglass tube. The device sucks the urchins up and deposits them into a large net.
It takes him almost two hours to clear off an area smaller than a tennis court.
When he finally comes up, his net is packed with thousands of purple urchins with wiggly spines. They’re much lighter than the same number of urchins would be in a healthy kelp forest.
Holcomb smashes one open to show that there’s almost no flesh inside. “They’re all empty,” he says. “There’s no food value in them.”
We head back to a dock in Fort Bragg, where Catton has brought a group of local volunteers to count and measure the urchins.
“We want to be able to say, ‘How much effort does this take?’ ” says Catton. “How effective is this on a small scale? How can we expand this effectively? And if not, what do we need to do differently?”
In a few months, her team will return to the test sites to find out if the divers’ efforts have enabled kelp to grow back. But even if their experiment succeeds, the problem of restoring the entire coastline is vast.
“It’s much like trying to scratch the paint off a house with a pin,” says Holcomb. “It’s not gonna be easy.”
Recently though, a few changes in the ocean may point toward a recovery for the kelp forest.
The warm blob in the Pacific has abated. The coastal storms of the last few months have cooled off the ocean, and water temperatures are closer to normal.
Additionally, many sea star populations along the coast appear to be recovering. If the baby sea stars survive to adulthood without dying of the wasting disease, they could help bring balance back to the ecosystem by eating the urchins that have been destroying kelp forests.