What the Crash of Abalone and Invasion of Urchins Says About Ocean Health
If one word could ever have characterized the red abalone population of northern California, it might have been abundance. The coveted sea snails were so numerous in places that divers often found them stacked on top of each other two and three deep, their fat muscular feet — the prized edible part — spilling out from under their shells as they foraged for food. The animals eat algae, and for all of California’s modern history, they thrived in the lush coastal kelp forests of Sonoma, Mendocino and Humboldt counties.
Then, in an ecological millisecond, the abalone population crashed — smashed by a complex trophic cascade linked to global warming that has turned northern California’s rich kelp ecosystem into a gray and barren marine desert, plagued by an overpopulation of kelp-eating purple sea urchins.
The abalone fishery has been shut down, and there is no telling when — if ever — managers will reopen it.
“It could be decades,” says Sonke Mastrup, manager of the California Department of Fish and Wildlife’s invertebrate program.
Tristin McHugh, a biologist with the volunteer-based citizen science group Reef Check, which has been surveying the demolished ecosystem, says, “A lot of people often ask, ‘Will it open? When will it open again?’ My answer is that it will never be open again in the way it once was.”
The chain of events that caused the collapse began in 2013, when a mysterious disease wiped out many sea stars of the region, including the sunflower sea star, the chief predator or purple urchins. Their numbers promptly began to increase.
Almost simultaneously, the region’s sea surface temperatures spiked for reasons not entirely understood but probably related to global climate change. This event — nicknamed by media and scientists as “the blob” — caused a widespread die-off of bull kelp, which thrives in cold, nutrient-rich waters.
The kelp forests, hit by this double whammy, retreated as sea urchins exploded, and today the ecosystem lies in shambles. Urchins cover the rocky bottom — in some places literally — while plate-sized abalone shells litter the seafloor and beaches. Survivors of the species are facing starvation as they hunt for seaweed scraps in the surf zone. Millions of the snails have already died, prompting an emergency closure of the recreational fishery in 2018.
There seems to be no recovery in sight.
“We’re all just waiting now to see how far this goes and when it turns around,” says Josh Russo, a diver who has hunted abalone for almost 20 years and president of a diving and spearfishing advocacy group called the Watermen’s Alliance.
Now, Russo is one of dozens of divers and scientists who are trying to help the kelp — and the abalone — recover. Their battle strategy is centered around killing urchins in a handful of strategic locations. Over the course of 2018, Russo and other divers removed 1.2 million purple urchins from the water and sent them to a composting facility in Ukiah.
The idea is not to cull the entire population—certainly an impossible task. Rather, the hope is that divers can clear the urchins from small patches of seafloor so that bull kelp spores may lodge, take hold on rocks and grow into full-sized plants. Such pockets of restored kelp could then serve as seed banks from which the whole coast could be revitalized.
But such regeneration will be possible only if a powerful force — something far beyond the magnitude of human intervention — knocks down urchin numbers. There has been speculation that, eventually, the animals will starve, or that a disease could wipe them out. Some people have even contemplated capturing any sunflower sea stars that still survive in the region and — on the assumption that they possess a genetic resistance to the virus that destroyed their overall population — captively breeding them for release into the wild. This could theoretically bring the ecosystem back into balance.
For now, such hopeful outcomes serve as little more than dim beacons of hope, and the reality is that the north coast kelp forest could be a figment of picture books and memories for decades.
It’s a bitter pill for former abalone divers to swallow.
“I’m a lifelong abalone diver, and it hurts,” Mastrup says.
Mastrup’s department is working alongside Russo and the Watermen’s Alliance in urchin culling efforts. So are scientists at the Bodega Marine Laboratory and the Noyo Center for Marine Science, as well as several commercial urchin divers, whose target quarry species, the red urchin, is now languishing in a half-dead starvation state, with their prized golden gonads — marketed as uni — now shriveled and worthless. Reef Check is helping, too, by surveying the culling sites and watching hopefully for positive trends in the data.
The ecological shift of California’s coastal ecosystem represents a textbook example of alternative stable states, by which an ecosystem alternates between two drastically different realities. In the case of the kelp forest, the urchin barren is its alternative stable state — and vice-versa. Each system is resilient and stable, and it takes an extreme event or change in conditions to drive a shift from one to the other, but once the shift occurs, reversing it is very difficult. Several historic examples have demonstrated the extreme stability of the urchin barren state. In the coastal waters of southwestern Hokkaido, Japan, urchin barrens formed early in the 20th century and have persisted ever since, with virtually nobody alive anymore who can even remember when kelp forests grew vibrantly here. Urchin barrens have similarly persisted in the Aleutian Islands since the 1990s. Many divers and water lovers fear this long-term outlook will be California’s fate.
The reason that urchin barrens are so stable is the resilience of the urchins themselves that create them. Research published in 2014 found that individual urchins in Hokkaido have lived for 50 years without solid food. In other words, they never die, practically speaking, and they will outlive all competition for years after the last scrap of food has been eaten.
Biologist Cynthia Catton of the Department of Fish and Wildlife, who has been closely involved in the urchin removal program, says that urchins bereft of kelp will begin scouring the rocks of its crust-like coralline algae and have even been seen gnawing away at empty abalone shells.
Recently, McHugh was leading a Reef Check survey dive at Albion, in southern Mendocino County. She and her dive team placed white metering tape on the bottom to delineate the morning’s survey area.
“And within 15 minutes the urchins had crawled onto the tape and were chewing bites out of it,” she says.
It’s this type of voracious behavior, multiplied across tens of millions of urchins, that has locked California’s former kelp beds into their bleak new reality.
As for the red abalone, Catton says they, like the region’s urchins, are currently in a “reproductively depressed state.”
“This has a lot of implications for their ability to recover,” she says.
Mastrup adds that the animals grow very slowly — a complicating factor in restoring an abundant, sustainable fishery.
“Once they start breeding again, it’s still going to be 10 or 12 years before those animals have reached legal harvest size,” he says, referring to the longstanding 7-inch minimum shell diameter for “keeper” abalone.
Still, Russo, at the Watermen’s Alliance, remains optimistic. The abundance of red abalone in recent history “was a super artificially high population,” he explains, boosted by the eradication of sea otters in the 18th centuries.
“Before this all happened, they were stacked three on top of each other — you could get your [three-abalone] limit in one dive,” he says. “There was no other animal that you’re allowed to hunt where it was so easy to get your limit.”
Now, he says, “we’re seeing a more natural population.”
In fact, in some coves the abalone “look fat and happy,” according to McHugh. “They’re getting kelp from somewhere.”
But such sites are few and far between, and Catton cautions that the key problem has not been solved.
“Abalone are still starving, they’re still dying,” says Catton.
Mastrup says he is only marginally optimistic about the potential for urchin removal to alleviate the pressure on the north coast’s kelp long enough for the iconic groves to come back. Even if seed banks of adult kelp are established, there remains the challenge of holding the armies of voracious urchins at bay indefinitely.
ABOUT THE AUTHOR ALASTAIR BLAND
Alastair Bland is a journalist based in San Francisco who writes about the environment, agriculture, science and food. He has written for SmithsonianMag.org, Yale Environment 360, NPR, and the East Bay Express, among others.