Quick Take
More than 90% of kelp forests have disappeared in Northern California after a devastating underwater heat wave struck the coast. Now, researchers at UC Santa Cruz are trying to save what was left behind in a new study that helps expand and protect surviving kelp forests by selectively removing sea urchins.
Monterey Bay might seem like one unified stretch of blue on the surface, but the seafloor is severed into two distinct worlds: wastelands and wilderness. In some areas, giant kelp forests’ sprawling canopies create thriving habitats for around a thousand sea creatures. But in others, miles of sea urchins carpet the bottom of the ocean in stretches devoid of life called urchin barrens.
Alec Scott, a scientific diver from UC Santa Cruz, is helping carve out a space in between these two worlds in hopes of expanding and protecting the remaining kelp forests left behind from a devastating underwater heat wave.
Scott is part of a team of 15 researchers with the Raimondi-Carr Lab who are diving beneath the waters of Monterey Bay to create urchin-free zones next to the boundaries of these healthy giant kelp forests.
As part of the two-year study, the researchers are testing nine underwater sites where kelp forests bump up against urchin barrens. Divers removed sea urchins on either side of the barrens and the remaining forests to create four different clearings that vary in size. The healthy forests can then grow into the urchin bald patches and expand their range.
If the researchers are successful, they hope to change the focus of kelp restoration efforts. Traditional restoration methods center around removing barrens entirely or planting new kelp forests from scratch — a labor-intensive and costly process. But this project shifts the attention to surviving kelp forest, creating a cheaper and less physically demanding way to restore kelp forests and manage the sea urchin population boom.
“What’s fundamentally different here is that we’re combining the protection and expansion in the restoration effort,” said Mark Carr, principal investigator of the kelp restoration project.
With more than 700 dives under their weighted belts, the researchers have tediously culled thousands of urchins with crowbars and hands sheathed in thick neoprene gloves.
To get urchins out of hard-to-reach places more efficiently, Scott even used a metal spoon from his own kitchen to get the job done. “Earlier on, I thought maybe I’d just remove the urchins without the gloves,” Scott said. “But it’s just spiky down there.”
On one of their last dives of the season in late October, Scott and the project’s driving field technician, Allison Coughlin, disappeared into a burble of bubbles as they descended toward a research site in front of the Monterey Bay Aquarium. They have clocked more than 600 hours underwater monitoring and maintaining these sites.
Though Coughlin has spent plenty of time observing this now-desolate landscape, the barrens still spook her.
“It really does feel like a cemetery,” she said. “The urchins are in their zombie state.”
Sea urchins are kelp’s main predators and love to chomp on kelp’s leaflike fronds, called blades. Just like leaves in land forests, blades fall to the sea bottom when they die — settling into the gaps between rocks where sea urchins live. But in 2014, the largest marine heat wave on record wiped out this once-reliable food source.
Aptly coined “the Blob,” the unusual mass of warm water smothered the coast of Northern and Central California for two years. Ocean temperatures spiked and nutrient levels plummeted, unleashing an underwater death bath. Kelp, which thrives in cold and nutrient-rich water, became suddenly scarce.
The event caused more than 90% of kelp in Northern California to disappear, including the forests near Point Lobos, a popular tourist destination in Carmel-by-the-Sea. “It was visited by so many people and is renowned for its beautiful kelp forests, ” Carr said. “When that kelp was gone, people went ballistic.”
Before the marine heat wave, urchins stayed tucked away in craggy crevices with few reasons to leave their home. But that changed when the kelp vanished.
“The sea urchins went nuts,” Carr said. “These blades were being delivered to them like pizzas. But when you reduce the availability, the urchins come storming out looking for food.”
The remaining kelp forests were defenseless against urchins’ vigorous appetite. Starved, the urchins began mowing down any kelp they could find — adding to the stressors faced by remaining kelp forests. As new kelp spores tried to grow, the young sea plants were wolfed down by starving urchins that were wasting away in neighboring barrens. When there was no food left, the barrens formed.
Two other factors have encouraged urchin barrens to grow at alarming rates.
Once living in a barren, sea urchins exist in a condition that is close to death. Though they have a limited food supply for a growing population, urchins continue to survive by absorbing just enough nutrients through their skin.
Malnourished, their reproductive organs stop developing, which is the only part of the urchin that predators eat. No longer appetizing to hunters like sea otters, urchins have no natural threats and expand rapidly.
To make matters worse, a pink algae called encrusting coralline algae sprouts up once barrens are established. Coralline produces a chemical that attracts urchin larvae into the barrens. Instead of settling in a balanced ecosystem with enough food, the larvae grow into adults in a forever zombie state.
“I think if I was a diver that didn’t have this background, I would probably think of the barrens as pretty because it’s just pink coralline on the rocks and purple urchins,” Coughlin said. “But then you think about how that was once a kelp forest. … There’s just so much less biodiversity, less fish, and just a lot less everything. It’s replaced with urchins.”
After monitoring the urchin-free zones for months, the researchers will return next season to see if the kelp forests successfully expanded their boundaries. The team hopes that this study will help policymakers not only better understand what conditions encourage surviving forests to thrive but also the amount of resources needed to execute this restoration plan.
“A part of this that is really important is not science at all,” Carr said. “We’re also trying to estimate how much time and how frequently you have to go down and remove these urchins in order to achieve both the protection and the expansion of the forests.”
Coughlin is hopeful the team’s hard work will pay off. Even after spending so much time among the sequoias of the sea, she is still in awe of giant kelp’s beauty and versatility.
“You really get to be a part of that world and see firsthand how there are so many more species that you will see on one dive compared to a walk in a land forest,” said Coughlin. “From a diver’s perspective, a kelp forest is the most beautiful thing you could ever lay your eyes on.”
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