How researchers are working to restore once-thriving kelp forest along Sonoma Co. Coast

ByDan Ashley and Tim Didion KGO logo
Tuesday, June 13, 2023
Kelp restoration project begins along Sonoma Co. Coast
U.C. Davis and marine researchers are working to restore a once-thriving kelp forest along the Sonoma County Coast.

SONOMA COUNTY, Calif. (KGO) -- A unique ocean-going restoration effort is just getting underway along the Sonoma Coast and its goal is to rescue an underwater forest that's critical to marine life.

"So now we're giving the bull kelp a little haircut so they'll keep tumbling nicely. So they'll grow nice and healthy," says kelp restoration specialist Julieta Gomez.

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For Gomez and fellow marine researcher Rachael Karm, the weekly trims are just part of caring for lab-nurtured kelp specimens that will soon be part of the critical mission. To help restore a once-thriving natural population that's been decimated in recent years. The damage began roughly a decade ago, with a shift in the marine environment that killed off local predators like the sunflower sea star. That triggered a population explosion in another, competing, species, ravenous purple sea urchins, which feed on the kelp.

"So kelp loss has been a devastating issue along the Northern California coastline, particularly in Sonoma and Mendocino County. And so the scale of loss is incredible. It's over 90 percent since 2014," says Rietta Hohman, who's leading the cutting-edge kelp restoration project for the Greater Farallones Association and the Greater Farallones National Marine Sanctuary.

Working with the U.C. Davis Marine Lab at Bodega Bay, the group is growing their own colonies, which they hope to reintroduce to the shoreline. Enlisting the help of local divers to literally pluck the urchins and plant the kelp.

"We work with local commercial urchin divers to remove urchins, purple urchins, in particular, to reduce the grazing pressure on new kelp forest growth. And then we are also going to be out planting in these areas using a couple of different methods, Hohman explains.

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They say plucking the destructive urchins is pretty straightforward but figuring out what to do with them is a work in progress. Partner groups are experimenting with ideas like turning them into fertilizer or plumping them up for potential sale to local restaurants.

"There's very little variation in the color of the purple," says Karl Menard of the U.C. Davis Bodega Marine Laboratory.

But seeding a new kelp forest presents far different challenges. In rows of barrel tanks, the team is growing tiny kelp spores on long strands of twine that can be sunk in place with weights. Rows of lights mimic cycles of night and day as the team monitors their progress under the microscope.

"About every week or two we'll check under the microscope slides to make sure they're growing the way we want them to," explains Rachael Karm, who is based at the Hughes research lab at Sonoma State.

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Other strategies call for divers to plant bags filled with kelp spores, or even glue small kelp platforms directly to the underwater reef. While nobody's sure which strategy will be the most successful, anticipation is building with work expected to ramp up a little later this summer.

"And we get to be out there diving at these sites doing this incredible work, seeing these sites, recover, cross our fingers, knock on wood, and really forging a path forward that we hope will be able to be used both regionally and across the globe," says Hohman.

Sonoma State University and Moss Landing Marine Labs are also lead partners in the project. And for the Marine Sanctuary, it's a chance to restore an ecosystem that's critical for supporting sea life from abalone to rockfish and beyond.

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