How a determined marine biologist and volunteers saved a giant kelp forest off California’s coast

Thirty years ago, the giant kelp forests in the ocean off the coast of California were mostly wiped out by ecosystem imbalances. Now a citizen-led effort has helped to restore them.

Giant kelp is the largest type of seaweed in our oceans. But the fragile ecosystem that supports its growth began to collapse after the area’s sea otters were wiped out in the 1840s. With the sea otters gone, sea urchins flourished and were free to devour all the kelp they could eat.

In the 20th century, water runoff from paved streets made conditions worse. The final straw, was the El Niño event of 1983, which ripped out nearly all the area’s kelp. After that, environmental pressures prevented it from growing back.

Marine biologist Nancy Caruso, who led the restoration effort, likens a healthy underwater kelp forest to a cathedral with light filtering through the stained glass windows onto the floor. Sunlight dances through the long, amber blades of kelp, creating beautiful patterns of light, she says.

Kelp can reach heights of about 110 feet, but often grows in water less than 30 feet deep. When it reaches the surface, it spreads its length along the top of the water, creating a canopy. The canopy provides cover for fish that are swimming up and down the coast following plankton and the ocean currents. They can hide underneath the canopy from predators like pelicans and other diving birds.

Prior to the 2014 hurricane, Caruso says she and her team believed their restoration efforts had been successful, but needed confirmation from Mother Nature. The real test comes, she says, when a hurricane or large ocean swells rip out all of the kelp. This is a natural occurrence — like a forest fire that burns so new life can begin.

The hurricane ripped out about 95 percent of the area’s kelp, creating big holes in the canopy of the forest. In a healthy ecosystem, new kelp begins to grow from the bottom up — which is what Caruso is seeing right now.

“When the kelp returns immediately after an event [like this], then we know that our restoration efforts are successful,” Caruso says. “After 30 years of our local ecosystem not having healthy kelp forests, we can rest assured that it's now restored and everything is back to normal again.”

Caruso’s mission began 12 years ago, when she founded a non-profit organization called Get Inspired!, with the mission to restore the kelp forests to their former glory. At the time, there was only one kelp forest left in Orange County.

She and a team of volunteers collected the reproductive blades from the kelp plants and took them into local classrooms for the students to clean and care for.

“We would leave them out of water, in the refrigerator, covered with paper towels, and then the next morning we would put them back in the ice-cold seawater and the kelp blade would release millions of spores,” Caruso explains.“

They would place the microscopic spores on small bathroom tiles and the kids would raise them for about four months in tiny nurseries built from Home Depot parts and fittings. Once the spores were visible to the naked eye, they would take the tiles out to the ocean.

Then, teams of volunteer divers would take the tiles into the ocean and attach them to the reef with small rubber bands. Each tile held thousands of kelp spores and the root system, called the holdfast, would grow off the tile and attach itself to the reef.

“The tile is non-leaded and unglazed so it could actually biodegrade, and the rubber band is biodegradable, too,” Caruso explains. “There is still kelp out there that started off from our tiles, so it's really gratifying to see that.”

This article is based on an interview that aired on PRI's Living on Earth with Steve Curwood