‘An eco-disaster’: Kelp forests disappearing off the coast of La Jolla for unknown reasons

The kelp forests off the coast of La Jolla are disappearing, and local scientists are stumped as to why they’re not recovering.

The two largest kelp forests on the West Coast — off La Jolla and Point Loma — have been slowly getting smaller amid rising ocean temperatures, especially in the kelp beds off northern La Jolla between Marine Street Beach and La Jolla Shores.

Kelp beds off southern La Jolla have shown patchy regrowth, but those in northern La Jolla appear decimated.

“I’m not sure why that is,” said Ed Parnell, a marine ecologist at UC San Diego’s Scripps Institution of Oceanography in La Jolla. The La Jolla kelp “should be doing better than it’s doing,” he said.

A 2014 heat wave, followed by a 2016 El Niño — which resulted in a series of warmer storms — resulted in “massive kelp mortality” all along the West Coast, Parnell said.

Cooler water in 2017-18 led to sporadic recovery, he said, though another warm-up in 2019 again diminished the forests.

Temperatures in the northern La Jolla kelp areas are a bit higher than in the southern portions, but “not enough to account for … the complete lack of kelp recovery,” Parnell said.

“I’m trying to understand what’s going on,” he said.

A still from a May video of northern La Jolla ocean waters shows virtually no remaining kelp.

(Ed Parnell)

There are several potential reasons for the kelp’s failure to regenerate, including disease, competition for space with other species of algae and a lack of light in deeper waters needed for growth.

The kelp forests are both a home and a food source for several species. Individual kelp plants can live eight to 10 years and regrow quickly.

Sea urchins often are the cause of kelp eradication, as they feed quickly on the kelp. But “right now, we don’t have a sea urchin overgrazing problem off San Diego County,” Parnell said. That problem is more contained to California’s central coast.

Finding the cause of the kelp’s decline will take time, Parnell said. It’s difficult to test for individual factors.

“The answer is probably going to be complicated; it’s probably several factors, and the timing of those factors has come into play,” he said.

With another El Niño on the horizon for next winter, which portends warmer water, “we’re going to lose what little kelp has come back,” Parnell said.

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Scuba diver Rod Watkins has watched the decline for more than a dozen years.

The loss of the kelp “has had a dramatic effect on the ecosystem,” Watkins said, “because many species of fish use the kelp canopy as a home. … You used to be able to find an abalone in the reserves under almost every rock. Today, you can hardly find an abalone out there. It’s sad … it’s an eco-disaster.”

Watkins, the owner of Scuba San Diego Inc., has led dives into the kelp forests off San Diego since 1968 and said the local kelp has “been completely degraded due to [increasing] ocean temperatures.”

Though the kelp decimation hasn’t affected his business “because people still want to come and see” what little is left, it’s “nothing like what there was 15 to 20 years ago,” Watkins said.

The surface of the ocean “[used to] be covered with kelp canopy” from south of Point La Jolla to the Marine Room restaurant in La Jolla Shores, he said. “I haven’t seen that in 15 years.” ◆