West Coast
A group of divers working on the Giant Giant Kelp Restoration Project in Monterey Bay are trying to restore the plant they say is under attack from a proliferation of purple urchins. (Karl Mondon/Bay Area News Group)

CA - Hammer-wielding scuba divers clear sea urchins from ocean floor to restore giant kelp in Monterey Bay

MONTEREY — On a recent Saturday morning, scuba divers Keith Rootsaert and Dan Schwartz splashed into the ocean just east of Old Fisherman’s Wharf, the chilly water swallowing the sounds of Monterey Bay as they descended. Upon reaching the seabed, each diver grabbed a spiky purple sea urchin, braced it against a rock and pulverized its center with a welding hammer — all in the name of saving giant kelp.

“Urchin culling” is an intervention — not a massacre. The intervention is necessary because the urchins are devouring the kelp.

The two divers needed to ensure the urchins were dead, but they didn’t have time to waste. Their goal was to kill hundreds of urchins apiece before the hourlong dive was over.

“Urchin culling” is an intervention — not a massacre. The intervention is necessary because the urchins are devouring the kelp.

Rootsaert describes kelp forests as the marine equivalent of California’s redwood forests. “If the redwood forests were on fire, people would be working tirelessly to save them,” he said. “The kelp forests need saving, but because they are out of sight in the ocean it’s harder to get people to care.”

A 57-year-old building systems engineer who lives in Monterey, Rootsaert founded the nonprofit Giant Giant Kelp Restoration Project in April 2021. Since then, he has taken over 150 volunteers on more than 1,200 dives to cull more than 563,000 urchins.

Urchins are not an invasive species. The native creatures normally hide in crevices on the ocean floor, eating kelp that drifts down from the forest’s canopy. But a perfect storm of events beginning a decade ago threw the coastal marine ecosystem out of whack.

In 2013, a mysterious wasting disease wiped out the sunflower sea star, a voracious urchin predator with up to 24 limbs. From 2014 to 2016, the kelp forests languished through a persistent Pacific marine heat wave known as “The Blob.” Much of the kelp couldn’t take the heat. And without predators to keep them in check, the hungry urchins stormed out from their nooks and crannies and decimated the remaining kelp.

The event ravaged Pacific kelp forests from Mexico to Alaska. California’s North Coast lost 95% of its bull kelp forest. The Central Coast lost two-thirds of its giant kelp forest.

The Monterey Bay’s kelp forests used to support more than 1,000 marine species, including fish, snails, crabs and charismatic sea otters. But many of those species moved on when the urchins moved in.

Rootsaert founded his kelp restoration project in the hopes of restoring the ecological balance.

Divers cull the urchins at a 100-meter square test site called Tanker’s Reef. A nearby site is left untouched so that scientists can compare results.

The experiment is a collaboration with environmental groups like Reef Check, which monitors the health of kelp forests along the West Coast, and government agencies such as the California Department of Fish and Wildlife and the Monterey Bay National Marine Sanctuary.

Rootsaert’s group relies wholly on volunteer scuba divers. “Volunteers are the best answer,” Rootsaert said. “You are building an effort that will sustain itself over time because you have people acting as ocean stewards.”

Volunteer Paul Souza, a 40-year-old licensed therapist from Fresno, started diving in Monterey Bay as a teenager in the late ’90s, which he describes as “the days of the infamous kelp crawl, where the kelp was so thick you’d have to crawl over it.” But when he returned in 2020, the kelp was gone and the urchins were in charge.

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