MONTEREY — More than 150 Monterey Bay Area divers are undergoing training to help battle a type of urchin that is decimating kelp forests critical to several marine wildlife species, including the endangered sea otter population.
What began as an experiment in 2019 (https://bit.ly/3gbnZLs) off Lovers Point in Pacific Grove has blossomed into a full-fledged attack on purple urchins whose voracious appetite has turned areas of the bay’s Giant Kelp beds into barren landscapes.
The efforts to remove purple urchins, as well as red urchins along the Monterey Bay coastline, are important because kelp beds provide enormous benefits to marine wildlife and human populations alike.
For example, kelp can remove several times more carbon greenhouse gas than trees can. They also provide cover for otters to hide from sharks, mate and grip onto so they don’t drift onto shore.
Purple urchins have left by some estimates 95% of Northern California’s coast barren of kelp. (AP)Otters once numbered more than 100,000, but now their numbers have dwindled to 3,000 and their future is not guaranteed. The kelp is like underwater rainforests that have several tiers and a canopy, providing food and shelter for the animals of the coastline ecosystem.
But beginning in 2013-2014 much of the Sunflower sea star population began a die-off from a mysterious wasting disease along the North America Pacific Coast. It continues to kill sea stars today and as a result, the population of purple urchins, which the sea stars preyed on, have exploded and consequently laid waste to much of the kelp forests.
Keith Rootsaert, a Monterey diver who is heading up efforts to cull purple urchins from the coastline, said that at a recent webinar 152 fellow divers registered for training on how to participate in an organized method to reduce the urchin numbers. Rootsaert has trained diving instructors who will in turn train their clients and dive club members.
His website (https://g2kr.com/urchin-removal-petition) details the work that is being done at several places along Monterey Bay, most recently along Tanker’s Reef just off the breakwater from Del Monte Beach.
In a separate but synergistic relationship, Rootsaert also volunteers as a monitor for the nonprofit Reef Check that is working globally to log kelp forest and reef destruction. Dan Abbott, the Central Coast regional manager for Reef Check, said that for the most part, the destruction has stabilized, but that “urchin barren” areas are not recovering.
While Monterey Bay is suffering serious effects, it could be worse. Abbott estimates that 95% of the kelp forests along the coastline north of San Francisco have been decimated. The Mendocino coast is likely the worst hit, he said.
But there are areas of the Central Coast where kelp beds are not faring much better.
“The area around Point Pinos and Point Joe are completely barren,” Abbott said. “The seafloor is littered with urchins.”
A diver on the Monterey Bay coastal seafloor drills in bolts that will mark off areas of purple urchin populations to help with culling and monitoring. (Courtesy Dan Schwartz) OLYMPUS DIGITAL CAMERARootsaert said it is too early to tell how well the culling is working, but that momentum is growing to engage teams of divers to head down to the seafloor with welder’s hammers to kill the urchins. Hammers work best because after a ‘hammer blow it’s clear the urchin has been killed so subsequent divers won’t come along thinking the patch still needs to be cleared of urchins.
The work is clearly cut out for the volunteers. At many places on the seafloor urchins number more than 20 per square meter. To be truly effective Rootsaert said he would like to see those numbers reduced to 0.6 urchins per square meter.
“In a lot of places the urchin population has doubled since 2019,” Rootsaert said.
While the divers are increasing their numbers, the scientific community is stepping up its research into causes and perhaps solutions to the problem. Researchers and faculty at the Monterey Bay Aquarium, Moss Landing Marine Laboratories and UC Santa Cruz are all looking at ways to thwart the decline of the kelp.
“It’s so important since 50% of the world’s oxygen comes from the ocean and kelp does a great job of sequestering carbon,” Rootsaert said. “Kelp also dampens wave action that decreases coastal erosion.”