In late January, a heavy rainstorm soaked the Big Sur coast, a place recently scarred by California’s worst fire season on record. As the water washed over charred soil, it picked up debris. Rocks and boulders formed what looked like a bulky head, a tail of murky water the consistency of wet cement following behind. Upon reaching the shore, several of these slides, known as “debris flows,” rushed into rocky intertidal habitats.
A few weeks after the storm, in early February, eight scientists with a research consortium called the Multi-Agency Rocky Intertidal Network, or MARINe, hiked towards a beach smothered by one of the Big Sur debris flows. The sour smell of decomposing creatures hit them. A few turkey vultures nipped at the sand. There were dead sea stars, chitons, and likely hundreds of dead black abalone. In a previous visit to this site, scientists were able to count 150 black abalone or “abs” in a small 50-meter area, with hundreds left uncounted. A fraction of the site’s population remained.
Listed as endangered in 2009, black abalone, with their distinctive greenish-black, oval outer shell and pearly underside, have suffered tremendously in the last 30 years due to a chronic, lethal wasting disease. Prior to that, overharvesting contributed to their decline.
Last summer, Wendy Bragg, a marine ecologist who works with MARINe, feared black abalone might take another hit as she watched fires burn along the coastline from Santa Cruz to Big Sur. “Seventy percent of our healthy [black] abalone populations coincide with where these fires were,” she says. “They are in these deep cracks and under boulders. So if you get a debris flow or landslide, they would get buried under the sediment. Or [the sediment] would gather in those cracked areas and knock them loose.”
Bragg, who also has a background in fire ecology, now focuses her research on conservation and recovery strategies for black abalone, a species found only in California. She says studying how fire might impact ocean creatures is “kind of a new thought.” But California is growing warmer and drier due to climate change, which could result in longer, more severe fire seasons. Research shows rain events in California may also become more intense, setting up the possibility of more frequent coastal debris flows.
In the fall, knowing winter rains were coming, Bragg and MARINe, with the support of the National Marine Fisheries Service (NMFS) and the California Department of Fish and Wildlife, started making plans to rescue black abalone if debris flows should pose a risk. Since MARINe has documented abalone populations for 20 years, scientists knew where on the coast to find them. In the weeks leading up to the storm, Bragg completed additional surveys, even taking photos and using GPS to mark specific places that could be impacted.
Smoke from a 2016 wildfire near Big Sur. California is growing warmer and drier due to climate change, which could result in longer, more severe fire seasons. Research shows rain events in California may also become more intense, setting up the possibility of more frequent debris flows along the coast as rainwater flows over fire-scarred areas. Photo by l@mie.
Listed as endangered in 2009, black abalone have suffered tremendously in the last few decades due to overharvesting and a chronic wasting disease. Now, debris flows threaten their survival. Photo by Steve Lonhart/NOAA Monterey Bay National Marine Sanctuary.
In early February, when the scientists returned to five established sites, they found unrecognizable landscapes. “It was startling to see how much things changed in some areas,” Bragg says, adding that in one location a rocky narrow strip of coast turned into a wide, sandy beach after sediment fanned out and waves deposited layers of sand. In another location, a van-sized boulder had vanished, presumably shoved into the ocean. “When you see areas where there was so much sediment shifting in the [black abalone] habitat, the likelihood of them surviving there was very little.”
Bragg discovered abalone covered by three or four inches of sediment; one lay motionless upside down in the sand. “This is not a species that is ever near sand,” Bragg explains. “They’re typically in the intertidal, between high and low tide.”
Over three days, abalone experts with the team carefully removed about 80 black abalone from three heavily impacted locations. They were gently placed in a mesh bag and dampened with wet rags as scientists continued their work. (Black abalone are unlike other abalone species as they do not need to live submerged in water.) With each rescued abalone, a slip of waterproof paper noted when and where it was found, in hopes of returning them when the habitat had stabilized. At day’s end, Bragg loaded the abalone in a soft, cloth cooler and strapped it to her body, in front like a baby carrier, as she hiked out to quickly get them into tanks.
Removing black abalone is not easy. (It’s also illegal. Law forbids even touching one, but NMFS gave authorization for this rescue project.) An abalone foot works like a massive bicep gripping the rock. Without expertise, prying abalone loose can cause injury or death to the invertebrate. “We only made these decisions because we felt like their chance of survival was so low there, that the risk of injury was offset by the potential to rescue them and get them to a safer area,” Bragg explains.
Steve Lonhart, a research specialist and unit diving supervisor with the Monterey Bay National Marine Sanctuary, says debris flows along this stretch of coast are common. “Big Sur is an active place,” he says. “Those hills are constantly going into the ocean.”
In May 2017, Lonhart recalls, an event known as the Mud Creek landslide was so large it added 15 acres of new land to California’s coastline. “I always try to make sure people understand that there’s an initial event, which in the case of Mud Creek was a massive landslide that came down,” Lonhart says. “But the ocean is moving back and forth, which is creating this action.”
Sediment can move up or down the coast. For months after the landslide, biologists used drones to keep tabs on how the sediment crept outwards. By October of that year, it became clear that a large population of abalone was at risk of being buried. Forty were removed, tagged, and either relocated to safer habitat or kept by NOAA scientists for ongoing research.
That experience led to the creation of a “Black Abalone Translocation Manual” finalized this past June. Prepared by UC Santa Cruz researchers for the Monterey Bay National Marine Sanctuary, the manual helped guide Bragg’s work this winter.
The 80 removed abs from Big Sur’s recent slides now reside comfortably in tanks, eating kelp brought in by a kelp harvesting organization. The plan is to hopefully return them to either their original habitat or somewhere nearby by summer.
Pete Raimondi, a UCSC professor of ecology and evolutionary biology who acts as the principal investigator on the abalone removal project, says it’s hard to know how many of California’s black abs have perished due to recent debris flows. Steep terrain and dangerous swells make it hard to access a number of sites. But because so much of black abalone habitat was in the direct line of Big Sur slides, Raimondi is certain there’s been great loss. “We don’t want to underestimate the scale of what’s going on,” he says. “It could be vast.”
Scientists will continue to watch how sediment moves along the coast, possibly activating another rescue. Bragg says the work is crucial, not just for the endangered species, but the whole of California. “Culturally, abalone are so important, especially to native populations. People light up when they see [abalone],” she says. “To lose something so beautiful would be tragic. We are doing what we can to ensure that doesn’t happen.”
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