Skip to main content
logo sos

Sea Otter Savvy

Sea Otter Science And Community Outreach

The Spore Solution: Helping Kelp Forests Regain Their Former Glory

Bull kelp (Nereocystis luetkeana) canopy in Drake's Bay, California. Photo by Dan Gossard

A novel restoration technique could add to the efforts aimed to solve the kelp conundrum in northern California…

kelp urchinbarrens zackRandellA purple urchin barrens in California. Photo by Zach RandellImagine for a moment, that you are a drowsy otter, getting blissfully rocked to sleep by the gentle rise and fall of the surge, without a care in the world. You are safe because the kelp draped over your belly will anchor you and keep you from being swept away during your slumber. This is the charismatic image that comes to mind when one thinks about Monterey Bay, and what one might imagine the northern coast looking like before the otters disappeared. The dense, golden kelp forests are the foundation along the rugged Pacific Coast, providing food for the critters on the bottom, shelter for the fish swimming below the surface, and an anchor for a tired furry mammal. These beds of swaying algae are also cherished by humans, including scuba divers, artists, and beachgoing children alike. But beyond their aesthetic attributes, these bountiful forests also perform a critical ecosystem function, serving as a foundational species, a species that is abundant and can uniquely control the surrounding biodiversity.

Unfortunately, in recent years it has become no secret that the California kelp forests are in decline, with little hope for a natural rebound. It all started in 2013, when a devastating disease known as seastar wasting syndrome, wiped out many seastar populations, including the sea-urchin-devouring sunflower star (Pycnopodia helianthoides). One year later, the ocean along the Pacific Coast experienced unusually warm temperatures for a prolonged period of time, creating non-ideal conditions for bull kelp forests. In that same year, scientists detected a reduction in annual kelp forest cover up and down the California coast. This “perfect storm” was a one-two punch to bull kelp, putting it at a severe disadvantage that caused a shift from healthy forests to urchin barrens over the course of just a few years. By 2019, an estimated 95 percent of the northern kelp forests had disappeared, causing profitable commercial fisheries for red abalone (Haliotis rufescens) and red sea urchin (Strongylocentrotus franciscanus) to dramatically decline. The resulting barrens, in the absence of kelp forests and characterized by bare rocky bottoms and ravenous hordes of purple sea urchins (Strongylocentrotus purpuratus), are now common off the coast of California.

Now, for most, this drastic change in the ecosystem that seemingly happened overnight was a shock and a reason for immediate action. The kelp forests are a staple along the California coast, and without this foundational species, we know that the whole ecosystem shifts. Understandably, fishers, locals, and some scientists, quickly sprang into action, formulating ways to intervene to hopefully keep the forests alive. However, some scientists urged caution, suggesting everyone take a step back and look at the full picture. Much like a pendulum that swings back and forth, the kelp forest ecosystem has two “steady states” or systems that remain stable until a large shift occurs and swings that system to the opposite state. The kelp forest is either in a healthy kelp forest state or an urchin barren state. Throughout history, humans have documented kelp forests swinging back and forth, shifting between these two stable states. This means that the kelp forest could naturally recover from an urchin-barren state, it just needs time and the right conditions. However, much of California’s coastal economy (and many people’s livelihoods) relies on the kelp forest staying in a stable and healthy state. Because of this, state officials and scientists agreed that intervening and assisting the kelp forests in their recovery was the best plan of action.

Kelp On the boat pre dispersalResearchers prepare for a spore dispersal from the boat. Photo by Elizabeth Carpenter.However, kelp restoration is no easy task. This is especially true in northern California due to the dynamic, high-wave action coast, the presence of an insatiable grazer, and the unique life history of the bull kelp species. As an annual kelp, it completes its entire life cycle within one year. This life history aligns with seasonal variability, with growth occurring in the early spring through summer, and spore production and dispersal taking place in the fall. Much like a fern, bull kelp produces reproductive spores that are packed by the millions into specialized tissues called sori, releasing and dispersing the spores when they are mature. Bull kelp completes its life cycle when its long, flowing strands are ripped from the seafloor and deposited on the beach by large winter storms. Although this live-fast-die-young life history allows the bull kelp to persist in extreme environments, its annual life cycle poses many challenges for restoration. The most successful techniques applied to kelp in California to date have focused on species that either reproduce year-round or are in low-wave action regions.

In recent years ecologists and biologists, alongside state officials, non-profit kelp experts, and passionate commercial and recreational divers, have been working around the clock to try and restore the kelp forests, including the northern California canopy forming kelp species, bull kelp (Nereocystis lutkeana). Kelp restoration techniques that are currently being tested include urchin removals, spore bags, seeded lines, and seeded gravel. However, the hungry urchins are quick to devour any new bull kelp that starts to grow, preventing kelp forests from recovering. Divers have worked tirelessly to remove purple urchins, eliminating over 50,000 lbs from 2019 to 2021, reducing the density of urchins in hopes that the kelp would come back on its own. Spore bags (mesh bags with spore-dense material collected from a nearby healthy bull kelp bed) and seeded lines (spore-seeded rope bolted to the seafloor) have also been tested alongside urchin removals. There have also been experiments with Green Gravel, or gravel seeded with kelp spores. However, regardless of the technique, researchers have found that kelp restoration methods are generally costly and limited to restoring small regions at a time. In August 2022, The Spore Solution Team, (Elizabeth Carpenter, FISHBIO and Daniel Gossard, Monterey Bay Seaweeds), joined the battle to save the kelp forests, proposing to test a novel restoration technique that may be used as a complementary tool to bolster kelp forest recovery.


kelp pilot study with microscope slidesResearcher Dan Gossard secures the custom 3D-printed microscope slide holder to a concrete block as part of a pilot experiment to test how far the spores disperse. Photo by Elizabeth Carpenter.The Spore Solution kelp restoration project, funded by Pacific States Marine Fisheries Commission, aims to test a technique that reduces overall costs, removes the need for physical substrates for kelp spores (like mesh bags, rope, or gravel), and may restore large swaths of kelp forests in a single deployment. The approach is meant to be a spore dispersal enhancement, providing a “helping hand” to the few natural populations of bull kelp still present in northern California. The methodology is based on three simple steps: 1) collect a small amount of spore-rich material from a local bull kelp population, 2) encourage spores to release into a container of seawater, and 3) deploy the concentrated solution of spores to the restoration site. This third step is made easy by the affectionately named “Reef Duster,” a custom-fabricated system that deposits the spore solution directly to the ocean floor. Restoration areas targeted during the experiments include regions where bull kelp forests historically flourished. The Spore Solution project team conducted the first spore dispersal trial in September 2022 in Drake’s Bay, but due to a variety of issues, including the very uncharacteristically wet winter in early 2023, the spores dispersed were likely buried by sediment. In June 2023, a pilot study was conducted in Monterey Bay, to measure the applicability of the method and the distance in which the spores traveled once they were dispersed on the sea floor. Initial findings suggest that when billions of spores are dispersed directly to the substrate, spores will recruit within meters of the dispersal point. These findings give the Spore Solution Team hope that this method could be scaled up to regional restoration efforts in the future. In September 2023, the Spore Solution Team will be dispersing spores once more in Drake’s Bay, keeping their fingers crossed that 2024 doesn't bring along more uncharacteristic winter storms.

Someday we hope the sea otters once again drowsily sleeping in northern California’s kelp beds, once again lending their predatory superpowers to efforts to restore coastal ecosystems. Until then, the future will tell if this novel technique is successful on a larger scale, and how it may become a tool in the restoration toolbox used to solve the northern California kelp conundrum.

If you would like to visualize kelp canopy loss in California over time, check out The Nature Conservancy’s interactive map at kelpwatch.org.

Sea otters rafted in a California kelp bed. Photo by Joan Tisdale.

kelp Elizabeth RamsayAbout Guest Blogger Elizabeth Carpenter

Elizabeth is an aquatic biologist and communications specialist with extensive experience in a wide variety of marine and freshwater systems. She has many years of experience working as a scientific communicator and biologist in aquatic systems. She regularly writes reports, develops communication materials for multiple websites and social media platforms, and mentors science communication interns at FISHBIO. Elizabeth holds a Master of Science Degree in Marine Biology and Ecology from California State University Monterey Bay and Moss Landing Marine Laboratories, where she designed an experimental thesis testing morphological plasticity in two kelp species based on wave exposure along the Monterey Bay Peninsula.