Lending a Kelping Hand in Greater Farallones National Marine Sanctuary

By Marissa Garcia


January 2020

Scientists dove off the R/V Fulmar into the sea off the coast of Northern California, in Greater Farallones National Marine Sanctuary. Propelling themselves downward with their flippers, they saw bright patches of purple sea urchins lining the ocean floor, but the familiar kelp forests were gone. Scientists call these environments urchin barrens, a shallow area of the ocean where urchins have overgrazed kelp forests. Here, divers conduct annual underwater surveys, recording data on the population dynamics of algae, invertebrates, and fishes.

Tracking the health of marine ecosystems like kelp forests requires scientific monitoring, which depicts how these ecosystems have changed over time. In recent years, NOAA’s Office of National Marine Sanctuaries, the Greater Farallones Association, and Greater Farallones National Marine Sanctuary have collaborated with the California Department of Fish and Wildlife, Ocean Protection Council, and The Nature Conservancy to document the transition from kelp-dominated to urchin-dominated ecosystems along the West Coast, a shift accompanied by a steep decline in biodiversity. These monitoring efforts are centered in Monterey Bay and Greater Farallones national marine sanctuaries.

a diver swims through kelp
Dr. Steve Lonhart, a NOAA diver, investigates giant kelp in Monterey Bay National Marine Sanctuary. Photo: Paul Chetirkin/NOAA

Kelp forests harbor incredible biodiversity, bolstering populations important for local fisheries. They serve as both a food source and shelter for several marine species. “The kelp forests in Northern California hold fish, abalone, sea urchins…all kinds of beautiful organisms that people like to fish for, and dive and kayak around,” says Dr. Laura Rogers-Bennett, a senior scientist for the California Department of Fish and Wildlife who is actively involved in the long-term monitoring effort.

In an effort to bring back the kelp forests’ biodiversity as swiftly as possible, the Greater Farallones Association, a non-profit organization that supports habitat restoration within Greater Farallones National Marine Sanctuary, used recommendations from the Greater Farallones Sanctuary Advisory Council to develop the Sonoma-Mendocino Bull Kelp Recovery Plan, which was finalized after an extensive literature review and geographic information system (GIS) analysis. The recovery plan contains strategies for kelp forest recovery, and involves restoration site selection, monitoring, research, and community engagement.

Biodiversity in Changing Seas

Purple sea urchins can overgraze kelp forests, resulting in an urchin barren. Photo: Paul Chetirkin/NOAA

Kelp forests arise in cool, nutrient-rich waters, which are normal conditions in Monterey Bay and Greater Farallones national marine sanctuaries due to upwelling from the California Current. These forests prosper in the nearshore rocky habitat, where kelp can grow tall, attached to the seafloor and rising upward to the ocean’s surface, bathing in the sunlight that fuels photosynthesis. The heavy foliage offers shelter for many creatures, including fish that use these kelp forests as nursery habitats.

But sea urchin overgrazing can devastate kelp forests. Sea urchins consume kelp holdfasts and algae found on the bottom, and they can outcompete other invertebrates such as abalone. If there are too many sea urchins, the kelp forest can vanish. This has occurred all along the West Coast, and in some areas, 95% of the kelp has disappeared.

Between 2013 and 2015, a mysterious sea star wasting disease killed populations of approximately 20 different sea star species, including those that are known to prey on sea urchins. The sunflower star is a known keystone species that consumed large quantities of the urchins. Some researchers believe the decline of this species contributed to the proliferation of purple sea urchins in subsequent years.

Other predatory species such as fish and lobsters in central and southern California also impact the urchin populations, creating a complexity of ecosystem dynamics and responses to ecological and climate stressors. The mystery continues, and scientists are still trying to understand why the purple urchin population swelled. Some believe that marine heat waves may have facilitated high sea urchin recruitment.

Shifting Ecosystems

Sea urchins edge in on bull kelp growing in Monterey Bay National Marine Sanctuary. Photo: Dr. Steve Lonhart/NOAA

“When you switch over to an urchin-dominated system, it dramatically changes the entire community,” says Dr. Steve Lonhart, a senior scientist for Monterey Bay National Marine Sanctuary and the Sanctuary Integrated Monitoring Network. With the disappearance of so much critical shelter, much of the biodiversity distinctive to the kelp forests is displaced or lost completely. Many fish and invertebrate species native to kelp forests that are important for supporting local fisheries and food security disappear with the emergence of urchin barrens.

Lonhart further clarifies that kelp-dominated and urchin-dominated habitats are what scientists call “alternative stable states,” which means that once either community becomes established, it tends to stay that way until something changes significantly. However, with climate change it is predicted that marine heat waves will increase in frequency and duration. Because temperate kelp forests do poorly when the water is abnormally warm, the predicted heat waves will likely continue to cause long-term ecological consequences and subsequent economic impacts resulting from kelp forest loss.

Sea otters commonly prey on sea urchins. However, they’re not likely to stave off the high urchin population of the barren flats. Sea otters only eat urchins with healthy gonadal content; these are limited in the barrens, where fewer food resources are available, and urchin gonads shrink in size to survive through starvation. This makes the urchins unappealing prey to sea otters.

Because sea otters may not put predatory pressure on the urchin barrens, the transition to a kelp-dominated ecosystem may not happen until a large disturbance happens. If a disease were to break out, for example, it would likely spread quickly in the dense population of urchins living in the barrens, which could severely reduce the population. The timeline for this, however, is uncertain and urchin-dominated systems have been documented to last for decades. Without active management, degraded kelp forest ecosystems can and will result in dramatic ecological and economic consequences.

Community Kelp Restoration

A diver records data in an urchin barren. Photo: Dr. Cynthia Catton/CDFW

Greater Farallones National Marine Sanctuary and the Greater Farallones Association are currently implementing strategies for kelp forest restoration, monitoring, research, and community engagement as outlined in the Sonoma-Mendocino Bull Kelp Recovery Plan. In partnership with The Nature Conservancy, the sanctuary and association are analyzing the feasibility of flying Unmanned Aerial Vehicles (UAVs) over these coastal regions to map kelp forest canopy dynamics. Through the Kelp Ecosystem and Landscape Partnership for Research on Resilience (KELPRR), the association and sanctuary are collaborating with over 30 partners to organize outreach events. Partners include researchers, nonprofits, for-profits, fishermen and women, and members of the community – all coming together to address the challenge of kelp loss.

The Waterman’s Alliance, an organization that represents over 1,000 divers in spearfishing clubs throughout California, coordinated initial efforts to remove urchins at key sites in 2018. According to Rietta Hohman, the kelp recovery project manager and education specialist for the Greater Farallones Association, the most important element for large-scale kelp restoration is engaging commercial urchin divers to conduct urchin harvesting efforts at the sites identified in the recovery plan. Urchin divers have the experience, expertise, and equipment to conduct targeted urchin harvesting. Reducing the urchin densities at key areas will help remove intense grazing pressure, preserve the nearshore bull kelp spore bank, and ultimately help catalyze the process of kelp recovery.

Impacts of Kelp Loss

In the barrens, urchins live together in extremely high densities. Photo: Katie Sowul/CDFW

The loss of bull kelp forests on the northern California coastline has led to the collapse of the region’s commercial red sea urchin fishery, which has a $3 million annual average value, and the complete closure of the recreational red abalone fishery. As a result, local businesses are now suffering. The only dive shop on the north coast, Sub-Surface Progression, officially closed its doors in December 2019. Kelp forests are valued for many other reasons, such as supporting economically important commercial and recreational fisheries, non-consumptive diving, snorkeling, and wildlife viewing. Additional concerns over climate change and more frequent marine heat waves add to the urgency to take action now.

How You Can Get Involved

Kelp forests provide dense habitats for many marine species. Photo: Paul Chetirkin/NOAA

Residents near Monterey Bay and Greater Farallones national marine sanctuaries can get involved in bringing back kelp forests. You can partake in citizen science efforts, including conducting surveys in urchin-dominated reefs with Reef Check California and dockside urchin sampling with The Noyo Center for Marine Science. While diving, you can help determine how dense urchin populations are, and where kelp is beginning to grow again. Greater Farallones and The Nature Conservancy are also investigating opportunities to expand citizen science opportunities for youth and the public for intertidal monitoring and kelp canopy mapping with UAVs.

Education about kelp forest ecology and the resulting effects on fisheries may also be coming to your community soon. Greater Farallones National Marine Sanctuary is striving to launch a kelp-focused “Fisherman in the Classroom” program, which would bring commercial and recreational fishermen to students on the north coast of California as guest lecturers.

Restoring kelp forests is also of interest to the coastal communities living along Northern California. Lonhart reflects upon the impact of urchin barrens: “You lose the kelp and a lot of the species that are associated with it, and it changes the way you see the coastline, the way you experience it, the way you dive in it, snorkel in it, sail through it.”

The collective effort of national marine sanctuaries and their partners along the Northern California coast could convert desolate urchin barrens to the vibrant kelp forests these communities depend on.

Marissa Garcia is a student at Harvard College and a Virtual Student Federal Service intern for NOAA’s Office of National Marine Sanctuaries.