Underwater Barrens

Monitoring the fate of Southern Californian kelp requires a long view.

Kelp forests in Southern California

KATIE DAVIS/UCSB

Kicking towards the ocean’s floor, kelp divers see the world turn a distinct shade of blue-green. Rising air bubbles and the click-clicks of krill drown out familiar land-dwellers’ sounds. Like a strange dreamland, where the scale of an organism readily shifts, giant kelp stalks start to loom like majestic redwood trees, stretching from the depths to the sky. At the surface, the kelp fans out to create a canopy, replete with an understory refuge for fish to escape the predatory eyes of ospreys and eagles. Gliding through this underwater forest can feel like flying.

Sea urchins are choking out kelp forests in Southern California.

KATIE DAVIS/UCSB
Off the coast of Southern California, five quiet and unassuming islands make up Channel Islands National Park, a 250,000-acre haven that works in association with the Channel Islands National Marine Sanctuary. Santa Rosa Island, the second largest of the islands, sits like a diamond, with one point facing due south. On the backside, a comfortable anchorage called Johnson’s Lee offers respite in foul weather to boats, but not to kelp forests, which are being devoured by sea urchins. Johnson’s Lee sits just outside of the South Point Marine Protected Area, and the dividing line can be clearly seen by a dramatic difference in biological diversity of fish, algae, and invertebrates.

Two years ago, Johnson’s Lee was a vibrant kelp forest, thriving with abalone and various species of fish. Now, urchin barrens dominate. Urchins have effectively clearcut the kelp forests and changed the dynamics of the ecosystem. As Katie Davis, a research associate at the University of California, Santa Barbara, said, “Everything’s so out of whack in the Channel right now . . . everything is in flux. Johnson’s Lee urchin barren is one of the gnarliest things I’ve seen. There’s a front of urchins moving in.”

Davis manages the UCSB chapter of a long-term kelp forest monitoring program, called Partnership for Interdisciplinary Studies of Our Coastal Oceans (PISCO). Similar to how physicians use pulse, blood pressure, and temperature to gauge bodily well-being, these long-term programs provide a storehouse of data and information that can be used to measure the health of an ecosystem.

Johnson’s Lee, an anchorage off the coast of Santa Rosa Island, has turned from a diverse kelp forest into an urchin barren.

KATIE DAVIS/UCSB
Last year was one of the most biologically disturbing years on record, likely due in part to an unprecedented warm water event, nicknamed the “Blob,” sitting off Southern California. Such an event raises the question of whether Marine Protected Areas are doing what they were designed to do: increase biological diversity and abundance, and develop resilience to disturbances such as El Niño and overfishing. The variables that contribute to the issue of kelp deforestation are like a spider web of linkages. “It’s incredibly complex,” says David Kushner, the National Park Service Regional Dive Officer and overseer of the Kelp Forest Monitoring (KFM) Program—established in 1982, it’s one of the longest running marine monitoring programs in the country.

Kushner, who has been diving for the Park Service in the Channel Islands since 1990, stresses the importance of long term data for understanding natural cycles. Without historical data, one might jump to the conclusion that this event is unprecedented. In fact, “It’s turned into an urchin barren three times, always post El Niño,” says Kushner.

Overcrowded urchin populations often resort to cannibalism.

KATIE DAVIS/UCSB
This time might be an exception, though. Sunflower stars (Pycnopodia helianthoides), a keystone predator for urchins, typically keep urchin populations in check. However, marine biologists speculate that due to a series of warm water anomalies, a sea star “wasting” disease, which is precipitated by infection with a densovirus, has decimated populations. “We haven’t recorded a sunflower star in years at Johnson’s Lee,” says Davis. 

Another keystone predator that influences the health of kelp forest ecosystems is the sea otter. Urchins have been the scourge of kelp forests since sea otters were hunted to extinction in southern California for their valuable fur pelts in the eighteenth and nineteenth centuries. Sea otters can eat up to 25 percent of their body weight every day, with one of their favorite snacks being sea urchins. Without the otters to keep urchin populations down, the kelp forests were overrun.

In the northern waters of the coastal U.S., sea otters fare better. In the mid-1990s, a population of about one hundred sea otters moved into the Juan de Fuca Strait, where they had been previously eradicated. (Prior to that, sea otters were manually introduced with moderate success as well.) Bob Sizemore, a research scientist for Washington State Fish and Wildlife, witnessed the ecosystem turn from urchin bar-ren to kelp forest in the span of months. “To see that shift almost overnight was just amazing.”

Sea otters have made a come-back as far south as Monterey, California. In Southern California, where sea otters have yet to return, humans fill the gap. Urchins are a delicacy in many Asian countries and the West Coast urchin fishery is thriving, with urchin hunters walking along the ocean floor, weighted down with lead, plucking urchins off the reef, and piling them into oversized mesh bags. Logically, one might conclude an urchin barren should be a boon for urchin fishermen. However, due to over-grazing and a dearth of food, urchins living in barrens start to cannibalize one another. Moreover, their gonads—the edible portion of the creature—do not develop fully and cannot be consumed.

Warm water events seem to correlate with higher disease and death rates among urchins, too. According to Joshua Sprague, a KFM diver, “urchins are at, or near, all time low densities at [the southern] island sites, likely due to a warm-water related disease.” Although this might temporarily bode well for kelp forests and their dependent species, some biologists predict that an increase in warm water events will trigger massive larval dispersal in sea urchins, causing more overcrowding and prompting a population collapse among sea urchins as well.

Given the complexity of ecosystem dynamics, the importance of long-term monitoring becomes ever clearer. “It’s all about cycles,” Kushner says, as he emphasizes that taking the long view is “one of the best ways to begin to understand how climate change works.” Unfortunately, ongoing monitoring programs are being cut. In 2012, PISCO’s kelp-forest program had to drop half of its dive team due to an inability to secure funding; the changing political environment only spells more uncertainty. Yet the more we learn about the dynamics of Pacific Ocean life, the more we can appropriately adapt to a changing environment.

--DS

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Monitoring the fate of Southern Californian kelp requires a long view.