The cove was a mass of shining fronds of bull kelp (Nereocystis luetkeana) floating languidly atop the swell. Each plant’s long, brown stalk stretched down to a sea floor teeming with myriad creatures. Amid the dim light filtering down from the surface, a leopard shark’s dappled form glided slowly, in search of prey. Small fish sheltered beneath the kelp canopy. Abalone grazed on succulent algae that clothed the rocky bottom. A black seabird dove beneath the surface, darting here and there, propelled by strong wings and feet, picking off fish, one by one. Life in the forest – this Kingdom of Kelp - was good, was balanced.
Bull kelp, known scientifically—but somewhat irreverently—as Nereocystis leutkeana, or “mermaid’s bladder,” is a world-class marine plant: it grows nearly a foot each day, up to 70 feet high, and is "anchored" to the seafloor by a root-like holdfast. Its long hollow tube, or stipe, on reaching the surface, branches into a bouquet of blades made buoyant by gas-filled bulbs. From these, the fronds fan out to absorb nutrients from the cool, rich water, and photosynthesize mightily: marine algae generates nearly 70% of our planet’s oxygen.
Bull kelp forms a tower of life, from seafloor to surface: seals, sea lions, seabirds and other marine life find the kelp’s “larder” generous, yielding up a feast rockfish, crabs, urchins, prawns, abalone, and sea stars. It provides habitat for tiny plankton and great whales. Gray whale mothers with newborn calves may hide in kelp to confuse prowling killer whales, whose echolocation is confounded by the acoustic “curtain” of hollow kelp stipes bouncing their signals back. Grays may even slurp a snack of crustaceans or fish eggs from the fronds. In these ideal conditions, marine invertebrates like abalone, sea stars, limpets, and sea urchins, were thriving. And we land creatures benefitted from sports and commercial fisheries, and income from recreational use of this spectacularly scenic area.
But, despite its majesty and magnificence, kelp is also vulnerable: as an “annual” plant that lives just one or two years, its propagation can be suppressed, perhaps indefinitely, by abrupt and persistent disruptions within the ecosystem. And it was.
Along the Sonoma and Mendocino county coasts, the once-luxuriant kelp kingdom came under siege, in a virtual ecosystem collapse. In 2011, disaster struck when a toxic algae “red tide” occurred, killing a variety of sea life. Sea stars, which had kept the urchin population in check, died en masse from a wasting disease. Urchin numbers skyrocketed, devouring everything available. And from 2014 through 2015, an oceanographic triple-whammy hit: in 2014 a warm water cell called “The Blob” hunkered down off Northern California, suppressing productive, cold-water upwelling. It combined with a strong El Niño warm water phenomenon, and gradual ocean warming. The result was a deadly cascade of effects. Starvation ensued in parts of the food web, the exception being – at first -- the purple sea urchin. A versatile opportunist, this species denuded its surroundings. Grazing fiercely on the kelp, especially the tender new plants, mowing down both forest and undergrowth, creating “urchin barrens” where virtually nothing else lived. And when kelp density is low, their spores may not settle properly and mature; new kelp plants simply fail to materialize. By devouring the kelp, the urchins have literally eaten themselves out of house and home.
What can slow or stop this urchin devastation? Disease, storms, an increase in predators. Eliminating fishing pressure can help the abalone recover. Sea star numbers seem to be rebounding. What about kelp recovery? Cool water, at 63 Deg. F. or lower, is essential; successive La Niña coldwater phenomena could help. But that’s beyond resource agencies’ abilities to arrange.
The California Department of Fish and Wildlife has taken the lead on restoring several components of this compromised ecosystem, through closures, and extensive field and laboratory studies to tease out the intricacies of food web dynamics that might suggest solutions. In January 2018, NOAA’s Greater Farallones National Marine Sanctuary Advisory Council voted to form a Working Group to address the kelp forest crisis in Mendonoma. We will engage in strategic collaborations, but it will be a formidable task.
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For more information:
• https://farallones.noaa.gov/eco/
•https://cdfwmarine.wordpress.com/2016/03/30/perfect-storm-decimates-kelp/
