Coast & Ocean Vol. 21, Nos. 1&2: Bringing Kelp Forests Back

Macrocystis pyrifera: the syllables roll off the tongue—much more elegantly than the thin words “giant kelp.” Both names, though, apply to the same amazing plant, one that we are fortunate to have growing along the California shore. Vast forests of it provide shelter and sustenance to an amazing abundance and diversity of animal life, from lumbering black sea bass, which reach weights of over 500 pounds, to gliding bat rays, to feather-duster worms, jeweled top snails, brittle stars, and myriad other members of the invertebrate orders, right down to the lowliest encrusting sponge.

The animals this plant houses (a single holdfast may provide shelter to more than 150 species) are fascinating enough, but Macrocystis pyrifera is itself just as fascinating—if not more so. For one thing, it has evolved a two-stage life cycle, alternating between sexual reproduction (when the plant, in its incarnation as a tiny sperm- or egg-releasing gametophyte, is best seen under a microscope) and asexual reproduction (the ropy golden-brown plant we think of when we imagine kelp is in fact the sporophyte, or spore-producing phase). From microscopic teeniness, giant kelp can grow more than a foot a day, to lengths of more than 200 feet. “Forests” form over hard substrate (usually rocks) in ocean depths to 120 feet, but typically between 20 and 70 feet, and may vary in extent from several hundred feet to a mile wide and several miles long.

A land-bound eye might identify a kelp forest from its gentle riffle on the surface of the sea; the canopy of topmost fronds stretch out over the water, rolling with the swell and flapping lightly in the breeze. When seen from below, however, the kelp forest is majestic and imposing—another world entirely. It is often likened to a redwood forest, and in its verticality there is a certain similarity. On a sunny day in a calm ocean the kelp forest becomes an ethereal place in which long beams of light dance among undulating algal stipes and fronds. Rockfish hover big-eyed and Zen-like, little orange señoritas flit about like birds, and spotted harbor seals swoop in for a close look at you, an awkward, bubbling, wet-suited creature clearly not of their realm.

It is also an environment at the mercy of tides, currents, and swells—oceanographic and meteorological forces that can be far from benign. When wintertime waves come crashing onto California’s shores driven by low-pressure systems far to the south or north, the kelp forest becomes a place, if not quite of lashing fury (water being thicker than hurricane-driven air), at least of intense agitation. These natural forces can rip up weak holdfasts in a kelp forest and then fling the 100-plus-foot plants ashore among pounding waves.

Death, however, feeds life, as shorebirds come to pick at the bounty of tiny animals tucked within the holdfasts’ snaking haptera, which a short time before glued plant to rock. Soon, too, kelp-fly and beach-hopper eggs laid in the decomposing vegetal mounds begin to hatch by the thousands, becoming more food for more birds. Death becomes life: that is the way of things, and when caused by natural forces we welcome it. But what about when humans upset the balance? Do we just let things be?

Some marine biologists studying the Southern California Bight—where human disturbances along the heavily settled coast have been especially high—say the answer is no. For the past 15 years, they have been exploring means to mitigate past wrongs. One potent response is reforestation (planting kelp beds where kelp used to be), something that four Southern California “Keeper” organizations have been hard at work on since the mid-1990s.

Tom Ford, biologist with Santa Monica BayKeeper, explained that in the Los Angeles area a good 60 to 70 percent of kelp beds that once thrived over the Palos Verdes Shelf and along the Malibu coast west to Point Dume have vanished over the past 75 years. The reasons are complex, but major culprits have been wastewater discharge and erosion from hillside development that puts enough dirt into the ocean to bury the substrate—and tiny new kelp plants. Another cause is ecosystem imbalance. The extirpation of the southern sea otter during the late 1800s and, more recently, heavy fishing of spiny lobster and sheephead—all major predators on sea urchins—have let urchin populations blossom. These spiky echinoderms love kelp, although in a pinch they feed quite happily on sewage and, if necessary, can wait months to get a balanced meal. Once they have created “urchin barrens” by scouring rocky reefs clean of kelp, they never go away long enough to allow new plants to become reestablished.

Because the change is hidden from view, Ford said, “The average beachgoer goes down, looks out over the water, and everything looks fine. If we went out and chopped down 70 percent of the chaparral community in Malibu, people would lose their minds.”

Students Give Nature a Hand

In the early 1990s, Santa Monica BayKeeper decided to take action. With funding from the National Oceanic and Atmospheric Association, Coastal Conservancy, and Santa Monica Bay Restoration Project, BayKeeper began by monitoring 11 sites: three on the Palos Verdes Peninsula and eight along Malibu. The goal was to determine where healthy kelp was growing, what was living among the plants’ fronds, stipes, and holdfasts, and whether the forests were expanding. These surveys contributed to the identification in 1996 of three prime locales for attempting kelp reforestation—one north of Rocky Point, Palos Verdes, and two near Malibu’s Escondido Beach and Paradise Cove.

To get going, BayKeeper biologists needed large numbers of young kelp plants, and they saw an immediate opportunity: Get schoolchildren involved. While working as kelp “farmers,” students would learn about kelp forest ecology, plant biology, and scientific methods, and would gain a personal stake in their local ecosystem.

For three years, sixth-graders at Lincoln Middle School in Santa Monica rolled up their sleeves and became part-time biologists. Each fall, BayKeeper scientists went to the school and presented basic information on kelp and the interdependency of kelp forest animals and plants. Then students designed and carried out various experiments to understand kelp herbivores better. How much do urchins really eat? Which kelps do they prefer? By observing sea urchins in the classroom, they arrived at some hard answers, which they could pass on to BayKeeper biologists. Urchins’ love of Macrocystis pyrifera proved to be deep and abiding, their appetite prodigious—no big surprise perhaps, but for the students to see this themselves was an invaluable experience, Ken Vanderveen, a Lincoln teacher, said.

Come January, actual kelp cultivation joined the curriculum. First, volunteer divers in the bay collected sporophylls (specialized blades at the base of the giant kelp plant). As Vanderveen explained, “Students then photo-shocked the sporophylls, tricking them into releasing their spores.” This was done by subjecting the reproductive blades to controlled changes in temperature and light. The students then (after counting the swimming spores under the microscope to ensure proper concentrations) inoculated 10 gallons of seawater in specially designed “ecocart” aquariums that allowed water at a regulated temperature to circulate over 100 small unglazed tiles onto which kelp spores could settle. Each day for seven weeks, students checked water temperature and salinity and, as needed, cleaned out brown diatoms, which can smother the young kelp. After two months, if all went well, they would see thousands of tiny kelp plants appearing as “brown peach fuzz” on the tiles. At that point, the tiles would be transferred to a lab on Terminal Island in Los Angeles Harbor, to be grown into inch-long plants and readied for transfer to the sea.

In practice, all did not always go well, so now the kelp raising is restricted to the more controlled environment of the Terminal Island lab. The students, nonetheless, learned some key lessons about science—including the possibility of failure and the importance of being ready to “try, try again.”

The overall experiment has proven very successful ever since it left the lab and entered the waters of Santa Monica Bay beginning in 2000. Inflows of cool, nutrient-rich water have contributed to this success story. “When we started, the area was completely wiped out,” he noted. “But conditions started to change just as we got going, and the whole area exploded.”

Baykeeper personnel and volunteers transport seeded tiles (or sometimes pieces of rope) to reefs 25 to 45 feet deep and attach them with rubber bands. Sprouts that “take” grow about three feet in a few months, at which point the tiles and rubber bands are removed. The BayKeeper biologists have also tried transplanting established kelp plants, but this technique has met with little success. Another technique is to fill mesh bags with sporophylls collected from neighboring beds and float them a few feet above the surface of the reef; spores then settle out naturally.

First, however, any urchins in the vicinity must be relocated. The Malibu reef is fairly near an area that still hosts a thriving kelp forest, where natural “recruitment” has occurred during the past few years, perhaps because of improved water conditions. “So people are looking at this and saying, ‘That’s all right, Tom; we don’t need you. It’ll fix itself,’” Ford said. “But I say, hey, we’ve still got 70 urchins in a square meter. I don’t care if everything else is ideal, there’s no way the kelp is going to be able to expand back into its former range if we don’t restore the balance of that ecosystem. Either I’m going to do it, or you set up a marine protected area and you let the lobsters and the fish come back and do their thing, and regulate that urchin population. That’s what I would prefer, because I don’t pretend to be able to do what Mother Nature does.”

In the meantime, however, there’s nothing wrong with giving mother a hand. The reforestation project will restore many thousands of square meters of kelp beds, and once the planting is complete, monitoring will continue for up to seven years. Biologists will compare restored areas to nearby kelp beds that remain intact, and to now-destroyed kelp beds. Relative change in species abundance and diversity will be tracked in each environment, and those data compared with similar monitoring projects in Santa Barbara, San Diego, and Orange Counties.

Kelp forests are nurseries for larvae and juvenile fish, and to restore some of this habitat will benefit sport and commercial fishers. The tourist-trade benefits of enhancing this scuba-diving paradise cannot be discounted either. But just in terms of natural habitat—never mind its “uses” for humankind—restoring the kelp forests seems a worthwhile task. “They protect our coastlines, they dampen wave energy, they interrupt longshore currents—the current that goes ripping along our coast and keeps scything sand away,” said Tom Ford. They are an all-important part of our coastal ecosystem.

Return to the picture I painted above, of long shafts of light and gently moving creatures. And now consider what Charles Darwin wrote in 1860, on his Beagle voyage in South Pacific waters: “There is one marine production, which from its importance is worthy of a particular history. It is the kelp, Macrocystis pyrifera. This plant grows on every rock, from low-water mark to a great depth, both on the outer coast and within the channels. . . . The number of living creatures of all Orders, whose existence intimately depends on the kelp, is wonderful. A great volume might be written, describing the inhabitants of one of these beds of seaweed. . . . I can only compare these great aquatic forests of the southern hemisphere, with the terrestrial ones in the intertropical regions. Yet if in any country a forest was destroyed, I do not believe nearly so many species of animals would perish as would here, from the destruction of the kelp.”

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