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Kelp's enemies: sea urchins, kelp curlers, el nino, and sewage

In the forests of the sea

Scuba gear necessary for the study of underwater biology was invented just forty-five years ago.
  • Scuba gear necessary for the study of underwater biology was invented just forty-five years ago.

One of the eeriest forests in the world is located just a mile or two from the center of San Diego. Very few people enter it, though there is one safe, and convenient way to glimpse what it’s like. If you go to the Natural History Museum and descend to the dimly lit basement, you will find an exhibit that tries to depict a very small section of the wilds of giant kelp.

The giant kelp plant can grow a new canopy two or three times a year.

The giant kelp plant can grow a new canopy two or three times a year.

Life-size models of this king of the undersea plant world, which grows so luxuriantly off our beaches, snake upward though pools of blue light; here and there, startlingly realistic models of various fish are suspended. Beside the models, clearly written notes convey facts about the forest. All are well executed but at the same time terribly misleading.

Harvesting ship Kelsol.  Kelco for the most part decides when the kelp should be harvested.

Harvesting ship Kelsol. Kelco for the most part decides when the kelp should be harvested.

The kelp forest in the museum basement is frozen, silent, motionless, whereas the real kelp forest moves ceaselessly — churning, twisting, swaying, changing at an astonishing rate. The neatly printed notes in the museum give the impression that the local kelp beds are firmly within man's understanding and control. But the San Diego scientists who work on researching the kelp beds laugh and shake their heads at that notion. They know better.

Kelco biologists Craig Barilotti, Dale Glantz, Ron McPeak

Kelco biologists Craig Barilotti, Dale Glantz, Ron McPeak

Craig Barilotti likes to say that human knowledge of marine plants, compared to that of terrestrial plants, is about 3000 years behind. “We’ve been growing terrestrial plants for thousands of years,” he says. In contrast, scuba gear so necessary for the study of underwater biology was invented just forty-five years ago, and the vast majority of the research on the giant kelp, Macrocystis pyrifera, began more recently than that.

Scripps scientists Paul Parnell, Claridy Lennert, Paul Dayton, Mia Tegner

Scripps scientists Paul Parnell, Claridy Lennert, Paul Dayton, Mia Tegner

Barilotti is a marine biologist working for Kelco, the San Diego-based company that, with 500 local employees and 1400 employees worldwide, is the principal harvester of giant kelp in the world. A native of Santa Monica, Barilotti began scuba diving more than thirty years ago and occasionally swam in the waters off the Palos Verdes Peninsula, the headland that delineates the southern edge of Santa Monica Bay. It was an area then experiencing an “eco-catastrophe,” according to Barilotti.

Throughout 1983 and 1984 “the kelp curlers would eat off all the blades, so you would see stipes [stalks] with just the floats. Whole areas at the south end of the Point Loma forest were completely denuded.”

Throughout 1983 and 1984 “the kelp curlers would eat off all the blades, so you would see stipes [stalks] with just the floats. Whole areas at the south end of the Point Loma forest were completely denuded.”

“At that time, there were just massive quantities of industrial wastes going out there,” including products of the Montrose Chemical Company, the last manufacturer of DDT in the United States. With sewage from Los Angeles County discharging directly into it, the ocean off the Palos Verdes Peninsula “was probably the most polluted marine environment in the world,” Barilotti says. Diving there, he says, it didn’t take much imagination to realize something was drastically awry. “At least ten miles of the bottom were just denuded of everything.” Concern over what was happening led him to pursue a doctorate in marine biology. He taught at San Diego State University for several years, then eight years ago went to work directing Kelco’s scientific research on the kelp “forests.”

Although marine biologists both inside and out of Kelco use the term “forests,” Barilotti expresses some discomfort over it. He acknowledges that stands of kelp and terrestrial forests do share certain important characteristics. Both produce dense canopies that shade the plants below. Both serve as home to plant-eating animals that graze upon the forest products.

But Barilotti likes to point out the inherent differences between the forests of the land and those of the sea. Most dramatic is the rate at which they change and grow. A tree can live for hundreds of years, whereas one of the giant kelp plants off the coast of San Diego has a typical life span of about five years. It can grow, however, at a rate of up to two feet per day under optimum conditions. “A terrestrial forest takes roughly a hundred years to produce,” Barilotti says. Compare that to a stand of the giant kelp plant, which can grow a new canopy two or three times a year. Everything else in the surrounding underwater ecological system is adapted to the giant kelp’s fast-growing, heavy-shedding lifestyle. Although the marine giants constantly lose material in the form of drift seaweed, Barilotti says, “When you dive in a kelp bed, it sort of looks like the park clean-up crew has just been there. You don’t see drift kelp all over unless there’s just been a big storm.” A host of creatures is waiting below to eat the falling drift.

Looking at kelp forests versus terrestrial forests more broadly, Barilotii notes that the productivity of land-based plants is almost directly related to the availability of water. Marine plants, on the other hand, obviously have plenty of water. Their productivity instead seems to depend most upon the availability of nutrients — the nitrates and phosphates the plants convert into new plant material. In kelp beds, nutrients are constantly brought in from deeper ocean waters through current flows and upwelling. “Nutrients in a terrestrial forest are recycled and regenerated within the forest, and if you log it extensively, eventually you take away all the nutrients and you have to add nutrients to it. In contrast, we [at Kelco] can keep taking kelp from the kelp forest, and it doesn’t affect the supply. In other words, they sort of normally harvest themselves. The only thing we change is that we harvest them all at one time.” (Although the state of California owns the kelp beds, it leases some of them to Kelco, and Kelco for the most part decides when the kelp should be harvested.)

Barilotti and other Kelco scientists are quick to add that the kelp company’s three harvesting ships cut only the top few feet off each plant. Removing only the surface canopy does subtly change the way the plant grows, and other scientists who don’t work for Kelco might argue that the effects of this aren’t fully enough understood to say that no harm is done. Yet no one has yet demonstrated any such harm, and the question was one of the earliest questions raised about giant kelp; in 1923 a research report was published that explained in broad terms how the plant grows.

Anchored to the ocean floor by a tangled mass of tissue called a "holdfast,” the giant kelp sends up fronds bearing both blades and little buoyant “floats” that lift the plant skyward. By the time they reach the surface, giant kelp fronds are usually thirty to sixty feet long. The fronds keep growing at the surface, but another change occurs — they start losing blades near their base on the ocean bottom, and they continue losing them. By the time a giant kelp plant is seventy-five feet long, it normally has lost many of its underwater blades, and soon the surface tissues begin to senesce, changing color and no longer adding new blades. Left alone, these heavy strands of aging kelp will soon break off and float away. Harvesting the plant within a few feet of the surface mimics the natural process, that study in 1923 concluded. Other subsequent studies have concurred.

In general, giant kelp likes to grow in thirty to sixty feet of water with a rocky bottom. Besides the Point Loma bed, other kelp forests dot the coast of San Diego County, their precise locations changing from year to year.

Several usually can be found in the North County, and a big one lies off La Jolla; this year it begins at a point off the Children's Pool and runs south all the way into Pacific Beach. Another kelp bed grows off Imperial Beach. A 1911 federal government survey noted it, though the surveyors described the growth as thin then, and thin it has remained throughout most of the years since. This year, however, the Imperial Beach bed grew enough giant kelp so that Kelco was able to harvest it for the first time in the company’s fifty-seven-year history. A few hundred acres in size, it seems to be increasing, according to Kelco. No one knows why.

Although it’s not surprising that the early systematic studies of giant kelp should relate to man’s exploitation of the plants, the first published insights into giant kelp ecology simply reflect a tone of awestruck appreciation. During his 1834 voyage to Chile on the HMS Beagle, Charles Darwin pored over specimens of the enormous plants and noted, “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.” It was Darwin who first compared "these great aquatic forests” with the terrestrial ones in the intertropical regions. Yet he added, “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.”

Notwithstanding the great biologist’s enthusiastic comments, American interest in its giant kelp didn’t develop for several decades more and then was spurred by the unromantic needs of the fertilizer industry. In the late 1800s and early 1900s, American farmers had come to rely heavily on a mineral called potash for use as a fertilizer, and most of the supply came from mines in Germany. Concerned about over-dependence on the Kaiser, the U.S. Congress commissioned studies conducted from 1911 through 1913 to map California coastal kelp beds, since kelp was another source of potash. Those surveys revealed Macrocystis pyrifera to be flourishing from central Baja up to Santa Cruz; another species of the giant kelp continued up to Alaska. (These are the only giant kelps found along American shores, though Macrocystis also grows along the east and west coasts of South America, off South Africa, Tasmania, south Australia, New Zealand, and the sub-antarctic islands.) Before the government survey was even concluded, commercial harvesting had begun, and the pace grew ever more frantic as potash prices skyrocketed in the advent of World War I, particularly since potash was also a key ingredient in military explosives. According to one Kelco history of this period, harvesting companies sprouted up from San Diego to Santa Barbara, and in 1916, the Hercules Powder Company, built near San Diego, was reportedly employing up to 1500 people and handling as much as 1800 metric tons of kelp daily.

Welcome as the 1918 armistice was to most people, it spelled disaster for the Southern California kelp processors. With the government canceling explosives contracts, commercial harvesting all but ceased until the late 1920s, when a few companies began harvesting Macrocystis to be processed into meal used as an ingredient in livestock feed. One such company was Kelco of California.

Kelco manufactured the kelp meal for a while but then took an interest in a discovery made by a British pharmacist back in 1883. From the walls of kelp cells, he had extracted a substance called algin, a natural compound with the ability to change the flow properties of fluids. Soon after its founding in 1929, Kelco began extracting algin, which was used at First to control the viscosity in a gasket compound for sealing tin cans. Over the years, the local enterprise developed a myriad of other applications for the algin, and today Kelco manufactures some seventy different algin products used to do everything from prevent ice crystal 1? formations in milkshakes to help I antacid tablets disintegrate.

It was Kelco, therefore, which was paying the most attention to San Diego’s giant kelp forests throughout the 1930s and 1940s, and the bulk of the company’s research efforts were directed toward how the kelp might be used, rather than at what was going on within the shadowy, complex world over which the giant kelp lorded. By the mid-1950s, however, two developments combined to begin changing that. One was the growing use and acceptance of scuba gear, which at last enabled marine biologists to get a good, sustained look below the surface of the water. The other was growing evidence that parts of Southern California’s kelp beds were in trouble.

That evidence showed up first and most dramatically off Los Angeles, in the Palos Verdes kelp beds where Craig Barilotti began his diving career. But even in the mid-Fifties, the huge kelp bed off Point Loma had also begun to thin out somewhat, particularly in the south end of the bed, right off the Point Loma lighthouse. Today many scientists believe that one major cause of the deterioration in both the Los Angeles and San Diego kelp beds was sewage. (San Diegans at that time released their sewage at a shallow depth in the bay, from which point the sewage flowed out and turned north — right into the Point Loma kelp bed.) But then, as now, the role of the sewage was hard to sort out from two other blows inflicted on the forest by completely natural processes.

One was the el nino oceanic condition that began warming the waters off the coast here in 1957. That year Kelco harvested only forty-eight percent of the kelp from the Point Loma bed that it had harvested in 1952 (a good year), and the next year, the yield dropped to twenty-one percent. In 1959, the canopy floating on the surface of the waters off Point Loma had shrunk to no more than 150 acres, just one percent of what it had been seven years earlier. By then, Kelco had begun harvesting giant kelp elsewhere in California, and el nino forced the company to expand its horizons even more.

Furthermore, not long after the canopy disappeared, the scientists and Kelco researchers who dove beneath the waters in Point Loma increasingly saw another astonishing (and to Kelco, chilling) sight. Three kinds of sea urchins normally make their homes in the kelp beds. Along with abalones, the urchins are the major herbivores who compose the kelp forest clean-up crew, consuming the old blades normally shed by the messy plants. Most of the time, the urchins hide under rocks and in crevices, never venturing more than a foot or two from their homes. But by 1960, scuba divers had begun to report the urchins crawling out of their hiding places and forming great fronts composed of several dozen or more of the spiny sea creatures, who advanced upon and devoured the already ailing kelp plants. By that year, hundreds of acres off San Diego had been denuded, and in the newly barren areas, observers often found sea urchins, who apparently continued to subsist on microscopic algae that grew on the bottom. The urchins thus effectively prevented new kelp plants from taking hold and getting re-established.

Southern California’s kelp beds seemed to be in a state of real emergency. An explosion of kelp research resulted, with San Diego scientists leading the efforts. Biggest of all was something called the Kelp Habitat Improvement Project, in which various state agencies, Kelco, and university-based researchers joined forces to try to understand what had happened off Point Loma and to look for ways to repair the damage. In the ensuing years, answers began to emerge to many basic questions, and the project scientists began to take action. They reasoned that since all of the urchins’ natural predators had either been wiped out (in the case of sea otters, who were hunted to extinction off San Diego almost 150 years ago) or severely reduced in number (as in the case of sheephead fish and lobster), it was appropriate for humans to fill that void and try to restore the ecological balance. The research team thus developed a procedure for controlling the urchins. It involved sprinkling quicklime into the areas where urchins were known to proliferate; the chemical reacted with the sea water and gave off heat, in effect burning the urchins to death.

How well did it work? The marine biologists are still arguing about some things. One important event that occurred in 1963 (about the same time the quickliming began) was that the sewage outfall was moved from San Diego Bay to a point about two and a half miles off Point Loma, more than a mile past the kelp bed. Some scientists think this improved the water quality in the Point Loma kelp beds. (And researchers learned in the 1970s that the clarity of the water is crucial to kelp forests, since the plant’s female reproductive cells only became fertile when there’s a certain percentage of light in the water.)

The quickliming indisputably killed urchins (along with some other less offensive kelp forest inhabitants), and in the urchins’ absence, the giant plants began to return. A more difficult question to answer is whether the urchin populations would have died off naturally. Some evidence suggests this can occur. Whatever the explanation, aerial photos of the Point Loma kelp forest taken over the years tell a dramatic story: virtually absent in 1960, the giant kelp by the late 1960s had once again grown into a thick blanket that covered nearly 1900 acres on the surface of the coastal waters.

Aerial photos of that blanket taken regularly since then show an amazing amount of variation from one year to the next. It’s a variation inconceivable in any terrestrial forest; the boundaries of the kelp bed shift as if annually redrawn in the dark by a poor-sighted copy artist. In fact, the principal rearranger of kelp boundaries tends to be winter storms, which generate waves that can dislodge the Macrocystis — particularly the oldest and youngest plants — like a giant plucking daisies. The destruction then continues as the dislodged plants move through the forest, their heavy holdfasts bludgeoning neighboring plants, their fronds entangling with and damaging healthy neighboring fronds. But if winter storms during the Sixties and Seventies changed the shape of the local kelp blanket from year to year, the blanket off Point Loma basically remained in place. By the summer of 1982, Kelco assessed it as being in excellent condition. Then the worst el nino of recorded history rolled into town.

This was the beginning of another true eco-catastrophe, but in a sense this was an ecocatastrophe that kelp ecologists could welcome. By 1982 they had gathered twenty-five years of kelp forest data, data they hoped would help them make sense of a big new disturbance. And the el nino heralded not one disturbance but the beginning of a veritable underwater soap opera.

It actually began far away, in the tropical Pacific, where the sea surface temperatures in May of 1982 began rising for reasons that are still not understood. The warmer equatorial waters set off a chain of far-reaching events; one of the consequences was an unusually deep atmospheric low-pressure center in the Aleutian Islands off Alaska and stronger than normal westerly winds. These brought an extraordinary number of severe storms to the West Coast of the United States, where they made landfall much farther south than normal. In San Diego, the first of eleven major storms struck on November 30, 1982. Over the next four months, waves higher than eighteen feet were measured no less than six times. To put that in perspective, only ten waves of similar height had been measured from 1900 through 1982. That sort of battering devastated all the giant kelp canopies throughout San Diego — and everywhere else Macrocystis grows from Baja northward. Virtually overnight, at least 1400 acres of giant kelp canopy disappeared in the Point Loma bed, according to Paul Dayton and Mia Tegner, the Scripps Institution of Oceanography’s principal authorities on giant kelp.

Dayton and Tegner dove extensively during the spring of 1983, and they estimate they surveyed about 10,000 square meters of underwater Macrocystis. What they found certainly didn’t spell the end of the giant kelp. Although the dense kelp on the surface of the water had been destroyed, many plants retained their holdfasts and parts of the plants below the surface. (The percentage of underwater destruction ranged from thirteen to sixty-six percent and seemed to depend on depth, with the plants in the shallowest areas suffering the worst beating.) That spring of 1983, the water temperatures dropped from their unusually high levels back into the normal range, and “as a result, the kelp grew like crazy for a little while,” Tegner says. “The storms had cleared a lot of open space. So there was tremendous recruitment of young plants.” By fall, however, most of these had died, as ocean temperatures from August through October climbed above sixty degrees and stayed there, sometimes spiking up to more than seventy degrees.

Way back in the late 1950s, during the big el nino that occurred then, kelp researchers had observed the disastrous effect that bottom temperatures of more than sixty degrees can have on kelp. An obvious early hypothesis was that the heat alone bothered the plants. Then research in the early 1970s showed that kelp tissue in the laboratory could thrive at temperatures as high as sixty-eight to seventy-seven degrees. Tegner says it now seems clear that the problem with warm water (from the giant kelps’ perspective) is that plankton grow so well in it that they gobble up all the nutrients. In water that warm, the giant kelp in effect starves. San Diego’s kelp got a respite from these barren seas when the temperatures plunged for a month or two at the end of 1983. But then the water temperatures heated up again and remained high until around November of 1984.

By April of that year, Tegner and Dayton had begun to voice the concern that Point Loma’s giant kelp might take a long time to return to its previous densities. Giant kelp doesn’t live alone. It’s part of an entire community of plant life; some half-dozen different species of kelp form “understories” in the sections of San Diego’s shores where the giant kelp also grows. Normally, the giant kelp is dominant; it’s very hard for other plants to invade it because of Macrocystis's ability to climb quickly above the other plants and receive the majority of the available sunlight. But when certain species of the understory reach a certain density, they can prevent the giant kelp from invading. Those savage storms of the winter of 1982-83, which so damaged the giant kelp, hardly hurt the understory species at all, and the warm water probably hurt them less, according to Tegner. As the warm water persisted through the winter of 1983-84, Dayton and Tegner wondered if the giant kelp’s ecological competitors might not give it a serious battle.

The warm el nino waters finally dissipated by November of 1984, and it didn’t take long for the answer to emerge: though initially sparser than they had been in years, the young giant kelp plants soon had shot up past their small-fry competitors, and by the end of 1985, feathery blades of giant kelp once again could be seen covering hundreds of acres of the surface of the water off Point Loma.

And then, having survived the most violent storms of the century, followed by two years of starvation; having escaped a recurrence of the urchin plagues like those that occurred after the 1957-59 el nino, the giant kelp suffered yet another disaster. Tegner says the first signs that trouble might be brewing began to appear in the summer of 1984. when the giant kelp was still suffering from the nutrient-bare warm waters. Particularly down at the south end of the Point Loma kelp bed.

Kelco and Scripps kelp researchers began noticing that the Macrocystis leaves were beginning to look chewed up; the plants just didn’t look good. “By the winter [of 1984-85], it was very obvious that something serious was going on,” says Tegner. From January through June of 1985, the period when the canopy should have grown both in size and in density, it instead shrank by sixty percent.

Tegner says it took a while to put all the pieces together, but by late spring of 1985, the major clue was inescapable: up to fifty percent of all the blades on the giant kelp plants in certain parts of the Point Loma forest were curling. The immediate cause was obvious to the kelp ecologists. One inhabitant of the forest is the kelp curler, a tiny invertebrate that makes a cozy home for itself by folding over one corner of a kelp blade and cementing it shut with a gummy mucus. Normally, however, the kelp curlers don’t do this to enough kelp leaves to harm the plant. Usually the kelp curlers are eaten by a little fish called the kelp surfperch, which normally lives amid the fronds of the giant kelp canopy. When so much of the canopy disappeared throughout 1983 and 1984, the surfperch numbers probably declined precipitously. And the kelp curler population apparently exploded. “These animals are all small, but there were such huge numbers of them,” says Tegner. “It was very much like a plague of insects on land vegetation. They’d eat off all the blades, so you would see stipes [stalks] with just the floats. And eventually those would disappear. Whole areas at the south end [of the Point Loma forest] were completely denuded.”

The researchers from Scripps began keeping track of what percentage of the kelp leaves were curling in June of 1985, and Tegner says the numbers began to decline by late that year — just as surfjperch numbers seemed to climb, and surfperch guts examined by Tegner and her associates appeared to be filled with kelp curlers. The giant kelp looked increasingly good throughout 1986. “We’ve had very substantial recovery,” Tegner said.

Marine biologists like Tegner must surely have one of the longest commutes to work of anyone in San Diego. One day this past December, she and a team of three other scientists from Scripps prepared to head out for a routine day of diving. The drive through La Jolla traffic to Scripps is the easy part. But then they have to get from their offices at Scripps out to where the giant kelp live. And though the kelp beds aren’t far, reaching them is a multistep process made up in large part of drudgery: filling the heavy scuba tanks with compressed air, gathering up all the diving gear, loading the dozens of items — fins, belts, collecting bags,' charts, lunches, jackets, sunglasses, wet suits, dry suits, cornstarch, weight belts, and more — into the back of a truck. Then the kelp researchers must drive to Quivira Basin on Mission Bay, where Scripps keeps a twenty-foot aluminum launch. Once again all the gear must be transferred: from the truck into handcarts, then from the handcarts into the boat. The actual boat ride through Mission Bay, out the channel, and south along Point Loma seems easy, but on this day it was past eleven o’clock by the time the scientists reached their goal at the very southern end of the kelp bed, which stretches from Sunset Cliffs in Point Loma down to south of the lighthouse.

The Scripps scientists concentrated their work on the Point Loma forest, which is the biggest. On this particular day, they uttered exclamations of pleasure to find a yellow buoy where they had left it. Sometimes lobster fishermen or motorboatcrs cut the buoy adrift, and the scientists have to drop an anchor. But an anchor tends to disturb the bottom, and in this particular part of the kelp forest — notable for its poor visibility — that was the last thing the researchers needed.

On this trip, the most senior member of the group was forty-five-year-old Paul Dayton, who began studying kelp at Scripps sixteen years ago. These days teaching and administrative responsibilities only leave Dayton the opportunity to dive two or three times a month. In 1974 he hired Mia Tegner, who had just completed a doctorate at Scripps in which she studied the interactions of sea urchin eggs and sperm. Today Tegner ranks as one of the most knowledgeable abalone and sea urchin biologists in California. She now dives in the kelp forest twice a week, and two additional assistants, Paul Parnell and Cleridy Lennert, bring back underwater data for the team even more often.

This day all four plan to share the mundane tasks involved in trying to expand human knowledge of how the kelp forest works. Within minutes of tying the launch to the buoy, the four scientists, now garbed in diving apparatus, each roll over backward off the sides of the little motorboat and slowly sink beneath the water. In all directions, the ends of Macrocystis fronds can be spotted floating on the blue-dappled surface. Distant ones look like some sort of unrecognizable litter, but up close the blades dance sinuously, and the floats glow with a rich, golden color in the luminous sea of green.

The scientists' destinations, some fifty feet or so beneath the surface, are four lines of fabric-covered lead, each one more than seventy-five feet long, which Tegner and Dayton fixed in place almost four years ago. Parnell and Lennert's task this morning is to swim along the lines and map every significant plant growing within two meters (about six and a half feet) of each of the four lines. To do the work, the two divers are armed with clipboards bearing special waterproof paper on which are written detailed notations — what species were growing where, how high — from the last time the team mapped here, some six weeks before. This day they planned to record any changes. Dayton and Tegner have similar lines at four other underwater “stations” throughout the kelp bed; all are mapped every other month on average. The idea is that closely following the lives of individual plants in different parts of the kelp forest can give some insight into the health, structure, and organization of the forest.

While Parnell and Lennert map, Tegner and Dayton plan to swim along the same lines, but with another goal — namely, to collect every single piece of drift algae floating within two meters of each side of the line. That may sound simple, but the scientists say it often isn't, particularly at this site, where visibility on the bottom often is so bad that the divers can't see more than five to ten feet in front of their masks. In such murk, it’s also tough to distinguish between plants that have broken off and those that are still lightly anchored to the bottom. It forces Tegner and Dayton to work slowly and cautiously. When Tegner finally resurfaces and climbs into the launch, she growls, “I kept losing the line! I’d get two feet away from it, and then I’d lose it again!” Yet she’s managed to tuck a reasonable seaweed salad into a yellow net bag that she carries.

Today it’s a mixture composed primarily of a delicate annual bottom kelp called Desmarestia, which has infested the south end of the Print Loma forest this year. (An opportunistic species, it is rare under normal conditions but tends to spring up after disturbances.) But pieces of the giant kelp and a few of the understory species are mixed in, and Tegner also has bagged a badly eaten strand of the feather boa kelp, which grows in much shallower water but sometimes breaks up and floats out to the kelp forest. “Then the urchins grab them because they’re good to eat,” she says. A piece of emerald green surf grass in one of the collection bags also found its way out to the forest in similar fashion.

When the team of scientists makes it back to Scripps at the end of this day, they’ll dump each of the bags of drift algae out onto a table, sorting them into the different species. Then Parnell will weigh each species collected along each of the lines, carefully recording the information. The individual numbers are virtually meaningless. (So what if someone collected 110 grams of Laminaria farlowii from a hundred-meter-square patch of ocean floor on one morning in January of 1987?) But drift algae feeds many creatures in the forest. As it becomes more or less abundant, effects ripple widely. Today’s numbers are one tiny piece that may someday fit into part of one of the puzzles found in such abundance here.

With the tasks at the south station completed, Parnell pilots the launch to the station at the far north end of the kelp bed. Here Dayton and Lennert plan to do the mapping, but Tegner and Parnell will perform the even more tedious job of checking to see what percentage of the giant kelp leaves have been curled by the tiny creatures who caused so much trouble in 1985. To check for kelp curlers, the scientists first dive down to the bottom of the forest and pick a giant kelp plant at random. Then, beginning at the bottom, they count every single blade, carefully checking each one for curling and writing down the total number of blades and the total number of curled blades. Then they start again with another plant. By the time Tegner and Dayton pile back into the boat after a half-hour or so this activity, they have counted a total of 606 blades, fewer than two dozen of which showed any signs of curling, a 1.5 percent curling rate — far less than the forty to fifty percent rate that the invertebrates inflicted on the forest in 1985.

With the scientists’ air supplies dwindling and their specific goals accomplished, Parnell steers the launch back toward Mission Bay. The group has spent less than an hour and a half under water, and it takes at least that long to return to the dock, unload and wash all the gear, shower, load everything back in the truck, drive back to Scripps, and unload everything. No one complains; that’s the nature of this work, and no one is more aware of that than Paul Dayton, who’s been studying kelp for more than twenty years. Dayton is more apt to complain about something else: the frustrations of trying to better understand something so little understood that no one even knows what part of the picture scientists ought to be looking at.

When Dayton first began his work at Scripps, he set up one station right in the middle of the Point Loma kelp bed, and he began doing studies there. It seemed a reasonable approach. No one knew then that sea urchins tend to settle and grow on the edges of the kelp forest or in holes created by storms. So by studying just one section in the center of a forest one could get a completely distorted picture of what was happening to the urchins, one of the most important elements in the forest ecology. Or to take another example, when Dayton began his Point Loma work, no one guessed that the very shape of the forest alters currents so that nutrients move through different parts of the forests at different speeds.

Eventually he added two stations at different depths in the center of the forest, and when the el nino began, he and Tegner added two more, at the north and south ends. Tegner says, “Now obviously, you can’t have an infinite number of [research] sites — but the question of how many you do need is a nontrivial one.” As time has gone by, Tegner and Dayton say they’ve become convinced that the most important challenge in ecology today is this one of properly integrating the varying scales of space and time.

They point out that pressures in the real world, such as funding and academic promotional procedures,tend to force ecologists into two- and three-year study projects, while few natural patterns are that short. Terrestrial ecologists certainly share that problem, Dayton says. But he says terrestrial ecologists also start from a base of incomparably more common knowledge. “A cynic could say, ‘Well, you [marine biologists] haven’t really learned anything that John Muir didn’t know a hundred years ago.’ And there’s a certain truth to that.” Given the immensely more sophisticated base of knowledge that terrestrial biologists have, Dayton says, “I sometimes feel like, ‘Gee, here I’m bashing my brains out to move us up from 3000 years to one hundred years ago .... Maybe my students will bring us up to the present generation.’ ”

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