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Stanford Report, February 19, 2003

Marine biologists work to solve 'black box' mysteries of ocean life


New studies conducted in coastal waters from California to the Caribbean are forcing marine scientists to abandon long-held assumptions about life in the ocean and how best to protect it.

"We used to think that marine organisms went vast distances when they floated in the sea, but it turns out that that they are not really going that far," said Stephen R. Palumbi, a professor of biological sciences at Stanford's Hopkins Marine Station. "We're finding that the oceans are not just one big neighborhood but are chopped up into smaller ones. In fact, every bit of coastline might be a small neighborhood that we can manage and try to preserve on its own."

Hopkins Marine Station biologist Mark Denny records the forces that ocean waves exert on intertidal organisms at the marine reserve in Pacific Grove. Photo: L.A. Cicero

Palumbi and fellow Hopkins biologist Mark W. Denny discussed this new approach to marine ecology at a symposium titled "Opening the Black Box: Understanding Ecosystem Dynamics in Coastal Oceans," at the annual meeting of the American Association for the Advancement of Science (AAAS) in Denver Feb. 15.

"In science, a 'black box' is something that you know what goes in and you know what comes out, but you don't know what happens in the middle," explained Denny. "We know that there are organisms on the shore and that they eventually have kids that end up on the shore in a particular pattern. What we don't know is the chain of mechanism that hooks the parents to their kids and explains the pattern. 'Opening the black box' means exposing all the links in that chain, from the small scale to the very big scale, to explain what's going on."


Denny, Palumbi and the other participants in the "black box" symposium are affiliated with the Partnership for the Interdisciplinary Study of Coastal Oceans (PISCO) -- a consortium of marine scientists from Stanford, Oregon State University (OSU), the University of California-Santa Barbara (UCSB) and the University of California-Santa Cruz (UCSC). Established in 1999, PISCO's mission is to conduct scientific research that leads to a clear understanding of the different ecosystems that are found along the West Coast -- from Washington state to Southern California.

"There's certainly a lot of variation along the coast," observed Denny, the John B. and Jean De Nault Professor of Marine Sciences at Stanford. "For instance, if you put little bare plastic or ceramic plates down in the intertidal zone in Oregon and come back a couple of weeks later, the plates are likely to be covered with barnacles."

But when Denny and his colleagues tried the same experiment a few hundred miles south of Oregon along California's Monterey Bay, the results were dramatically different.

"We put out 200 plates for two years running, and we had maybe 10 barnacles on all of them," he recalled. "So there are just whopping differences in the rate at which barnacle larvae are being recruited into the system, depending on where on the coast you are."

Species distribution also varies on much smaller scales, as Denny learned when he and his students counted the number of new mussels that had attached themselves to a set of ordinary plastic kitchen scrubbers installed along a short stretch of shore. "It turned out to be real patchy for some reason. There were some spots out there that reliably recruited mussels, and others just a few feet away that didn't, so a lot of the variation that's going on is being driven at the small scale rather than the large scale."

Making waves

One factor that may affect the abundance of marine organisms -- on a small and large scale -- is the constant pounding of the surf against the shore.

"It's obvious that when waves crash, they apply really huge forces to things that live out there," Denny said, noting that a 6-foot wave applies the same kind of force to barnacles and other tiny creatures that a 1,000 mph wind would apply to a person standing on land.

"There aren't many things on land that would survive that kind of super-duper hurricane, but that's what these things put up with every 10 seconds when waves break on the shore," he noted.

To measure the force of individual waves, Denny and his colleagues developed a decidedly low-tech device that consists of a plastic golf ball attached to a spring scale.

"We call it a dynamometer, to give it a fancy name, but it's cheap to make, and we make them by the hundreds," he said. To measure wave forces along Monterey Bay, Denny and his coworkers drill holes into the rocky shoreline, then insert a dynamometer into each hole. When a wave hits the plastic golf ball, it stretches the spring, giving researchers an accurate measurement of the amount of force that struck the shore.

"The dynamometers see a lot of force, but it varies from place to place," Denny noted. "For instance, we have one transect with about 100 dynamometers placed about 18 inches apart. What we found is that the most exposed place will see about 13 times the force as the least exposed place just a few feet away."

Denny and his students are in the process of designing a high-tech version of the dynamometer that will replace the metal spring with an electronic sensor that continuously transmits wave force data back to the lab. He and his colleagues also are using nickel-size computers called I-Buttons that record the body temperature of shoreline organisms every 10 minutes over a two-week period.

"The take-home message is that the technology is available to measure these kind of small-scale variabilities," he concluded. "Doing big science on a big scale is important, but if you're really interested in opening the black box, you also have to look at smaller scales to be able to get the whole picture."

Barnacle babies

At the Palumbi lab, researchers have turned to genetics to unravel one of the great mysteries of the ocean black box: Do newborn marine organisms travel vast distances, or do they tend to stay close to home?

"When you're managing marine ecosystems, it's important to know where organisms are going in the sea," Palumbi observed. "Are they going a mile or 10 miles or 100 miles in their lives? And what happens when they reproduce, because a lot of marine organisms don't reproduce by dropping big babies on the ground like mammals do. They, in fact, release very small eggs or very tiny larvae out into the water that drift in the ocean currents."

To find out how far marine larvae drift, Palumbi and his colleagues have been comparing different populations of Balanus glandula -- a common barnacle found from Baja California to Alaska.

"It's a model species that's been studied intensely -- the white rat of intertidal biology," Palumbi quipped. "Barnacles grow all over the rocks, they foul the hulls of boats, they grow all over piers and jetties. Although adults don't move, the larval form was thought to drift hundreds of miles in the ocean currents. But you have to test these things. You can't just assume they move a lot and then base all of your management on that assumption."

Human and barnacle genomes

How do you determine if barnacles growing along the coast of Oregon were actually born hundreds of miles away in California? One method is to look for subtle similarities in their DNA -- a process that was both tedious and time-consuming until the Human Genome Project came along.

"The Human Genome Project led to refinements of genetic sequencing technology, so now we can look at the genetics of different barnacle populations more intensively and with higher resolution than ever before," Palumbi noted.

He and his colleagues recently conducted DNA analyses of barnacle colonies in Washington, Oregon and California. "We were able to extract enough DNA from even the microscopic larvae of barnacles to map genetic differences," he said. The results showed that larvae in all three locations had remained close to the shores where they were spawned.

"What we thought we knew about larval biology and the currents out there in the sea was wrong," Palumbi noted. "We found that there are local populations that are not mixing up and down the coast over scales of hundreds of miles. Instead they're mixing at scales of about 6 to 12 miles -- which means that the scale over which you should be managing these ecosystems also should be 6 to 12 miles. That's the scale at which you would manage a human community -- a town or a county, not a whole state. That's the real surprising news about our study: The first time we looked at the genetics with high-resolution techniques, we saw a pattern different than previous assumptions."

Neighborhood watch

DNA analyses of other marine populations around the world have yielded similar results. In a study published in the Jan. 3 edition of Science, researchers described finding genetically distinct populations of gobies -- a small tropical fish -- living within 13 miles of one another in coastal waters off Puerto Rico. Goby larvae remain adrift in ocean currents for three weeks, but instead of traveling hundreds of miles, the tiny creatures appear to stay close to their coastal birthplace.

"The ocean is quite likely to turn out to be collections of neighborhoods," said Palumbi, who last month authored a Pew Oceans Commission report calling for the creation of a network of marine reserves from Hawaii to Florida.

"If we're going to manage the ocean, it's really going to be on a neighborhood-by-neighborhood basis," he added. "The very existence of those neighborhoods is a very different way of looking at the ocean than we thought before. Ten years ago, the conventional wisdom was that these populations were just one big mix up and down the coast -- and that's how fisheries are managed at the state and local level. The fact these neighborhoods exist means that it's possible for there to be local benefits, and that's one of the things that will make a big difference in getting local communities to begin protecting chunks of the sea."

Stephen R. Palumbi, professor of biological sciences, presented findings with Denny Saturday at the anual meeting of the American Association for the Advancement of Science in Denver suggesting that marine organisms do not travel as far as previously believed and that coastal areas are “chopped up” into small neighborhoods. Photo: L.A. Cicero