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May 26, 1997

UCSC marine biologists find biodiversity flourishing between Monterey Bay tides

By Mari N. Jensen

[Photo of John Pearse with students at beach] At the base of a cliff below the Santa Cruz lighthouse, early morning low tide finds 47 student researchers from UCSC poking under boulders, peering into tide pools, and sifting through surf grass to find every species inhabiting the rocky zone between the tides (photos). It looks like fun, and is, but there's more to it: The students' work is part of a unique long-term study to determine how increased human use has affected the wildlife living in this narrow zone along central California's popular coastline.

Their results might come as a surprise: When comparing surveys conducted in the early 1970s to a 1996 survey, the researchers found no decrease in the number of species despite increasingly heavy human use of the Santa Cruz County and southern San Mateo County sites examined. John Pearse, professor emeritus of biology at UCSC, and his student colleagues now have the most complete long-term species lists available for specific sites on central California's rocky shores.

Overall, the researchers have cataloged 723 species at 10 sites, although not all species occur at all sites. Students found more total species at each location in 1996 than in the early '70s. Explaining the higher numbers for 1996, Pearse says, "There's a lot of rare species you see only every third or fifth visit, because they're inconspicuous--or you're not trained to see them."

At each site, only about half the species found in the '70s also surfaced in 1996. That high turnover "is part of the diversity, part of the excitement," Pearse says. Such changes in species composition are not evidence of deterioration, he says, but of dynamic ecosystems.

Pearse's group presented the latest findings of its ongoing study as a poster at the annual Monterey Bay National Marine Sanctuary Symposium in March. His coauthors were Eric Danner and Lani Watson, both graduate students in ocean sciences, and Chela Zabin, a senior in marine biology. Their poster was named "Best Overall" at the symposium.

To document changes in the environment, such long-term studies are essential, says Andrew DeVogelaere, research coordinator and senior scientist at Monterey Bay National Marine Sanctuary. "For us, it's a unique data set," he says. "To have a comparison from 25 years ago on rocky shores is incredible. Most studies last two to four years."

Rafe Sagarin, a researcher at Stanford University's Hopkins Marine Station in Pacific Grove, says of Pearse's study, "His work is really important for looking at this basic but unresearched question of what's out there--and how it's changing."

Pearse could never have gotten such complete information without the students who scour the intertidal for its hidden life-forms. His Biology 161L class searches for species at sites ranging from the north side of Pigeon Point in San Mateo County south to Pleasure Point between Santa Cruz and Capitola. Clothed in chest-high waders or wet suits, the group assembles at the site of the day about an hour before the morning low tide. The students fan out over the slick rocks for the day's treasure hunt, sometimes accompanied by several dogs and equipped with clipboards, species lists from previous visits, field guides, nets, and vials.

Following the tide out, students wade through the iridescent green-blue seaweed to find and identify the intertidal's myriad of inhabitants, such as scaled worm snails and brilliant orange sponges. Some of the most spectacular finds are tiny sea slugs, called "butterflies of the sea" because of their astonishing colors. The robin's-egg-blue body of Phidiana crassicornis has neon-blue racing stripes and is less than an inch long. The brown frill running the length of its body helps it breathe, explains Jeff Newman, a junior in biology and environmental studies. He adds, "The early mornings are rough, but the creatures make it worth it."

Teaching assistant Jay Park has been working on the survey for four seasons. For him, doing research is the motivation. "We're doing research that will help us understand what's here in Monterey Bay," he says.

Pearse, who came to UCSC in 1971, is regarded as an expert on Monterey Bay's nearshore ecosystems. A handsome, solidly built man with graying hair and beard, it's easy to imagine him at the helm of a ship. But the Sea-Wolf never had Pearse's ready smile--or his Guatemalan sweatshirt.

"John's an amazing teacher," teaching assistant Katrina Hart says. "Pretty much any question you have, he'll be able to explain what's going on."

The class continually discovers new species for each location. Pearse says, "I didn't anticipate we would have this richness. We may have an increased number of species, but I don't know that yet." The researchers must do further analysis to determine whether there are indeed more species present, or whether the group is just more experienced at treasure hunting.

California Sea Grant and the Monterey Bay National Marine Sanctuary fund Pearse's study.

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