UC Santa Cruz Tip Sheet February 1996
Research news and feature ideas, issued periodically by the UCSC Public Information Office For more information, contact Robert Irion at (408) 459-2495 or irion@ua.ucsc.edu
* Marine biology * Early ATOC transmissions show no obvious harm to marine animals
During the first five transmission cycles from the California sound source in the Acoustic Thermometry of Ocean Climate (ATOC) project, biologists observed no dramatic changes in the behavior of marine mammals that would have required them to stop the broadcasts. Oceanographers hope to use ATOC to measure the hypothesized influence of global warming upon the sea. However, the project came under fire from some quarters for the effects that its low-frequency, 195-decibel sounds might have on animals-- especially deep-diving whales and elephant seals.
As of mid-January, ATOC scientists had spotted large numbers of whales, dolphins, and other animals near the sound source during aerial and boat-based surveys, both when the source was on and when it was silent. Although the scientists detected no apparent changes in behavior, any conclusions must await the collection of more data plus detailed analysis.
"Even though we got a late start, the research program is going extremely well," says UCSC biologist Dan Costa, who leads ATOC's Marine Mammal Research Program for California. "The exciting thing is that we have seen lots of animals in the study area even during the winter months, when we weren't sure what to expect."
This spring, the team will transport several elephant seals near the sound source and monitor their returns to shore at Ano Nuevo, on the central California coast. Time-depth recorders attached to the elephant seals will show whether the deep-diving animals steer away from the sounds or change the depth or duration of their dives during their trips home. The Marine Mammal Research Program is scheduled to run at least through September 1996.
Contact: Dan Costa--(408) 459-2786 or costa@biology.ucsc.edu
* Biodiversity * Frog embryos harmed by combined acidic water and ultraviolet light
Acidic water and ultraviolet light damage the embryos of frogs far more seriously when acting in tandem rather than as separate factors, according to a laboratory study at UCSC. Researchers exposed the eggs of a common species of frog to various levels of acidity and UV-B radiation, the most harmful form of ultraviolet light. By themselves, even the most acidic water or the most severe UV-B radiation did not kill many embryos. But when the team combined the two environmental assaults, as many as half of the eggs failed to hatch.
Ecologists should look for similar interactions in nature as they try to explain why many populations of amphibians around the world are dying out, the study's authors say. Stresses such as habitat loss, a thinning ozone layer, acid rain, pesticides, disease, and global climate change may combine to wreak more havoc on frogs, toads, and salamanders than any one factor could by itself. Indeed, some scientists now suspect that for any given group of amphibians in trouble, two or more such factors may interact synergistically--that is, the combined effects of the stresses are far greater than the sum of their individual effects.
"People have been looking for a smoking gun to explain the amphibian die-offs, and there isn't just one smoking gun," says Michael Soule, coauthor of the study and professor emeritus of environmental studies at UCSC. "There's quite an armamentarium out there. We're just beginning to look at the interactions among these possible causes." The UCSC team published its work in the October 1995 issue of Conservation Biology.
Contact: Michael Soule--(408) 459-4837 or soule@cats.ucsc.edu
* Oceanography * Iron fertilization experiment: Iron's chemical dances in the sea
The sea turned green with a teeming bloom of tiny marine plants when scientists fortified the water with a half-ton of iron. The June 1995 experiment, called IronEx-II, vividly confirmed that marine plants are stunted by the iron-poor waters of the equatorial Pacific. Researchers on the cruise were interested not in controlling earth's climate by soaking up carbon dioxide with plant growth, but rather in studying the complex interactions between sea life and the chemistry of the ocean.
For instance, iron's chemical associations in the sea had been somewhat of a mystery. Before the cruise, UCSC postdoctoral researcher Eden Rue found that almost all dissolved iron in the ocean acts like a celebrity leaving a limo: It attracts hordes of devoted molecular fans, in the guise of strongly binding organic molecules. Biologists had assumed that the tiny plants called phytoplankton could only consume inorganic iron, so Rue's discovery raised questions about what form of iron the plants actually use.
Working in an ultraclean lab lashed to the rolling ship, Rue measured the different types of iron forms by adhering bound iron onto a drop of mercury--an electrochemical technique she devised. The 100-fold increase in iron during the cruise not only turned the water green with plants, but as Rue found, quadrupled the amount of iron-binding molecules in less than a day.
Phytoplankton apparently can thrive even if nearly all the iron is bound. In fact, Rue suspects that plants somehow produce binding molecules to capture the dissolved iron, which may otherwise clump into particles and settle to the seafloor. Rue compares the dose of iron to a smorgasbord for phytoplankton. Producing the binding molecules, she says, "may be a way for them to stack food on their plates." She presented her work in February at an ocean sciences meeting in San Diego.
Contact: Eden Rue--(408) 459-2585 or elrue@cats.ucsc.edu
* Environmental toxicology * Metals in San Francisco Bay may repeatedly contaminate the water
Preliminary measurements of trace metals in the waters and sediments of San Francisco Bay suggest that cleaning the most polluted parts of the bay could be a Sisyphean task. A chronic supply of metals in contaminated sediments may rise into the water for decades, confounding the attempts of regulators to purge toxic metals from the wastes of industry and civilization.
Scientists face more work to confirm that bleak scenario. But early studies at two sites in San Francisco Bay hint that metals re-emerging from sediments contaminate the water at least as much as--if not more than--all of the runoff and discharges from streets, sewers, and factories combined.
Postdoctoral researcher Ignacio Rivera-Duarte of UCSC used painstaking ultraclean methods to determine the concentrations of several metals in the water, as well as in "porewaters" that squeeze among the grains of sediments. This led to a picture of the relative rates at which metals flow into the bay's waters, then into the sediments via tiny plant cells that sink to the bottom, then back into the water when the plants decay. That "remobilization" of trace metals from sediments turned out to be the biggest source of most of the metals in the water.
At heavily polluted sites in the southern San Francisco Bay, metals buried in the sediments years ago may continue to infiltrate the water for the foreseeable future, like sap that still oozes from telephone poles. As a result, that part of the bay may have prolonged problems with trace metals even if regulations demand that sewage, industrial wastewater, and other effluents be virtually free of potentially toxic substances. "We're not saying that contaminants in wastewater are no longer an issue," says team leader Russell Flegal, a geochemist. "New inputs from wastewater discharges and surface runoff would only add to the problem." Rivera-Duarte discussed the study in February at an ocean sciences meeting in San Diego.
Contact: Russell Flegal--(408) 459-2093 or flegal@rupture.ucsc.edu
* Geology * Blobs of hot lava, bubbling up toward the seafloor? Probably not
It's a common image in geology textbooks: Molten magma wells up from the planet's bowels to the seafloor at midocean ridges, giving birth to new slabs of the earth's crust. The magma, a fiery orange or red, ascends in teardrop-shaped blobs through what look like inverted funnels or gigantic pipes. There's a problem with that image, say scientists at UCSC. It's probably wrong.
Instead of a pipe, the plumbing under a midocean ridge may act like a sponge, and a very bad sponge at that. A typical chunk of the earth's mantle in one of these zones, the scientists believe, holds just 1 or 2 parts magma per 1,000 parts unmelted rock--a far smaller ratio than predicted by the reigning model of seafloor spreading.
What's more, as the magma oozes upward through tiny channels, it appears to stay in chemical contact with the mantle rocks around it. Other researchers have assumed that once magma forms deep under the ocean floor, it rises quickly and no longer reacts with the surrounding mantle.
"Midocean ridges are the biggest magmatic systems on the planet," says Quentin Williams, a UCSC mineral physicist. "The previous picture of how these systems work may not be accurate. The chemistry of what comes out at the top seems to tell us that the magma percolates upward instead of flowing through conduits, and that it continuously bathes the mantle in a very small amount of melt." Williams and two colleagues, led by graduate student Craig Lundstrom, published their results in the December 22 Science.
Contact: Quentin Williams--(408) 459-3132 or quentw@rupture.ucsc.edu
Editors and reporters: To receive electronic versions of these and other items about research at UCSC, send a message to irion@ua.ucsc.edu. For news releases and other resources, go to UCSC's "Services for Journalists" site on the World Wide Web: http://www.ucsc.edu./news/journalist.html
Press Releases Home | Search Press Releases | Press Release Archive | Services for Journalists
Maintained by:pioweb@cats.ucsc.edu