News tips from UC Santa Cruz Ocean Sciences meeting -- February 12-16, 1996 San Diego, California

For more information, contact Robert Irion or Erik Stokstad at (408) 459-2495 or irion@ua.ucsc.edu / stokstad@cats.ucsc.edu

State of the Ocean address: The Sverdrup Lecture Monday, February 12, 1:30 p.m. Speaker: Margaret Delaney (408) 459-4736 or delaney@cats.ucsc.edu

Levels of carbon dioxide in the air. Temperatures of the tropical sea surface. "Conveyor belts" in the ocean linking high and low latitudes. These, says Margaret Delaney, are some of the challenges facing the burgeoning field of paleoceanography. The discipline, Delaney says, is maturing into one that can help scientists understand our planet--providing not just snapshots of long-lost eras, but clues about what the future may portend.

Delaney, an associate professor of marine sciences at UC Santa Cruz, will deliver the annual Sverdrup Lecture in paleoceanography, named for the late Scandinavian oceanographer H. U. Sverdrup. Delaney last month became the fourth editor of the international journal Paleoceanography, founded in 1986 to help unite chemists, oceanographers, geologists, climatologists, and others who contribute to broad-based studies of how earth's oceans have changed over time.

Paleoceanographers have a growing toolbox at their disposal to probe ever more finely into the recent history of the oceans and ever more deeply into the distant past. Fast computer models, advances in drilling technology, careful analysis of sediments and fossilized organisms, and clever uses of the isotopes of oxygen, strontium, and other elements all have turned new pages in the marine record books.

"Researchers have detailed ice-core records about earth's atmosphere and climate for the last few hundred thousand years," Delaney says. "Now, we're getting the same sort of information from the ocean on that timescale. We can compare those data sets to work toward understanding how the ocean, atmosphere, and climate are linked."

However, ice cores can't help scientists peer tens of millions of years back in time, to eras when earth's climate was radically different than it is today. Instead, clues lurk in various places on land and beneath the ocean floor. "There are a hundred million years of records in the ocean, which we can use to get at long-term links between the ocean and the climate," Delaney says. "But it's a matter of learning how to interpret all of the data--that's the major issue in the field today."

One example is the dispute over how much the temperature of the tropical ocean--the planet's biggest reservoir of heat--can change. Some studies point to stable temperatures; others suggest large warmings and coolings. It's a crucial issue for sorting out how oceans affect earth's heat budget and, ultimately, how they drive short-term and long-term changes in climate and geochemistry.

Paleoceanography, says Delaney, is a going concern precisely because of this potential to shed light on earth's seemingly fickle thermostat. "Our oceanic records aren't on the same timescale as the current human impacts on the environment, but we do see rapid forcings and responses," she says. "Oceanographers and meteorologists tell us the way things are; as paleoceanogaphers we tell you the range of ways things were--and may be again."

Metals in S.F. Bay sediments may repeatedly contaminate the water Monday, February 12, 3:30 p.m. Speaker: Ignacio Rivera-Duarte (408) 459-2088 or iriverad@cats.ucsc.edu

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 the far southern reaches of 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.

Toxicologist Ignacio Rivera-Duarte, a postdoctoral researcher at UC Santa Cruz, collected water and sediments at several spots in San Francisco Bay during the summer, when water circulates most sluggishly. In southernmost San Francisco Bay, near San Jose, levels of copper and nickel in the water often exceed federal safety guidelines at that time of year.

Rivera-Duarte used painstaking ultraclean methods to determine the concentrations of copper, nickel, cadmium, cobalt, and zinc in the water, as well as in "porewaters" that squeeze among the grains of sediments. The data, among the first reliable measurements of trace metals in porewaters, were accurate to within a part per trillion. Such fine level of detail allowed Rivera-Duarte to paint 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 all of the metals in the water except cadmium, Rivera-Duarte found. He and his colleagues speculate that 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.

Research team leader Russell Flegal, professor of earth sciences at UCSC, says the work corroborates similar studies his group has performed in San Diego Bay, parts of which are similar to San Francisco Bay. However, he emphasizes the need for further research, both at different times of year and at more sites within both bays.

"These studies show that we should take remobilization from sediments into account when we try to understand sources of trace-metal contamination in severely impacted bays," Flegal says. "However, we are not saying that contaminated wastewater is no longer a issue. New inputs from wastewater discharges and surface runoff would only add to the problem."

Some results from the IronEx-II ocean fertilization experiment Thursday, February 15, 11:30 a.m. Speaker: Eden Rue (408/459-2585 or elrue@cats.ucsc.edu) Thursday, February 15, 4 p.m. Speaker: Marta Sanderson (408/459-2682 or mps@cats.ucsc.edu)

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. Encouraging worldwide plant growth with iron supplements, some scientists have suggested, could soak up enough carbon dioxide from the atmosphere via photosynthesis to slow global warming. Many researchers remain dubious about such global engineering, but they were eager to study the fascinating 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, UC Santa Cruz 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. But because biologists had assumed that the tiny plants called phytoplankton could only consume inorganic iron, 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 at UCSC. The hundredfold 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." No one knows yet how the plants get the iron into their cells, but clues gathered by Rue suggest that it enters with the aid of a molecular entourage.

A puzzle of the first iron-seeding experiment, IronEx-I in 1993, was that plants grew less vigorously than expected. One proposed reason is that as the tiny plants gorge themselves on iron, they also crave yet another nutrient: silica and/or zinc. To test the idea, UCSC graduate student Marta Sanderson added different nutrients to pristine seawater. A dose of iron by itself spurred an 18-fold increase in plant growth. But silica and iron together increased growth more than 40-fold.

"When you add iron, you stimulate the growth of diatoms," says Sanderson, "but they also need silica to grow their skeletal shells." Charting the dietary needs of these plants will help scientists clarify marine biogeochemical cycles: the complex paths that iron, silica, carbon, and other elements travel among land, sea, and living organisms.

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