It comes as no surprise to hear that the Earth’s climate is changing. But is the climate changing because of people’s activities, natural causes, or a combination of both? And how significant are these changes? Scientists are now studying the shells of tiny one-celled organisms that lived in the ocean thousands of years ago in an attempt to answer these and other questions.

On Tuesday, April 16, from 11:30 a.m. to 1 p.m. at the Hotel du Pont in Wilmington, Katharina Billups, assistant professor of oceanography at the University of Delaware, will present “Ocean History through the Microscope.” The lecture, which includes lunch, will conclude the fourth annual Wilmington Lunch and Lecture Series sponsored by the University of Delaware Graduate College of Marine Studies and the Sea Grant College Program.

Billups quotes Winston Churchill who says, “The farther backward you can look, the farther forward you can see,” as a reason for studying the history of the ocean. “If we study how the ocean has affected the climate when only natural changes were a factor,” says Billups, “then we can look to the past to help unlock the mysteries of how our climate may change from human activity.”

During her talk, Billups will describe how she is able to reconstruct the history of the ocean by conducting chemical analyses on the shells of marine organisms called foraminifera or forams. Although they are still among the most plentiful organisms in the ocean today, there are some areas of the deep sea where the bottom sediments are composed almost exclusively of the shells of forams that lived thousands of years ago. Information about the water in which these organisms lived is recorded in the chemistry of their shells.

Billups will show slides of how deep-sea drilling equipment is used to collect cores, or samples, of sediments from the bottom of the ocean. Once the sediments are cleaned of mud, microscopes are used to select forams of interest. Laboratory analyses are then conducted on these forams to determine the ratio of oxygen-18 and oxygen-16 — two varieties of oxygen atoms called isotopes — in their shells.

The isotope ratio in a shell is primarily dependent on the amount of ice that is present at the poles. Water molecules that are composed of the lighter isotope, oxygen-16, tend to evaporate more easily — leaving behind seawater that is higher in oxygen-18. At the polar ice caps, where these lighter water molecules fall as snow, oxygen-16 gets locked up in the ice.

“During periods of glaciation, the ice caps were larger than they are today,” says Billups. “As a result, ocean water had a higher concentration of oxygen-18, and forams living during these time periods had a correspondingly higher concentration of oxygen-18 in their shells.”

Billups earned her doctorate in Earth sciences from the University of California in Santa Cruz and a bachelor’s and master’s degree in geology from the University of California in Davis. Prior to joining CMS, she completed a postdoctoral fellowship at Harvard University in Cambridge, Massachusetts.

The lecture includes lunch at the award-winning Hotel du Pont. To reserve your seat, at $10 per person, call (302) 831-8062. Or e-mail your reservations to MarineCom@udel.edu.

April 15, 2002