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August 23, 2004

Two UCSC graduate students receive grant for marine ecology research

By Tim Stephens

Two UC Santa Cruz graduate students are among the winners of the 2004 Mia J. Tegner Memorial Research Grants in Marine Environmental History and Historical Marine Ecology. Seth Newsome, a Ph.D. candidate in Earth sciences, and Daniel Monson, a Ph.D. candidate in ecology and evolutionary biology, will use their $5,500 grant to investigate historical changes in the diets of killer whales during the past century.

UCSC researchers will investigate possible changes in the diets of killer whales over the past 100 years. Photo: Graeme Ellis

The Tegner grants are awarded specifically to help scientists document the state of marine populations and ecosystems prior to large-scale human impacts such as industrial fishing, whaling, and pollution. The 11 grants made this year were chosen from among 86 proposals from scientists in 16 countries. The grants were announced last month by the Marine Conservation Biology Institute of Redmond, Washington.

Newsome and Monson are teaming up to investigate a controversial hypothesis regarding the ongoing collapse of marine mammal populations in the Bering Sea and Gulf of Alaska. Over the past few decades, populations of pinnipeds (seals and sea lions) and sea otters in this region have declined dramatically, but the ultimate cause of the declines remains unclear. The "killer whale predation hypothesis" holds that the depletion of whale populations by industrial whaling forced killer whales to change their diets, relying less on baleen whales as a food source and eating more pinnipeds and sea otters instead.

The hypothesis is supported by indirect and circumstantial evidence, but Newsome and Monson hope to find stronger evidence for a shift in killer whale diets by analyzing the isotope composition of killer whale teeth. Isotope analysis of an animal's tissues can yield clues to its past diet because of natural variability in the abundance of rare isotopes of elements such as carbon and nitrogen. The teeth of killer whales are built up in layers deposited over an animal's lifetime, and the isotope composition of each growth layer should reflect the animal's diet at the time it was deposited.

Newsome and Monson have worked with colleagues at the National Marine Mammal Lab to obtain about 100 killer whale tooth specimens from museum collections. They have grouped the specimens to represent three relevant time periods: 1900 to 1950, 1950 to 1970, and 1970 to 2003. They plan to section teeth and analyze individual growth rings using a mass spectrometer in the Stable Isotope Laboratory at UCSC.

Newsome has also been investigating the role that changes in productivity may be playing in the decline of the Bering Sea ecosystem. In addition, he has been working with Paul Koch, professor of Earth sciences, and Diane Gifford-Gonzalez, professor of anthropology, to study historical changes in populations of northern fur seals along the California coast over the past 5,000 years, using isotope analysis of remains left at middens by native people.

Monson earned his M.S. in marine sciences at UCSC in 1995, studying sea otter populations with James Estes, adjunct professor of ecology and evolutionary biology. He has been a research wildlife biologist at the U.S. Geological Survey's Alaska Science Center since 1996 and has returned to UCSC to pursue his Ph.D., with professor of ecology and evolutionary biology Terrie Williams as his adviser. He has extensive experience as a field biologist studying a variety of marine mammals in Alaska and California.

The Tegner grants honor the memory of Mia J. Tegner, a marine biologist at Scripps Institution of Oceanography who lost her life in 2001 while carrying out research off southern California. She studied the ecology of kelp forest communities and abalone populations and was particularly interested in understanding how marine populations and ecosystems have changed as a result of human activities. This pioneering research earned her appointments as a Pew Fellow in Marine Conservation and as a Fellow of the American Association for the Advancement of Science. The Mia J. Tegner Memorial Research Grants were started by the Marine Conservation Biology Institute with funding from the Oak Foundation, the Christensen Fund, and the Weinstein Family Foundation.

The Marine Conservation Biology Institute is a nonprofit science organization dedicated to advancing the science of marine conservation biology and promoting cooperation essential to protecting, restoring, and sustainably using the living sea.

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