Amphibian Decline:UVB & Ground Pollutants
by Mika Pringle Tolson
UC TSR&TP Trainee Lara Hansen
Photo courtesy of Lara Hansen
Lara Hansen is one of those rare individuals who has always known what she wanted to do with her life. "When I was 7 my dad read me an article out of what was probably Science magazine about ozone depletion. There was a cool picture on the front and when I asked him what it was about, he explained it to me. I have been fascinated by ozone depletion and enhancement of UVB ever since." Hansen's senior thesis project as an undergraduate in biology at UC Santa Cruz involved looking at how UVB exposures affected growth and survival of the marine bacterium, Pseudomonas perfectomarinus. She is currently pursuing a doctoral degree in ecology at UC Davis. With her TSR&TP graduate student fellowship, Lara Hansen is taking a toxicological approach to studying the impact of environmental stresses on amphibian species decline in Western North America. Previous research has implicated UVB exposure and environmental toxicants as possible causes, but these have not been positively identified and exposures have never been quantified. Through immunocompetency assays and field and lab trials, Hansen hopes to identify sublethal exposures of environmental stresses on populations of the Pacitic tree frog, Hyla regilla. She chose the Pacific Tree Frog because it has the broadest ecological tolerance and range (British Columbia to Baja California). This broad range allows her to examine virtually all environmental stresses that are suspected contributors to the species' decline. Hansen is sampling native populations of H. regilla and transplanting eggs in three transects in California with low and high altitude sites (the central coast range and the southern and northern Sierra Nevada) to determine variability and sensitivity among populations. She wants to know if "high elevation populations are better able to deal with high levels of UVB than populations at lower elevations." UVB exposure is known to suppress immune systems, and as Hansen explains, "Amphibians are a great system to study the effects of environmental stress on immune system function because they have really vascular skin. They're wide open for immune suppression because their blood and their immune system is right there at the surface where it can get a really big dose." Hansen anticipates completing her doctorate in the spring or summer of 1998 and continuing her research on the effects of UVB with a non-profit environmental group or government agency. She hopes to "focus her scientific findings toward actually solving problems and explaining science to policy makers to assist in creating more relevant policies."
Adult Pacific Tree Frog, Hyla regilla
(Photo courtesy of L. Hanson)
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