Fellow Examines Effects of Endocrine Disrupting Compounds on Fish
Susanne Brander initially thought her future would be a career in business-she graduated with a bachelor’s degree in business administration in 1999. But that all changed when an internship with The Nature Conservancy sparked her interest in biology. Then, fieldwork with sea turtle conservation groups in Greece, Thailand and the U.S. Virgin Islands solidified her decision to pursue post-graduate studies in biology, instead.
Now she’s a Delta Science Program Fellow whose graduate research, through the Department of Environmental Toxicology at the University of California, Davis, at the Bodega Marine Lab focuses on the effects of endocrine disrupting compounds (EDCs) on fish reproduction and health. This research will contribute to a better understanding of the impacts of these chemicals on fish in the Bay-Delta and elsewhere. The Delta Science Fellows program funds postdoctoral and graduate researchers to work with community and scientific mentors on targeted Delta research priorities.
The endocrine system is a complex system of glands in the body that produce hormones-like the pituitary gland, ovaries, etc. Disrupting this system can lead to many adverse effects in animals. According to the Environmental Protection Agency, endocrine disruptors “interfere with the synthesis, secretion, transport, binding, action, or elimination of natural hormones in the body that are responsible for the maintenance of homeostasis (normal cell metabolism), reproduction, development, and/or behavior.” The main reproductive hormones in females and males are estrogens and androgens, respectively.
Brander’s research goals are:
To evaluate a potential model species that can be used to study and assess endocrine disruption in the estuary and serve as a surrogate for threatened species exposed to EDCs.
To evaluate changes influenced by contaminants that act as estrogens and/or androgens at the field site, molecular, organism, and population levels in a model estuarine system (San Francisco [SF] Bay Estuary - Suisun Marsh).
To examine the potential for estrogenic activity of pyrethroid pesticides, which are now a common pollutant in the SF Bay Estuary.
To address those objectives she used the Mississippi silverside (Menidia audens) as a model species-a small non-native fish ubiquitous in the SF Bay Estuary and Sacramento/San Joaquin Delta. “It is an ideal choice for use as a model or surrogate species to study the impact of EDCs, because it has been shown in other studies to be sensitive to contaminants, including EDCs,” Brander said. “It also has a small home range, which means that fish caught at a specific site have been exposed only to the contaminants at that site, so responses can be linked to a small area.”
Since many sites in the SF Bay Estuary have numerous contaminants, it’s difficult to identify which individual compounds are the most harmful, she said. “For many of these EDCs, effects of individual chemicals have been determined in the laboratory. Instead of looking at the impact of individual EDCs, my field work sought to look at the overall impact of the complex mixture.” To do this she and her fellow researchers used genetically engineered cells that respond to chemicals which act as estrogens or androgens. This cell line also contains a gene that causes a firefly to glow. Therefore, if there are hormones in the water, these special cells light up.
For her field research, Brander took water samples from two locations within Suisun Marsh-Suisun Slough (urban runoff) and Denverton Slough (ranch runoff). At the site receiving urban runoff and treated wastewater effluent she and her research team found both estrogenic and androgenic compounds in the water. At the site receiving ranch runoff, they only found estrogenic activity in the water.
At the ranch runoff site where they detected just estrogens in the water, the sex ratio seemed to be normal (50:50) but male fish showed elevated gene expression of choriogenin and vitellogenin, two female reproductive genes. However, at the urban runoff site where both male and female hormones were detected, the sex ratio was skewed towards having too many male fish, evidence that fish at the urban site are being masculinized, she explained, possibly due to EDCs that act as androgens (male hormones) in the water.
Brander has been collaborating with an ecologist who does mathematical modeling of fish populations. “A preliminary model we put together examines the impact of masculinization and shows that it may contribute to population decline,” she said. “Our hope is to be able to extrapolate this to endangered species that cannot be sampled from the wild, such as the delta smelt.”
“Endocrine disrupting compounds are stressors currently having measurable effects in Suisun Marsh,” said Delta Science Program Lead Scientist Cliff Dahm. “The importance of these compounds relative to other stressors is the bigger picture that needs to be addressed.”
Brander earned her master’s in environmental science and policy at Johns Hopkins University in 2004. She is now in Wilmington, North Carolina, where her husband, Will White, is an ecologist in the Department of Biology and Marine Biology at the University of North Carolina. She is currently finishing up her dissertation and once she receives her Ph.D. from UC Davis, Brander will be adjunct faculty at UNC Wilmington. In her spare time, she enjoys doing yoga and making pottery; however, with a four-month-old daughter, spare time is in short supply these days.