This action funds an NSF Minority Postdoctoral Research Fellowship for FY 2010. The fellowship supports a research and training plan in a host laboratory for the Fellow who also presents a plan to broaden participation in biology. The title of the research and training plan for this fellowship to Kristine Kaiser is "Effects of man-made noise on stress physiology, immunology and reproductive biology in frogs." The host institution for this research is University of California-Riverside, and the sponsoring scientists are Drs. Wendy Saltzman and Emma Wilson.
Noise is a natural component of an ecosystem, but for a species which tries to attract mates acoustically, it can be problematic. Most species have adaptations to allow for communication to occur despite naturally-occurring noise. However, habitat alteration has become pervasive; such change often introduces human-made, or anthropogenic, noise such as traffic noise into the environment. Anthropogenic noise differs from natural noise in many structural features, and how it affects acoustically communicating animals is not well known; yet an animal's ability to cope with this problem can affect its likelihood of survival in a rapidly changing landscape. Although recent work has shown behavioral compensation to noise in frogs, the effects of noise on fitness and physiology are not well studied. The three major goals of the project are to determine if anthropogenic noise (1) increases the stress response in frogs; (2) decreases frog immunocompetence; and (3) decreases frog fitness or impacts reproductive physiology.
Training objectives of this project include integrative biological research in the fields of endocrinology, immunology, and reproductive physiology. This research provides valuable insight into amphibian physiology and a possible mechanism of amphibian population dynamics. In addition, the postdoctoral Fellow will serve as a mentor to a diverse group of undergraduate researchers in all aspects of the project.
Intellectual Merit: Chronic noise exposure has a variety of negative effects on vertebrates, including behavioral shifts, fatigue, physiological effects (e.g., hypertension and heart disease), and psychological disturbances (e.g., migraine, irritability). However, although a growing body of literature demonstrates a wide range of behavioral responses to noise among frogs, the physiological effects of noise exposure are poorly understood in amphibians, the most threatened vertebrate taxon. I found that exposure to traffic noise at ecologically relevant levels increased the level of corticosterone (CORT), a hormone associated with the stress response, in the plasma, suggesting that frogs reacted to even long-term noise as a stressor. I also found that at the end of one week of exposure to noise, frogs had significantly decreased sperm counts and sperm viability relative to control frogs, but I found no effect on the ratios of circulating white blood cells:red blood cells, a measure of immune function. I conducted another experiment to understand the mechanism by which reproductive suppression occurred. Previous studies in other species suggest that CORT may mediate complex interactions with various physiological systems, so I experimentally elevated frogs' plasma CORT levels for a week. I found no decrease in these frogs' sperm counts or sperm viability relative to controls, but did find a slight decrease in eosinophils, a white blood cell associated with fighting extracellular parasites. I suggest that traffic noise, although largely pervasive, is but one chronic stressor animals face in an increasingly human-altered landscape. Thus, this study is one step forward in understanding species' responses to urbanization and providing a framework for such studies. The rapidly changing landscape many individuals face as a result of habitat change may include a variety of potentially novel stressors, making it harder for animals to acclimate to environmental disturbances. Studies incorporating multiple chronic environmental stressors would be valuable. Broader Impacts: Over the course of this study, eleven undergraduate students participated in research under my direction; many led their own research projects within the lab, including development and validation of all of the protocols we used. Seven of these were women and five were under-represented minorities. Impressively, all have remained in science or professional school or are applying to do so. In addition, two of these students were awarded competitive internal grants to supplement their independent projects. Several of these students have presented their research findings at regional conferences and have co-authored posters, presentations, invited talks, and two manuscripts (one published, one in review) on this research. I published a public-interest piece on frogs and traffic noise in the magazine Froglog in 2011, and hope to publish another in a future general-interest issue. I also worked with a public high school teacher in Los Angeles to disseminate portions of this research (aligned with California State Science Standards) in her classroom as well as present options for careers in biology. Due to the implementation of the Next Generation Science Standards, the lessons are being revised to align with standards now in place and will be submitted to a public forum at a later date after being classroom tested.
