Masters Theses

Date of Award

8-2007

Degree Type

Thesis

Degree Name

Master of Science

Major

Wildlife and Fisheries Science

Major Professor

Matthew J. Gray

Committee Members

Debra L. Miller, Lisa L. Muller, J. Larry Wilson

Abstract

There is considerable evidence that amphibians are declining globally due to various anthropogenic stressors. Cattle grazing in wetlands is a stressor that may have negative impacts on amphibians and has not been investigated intensively. Cattle could have a negative effect on larval amphibians by decreasing water quality through deposition of nitrogenous waste. Reduction in water quality also may compromise immune function by inducing stress thus making larvae more susceptible to pathogens. My objective was to quantify differences in amphibian larvae community metrics, water quality, and pathogen prevalence between cattle-access and non-access wetlands. I also measured fish abundance and biomass of filamentous algae and detritus, because these variables are known to influence larval amphibian populations, and may be affected by cattle. My study was conducted at the University of Tennessee Plateau Research and Education Center on the Cumberland Plateau, Tennessee. I sampled amphibian larvae and fish 2X per week, water quality 2X per month, and algal and detrital biomass 1X per month at each wetland from March – August 2005 and 2006. I also opportunistically collected American bullfrog (Rana catesbeiana) and green frog (R. clamitans) tadpoles from cattle-access and non-access wetlands during three seasons (winter, summer, and autumn), tested them for pathogens, and noted histopathological changes. In general, relative abundance, species richness, and species diversity of amphibian larvae were greater in non-access wetlands. Mean relative abundance of green frog and American bullfrog (and all other ranid tadpoles) was greater in non-access wetlands. Dissolved oxygen was lower, while specific conductivity and turbidity were higher in cattle-access wetlands. Detrital and algal biomass was lower and greater in cattle-access wetlands in compared to non-access wetlands, respectively. Some changes were noted in aquatic invertebrate and fish abundance between land uses. Tadpoles also were infected by a variety of known amphibian pathogens (e.g., Frog virus 3, Aeromonas hydrophila), but land-use trends often were dependent on species and season. My results suggest cattle negatively impact water quality, detritus, and relative abundance of some larval amphibian species. Fencing cattle from wetlands may be a prudent amphibian conservation strategy.

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