The effects of land use change on littoral zone dynamics of Lake Tanganyika, East Africa
AuthorO'Reilly, Catherine Marie
AdvisorCohen, Andrew S.
MetadataShow full item record
PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractLake Tanganyika, East Africa, is one of the world's unique freshwater ecosystems. This lake is approximately 10 million years old and contains an extremely diverse fauna with high levels of endemicity. Most of the biodiversity in the lake is concentrated along the rocky shoreline, and this dissertation focused on the land-water interactions that may affect the littoral ecosystem as human population densities increase. First, the potential of carbon and nitrogen stable isotopes as indicators of human impact was examined. Sedimentary organic matter from four river deltas with contrasting patterns of land use was used to develop a predictive relationship between terrestrial patterns and geochemical signals. Stable isotope analyses of cores taken at two disturbed and two undisturbed watersheds were consistent with patterns seen in surface sediments. These results suggest that nitrogen isotopes are a better indicator of land use while carbon isotopes are useful in determining changes in vegetation patterns. To evaluate the effect of deforestation on ecosystem dynamics, epilithic metabolism was measured at several sites over a period of one year. Epilithic net productivity did not differ significantly between the disturbed and undisturbed watersheds, but epilithic respiration and algal biomass were significantly higher at the disturbed site. Further evidence of disturbance was given by greater amounts of inorganic material on the rocks and lower ambient oxygen concentrations at the impacted site. Finally, in order to identify species more susceptible to changes in benthic productivity, the food web structure of the pelagic and littoral food webs was elucidated using stable isotopic analyses. Diet specificity is not apparent in the littoral food web, suggesting that broad dietary preferences may help stabilize this persistent food web during environmental perturbations. The isotopic structure of the pelagic food web suggests that upwelling of deeper waters is an important nutrient source for the food web, which is consistent with current nutrient and hydrodynamic models.
Degree ProgramGraduate College