Lake ecosystem variation across landscape position and human development gradients in Vilas County, Wisconsin

Vilas County, Wisconsin's human population has greatly increased over the last century. For my dissertation research, I studied the anthropogenic impacts on lake ecosystems in Vilas County and how the response of lakes varies with their position on the landscape. I assessed the spatial variation in aquatic macrophyte community composition along gradients of landscape position and human development. I used multivariate techniques to assess the relationships among the macrophyte communities and to find out which environmental variables best account for the differences between communities. I also examined the changes in macrophyte percent cover versus an index of human development. Macrophyte communities in lakes high in the landscape are dominated by isoetids while lakes low in the landscape are dominated by elodeids due to the difference in bicarbonate concentrations. The presence of the human-introduced crayfish Orconectes rusticus correlates with the absence of macrophytes. An increase in human development correlates with a decrease in macrophyte abundance.; I investigated a technique to examine the temporal variation in zooplankton community size structure over time using surface sediments from 58 lakes that range in both landscape position and human development. We used non-metric multidimensional scaling ordination and simple correlation analyses to assess the capabilities of Bosmina mucro and antennule measurements to describe the zooplankton community size structure. This broad spatial-scale calibration study supports the use of Bosmina mucro and antennule lengths as a proxy for zooplankton community size structure.; We used paleolimnological techniques to examine the changes since European settlement in riparian and upland vegetation, zooplankton communities, organic carbon inputs and water chemistry in four highly developed Vilas County, Wisconsin lakes that vary in landscape position. The four lakes had similarities in their response to shoreline development, but differences in the magnitude of the changes in aquatic chemistry and in the zooplankton community response. The two lakes low in the landscape showed greater change in inferred zooplankton community size structure. Variation in aquatic chemistry and taxa present between lakes of different landscape position prior to European settlement could be an explanation behind the differing lake ecosystem responses to human development.