Water Quality and Land Cover in Lake Michigan Drowned River Mouths
Description
PURPOSE: Lake Michigan’s drowned river mouth (DRM) systems are hydrologically unique due to their riverine and large-lake influences that create biologically diverse ecosystems. DRMs serve as focal points for human development and the confluence of watershed impacts, which can have substantial impacts on DRM ecosystems. We hypothesized that greater anthropogenic development in southern DRM watersheds would be reflected in poorer water quality indicators than less developed northern DRM watersheds. SUBJECTS: We sampled 12 DRMs along a latitudinal gradient in eastern Lake Michigan. METHODS: We used standard methods to measure water quality, and we used publicly available data to characterize land cover. ANALYSES: We then used a combination of univariate (simple linear regression and ANOVA) and multivariate (PCA) statistical tests to examine the significance of spatial patterns. RESULTS: We found that watershed human population density and agriculture were strong drivers of chlorophyll-a and TP – indicators of poorer water quality – and that these measures increase in southern DRMs. Within DRMs, we found that TP concentrations were typically greatest near the river mouth and decreased closer to the outflow into Lake Michigan. CONCLUSIONS: Our results suggest that land use drives chlorophyll-a and TP (i.e., indicators of ecosystem productivity) and will be used to better understand the effects of human development on DRMs.
Water Quality and Land Cover in Lake Michigan Drowned River Mouths
PURPOSE: Lake Michigan’s drowned river mouth (DRM) systems are hydrologically unique due to their riverine and large-lake influences that create biologically diverse ecosystems. DRMs serve as focal points for human development and the confluence of watershed impacts, which can have substantial impacts on DRM ecosystems. We hypothesized that greater anthropogenic development in southern DRM watersheds would be reflected in poorer water quality indicators than less developed northern DRM watersheds. SUBJECTS: We sampled 12 DRMs along a latitudinal gradient in eastern Lake Michigan. METHODS: We used standard methods to measure water quality, and we used publicly available data to characterize land cover. ANALYSES: We then used a combination of univariate (simple linear regression and ANOVA) and multivariate (PCA) statistical tests to examine the significance of spatial patterns. RESULTS: We found that watershed human population density and agriculture were strong drivers of chlorophyll-a and TP – indicators of poorer water quality – and that these measures increase in southern DRMs. Within DRMs, we found that TP concentrations were typically greatest near the river mouth and decreased closer to the outflow into Lake Michigan. CONCLUSIONS: Our results suggest that land use drives chlorophyll-a and TP (i.e., indicators of ecosystem productivity) and will be used to better understand the effects of human development on DRMs.