Date Approved

8-24-2021

Graduate Degree Type

Thesis

Degree Name

Biology (M.S.)

Degree Program

Annis Water Resources Institute

First Advisor

Carl Ruetz

Second Advisor

Alan Steinman

Third Advisor

Sean Woznicki

Academic Year

2020/2021

Abstract

Lake Michigan’s drowned river mouths (DRM) are hydrologically unique systems with riverine and large-lake influences that create biologically diverse ecosystems. Serving as focal points for human development due to the ecosystem services they provide, DRMs have experienced a history of industrialization, urbanization, and are now moving towards an era of rehabilitation. Today, DRM shorelines have been hardened, their riparian zones have been severely altered, and their watersheds exist on a latitudinal gradient of less to greater anthropogenic stress (agriculture and development). The main goal of this study was to understand the current ecological state of DRMs related to anthropogenic development across multiple spatial scales. I hypothesized (1) that there is a latitudinal gradient in indicators of water quality in DRM lakes of eastern Lake Michigan, which is the result of natural land cover and anthropogenic land use, and (2) that natural shorelines support more fish species less tolerant to environmental degradation than residential and hardened shorelines in DRM lakes. To assess the impacts of development on DRM fish communities, I sampled the littoral fish community of 6 DRMs at shorelines hardened with riprap or seawall, residential shorelines with lawns and homes, and natural shorelines with intact riparian vegetation. Within DRMs, I did not find that shoreline structure was a significant driver of fish assemblages. However, I found a general gradient in DRMs from north to south with more fish species tolerant to degraded conditions in southern DRMs, corresponding to watersheds with more development and agriculture in southern DRMs than those with more forested land cover in northern DRMs. I also sampled 12 DRMs for water quality and found that chlorophyll-a and total phosphorus (TP) concentrations increase in southern DRMs, which corresponds to increased agriculture and development. My research suggests that the impacts of land use at the watershed scale were a strong driver of fish assemblages and water quality among the DRMs in eastern Lake Michigan, which will be useful to managers and researchers concerned with coastal habitats in Lake Michigan.

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