A Spatial and Multivariate Approach to Examining Effects of Urbanization on Nitrogen Sources, Organic Matter Inputs, and Trophic Structure in Streams of Cobb and Paulding Counties, Georgia.

Author

Katharine HorningFollow

Date of Award

Fall 11-19-2020

Degree Type

Thesis

Degree Name

Master of Science in Integrative Biology (MSIB)

Department

Biology

Committee Chair/First Advisor

William Ensign

Major Professor

Troy Mutchler

Second Committee Member

Allen Roberts

Abstract

Urbanization and land use changes have a negative effect on streams often causing numerous physical changes in stream morphology, a change in nutrient concentrations, and altered ecosystems contributing to a loss of habitat, decreased biodiversity, and loss of stability for ecosystem function (Walsh et al., 2005; Meyer et al., 2005; Cardinale and Palmer, 2012). The use of stable isotope analysis for monitoring could be valuable because it accounts for temporal integration from anthropogenic wastewater inputs, characterized by a shift in the abundance of ¹⁵N. This project had three main objectives: (1) to examine how nitrogen and carbon sources are altered with the use of spatial trends of δ¹⁵N values in streams with varying levels of urbanization; (2) to examine how the effects of urbanization, altered nitrogen and organic matter inputs play a role in trophic structure within aquatic ecosystems by examining isotopic food webs; and (3) to see if these variables could be utilized for spatial predictability of urban impacts on streams. We found support for the notion that high levels of developed land use and agricultural land use correspond with an increase in the ẟ¹⁵N values of macroinvertebrates. Our food webs and ẟ¹⁵N values suggested that certain organisms changed their role in the food web consistent with a shift in the food web towards omnivory. Use of impervious surface area, land cover land use and ẟ¹⁵N to monitor water quality could provide an early indicator for stream degradation.