Date of Graduation

5-2025

Document Type

Thesis

Degree Name

Master of Science in Crop, Soil & Environmental Sciences (MS)

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor/Mentor

Speir, Shannon

Committee Member

Wood, Lisa S.

Second Committee Member

Evans-White, Michelle A.

Third Committee Member

Daniels, Michael B.

Keywords

decomposition; nutrients; road salts; Urbanization; Water quality

Abstract

Urban stream syndrome (USS) refers to the common symptoms of degradation in urban streams globally. Two symptoms of USS are increased nutrient and salt concentrations in streams, affecting ecosystem structure and function. Excess nutrients negatively impact freshwater ecosystems, placing downstream habitats at risk of eutrophication and harmful algal blooms. Excess salt runoff, derived from road salt application, is toxic to freshwater organisms and affects leaf litter decomposition, the base of aquatic food webs. Here, I aimed to quantify the effects of nutrient pollution and salinization on urban water quality and ecosystem function. Despite the widespread consequences of nutrient pollution, most research compares urban systems to pristine watersheds or focuses solely on nutrient concentrations in a single stream. This limits our understanding of how nutrient export varies spatially and temporally within a broader urban area. I quantified nutrient loads at a high spatiotemporal resolution in Fayetteville, Arkansas to determine the controls on nutrient export across the urban landscape. I collected biweekly nutrient samples (nitrate [N], soluble reactive phosphorus [P]) and streamflow at 20 sites, as well as five stormflow events at a subset of sites. Both N and P loads had a positive relationship (N: p<0.0001, P: p<0.0001) with subwatershed impervious cover and a negative relationship with subwatershed canopy cover (N: p<0.001, P: p<0.05). In contrast, riparian landscape characteristics were only seasonally important (e.g., canopy cover had a positive relationship with SRP in the spring). The effect of landscape characteristics on nutrient loads also varied across storm events. I also documented low spatial stability in nutrient loads, likely due to heterogeneity in land cover. Our research suggests urban water quality must be managed at the watershed scale to account for both the spatial heterogeneity of urban areas and seasonal variation in nutrient dynamics to effectively protect water quality. I also examined how traditional road salts and ‘eco-friendly’ alternatives (e.g., beet-brine) affect leaf litter decomposition, a key ecosystem function, using replicated recirculating stream mesocosms. I quantified microbial respiration of leaf biofilms, microbial conditioning (as leaf toughness), and decomposition (as mass loss) over a two-week period for a labile (sugar maple; Acer saccharum) and recalcitrant (post oak; Quercus stellata) leaf species under five deicer treatments: control, low-beet, high-beet, low-salt, and high-salt. I observed decreased decomposition rates for labile leaves in the high-beet treatment during first seven days of the experiment (high-beet-brine k = .007 d-1, control k = .022 d-1) treatment, most likely resulting from the addition of beet-based carbon. I saw microbial conditioning (an early indicator of decomposition) of recalcitrant leaves was increased by each of the deicing treatments, likely due to added Cl-. Overall, beet-brine had a larger effect on leaf litter decomposition than the paired treatment of traditional road salts. Further research is needed prior to the widespread implementation of beet-brine as an ‘eco-friendly’ alternative to traditional road salts. My thesis highlights the complex spatiotemporal dynamics of nutrient loss in urban streams and emphasizes that both traditional and eco-friendly management solutions require careful evaluation to support urban freshwater ecosystem function.

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Available for download on Wednesday, June 17, 2026

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