Poster Presentation Society for Freshwater Science 2026 Annual Meeting

Does Raw Sewage Fuel Food Webs in Urban Streams with Failing Infrastructure? (136125)

Jason Aguirre 1 , Emily Elliott, PhD 1
  1. Geology and Environmental Science, University of Pittsburgh, Pittsburgh, Pennsylvania, USA

Urban waterways link human infrastructure and ecological systems, with direct consequences for water quality, biodiversity, and downstream resource management. As cities expand and infrastructure ages, urban streams increasingly receive excess nutrients like carbon, nitrogen, and phosphorus from wastewater, stormwater runoff, and altered land use. Although urban streams can intercept some nutrient pollution through biological uptake and biogeochemical regulation, chronic nutrient enrichment can destabilize aquatic communities and impair ecosystem functions that regulate additional contaminants. A persistent challenge in urban stream science is understanding how human-derived nutrients move beyond the water column to become incorporated into stream ecosystems, and how land use and infrastructure govern these pathways. This research will examine how urban land use shapes the incorporation of sewage-derived nutrients into stream food webs and influences aquatic community structure. The study will be conducted in eight urban tributaries within the Ohio River Basin in Pittsburgh, Pennsylvania, USA, a region characterized by aging sewer infrastructure, buried headwaters, and highly modified hydrologic regimes. These streams are monitored under an EPA-mandated Consent Decree, providing high-resolution discharge data that will be integrated with biological and chemical measurements. This project will combine field sampling, stable isotope tracers, and watershed-scale geospatial analysis to address two objectives. First, it will quantify the incorporation of sewage-derived nutrients into urban stream food webs using a single, comparable functional feeding group of stream insects (shredders) present across all study sites. Carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes signatures from insect consumers and basal resources will be used to estimate the relative contribution of human versus natural energy sources, while insect abundance and diversity will be measured to assess community-level responses. Second, food web metrics will be evaluated in relation to watershed-scale indicators of the built environment, including impervious surface cover, housing age, hydrologic intensity, and sewer infrastructure density, to determine how urbanization governs the spatial distribution of enriched nutrients across ecosystems. By explicitly linking land use, infrastructure, and biological nutrient incorporation, this research will advance a mechanistic understanding of ecological exposure to urban nutrient pollution. 

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