PS 48-228 - Organic Matter Cycling across the Urban Terrestrial-Aquatic Continuum

Abstract: Over 70% of the world’s population is predicted to live in urban areas by the end of the century, yet the impacts of urbanization on ecosystem functions remain ambiguous. This contributes to high uncertainty in the representation of urban carbon (C) cycling within Earth Systems Models (ESMs), which in turn leads to imprecise predictions of the global climate. In particular, ecosystems across the urban terrestrial–aquatic continuum have an outsized impact on global C cycles but are poorly understood. Across the terrestrial–aquatic continuum, urban land uses contribute excess C and nutrients (nitrogen and phosphorous) to soils and waterways, which in turn regulate microbial C cycling. Precipitation heightens these impacts by flushing materials into aquatic ecosystems and, ultimately, into the coastal ocean.

The goal of this research is to identify locations exerting strong impact on C biogeochemistry (i.e., control points) and then understand the interplay of molecular controls, nutrient supply, and hydrologic factors that fuel rapid microbial C processing at these locations. Our hypothesis is that commonalities in microbial functions lead to conserved control points and biogeochemical processes that are distinct to the urban environment and regulate organic matter (OM) decomposition across its terrestrial–aquatic continua. To achieve these outcomes, we will employ top-down (non-target) and bottom-up (targeted towards specific genes) molecular analyses to identify enzymatic pathways of OM decomposition impacted by anthropogenic activities, structured to integrate into microbial-explicit models. This molecular understanding is critical to improving our predictive abilities in novel environmental scenarios, as it drives the relative magnitudes of the various C cycle fluxes at the ecosystem to Earth system scale.

This poster will present the first year of research in this five-year endeavor. We will focus on patterns of spatiotemporal variation in OM concentration and composition across three urban watersheds – Baltimore, MD, Jacksonville, FL, and Duluth-Superior, MN-WI. We will also present preliminary results on the resistance and resilience of these watersheds to extreme hydrologic events (hurricanes, snowmelt, and large precipitation events). Collectively, this work will create a unique knowledge set inclusive of control points, microbial OM decomposition processes, and their relationships to various urban attributes that influence the response of coastal zones to environmental extremes.