Baltimore Ecosystem Study Institute of Ecosystem Studies

2011 BES Annual Meeting Presentation and Poster Abstracts

Effects of Urbanization on Dissolved Organic Matter Composition in Maine, USA.
Parr, Thomas
Co-Authors: Thomas Parr, Chris Cronan, Tsutomu Ohno, Kevin Simon

Abstract: Humans impact greater than 75% of the earth’s terrestrial surface with more than 50% of the world population living in urban areas. Compared to most other states on the eastern seaboard, Maine has a small urban footprint, but it is growing. Indeed, 77% of Maine’s population growth in the past decade has occurred outside of existing cities in once smaller towns and rural areas leading to urban and suburban expansion. Because streams integrate landscape processes and are readily degraded by anthropogenic stressors, they are an ideal study system for this process. Urbanization strongly modifies the biogeochemistry of streams with potential consequences for ecosystem structure and function. While changes in inorganic nutrient biogeochemistry are reasonably well studied, much less is known about the urban influence on dissolved organic matter (DOM) abundance and composition. We examined the composition and abundance of dissolved organic matter seasonally along a gradient of urbanization, indicated by total impervious cover, across the State of Maine. Samples from 116 1st and 2nd order streams draining catchments containing 0-60% impervious cover were analyzed using fluorescence spectroscopy and parallel factor analysis (PARAFAC) to quantify DOM composition. PARAFAC Components typically associated with upland forests and wetlands decreased with increasing urbanization. One component, occurring in the protein region, increased with impervious cover indicating increased carbon lability. Fluorescence indices also indicated increasing urbanization decreased its humic character and shifted its origin from allochthonous to autochthonous sources. Thus, urbanization changes the composition of DOM available for aquatic biogeochemical processes towards more labile compounds.