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Urban infrastructure influences dissolved organic matter quality and bacterial metabolism in an urban stream network
Citation:
Arango, C., J. Beaulieu, K. Fritz, B. Hill, C. Elonen, M. Pennino, P. Mayer, S. Kaushal, AND D. Balz. Urban infrastructure influences dissolved organic matter quality and bacterial metabolism in an urban stream network. FRESHWATER BIOLOGY. John Wiley & Sons Inc, Malden, MA, 62(11):1917-1928, (2017).
Impact/Purpose:
Urban streams are often buried beneath urban infrastructure, eliminating light and reducing direct organic matter inputs into streams. These factors can impact water quality in the urban stream and in downstream waters. This research is relevant to researchers, communities, planners and other concerned with the quality of water near urban areas.
Description:
Urban streams are degraded by a suite of factors, including burial beneath urban infrastructure (i.e., roads, parking lots) that eliminates light and reduces direct organic matter inputs to streams, with likely consequences for organic matter metabolism by microbes and carbon limitation in streams. We studied seasonal changes in organic matter metabolism by microbial communities in open and buried reaches of three urban streams in Cincinnati, Ohio. We characterized organic matter quality using fluorescence spectroscopy, extracellular enzyme profiles, and carbon limitation patterns. We hypothesized: 1) that algal production would lead to higher quality dissolved organic matter (DOM) in spring compared to other seasons and in open compared to buried reaches, 2) lower reliance of microbial respiration on recalcitrant carbon sources in spring and in open reaches, and 3) that microbial respiration would be more carbon limited in the autumn and in buried reaches. DOM quality was generally higher in spring than autumn, but the only DOM quality metric that varied by reach was an indicator of recalcitrant humic compounds, which showed more humic DOM in open compared to buried reaches. This likely reflected open reaches as an avenue for direct terrestrial inputs from the riparian zone. Extracellular enzyme assays showed that microbes in buried reaches consistently allocated more effort to degrade recalcitrant carbon sources, consistent with a lack of labile carbon compounds due to limited photosynthesis. Finally, buried and open reaches were both more carbon-limited in autumn when terrestrial leaf inputs dominated compared to the spring when vernal algal blooms were pronounced. Altogether, our data show that stream burial affects the quality of DOM pool with consequences for how microbes use those carbon sources, and that buried and open stream reaches were limited by labile carbon in all seasons. Different carbon quality and use patterns coupled with widespread carbon limitation suggests that these urban streams likely export recalcitrant carbon to downstream water bodies, and that the cycling of nitrogen and/or phosphorus could decrease if heterotrophic metabolism is limited by labile carbon availability.
URLs/Downloads:
http://onlinelibrary.wiley.com/doi/10.1111/fwb.13035/abstract?campaign=woletoc
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