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Carbon limitation patterns in buried and open urban streams
Citation:
Arango, C., J. Beaulieu, K. Fritz, B. Hill, C. Elonen, M. Pennino, P. Mayer, S. Kaushal, AND A. Balz. Carbon limitation patterns in buried and open urban streams. To be Presented at Society for Freshwater Science annual conference, Milwaukee, WI, May 17 - 21, 2015.
Impact/Purpose:
To inform the public
Description:
Urban streams alternate between darkened buried segments dominated by heterotrophic processes and lighted open segments dominated by autotrophic processes. We hypothesized that labile carbon leaking from autotrophic cells would reduce heterotrophic carbon limitation in open channels, whereas the lack of carbon fixation in buried channels would reduce labile carbon production and exacerbate heterotrophic carbon limitation. To test this hypothesis, we deployed nutrient diffusing substrata (NDS) with increasingly labile forms of carbon (cellobiose, arabinose, glucose) and a control into paired open and buried reaches in three streams seasonally. Expressed on an areal basis, heterotrophic respiration on the carbon-amended NDS was higher than the control in all reaches (2-way ANOVA, p<0.001), but there was no carbon lability effect. Therefore, heterotrophic respiration was carbon limited in all reaches, despite the presumed availability of labile carbon from autotrophic processes in open reaches. However, heterotrophic respiration expressed on a biomass basis did not differ among carbon types or between stream reaches. Thus, heterotrophic biofilms in open and buried reaches were carbon limited and accrued biomass in response to the addition of even relatively recalcitrant carbon.
