Nitrogen (N) uptake in streams is an important ecosystem service that reduces nutrient loading to downstream ecosystems. Here we synthesize studies that investigated the effects of urban stream burial on N-uptake in two metropolitan areas and use simulation modeling to scale our measurements to the broader watershed scale. We report that nitrate travels on average 18 times farther downstream in buried than in open streams before being removed from the water column, indicating that burial substantially reduces N uptake in streams. Simulation modeling suggests that as burial expands throughout a river network, N uptake rates increase in the remaining open reaches which somewhat offsets reduced N uptake in buried reaches. This is particularly true at low levels of stream burial. At higher levels of stream burial, however, open reaches become rare and cumulative N uptake across all open reaches in the watershed rapidly declines. As a result, watershed-scale N export increases slowly at low levels of stream burial, after which increases in export become more pronounced. Stream burial in the lower, more urbanized portions of the watershed had a greater effect on N export than an equivalent amount of stream burial in the upper watershed. We suggest that stream daylighting (i.e., uncovering buried streams) can increase watershed-scale N retention. This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.
|Original language||English (US)|
|State||Published - Jul 17 2015|
Bibliographical noteFunding Information:
Data used to generate figures and tables in this manuscript are available as Supporting Information. We appreciate constructive input from two anonymous journal reviewers. We thank Kevin Danaher, Elizabeth Hagenbach, Kevin Magerr, Evan Smith, and Benjamin Wu for field assistance. Additional field and laboratory support was provided by Pegasus Technical Services under contract #EP-C-11-006 and by Dynamac Corporation under contract #EP-D-11-073. We thank numerous private land owners for site access and the Cincinnati Metropolitan Sewer District for their assistance with site selection. The U.S. Environmental Protection Agency, through its Office of Research and Development collaborated in the research described herein. It has been subjected to the Agency’s administrative review and has been approved for external publication. Any opinions expressed in this paper are those of the authors and do not necessarily reflect the views of the Agency, therefore, no official endorsement should be inferred. Any mention of trade names or commercial products does not constitute endorsement or recommendation for use.